Data Management and Analysis The cross section analyses focused on occurrence at the water system level; i. e., the summary data presented discuss the percentage of public water systems with detections, not the percentage of samples with detections. By normalizing the analytical data to the system level, skewness inherent in the sample data is avoided. System level analysis was used since a PWS with a known contaminant problem usually has to sample more frequently than a PWS that has 4 8 Aldrin/ Dieldrin   February 2003 never detected the contaminant. Obviously, the results of a simple computation of the percentage of samples with detections ( or other statistics) can be skewed by the more frequent sampling results reported by the contaminated site. This level of analysis is conservative. For example, a system need only have a single sample with an analytical result greater than the Minimum Reporting Limit ( MRL), i. e., a detection, to be counted as a system with a result " greater than the MRL."

Also, the data used in the analyses were limited to only those data with confirmed water source and sampling type information. Only standard SDWA compliance samples were used; " special" samples, or " investigation" samples ( investigating a contaminant problem that would bias results), or samples of unknown type were not used in the analyses. Various quality control and review checks were made of the results, including follow up questions to the states providing the data. Many of the most intractable data quality problems encountered occurred with older data. These problematic data were, in some cases, simply eliminated from the analysis. For example, when the number of data with problems were insignificant relative to the total number of observations they were dropped from the analysis ( for further details see Cadmus, 2000).

As indicated above, Massachusetts is included in the 20 state, Round 2 national crosssection Noteworthy for SOCs like aldrin, however, Massachusetts SOC data were problematic. Massachusetts reported Round 2 sample results for SOCs from only 56 PWSs, while reporting VOC results from over 400 different PWSs. Massachusetts SOC data also contained an atypically high percentage of systems with analytical detections when compared to all other states. Through communications with Massachusetts data management staff, it was learned that the state's SOC data were incomplete and that the SDWIS/ FED record for Massachusetts SOC data were also incomplete. For instance, the SDWIS/ FED Round 2 data for Massachusetts indicates 18% of systems reported detections of aldrin. The average percent of systems with detections for all other states was 0.2%. In contrast, Massachusetts data characteristics and quantities for IOCs and VOCs were reasonable and comparable with other states' results. Therefore, Massachusetts was included in the group of 20 SDWIS/ FED Round 2 cross section states with usable data for IOCs and VOCs, but its aldrin ( SOC) data were omitted from the Round 2 cross section occurrence analyses and summaries presented in this report.

Occurrence Analysis To evaluate national contaminant occurrence, a two stage analytical approach has been developed. The first stage of analysis provides a straightforward, conservative, broad evaluation of occurrence of the CCL preliminary regulatory determination priority contaminants as described above. These descriptive statistics are summarized here. Based on the findings of the Stage 1 Analysis, EPA will determine whether more intensive statistical evaluations, the Stage 2 Analysis, may be warranted to generate national probability estimates of contaminant occurrence and exposure for priority contaminants. ( For details on this two stage analytical approach see Cadmus, 2000.)

The summary descriptive statistics presented in Table 4 2 for aldrin are a result of the Stage 1 analysis and include data from Round 2 ( SDWIS/ FED, 1993 to 1997) cross section states 4 9 Aldrin/ Dieldrin   February 2003 ( excluding Massachusetts). Included are the total number of samples, the percent samples with detections, the 99th percentile concentration of all samples, the 99th percentile concentration of samples with detections, and the median concentration of samples with detections. The percentages of PWSs and population served indicate the proportion of PWSs whose analytical results showed a detection( s) of the contaminant ( simple detection, > MRL) at any time during the monitoring period; or a detection( s) greater than half the Health Reference Level ( HRL); or a detection( s) greater than the HRL. The HRL, 0.002 µ g/ L, is a preliminary estimated health effect level used for this analysis.

Aldrin is classified by EPA as a linear carcinogen and would, if regulated, have a MCLG of zero. The value used as the HRL when for the occurrence evaluation was the concentration equivalent to a one in a million risk based on the EPA cancer slope factor.

The 99th percentile concentration is used here as a summary statistic to indicate the upper bound of occurrence values because maximum values can be extreme values ( outliers) that sometimes result from sampling or reporting error. The 99th percentile concentration is presented for both the samples with only detections and all of the samples because the value for the 99th percentile concentration of all samples is below the Minimum Reporting Level ( MRL) ( denoted by "<" in Table 4 2). For the same reason, summary statistics such as the 95th percentile concentration of all samples or the median ( or mean) concentration of all samples are omitted because these also are all "<" values. This is the case because only 0.006% of all samples recorded detections of aldrin in Round 2.

As a simplifying assumption, a value of half the MRL is often used as an estimate of the concentration of a contaminant in samples/ systems whose results are less than the MRL. For a contaminant with relatively low occurrence, such as aldrin in drinking water occurrence databases, the median or mean value of the occurrence using this assumption would be half of the MRL ( 0.5 * MRL). However, for these occurrence data this is not straightforward. For Round 2, states have reported a wide range of values for the MRLs. This is in part related to state data management differences, as well as real differences in analytical methods, laboratories, and other factors.

The situation can cause confusion when examining descriptive statistics for occurrence. For example, most Round 2 states reported non detections simply as zeros resulting in a modal MRL value of zero. By definition the MRL cannot be zero. This is an artifact of state data management systems. Because a simple meaningful summary statistic is not available to describe the various reported MRLs, and to avoid confusion, MRLs are not reported in the summary table ( Table 4 2).

In Table 4 2, national occurrence is estimated by extrapolating the summary statistics for the 20 state cross section ( excluding Massachusetts) to national numbers for systems, and population served by systems, from the Water Industry Baseline Handbook, Second Edition ( USEPA, 2000). From the handbook, the total number of community water systems ( CWSs) plus non transient, non community water systems ( NTNCWSs) is 65,030, and the total population served by CWSs plus NTNCWSs is 213,008,182 persons ( see Table 4 2). To arrive 4 10 Aldrin/ Dieldrin   February 2003 at the national occurrence estimate for a particular cross section, the national estimate for PWSs ( or population served by PWSs) is simply multiplied by the percentage for the given summary statistic ( i. e., the national estimate for the total number of PWSs with detections [ 11] is the product of the percentage of PWSs with detections [ 0.016%] and the national estimate for the total number of PWSs [ 65,030]).

Included in Table 4 2 in addition to the cross section data results are results and national extrapolations from all Round 2 reporting states. The data from the biased states are included because of aldrin's very low occurrence in drinking water samples in all states. For contaminants with very low occurrence, such as aldrin where very few states have detections, any occurrence becomes more important, relatively. For such contaminants, the cross section process can easily miss a state with occurrence that becomes more important. This is the case with aldrin.

Extrapolating only from the cross section states, aldrin's very low occurrence clearly underestimates national occurrence. For example, while data from biased states like Alabama ( reporting 100% detections > HRL, > ½ HRL, and > MRL; see Appendix A) exaggerate occurrence because only systems with detections reported results, their detections are real and need to be accounted for because extrapolations from the cross section states do not predict enough detections in the biased states. Therefore, results from all reporting Round 2 states, including the biased states, are also used here to extrapolate to a national estimate. Using the biased states' data should provide conservative estimates, likely overestimates, of national occurrence for aldrin.

As exemplified by the cross section extrapolations for aldrin and dieldrin, national extrapolations of these Stage 1 analytical results can be problematic, especially for contaminants with very low occurrence, because the State data used for the cross section are not a strict statistical sample. For this reason, the nationally extrapolated estimates of occurrence based on Stage 1 results are not presented in the CCL Federal Register Notice. The presentation in the Federal Register Notice of only the actual results of the cross section analysis maintains a straight forward presentation, and the integrity of the data, for stakeholder review. The nationally extrapolated Stage 1 occurrence values are presented here, however, to provide additional perspective. A more rigorous statistical modeling effort, the Stage 2 analysis, could be conducted on the cross section data ( Cadmus, 2001). The Stage 2 results would be more statistically robust and more suitable to national extrapolation. This approach would provide a probability estimate and would also allow for better quantification of estimation error.

Additional Drinking Water Data from the Corn Belt To augment the SDWA drinking water data analysis described above, and to provide additional coverage of the corn belt states where aldrin use as an agricultural insecticide was historically high, independent analyses of SDWA drinking water data from the states of Iowa, Illinois, and Indiana are reviewed below. The Iowa analysis examined SDWA compliance monitoring data from surface and ground water PWSs for the years 1988 to 1995 ( Hallberg et al., 1996). Illinois and Indiana compliance monitoring data for surface and ground water PWSs were evaluated mostly for the years after 1993, though some earlier data were also included ( USEPA, 4 11 Aldrin/ Dieldrin   February 2003 1999c). The raw water data from Illinois were collected from rural, private supply wells ( Goetsch et al., 1992). Data sources, data quality, and analytical methods for these analyses are described in the respective reports; they were all treated similarly to the data quality reviews for this analysis.

Results Occurrence Estimates The percentages of PWSs with detections are very low ( Table 4 2). The cross section shows only approximately 0.02% of PWSs ( approximately 11 PWSs nationally) experienced detections at any concentration level (> MRL, > ½ HRL, and > HRL), affecting about 0.02% of the population served ( approximately 40,000 to 50,000 people nationally) ( see also Figure 4 2). All of the detections were in systems using ground water. The percentage of PWSs ( or population served) in a given source category ( i. e., ground water) with detections > MRL, > ½ HRL, or > HRL is the same because the estimated HRL is so low that it is lower than the MRL. Hence, any detection reported is also greater than the HRL. While concentrations are low   for the detections the median concentration is 0.58 µ g/ L, and the 99th percentile concentration is 0.69 µ g/ L   these values are greater than the HRL.

As noted above, because of the very low occurrence, the cross section states yield an underestimate. Hence, all data are used, even the biased data, to present a conservative upper bound estimate. Conservative estimates of aldrin occurrence using all of the Round 2 reporting states still show relatively low detection frequencies ( Table 4 2). Approximately 0.2% of PWSs ( estimated at 138 PWSs nationally) experienced detections at any concentration level (> MRL, > ½ HRL, and > HRL), affecting about 0.5% of the population served ( 1,052,000 people nationally). The proportion of surface water PWSs with detections was greater than ground water systems. Again the percentages of PWSs ( or populations served) with detections > MRL, > ½ HRL, or > HRL are the same because of the low HRL. The median concentration of detections is 0.18 µ g/ L, and the 99th percentile concentration is 4.4 µ g/ L.

The Round 2 reporting states and the Round 2 national cross section show a proportionate balance in PWS source waters compared to the national inventory. Nationally, 91% of PWSs use ground water ( and 9% surface waters). Round 2 reporting states and the Round 2 national cross section show 87% use ground water ( and 13% surface waters). The relative populations served are not as comparable. Nationally, about 40% of the population is served by PWSs using ground water ( and 60% by surface water). For the Round 2 cross section, 29% of the cross section population is served by ground water PWSs ( and 71% by surface water). For all Round 2 reporting states, 31% of the population is served by ground water PWSs ( and 69% by surface water). The resultant national extrapolations are not additive as a consequence of these disproportions.

