Figure 5.5 presents a scatter plot of the window sill dust lead loadings against the floor dust lead loadings. Each point in Figure 5.5 represents the floor and window dust lead loadings from the same room in the same housing unit. The figure shows evidence of a moderate positive correlation between the dust lead loadings on these two neighboring surfaces. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 5 9 October 31, 2002 Table 5.4 Distribution of Dust Lead Loading by Room and Surfaces Dust Lead Kitchens Living Rooms Bedrooms Other Rooms Loading ( µ g/ sq ft) a Number of Rooms ( 000) b Percent of Rooms (%) c Number of Rooms ( 000) Percent of Rooms (%) Number of Rooms ( 000) Percent of Rooms (%) Number of Rooms ( 000) Percent of Rooms (%) Floorsd LT LODe 63,244 66% 98,433 78% 170,153 78% 231,924 73% GE LOD 31,633 33% 26,732 21% 45,915 21% 84,438 27% GE 5 14,062 15% 9,863 8% 19,340 9% 34,291 11% GE 10 5,568 6% 4,287 3% 10,612 5% 18,933 6% GE 20 2,571 3% 1,824 1% 4,175 2% 10,626 3% GE 40 712 1% 880 1% 1,593 1% 7,477 2% GE 100 335 0% 170 0% 1,354 1% 785 0% Missingf 488 1% 1,737 1% 1,002 1% 2,594 1% Total Rooms 95,365 100% 126,902 100% 217,069 100% 318,956 100% Window Sills LT LOD 23,001 24% 29,378 23% 38,394 18% 44,841 14% GE LOD 50,393 53% 72,154 57% 140,748 65% 141,008 44% GE 125 7,037 7% 10,937 9% 20,393 9% 23,472 7% GE 250 4,329 5% 6,731 5% 11,075 5% 17,156 5% GE 500 2,455 3% 4,386 4% 6,661 3% 10,096 3% Missing 3,870 4% 5,462 4% 17,993 8% 16,321 5% No Sills 18,102 19% 19,907 16% 19,934 9% 116,785 37% Total Rooms 95,365 100% 126,902 100% 217,069 100% 318,956 100% Window Troughs LT LOD 3,293 4% 4,125 3% 5,211 2% 6,657 2% GE LOD 49,962 52% 64,827 51% 122,752 57% 119,236 37% GE 800 9,249 10% 12,795 10% 23,268 11% 21,487 7% Missing 16,542 17% 27,537 22% 57,738 27% 58,044 18% No Trough 25,568 27% 30,413 24% 31,368 15% 135,019 42% Total Rooms 95,365 100% 126,902 100% 217,069 100% 318,956 100%

a In this table, maximum loading is not applicable as only one dust sample was collected from each surface in each room. v " Housing units" include permanently occupied, noninstitutional housing units in which children are permitted to live. c All percentages are calculated with total rooms of that type as the denominator. d Floors include both carpeted and uncarpeted floors. e LT equals " less than." GE equals " greater than or equal to." LOD equals " limit of detection." f Missing means that the floor, sill, or trough was present, but that no lead value is available ( either the sample was not collected, e. g., due to inaccessibility or respondent refusal, or the laboratory did not submit a value). National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 5 10 October 31, 2002 Figure 5.5 Association Between Dust Lead Loading on Floors and Window Sills Tables 5.5a through 5.5c present the distributions of floor, window sill, and window trough dust lead loadings, respectively, by selected thresholds and by year of construction. It is evident that older homes have considerably more dust lead than newer homes. The percentage of homes over the HUD Rule standard of 40 µ g/ ft2 for floor dust ( Table 5.5a) increases from less than 1 percent for post 1977 homes to 16 percent 0.01 0.1 1 10 100 1000 10000 100000 0.1 1 10 100 1000 10000 100000 Floor Lead Loading ( µ g/ sq ft) Window Sill Lead Loading ( µ g/ sq ft) National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 5 11 October 31, 2002 for pre 1940 homes. The percentage of homes over the sill dust standard ( Table 5.5b) steadily increases from 4 percent for post 1977 homes to 14 percent for 1940 1959 homes to 40 percent for pre 1940 homes.

Table 5.5a Maximum Floor Dust Lead Loading by Year of Construction Maximum Floor Dust Year of Construction Lead Loading( µ g/ sq ft) a 1978 1998 1960 1977 1940 1959 Before 1940 Number ( 000) Percent (%) b Number ( 000) Percent (%) Number ( 000) Percent (%) Number ( 000) Percent (%) LT LODc Number HUsd 17,487 59% 13,006 47% 5,667 28% 2,208 13% Lower 95% CIe 15,646 53% 10,272 38% 4,076 20% 782 4% Upper 95% CI 19,329 65% 15,740 56% 7,257 35% 3,635 21%

GE LOD Number HUs 12,241 41% 14,868 53% 14,820 72% 15,268 87% Lower 95% CI 10,419 35% 12,454 44% 12,770 65% 13,008 79% Upper 95% CI 14,064 47% 17,281 62% 16,869 80% 17,527 96%

GE 5 Number HUs 3,233 11% 4,968 18% 8,753 43% 11,245 64% Lower 95% CI 2,285 8% 3,567 13% 7,060 35% 9,635 55% Upper 95% CI 4,181 14% 6,370 23% 10,446 50% 12,855 73%

GE 10 Number HUs 1,153 4% 2,488 9% 4,938 24% 7,386 42% Lower 95% CI 370 1% 1,607 6% 3,447 17% 5,802 33% Upper 95% CI 1,935 7% 3,369 12% 6,428 31% 8,970 52%

GE 20 Number HUs 97 0% 1,112 4% 2,784 14% 4,996 29% Lower 95% CI 0 0% 516 2% 1,283 6% 3,759 22% Upper 95% CI 267 1% 1,708 6% 4,286 21% 6,234 35%

GE 40 Number HUs 97 0% 588 2% 1,967 10% 2,843 16% Lower 95% CI 0 0% 216 1% 718 4% 1,989 11% Upper 95% CI 267 1% 961 4% 3,215 16% 3,698 21%

GE 100 Number HUs 97 0% 280 1% 935 5% 1,114 6% Lower 95% CI 0 0% 0 0% 121 1% 587 3% Upper 95% CI 267 1% 640 2% 1,750 9% 1,642 9%

Missing Number HUs 0 0% 0 0% 77 0% 0 0%

a Floors include both carpeted and uncarpeted floors. b All percentages are calculated with total housing units ( 95,688) as the denominator.

c LT equals " less than." GE equals " greater than or equal to." LOD equals " limit of detection." d " Housing units" include permanently occupied, noninstitutional housing units in which children are permitted to live. e CI = 95% confidence interval for the estimated number or percent. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 5 12 October 31, 2002 Table 5.5b Maximum Window Sill Dust Lead Loading by Year of Construction Maximum Floor Dust Year of Construction Lead Loading( µ g/ sq ft) a 1978 1998 1960 1977 1940 1959 Before 1940 Number ( 000) Percent (%) b Number ( 000) Percent (%) Number ( 000) Percent (%) Number ( 000) Percent (%) LT LODc Number HUsd 6,196 21% 1,924 7% 1,074 5% 408 2% Lower 95% CIe 4,270 14% 826 3% 277 1% 0 0% Upper 95% CI 8,122 27% 3,021 11% 1,871 9% 835 5%

GE LOD Number HUs 21,823 73% 24,729 89% 18,779 91% 16,803 96% Lower 95% CI 19,833 68% 22,996 84% 16,956 87% 15,103 93% Upper 95% CI 23,814 79% 26,462 94% 20,602 96% 18,503 99%

GE 125 Number HUs 1,806 6% 4,097 15% 5,407 26% 9,028 52% Lower 95% CI 578 2% 2,444 9% 3,954 19% 7,196 42% Upper 95% CI 3,033 10% 5,749 21% 6,860 33% 10,861 61%

GE 250 Number HUs 1,029 4% 1,755 6% 3,712 18% 6,943 40% Lower 95% CI 139 1% 1,086 4% 2,556 12% 5,476 31% Upper 95% CI 1,919 7% 2,424 9% 4,867 24% 8,410 48%

GE 500 Number HUs 447 2% 747 3% 2,869 14% 4,980 29% Lower 95% CI 0 0% 274 1% 1,779 9% 3,712 21% Upper 95% CI 1,024 3% 1,219 4% 3,959 19% 6,247 36%

Missing Number HUs 299 1% 851 3% 361 2% 220 1% No sills Number HUs 1,456 5% 371 1% 349 2% 45 0% Lower 95% CI 456 2% 0 0% 0 0% 0 0% Upper 95% CI 2,456 8% 762 3% 730 4% 143 1%

a Missing means that the sill was present, but that no lead value is available ( either the sample was not collected, e. g., due to inaccessibility or respondent refusal, or the laboratory did not submit a value). " No sill present" means that there was no sill in the HU, e. g., windows were flush with the wall, or awning windows were installed. b All percentages are calculated with total housing units ( 95,688) as the denominator.

c LT equals " less than." GT equals " greater than or equal to." LOD equals " limit of detection." d " Housing units" include permanently occupied, noninstitutional housing units in which children are permitted to live. e CI = 95% confidence interval for the estimated number or percent. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 5 13 October 31, 2002 Table 5.5c Maximum Window Trough Dust Lead Loading by Year of Construction Year of Construction 1978 1998 1960 1977 1940 1959 Before 1940 Maximum Window Trough Dust Lead Loading ( µ g/ sq ft) a Number ( 000) Percent (%) b Number ( 000) Percent (%) Number ( 000) Percent (%) Number ( 000) Percent (%)

LT LODc Number HUsd 280 1% 94 0% 0 0% 0 0% Lower 95% CIe 0 0% 0 0% 0 0% 0 0%

Upper 95% CI 681 2% 235 1% 0 0% 0 0%

GE LOD Number HUs 20,969 70% 20,319 73% 16,406 80% 14,943 86% Lower 95% CI 17,718 60% 17,730 64% 14,638 73% 13,192 80%

Upper 95% CI 24,221 81% 22,909 82% 18,174 86% 16,694 91%

GE 800 Number HUs 2,252 8% 3,788 14% 6,286 31% 8,883 51% Lower 95% CI 1,032 4% 2,504 9% 4,500 21% 7,084 41%

Upper 95% CI 3,473 12% 5,072 18% 8,073 40% 10,683 61%

Missing Number HUs 4,184 14% 5,885 21% 2,966 14% 2,322 13% No troughs Number HUs 4,341 15% 1,576 6% 1,191 6% 210 1% Lower 95% CI 2,380 8% 732 3% 368 2% 0 0%

Upper 95% CI 6,301 21% 2,419 9% 2,014 10% 451 3%

a Missing means that the trough was present, but that no lead value is available ( either the sample was not collected, e. g., due to inaccessibility or respondent refusal, or the laboratory did not submit a value). " No trough present" means that there was no trough in the HU, e. g., windows were flush with the wall, or awning windows were installed. b All percentages are calculated with total housing units of that age as the denominator.

c LT equals " less than." GT equals " greater than or equal to." LOD equals " limit of detection." d " Housing units" include permanently occupied, noninstitutional housing units in which children are permitted to live e CI = 95% confidence interval for the estimated number or percent.

Tables 5.6a through 5.6c present floor, window sill, and window trough dust loading distributions by household income level. There are some significant differences shown in the table. A greater percent of homes in the higher income level have lower lead dust loadings. For example, 47 percent of higher income homes have lead dust loadings on floors below the limit of detection, while only 29 percent of homes in the lower income level have loadings below the limit of detection. Only 1 percent of homes in the higher household income level exceed 100 µ g/ ft2 floor dust lead loading, while 5 percent of lower income level homes exceed this loading. Similar trends are observed for window sill and trough dust loadings.

Although the data have not been presented, there were no apparent differences between urbanization categories and dust lead loadings. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 5 14 October 31, 2002 Table 5.6a Maximum Floor Dust Lead Loadings by Household Income Maximum Floor Dust Lead Loading( µ g/ sq ft) a Household Income Less than $ 30,000/ year Equal to or above $ 30,000/ year Number ( 000) Percent (%) b Number ( 000) Percent (%)

LT LODc Number HUsd 9,747 29% 26,508 47% Lower 95% CIe 6,944 23% 22,360 42%

Upper 95% CI 12,550 35% 30,657 53%

GE LOD Number HUs 24,038 71% 29,525 53% Lower 95% CI 19,932 65% 26,065 47%

Upper 95% CI 28,143 77% 32,985 58%

GE 5 Number HUs 13,364 40% 13,215 24% Lower 95% CI 10,562 32% 10,859 20%

Upper 95% CI 16,166 47% 15,571 27%

GE 10 Number HUs 8,276 25% 6,792 12% Lower 95% CI 6,219 19% 5,052 9%

Upper 95% CI 10,332 30% 8,532 15%

GE 20 Number HUs 4,282 13% 4,135 7% Lower 95% CI 3,117 9% 2,782 5%

Upper 95% CI 5,447 17% 5,488 10%

GE 40 Number HUs 2,819 8% 2,170 4% Lower 95% CI 1,710 5% 924 2%

Upper 95% CI 3,927 12% 3,415 6%

GE 100 Number HUs 1,637 5% 435 1% Lower 95% CI 728 2% 57 0%

Upper 95% CI 2,546 8% 813 1%

Missing Number HUs 46 0% 77 0%

a Missing means that the sill or trough was present, but that no lead value is available ( either the sample was not collected, e. g., due to inaccessibility or respondent refusal, or the laboratory did not submit a value). b All percentages are calculated with total housing units in that income class as the denominator.

c LT equals " less than." GT equals " greater than or equal to." LOD equals " limit of detection." d " Housing units" include permanently occupied, noninstitutional housing units in which children are permitted to live. e CI = 95% confidence interval for the estimated number or percent. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 5 15 October 31, 2002 Table 5.6b Maximum Window Sill Lead Dust Loadings by Household Income Household Income Less than $ 30,000/ year Equal to or Above $ 30,000/ year Window Sill Dust Lead Loading( µ g/ sq ft) a Number ( 000) Percentb Number ( 000) Percent LT LODc Number HUsd 1,448 4% 7,111 13% Lower 95% CIe 376 1% 5,291 9%

Upper 95% CI 2,520 7% 8,931 16%

GE LOD Number HUs 29,948 89% 47,597 85% Lower 95% CI 24,656 84% 42,665 81%

Upper 95% CI 35,241 93% 52,528 89%

GE 125 Number HUs 10,322 31% 8,865 16% Lower 95% CI 7,909 26% 6,896 13%

Upper 95% CI 12,735 36% 10,835 19%

GE 250 Number HUs 7,671 23% 4,772 9% Lower 95% CI 5,776 18% 3,611 7%

Upper 95% CI 9,565 28% 5,933 11%

GE 500 Number HUs 4,395 13% 3,893 7% Lower 95% CI 2,943 9% 2,773 5%

Upper 95% CI 5,846 17% 5,014 9%

Missing Number HUs 1,137 3% 594 1% No sills Number HUs 1,297 4% 809 1% Lower 95% CI 250 1% 151 0%