Drinking water data from the corn belt states of Iowa, Indiana, and Illinois also show very low occurrence of aldrin. There were no detections of the pesticide in the Iowa or Indiana SDWA aldrin as well. Only 0.3% of all sampled wells had detections at a reporting limit of 0.004 µ g/ L ( Goetsch et al., 1992). 4 12 Aldrin/ Dieldrin   February 2003 Table 4 2. Summary Occurrence Statistics for Aldrin Frequency Factors 20 State Cross Section1 All Reporting States2 National System & Population Numbers3 Total Number of Samples 31,083 41,565  Percent of Samples with Detections 0.006% 0.132%  99th Percentile Concentration ( all samples) < ( Non detect) < ( Non detect)  Health Reference Level 0.002 µ g/ L 0.002 µ g/ L  Minimum Reporting Level ( MRL) Variable4 Variable4  99th Percentile Concentration of Detections 0.69 µ g/ L 4.40 µ g/ L  Median Concentration of Detections 0.58 µ g/ L 0.18 µ g/ L  Total Number of PWSs 12,165 15,123 65,030 Number of GW PWSs 10,540 13,195 59,440 Number of SW PWSs 1,625 1,928 5,590 Total Population 47,708,156 58,979,361 213,008,182 Population of GW PWSs 14,043,051 18,279,343 85,681,696 Population of SW PWSs 33,665,105 40,700,018 127,326,486 Occurrence by System National Extrapolation5 PWSs with detections (> MRL) 0.016% 0.212% 11 138 Range of Cross Section States 0  0.23% 0  100% N/ A N/ A GW PWSs with detections 0.019% 0.167% 11 99 SW PWSs with detections 0.000% 0.519% 0 29 PWSs > 1/ 2 Health Reference Level ( HRL) 0.016% 0.212% 11 138 Range of Cross Section States 0  0.23% 0  100% N/ A N/ A GW PWSs > 1/ 2 Health Reference Level 0.019% 0.167% 11 99 SW PWSs > 1/ 2 Health Reference Level 0.000% 0.519% 0 29 PWSs > Health Reference Level 0.016% 0.212% 11 138 Range of Cross Section States 0  0.23% 0  100% N/ A N/ A GW PWSs > Health Reference Level 0.019% 0.167% 11 99 SW PWSs > Health Reference Level 0.000% 0.519% 0 29 Occurrence by Population Served PWS Population Served with detections 0.018% 0.494% 39,000 1,052,000 Range of Cross Section States 0  0.35% 0  100% N/ A N/ A GW PWS Population with detections 0.062% 0.414% 53,000 355,000 SW PWS Population with detections 0.000% 0.530% 0 674,000 PWS Population Served > 1/ 2 Health Reference Level 0.018% 0.494% 39,000 1,052,000 Range of Cross Section States 0  0.35% 0  100% N/ A N/ A GW PWS Population > 1/ 2 Health Reference Level 0.062% 0.414% 53,000 355,000 SW PWS Population > 1/ 2 Health Reference Level 0.000% 0.530% 0 674,000 PWS Population Served > Health Reference Level 0.018% 0.494% 39,000 1,052,000 Range of Cross Section States 0  0.35% 0  100% N/ A N/ A GW PWS Population > Health Reference Level 0.062% 0.414% 53,000 355,000 SW PWS Population > Health Reference Level 0.000% 0.530% 0 674,000 1. Summary Results based on data from 20 State Cross Section ( minus Massachusetts), from SDWIS/ FED, UCM ( 1993) Round 2. 2. Summary Results based on data from all reporting states from SDWIS/ FED, UCM ( 1993) Round 2. 3. Total PWS and population numbers are from EPA March 2000 Water Industry Baseline Handbook. 4. See text for discussion. 5. National extrapolations are from the 20 State data using the Baseline Handbook system and population numbers.  PWS = Public Water Systems; GW = Ground Water; SW = Surface Water; MRL = Minimum Reporting Level ( for laboratory analyses); Health Reference Level = Health Reference Level, an estimated health effect level used for preliminary assessment for this review; N/ A = Not Applicable."  The Health Reference Level ( HRL) used for aldrin is 0.002 : g/ L. This is a draft value for working review only.  Total Number of Samples = the total number of analytical records for aldrin.  99th Percentile Concentration = the concentration value of the 99th percentile of either all analytical results or just the detections ( in : g/ L).  Median Concentration of Detections = the median analytical value of all the detections ( analytical results greater than the MRL) ( in : g/ L).  Total Number of PWSs = the total number of public water systems with records for aldrin.  Total Population Served = the total population served by public water systems with records for aldrin.  % PWS with detections, % PWS > ½ Health Reference Level, % PWS > Health Reference Level = percent of the total number of public water systems with at least one analytical result that exceeded the MRL, ½ Health Reference Level, Health Reference Level, respectively.  % PWS Population Served with detections, % PWS Population Served > ½ Health Reference Level, % PWS Population Served > Health Reference Level = percent of the total population served by PWSs with at least one analytical result exceeding the MRL, ½ Health Reference Level, or the Health Reference Level, respectively. 4 13 Aldrin/ Dieldrin   February 2003 Regional Patterns Occurrence results are displayed graphically by state in Figures 4 2 and 4 3 to assess whether any distinct regional patterns of occurrence are present. Thirty four states reported Round 2 data but seven of those states have no data for aldrin ( Figure 4 2). Another 22 states did not detect aldrin. The remaining five states have detected aldrin in drinking water and are generally located either in the southern United States or the Northeast ( Figure 4 2). In contrast to the summary statistical data presented in the previous section, this simple spatial analysis includes the biased Massachusetts data.

The simple spatial analysis presented in Figures 4 2 and 4 3 suggests that special regional analyses are not warranted. The State of Alabama does, however, stand out as having relatively high occurrence for reasons that are unclear. While there is a weak geographic clustering of drinking water detections in a few southern and northeastern states ( including the State of Massachusetts' biased data), this is partly the result of so few states with any detections. Further, use and environmental release information described in Chapter 3 of this report indicates that aldrin detections are more widespread than the drinking water data suggest. Two out of the three TRI states ( Arkansas and Michigan) that reported releases of aldrin into the environment did not report detections of the chemical in PWS sampling. Furthermore, aldrin's widespread presence in the environment is evidenced by detections of the compound in hazardous waste sites in at least 31 states ( at NPL sites), as well as detections in site samples in at least 40 states ( listed in ATSDR's HazDat [ ATSDR, 2000]).

4.1.3 Conclusion Aldrin is an insecticide that was discontinued for all uses in 1987. It combats insects by contact or ingestion, and was used primarily on corn and citrus products, as well as for general crops and timber preservation. In addition, aldrin was used for termite proofing plywood, building boards, and the plastic and rubber coverings of electrical and telecommunication cables ( ATSDR, 1993). In 1972, USEPA cancelled all uses of aldrin except subsurface ground insertion for termite control, dipping of non food plant roots and tops, and moth proofing in closed system manufacturing processes. This cancellation decision was finalized in 1974, and in 1987, the manufacturer voluntarily cancelled all uses ( ATSDR, 1993). 4 14 Aldrin/ Dieldrin   February 2003 Aldrin Detects in All Round 2 States States not in Round 2 No data for Aldrin States with No Detections ( No PWSs > MRL) States with Detections ( Any PWSs > MRL) All States Figure 4 2. States With PWSs With Detections of Aldrin for All States With Data in SDWIS/ FED ( Round 2) 4 15 Aldrin/ Dieldrin   February 2003 * State of Massachusetts is an outlier with 17.86% PWSs > MRL Aldrin Occurrence in Cross section States States not in Cross Section No data for Aldrin 0.00% PWSs > MRL 0.01  1.00% PWSs > MRL > 1.00% PWSs > MRL *

Aldrin Occurrence in Cross section States States not in Cross Section No data for Aldrin 0.00% PWSs > HRL 0.01  1.00% PWSs > HRL > 1.00% PWSs > HRL Figure 4 3. Round 2 Cross Section States With PWSs With Detections of Aldrin ( Any PWSs With Results Greater than the Minimum Reporting Level [ MRL]; Above) and Concentrations Greater than the Health Reference Level ( HRL; Below) 4 16 Aldrin/ Dieldrin   February 2003 Aldrin has been detected at very low frequencies and concentrations in bed sediments sampled during the first round of the USGS NAWQA studies and in ground water in Illinois. It has also been found at ATSDR HazDat and CERCLA NPL sites across the country. Furthermore, releases have been reported through the Toxic Release Inventory ( TRI).

Aldrin has also been detected in PWS samples collected under the Safe Drinking Water Act ( SDWA). Occurrence estimates are very low with only 0.006% of all cross section samples showing detections. Significantly, the values for the 99th percentile and median concentrations of all cross section samples are less than the Minimum Reporting Level ( MRL). For Round 2 cross section samples with detections, the median concentration is 0.58 µ g/ L and the 99th percentile concentration is 0.69 µ g/ L. Systems with detections constitute only 0.02% of Round 2 cross section systems ( an estimate of 11 systems nationally). National estimates for the population served by PWSs with detections are also very low ( 40,000 to 50,000), and are the same for all categories (> MRL, > ½ HRL, > HRL). These estimates constitute less than 0.02% of the national population. Using more conservative estimates of occurrence from all states reporting SDWA Round 2 monitoring data, including states with biased data, 0.2% of the nations PWSs ( approximately 138 systems) and 0.5% of the PWS population served ( 1,052,000 people) may be estimated to have detections > MRL, > ½ HRL, and > HRL.

Additional SDWA compliance data from the corn belt states of Iowa, Indiana, and Illinois examined through independent analyses support the drinking water data analyzed in this report. There were no detections in either surface or ground water PWSs in the states of Iowa and Indiana. Illinois reported detections only from surface water PWSs with 1.8% of surface water systems, and 0.1% of samples, showing detections. The 99th percentile concentration of all samples was below the reporting level and the maximum concentration was 2.4 µ g/ L. Furthermore, in a survey of Illinois rural, private water supply wells aldrin and dealdrin were detected in only 0.3% of all sampled wells. 4 17 Aldrin/ Dieldrin   February 2003 References ATSDR. 2000. Agency for Toxic Substances and Disease Registry. Hazardous Substance Release and Health Effects Database. Available on the Internet at: http:// www. atsdr. cdc. gov/ hazdat. htm. Last modified August 19, 2000.

ATSDR. 1993. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Aldrin/ Dieldrin ( Update). Atlanta: Agency for Toxic Substances and Disease Registry. 184 pp.

Cadmus. 2000. Methods for Estimating Contaminant Occurrence and Exposure in Public Drinking Water Systems in Support of CCL Determinations. Draft report submitted to EPA for review July 25, 2000.

Cadmus. 2001. Occurrence estimation methodology and occurrence findings report for six year regulatory review. Draft report submitted to EPA for review October 5, 2001.

Goetsch, W. D., D. P. McKenna, and T. J. Bicki. 1992. Statewide Survey for Agricultural Chemicals in Rural, Private Water Supply Wells in Illinois. Springfield, IL: Illinois Department of Agriculture, Bureau of Environmental Programs. 4 pp.

Hallberg, G. R., D. G. Riley, J. R. Kantamneni, P. J. Weyer, and R. D. Kelley. 1996. Assessment of Iowa Safe Drinking Water Act Monitoring Data: 1988 1995. Research Report No. 97 1. Iowa City: The University of Iowa Hygienic Laboratory. 132 pp.

Kolpin, D. W., J. E. Barbash, and R. J. Gilliom. 1998. Occurrence of pesticides in shallow groundwater of the United States: initial results from the National Water Quality Assessment Program. Environ. Sci. Technol. 32: 558 566.

Larson, S. J., R. J. Gilliom, and P. D. Capel. 1999. Pesticides in Streams of the United States Initial Results from the National Water Quality Assessment Program. U. S. Geological Survey Water Resources Investigations Report 98 4222. 92 pp. Available on the Internet at: http:// water. wr. usgs. gov/ pnsp/ rep/ wrir984222/.

Leahy, P. P. and T. H. Thompson. 1994. The National Water Quality Assessment Program. U. S. Geological Survey Open File Report 94 70. 4 pp. Available on the Internet at: http:// water. usgs. gov/ nawqa/ NAWQA. OFR94 70. html. Last updated August 23, 2000.

Nowell, L. 1999. National Summary of Organochlorine Detections in Bed Sediment and Tissues for the 1991 NAWQA Study Units. Available on the Internet at: http:// water. wr. usgs. gov/ pnsp/ rep/ bst/. Last updated October 18, 1999.

USEPA. 2001a. Analysis of national occurrence of the 1998 Contaminant Candidate List regulatory determination priority contaminants in public water systems. Office of Water. EPA report 815 D 01 002. 77 pp. 4 18 Aldrin/ Dieldrin   February 2003 USEPA. 2001b. Occurrence of unregulated contaminants in public water systems: An initial assessment. Office of Water. EPA report 815 P 00 001. Office of Water. 50 pp.

USEPA. 2000. U. S. Environmental Protection Agency. Water Industry Baseline Handbook, Second Edition ( Draft). March 17, 2000.

USEPA. 1999a. U. S. Environmental Protection Agency. Suspension of unregulated contaminant monitoring requirements for small public water systems; Final Rule and Proposed Rule. Fed. Reg. 64( 5): 1494  1498. January 8.

USEPA. 1999b. U. S. Environmental Protection Agency. Revisions to the unregulated contaminant monitoring regulation for public water systems; Final Rule. Fed. Reg. 64( 180): 50556 50620. September 17.

USEPA. 1999c. U. S. Environmental Protection Agency. A Review of Contaminant Occurrence in Public Water Systems. EPA Report/ 816 R 99/ 006. Office of Water. 78 pp.

USEPA. 1992. U. S. Environmental Protection Agency. Drinking Water; National Primary Drinking Water Regulations   Synthetic Organic Chemicals and Inorganic Chemicals; National Primary Drinking Water Regulations Implementation. Fed. Reg. 57( 138): 31776 31849. July 17.

USEPA. 1991. U. S. Environmental Protection Agency. National Primary Drinking Water Regulations  Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for Unregulated Contaminants; National Primary Drinking Water Regulations Implementation; National Secondary Drinking Water Regulations; Final Rule. Fed. Reg. 56( 20) 3526 3597.

USEPA. 1987. U. S. Environmental Protection Agency. National Primary Drinking Water Regulations Synthetic Organic Chemicals; Monitoring for Unregulated Contaminants; Final Rule. Fed. Reg. 52( 130): 25720. July 8.

USGS. 2000. U. S. Geological Survey. Pesticides in Stream Sediment and Aquatic Biota. USGS Fact Sheet FS 092 00. 4 pp.

USGS. 1999a. U. S. Geological Survey. The Quality of Our Nation's Waters: Nutrients and Pesticides. U. S. Geological Survey Circular 1225. Reston, VA: United States Geological Survey. 82 pp.

USGS. 1999b. U. S. Geological Survey. Pesticides Analyzed in NAWQA Samples: Use, Chemical Analyses, and Water Quality Criteria. PROVISIONAL DATA  SUBJECT TO REVISION. Available on the Internet at: http:// www. water. wr. usgs. gov/ pnsp/ anstrat. Last modified August 20, 1999. 4 19 Aldrin/ Dieldrin   February 2003 4.2 Dieldrin 4.2.1 Ambient Occurrence To understand the presence of a chemical in the environment, an examination of ambient occurrence is useful. In a drinking water context, ambient water is source water existing in surface waters and aquifers before treatment. The most comprehensive and nationally representative data describing ambient water quality in the United States are being produced through the United States Geological Survey's ( USGS) National Water Quality Assessment ( NAWQA) program. ( NAWQA, however, is a relatively young program and complete national data are not yet available from their entire array of sites across the nation.)