Upper 95% CI 2,345 7% 1,466 3%

a Missing means that the sill or trough was present, but that no lead value is available ( either the sample was not collected, e. g., due to inaccessibility or respondent refusal, or the laboratory did not submit a value). " No sill/ trough present" means that there was no sill or trough in the HU, e. g., windows were flush with the wall, or awning windows were installed. b All percentages are calculated with total housing units in that income class as the denominator.

c LT equals " less than." GT equals " greater than or equal to." LOD equals " limit of detection." d " Housing units" include permanently occupied, noninstitutional housing units in which children are permitted to live. e CI = 95% confidence interval for the estimated number or percent. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 5 16 October 31, 2002 Table 5.6c Maximum Window Trough Lead Dust Loadings by Household Income Maximum Window Trough Dust Lead Loading( µ g/ sq ft) a Household Income Less than $ 30,000/ year Equal to or Above $ 30,000/ year Number ( 000) Percentb Number ( 000) Percent LT LODc Number HUsd 59 0% 315 1% Lower 95% CIe 0 0% 0 0%

Upper 95% CI 180 1% 723 1%

LT 800 Number HUs 25,985 77% 42,253 75% Lower 95% CI 21,486 70% 37,300 69%

Upper 95% CI 30,485 84% 47,205 81%

GE 800 Number HUs 9,449 28% 10,623 19% Lower 95% CI 6,742 20% 8,067 15%

Upper 95% CI 12,156 36% 13,179 23%

Missing Number HUs 5,624 17% 8,788 16% No troughs Number of HUs 2,162 6% 4,755 9% Lower 95% CI 869 3% 3,009 5%

Upper 95% CI 3,456 10% 6,501 12%

a Missing means that the sill or trough was present, but that no lead value is available ( either the sample was not collected, e. g., due to inaccessibility or respondent refusal, or the laboratory did not submit a value). " No sill/ trough present" means that there was no sill or trough in the HU, e. g., windows were flush with the wall, or awning windows were installed. b All percentages are calculated with total housing units in that income class as the denominator.

c LT equals " less than. " GE equals " greater than or equal to." LOD equals " limit of detection."

d " Housing units" include permanently occupied, noninstitutional housing units in which children are permitted to live.

e CI = 95% confidence interval for the estimated number or percent.

Figure 5.646 shows the distribution of the dust lead loadings by room type: kitchen, common living area, bedroom, and other room. For these four room types, both floor dust and window dust have been combined. Dust loadings for the main entrance are also shown in the figure, but these are only floor loadings since no data were collected from main entrance windows. Figure 5.7 shows the distribution of the dust lead measurements by surface and carpet. In both figures, the distributions are extremely right skewed. Except for troughs, none of the boxes extend above 40 µ g/ ft2, which means that the 75th percentile is less than 40 µ g/ ft2.

However, there are dust lead loadings well above 10,000 µ g/ ft2. On troughs, they extend above 100,000 µ g/ ft2.

Table 5.7 presents selected parameters of the distributions of dust lead loadings by surface types,

corresponding to the boxplots in Figure 5.7. Table 5.7 also presents geometric means and standard deviations.

46 Dust lead loading data is presented in box plot form. Each box plot shows a univariate data distribution, for example, the dust samples collected from a specific location ( e. g., entrance floor). The box in the box plot represents the middle 50 percent of the data; the bottom of the box gives the 25th percentile; the top of the box gives the 75th percentile, and the horizontal line inside the box gives the median or 50th percentile. The vertical lines extending from the top and bottom of the box reach to the largest and smallest observations, respectively, except for outliers. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 5 17 October 31, 2002 The distributions in Table 5.7 are all right skewed, so that they are not normally distributed. A better model would be the lognormal distribution. Appendix C includes a discussion of distributional models for these data.

Figure 5.6 Box Plots for Dust Lead Loadings by Room a The first four plots include floor and window loadings. Main entrance only includes floors since no data were collected from main entrance windows.

b The box in the box plot represents the middle 50 percent of the data; the bottom of the box gives the 25th percentile; the top of the box gives the 75th percentile, and the horizontal line inside the box gives the median or 50th percentile. The vertical lines extending from the top and bottom of the box reach to the largest and smallest observations, respectively, except for outliers. 0.01 0.1 1 10 100 1000 10000 100000 1000000 Kitchen Living Room Bedroom Other Room Main Entrance ( Only Floors)

Room Type Dust Lead Loading ( µ g/ sq ft) National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 5 18 October 31, 2002 Figure 5.7 Box Plots for Dust Lead Loadings by Surface a The box in the box plot represents the middle 50 percent of the data; the bottom of the box gives the 25th percentile; the top of the box gives the 75th percentile, and the horizontal line inside the box gives the median or 50th percentile. The vertical lines extending from the top and bottom of the box reach to the largest and smallest observations, respectively, except for outliers. 0.01 0.1 1 10 100 1000 10000 100000 1000000 All Floors Carpeted Floors Non Carpeted Floors Window Sills Window Troughs Surface Dust Lead Loading ( µ g/ sg ft) National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 5 19 October 31, 2002 Table 5.7 Estimated Empirical Distribution Parameters of Dust Lead Loadings by Surface Types Floors Window Sills Window Troughs µ g/ ft2 µ g/ ft2 µ g/ ft2 Arithmetic Mean 13.6 194.9 1,990.9 Arithmetic Standard Deviation 483.5 1682.7 12,086.5 Geometric Mean 1.1 9.4 96.4 Geometric Standard Deviationa 3.8 9.3 14.4 25th Percentile .375 2.0 18.0 Median 0.9 8.3 89.1 75th Percentile 2.0 37.13 462.0 90th Percentile 6.0 172.8 2,824.2 95th Percentile 13.2 524.9 6,974.6 Number of Samples 3,894 2,302 1,607 a The geometric standard deviation is computed as exp( s), where s is the arithmetic standard deviation of the natural logarithms of the loadings ( see, e. g., Gilbert, R. O. ( 1987) Statistical Methods for Environmental Pollution Monitoring, Van Nostrand Reinhold Company New York). b For this table, values below 0.375 were set equal to 0.375, which is ¼ of the limit of detection.

5.3 Association between Interior Dust Lead Hazards and Interior LBP Condition Figure 5.8 presents the prevalence of interior dust lead hazards in relation to the condition of the interior LBP. Table 5.8 presents further details on these estimates. Dust lead hazards are more likely to exist in homes with deteriorated LBP. An estimated 61 percent (+ 20%) of homes with significantly deteriorated LBP have lead dust hazards, while only 33 percent (+ 7%) of homes with LBP in good condition have lead dust hazards. Only 6 percent (+ 2%) of homes with no interior LBP have lead dust hazards. Although it appears from the data that the presence of LBP, especially significantly deteriorated LBP, contributes to higher dust lead hazard, there are additional sources of lead in the environment to account for dust lead in homes with no lead based paint.

Table 5.8 also allows one to compare the relative risks ( 95 percent confidence intervals on that risk are not shown in the table) of interior lead dust hazards associated with different paint conditions. The presence of significantly deteriorated LBP makes a house 1.8 (+ 0.5) times as likely to have an interior lead dust hazard compared to a house where the LBP is in good condition, and 10.0 (+ 1.9) times as likely as a house without LBP. Even a house with LBP in good condition is 5.4 (+ 0.8) times as likely to have interior lead dust hazards as one without any LBP. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 5 20 October 31, 2002 Figure 5.8 Association Between Dust Lead Hazards and Condition of Interior Lead Based Paint Table 5.8 Association Between Dust Lead Hazards and Presence and Condition of Interior Lead Based Paint No LBP on Interior or Exterior No Interior LBP Interior LBP in Good Condition Significantly Deteriorated Interior LBP Interior Dust Lead Hazards Number ( 000) Percent (%) Number ( 000) Percent (%) Number ( 000) Percent (%) Number ( 000) Percent (%) Estimatea 55,105 95% 62,752 94% 15,244 67% 2,389 39%

Lower 95% CIb 51,893 90% 60,141 90% 12,633 56% 1,565 26% None Present Upper 95% CI 58,318 100% 65,363 98% 17,855 78% 3,213 53%

Estimate 2,686 5% 4,068 6% 7,508 33% 3,727 61%

Lower 95% CI 1,372 2% 2,584 4% 6,024 26% 2,505 41% Some Present Upper 95% CI 4,001 7% 5,552 8% 8,992 40% 4,949 81%

Total HUs 57,791 100% 66,820 100% 22,752 100% 6,116 100%

a Estimate is either the number of permanently occupied, noninstitutional housing units ( 000) in which children are permitted to live, or the percentage of total housing units. b CI = 95% confidence interval for the estimated number or percent. 0 10,000 20,000 30,000 40,000 50,000 60,000 70,000 No LBP on Interior or Exterior No Interior LBP Interior LBP in Good Condition Significantly Deteriorated LBP Number of Housing Units ( 000) Interior Dust Lead Hazards No Interior Dust Lead Hazards National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 5 21 October 31, 2002 Tables 5.9 and 5.10 present data on the association between floor and sill dust lead loadings and the presence of interior lead based paint. Both tables show a positive relationship between the presence of interior lead based paint and dust lead levels. Housing units with some interior LBP are twice as likely to have floor dust, and three times as likely to have window sill dust, above hazardous levels compared to housing units without LBP.

Table 5.9 Association Between Floor Dust Lead Loadings and Presence of Interior Lead Based Paint Interior Lead Based Paint None Present Some Present Maximum Floor Dust Lead Loading ( µ g/ sq ft) a Number ( 000) Percent (%) b Number ( 000) Percent (%)

LT LODc Number HUsd 32,873 34% 5,496 6% Lower 95% CIe 29,475 31% 3,529 4%

Upper 95% CI 36,270 38% 7,463 8%

GE LOD Number HUs 33,824 35% 23,372 24% Lower 95% CI 30,086 31% 19,997 21%

Upper 95% CI 37,561 39% 26,748 28%

GE 5 Number HUs 12,242 13% 15,958 17% Lower 95% CI 9,835 10% 13,372 14%

Upper 95% CI 14,650 15% 18,544 19%

GE 10 Number HUs 6,003 6% 9,961 10% Lower 95% CI 4,238 4% 7,615 8%

Upper 95% CI 7,768 8% 12,307 13%

GE 20 Number HUs 2,493 3% 6,496 7% Lower 95% CI 1,606 2% 4,661 5%

Upper 95% CI 3,381 4% 8,331 9%

GE 40 Number HUs 1,666 2% 3,830 4% Lower 95% CI 993 1% 2,378 3%

Upper 95% CI 2,338 3% 5,281 6%

GE 100 Number HUs 1,122 1% 1,304 1% Lower 95% CI 419 0% 654 1%

Upper 95% CI 1,825 2% 1,954 2%

Missing Number HUs 123 a Missing means that the sill or trough was present, but that no lead value is available ( either the sample was not collected, e. g., due to inaccessibility or respondent refusal, or the laboratory did not submit a value). b All percentages are calculated with total housing units as the denominator. c LT equals " less than." GE equals " greater than or equal to." LOD equals " limit of detection." d " Housing units" include permanently occupied, noninstitutional housing units in which children are permitted to live. e CI = 95% confidence interval for the estimated number or percent. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 5 22 October 31, 2002 Table 5.10 Association Between Window Sill Dust Lead Loadings and Presence of Interior Lead Based Paint Interior Lead Based Paint None Present Some Present Maximum Window Sill Dust Lead Loading ( µ g/ sq ft) a Number ( 000) Percent (%) b Number ( 000) Percent (%)

LT LODc Number HUsd 8,728 9% 874 1% Lower 95% CIe 6,544 7% 187 0%

Upper 95% CI 10,912 12% 1,562 2%

GE LOD Number HUs 54,454 57% 27,680 29% Lower 95% CI 51,195 54% 24,515 26%

Upper 95% CI 57,713 60% 30,845 32%

GE 125 Number HUs 6,553 7% 13,785 14% Lower 95% CI 5,043 5% 11,177 12%

Upper 95% CI 8,063 8% 16,393 17%

GE 250 Number HUs 3,434 4% 10,005 11% Lower 95% CI 2,193 2% 8,096 9%

Upper 95% CI 4,675 5% 11,914 13%

GE 500 Number HUs 1,498 2% 7,544 8% Lower 95% CI 651 1% 5,770 6%

Upper 95% CI 2,346 3% 9,318 10%

No sill present in HUa Number HUs 2,043 0% 178 0% Missing Number HUs 1,595 136 a Missing means that the sill was present, but that no lead value is available ( either the sample was not collected, e. g., due to inaccessibility or respondent refusal, or the laboratory did not submit a value). b All percentages are calculated with total housing units as the denominator. c LT equals " less than." GE equals " greater than or equal to." LOD equals " limit of detection." d " Housing units" include permanently occupied, noninstitutional housing units in which children are permitted to live. e CI = 95% confidence interval for the estimated number or percent. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 6 1 October 31, 2002 6. RESIDENTIAL SOIL LEAD Chapter 6 presents estimates of the prevalence of soil lead by lead concentration, and the association between soil lead concentration and exterior lead based paint condition. Relevant estimates are compared with the findings of the 1990 LBP Survey. The prevalence of soil lead hazards in housing is presented in Chapter 3. Since soil lead hazards include lead in soil in children's play areas, most estimates in this Chapter are based on the subsample of 375 homes with data on the presence or absence of children's play areas in the yards and on the extent of soil lead hazards in children's play areas. A few tables in this chapter are independent of the presence or absence of lead contaminated soil in children's play areas; such tables are therefore based on the full sample and have a footnote indicating that the basis is the full sample.

6.1 Prevalence of Residential Soil Lead Over All Sampled Locations A composite soil sample was collected at each of five sites on the property of each dwelling unit:

1) near the most commonly used entrance, 2) the dripline and 3) the mid yard line of the wall with the main entrance, and 4) the dripline and 5) mid yard line of a second, randomly selected wall. The main entrance sample was a composite sample of two cores from the main entrance area. The dripline and mid yard samples on each wall were composite samples from three locations along the length of the sample site. In addition, soil samples were collected from children's play areas for a subsample of homes. At each of these homes, up to four samples were collected from children's play equipment, when present; otherwise, one sample was collected from an area of the yard identified as being where children play. The tables in this section and in Section 6.2 are based on the lead concentration data from all of these soil samples, referenced as " all sampled locations." Section 6.3 then presents data on soil lead concentrations in children's play areas, while Section 6.4 presents corresponding data for the " rest of the yard," i. e., areas not identified as children's play areas.

Figure 6.1 and Table 6.1 present the distribution of maximum bare soil lead concentrations.