Data Sources and Methods The USGS instituted the NAWQA program in 1991 to examine water quality status and trends in the United States. NAWQA is designed and implemented in such a manner to enable consistency and comparison between representative study basins located around the country, facilitating interpretation of natural and anthropogenic factors affecting water quality ( Leahy and Thompson, 1994).

The NAWQA program consists of 59 significant watersheds and aquifers referred to as " study units." The study units represent approximately two thirds of the overall water usage in the United States and a similar proportion of the population served by public water systems. Approximately one half of the nation's land area is represented ( Leahy and Thompson, 1994).

To facilitate management and make the program cost effective, approximately one third of the study units at a time engage in intensive assessment for a period of 3 to 5 years. This is followed by a period of less intensive research and monitoring that lasts between 5 and 7 years. This way all 59 study units rotate through intensive assessment over a 10 year period ( Leahy and Thompson, 1994). The first round of intensive monitoring ( 1991 to 1996) targeted 20 watersheds. This first group was more heavily slanted toward agricultural basins. A national synthesis of results from these study units focusing on pesticides and nutrients has been compiled and analyzed ( Kolpin et al., 1998; Larson et al., 1999; USGS, 1999).

Dieldrin is an analyte for both surface and ground water NAWQA studies. Two of the first 20 study basins analyzed in the pesticide and nutrient national synthesis reports, the Central Nebraska Basins and the White River Basin in Indiana, are located in the corn belt where dieldrin use was heavy during the 1960s. The method detection limit ( MDL) for dieldrin is 0.001 µ g/ L ( Kolpin et al., 1998), substantively lower than most drinking water monitoring. Additional information on analytical methods used in the NAWQA study units, including method detection limits, are described by Gilliom and others ( in press).

Dieldrin is an organochlorine insecticide. As a group, organochlorines are hydrophobic and resist degradation. Hydrophobic (" water hating") compounds have low water solubilities and strong tendencies to sorb to organic material in sediments and accumulate in the tissue of aquatic biota, where they can persist for long periods of time ( ATSDR, 1993; USGS, 2000). 4 20 Aldrin/ Dieldrin   February 2003 Organochlorines may be present in bed sediments and tissues of aquatic systems even when they are undetectable in the water column using conventional methods ( Nowell, 1999).

To determine their presence in hydrologic systems of the United States, the NAWQA program has investigated organochlorine pesticide detections in bed sediments and biotic tissue, focusing on the organochlorine insecticides that were used heavily in the past ( Nowell, 1999). In addition to its own commercial production and use, dieldrin is a degradation product of aldrin, one of the top three insecticides used for agriculture in the 1960s and widely used to kill termites in structures until the mid 1980s. Given this history, dieldrin was investigated in this study ( Nowell, 1999; USGS, 1999). Sampling was conducted at 591 sites from 1992 to 1995 in the 20 NAWQA study units first intensively assessed. Details regarding sampling techniques and analytical methods are described by Nowell ( 1999).

Data are also available for dieldrin occurrence in surface water in the Mississippi River and six major tributaries draining corn belt states ( Goolsby and Battaglin, 1993). These data are the result of a USGS regional water quality investigation and details regarding sampling and analytical methods are described in the report.

Results NAWQA National Synthesis Detection frequencies and concentrations of dieldrin in ambient surface and ground water are low, especially in ground water, which is the case for insecticides in general ( Table 4 3) ( Kolpin et al., 1998; Miller and Wilber, 1999). However, using a common reporting limit of 0.01 µ g/ L, dieldrin is the most commonly detected insecticide in ground water in these USGS studies. This possibly reflects the historically heavy use of aldrin and dieldrin and clearly indicates dieldrin's environmental persistence ( Kolpin et al., 1998; Miller, 2000). Also, though relatively immobile in water when compared to newer pesticides, dieldrin is one of the most mobile of the older organochlorine pesticides ( USGS, 1999).

Dieldrin detection frequencies are considerably higher in shallow ground water in urban areas when compared to shallow ground water in agricultural areas ( Table 4 3), a likely consequence of the more recent use of aldrin and dieldrin as a termiticide and industrial mothproofing agent until the mid 1980s. Agricultural uses were discontinued in the 1970s. Major aquifers, generally deep, have very low detection frequencies and concentrations of dieldrin. Hydrophobic compounds have high sorption potential and are not very mobile in ground water, making their occurrence in deep aquifers unlikely.

In streams, detection frequencies are higher compared to ground water ( Table 4 3). Dieldrin's chemical characteristics, chiefly its hydrophobicity, make it less likely to be transported to the subsurface with ground water recharge. Instead, dieldrin sorbs easily to sediments and biotic tissues and may persist in surface water environments for many years after applications have ceased. Differences in detection frequencies and concentrations between urban and agricultural settings are less pronounced for streams than for ground water, but frequencies and concentrations are greater for streams in agricultural settings. 4 21 Aldrin/ Dieldrin   February 2003 The concentrations and detection frequencies of dieldrin in bed sediments and biotic tissues are considerably higher than water, although the median concentration of all samples is still below the MDL ( Table 4 4). Occurrence of dieldrin is highest in whole fish, highlighting the potential for it to bioaccumulate ( Kolpin et al., 1998). The trend of higher concentrations and detection frequencies in urban environments is again apparent when examining dieldrin Table 4 3. Dieldrin Detections and Concentrations in Streams and Ground Water1 Detection Frequency (% Samples $ MDL2) Concentration Percentiles ( All Samples; µ g/ L)

% $ 0.001 µ g/ L % $ 0.01 µ g/ L Median 95th Maximum Streams urban 3.67% 1.83% nd3 nd 0.016 integrator 3.27% 1.63% nd nd 0.015 agricultural 6.90% 3.90% nd 0.007 0.027 all sites 4.64% 2.39% nd nd 0.19 Ground water shallow urban 5.65% 3.32% nd 0.005 0.068 shallow agricultural 0.97% 0.65% nd nd 0.057 major aquifers 0.43% 0.21% nd nd 0.03 all sites 1.42% 0.93% nd nd 0.068 1 USGS, 1998.

2 MDL for dieldrin in water studies: 0.001 µ g/ L.

3 Not detected in concentration greater than MDL. 4 22 Aldrin/ Dieldrin   February 2003 Table 4 4. Dieldrin Detections and Concentrations in Sediments, Whole Fish, and Bivalves ( All Sites) 1 Detection Frequency (% Samples > MDL2) Concentration Percentiles ( All Samples; µ g/ kg Dry Weight)

Medium 95th Maximum sediments 13.7% nd3 2.7 18 whole fish 28.6% nd 31.9 260 bivalves 6.4% nd 6.4 20 1 Nowell, 1999.

2 MDL for dieldrin in sediments: 1 µ g/ kg; dieldrin in whole fish and bivalves: 5 µ g/ kg.

3 Not detected in concentration greater than MDL.

occurrence across various land use settings for sediments and biotic tissues. Urban areas have the highest detections and concentrations. Occurrence in agricultural and mixed land use settings is lower and approximately equivalent. Forest and rangeland show very low occurrence. The occurrence of a toxic compound in stream sediments is pertinent to drinking water concerns because some desorption of the compound from sediments into water will occur through equilibrium reactions, although in very low concentrations.

While concentrations in water are generally low, a risk specific dose ( RSD) criteria of 0.02 µ g/ L, a concentration associated with a cancer risk level of 1 in 100,000 people, was exceeded at least at 1 site in both surface and ground water ( Kolpin et al., 1998; Larson et al., 1999; USGS, 1998).

Water Quality Investigations from the Corn Belt A USGS regional water quality investigation provides additional information on the occurrence of dieldrin in the corn belt. For surface water sampling from April 1991 to March 1992 from the Mississippi River and six tributaries draining the corn belt, 8% of all samples and 71% of sites had detections greater than the reporting limit of 0.02 µ g/ L. The maximum concentration was approximately 0.03 µ g/ L ( Goolsby and Battaglin, 1993).

4.2.2 Drinking Water Occurrence The Safe Drinking Water Act ( SDWA), as amended in 1986, required Public Water Systems ( PWSs) to monitor for specified " unregulated" contaminants, conduct monitoring on a 5 year cycle, and report the monitoring results to the states. Unregulated contaminants do not have an established or proposed National Primary Drinking Water Regulation ( NPDWR), but they are contaminants that were formally listed and required for monitoring under federal regulations. The intent was to gather scientific information on the occurrence of these 4 23 Aldrin/ Dieldrin   February 2003 contaminants to enable a decision as to whether or not regulations were needed. All nonpurchased community water systems ( CWSs) and non purchased non transient non community water systems ( NTNCWSs), with greater than 150 service connections, were required to conduct this unregulated contaminant monitoring. Smaller systems were not required to conduct this monitoring under federal regulations, but were required to be available to monitor if the state decided such monitoring was necessary. Many states collected data from smaller systems. Additional contaminants were added to the Unregulated Contaminant Monitoring ( UCM) program in 1991 ( USEPA, 1991) for required monitoring that began in 1993 ( USEPA, 1992).

Dieldrin has been monitored under the SDWA Unregulated Contaminant Monitoring ( UCM) program since 1993 ( USEPA, 1992). Monitoring ceased for small public water systems ( PWSs) under a direct final rule published January 8, 1999 ( USEPA, 1999a), and ended for large PWSs with promulgation of the new Unregulated Contaminant Monitoring Regulation ( UCMR) issued September 17, 1999 ( USEPA, 1999b) and effective January 1, 2001. At the time the UCMR lists were developed, the Agency concluded there were adequate monitoring data for a regulatory determination. This obviated the need for continued monitoring under the new UCMR list.

Data Sources, Data Quality, and Analytical Methods Currently, there is no complete national record of unregulated or regulated contaminants in drinking water from PWSs collected under SDWA. Many states have submitted unregulated contaminant PWS monitoring data to EPA databases, but there are issues of data quality, completeness, and representativeness. Nonetheless, a significant amount of state data are available for UCM contaminants that can provide estimates of national occurrence.

The National Contaminant Occurrence Database ( NCOD) is an interface to the actual occurrence data stored in the Safe Drinking Water Information System ( Federal version; SDWIS/ FED) and can be queried to provide a summary of the data in SDWIS/ FED for a particular contaminant. The drinking water occurrence data for dieldrin presented here were derived from monitoring data available in the SDWIS/ FED database.

The data in this report have been reviewed, edited, and filtered to meet various data quality objectives for the purposes of this analysis. Hence, not all data from a particular source were used, only data meeting the quality objectives described below were included. The sources of these data, their quality and national aggregation, and the analytical methods used to estimate a given contaminant's national occurrence ( from these data) are discussed in this section ( for further details see USEPA [ 2001a, b]).

UCM Rounds 1 and 2 The 1987 UCM contaminants include 34 volatile organic compounds ( VOCs) ( USEPA, 1987). Dieldrin, a synthetic organic compound ( SOC), was not among these contaminants. The UCM ( 1987) contaminants were first monitored coincident with the Phase I regulated contaminants, during the 1988 to 1992 period. This period is often referred to as " Round 1" monitoring. The monitoring data collected by the PWSs were reported to the states ( as primacy 4 24 Aldrin/ Dieldrin   February 2003 agents), but there was no protocol in place to report these data to EPA. These data from Round 1 were collected by EPA from many states over time and put into a database called the Unregulated Contaminant Information System, or URCIS.

The 1993 UCM contaminants include 13 SOCs and 1 inorganic contaminant ( IOC) ( USEPA, 1991). Monitoring for the UCM ( 1993) contaminants began coincident with the Phase II/ V regulated contaminants in 1993 through 1998. This is often referred to as " Round 2" monitoring. The UCM ( 1987) contaminants were also included in the Round 2 monitoring. As with other monitoring data, PWSs reported these results to the states. EPA, during the past several years, requested that the states submit these historic data to EPA, and they are now stored in the SDWIS/ FED database.

Monitoring and data collection for dieldrin, a UCM ( 1993) contaminant, began in Round 2. Therefore, the following discussion regarding data quality screening, data management, and analytical methods focuses on SDWIS/ FED. Discussion of the URCIS database is included where relevant, but it is worth noting that the various quality screening, data management, and analytical processes were nearly identical for the two databases. For further details on the two monitoring periods as well as the databases see USEPA ( 2000a, b).

Developing a Nationally Representative Perspective The Round 2 data contain contaminant occurrence data from a total of 35 primacy entities ( including 34 states and data for some tribal systems). However, data from some states are incomplete and biased. Furthermore, the national representativeness of the data is problematic because the data were not collected in a systematic or random statistical framework. These state data could be heavily skewed to low occurrence or high occurrence settings. Hence, the state data were evaluated based on pollution potential indicators and the spatial/ hydrologic diversity of the nation. This evaluation enabled the construction of a cross section from the available state data sets that provides a reasonable representation of national occurrence.

A national cross section from these state Round 2 contaminant databases was established using the approach developed for the EPA report A Review of Contaminant Occurrence in Public Water Systems ( USEPA, 1999c). This approach was developed to support occurrence analyses for EPA's Chemical Monitoring Reform ( CMR) evaluation. It was supported by peer reviewers and stakeholders. The approach cannot provide a " statistically representative" sample because the original monitoring data were not collected or reported in an appropriate fashion. However, the resultant " national cross section" of states should provide a clear indication of the central tendency of the national data. The remainder of this section provides a summary description of how the national cross section for the SDWIS/ FED ( Round 2) database was developed. The details of the approach are presented in other documents ( USEPA, 2001a; USEPA 2001b).