Figure 6.1 presents a histogram of the distribution, while Table 6.1 presents the number and percentage of HUs by selected soil lead concentration thresholds: 0, 20, 50, 200, 400, 1,200, 1,600, 2,000, and 5,000 ppm.

Figure 6.1 and Table 6.1 include bare soil from all sampled locations, both play areas and all other locations.

An estimated 58 percent ( ± 8%) of homes have soil lead levels above the limit of detection. 47 An estimated 10 47 The sample limit of detection for this study was determined to be 20 ppm by testing four distinct soil types from among the study samples in accordance with EPA SW 840 Method 3050 procedures. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 6 2 October 31, 2002 percent ( ± 4%) 48 of homes have soil lead levels above 400 ppm, and 7% ( ± 4%) have soil lead levels above 1,200 ppm. Only 3 percent of homes were found to have soil lead above 2,000 ppm. The maximum soil values for each HU have been used in Table 6.1. The effect of using the average soil lead for each HU would drive the distribution towards the lower thresholds, i. e. more homes have lower average soil lead concentrations.

Care is to be exercised in comparing the tables in this Chapter with Table 3.3, which tabulate the prevalence of soil lead hazards. The tables in this chapter present the distribution of residential soil lead concentrations at selected locations, while soil lead hazards are defined in terms of soil lead concentrations in two types of locations. Specifically, a housing unit is defined to have a soil lead hazard if soil lead concentrations exceed 400 ppm in play areas or exceed 1,200 ppm in the rest of the yard. Thus, the tables in this section do not directly compare with Table 3.3.

Figure 6.1 Distribution of Maximum Bare Soil Lead Concentrations 48 All confidence intervals are at the 95 percent level for the estimated number or percentage. 0 10 20 30 40 50 < 20 20 50 50 200 200 400 400 1200 1200 1600 1600 2000 2000 5000 > 5000 Lead Concentrations ( ppm) HUs (%) National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 6 3 October 31, 2002 Table 6.1 Distribution of Maximum Bare Soil Sample Lead Concentrations ( All Sampled Locations)

Bare Soil Lead Number of HUs ( 000) a Percent of HUs (%) b Estimate Lower 95% CIc Upper 95% CI Estimate Lower 95% CI Upper 95% CI GEd0 ppm 77,888 72,054 83,722 81% 75% 88% GE 20 ppm 55,114 47,348 62,881 58% 50% 66% GE 50 ppm 40,023 31,365 48,680 42% 33% 51% GE 200 ppm 15,299 11,626 18,971 16% 12% 20% GE 400 ppm 9,996 6,398 13,594 10% 7% 14% GE 1,200 ppm 6,271 2,733 9,809 7% 3% 10% GE 1,600 ppm 3,900 1,670 6,131 4% 2% 6% GE 2,000 ppm 3,124 827 5,420 3% 1% 6% GE 5,000 ppm 1,580 0 3,309 2% 0% 4% No Bare Soil 15,413 9,789 21,037 16% 10% 22% No Soil 2,242 330 4,154 2% 0% 4% Missinge 145 0 527 0% 0% 1%

a " Housing units" include permanently occupied, noninstitutional housing units in which children are permitted to live. b All percentages are calculated with total housing units ( 95,688) as the denominator. c CI = 95% confidence interval for the estimated number or percent. d GE equals " greater than or equal to." e " Missing" means that soil was present, but that no lead value is available ( either the sample was not collected, e. g. due to inaccessibility or respondent refusal, or the laboratory did not submit a value). " No soil" means that there was no soil on the property to sample.

Table 6.2 presents the number and percentage of housing units by construction year for selected soil lead concentration thresholds for bare soil only, again for all sampling locations. As seen above for all soil, as the soil lead threshold increases, the number of newer homes meeting the criteria for bare soil decreases faster than the older homes. In fact, practically no newer homes ( 1960 1998) have lead in bare soil above 1,200 ppm, and less than 4 percent have soil lead above 400 ppm. 49 Thus, the data suggest that older homes have higher bare soil lead levels than new homes. Since the amount of lead added to commercial residential paint declined from 1940 to 1980, these observations are not unreasonable, and have been reported by others. 50 49 Even fewer homes will have greater than 9 square feet of bare soil above 400 ppm or 2,000 ppm ( soil lead hazard as specified in the Lead Safe Housing Rule).

50 Francek, M. ( 1992.) Soil lead levels in a small town environment: A case study from Mt. Pleasant, Michigan. Environmental Pollution 76. pp. 251 257. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 6 4 October 31, 2002 Table 6.2 Distribution of Maximum Bare Soil Sample Lead Concentration by Construction Year ( All Sampled Locations)

Bare Soil Lead Concentration Number of HUs ( 000) a Percent of HUs (%) b Before 1940 1940  1959 1960   1977 1978  1998 Before 1940 1940  1959 1960  1977 1978  1998 GEc 0 ppm 12,015 16,843 23,185 25,845 69% 82% 83% 87% GE 20 ppm 12,015 15,404 17,345 10,350 69% 75% 62% 35% GE 50 ppm 11,193 12,789 10,437 5,603 64% 62% 37% 19% GE 200 ppm 7,243 6,073 1,793 190 41% 30% 6% 1% GE 400 ppm 5,148 3,736 1,111 0 30% 18% 4% 0% GE 1,200 ppm 3,386 2,886 0 0 19% 14% 0% 0% GE 1,600 ppm 2,006 1,894 0 0 12% 9% 0% 0% GE 2,000 ppm 1,320 1,804 0 0 8% 9% 0% 0% GE 5,000 ppm 1,106 475 0 0 6% 2% 0% 0% Missingd 145 0 0 0 1% 0% 0% 0% No Bare Soil 4,313 2,762 4,613 3,724 25% 13% 17% 13% No Soil 1,003 939 95 205 6% 5% 0% 1% Total 17,476 20,544 27,893 29,774 100% 100% 100% 100%

a " Housing units" include permanently occupied, noninstitutional housing units in which children are permitted to live. b All percentages are calculated with total housing units of that age as the common denominator. c GE equals " greater than or equal to." d Missing means that soil was present, but that no lead value is available ( usually due to inaccessibility or respondent refusal). " No soil" means that there was no soil on the property to sample.

Figure 6.2 presents a series of boxplots51 showing the distribution of soil lead concentrations at each of the seven sample sites. The last two boxplots represent only the data collected during the supplemental data collection from play areas. As with paint lead and dust lead loadings, soil lead concentrations are extremely skewed with over three fourths of the samples under 200 ppm, but some samples are well above 1,000 ppm.

Table 6.3 presents selected parameters of the distributions of soil lead concentrations by sample sites, corresponding to the first five boxplots in Figure 6.2. Table 6.3 also presents geometric means and standard deviations. As with the distributions of paint lead loadings and dust lead loadings, the distribution of soil lead concentrations is right skewed. Thus, a normal distribution would not be a suitable model for the distribution. A lognormal distribution would be a more suitable distribution. Appendix C includes a discussion of modeling these data.

51 Soil lead concentration data is presented in box plot form. Each box plot shows a univariate data distribution, for example, the soil samples collected from a specific location ( e. g., main entry). The box in the box plot represents the middle 50 percent of the data; the bottom of the box gives the 25th percentile; the top of the box gives the 75th percentile; and the horizontal line inside the box gives the median or 50th percentile. The vertical lines extending from the top and bottom of the box reach to the largest and smallest observations, respectively, except for outliers. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 6 5 October 31, 2002 Figure 6.2 Box Plots for Lead in Soil Samples by Sample Site a The box in the box plot represents the middle 50 percent of the data; the bottom of the box gives the 25th percentile; the top of the box gives the 75th percentile, and the horizontal line inside the box gives the median or 50th percentile. The vertical lines extending from the top and bottom of the box reach to the largest and smallest observations, respectively, except for outliers.

b " Wall 1" refers to the main entrance wall and " Wall 2" refers to the second, randomly selected wall. 1 10 100 1000 10000 100000 Main Entry Wall 1 Dripline Wall 2 Dripline Wall 1 Midyard Wall 2 Midyard Play area Under Play Equipment Soil Sample Location Soil Lead Concentration ( ppm) National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 6 6 October 31, 2002 Table 6.3 Estimated Empirical Distribution Parameters of Soil Lead Concentrations by Sample Site Main Entry Wall 1 Dripline Wall 2 Dripline Wall 1 Midyard Wall 2 Midyard ppm ppm ppm ppm ppm Arithmetic Mean 234.8 242.9 404.1 87.3 123.4 Arithmetic Standard Deviation 1,094.4 817.6 1,612.7 194.7 360.4 Geometric Mean 43.3 44.5 49.0 28.1 29.9 Geometric Standard Deviationa 5.6 5.8 6.8 4.3 4.9 25th Percentile 12.1 11.4 10.8 7.8 8.5 Median 40.2 38.8 40.3 27.0 29.1 75th Percentile 133.4 130.7 165.4 76.3 74.2 90th Percentile 433.5 553.5 712.5 209.0 277.0 95th Percentile 1,005.8 1,110.8 1,444.5 411.3 538.8 Number of Samples 707 704 704 723 728 a The geometric standard deviation is computed as exp( s), where s is the arithmetic standard deviation of the natural logarithms of the concentrations ( see, e. g., Gilbert, R. O. ( 1987) Statistical Methods for Environmental Pollution Monitoring, Van Nostrand Reinhold Company New York). For the calculations of the geometric mean and standard deviation, zero and negative values were set to 5.

6.2 Association between Bare Soil Lead and Exterior Paint Condition Table 6.4 and Figure 6.3 show the association between bare soil lead concentration and the condition of the exterior LBP. Higher bare soil lead concentrations occur for homes with deteriorated LBP.

An estimated 56 percent ( ± 8%) of homes with intact or minimally deteriorated LBP have bare soil lead above 20 ppm, while 73 percent ( ± 19%) of homes with significantly deteriorated LBP have bare soil levels above 20 ppm. Only 4 and 2 percent of homes free of significantly deteriorated LBP have bare soil lead levels above 1,200 and 2,000 ppm, respectively, while 24 and 13 percent of homes with significantly deteriorated LBP have bare soil lead levels above 1,200 and 2,000 ppm, respectively. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 6 7 October 31, 2002 Table 6.4 Association Between Bare Soil Lead Concentration and Presence of Significantly Deteriorated Exterior LBP ( All Sampled Locations)

Bare Soil Lead Housing Units without Any Exterior LBPa, b Housing Units without Significantly Deteriorated Exterior LBPa, b Housing Units with Significantly Deteriorated Exterior LBPa, b Percent Lower 95% CIc Upper 95% CI Percent Lower 95% CI Upper 95% CI Percent Lower 95% CI Upper 95% CI GEd0 ppm 83% 78% 88% 83% 77% 88% 73% 55% 92% GE 20 ppm 49% 41% 56% 56% 48% 63% 73% 54% 92% GE 50 ppm 28% 20% 36% 38% 30% 47% 67% 51% 83% GE 200 ppm 5% 1% 9% 13% 9% 17% 39% 19% 58% GE 400 ppm 3% 0% 5% 8% 5% 11% 30% 11% 49% GE 1,200 ppm 1% 0% 3% 4% 2% 7% 24% 7% 41% GE 1,600 ppm 1% 0% 3% 2% 1% 4% 17% 4% 30% GE 2,000 ppm 1% 0% 2% 2% 0% 4% 13% 2% 24% GE 5,000 ppm 0% 0% 0% 1% 0% 2% 8% 0% 17% Missinge 0% 0% 0% 30% 0% 0% 1% 0% 5% No Bare Soil 14% 10% 19% 15% 11% 20% 22% 3% 41% No Soil 3% 0% 6% 2% 0% 4% 4% 0% 9% Total 100% 100% 100%

a " Housing units" include permanently occupied, noninstitutional housing units in which children are permitted to live. b The denominators for the percentages are 66,032,000 HUs without any exterior LBP, 84,215,000 HUs without significantly deteriorated exterior LBP, and 11,473,000 HUs with significantly deteriorated exterior LBP. c CI = 95% confidence interval for the estimated number or percent. d GE equals " greater than or equal to." e Missing means that soil was present, but that no lead value is available ( usually due to inaccessibility or respondent refusal). " No soil" means that there was no soil on the property to sample. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 6 8 October 31, 2002 Figure 6.3 Association Between Lead in Bare Soil and Deteriorated Exterior Lead Based Paint 6.3 Prevalence of Bare Soil Lead in Children's Play Areas Table 6.5 presents the number and percentage of housing units with bare soil lead in children's play areas above selected concentration thresholds: 0, 20, 50, 200, 400, 1,200, 1,600, 2,000, and 5,000 ppm.

Figure 6.4 presents the point estimates as a histogram. An estimated 51 percent ( ± 6%) of homes have bare soil lead levels in play areas above the limit of detection. 52 An estimated five percent ( ± 3%) of homes with play areas have soil lead levels above 400 ppm, while an estimated two percent ( ± 2%) of homes have play area soil lead levels above 2,000 ppm.

Where more than one soil sample was collected from children's play areas at a home, the maximum soil value for housing unit has been used in Table 6.5. The effect of using the average soil lead for each housing unit would drive the distribution towards the lower thresholds, i. e. more homes would have lower soil lead concentrations.