Cross Section Development As a first step in developing the cross section, the state data contained in the SDWIS/ FED database ( that contains the Round 2 monitoring results) were evaluated for completeness and quality. Some state data in SDWIS/ FED were unusable for a variety of 4 25 Aldrin/ Dieldrin   February 2003 reasons. Some states reported only detections, or their data had incorrect units. Datasets only including detections are obviously biased. Other problems included substantially incomplete data sets without all PWSs reporting ( USEPA, 2001a Sections II and III).

The balance of the states remaining after the data quality screening were then examined to establish a national cross section. This step was based on evaluating the states' pollution potential and geographic coverage in relation to all states. Pollution potential is considered to ensure a selection of states that represent the range of likely contaminant occurrence and a balance with regard to likely high and low occurrence. Geographic consideration is included so that the wide range of climatic and hydrogeologic conditions across the United States are represented, again balancing the varied conditions that affect transport and fate of contaminants, as well as conditions that affect naturally occurring contaminants ( USEPA, 2001b Sections III. A. and III. B.).

The cross section states were selected to represent a variety of pollution potential conditions. Two primary pollution potential indicators were used. The first factor selected indicates pollution potential from manufacturing/ population density and serves as an indicator of the potential for VOC contamination within a state. Agriculture was selected as the second pollution potential indicator because the majority of SOCs of concern are pesticides ( USEPA, 2001b Section III. A.). The 50 individual states were ranked from highest to lowest based on the pollution potential indicator data. For example, the state with the highest ranking for pollution potential from manufacturing received a ranking of 1 for this factor and the state with the lowest value was ranked as number 50. States were ranked for their agricultural chemical use status in a similar fashion.

The states' pollution potential rankings for each factor were subdivided into four quartiles ( from highest to lowest pollution potential). The cross section states were chosen from all quartiles for both pollution potential factors to ensure representation, for example, from the following: states with high agrichemical pollution potential rankings and high manufacturing pollution potential rankings; states with high agrichemical pollution potential rankings and low manufacturing pollution potential rankings; states with low agrichemical pollution potential rankings and high manufacturing pollution potential rankings; and states with low agrichemical pollution potential rankings and low manufacturing pollution potential rankings ( USEPA, 2001b Section III. B.). In addition, some secondary pollution potential indicators were considered to further ensure that the cross section states included the spectrum of pollution potential conditions ( high to low). The cross section was then reviewed for geographic coverage throughout all sectors of the United States.

The data quality screening, pollution potential rankings, and geographic coverage analysis established a national cross section of 20 Round 2 ( SDWIS/ FED) states. The cross section states provide good representation of the nation's varied climatic and hydrogeologic regimes and the breadth of pollution potential for the contaminant groups ( Figure 4 4). 4 26 Aldrin/ Dieldrin   February 2003 Cross Section Evaluation To evaluate and validate the method for creating the national cross sections, the method was used to create smaller state subsets from the 24 state, Round 1 ( URCIS) cross section and aggregations. Again, states were chosen to achieve a balance from the quartiles describing pollution potential, and a balanced geographic distribution, to incrementally build subset crosssections of various sizes. For example, the Round 1 cross section was tested with subsets of 4, 8 ( the first 4 state subset plus 4 more states), and 13 ( 8 state subset plus 5) states. Two additional cross sections were included in the analysis for comparison: a cross section composed of 16 biased states eliminated from the 24 state cross section for data quality reasons and a crosssection composed of all 40 Round 1 states ( USEPA, 2001b Section III. B. 1).

These Round 1 incremental cross sections were then used to evaluate occurrence for an array of both high and low occurrence contaminants. The comparative results illustrate several points. The results are quite stable and consistent for the 8, 13, and 24 state cross sections. They are much less so for the 4 state, 16 state ( biased), and 40 state ( all Round 1 states) cross sections. The 4 state cross section is apparently too small to provide balance both geographically and Figure 4 4. Geographic Distribution of Cross Section States for Round 2 ( SDWIS/ FED)

Round 2 ( SDWIS/ FED)

Alaska Arkansas Colorado Kentucky Maine Maryland Massachusetts Michigan Minnesota Missouri New Hampshire New Mexico North Carolina North Dakota Ohio Oklahoma Oregon Rhode Island Texas Washington 4 27 Aldrin/ Dieldrin   February 2003 with pollution potential, a finding that concurs with past work ( USEPA, 1999c). The CMR analysis suggested that a minimum of 6 to 7 states were needed to provide balance both geographically and with pollution potential. The CMR report used 8 states out of the available data for its nationally representative cross section ( USEPA, 1999c). The 16 state and 40 state cross sections, both including biased states, provided occurrence results that were unstable and inconsistent for a variety of reasons associated with their data quality problems ( USEPA, 2001b Section III. B. 1).

The 8, 13, and 24 state cross sections provide very comparable results, are consistent, and are usable as national cross sections to provide estimates of contaminant occurrence. Including greater data from more states improves the national representation and the confidence in the results, as long as the states are balanced related to pollution potential and spatial coverage. The 20 state cross section provides the best, nationally representative cross section for the Round 2 data.

Data Management and Analysis The cross section analyses focused on occurrence at the water system level; i. e., the summary data presented discuss the percentage of public water systems with detections, not the percentage of samples with detections. By normalizing the analytical data to the system level, skewness inherent in the sample data is avoided. System level analysis was used since a PWS with a known contaminant problem usually has to sample more frequently than a PWS that has never detected the contaminant. Obviously, the results of a simple computation of the percentage of samples with detections ( or other statistics) can be skewed by the more frequent sampling results reported by the contaminated site. This level of analysis is conservative. For example, a system need only have a single sample with an analytical result greater than the Minimum Reporting Limit ( MRL), i. e., a detection, to be counted as a system with a result " greater than the MRL."

Also, the data used in the analyses were limited to only those data with confirmed water source and sampling type information. Only standard SDWA compliance samples were used; " special" samples, or " investigation" samples ( investigating a contaminant problem that would bias results), or samples of unknown type were not used in the analyses. Various quality control and review checks were made of the results, including follow up questions to the states providing the data. Many of the most intractable data quality problems encountered occurred with older data. These problematic data were, in some cases, simply eliminated from the analysis. For example, when the number of data with problems were insignificant relative to the total number of observations they were dropped from the analysis ( for further details see Cadmus [ 2000]).

As indicated above, Massachusetts is included in the 20 state, Round 2 national crosssection ( Figure 4 4). However, problematic Massachusetts data for SOCs like dieldrin is noteworthy. Massachusetts reported Round 2 sample results for SOCs from only 56 PWSs, while VOC results were reported from over 400 different PWSs. Massachusetts SOC data also contained an atypically high percentage of systems with analytical detections when compared to all other states. Through communications with Massachusetts data management staff, it was learned that the state's SOC data and the SDWIS/ FED record for Massachusetts SOC data were 4 28 Aldrin/ Dieldrin   February 2003 incomplete. For instance, the SDWIS/ FED Round 2 data for Massachusetts indicates 18% of systems reported detections of dieldrin while the average for all other states was 0.4%. In contrast, Massachusetts data characteristics and quantities for IOCs and VOCs were reasonable and comparable with other states' results. Therefore, Massachusetts was included in the group of 20 SDWIS/ FED Round 2 cross section states with usable data for IOCs and VOCs, but its dieldrin ( SOC) data were omitted from Round 2 cross section occurrence analyses and summaries presented in this report.

Occurrence Analysis To evaluate national contaminant occurrence, a two stage analytical approach has been developed. The first stage of analysis provides a straightforward, conservative, broad evaluation of occurrence of the CCL regulatory determination priority contaminants as described above. These descriptive statistics are summarized here. Based on the findings of the Stage 1 Analysis, EPA will determine whether more intensive statistical evaluations, the Stage 2 Analysis, may be warranted to generate national probability estimates of contaminant occurrence and exposure for priority contaminants. ( For details on this two stage analytical approach see Cadmus [ 2000].)

The summary descriptive statistics presented in Table 4 5 for dieldrin are a result of the Stage 1 analysis and include data from Round 2 ( SDWIS/ FED, 1993 to 1997) cross section states ( minus Massachusetts). Included are the total number of samples, the percent samples with detections, the 99th percentile concentration of all samples, the 99th percentile concentration of samples with detections, and the median concentration of samples with detections. The percentages of PWSs and population served indicate the proportion of PWSs whose analytical results showed a detection( s) of the contaminant ( simple detection, > MRL) at any time during the monitoring period; or a detection( s) greater than half the HRL; or a detection( s) greater than the HRL. The HRL, 0.002 µ g/ L, is a preliminary estimated health effect level used for this analysis.

Dieldrin is classified by EPA as a linear carcinogen and would, if regulated, have a MCLG of zero. The value used as the HRL when for the occurrence evaluation was the concentration equivalent to a one in a million risk based on the EPA cancer slope factor.

The 99th percentile concentration is used here as a summary statistic to indicate the upper bound of occurrence values because maximum values can be extreme values ( outliers) that sometimes result from sampling or reporting error. The 99th percentile concentration is presented for both the samples with only detections and all of the samples because the value for the 99th percentile concentration of all samples is below the Minimum Reporting Level ( MRL) ( denoted by "<" in Table 4 5). For the same reason, summary statistics such as the 95th percentile concentration of all samples or the median ( or mean) concentration of all samples are omitted because these also are all "<" values. This is the case because only 0.064% of all samples recorded detections of dieldrin in Round 2.

As a simplifying assumption, a value of half the MRL is often used as an estimate of the concentration of a contaminant in samples/ systems whose results are less than the MRL. With a relatively low occurrence contaminant such as dieldrin in drinking water occurrence databases, 4 29 Aldrin/ Dieldrin   February 2003 the median or mean value of occurrence using this assumption would be half the MRL ( 0.5 * MRL). However, for these occurrence data this is not straightforward. For Round 2, states have reported a wide range of values for the MRLs. This is in part related to state data management differences, as well as real differences in analytical methods, laboratories, and other factors.

The situation can cause confusion when examining descriptive statistics for occurrence. For example, most Round 2 states reported non detections simply as zeros resulting in a modal MRL value of zero. By definition the MRL cannot be zero. This is an artifact of state data management systems. Because a simple meaningful summary statistic is not available to describe the various reported MRLs, and to avoid confusion, MRLs are not reported in the summary table ( Table 4 5).

In Table 4 5, national occurrence is estimated by extrapolating the summary statistics for the 20 state cross section ( minus Massachusetts) to national numbers for systems, and population served by systems, from the Water Industry Baseline Handbook, Second Edition ( USEPA, 2000). From the handbook, the total number of community water systems ( CWSs) plus non transient, non community water systems ( NTNCWSs) is 65,030 and the total population served by CWSs plus NTNCWSs is 213,008,182 persons ( Table 4 5). To arrive at the national occurrence estimate for the cross section, the national estimate for PWSs ( or population served by PWSs) is simply multiplied by the percentage for the given summary statistic ( i. e., the national estimate for the total number of PWSs with detections, 61, is the product of the percentage of PWSs with detections, 0.093%, and the national estimate for the total number of PWSs, 65,030).

Included in Table 4 5 in addition to the cross section data results are results and national extrapolations from all Round 2 reporting states. The data from the biased states are included because for contaminants with very low occurrence, such as dieldrin where few states have detections, any occurrence becomes more important, relatively. For such contaminants, the cross section process can easily miss a state with occurrence that becomes more important. This is the case with dieldrin.

Extrapolating only from the cross section states, dieldrin's very low occurrence probably underestimates national occurrence. For example, while data from biased states like Alabama ( reporting 100% detections > HRL, > ½ HRL, and > MRL; see Appendix B) exaggerate occurrence because only systems with detections reported results, their detections are real and need to be accounted for because extrapolations from the cross section states do not predict enough detections in the biased states. Therefore, results from all reporting Round 2 states, including the biased states, are also used here to extrapolate a national estimate. Using the biased states' data should provide conservative estimates, likely overestimates, of national occurrence for dieldrin.

Additional Drinking Water Data from the Corn Belt To augment the SDWA drinking water data analysis described above and to provide additional coverage of the corn belt states where dieldrin use as an agricultural insecticide was historically high, independent analyses of SDWA drinking water data from the states of Iowa, 4 30 Aldrin/ Dieldrin   February 2003 Illinois, and Indiana were reviewed. Raw water monitoring data are also included from Illinois community water supply wells.

The Iowa analysis examined SDWA compliance monitoring data from surface and ground water PWSs for the years 1988 to 1995 ( Hallberg et al., 1996). Illinois and Indiana compliance monitoring data for surface and ground water PWSs were evaluated mostly for the years after 1993, though some earlier data were also included ( USEPA, 1999c). The raw water data from Illinois were collected from rural, private supply wells ( Goetsch et al., 1992). Data sources, data quality, and analytical methods for these analyses are described in the respective reports; they were all treated similarly to the data quality reviews for this analysis.

Results Occurrence Estimates The percentages of PWSs with detections are very low ( Table 4 5). The cross section shows approximately 0.1% of PWSs ( about 61 PWSs nationally) experienced detections at any concentration level (> MRL, > ½ HRL, and > HRL), affecting less than 0.1% of the population served ( 150,000 people nationally, see Figure 4 5). The percentage of PWSs ( or population served) in a given source category ( i. e., ground water) with detections > MRL, > ½ HRL, and > HRL is the same because the estimated HRL is so low that it is less than the MRL. Hence, any detection reported is greater than the HRL. Detection frequencies are marginally higher for surface water systems when compared to ground water systems. While concentrations are also low   for samples with detections the median concentration is 0.16 µ g/ L and the 99th percentile concentration is 1.36 µ g/ L   these values are greater than the HRL.