52 The sample limit of detection for this study was determined to be 20 ppm by testing four distinct soil types from among the study samples in accordance with EPA Method 3050 procedures. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90%

GE 0 GE 20 GE 50 GE 200 GE 400 GE 1,200 GE 1,600 GE 2,000 GE 5,000 Bare Soil Lead Concentration ( ppm) Percent of Housing Units Housing Units without Any Exterior LBP Housing Units without Significantly Deteriorated Exterior LBP Housing Units with Significantly Deteriorated Exterior LBP National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 6 9 October 31, 2002 Figure 6.4 Distribution of Maximum Bare Play Area Soil Lead Concentration Table 6.5 Distribution of Maximum Soil Lead Concentrations in Children's Play Areas Number of HUs ( 000) a Percent of HUs (%) b Bare Play Area Soil Lead HUs in Sample Estimate Lower 95% CIc Upper 95% CI Estimate Lower 95% CI Upper 95% CI GEd0 ppm 76,404 69,826 82,982 80% 73% 87% 294 GE 20 ppm 49,019 42,946 55,092 51% 45% 58% 209 GE 50 ppm 28,878 25,828 31,929 30% 27% 33% 127 GE 200 ppm 10,849 7,899 13,800 11% 8% 14% 101 GE 400 ppm 4,856 2,096 7,616 5% 2% 8% 84 GE 1,200 ppm 2,493 458 4,529 3% 1% 5% 82 GE 1,600 ppm 2,078 92 4,063 2% 0% 4% 80 GE 2,000 ppm 1,777 0 3,871 2% 0% 4% 77 GE 5,000 ppm 380 0 1,231 0% 0% 1% 1 No play area 12,368 6,659 18,077 13% 7% 19% 53 Missinge 6,916 1,862 11,969 7% 2% 13% 23 Total 95,688 100% 375 a " Housing units" are permanently occupied, noninstitutional residential units in which children are permitted to live. b All percentages are calculated with total housing units ( 95,688) as the denominator. c CI = 95% confidence interval for the estimated number or percent. d GE equals " greater than or equal to." e Missing means that soil was present, but that no lead value is available ( usually due to inaccessibility or respondent refusal). " No soil" means that there was no soil on the property to sample. 0 10 20 30 40 50 < 20 20 50 50 200 200 400 400 1200 1200 1600 1600 2000 2000 5000 > 5000 Lead Concentrations ( ppm) HUs (%) National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 6 10 October 31, 2002 Table 6.6 presents the number and percentage of housing units with bare soil lead concentration in children's play areas by selected thresholds, by housing unit construction year. In general, as the soil lead threshold increases, the number of homes meeting the criteria decreases as the housing unit age increases. In fact, nearly all newer homes ( 1960 1998) have bare play area soil lead below 400 ppm. Thus, the data suggest that older homes have higher bare play area soil lead concentrations than new homes. Since the amount of lead added to commercial residential paint declined from 1940 to 1980, these observations are not unreasonable, and have been reported by others. 53 Table 6.6 Distribution of Maximum Soil Lead Concentrations in Children's Play Areas, by Construction Year Number of HUs ( 000) a Percent of HUs (%) b Bare Soil Lead Concentration Before 1940 1940   1959 1960   1977 1978   1998 Before 1940 1940   1959 1960  1977 1978   1998 GEc0 ppm 14,641 15,953 22,536 23,275 84% 78% 81% 78% GE 20 ppm 14,552 13,074 13,238 8,155 83% 64% 48% 27% GE 50 ppm 12,562 8,920 4,733 2,664 72% 43% 17% 9% GE 200 ppm 6,508 2,804 320 1,217 37% 14% 1% 4% GE 400 ppm 3,325 1,469 62 0 19% 7% 0% 0% GE 1,200 ppm 1,498 995 0 0 9% 5% 0% 0% GE 1,600 ppm 1,082 995 0 0 6% 5% 0% 0% GE 2,000 ppm 872 905 0 0 5% 4% 0% 0% GE 5,000 ppm 380 0 0 0 2% 0% 0% 0% No Play Area 613 102 3,410 2,790 13% 22% 7% 13% Missingd 2,222 4,489 1,947 3,710 4% 1% 12% 9% Total 17,476 20,544 27,893 29,774 100% 100% 100% 100%

a " Housing units" are permanently occupied, noninstitutional housing units in which children are permitted to live. b All percentages are calculated with total housing units of that age as the common denominator. c GE equals " greater than or equal to." d Missing means that soil was present, but that no lead value is available ( usually due to inaccessibility or respondent refusal). " No bare soil" means that there was no bare soil in children's play areas on the property to sample.

Table 6.7 shows the association between bare play area soil lead concentration and the condition of the exterior LBP. Higher bare soil lead concentrations occur in play areas for homes with significantly deteriorated LBP. An estimated 46 percent ( ± 7%) of homes with intact or minimally deteriorated LBP have bare play area soil lead above 20 ppm, while 89 percent ( ± 11%) of homes with significantly deteriorated LBP have bare soil levels above 20 ppm. Only three percent ( ± 3%) of homes with intact or minimally deteriorated LBP have bare play area soil lead levels above 400 ppm, while 18 percent ( ± 12%) of homes with significantly deteriorated LBP have bare soil lead levels above 400 ppm.

53 Francek, M. ( 1992.) Soil lead levels in a small town environment: A case study from Mt. Pleasant, Michigan. Environmental Pollution 76. pp. 251 257. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 6 11 October 31, 2002 Table 6.7 Association Between Bare Soil Lead Concentration and Presence of Significantly Deteriorated Exterior LBP, in Children's Play Areas Bare Play Area Soil Lead Housing Units without Significantly Deteriorated Exterior LBP (%) a, b Housing Units with Significantly Deteriorated Exterior LBP (%) a, b Estimate Lower 95% CIc Upper 95% CI Estimate Lower 95% CI Upper 95% CI GEd0 ppm 79% 71% 86% 90% 79% 100% GE 20 ppm 46% 39% 53% 89% 77% 100% GE 50 ppm 24% 20% 29% 73% 55% 91% GE 200 ppm 8% 4% 12% 35% 17% 53% GE 400 ppm 3% 1% 6% 18% 6% 30% GE 1,200 ppm 1% 0% 3% 13% 2% 24% GE 1,600 ppm 1% 0% 3% 11% 0% 23% GE 2,000 ppm 1% 0% 2% 10% 0% 23% GE 5,000 ppm 0% 0% 0% 3% 0% 11% No Play Areas 14% 7% 20% 7% 0% 17% Missinge 8% 2% 14% 3% 0% 7%

a " Housing units" include permanently occupied, noninstitutional housing units in which children are permitted to live. b Percentages are calculated with the number of HUs with and without significantly deteriorated LBP, 11,472 and 84,216, respectively, as the denominators. c CI = 95% confidence interval for the estimated number or percent. d GE equals " greater than or equal to." e Missing means that soil was present, but that no lead value is available ( usually due to inaccessibility or respondent refusal). " No soil" means that there was no soil on the property to sample.

6.4 Prevalence of Soil Lead in the Rest of the Yard Table 6.8 presents the number and percentage of housing units with soil lead in the rest of the yard  i. e., areas not identified as children's play areas  above selected concentration thresholds: 0, 50, 200,

400, 1,200, 1,600, 2,000, and 5,000 ppm. An estimated 75 percent ( ± 6%) of homes have bare soil lead levels in the rest of the yard above the limit of detection. 54 An estimated 10 percent ( ± 4%) of homes have soil lead levels above 1,200 ppm in the rest of the yard, while an estimated 6 percent ( ± 2%) of homes have soil lead levels above 2,000 ppm.

54 The sample limit of detection for this study was determined to be 20 ppm by testing four distinct soil types from among the study samples in accordance with EPA Method 3050 procedures. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 6 12 October 31, 2002 Table 6.8 Distribution of Maximum Soil Lead Concentrations in the Rest of the Yard Soil Lead Concentration Number of HUs ( 000) a Percent of HUs (%) b Estimate Lower 95% CIc Upper 95% CI Estimate Lower 95% CI Upper 95% CI HUs in Sample GEd 0 ppm 90,348 87,218 93,479 94% 91% 98% 323 GE 20 ppm 71,537 65,843 77,230 75% 69% 81% 258 GE 50 ppm 54,250 48,525 59,976 57% 51% 63% 162 GE 200 ppm 27,353 25,438 29,267 29% 27% 31% 116 GE 400 ppm 19,709 16,109 23,310 21% 17% 24% 70 GE 1,200 ppm 9,939 6,435 13,444 10% 7% 14% 53 GE 1,600 ppm 6,220 4,034 8,407 7% 4% 9% 49 GE 2,000 ppm 5,905 3,727 8,083 6% 4% 8% 38 GE 5,000 ppm 2,987 1,548 4,427 3% 2% 5% 17 No Soil/ No Bare Soile 2,310 366 4,254 2% 0% 4% 9 Missinge 3,029 693 5,365 3% 1% 6% 12 Total 95,688 100% 375 a " Housing units" are permanently occupied, noninstitutional residential units in which children are permitted to live. b All percentages are calculated with total housing units ( 95,688) as the denominator. c CI = 95% confidence interval for the estimated number or percent. d GE equals " greater than or equal to." e Missing means that soil was present, but that no lead value is available ( usually due to inaccessibility or respondent refusal). " No soil" means that there was no soil in the rest of the yard to sample. " No bare soil" means there was no bare soil in the rest of the yard.

Table 6.9 presents the number and percentage of housing units with soil lead concentration in the rest of the yard by selected thresholds, and by housing unit construction year. In general, as the soil lead threshold increases, the number of homes meeting the criteria decreases as the housing unit age increases. In fact, nearly all ( 91%) homes built between 1960 and 1977 have bare soil lead concentrations below 400 ppm in the rest of the yard. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 6 13 October 31, 2002 Table 6.9 Distribution of Maximum Soil Lead Concentrations in the Rest of the Yard, by Construction Year Number of HUs ( 000) a Percent of HUs (%) b Bare Soil Lead Concentration Before 1940 1940  1959 1960  1977 1978  1998 Before 1940 1940   1959 1960  1977 1978   1998 GEc0 ppm 15,858 19,372 26,950 28,168 91% 94% 97% 95% GE 20 ppm 15,858 18,947 24,151 12,581 91% 92% 87% 42% GE 50 ppm 15,350 17,492 13,509 7,900 88% 85% 48% 27% GE 200 ppm 13,051 9,524 4,430 348 75% 46% 16% 1% GE 400 ppm 11,255 5,960 2,410 84 64% 29% 9% 0% GE 1,200 ppm 6,326 2,926 686 0 36% 14% 3% 0% GE 1,600 ppm 4,245 1,289 686 0 24% 6% 3% 0% GE 2,000 ppm 3,929 1,289 686 0 23% 6% 3% 0% GE 5,000 ppm 1,891 865 231 0 11% 4% 1% 0% No Soil/ No Bare Soile 1,211 939 160 0 7% 5% 1% 0% Missingd 407 233 783 1,606 2% 1% 3% 5% Total 17,476 20,544 27,893 29,774 100% 100% 100% 100%

a " Housing units" are permanently occupied, noninstitutional housing units in which children are permitted to live. b All percentages are calculated with total housing units of that age as the common denominator. c GE equals " greater than or equal to." d Missing means that soil was present, but that no lead value is available ( usually due to inaccessibility or respondent refusal). e " No soil" means that there was no soil in the rest of the yard to sample. " No bare soil" means there was no bare soil in the rest of the yard.

6.5 Comparison of Prevalence of Soil Lead to the 1990 LBP Survey Table 6.10 compares the prevalence of soil lead found in the NSLAH with the prevalence of soil lead found in the 1990 LBP Survey. The estimate of homes reported for the NSLAH have been limited to those with 500 ppm55 soil lead or greater and to homes built before 1980 for comparability to the 1990 LBP Survey protocols and findings ( see Appendix B for a comparison of the protocols for the two studies).

Statistical comparison shows no significant difference in the prevalence of soil above or below 500 ppm in the two studies.

55 At the time the 1990 LBP survey was conducted, 500 ppm was the guideline in EPA's Interim Guidance on Establishing Soil Lead Cleanup Levels at Superfand Sites, September 7, 1989 ( OSWER Directive # 9355 4 02). National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT 6 14 October 31, 2002 Table 6.10 Comparison of the Prevalence of Lead Contaminated Bare Soil in the NSLAH and the 1990 LBP Survey 1990 LBP Survey ( pre 1980 HUs) Current NSLAH ( pre 1980 HUs) Number ( 000) Percent (%) Number ( 000) Percent and ( CI) a (%) HUs with Bare Soil Lead Above 500 ppm 15,699 20% 15,909 23% ( 19 27%) HUs with Bare Soil Lead Equal to or Below 500 ppm 61,478 80% 50,290 73% ( 70 77%)

No Bare Soil   2,557 4%

Total 77,177 100% 68,756 100%

a CI = 95% confidence interval for the estimated percent. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT October 31, 2002 7 1 7. QUALITY OF THE NATIONAL SURVEY DATA Chapter 7 examines the quality of the data and the resulting quality of projected national estimates. The greatest source of error ( in the statistical sense) in the NSLAH estimates is sampling error

as discussed in Volume II, Chapter 2. This chapter addresses two additional important potential sources of error   nonresponse bias and measurement bias   and discusses their effects on the national estimates of the prevalence of lead based paint ( LBP), lead in dust, and lead in soil. 56 The chapter concludes with a summary of the data collection quality assurance activities,

including results of telephone verification, field team audits, field dust and soil quality control samples,

laboratory performance on dust and soil quality control samples, and paint testing quality control.

7.1 Statistical Concepts and Terminology There are two broad types of error in survey estimates: sampling error and nonsampling error:

Sampling error: Sampling error arises from surveying a random sample rather than a complete census of all housing units ( HUs). It is a function of the sample size and sample design. Different samples of the same size drawn using the same sample design will yield varying estimates of the population parameters. This variation about the true population parameter is the sampling error.

Nonsampling error: Nonsampling errors arise from a number of sources, including differential response rates from different demographic groups, types of HUs, and geographical areas; unknown differences between the respondents and nonrespondents; differences between the sample frame and the target population; some types of processing and data reduction techniques; and classification bias due to measurement error inherent in XRF and laboratory instrumentation and variation in a measured parameter across a surface and among rooms.

Throughout the report, the term weight has been used in conjunction with the sampled HUs,

rooms, and surfaces. It is important that these terms be understood.

56 Another source of error in the survey is response bias, i. e., how correct was the information provided by the respondents? Significant information obtained from respondents included year of construction ( HU age) and age of children. These data were not verified by other means and are thus associated with an unknown amount of error. However, the overall distribution of HU age and age of children reported by survey respondents were consistent with study expectations ( see Volume II, Chapter 2), indicating no systematic bias in these responses. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT October 31, 2002 7 2

Housing Unit ( HU) weight: The HU weight is the number of HUs in the target population that a single HU in the survey represents. The weight is calculated by taking the inverse of the probability of selection for that unit. Thus, if the probability of selection is 0.01, the sample weight is 100. With multi stage samples, the overall probability of selection is the product of the conditional probabilities of selection at each stage. HU weights for this survey reflect nonresponse adjustments and post stratification to the 1997 American Housing Survey ( AHS) housing unit totals by Census region, HU age category, and presence of children under age 18.

Room weight: The room weight is the number of rooms in the target population that a single room in the survey represents. Room weights were determined by dividing the post stratified HU weights by the probability of room selection based on the inventory of all rooms in each HU. A nonresponse adjustment was then made to account for noncompleted rooms. A room was only considered to be complete if some environmental samples and data were collected in the room.

Component weight: The component weight is the number of components in the target population that a single component tested in the survey represents. For most lead samples, the component weight equaled the nonresponse adjusted room weight. There were two exceptions: 1) XRF measurements on windows and doors, and 2) window dust samples. For these components, a sample of one door or window per room was selected. To complete component weights for these components, the nonresponse adjusted room weights were divided by the component probability of selection, i. e., the inverse of the total number of doors or windows in the room.

7.2 Potential for Nonresponse Bias The objective of the nonresponse analysis was to estimate the potential impact of survey nonresponse on the estimated prevalence of LBP in housing. To accomplish this, three analyses were conducted. First, the weighted distribution of the NSLAH sample was compared and found to be comparable with the AHS and CPS ( this analysis was presented in Chapter 2). Second, an analysis of completion rates was performed to look for correlates with nonresponse. Third, the survey estimates for the " hard to recruit" and HUs that initially refused ( proxies for the nonrespondents) were compared with estimates from HUs that were relatively easy to recruit and had no history of refusal.