As noted above, because of the very low occurrence, the cross section states yield an underestimate. Hence, all data are used, even the biased data, to present a conservative upper bound estimate. Conservative estimates of dieldrin occurrence using all of the Round 2 reporting states still show relatively low detection frequencies ( Table 4 5). Approximately 0.2% of PWSs ( estimated at 137 PWSs nationally) experienced detections at any concentration level (> MRL, > ½ HRL, and > HRL), affecting about 0.4% of the population served ( 793,000 people nationally). The proportion of surface water PWSs with detections was greater than ground water systems. Again the percentages of PWSs ( or populations served) with detections > MRL, > ½ HRL, or > HRL are the same because of the low HRL. The median concentration of detections is 0.42 µ g/ L and the 99th percentile concentration is 4.4 µ g/ L.

The Round 2 reporting states and the Round 2 national cross section show a proportionate balance in PWS source waters compared to the national inventory. Nationally, 91% of PWSs use ground water ( and 9% surface waters). Round 2 reporting states and the Round 2 national cross section show 88% use ground water ( and 12% surface waters). The relative populations served are not as comparable. Nationally, about 40% of the population is served by PWSs using ground water ( and 60% by surface water). For the Round 2 cross section, 30% of the cross section population is served by ground water PWSs ( and 70% by surface water). For all Round 2 reporting states, 32% of the population is served by ground water PWSs 4 31 Aldrin/ Dieldrin   February 2003 ( and 68% by surface water). The resultant national extrapolations are not additive as a consequence of these disproportions.

Drinking water data from the corn belt states of Iowa, Indiana, and Illinois also show very low occurrence of dieldrin. There were no detections of the pesticide in the Iowa SDWA compliance monitoring data for surface or ground water PWSs ( Hallberg et al., 1996). While Illinois and Indiana also had no detections of the compound in ground water PWSs, it was detected in surface water PWSs in those states ( USEPA, 1999c). Occurrence was low in both states: 1.8% of surface water systems ( 0.1% of samples) showed detections in Illinois; and 2.1% of surface water systems ( 0.3% of samples) showed detections in Indiana. For Illinois and Indiana surface water PWSs, the 99th percentile concentrations of all samples were below the reporting level and the maximum concentrations were 0.1 µ g/ L and 0.04 µ g/ L, respectively ( USEPA, 1999c). Furthermore, in a survey of Illinois rural, private water supply wells only 1.6% of all sampled wells had detections of dieldrin ( Goetsch et al., 1992).

Regional Patterns Occurrence results are displayed graphically by state in Figures 4 5 and 4 6 to assess whether any distinct regional patterns of occurrence are present. Thirty four states reported Round 2 data but seven of those states have no data for dieldrin ( Figure 4 5). Another 19 states did not detect dieldrin. The remaining eight states detected dieldrin in drinking water and are generally located either in the southern United States or the Northeast ( Figure 4 5). In contrast to the summary statistical data presented in the previous section, this simple spatial analysis includes the biased Massachusetts data.

The simple spatial analysis presented in Figures 4 5 and 4 6 suggests that special regional analyses are not warranted. Alabama does, however, stand out as having relatively high occurrence for reasons that are unclear. While there is a weak geographic clustering of drinking water detections in a few southern and northeastern states ( including Massachusetts' biased data), this is partly the result of so few states with any detections. Further, use and environmental release information ( Section 3) and ambient water quality data ( Section <IP_ADDRESS>) indicate that dieldrin detections are more widespread than the drinking water data suggest. Detections of the compound in hazardous waste sites in at least 38 states ( at NPL sites), site samples in at least 40 states ( listed in ATSDR's HazDat [ ATSDR, 2000]), and water, sediment, and biotic tissue quality data from the NAWQA program provide evidence for nationwide occurrence. 4 32 Aldrin/ Dieldrin   February 2003 Table 4 5. Summary Occurrence Statistics for Dieldrin Frequency Factors 20 State Cross Section1 All Reporting States2 National System & Population Numbers3 Total Number of Samples 29,603 40,055  Percent of Samples with Detections 0.064% 0.135%  99th Percentile Concentration ( all samples) < ( Non detect) < ( Non detect)  Health Reference Level 0.002 µ g/ L 0.002 µ g/ L  Minimum Reporting Level ( MRL) Variable4 Variable4  99th Percentile Concentration of Detections 1.36 µ g/ L 4.40 µ g/ L  Median Concentration of Detections 0.16 µ g/ L 0.42 µ g/ L  Total Number of PWSs 11,788 14,725 65,030 Number of GW PWSs 10,329 12,968 59,440 Number of SW PWSs 1,459 1,757 5,590 Total Population 45,784,187 56,909,027 213,008,182 Population of GW PWSs 13,831,864 18,044,000 85,681,696 Population of SW PWSs 31,952,323 38,865,027 127,326,486 Occurrence by System National Extrapolation5 PWSs with detections (> MRL) 0.093% 0.211% 61 137 Range of Cross Section States 0  0.97% 0  100% N/ A N/ A GW PWSs with detections 0.087% 0.177% 52 105 SW PWSs with detections 0.137% 0.455% 8 25 PWSs > 1/ 2 Health Reference Level ( HRL) 0.093% 0.211% 61 137 Range of Cross Section States 0  0.97% 0  100% N/ A N/ A GW PWSs > 1/ 2 Health Reference Level 0.087% 0.177% 52 105 SW PWSs > 1/ 2 Health Reference Level 0.137% 0.455% 8 25 PWSs > Health Reference Level 0.093% 0.211% 61 137 Range of Cross Section States 0  0.97% 0  100% N/ A N/ A GW PWSs > Health Reference Level 0.087% 0.177% 52 105 SW PWSs > Health Reference Level 0.137% 0.455% 8 25 Occurrence by Population Served PWS Population Served with detections 0.070% 0.372% 150,000 793,000 Range of Cross Section States 0  2.00% 0  100% N/ A N/ A GW PWS Population with detections 0.146% 0.371% 125,000 318,000 SW PWS Population with detections 0.038% 0.372% 48,000 474,000 PWS Population Served > 1/ 2 Health Reference Level 0.070% 0.372% 150,000 793,000 Range of Cross Section States 0  2.00% 0  100% N/ A N/ A GW PWS Population > 1/ 2 Health Reference Level 0.146% 0.371% 125,000 318,000 SW PWS Population > 1/ 2 Health Reference Level 0.038% 0.372% 48,000 474,000 PWS Population Served > Health Reference Level 0.070% 0.372% 150,000 793,000 Range of Cross Section States 0  2.00% 0  100% N/ A N/ A GW PWS Population > Health Reference Level 0.146% 0.371% 125,000 318,000 SW PWS Population > Health Reference Level 0.038% 0.372% 48,000 474,000 1. Summary Results based on data from 20 State Cross Section ( minus Massachusetts), from SDWIS/ FED, UCM ( 1993) Round 2. 2. Summary Results based on data from all reporting states from SDWIS/ FED, UCM ( 1993) Round 2; see text for further discussion. 3. Total PWS and population numbers are from EPA March 2000 Water Industry Baseline Handbook. 4. See text for discussion. 5. National extrapolations are from the 20 State data using the Baseline Handbook system and population numbers.  " PWS = Public Water Systems; GW = Ground Water; SW = Surface Water; MRL = Minimum Reporting Level ( for laboratory analyses); Health Reference Level = Health Reference Level, an estimated health effect level used for preliminary assessment for this review; N/ A = Not Applicable."  The Health Reference Level ( HRL) used for dieldrin is 0.002 : g/ L. This is a draft value for working review only.  Total Number of Samples = the total number of analytical records for dieldrin.  99th Percentile Concentration = the concentration value of the 99th percentile of either all analytical results or just the detections ( in : g/ L).  Median Concentration of Detections = the median analytical value of all the detections ( analytical results greater than the MRL) ( in : g/ L).  Total Number of PWSs = the total number of public water systems with records for dieldrin.  Total Population Served = the total population served by public water systems with records for dieldrin.  % PWS with detections, % PWS > ½ Health Reference Level, % PWS > Health Reference Level = percent of the total number of public water systems with at least one analytical result that exceeded the MRL, ½ Health Reference Level, Health Reference Level, respectively.  % PWS Population Served with detections, % PWS Population Served > ½ Health Reference Level, % PWS Population Served > Health Reference Level = percent of the total population served by PWSs with at least one analytical result exceeding the MRL, ½ Health Reference Level, or the Health Reference Level, respectively. 4 33 Aldrin/ Dieldrin   February 2003 Dieldrin Detections in All Round 2 States States not in Round 2 No data for Dieldrin States with No Detections ( No PWSs > MRL) States with Detections ( Any PWSs > MRL) All States Figure 4 5. States With PWSs With Detections of Dieldrin for All States With Data in SDWIS/ FED ( Round 2) 4 34 Aldrin/ Dieldrin   February 2003 * State of Massachusetts is an outlier with 18.18% PWSs > MRL Dieldrin Occurrence in Cross section States States not in Cross Section No data for Dieldrin 0.00% PWSs > MRL 0.01  1.00% PWSs > MRL > 1.00% PWSs > MRL *

Dieldrin Occurrence in Cross section States States not in Cross Section No data for Dieldrin 0.00% PWSs > HRL 0.01  1.00% PWSs > HRL > 1.00% PWSs > HRL Figure 4 6. Round 2 Cross Section States With PWSs With Detections of Dieldrin ( Any PWS With Results Greater than the Minimum Reporting Level [ MRL]; Above) and Concentrations Greater than the Health Reference Level ( HRL; Below) 4 35 Aldrin/ Dieldrin   February 2003 4.2.3 Conclusion Dieldrin is an insecticide that was discontinued for all uses in 1987. It combats insects by contact or ingestion, and was used primarily on corn and citrus products, as well as for general crops and timber preservation. In addition, dieldrin was used for termite proofing plywood, building boards, and the plastic and rubber coverings of electrical and telecommunication cables ( ATSDR, 1993). In 1972, USEPA cancelled all uses of dieldrin except subsurface ground insertion for termite control, dipping of non food plant roots and tops, and moth proofing in closed system manufacturing processes. This cancellation decision was finalized in 1974 and in 1987 the manufacturer voluntarily cancelled all uses ( ATSDR, 1993). Dieldrin is also produced by the environmental degradation of aldrin, an insecticide with similar uses and regulatory history.

Dieldrin has been detected at low frequencies and concentrations in ground and surface water sampled during the first round of the USGS NAWQA studies, and at similar frequencies and concentrations in surface waters of the Mississippi River and major tributaries. Its occurrence is greater in stream bed sediments and biotic tissue. Dieldrin has also been found at ATSDR HazDat and CERCLA NPL sites across the country.

Dieldrin has been detected in PWS samples collected under the SDWA. Occurrence estimates are very low with only 0.06% of all samples showing detections. Significantly, the values for the 99th percentile and median concentrations of all samples are less than the MRL. For Round 2 samples with detections, the median concentration is 0.16 µ g/ L and the 99th percentile concentration is 1.36 µ g/ L. Systems with detections constitute approximately 0.1% of Round 2 systems. National estimates for the population served by PWSs with detections are also low ( 150,000), and are the same for all categories (> MRL, > ½ HRL, > HRL). These estimates are less than 0.1% of the national population. Using more conservative estimates of occurrence from all states reporting SDWA Round 2 monitoring data, including states with biased data, 0.2% of the nations PWSs ( approximately 137 systems) and 0.4% of the PWS population served ( 793,000 people) may be estimated to have detections > MRL, > ½ HRL, and > HRL.

Additional SDWA compliance data from the corn belt states of Iowa, Indiana, and Illinois examined through independent analyses support the drinking water data analyzed in this report. There were no detections in either surface or ground water PWSs in the state of Iowa. Illinois and Indiana reported detections only from surface water PWSs with 1.8% of Illinois' surface water systems ( 0.1% of samples) and 2.1% of Indiana's surface water systems ( 0.3% of samples) showing detections. For Illinois and Indiana surface water PWSs, the 99th percentile concentrations of all samples were below the reporting level and the maximum concentrations were 0.1 µ g/ L and 0.04 µ g/ L, respectively ( USEPA, 1999c). Moreover, in a survey of Illinois rural, private water supply wells dieldrin was detected in only 1.6% of all sampled wells. 4 36 Aldrin/ Dieldrin   February 2003 References ATSDR. 2000. Agency for Toxic Substances and Disease Registry. Hazardous Substance Release and Health Effects Database. Available on the Internet at: http:// www. atsdr. cdc. gov/ hazdat. htm. Last modified August 19, 2000.

ATSDR. 1993. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Aldrin/ Dieldrin ( Update). Atlanta: Agency for Toxic Substances and Disease Registry. 184 pp.

Cadmus. 2000. Methods for Estimating Contaminant Occurrence and Exposure in Public Drinking Water Systems in Support of CCL Determinations. Draft report submitted to EPA for review July 25, 2000.

Cadmus. 2001. Occurrence estimation methodology and occurrence findings report for six year regulatory review. Draft report submitted to EPA for review October 5, 2001.

Gilliom, R. J., D. K. Mueller, and L. H. Nowell. In press. Methods for comparing water quality conditions among National Water Quality Assessment Study Units, 1992 95. U. S. Geological Survey Open File Report 97 589.

Goetsch, W. D., D. P. McKenna, and T. J. Bicki. 1992. Statewide Survey for Agricultural Chemicals in Rural, Private Water Supply Wells in Illinois. Springfield, IL: Illinois Department of Agriculture, Bureau of Environmental Programs. 4 pp.

Goolsby, D. A. and W. A. Battaglin. 1993. Occurrence, distribution and transport of agricultural chemicals in surface waters of the Midwestern United States. In Goolsby, D. A., L. L. Boyer, and G. E. Mallard, compilers. Selected Papers on Agricultural Chemicals in Water Resources of the Midcontinental United States. U. S. Geological Survey Open File Report 94 418. pp. 1 25.

Hallberg, G. R., D. G. Riley, J. R. Kantamneni, P. J. Weyer, and R. D. Kelley. 1996. Assessment of Iowa Safe Drinking Water Act Monitoring Data: 1988 1995. Research Report No. 97 1. Iowa City: The University of Iowa Hygienic Laboratory. 132 pp.

Kolpin, D. W., J. E. Barbash, and R. J. Gilliom. 1998. Occurrence of pesticides in shallow groundwater of the United States: initial results from the National Water Quality Assessment Program. Environ. Sci. Technol. 32: 558 566.

Larson, S. J., R. J. Gilliom, and P. D. Capel. 1999. Pesticides in Streams of the United States Initial Results from the National Water Quality Assessment Program. U. S. Geological Survey Water Resources Investigations Report 98 4222. 92 pp. Available on the Internet at: URL: http:// water. wr. usgs. gov/ pnsp/ rep/ wrir984222/.

Leahy, P. P. and T. H. Thompson. 1994. The National Water Quality Assessment Program. U. S. Geological Survey Open File Report 94 70. 4 pp. Available on the Internet at: http:// water. usgs. gov/ nawqa/ NAWQA. OFR94 70. html Last updated August 23, 2000. 4 37 Aldrin/ Dieldrin   February 2003 Miller, T. 2000. Selected Findings and Current Perspectives on Urban Water Quality The National Water Quality Assessment ( NAWQA) Program of the U. S. Geological Survey. Paper presented to the NAWQA National Liaison Committee, June 13, 2000. 8 pp.

Miller, T. L. and W. G. Wilber. 1999. Emerging Drinking Water Contaminants: Overview and Role of the National Water Quality Assessment Program ( Ch 2.). In: Identifying Future Drinking Water Contaminants. Washington, D. C.: National Academy Press.

Nowell, L. 1999. National Summary of Organochlorine Detections in Bed Sediment and Tissues for the 1991 NAWQA Study Units. Available on the Internet at: http:// water. wr. usgs. gov/ pnsp/ rep/ bst/ Last updated October 18, 1999.

USEPA. 2001a. Analysis of national occurrence of the 1998 Contaminant Candidate List regulatory determination priority contaminants in public water systems. Office of Water. EPA report 815 D 01 002. 77 pp.

USEPA. 2001b. Occurrence of unregulated contaminants in public water systems: An initial assessment. Office of Water. EPA report 815 P 00 001. Office of Water. 50 pp.

USEPA. 2000. U. S. Environmental Protection Agency. Water Industry Baseline Handbook, Second Edition ( Draft). March 17, 2000.

USEPA. 1999a. U. S. Environmental Protection Agency. Suspension of unregulated contaminant monitoring requirements for small public water systems; Final Rule and Proposed Rule. Fed. Reg. 64( 5): 1494 1498. January 8.

USEPA. 1999b. U. S. Environmental Protection Agency. Revisions to the unregulated contaminant monitoring regulation for public water systems; Final Rule. Fed. Reg. 64( 180): 50556  50620. September 17.

USEPA. 1999c. U. S. Environmental Protection Agency. A Review of Contaminant Occurrence in Public Water Systems. EPA Report/ 816 R 99/ 006. Office of Water. 78 pp.

USEPA. 1992. U. S. Environmental Protection Agency. Drinking Water; National Primary Drinking Water Regulations   Synthetic Organic Chemicals and Inorganic Chemicals; National Primary Drinking Water Regulations Implementation. Fed. Reg. 57( 138): 31776  31849. July 17.

USEPA. 1991. National Primary Drinking Water Regulations  Synthetic Organic Chemicals and Inorganic Chemicals; Monitoring for Unregulated Contaminants; National Primary Drinking Water Regulations Implementation; National Secondary Drinking Water Regulations; Final Rule. Fed. Reg. 56( 20) 3526 3597. January 30.

USEPA. 1987. National Primary Drinking Water Regulations Synthetic Organic Chemicals; Monitoring for Unregulated Contaminants; Final Rule. Fed. Reg. 52( 130): 25720. July 8. 4 38 Aldrin/ Dieldrin   February 2003 USGS. 2000. U. S. Geological Survey. Pesticides in Stream Sediment and Aquatic Biota. USGS Fact Sheet FS 092 00. 4 pp.

USGS. 1999. U. S. Geological Survey. The Quality of Our Nation's Waters: Nutrients and Pesticides. U. S. Geological Survey Circular 1225. Reston, VA: United States Geological Survey. 82 pp.

USGS. 1998. U. S. Geological Survey. Pesticides in Surface and Ground Water of the United States: Summary of Results of the National Water Quality Assessment Program ( NAWQA). PROVISIONAL DATA  SUBJECT TO REVISION. Available on the Internet at: http:// water. wr. usgs. gov/ pnsp/ allsum/. Last modified October 9, 1998. 5 1 Aldrin/ Dieldrin   February 2003 5.0 EXPOSURE FROM ENVIRONMENTAL MEDIA OTHER THAN WATER This section summarizes human population exposures to aldrin and dieldrin from food, air, and soil. The primary purpose is to estimate average daily intakes of aldrin and dieldrin by members of the general public. When exposure data on subpopulations were located, such as occupationally exposed persons, these data were summarized and included in this section.

5.1 Exposure from Food Aldrin and dieldrin have been used for pest control on crops such as corn, and citrus products. Aldrin is readily converted to dieldrin, which is persistent in the environment. Although the use of aldrin and dieldrin on crops was cancelled in 1974, soil residues from past uses persist, and may be taken up by crops. Dieldrin additionally bioconcentrates and biomagnifies through terrestrial and aquatic food chains. Thus, the general population may be exposed to aldrin or dieldrin through diet ( ATSDR, 2000).

5.1.1 Exposures of the General Population Concentrations in Non Fish Food Items Aldrin During 1981 through 1992, the U. S. Food and Drug Administration ( FDA) conducted a Market Basket Study to evaluate concentrations of pesticides in 234 different food items. Table 5 1 summarizes aldrin concentrations detected in these foods. Aldrin was detected in 5 food items at concentrations ranging from 0.0009 to 0.002 mg/ kg food. The mean concentration for all positive samples was 0.0016 mg/ kg ( KAN DO Office and Pesticides Team, 1995).

Agriculture and Agri Food Canada ( Neidert and Saschenbrecker, 1996) analyzed 21,982 randomly sampled domestic and imported food and vegetable commodities for pesticide residues between 1992 and 1994. Aldrin was not detected in any domestically produced fruits or vegetables, but was detected in one sample of imported tomatoes at < 0.05 mg/ kg. Aldrin was not detected in any food items during the 1985 survey ( Davies, 1988).

Kannan et al. ( 1994) reviewed data on aldrin and dieldrin residues in food in South and Southeast Asia and in the South Pacific Islands. Aldrin was detected in several food items collected throughout India during the period of 1975 through 1989. Vegetables, oils, and food grains contained < 0.01 to 0.04 mg/ kg, 0.01 to 1.1 mg/ kg, and 0.05 to 0.1 mg/ kg aldrin, respectively.

In 1990, Kannan et al. ( 1994) analyzed food items collected from various metropolitan locations in Australia for organochlorine pesticides. The highest aldrin concentrations were detected in pulses and dairy products at levels of 2.8 × 10 3 and 8.9 × 10 4 mg/ kg wet weight, respectively. Aldrin was also detected in cereals ( 3 × 10 5 mg/ kg), oils ( 1.5 × 10 4 mg/ kg), vegetables ( 0.01 mg/ kg), fruits (< 0.01 mg/ kg), and meat ( 3.0 × 10 4 mg/ kg). 5 2 Aldrin/ Dieldrin   February 2003 Table 5 1. Aldrin and Dieldrin in Domestic Food Items 1981 to 19921 Type of Food Mean Dieldrin Concentrations ( mg/ kg food) and Number of Positive Samples ( N) Mean Aldrin Concentrations ( mg/ kg food) and Number of Positive Samples ( N)

Condiments, Fats, and Sweetners 0.0011 0.005 ( 55)

Dairy 0.0003 0.0061 ( 163)

Desserts 0.0004 0.0048 ( 96) 0.0009 ( 1)

Fruits 0.0005 0.004 ( 21)

Grains 0.0003 0.002 ( 2) 0.002 ( 1)

Infant Food ( strained junior foods in jars) 0.0003 0.0051 ( 36)

Meat, Poultry, Fish and Eggs 0.0005 0.002 ( 195) 0.002 ( 1)

Mixed Foods 0.0006 0.002 ( 49)

Soup 0.0004 0.0008 ( 9) 0.001 ( 1)

Vegetables and Vegetable Products 0.0002 0.0108 ( 210) 0.002 ( 1)

1 Source: KAN DO Office and Pesticides Team, 1995.

Milk samples collected during 1990 through 1991 from 63 metropolitan locations throughout the United States did not contain aldrin residues above the detection limit of 0.0005 ppm ( Trotter and Dickerson, 1993).

During FDA Regulatory Monitoring 1985 1991 ( Yess et al., 1993) of adult foods eaten by infants, 1 of 735 imported orange samples analyzed contained trace levels of aldrin. However, aldrin was not detected in domestic samples of adult food items eaten by infants analyzed in the same FDA Regulatory Monitoring Survey 1985 1991. Infant foods analyzed during FDA Total Diet Study 1985 1991 ( Yess et al., 1993) and Market Basket Survey 1981 1991 ( KAN DO Office and Pesticides Team, 1995) sampling did not contain detectable levels of aldrin. 5 3 Aldrin/ Dieldrin   February 2003 Dieldrin Table 5 1 summarizes dieldrin concentrations in various food items analyzed during 1981 through 1992 as part of the FDA's Market Basket Study ( KAN DO Office and Pesticides Team, 1995). Dieldrin was detected in 117 of 234 different food items at concentrations ranging from 0.0002 to 0.0087 mg/ kg. The mean dieldrin concentration for all positive samples was 0.0015 mg/ kg. The highest dieldrin concentrations were detected in squash ( 0.0087 mg/ kg) and butter ( 0.0061 mg/ kg) samples. Cauliflower ( 0.0002 mg/ kg), soup, canned beets, and red beans ( 0.0004 mg/ kg) had the lowest dieldrin concentrations.

In 1992 and 1994, dieldrin was detected in both domestic and imported food and vegetable commodities analyzed by Agriculture and Agri Food Canada ( Neidert and Saschenbrecker, 1996). Six of the 5,784 domestically produced fruits and vegetables had dieldrin residues ranging from < 0.05 to 0.10 mg/ kg. Of the 16,198 imported fruits and vegetables sampled, 7 had dieldrin levels ranging from < 0.05 to 0.10 mg/ kg. One of the 1,858 imported oranges contained 0.50 mg/ kg dieldrin. A 1985 Canadian study reported higher levels of dieldrin residues in fruits and vegetables, which ranged from 0.11 to 23.0 : g/ kg ( Davies, 1988).

Dieldrin has been detected in various meats. Beef, chicken, lamb, and pork samples bought from butcher shops in Australia during 1990 contained a mean dieldrin concentration of 5.1 × 10 3 mg/ kg wet weight ( Kannan et al., 1994). Levengood et al. ( 1999) analyzed 44 samples of Canadian goose meat collected in northeastern Illinois during 1994 for pesticide residues. Dieldrin was detected in 16% of the baked skinless samples at concentrations ranging from 0.004 to 0.011 mg/ kg, and in 7% of the samples baked with the skin and overlying adipose tissue at concentrations of 0.005 to 0.010 mg/ kg. Dieldrin residue levels reported in this study were below FDA residue limits of 0.30 mg/ kg ( Dey and Manzoor, 1997).

Milk and milk products are additional sources of dieldrin in the diet. During 1990 and 1991, milk samples were collected from 63 metropolitan locations throughout the United States, as part of the EPA's Pasteurized Milk Program. Dieldrin was detected in 21.1% of 806 composited milk samples at concentrations ranging from 0.0005 mg/ kg ( detection limit) to 0.002 mg/ kg ( Trotter and Dickerson, 1993). FDA Total Diet Study results from 1985 through 1991 reported mean dieldrin concentrations in whole milk, 2% milk, evaporated canned milk, and chocolate milk samples of 0.0003 mg/ kg, 0.0003 mg/ kg, 0.0008 mg/ kg, and 0.0014 mg/ kg, respectively ( KAN DO Office and Pesticides Team, 1995). Maximum dieldrin concentrations detected in vitamin D milk and plain milk samples as part of the FDA Regulatory Monitoring were 0.03 mg/ kg and 1 mg/ kg, respectively. The maximum residue found in whole milk ( 1 mg/ kg) was above the EPA milk tolerance of 0.30 ppm ( 0.30 mg/ kg) ( Yess et al., 1993).