7.2.1 Analysis of Completion and Response Rates National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT October 31, 2002 7 3 An analysis of completion rates was conducted for the entire sample of 1,984 fielded HUs.

The analysis looked at the relationship between completion rates and factors such as age of housing, race,

ethnicity, geographic location, income, tenure, and presence of multi family housing. Given that these data were generally not available at the individual HU level for the noncompletes, data for the block group to which the HU belonged was used for the entire sample, with the exception of HU age. The housing unit age reported by respondents was used when available, which was the case for approximately one half of the HUs. The source of the block group data was the 1990 Census. Completion rates were also compared for HUs receiving an advance letter addressed to " Current Resident" and HUs receiving a letter addressed to a household member.

The completion rates for the analysis were calculated as the weighted proportion of the HUs sampled that completed both screener and data collection, or else were found to be ineligible. Ineligibles were considered to be screener completes in the sense that their eligibility status was determined during the screener. For a large proportion of the sample ( 39%), eligibility could not be determined, usually because contact could not be made. Most nonresponse occurred at the screener stage and resulted in unknown eligibility status. Of the 1,984 HUs sampled, 831 completed both the screener and data collection and 229 were found to be ineligible. Of the remaining 924 that did not complete the data collection, 149 were eligible and another 775 were of unknown eligibility. Thus, there were 1,060 completes and 924 noncompletes overall. The overall unweighted completion rate for the survey was 53.4 percent; the overall weighted completion rate was 53.1 percent.

Formulas for unweighted screener and data collection completion rates are given below, along with the eligibility rate, refusal rate, and overall response rate. The overall completion rate is calculated as the product of the completion rate at each stage. 57 % 59 984 , 1 229 943 x % 100 fielded # ineligible # completes screener # x % 100 rate completion Screener = + = + =

90% 172 , 1 060 , 1 x 100% ineligible # screener completing eligible # ineligible # collection data completing eligible # x 100% rate completion collection Data = = + + =

57 In the data collection completion rate, the ineligible cases are included in both numerator and denominator. If the ineligible cases are not included, the data collection completion rate drops from 90 to 88 percent. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT October 31, 2002 7 4 The overall response rate measures the response among eligible HUs. The number of eligible nonrespondents must be estimated because eligibility cannot usually be established for households that don't complete the screener. It is assumed that the eligibility rate among HUs whose eligibility is unknown is the same as for HUs that did complete the screener. The eligibility rate among HUs that completed a screener was 81 percent. The refusal rate is the rate of refusal among HUs where contact was established.

( Numerous attempts were made to gain cooperation. Among respondents, two thirds cooperated on the first or second attempt. While the average number of attempts to complete was 2.6, some housing units didn't cooperate until the eleventh attempt.) HUs that were vacant or couldn't be located, that had no one at home, that were in a locked, gated community where access couldn't be gained, or that couldn't otherwise be contacted were subtracted from the total sample size of 1,984 in the denominator. The overall response rate for the survey was 51.7 percent.

Eligibility Rate # Eligible 943 100% x 100% x 81% # Eligible # Ineligible 943 229 = = = + +

Refusal Rate # of refusals 564 100% x 100% x 34.5% # contacted 1,634 = = =

Overall Response Rate # eligible completing data collection 100% x # eligible completing data collection # eligible nonrespondents = +

831 51.7% 831 ( 149 .81* 775) = = + +

Overall completion rates by Census Division and block group characteristics such as race/ ethnicity, housing age, and type of housing are presented in Table 7.1. Mean percents for several characteristics by completion status are given in Table 7.2. For housing age, the predominant building age category for the block group was assigned to the HU, except when HU age was available from survey respondents. It is important to keep in mind that ( with the exception of HU age) the characteristics apply only to the block group in which the HU is located, and may not apply to the HU itself. The associations between completion status and these characteristics were tested using chi square and t tests that take into account the HU weights and the survey design.

Significant associations were found between completion status and percents Hispanic and African American, percent below the federal poverty level, housing age, and tenure ( see Table 7.2). National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT October 31, 2002 7 5 Different completion rates for groups within a category cannot always be explained, but could be due to factors such as the use of incentives, attitudes of householders, etc. In Table 7.1, the highest response rates were found among HUs in block groups with 30 percent or more Hispanic population, 30 percent or more in poverty, and in newer housing ( 1978 or later). The differences in response rates are substantial for these characteristics, ranging from 9 to 14 percentage points or more ( possibly a function of the $ 200 incentive having greater value for these households). This means that if the lead outcome variables are correlated with any of these characteristics ( such as housing age), a greater potential for nonresponse bias would exist had these characteristics not been used in adjusting for nonresponse at the screener and data collection stages. Nonresponse adjustment factors were calculated within cells defined by the block group percent of low income population, percent of Hispanic or African American population, and percent of pre 1940 and pre 1960 housing. In addition, the nonresponse adjusted HU weights were poststratified to 1997 AHS housing unit totals by Census region, housing unit age, and presence of a child under 18. Use of the final adjusted weights in all analyses therefore greatly reduces this potential bias in estimates for the national housing stock.

The presence or absence of a household member name on the advance letter was also significantly correlated with completion rates. For HUs located in higher income block groups ( i. e. fewer than 30 percent of the households are below the federal poverty level), the response rate for HUs with a name on the advance letter was significantly lower ( p = .01) than for HUs receiving a letter addressed to " Current Resident" ( 48% vs. 56%). For HUs located in lower income block groups ( i. e. more than 30 percent of the households are below the federal poverty level), however, the completion rates were not significantly different.

Response rates for the play areas sample were also calculated using the above formula.

Weighted and unweighted response rates were examined in the same manner, but given the smaller sample size the characteristics were restricted to Census Region, building age category, and soil lead. The national response rate for the play areas survey was 79.5 percent weighted and 78.0 percent unweighted ( higher than the national survey since we were returning to previously willing HUs). For each subset, the response rate remained between 71 and 85 percent. None of the response rate differences observed for the play areas survey were statistically significant at the alpha = .10 level. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT October 31, 2002 7 6 Table 7.1 Completion Rates by 1990 Census Block Group Characteristics Unweighted Weighted P Value for 1990 Census Block Group Characteristic Number of HUs Completion Rate Completion Rate Chi square testa Census Division New England 102 52% 53% 0.42 Middle Atlantic 289 53% 49% East North Central 289 49% 46% West North Central 181 55% 55% South Atlantic 326 52% 53% East South Central 144 53% 54% West South Central 208 56% 58% Mountain 136 57% 58% Pacific 309 56% 57% % Hispanic Population Less than 30% Hispanic 1832 52% 52% 0.005 30% or more Hispanic 152 65% 65% % African American Population Less than 30% African American 1731 52% 53% 0.08 30% or more African American 253 60% 59% % Population in Poverty Less than 30% in Poverty 1796 53% 52% 0.04 30% or more in Poverty 188 60% 61% % Multi family Housing Units ( 5+) Less than 30% Multi family HUs 1522 53% 53% 0.42 30% or more Multi family HUs 462 56% 55% Age of Housing Unitb Pre 1940 456 48% 45% < 0.001 1940   1959 363 59% 60% 1960   1977 806 47% 45% 1978 and later 359 70% 74%

a Chi square test between completion rate and housing characteristic  takes into account the HU weights and sample design.

b Reported HU age used when available for HUs completing screener. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT October 31, 2002 7 7 Table 7.2 Mean Percents for Completed and Noncompleted Housing Units by 1990 Census Block Group Characteristics Mean of Characteristic 1990 Census Block Group Characteristic Completes Noncompletes P value for t test between completes and noncompletesa Percent HUs Pre 1940b 18% 25% 0.001 Percent Population below Poverty Level 12% 11% 0.080 Percent Multi Family HUs ( 5+) 17% 16% 0.535 Percent Multi Family HUs ( 20+) 7% 7% 0.908 Percent HUs Owned 63% 66% 0.042 Percent Population: African American 11% 8% 0.006 Percent Population: Hispanic 8% 5% 0.005 a The test takes into account the HU weights and sample design.

b HU age reported by respondents was used when available for HUs completing screener.

7.2.2 Comparison of " Hard to Recruit" Versus " Easy to Recruit" HUs Lead measurements were not available for the HUs whose occupants refused to participate in the survey or who could not be contacted, so it is not possible to know how their participation would have changed the estimates of lead prevalence in housing. However, if the HUs that initially refused but later cooperated ( or those HUs requiring several attempts to complete the screener) are similar to the survey nonrespondents, they may be considered as a proxy group for the nonrespondents. If they are significantly different, this may indicate the likely direction of the nonresponse bias in the lead prevalence estimates.

The initial refusals were compared with HUs with a history of no refusal. HUs requiring 4 or more attempts to complete the screener were also compared with those requiring 3 or fewer attempts. The number of attempts was split at 3 4 for two reasons. Two thirds of respondents cooperated on the first or second attempt and the average number of attempts to complete was 2.6. The comparisons were made for four key statistics and by the housing characteristics recorded by the interviewer. The statistics were 1) the presence of LBP anywhere in the home, 2) the presence of deteriorated LBP anywhere in the home, 3)

presence of LBP hazard anywhere in the home, and 4) the presence of a soil lead hazard. The housing characteristics were the respondent's race/ ethnicity, household income, tenure, building age, and presence of a child under 18. Comparison of whether or not the household had initially refused ( or required more than three attempts to obtain a completed screener) and these characteristics is presented in Table 7.3. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT October 31, 2002 7 8 Table 7.3 Comparison of " Easy to Recruit" Respondents Versus " Hard to Recruit" Respondents National Survey Estimates Initial Refusal (%) p valuea More than 3 Attempts to Complete Screener (%) p valuea Presence of LBP anywhere in HU Yes 9.2 0.60 17.3 0.67 No 10.0 15.1 Presence of Significantly Deteriorated LBP anywhere Yes 6.0 0.05 12.8 0.29 No 10.4 16.7 Presence of Significant LBP Hazard in HU Yes 5.6 0.0007 15.8 0.84 No 11.6 16.5 Presence of Soil Lead Hazard Yes 8.7 0.85 6.2 0.29 No 9.9 16.7 Ethnicity Hispanic 10.7 0.78 9.6 0.14 Non Hispanic 9.7 16.8 Race White 10.2 0.38 16.9 0.12 African American 6.7 11.7 Asian, Pacific Islander, Hawaiian, 8.9 14.4 American Indian, Other Presence of Child under 18 Yes 9.9 0.85 15.1 0.31 No 9.5 16.6 Year of Construction Pre 1940 7.2 0.22 18.6 0.18 1940   1959 6.1 11.5 1960   1977 12.1 13.3 1978 or later 11.4 20.2 Tenure ( moved up to be w/ hsg info) Owned 11.2 0.03 15.8 0.15 Rented 6.3 16.8 Type of Housing Single family 10.3 0.02 15.4 0.58 Multi family 5.8 19.9 Household Income Less than $ 30,000 4.7 < 0.0001 12.3 0.03 $ 30,000 or More 11.7 17.8 Household Income Less than $ 20,000 4.7 0.05 11.1 0.02 $ 20,000  $ 39,999 6.8 15.6 $ 40,000  $ 59,999 10.9 16.8 $ 60,000 and over 13.5 18.9 Poverty Below Poverty Level 4.6 0.003 9.9 0.005 At or Above Poverty Level 9.8 17.0 a Chi square test of association between Ease of Recruitment and Reported Housing Characteristics. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT October 31, 2002 7 9 Table 7.3 shows that poorer households were much less likely to have an initial refusal, and required fewer attempts to obtain a completed screener. This is consistent with earlier analysis showing higher response rates for lower income households. It could be that the monetary incentive was more effective among lower income households in improving response rates, or that higher income HUs were more difficult to contact.

Table 7.3 also shows that households with LBP, significantly deteriorated LBP, significant LBP hazard, or soil lead hazard were just as likely to require more than three attempts to complete the screener as those without these lead characteristics. While households with LBP or soil hazards were just as likely to initially refuse as other households, those with significantly deteriorated LBP or LBP hazards were significantly more likely to initially refuse than those without these characteristics. This could be due to the fact that more lower income homes participated in the survey and lower income homes are more likely to have these characteristics.

The nonresponse analysis shows that the households that responded were more likely to be located in densely Hispanic and low income areas, and to be renters as opposed to home owners. They are also more likely to live in newer housing ( post 1977).

If the initial refusals who agreed to cooperate are representative of nonrespondents, there would be a potential for bias in unweighted estimated prevalence of HUs with deteriorated LBP or LBP hazards. This means that there would be a potential for bias in the estimated prevalence of HUs with an LBP hazard. However, this was partially corrected by using race/ ethnicity, low income indicators, and building age in making nonresponse adjustments to the HU weights. The weighting adjustments do not eliminate nonresponse bias completely, but they do reduce it when variables that are correlated with both the response rates and propensity to have a lead hazard are used in the nonresponse adjustments.

Comparison of the nonresponse adjusted and poststratified weighted distribution of housing from the National Survey with the AHS and CPS in Table 2.1 show that the weighted National Survey sample matches the national housing distribution closely. These results suggest that there is probably not a serious nonresponse bias in the weighted estimates of lead hazard prevalence.

7.2.3 Completion Rates in the Play Area Subsample In the play area subsample, 40 of the 75 PSU's were selected and all previously completed homes were selected for revisiting. There were 481 homes in the 40 PSU's. Table 7.4 displays the yield in National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT October 31, 2002 7 10 this subsample. In the play area subsample, 78 percent of the homes were completed, either with the collection of a play area soil sample, or the determination that one was not necessary.

Table 7.4. Completions in Play Area Subsample Result Number of HUs Percent of HUs Complete, no soil sample needed 178 37% Complete, new soil sample collected 197 41% Total completes 375 78% No contact made with respondent 54 11% Refusal 12 2% Demolished 1 0% Vacant 27 6% Other 12 2% Total Housing Units 481 100%

7.3 Quality of Field Data Collection and Analysis Quality assurance was integrated into all components of the study, including a defensible study design, experienced project personnel, utilization of well planned, detailed and tested protocols for all aspects of data collection, thorough study specific training of experienced field staff, electronic sample and data management, and ongoing communication between individuals responsible for each stage of the study.

These procedures are described in detail in Volume II, Chapter 6.

Four types of replicate sampling were conducted to estimate measurement error: replicate XRF testing of one random component per room, replicate dust sampling of one surface per home, replicate soil sampling at a different sample site at every third home, and replicate room sampling at a subset of homes. The analyses utilizing these replicate data and resultant measurement error estimates are presented in Appendix C.