Dingle et al. ( 1989) found dieldrin to persist in milk butterfat, with a half life in butter of approximately 9 weeks. Ultra pasteurized heavy cream and cow milk samples purchased in Binghamton, New York, in 1986 had dieldrin levels of 0.006 mg/ kg and 0.003 mg/ kg, respectively ( Schecter et al., 1989). 5 4 Aldrin/ Dieldrin   February 2003 Infant foods analyzed during the FDA's Market Basket Survey from 1981 through 1992 contained mean dieldrin residues ranging from 0.003 to 0.0051 mg/ kg ( KAN DO Office and Pesticides Team, 1995). Maximum dieldrin concentrations detected in infant foods sampled during the 1985 to 1991 sampling period as part of the FDA's Total Diet Study were 0.002 mg/ kg. Adult foods eaten by infants and children also analyzed as part of the FDA Total Diet Study and Regulatory Monitoring programs ( from 1985 through 1991) detected dieldrin in creamy peanut butter, pears, and one imported orange at maximum concentrations of 0.003, 0.0005, and 0.01 mg/ kg, respectively ( Yess et al., 1993).

Because many infants receive human breast milk, their dieldrin intakes may be closely related to its concentration in human breast milk. Current data regarding the levels of dieldrin in human breast milk in the United States were not located. However, data from several older studies are available. Dieldrin was found in the breast milk of 80.8% of 1,436 nursing women sampled in 1980, with a mean fat adjusted residue level of 0.164 mg/ kg ( Savage et al., 1981). Additional studies of nursing mothers in Hawaii ( Takei et al., 1983) and in Mississippi and Arkansas ( Strassman and Kutz, 1977) found dieldrin residues in breast milk at mean concentrations of 1.3 ppb ( 0.0013 mg/ kg) and 4 ppb ( 0.004 mg/ kg), respectively. Breast milk collected from Canadian provinces during 1986 contained an average dieldrin concentration of 4.6 × 10 5 ppm ( 4.6 × 10 5 mg/ kg) ( Mes et al., 1993).

Intake from Non Fish Food Items Aldrin The mean aldrin concentration detected in domestic food items during 1981 to 1992 was 0.0016 mg/ kg ( KAN DO Office and Pesticides Team, 1995). Based on this concentration, a 70 kg adult with a food intake rate of 1.305 kg/ day ( USEPA, 1988) would have an average daily aldrin intake of 3.0 × 10 5 mg/ kg day. At the same concentration, the average daily aldrin intake for a 10 kg child would be 1.3 × 10 4 mg/ kg day, assuming a food intake rate of 0.84 kg/ day ( USEPA, 1988). These intakes are based on the mean aldrin concentrations of positive samples. Food samples where aldrin was not detected are not included in the average. Thus these estimated daily intakes of aldrin from food overestimate the true mean for the general population. ATSDR ( 2000) reports average aldrin intakes to be approximately < 0.001 : g/ kg/ day (< 1.0 × 10 6 mg/ kg day).

Dieldrin Dieldrin was detected more frequently in food items than aldrin. The mean dieldrin concentration in food items analyzed during FDA Market Basket Study 1981 1992 ( KAN DO Office and Pesticides Team, 1995) was 0.0015 : g/ g. Based on this average concentration, a 70 kg adult with a food intake rate of 1.305 kg/ day ( USEPA, 1988) would have an average daily dieldrin intake of 2.8 × 10 5 mg/ kg day. A 10 kg child, with a food intake rate of 0.84 kg/ day ( USEPA, 1988) would have a daily dieldrin intake rate of 1.3 × 10 4 mg/ kg day. These estimates are based on the mean of dieldrin concentrations in positive samples and does not incorporate food samples without detectable levels of dieldrin into the average. Thus, these estimates will overestimate the typical dieldrin intakes experienced by the general population. Additional 5 5 Aldrin/ Dieldrin   February 2003 studies have estimated dietary intakes of dieldrin. MacIntosh et al. ( 1996) estimated daily dieldrin dietary intakes for adults to range from 2 × 10 5 to 4 × 10 3 mg/ day, with a mean of approximately 5 × 10 4 mg/ day. These estimates are based on mean dieldrin concentrations reported for 234 ready to eat food items from the FDA's Total Diet Study during 1986 through 1991 and approximately 117,000 food consumption surveys from the Nurses' Health Study and the Health Professionals/ Follow up Study. Gunderson ( 1988) estimated daily dieldrin intakes for adults to be 7 × 10 6 to 8 × 10 6 mg/ kg day during 1982 to 1984.

Rogan and Ragan ( 1994) estimated a high end average daily intake ( 90th percentile) of dieldrin for infants through breast milk in the United States to be 3.6 × 10 6 mg/ kg day. This estimate is based on dieldrin concentrations in breast milk of 0.10 ppm fat ( Savage et al., 1984), and daily intakes of 700 g of breast milk ( 2.5% fat) per day for 9 months.

Concentrations in Fish and Shellfish Aldrin Two studies were located that reported aldrin concentrations in fish and shellfish. Murray and Beck ( 1990) analyzed shrimp ( Penaeus setiferus and Penaeus aztecus) collected from 30 stations along the Calcasieu River Basin in an industrial area of Louisiana during 1985 to 1986. Aldrin was detected in shrimp samples from 7 of the 30 stations, at concentrations ranging from 0.01 to 0.12 : g/ g ( 0.01 to 0.12 mg/ kg).

In another study, Kannan et al. ( 1994) reported aldrin concentrations for fish and shellfish samples collected from various metropolitan locations in Australia, Papua New Guinea, and the Solomon Islands during 1990. Mean aldrin concentrations were 2.1 × 10 3, 4.5 × 10 4, and 7.7 × 10 4 mg/ kg ( wet weight) for oyster, mudcrab, and fish samples, respectively.

Dieldrin Several studies have reported dieldrin residues in fish and shellfish. Bottom feeding and game fish sampled from 400 sites throughout the United States between 1986 and 1989 as part of the National Study of Chemical Residues in Fish Survey contained mean dieldrin concentrations of 28.1 ng/ g ( 0.0281 mg/ kg). Of the 119 total fish species sampled, the 5 most frequently sampled fish species and their respective dieldrin concentrations were as follows: Carp ( 0.0448 mg/ kg), White Sucker ( 0.0228 mg/ kg) and Channel Catfish ( 0.0154 mg/ kg), Largemouth Bass ( 0.005 mg/ kg), Smallmouth Bass ( 0.00234 mg/ kg), and Walleye ( 0.00373 mg/ kg) ( Kuehl et al., 1994).

Dieldrin concentrations analyzed in 11 species of fish in the Great Lakes ranged from 0.24 to 41.2 ng/ g wet weight ( 0.00024 to 0.041 mg/ kg wet weight). The highest dieldrin concentrations were detected in carp ( 0.040 mg/ kg), trout ( 0.041 mg/ kg), and eel ( 0.031 mg/ kg). Bullhead ( 0.00024 mg/ kg) and perch ( 0.00098 mg/ kg) contained the lowest dieldrin concentrations ( Newsome and Andrews, 1993). Walleye and white bass samples ( skin on) contained mean dieldrin concentrations ranging from 0.006 to 0.009 mg/ kg wet weight and 0.011 mg/ kg wet weight, respectively, in raw samples collected from the Great Lakes during April and 5 6 Aldrin/ Dieldrin   February 2003 July 1991. Pan frying white bass samples ( skin removed) reduced dieldrin concentrations on average by 34.8%. Dieldrin loss from deep fat frying ( skin and muscle) walleye samples was 26.4% ( Zabik et al., 1995).

Fairey et al. ( 1997) measured pesticide concentrations in fish species commonly caught by anglers from 16 areas throughout the San Francisco Bay during 1994. Dieldrin was detected in six of the seven species of fish analyzed. As listed in Table 5 2, dieldrin concentrations in the seven fish species ranged from non detectable to 4.2 ng/ g ( 0.0042 mg/ kg) wet weight. Concentrations were proportional to fish lipid content. White croaker fish samples had the highest dieldrin levels, and also the highest lipid content. Fish species with lower lipid contents ( sharks and halibut) had the lowest dieldrin concentrations.

Blynn et al. ( 1994) analyzed two composited filet samples from three stations in Pennekamp Coral Reef State Park and Key Largo National Marine Sanctuary for pesticide residues during September 1992. None of the filet samples contained dieldrin concentrations above the detection limit of 0.001 mg/ kg.

Shrimp ( Penaeus setiferus and Penaeus aztecus) samples collected from 21 of 30 stations along the Calcasieu River Basin in an industrial area of Louisiana during 1985 to 1986 contained mean dieldrin concentrations of 1.57 : g/ g ( 1.57 mg/ kg). Dieldrin concentrations ranged from 0.05 to 9.47 : g/ g ( 0.05 to 9.47 mg/ kg) ( Murray and Beck, 1990).

Kannan et al. ( 1994) reported dieldrin levels in fish and shellfish samples collected from various metropolitan locations in Australia, Papua New Guinea, and the Solomon Islands during 1990. Mean dieldrin concentrations were 7.3 × 10 4, 3.2 × 10 4, and 9.5 × 10 3 mg/ kg ( wet weight) for oyster, mudcrab, and fish samples, respectively.

Table 5 2. Aldrin Concentrations in San Francisco Bay Area Fish in 19941 Fish Species Dieldrin Concentration Number of Fish Sampled White Croaker 1.1 x 10 3 to 4.2 x 10 3 125 Striped Bass 1.1 x 10 3 to 3.0 x 10 3 16 Shiner Surf Perch ND2 to 2.59 x 10 3 160 Leopard Shark ND to 6.1 x 10 4 14 Brown Smoothhound Shark ND 0.000341 21 Sturgeon 3.1 x 10 3 3 Halibut ND 3 1 Source: Fairley et al. ( 1997).

2 ND: Not Detected ( detection limit not reported). 5 7 Aldrin/ Dieldrin   February 2003 Intake from Fish and Shellfish Aldrin Only one study was located that reported aldrin concentrations in fish and shellfish ( Murray and Beck, 1990). Shrimp samples collected from an industrial area of Louisiana contained aldrin concentrations ranging from 0.01 to 0.12 mg/ kg. Based on these concentrations, and an average daily intake of 20.1 g/ day ( USEPA, 1997), a 70 kg adult would have an average daily intake of 2.9 × 10 6 to 3.5 × 10 5 mg/ kg day. A 10 kg child with a daily intake rate of 4.0 g/ day ( USEPA, 1997) would have a daily aldrin intake of 4.0 × 10 6 to 4.8 × 10 5 mg/ kg day. These intakes are based on aldrin concentrations in fish from an industrial area, which may be higher than typical aldrin levels in fish. Thus, these estimated aldrin intakes may not be representative of general population exposures to aldrin in fish.

Dieldrin Assuming an average concentration of dieldrin in fish of 0.0281 mg/ kg ( Kuehl et al., 1994), and a daily in take of 20.1 g/ day ( USEPA, 1997), a 70 kg adult would have an average dieldrin daily intake of 8.0 × 10 6 mg/ kg day. A 10 kg child exposed to the same concentrations would have a daily dieldrin intake of 1.1 × 10 5, based on a daily intakes of 4.0 g/ day ( USEPA, 1997). Ahmed et al. ( 1993) estimated dietary exposures to dieldrin from American finfish to be 4.9 × 10 7 mg/ kg day, based on FDA surveillance data collected from 1984 to 1988.

5.1.2 Exposures of Subpopulations Persons working with or living in areas utilizing aldrin and dieldrin may potentially have higher concentrations of these pesticides in their diets ( Melnyk et al., 1997).

Concentrations in Food Items Aldrin Additional information on concentrations of aldrin in non fish food items and fish/ shellfish or on intakes of aldrin by subpopulations were not obtained in the available literature.

Dieldrin One study was located that analyzed dieldrin concentrations in the diets of farmers ( Melnyk et al., 1997). Food samples from six farms in Iowa and North Carolina were analyzed during both a pesticide application and non application period as part of a pilot study to evaluate pesticide exposures of farmers and their families. Food and beverage samples at one of the six farms had dieldrin concentrations ranging from 11 to 28 ppb ( 0.011 to 0.028 mg/ kg). Food samples collected during the non application period had higher dieldrin concentrations than those collected during the application period of 28 ppb ( 0.028 mg/ kg) and 15 ppb ( 0.015 mg/ kg), respectively. Dieldrin was not detected in beverages collected during application periods, 5 8 Aldrin/ Dieldrin   February 2003 whereas beverages sampled during the non application period contained 11 ppb ( 0.011 mg/ kg) dieldrin. Previous aldrin use at the farm, the presence of dieldrin in milk ( 0.008 to 0.015 mg/ kg) from area dairy farms ( Bond et al., 1993), and the general persistence of dieldrin in the Midwest ( MacMonegle et al., 1984) may all contribute to the high dieldrin concentrations detected in food items at this farm. Dieldrin was not detected in food and beverage samples from the other five farms in the pilot study. Details on the types of foods ( e. g., fish and non fish food items) analyzed in the pilot study were not provided.

Intake from Food Items Aldrin Additional information on concentrations of aldrin in non fish food items and fish/ shell fish or on intakes of aldrin by subpopulations were not obtained in the available literature. Thus, intakes of aldrin by subpopulations were not calculated.