This section summarizes the results of the various activities focussed at ensuring quality of the field data collection and laboratory analysis of the environmental samples. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT October 31, 2002 7 11 7.3.1 Field Data Collection A number of procedures were instituted to ensure quality of the field data collection, including a manual edit of all data and samples by the field team, review by the Field Supervisor upon return of the data to Westat headquarters, and reconciliation of any errors with the field team prior to submission of any samples to the laboratory. In addition, random telephone verification and field team audits were conducted;

dust sample material screens were analyzed; and dust blanks and spike samples and blind soil reference samples were included in the sample stream.

Telephone Verification of Data Collection The Field Director contacted a random subsample of 82 ( 10%) households by telephone to verify the team's activities and conduct and to validate selected information from the data forms. No field problems were identified by this process.

In addition to the random verification process, a number of respondents and potential respondents utilized the toll free phone number, or the HUD phone number, to ask questions, verify the survey, and express concerns. All questions or concerns were answered or addressed by the Field Director or HUD.

Random Field Audits The QA Officer or designee, and HUD and NIEHS representatives, conducted random field audits at 31 households to verify that the protocols were followed and data collection was accurate and complete. In addition to the field audits, the QA Officer conducted 17 telephone audits to ascertain the team members' understanding of the protocols, especially when more than two months had elapsed between assignments. Problems noted during these audits were corrected directly with the individual team members.

In addition, the results of audits were immediately relayed to the Field Office. As appropriate, all field staff were notified by memo of any issues identified with the protocols. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT October 31, 2002 7 12 Lead Dust Wipe Sample Collection

Lead Dust Wipe Materials Screens The purpose of a materials screen was to verify that the various sampling supplies to be used in the field did not have lead contamination. Two screens were prepared and analyzed for every lot of wipe materials and sample tubes before being used in the study. The analyses showed that all material screens had below 1.5 µ g lead. 58

Field Blank Wipes One field blank wipe was prepared for each HU at a specified random sample location where another wipe sample was collected. All field blanks were below 50 µ g lead/ wipe, as specified in HUD Guidelines. Most field blanks ( 98+% of all field blanks) had lead levels below the detection limit for the analytical run ( approximately 3.5 µ g lead/ wipe). Of 15 field blanks with lead values above 3.5 µ g lead/ wipe, only one blank had more than 20 µ g lead/ wipe; this wipe had 43 µ g lead and was collected in a home with elevated window sill and trough lead dust levels. Data from this home were used in the survey since the blank was still below the 50 µ g guideline.

Reference ( Spike) Sample Dust Wipes Reference wipe samples were made in advance of the fieldwork by placing a known quantity of National Institute of Standards and Technology's Standard Reference Material ( NIST SRM) 1579a on the same wipe material used in the study. The reference wipes were labeled like a regular sample so that the laboratory was blinded to fact that these were quality control samples. The Field Office inserted one reference wipe sample with each group of 50 samples before sending samples to the laboratory. A total of 206 reference wipes, ranging from 21 to 516 µ g lead/ wipe, were submitted over the course of the study.

The average reference sample recovery was 96% ( range from 83% to 115%) with a standard deviation of +

5.25 percent. With a few exceptions, all sample recoveries were within the HUD Guidelines acceptable range of 80 to 120 percent. The laboratory was requested to re analyze those batches with values outside acceptable limits. Recoveries were acceptable on the second run ( see Section 6.7 of Volume II) and the second set of data was used for the entire batch of samples.

58 EPA's National Lead Laboratory Accreditation Program ( NLLAP) requires wipes to be used in the field to have less than 5 µ g lead/ wipe. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT October 31, 2002 7 13 Soil Quality Control Samples

Reference Soil Samples Reference soil samples were purchased before the fieldwork began. The Field Office labeled and included one reference sample with each group of samples from every three households ( approximately one sample in ten). A total of 83 soil reference samples were submitted to the laboratory. The average recovery was 104% ( range 84% to 121%) with a standard deviation of + 8.04 percent. Two analytical batches contained a reference sample with a recovery of 121%, exceeding the control limits of 80 to 100 percent. The laboratory was requested to re analyze these batches. Recoveries were acceptable on the second run ( see Section 6.9, Volume II) and the second set of data was used for the entire batch of samples.

Two types of reference soil samples were used: urban soil provided by University of Cincinnati ( 640, 3,132, and 6,090 ppm lead), and NIST SRM 2709 ( San Joacquin soil, 18.9 ppm lead) and SRM 2711 ( Montana soil, 1,162 ppm lead). It is interesting, but not unexpected, that the average recovery of 89% for the NIST Montana soil was lower than the average of 105% for the urban soils. Lead in urban soils tends to be from more leachable sources ( i. e. paint, past automobile emissions, industrial facilities). 59 7.3.2 Laboratory Quality Control Samples Each laboratory provided quality assurance procedures during the selection and qualification process. These approved procedures ( outlined in the National Survey's Protocol and Sample Design Report, June, 1999) were adhered to for all study samples. In general, the laboratories performed instrumental and duplicate quality control analyses, as required by ASTM E 1613 94 and the American Industrial Hygiene Association's Environmental Lead Laboratory Accreditation Program ( ELLAP) Quality Manual and Policies, to ensure that the original calibration solutions were accurate, the instruments were properly zeroed, instrumental drift was not excessive, and carryover between samples did not occur. These included duplicate injections of the same sample, method blanks, and spiked samples at a minimum frequency of five percent of the samples.

59 Personal communication with Sandy Roda, Director, Hematology and Environmental Laboratory, University of Cincinnati. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT October 31, 2002 7 14 7.3.3 Laboratory Selection Quality Assurance The laboratories used for analysis of dust and soil samples, respectively, were recognized by the EPA under its National Lead Laboratory Accreditation Program ( NLLAP) for those analyses throughout the laboratory qualification and performance phases of the National Survey. This recognition provided assurance of the quality of laboratory performance of lead analyses and reporting. In addition,

the laboratories were accredited by the American Industrial Hygiene Association; this accreditation provided a separate assurance of the quality of laboratory management and performance of environmental analyses and reporting.

7.4 Paint Testing Quality Assurance Calibration of the XRF analyzer was performed before and after testing in every home. In no case was the instrument used if the calibration criteria were not met, i. e. the analyzer read 0.0 mg/ m2 on the 0.0 film and between 0.9 and 1.2 mg/ m2 on both the front and back of the 1.0 film. In addition, the average of three readings on the front of the 1.0 film was between 0.9 and 1.2 mg/ m2. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT A 1 October 31, 2002 APPENDIX A Selected Additional Tables and Figures National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT A 2 October 31, 2002 Figure A. 1 Prevalence of Significant LBP Hazards, Soil Lead Threshold at 2,000 ppm and at 1,200 ppm 0 5,000 10,000 15,000 20,000 25,000 30,000 All Occupied Housing Units Midwest West Built 1960 1977 Built Before 1940 Income < $ 30,000/ year African American Household Households with Children < 6 Years Subpopulation of Housing Units Housing Units ( 000) with Significant LBP Hazards 2,000 ppm 1,200 ppm National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT A 3 October 31, 2002 Table A. 1 Prevalence of Housing Units with Significant Lead Based Paint ( LBP) Hazards, by Selected Characteristics, for Alternative Soil Lead Threshold of 2000 ppm HUD Lead Safe Housing Rule: Significant LBP Hazardsa Characteristic All HUs ( 000) b No. of HUs with Significant LBP Hazards ( 000) Percent of HUs with Significant LBP Hazards (%) c HUs in Sample Estimate Lower 95% CId Upper 95% CI Estimate Lower 95% CI Upper 95% CI Total Occupied HUs 95,688 25,517 20,410 30,623 27% 21% 32% 375 Region: Northeast 19,290 8,260 5,904 10,616 43% 31% 55% 95 Midwest 22,083 7,606 5,691 9,521 34% 26% 43% 102 South 35,474 6,082 3,161 9,003 17% 9% 25% 111 West 18,841 3,569 1,003 6,135 19% 5% 33% 67 Construction Year: 1978 1998 29,774 425 0 1,222 1% 0% 4% 88 1960 1977 27,874 2,843 317 5,370 10% 1% 19% 111 1940 1959 20,564 10,501 7,996 13,006 51% 39% 63% 97 Before 1940 17,476 11,747 8,771 14,723 67% 50% 84% 79 Urbanization MSA >= 2 million population 26,814 6,793 4,978 8,609 25% 19% 32% 276 MSA =< 2 million population 45,753 10,232 8,171 12,293 22% 18% 27% 417 Non MSA 23,121 7,001 3,848 10,153 30% 17% 44% 138 One or More Children Under Age 6: All HU ages 16,402 5,652 3,758 7,546 34% 23% 46% 83 HUs built 1978 1998 5,847 364 0 1,127 6% 0% 19% 25 HUs built 1960 1977 5,098 371 0 987 7% 0% 19% 20 HUs built 1940 1959 3,055 2,662 1,554 3,770 87% 51% 123% 22 HUs built before 1940 2,401 2,255 502 4,007 94% 21% 167% 16 Housing Unit Type: Single family 82,651 23,204 17,794 28,614 28% 22% 35% 319 Multi family 13,037 2,313 0 5,143 18% 0% 39% 56 Occupant Status: Owner occupied 62,232 16,013 12,647 19,380 26% 20% 31% 254 Renter occupied 29,074 9,503 5,906 13,100 33% 20% 45% 119 Refusal/ Don't Knowe 381 2 Household Income: Less than $ 30,000/ year 33,830 13,998 8,938 19,057 41% 26% 56% 145 Equal to or more than $ 30,000/ year 56,111 10,060 7,151 12,970 18% 13% 23% 211 Refusal/ Don't Know 5,747 19 One or More Children Under Age 6: All Income Categories 16,402 5,652 3,758 7,546 34% 23% 46% 83 Less than $ 30,000/ year 4,791 1,646 0 3,460 34% 0% 72% 28 Equal to or more than $ 30,000/ year 11,236 4,006 1,797 6,214 36% 16% 55% 52 Refusal/ Don't Know 375 3 National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT A 4 October 31, 2002 Table A. 1 Prevalence of Housing Units with Significant Lead Based Paint ( LBP) Hazards, by Selected Characteristics, for Alternative Soil Lead Threshold of 2000 ppm ( continued)

HUD Lead Safe Housing Rule: Significant LBP Hazardsa Characteristic All HUs ( 000) b No. of HUs with Significant LBP Hazards ( 000) Percent of HUs with Significant LBP Hazards (%) c HUs in Sample Estimate Lower 95% CId Upper 95% CI Estimate Lower 95% CI Upper 95% CI Government Support: Government support 4,809 822 10 1,634 17% 0% 34% 25 No government support 86,070 23,571 19,114 28,028 27% 22% 33% 327 Refusal/ Don't Know 4,809 23 Poverty: In Poverty 13,221 5,053 2,542 7,565 38% 19% 57% 54 Not in Poverty 76,336 18,669 14,396 22,942 24% 19% 30% 300 Refusal/ Don't Know 6,130 21 Race: White 77,005 19,164 14,972 23,356 25% 19% 30% 285 African American 10,365 2,317 665 3,969 22% 6% 38% 45 Otherf 6,571 2,631 0 5,734 40% 0% 87% 35 Refusal/ Don't Know 1,746 10 Ethnicity: Hispanic/ Latino 7,434 3,635 700 6,569 49% 9% 88% 31 Not Hispanic/ Latino 87,008 20,841 16,734 24,948 24% 19% 29% 337 Refusal/ Don't Know 1,246 7 a Significant LBP hazard as defined in text and HUD Lead Safe Housing Rule. b " Housing units" include permanently occupied, noninstitutional housing units in which children are permitted to live. c All percentages are calculated with the " All HUs" column in each row used as the denominator. d CI = 95% confidence interval for the estimated number or percent. e Refusals and " don't know" responses by survey respondents. f " Other" race includes Asian, American Indian or Alaskan Native, Native Hawaiian or other Pacific Islander, and more than one race.

Table A. 2 Prevalence of Significant Lead Based Paint ( LBP) Hazards by Location in the Building, for Alternative Soil Lead Threshold of 2000 ppm HUD Lead Safe Housing Rule: Significant LBP Hazards LBP Hazard Location Number of HUsa ( 000) Percent of HUsb HUs in Sample Estimate Lower 95% CIc Upper 95% CI Percent Lower 95% CI Upper 95% CI Interior only 10,861 6,865 14,857 11% 7% 16% 47 Both Interior and Exterior 7,965 4,891 11,040 8% 5% 12% 39 Exterior only 6,690 3,635 9,745 7% 4% 10% 29 Anywhere 25,517 20,440 30,594 27% 21% 32% 115 No Significant LBP Hazard 70,171 65,094 75,248 73% 68% 79% 260 Total HUs 95,688 100% 375 a " Housing units" include permanently occupied, noninstitutional housing units in which children are permitted to live. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT A 5 October 31, 2002 b All percentages are calculated with total housing units ( 95,688) as the denominator. Percentages may not total 100% due to rounding. c CI = 95% confidence interval for the estimated number or percent.

Table A. 3 Prevalence of Significant Lead Based Paint ( LBP) Hazards in Housing Units with a Child Under 6 Years of Age by Type of Hazard, for Alternative Soil Lead Threshold of 2000 ppm HUD Lead Safe Housing Rule: Significant LBP Hazards Type of Hazard Number of HUsa ( 000) Percent of HUsb (%)

Estimate Lower 95% CIc Upper 95% CI Estimate Lower 95% CI Upper 95% CI Significantly Deteriorated Lead Based Paint All HUs 14,124 10,666 17,582 15% 11% 18% HUs w/ Child Under 6 3,521 1,576 5,467 21% 10% 33% Interior Lead Dust All HUs 16,794 12,169 21,420 18% 13% 22% HUs w/ Child Under 6 3,637 1,636 5,638 22% 10% 34% Lead Contaminated Soil All HUs 5,572 2,487 8,657 6% 3% 9% HUs w/ Child Under 6 1,419 0 3,057 9% 0% 19% Any LBP Hazard All HUs 25,517 20,410 30,623 27% 21% 32% HUs w/ Child Under 6 5,652 3,758 7,546 34% 23% 46%

a " Housing units" include permanently occupied, noninstitutional housing units in which children are permitted to live. b Percentages are calculated with total housing units ( 95,688) or with housing units with a child under age 6 ( 19,577) as the denominator, or as applicable. c CI = 95% confidence interval for the estimated number or percent. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT A 6 October 31, 2002 Table A. 4a Distribution of Single Family Housing Units ( SFHUs) with Deteriorated or Significantly Deteriorated Paint, by Construction Year Deteriorated Paint Construction Year Total SFHUs ( 000) a Number of SFHUs with Deteriorated Paint ( 000) Percent of SFHUs with Deteriorated Paint (%) b Estimate Lower 95% CIc Upper 95% CI Estimate Lower 95% CI Upper 95% CI 1978 1998 26,349 5,231 2,628 7,835 20% 10% 30% 1960 1977 22,657 7,992 5,573 10,410 35% 25% 46% 1940 1959 18,497 11,987 9,643 14,331 65% 52% 77% Before 1940 15,148 11,518 10,049 12,986 76% 66% 86% Total SFHUs 82,651 36,728 27,893 45,562 44% 34% 55%

Significantly Deteriorated Paint Construction Year Total SFHUs ( 000) No. of SFHUs with Significantly Deteriorated Paint ( 000) Percent of SFHUs with Significantly Deteriorated Paint (%)

Estimate Lower 95% CI Upper 95% CI Estimate Lower 95% CI Upper 95% CI 1978 1998 26,349 3,403 1,629 5,176 13% 6% 20% 1960 1977 22,657 6,606 4,291 8,922 29% 19% 39% 1940 1959 18,497 9,426 7,240 11,611 51% 39% 63% Before 1940 15,148 9,365 7,527 11,203 62% 50% 74% Total SFHUs 82,651 28,800 20,686 36,913 35% 25% 45%

a " Single family housing units" include permanently occupied, noninstitutional single family housing units in which children are permitted to live. b Percentages are calculated with total housing units ( 95,688) or with housing units with a child under age 6 ( 19,577) as the denominator, or as applicable. c CI = 95% confidence interval for the estimated number or percent. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT A 7 October 31, 2002 Table A. 4b Distribution of Single Family Housing Units ( SFHUs) with Deteriorated or Significantly Deteriorated Unleaded Paint, by Construction Year Deteriorated Unleaded Paint Construction Year Total SFHUs ( 000) a Number of SFHUs with Deteriorated Unleaded Paint ( 000) Percent of SFHUs with Deteriorated Unleaded Paint (%) b Estimate Lower 95% CIc Upper 95% CI Estimate Lower 95% CI Upper 95% CI 1978 1998 26,349 5,149 2,525 7,773 20% 10% 29% 1960 1977 22,657 7,081 4,873 9,289 31% 22% 41% 1940 1959 18,497 5,748 4,076 7,420 31% 22% 40% Before 1940 15,148 2,824 1,828 3,819 19% 12% 25% Total SFHUs 82,651 20,802 13,303 28,301 25% 16% 34%

Significantly Deteriorated Unleaded Paint Construction Year Total SFHUs ( 000) 2 No. of SFHUs with Significantly Deteriorated Unleaded Paint ( 000) Percent of SFHUs with Significantly Deteriorated Unleaded Paint (%) 1 Estimate Lower 95% CI3 Upper 95% CI Estimate Lower 95% CI Upper 95% CI 1978 1998 26,349 3,320 1,521 5,119 13% 6% 19% 1960 1977 22,657 5,997 3,752 8,241 26% 17% 36% 1940 1959 18,497 4,658 3,107 6,209 25% 17% 34% Before 1940 15,148 2,250 1,274 3,225 15% 8% 21% Total SFHUs 82,651 16,225 9,654 22,795 20% 12% 28%

a " Single family housing units" include permanently occupied, noninstitutional single family housing units in which children are permitted to live. b Percentages are calculated with total housing units ( 95,688) or with housing units with a child under age 6 ( 19,577) as the denominator, or as applicable. c CI = 95% confidence interval for the estimated number or percent. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT A 8 October 31, 2002 Table A. 4c Distribution of Single Family Housing Units ( SFHUs) with Deteriorated and Significantly Deteriorated Lead Based Paint ( LBP) by Construction Year Deteriorated LBP Construction Year Number of SFHUs with Deteriorated LBP ( 000) Percent of SFHUs with Deteriorated LBP (%) 1 Total SFHUs ( 000) 2 Estimate Lower 95% CI3 Upper 95% CI Estimate Lower 95% CI Upper 95% CI 1978 1998 26,349 83 0 238 0% 0% 1% 1960 1977 22,657 910 242 1,579 4% 1% 7% 1940 1959 18,497 6,239 4,319 8,159 34% 23% 44% Before 1940 15,148 8,694 7,107 10,281 57% 47% 68% Total SFHUs 82,651 15,926 11,668 20,257 19% 14% 25%

Significantly Deteriorated LBP Construction Year No. of SFHUs with Significantly Deteriorated LBP ( 000) Percent of SFHUs with Significantly Deteriorated LBP (%) 1 Total SFHUs ( 000) 2 Estimate Lower 95% CI3 Upper 95% CI Estimate Lower 95% CI Upper 95% CI 1978 1998 26,349 83 0 238 0% 0% 1% 1960 1977 22,657 610 97 1,122 3% 0% 5% 1940 1959 18,497 5,002 3,193 6,811 27% 17% 37% Before 1940 15,148 7,115 5,605 8,626 47% 37% 57% Total SFHUs 82,651 12,809 8,894 16,797 15% 11% 20%

a " Single family housing units" include permanently occupied, noninstitutional single family housing units in which children are permitted to live. b Percentages are calculated with total housing units ( 95,688) or with housing units with a child under age 6 ( 19,577) as the denominator, or as applicable. c CI = 95% confidence interval for the estimated number or percent.

Table A. 5 Estimated Number of Housing Units with Lead Based Paint on Windows Number of Housing Units with LBP Windows ( 000)

HU Characteristic Estimate Lower 95% CI Upper 95% CI HUs in Sample All Housing Units 18,222 15,688 20,757 165 Construction Year: 1978 1998 290 0 711 2 1960 1977 2,092 1,251 2,933 20 1940 1959 4,733 3,202 6,264 41 Before 1940 11,108 9,298 12,917 102 Occupied by Children Under Age 6 2,826 1,661 3,991 32 Household in Poverty 3,547 2,324 4,771 36 Household in Poverty, Resident Children Under Age 6 569 169 969 7 National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT A 9 October 31, 2002 Table A. 6 Estimated Number of Windows with Lead Based Paint and in Housing Units with Lead Based Paint on Windows Number of Windows with Lead Based Paint ( Average/ HU) a Number of Painted Windows ( Average/ HU) Total Number of Windows ( Average/ HU)

HU Characteristic Estimate Lower 95% CI Upper 95% CI Estimate Lower 95% CI Upper 95% CI Estimate Lower 95% CI Upper 95% CI All Housing Units 7.7 6.2 9.3 13.9 12.1 15.7 15.0 13.3 16.8 Construction Year: 1978 1998 3.5 0.0 7.9 7.2 3.9 10.4 7.2 3.9 10.4 1960 1977 5.6 3.4 7.8 14.0 8.1 20.0 14.4 8.5 20.3 1940 1959 6.5 4.2 8.7 12.8 10.6 15.0 14.0 12.0 16.1 Before 1940 8.7 6.9 10.6 14.5 12.5 16.5 15.7 13.8 17.7 Occupied by Children Under Age 6 12.7 8.0 17.5 20.4 14.5 26.3 21.8 16.2 27.4 Household in Poverty 4.3 2.7 6.0 7.9 5.9 9.9 9.4 8.1 10.7 Household in Poverty, Resident Children Under Age 6 4.8 0.7 8.8 9.8 7.8 11.9 9.8 7.8 11.9 a Entries are average number of windows per housing units, averaged over the housing units with LBP on windows.

Table A. 7 Distribution of Maximum Soil Sample ( Bare and Covered) Lead Concentrations, All Sampled Locations Bare Soil Lead Number of HUs ( 000) a Percent of HUs (%) b Estimate Lower 95% CIc Upper 95% CI Estimate Lower 95% CI Upper 95% CI GEd0 ppm 93,111 91,090 95,131 97% 95% 99% GE 20 ppm 74,621 68,764 80,478 78% 72% 84% GE 50 ppm 56,266 49,840 62,693 59% 52% 66% GE 200 ppm 29,234 28,240 30,228 31% 30% 32% GE 400 ppm 20,390 17,032 23,748 21% 18% 25% GE 1,200 ppm 11,145 7,580 14,709 12% 8% 15% GE 1,600 ppm 7,426 5,289 9,563 8% 6% 10% GE 2,000 ppm 6,809 4,535 9,084 7% 5% 10% GE 5,000 ppm 2,987 1,548 4,427 3% 2% 5% No Bare Soil 335 0 960 0% 0% 1% No Soil 2,242 330 4,154 2% 0% 4% Missinge 95,688 a " Housing units" include permanently occupied, noninstitutional housing units in which children are permitted to live. b All percentages are calculated with total housing units ( 95,688) as the denominator. c CI = 95% confidence interval for the estimated number or percent. d GE equals " greater than or equal to." e " Missing" means that soil was present, but that no lead value is available ( either the sample was not collected, e. g. due to inaccessibility or respondent refusal, or the laboratory did not submit a value). " No soil" means that there was no soil on the property to sample. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT A 10 October 31, 2002 Table A. 8 Distribution of Maximum Soil Sample ( Bare and Covered) Lead Concentrations by Construction Year, All Sampled Locations Soil Lead Concentration Number of HUs ( 000) a Percent of HUs (%) b Before 1940 1940  1959 1960  1977 1978  1998 Before 1940 1940  1959 1960  1977 1978  1998 GEc 0 ppm 16,328 19,605 27,608 29,569 93% 95% 99% 99% GE 20 ppm 16,328 19,279 25,238 13,776 93% 94% 91% 46% GE 50 ppm 15,820 17,670 14,092 8,684 91% 86% 51% 29% GE 200 ppm 13,314 9,950 4,495 1,476 76% 48% 16% 5% GE 400 ppm 11,613 6,283 2,410 84 67% 31% 9% 0% GE 1,200 ppm 6,536 3,922 686  37% 19% 3% 0% GE 1,600 ppm 4,455 2,284 686  26% 11% 3% 0% GE 2,000 ppm 3,929 2,194 686  23% 11% 3% 0% GE 5,000 ppm 1,891 865 231  11% 4% 1% 0% Missingd 145  190  1% 0% 1% 0% No soil 1,003 939 95 205 6% 5% 0% 1% Total 17,476 20,544 27,893 29,774 100% 100% 100% 100%

a " Housing units" include permanently occupied, noninstitutional housing units in which children are permitted to live. b All percentages are calculated with total housing units of that age as the common denominator. c GE equals " greater than or equal to." d " Missing" means that soil was present, but that no lead value is available ( usually due to inaccessibility or respondent refusal). " No soil" means that there was no soil on the property to sample. APPENDIX B Comparison of Protocols for the HUD 1990 Survey of Lead Based Paint ( LBP) in Housing and the HUD National Survey of Lead and Allergens in Housing National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT B 2 October 31, 2002 Comparison of Protocols for the HUD 1990 Survey of Lead Based Paint ( LBP) in Housing and the HUD National Survey of Lead and Allergens in Housing Area HUD National Survey of Lead Based Paint in Housing HUD National Survey of Lead and Allergens in Housing Types/ numbers of housing units selected for the survey and whose data were available to the TSCA Section 403 risk analysis 284 housing units selected from occupied, permanent, non institutional housing in the 48 coterminous states built prior to 1980 and having the potential for containing children. ( These units were all privately owned. While publicly owned units were also selected for the survey, data for these units are not considered in this summary.) 831 housing units selected in a threestage stratified random sample from occupied, permanent, noninstitutionalized housing having the potential for containing children. 75 primary sampling units ( PSUs).

Breakdown of selected units by year built Pre 1940: 27% 1940 1959: 31% 1960 1979: 42% Post 1979: 0% Pre 1940: 18% 1940 1959: 22% 1960 1977: 29% Post 1977: 31%

Dates of environmental sampling November 1989 to March 1990 August 1998 to February 1999, and from July to August 1999 Selecting rooms for environmental sampling Telephone household interview provided information on rooms. One room was selected for sampling in each of the following strata:

Wet room  rooms containing plumbing ( e. g., kitchen, bathroom, laundry room, utility room)

Dry room  all rooms not classified as wet rooms

Main entryway ( floor dust samples only) Room Inventory Form from the Screening/ Recruiting Questionnaire was used to obtain information on rooms. One room was randomly selected for sampling in each of the following four strata:

Kitchen

Common living area ( e. g., living room, den, family room)

Bedroom in which one or more children aged 17 years or younger regularly slept, or any regularlyoccupied bedroom if no such children lived in the unit ( occasionally, two such bedrooms were selected)

Other random room among the remaining rooms in the housing unit. ( Note: Two rooms were randomly selected from this stratum if the stratum contained at least six rooms.)

Main entry ( floor dust only)

Interior common area ( multi family dwellings, floor dust only)

Method of assigning sampling weights Weights reflect the various stages of sampling. Total of the sampling weights Weights reflect the various stages of sampling. Total of the sampling weights National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT B 3 October 31, 2002 Area HUD National Survey of Lead Based Paint in Housing HUD National Survey of Lead and Allergens in Housing equaled the estimated number of housing units with children under age 7 years ( 13,912,000, as estimated by the 1987 AHS). Total of the sampling weights within a given census region equaled the estimated number of units with children under age 7 years in the census region. within a given census region equals the estimated number of units in the census region.

Method for taking dust samples for lead analysis Blue Nozzle vacuum ( a few wipe samples were also collected). Sampling house dust for lead: basic concepts and literature review. ( 1995). EPA 747 R 95 007. Wipes, collected in accordance with ASTM E1728 95, Practice for the field determination of settled dust samples using wipe sampling methods for lead determination by atomic absorption spectrometry techniques.

Number and location of floor dust samples per room One sample from each selected room ( location not dictated in the protocol) One sample from each selected room, generally taken from the center of the largest open area of the room.

Window sill/ trough dust sampling approach A window was selected within each selected room according to a ranking scheme. Sampling was performed from both the sill and trough of the selected window until enough dust was collected or until the entire sill or trough was vacuumed. Entire sill and trough sampled from a random window in the selected room. Trough definition included sliders.

Number and location of sill and trough dust samples per room One sample from the sill and one sample from the trough of the selected window in the selected wet room and dry room One sample from the sill and one sample from the trough of the selected window in each selected room Method of analyzing dust samples Graphite Furnace Atomic Absorption Spectroscopy ( GFAA) ( with EPA SW 846 digestion method) Flame Atomic Absorption Spectrometry ( FAAS) using NIOSH method 7082 Digestion method: modification of EPA SW 846 Method 3050 or ASTM ES 36 94 ( hot plate digestions utilizing nitric acid and/ or perchloric acid and/ or hydrogen peroxide). Method same as used in proficiency testing within the Environmental Lead Laboratory Accreditation Program ( ELLAP).

Soil sampling approach One composite sample of up to 3 core samples ( the latter two taken within 20 inches of the first), each taken at a depth of 10 cm, was collected at each of the following locations: entryway, drip line, and remote area ( i. e., an area halfway between the unit and its property boundary, or within 25 feet of the unit, whichever was less). Two sides of the unit were selected for soil sampling: the side containing the major entryway ( Wall 1) and a second, randomly selected side ( Wall 2). Samples were collected from the top 0.5 inches of soil at the following three sites:

Main entry  a single sample from Wall 1 National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT B 4 October 31, 2002 Area HUD National Survey of Lead Based Paint in Housing HUD National Survey of Lead and Allergens in Housing

Foundation/ drip line  one sample from each of Walls 1 and 2, each sample being a composite of 3 core subsamples taken within 3 feet of the foundation

Mid yard area  one sample from each of Walls 1 and 2, each sample being a composite of 3 core subsamples taken midway between the drip line and boundary of the housing unit property.

Play Area   one composite sample from bare soil under each unit of fixed play equipment.

Soil samples were collected in accordance with core sampling procedures based on ASTM E1727 95 ( described in the HUD Guidelines and in EPA's Residential Sampling for Lead: Protocols for Leaded Dust and Soil Sampling). Samples were collected from bare soil when possible. If no bare soil existed, samples were collected from covered surfaces if possible.

Method of analyzing soil samples ICP AES ( with SW 846 digestion method) ICP AES using NIOSH method 7082 Digestion method: modification of SW 846 Method 3050 or ASTM ES 36 94 ( hot plate digestions utilizing nitric acid and/ or perchloric acid). Method same as used in proficiency testing within the Environmental Lead Laboratory Accreditation Program ( ELLAP).

Handling dust lead and soil lead measurements below the detection limit As log transformed lead amounts are reported in the database, only positive measurements are represented. No indication is given as to when data may have been truncated due to being below detection limits. The final results as reported by the instrument are recorded in the database ( i. e., not detected results are not censored), along with detection limits.

Method for taking paintlead measurements Spectrum analyzer XRF instrument ( single 60 second spectrum reading measurement using a 40 millicurie cobalt source). Measurements were adjusted to statistically correct for measurement bias. Spectrum analyzer XRF analyzer ( fullperiod readings with a 20 second minimum in accordance with the applicable HUD approved Performance Characteristic Sheet .)

Approach to selecting interior painted Painted surfaces were categorized into the following four strata: The following painted components were measured for lead in each selected room: National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT B 5 October 31, 2002 Area HUD National Survey of Lead Based Paint in Housing HUD National Survey of Lead and Allergens in Housing components for paint lead measurements

Walls/ ceilings/ floors

Metal substrate

Non metal substrate

Other surfaces Five painted components were selected randomly for testing in each of the selected wet and dry rooms, one from each stratum along with a fifth selected randomly from among all strata. In addition, up to two purposive measurements were taken from paint anywhere in the unit that may be suspected to contain lead.

All four major walls

Ceiling

Door of major entryway

Window selected for dust sampling

Baseboard

Floor

Up to two other painted surfaces: Technician choice based on surfaces containing deteriorated paint or friction areas.

Approach to selecting exterior painted components for paint lead measurements Painted surfaces were categorized into the following four strata:

Wall ( randomly selected)

Metal substrate within the selected wall

Non metal substrate within the selected wall

Other surfaces within the selected wall Five painted components were selected randomly for testing from the side of the unit containing the selected wall, one from each stratum along with a fifth selected randomly from among all strata. In addition, up to two purposive measurements were taken from paint anywhere on the exterior of the unit that may be suspected to contain lead. Painted siding was measured for lead levels on each exterior wall. In addition, the following painted components were measured for lead on a random wall:

Miscellaneous trim ( 2 measurements)

Window

Door of major entryway   wall independent.

Porch and railing   wall independent

Up to two other painted surfaces National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT C 1 October 31, 2002 APPENDIX C Correcting for Classification Bias Due to Measurement Error National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT C 2 October 31, 2002 CORRECTING FOR CLASSIFICATION BIAS DUE TO MEASUREMENT ERROR Homes were classified as having LBP and lead hazards based on the XRF readings of paint and the analysis of dust and soil samples. Random variation associated with instrument or laboratory measurement, sample collection, and random selection of sampling locations, can induce a classification bias resulting in a bias in the estimated prevalence of HUs with LBP and lead hazards. In addition, paint and dust measurements were made in a sample of rooms   not all rooms. Under this protocol, it is possible for a home to have LBP or a LBP dust hazard in the unsampled rooms and non lead based paint and/ or no dust lead hazard in the sampled rooms. Such HUs would be incorrectly classified as not having LBP and/ or LBP hazards ( false negatives). For this report, measurement error refers to the combined effect of instrument or laboratory measurement variation, sampling variation, spatial variation, and the incomplete sampling of rooms on the important survey estimates.

The specific procedures, equations, and justification for the measurement error correction are presented in Appendix C of Volume II. The findings for the measurement error analyses for paint, dust,

and soil are discussed below in Sections 7.3.1 through 7.3.3 below. The measurement error adjusted values ( lead loading or concentration) have, to the extent possible, the same distribution as the true lead loading or lead concentration values, without the effect of measurement error. The measurement error corrected values are a weighted average of the observed measurements and predicted values from a regression model. Calculating the weights requires modeling the magnitude of the measurement error variance and the regression error variance. Replicate measurements were used to estimate the measurement error variance.

Note that this analysis used preliminary data from the main survey. The analysis did not include data from the follow on play area survey. In addition, minor revisions or corrections to the data may have been made since the analysis was performed. As a result, summary statistics from the measurement error analysis may not agree with those in other sections of the report. Nevertheless, the effects of measurement error are expected to similar in the preliminary and final data.

C. 1 Measurement Error  Paint XRF Measurements XRF readings to measure paint lead loading were taken on painted surfaces within the sampled rooms and on accessible exterior surfaces on two sides of the building to assess the lead loading in paint. The measurement error adjustment procedures were first applied to the interior XRF readings. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT C 3 October 31, 2002 Because the measurement error adjusted XRF values were very close to the original interior XRF readings,

it was considered unnecessary to apply a measurement error adjustment to the exterior XRF readings.

For the measurement error analysis for paint lead measurements, the objective was to determine the number and percentage of homes with LBP. A surface with LBP is a surface with an average lead loading across the surface of 1.0 mg/ cm2 or greater when tested with an XRF analyzer. The instrument calculates its best internal estimate of the lead loading, which it rounds to the nearest 0.1 mg/ cm2 for display. Therefore, to classify surfaces in an equivalent manner, the error corrected XRF readings were rounded to the nearest tenth unit for classifying surfaces. 60 The classification of surfaces as having or not having LBP is used to classify homes as having or not having LBP.

The measurement error adjustment procedure assumes that the distribution of the true paint lead loading around the average for similar homes and the distribution of the measurement error are normal. This assumption provided a relatively poor description of the XRF readings due to the presence of many zero XRF readings and long tails in the XRF distribution ( the measurement error adjustment results are expected to be sensitive values in the tails of the distribution). As a result, the measurement error adjustment for paint lead loadings should be considered approximate, at best. Additional research into the measurement error of the XRF instrument and the distribution of paint lead loading across components would be required to improve the measurement error adjusted values.

Figure C. 1, which shows a scatter plot of replicate XRF readings, helps to illustrate the distribution of the XRF readings. The original XRF reading is on the horizontal axis and the replicate reading is on the vertical axis. Three situations occur. The first is where both XRF readings are zero ( 72.3 percent of the replicate pairs)  these pairs provide essentially no information about measurement error.

The second case is where one of the two readings is zero ( 12.4 percent of the replicate pairs)  these pairs fall on the axes. Lastly, there is the case where both XRF readings are non zero ( 15.3 percent of the replicate pairs)   these generally fall on the diagonal in Figure C. 1. For these points, the differences between the replicate XRF readings have an approximately normal distribution as assumed by the measurement error correction procedure.

The XRF variation among all surfaces within a home increases with the average XRF reading within the home. This suggests that the measurement error will also increase with the paint lead loading on 60 Rounding to the nearest tenth unit for classifying surfaces is equivalent to classifying a surfaces as having LBP if the average lead loading across the surface is 0.95 or greater. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT C 4 October 31, 2002 a component. Surfaces with lead loading near zero will have relatively precise measurements and we expect that large differences between replicate readings when one reading is zero will be relatively rare.

However, there are many surfaces for which one reading is zero and the other paired reading is relatively large ( may be due to two different parts of a component having very different paint lead loadings). 61 Figure C. 1 Original and Replicate XRF Readings on the Same Component 50 40 30 20 15 10 9 8 7 6 5 4 3 2 1 0  1  2 50 40 30 20 15 10 98 7 6 5 4 3 2 1 0  1  2 Original XRF Reading Replicate XRF Reading Note: The axes use the transformed scale used for analysis ( see Equation 9 in Appendix C, Volume II).

For the measurement error adjustment, homes in which all XRF readings were zero or negative ( 162 HUs) were assumed to have no paint lead. The remaining homes were used in the 61 Whatever the explanation for the pattern in the data, the patterns are not consistent with the assumptions behind the measurement error adjustment. Since no consistent pattern was found that would provide a better model, the measurement error adjustment as described in Appendix C ( Volume II) was applied to the data. The results provide one estimate of the effect of measurement error on the assessment of the number of homes with LBP. However, other assumptions or other modeling approaches may provide very different estimates of the magnitude of the effect of measurement error. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT C 5 October 31, 2002 measurement error analysis. For those homes, the model used to predict paint lead loadings had factors for housing unit ID, room type, year of construction, and interactions of year of construction by substrate,

component, and percent deteriorated paint. A preliminary analysis suggested that the relationship between paint deterioration and XRF reading was not linear. To make the relationship closer to linear, the cube of the percent deterioration was used in the model. A further analysis of the relationship would be necessary to provide a better model.

The regression analysis predicts the approximate median of the interior paint lead loading.

Figure C. 2 shows the relative median paint lead loading estimated from regression, by construction year category and component substrate. Figure C. 3 shows the relative differences in median paint lead loading associated with combinations of construction year and region of the country. Figure C. 4 and 7.5 shows the relative differences in the median paint lead loading versus component type, room type, component condition, metro status, presence of pets, overall home cleanliness, and the number of days the air conditioning was used in the last month. Because the assumptions behind the measurement error analysis provide a poor description of the XRF measurements, the patterns illustrated in Figures 7.2 to 7.5 should be considered suggestive of, rather than descriptive of, patterns in the population. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT C 6 October 31, 2002 Figure C. 2 Predicted Relative Median Paint Lead Loading by Construction Year of the Home and Substrate ( based on regression model)

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 1750 1939 1940 1959 1960 1977 1978 1998 Relative Median Paint Lead Loading, mg/ cm2 ( See text)

Drywall Metal Other Paneling Plaster Wallpaper Wood National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT C 7 October 31, 2002 Figure C. 2 shows that interior paint lead loadings are highest in the oldest homes and lowest in the newest homes. The patterns for paint lead loading on specific substrates also generally decrease with the age of the home. The paint lead loadings are highest on wood surfaces in the oldest homes. For components with drywall, paneling, metal, plaster, wallpaper, and wood substrates, the median paint lead loading is low ( less than 0.05 mg/ cm2) for homes built since 1960. However, median paint lead loading on other substrates ( such as brick, concrete, stone, and vinyl) are higher for homes built in the 1960 to 1977 period.

Figure C. 3 shows that the highest predicted median paint lead loading is found in homes built before 1960 in the northeast US and in homes built before 1940 in the southern US. 62 Figure C. 3 Predicted Relative Median Paint Lead Loading by Construction Year of the Home and Region ( based on regression model)

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 1750 1939 1940 1959 1960 1977 1978 1998 Year of Construction Relative Median Paint Lead Loading, mg/ cm2 ( See text)

Midwest Northeast South West 62 Care should be taken when comparing these data to tables presented in Chapter 4. For example, a home was included in Table 4.1 if any one component had LBP. Values plotted in Figures 7.2 through 7.5 represent the predicted median paint loadings in the home ( i. e., for all components). Thus, while Table 4.1 shows that 53% of homes in the Midwest have LBP, Figure C. 3 shows that the median lead loading for all components is lowest for homes in the Midwest. This could be due to there being fewer components with LBP or the lead content of individual components could be lower in Midwest homes. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT C 8 October 31, 2002 Figure C. 4 shows that higher paint lead loadings are generally found on doors, window jambs and window sashes. There are relatively small but significant differences in the paint lead loading among rooms of different types. After accounting for other factors, paint lead loadings are generally higher in children's bedrooms and in kitchens.

Figure C. 4 Predicted Relative Median Paint Lead Loading by Component Type and Room Type ( based on regression model)

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 Baseboard Ceiling Door jamb Entry door Miscelaneous Wall Window apron Window jamb Window sash Window sill Adult bedroom Bathroom Child bedroom Kitchen Living room Other Relative Median Paint Lead Loading, mg/ cm2 ( See text)

Component Room type National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT C 9 October 31, 2002 Figure C. 5 shows that higher paint lead loadings are generally found on components that were judged to be in fair condition as opposed to intact or poor condition. However, relatively few surfaces were judged to be in fair condition. Small but significant differences were associated with metro status ( lower paint lead loading in non MSAs), presence of pets ( lower in homes with pets), overall cleanliness, and days using air conditioning in the last month.

Figure C. 5 Predicted Relative Median Paint Lead Loading by Component Condition, Metro Status, Presence of Pets, Overall Cleanliness, and Air Condition Use in the Last Month ( based on regression model)

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 Intact Fair Poor Missng MSA> 1M MSA< 1M nonMSA Pets No pets Appears clean Some cleaning No cleaning Unknown zero 1 to 9 10 to 19 20 to 30 31 days Relative Median Paint Lead Loading, mg/ cm2 ( See text)

Component condition Metro status Currently pets Cleanliness Days using AC in last month As part of the exploratory analysis to identify the model for the data, such additional variables as tenure and race were considered and not found to be significant predictors. National Survey of Lead Final Report, Vol. I and Allergens in Housing Analysis of Lead Hazards WESTAT C 10 October 31, 2002 The measurement error adjustment procedure identified approximately 30 percent of the XRF readings as outliers. Outliers are those measurements that are more than 2.5 standard deviations above or below the mean of the non outliers. In this case, the measurement error procedure makes a conservative adjustment. The non outlier data were assumed to have a normal error distribution, however, the distribution of the residuals had a tight distribution in the center and very long tails, inconsistent with the normal distribution assumption. The resulting estimate of the error variance was very small, resulting in almost no estimated effect of measurement error. Using the measurement error procedure in Appendix C ( Volume II), the measurement error adjusted paint lead loadings are essentially equal to the XRF readings.

Additional work would be required to develop a better model for the XRF readings and other assumptions might provide a significantly different assessment of the effects of measurement error.

The tentative results from the measurement error analysis are that the interior XRF readings provide a reasonable measure of the paint lead loading for many surfaces. For the remaining surfaces that look like outliers when judged relative to a normal distribution, the effect of measurement error is difficult to assess. We believe that similar conclusions are likely to apply to exterior surfaces; however, no measurement error adjustment was attempted for the exterior surfaces.