Dieldrin Melnyk et al. ( 1997) detected dieldrin in food and beverages in the diets of farmers during a pilot study of farms in Iowa and North Carolina. Dieldrin was detected in food items at one of the six farms with a history of aldrin usage analyzed in the study. Mean dieldrin concentrations in food items were 28 ppb ( 0.028 mg/ kg) and 15 ppb ( 0.015 mg/ kg) for nonapplication and application periods, respectively. Based on these concentrations ( 0.015 to 0.028 mg/ kg) and an intake of 1.305 kg/ day ( USEPA, 1988), a 70 kg adult worker would have an average daily dieldrin intake ranging from 2.8 × 10 4 to 5.2 × 10 4 mg/ kg day.

5.2 Exposure from Air Aldrin and dieldrin have both been used for pest control in agriculture and as termiticides. Agricultural uses of aldrin and dieldrin were cancelled in 1974 and their use as a termiticide cancelled in 1987. Aldrin and dieldrin may enter the atmosphere through mechanisms such as spray drift during application, water evaporation, and dispersion and suspension of particulates or soils to which the compounds are absorbed ( ATSDR, 2000).

5.2.1 Exposures of the General Population Concentrations in Air Aldrin Current data on ambient concentrations of aldrin in air were not located in the available literature. However, from 1970 to 1972 Kutz et al. ( 1976) analyzed 2,479 air samples from 16 states. Aldrin was detected in 13.5% of the samples with a mean of 3 × 10 5 ppb ( 4 × 10 7 mg/ m3). Ambient concentrations reported by this study are likely higher than current ambient aldrin levels, as it was conducted prior to the cancellation of all uses of adrin and dieldrin. 5 9 Aldrin/ Dieldrin   February 2003 Several studies have measured indoor air concentrations of aldrin, as the potential for higher exposure rates may occur for segments of the population residing in homes using this chemical for termite control ( Dobbs and Williams, 1983).

A pilot study of non occupational exposures to pesticides for the general population from ambient air inside and outside the home was conducted in nine homes during 1985. Indoor and outdoor air, as well as personal air monitors, were sampled over 24 hour periods. Aldrin was detected in indoor air at six of the nine households; outdoors at four of the nine households; and in three of the nine personal monitors. In one designated high pesticide use household, aldrin was detected in the indoor air at average concentrations of 0.004 ppb ( 5.8 × 10 5 mg/ m3). Neither compound was detected in the outdoor air immediately adjacent to the home and concentrations detected with personal air monitors were half of the concentrations reported for indoor air samples ( Lewis et al., 1988).

Indoor air concentrations of aldrin were monitored on each level of a two story home in Bloomington, Indiana, ( Wallace et al., 1996) identified in a previous study ( Anderson and Hites, 1988) as having elevated concentrations of these chemicals. Aldrin had been poured into the void spaces of the foundation blocks during its construction in 1985 for termite control. Between September 1987 and April 1995, aldrin concentrations had decreased from 5,000 ng/ m3 to 12 ng/ m3 ( 5 × 10 3 to 1.2 × 10 5 mg/ m3) in the basement, and from 300 ng/ m3 to 2 ng/ m3 ( 3 × 10 4 to 2 × 10 6 mg/ m3) in the living area.

Dieldrin Several studies have measured dieldrin in ambient air. Kutz et al. ( 1976) analyzed 2,479 air samples from 16 states from 1970 to 1972. Dieldrin was detected in 94% of samples with a mean of 1 x 10 4 ppb ( 1.6 × 10 6 mg/ m3).

In another study, dieldrin was detected at an average concentration of 5.1 × 10 6 ppb ( 8.0 × 10 8 mg/ m3) in ambient air over College Station, Texas, during 1979 through 1980 ( Atlas and Giam, 1988).

Several studies have measured indoor air concentrations of dieldrin. One study reported dieldrin concentrations in indoor air for homes 1 to 10 years after the termiticide treatment ranging from 0.002 to 0.17 ppb ( 3.16 × 10 5 to 1.98 × 10 3 mg/ m3) in roof voids, and from 0.0006 to 0.03 ppb ( 9.49 × 10 6 to 4.75 × 10 4 mg/ m3) in living rooms, bedrooms, and all interior areas ( Dobbs and Williams, 1983).

A pilot study of non occupational exposures to pesticides for the general population from ambient air inside and outside the home was conducted in nine homes during 1985. Indoor and outdoor air, as well as personal air monitors, were sampled over 24 hour periods. Dieldrin was detected in indoor air at five of the nine households; outdoors at four of the nine households; and by personal monitors for five out of nine individuals. In one designated high pesticide use household, dieldrin was detected in the indoor air at average concentrations of 0.002 ppb ( 3.8 × 10 5 mg/ m3). Neither compound was detected in the outdoor air immediately adjacent to 5 10 Aldrin/ Dieldrin   February 2003 the home and concentrations detected with personal air monitors were one third the concentrations for ambient indoor air ( Lewis et al., 1988).

Indoor air concentrations of dieldrin were monitored on each level of a two story home in Bloomington, Indiana, identified in a previous study ( Anderson and Hites, 1988) as having elevated concentrations of these chemicals. Aldrin had been poured into the void spaces of the foundation blocks during its construction in 1985 for termite control. Between September 1987 and April 1995, dieldrin concentrations fell from 28 ng/ m3 to 20 ng/ m3 ( 2.8 × 10 5 to 2.0 × 10 5 mg/ m3) in the basement, and from 7 ng/ m3 to 3 ng/ m3 ( 7 × 10 6 to 3 × 10 6 mg/ m3) in the living area ( Wallace et al., 1996).

Indoor air samples were collected as part of a pilot study in Raleigh, North Carolina, to characterize pesticide exposures of children. Samples were collected at 2 different heights ( 12.5 cm and 75 cm) from the living rooms of 8 homes, over a 24 hour period. Dieldrin was detected in indoor air samples at four of the eight homes, at a mean concentration of 0.01 : g/ m3 ( 1 × 10 5 mg/ m3), and at a maximum concentration of 0.02 : g/ m3 ( 2 × 10 5 mg/ m3) ( Lewis et al., 1994).

Intake from Air Aldrin Intake of aldrin from air was estimated based on the mean ambient air concentration reported by Kutz et al. ( 1976) from 1970 to 1972 of 4 × 10 7 mg/ m3. Assuming an inhalation rate of 20 m3/ day ( USEPA, 1988), the average estimated daily intake of aldrin for a 70 kg adult would be 1.1 × 10 7 mg/ kg day. The estimated average daily intake of aldrin for a 10 kg child is 6.0 × 10 7 mg/ kg day, based on an inhalation rate of 15 m3/ day ( USEPA, 1988). This ambient concentration of aldrin was measured prior to the cancellation of all uses of aldrin and dieldrin. Thus, these estimated daily intakes of aldrin from air will overestimate general population exposures from air.

Dieldrin The mean dieldrin concentration reported for ambient air from 1970 to 1972 is 1.6 × 10 6 mg/ m3 ( Kutz et al., 1976). Assuming an inhalation rate of 20 m3/ day ( USEPA, 1988), the average estimated daily intake dieldrin for a 70 kg adult would be 4.6 × 10 7 mg/ kg day. The estimated average daily intake of dieldrin in air for a 10 kg child is 2.4 × 10 6 mg/ kg day, based on an inhalation rate of 15 m3/ day ( USEPA, 1988). These estimated daily intakes will overestimate general population exposures to dieldrin from air, as they are based on ambient air concentrations reported prior to the cancellation of all uses of aldrin and dieldrin.

Higher intakes of aldrin and dieldrin may be expected for populations living in homes using these chemicals for termite control ( ATSDR, 2000). 5 11 Aldrin/ Dieldrin   February 2003 5.2.2 Exposures of Subpopulations Persons involved in the manufacturing or application of aldrin or dieldrin may potentially be exposed to these chemicals in air. However, data on workplace or post application concentrations of aldrin or dieldrin in air, or intakes of these chemicals by workers were not available from the retrieved literature.

5.3 Exposure from Soil Aldrin and dieldrin were used as pesticides, until their registrations were cancelled in 1974. Although aldrin was applied more frequently to soils, dieldrin is found more often and in higher concentrations than aldrin residues ( ATSDR, 2000).

5.3.1 Exposures of the General Population Concentrations in Soil Aldrin Data on aldrin in residential soils were not located in the available literature. Based on the rapid conversion of aldrin to dieldrin in soils ( ATSDR, 2000), the general population is more likely to be exposed to dieldrin than aldrin from soil.

Dieldrin The National Soils Monitoring Program ( Kutz et al., 1976) detected dieldrin in soils throughout 24 states at mean concentrations ranging from 1 to 49 ppb ( 0.001 to 0.049 mg/ kg).

Pesticides may accumulate in carpets from indoor treatment and the tracking in of outdoor soils, thus contributing to residential exposures ( Lewis et al., 1994). A composite sample of the dust from four Seattle homes collected during 1988 to 1989 contained 1.1 mg/ kg dieldrin, although none of the homeowners could remember using the pesticide ( Roberts and Camann, 1989).

Lewis et al. ( 1994) analyzed house dust and soil samples from nine homes in North Carolina, varying in pesticide use, as part of a pilot study to evaluate monitoring methods used to assess exposures to children. House dust samples were collected by taking 40 passes over a 3800 cm2 carpet areas of the homes with a HVS3 vacuum system. The mean dieldrin concentration was 0.29 mg/ kg ( 0.12 : g/ m2), with a maximum concentration of 1.0 mg/ kg ( 0.38 : g/ m2). Entryway soil samples, collected from outside the doorway most frequently used, had mean dieldrin concentrations of 0.07 mg/ kg, and a maximum of 0.19 mg/ kg at four of the nine homes sampled. Soils ( up to 0.5 mm in depth) collected from childrens' play areas contained mean dieldrin concentrations of 0.03 mg/ kg and a maximum concentration of 0.09 mg/ kg. Higher dieldrin levels were found in soils from primary walkways of 0.26 mg/ kg ( mean) and a maximum concentration of 0.54 mg/ kg ( Lewis et al., 1994). 5 12 Aldrin/ Dieldrin   February 2003 Intake from Soil Aldrin Data on aldrin levels in residential soils were not located in the available literature. Thus, average daily intakes of aldrin by the general population from soil could not be estimated. The use of aldrin as a pesticide was cancelled in 1974. Based on its cancellation and its rapid conversion to dieldrin in the environment ( ATSDR, 2000), it is assumed that the general population is more likely to be exposed to dieldrin than aldrin in soils.

Dieldrin Dieldrin has been detected in both residential soils ( Lewis et al., 1994) and house dust ( Roberts and Camann, 1989) samples. Mean dieldrin concentrations ranged from 0.03 to 1.1 mg/ kg. Based on this range of concentrations, and a daily intake of 50 mg/ day ( USEPA, 1997) for a 70 kg adult, the total daily intake of dieldrin through soil ranges from 2.1 × 10 8 mg/ kg day to 7.9 × 10 7 mg/ kg day. For a 10 kg child exposed to the same soil concentrations, at an intake rate of 100 mg/ day ( USEPA, 1997), the total daily dieldrin intake would be 3.0 × 10 7 mg/ kg day to 1.1 × 10 5 mg/ kg day.

5.3.2 Exposures of Subpopulations Persons involved in the manufacture, handling, or application of aldrin and dieldrin may potentially have higher exposures to these chemicals from soil through incidental ingestion.

Concentrations in Soil Aldrin Data on aldrin concentrations in agricultural soils in the Unites States were not located in the available literature. However, one study reported aldrin in soil samples collected from agricultural fields in Farrukhabad, India from 1991 to 1992. Surface soil samples ( 0 to 15 cm) contained aldrin concentrations ranging from 0.001 to 0.010 mg/ kg, with means ranging from 0.001 to 0.004 mg/ kg. Subsurface ( 15 to 30 cm) concentrations ranged from 0.001 to 0.014 mg/ kg, with means of 0.001 to 0.006 mg/ kg ( Agnihotri et al., 1996).

Dieldrin Several studies have evaluated dieldrin residues in agricultural soils. Aigner et al. ( 1998) sampled 38 agricultural soils from Ohio, Pennsylvania, Indiana, and Illinois during 1995 and 1996 for pesticide residues. Dieldrin was detected in 21 of 38 soils at concentrations ranging from 0.12 to 71 ng/ g ( 0.00012 to 0.071 mg/ kg). One soil sample from Ohio had considerably higher dieldrin concentrations than the other soil samples with residues of 4.25 mg/ kg. This soil sample contained the highest concentrations of all individual pesticides analyzed. Samples from two garden soils contained 4.39 ng/ g ( 0.0044 mg/ kg) and 3.47 ng/ g ( 0.0035 mg/ kg) of dieldrin. 5 13 Aldrin/ Dieldrin   February 2003 Harner et al. ( 1999) reported dieldrin concentrations ranging from < 0.02 to 23.9 ng/ g dry weight (< 0.00002 to 0.024 mg/ kg), and a mean of 0.0049 mg/ kg for 36 agricultural soils surveyed throughout Alabama.

The persistence of dieldrin in agricultural fields is demonstrated by a monitoring survey conducted in and around cotton fields in four counties in Alabama between 1972 and 1974. Although aldrin or dieldrin had not been reportedly used by cotton farmers " for several years," dieldrin was found to be present in 50% of the soil samples, at concentrations ranging from 0.007 to 0.040 mg/ kg ( Elliott, 1975).

Intakes from Soil Aldrin Data on aldrin concentrations in agricultural fields in the United States were not located in the available literature. Although one study ( Agnihotri et al., 1996) was located that detected aldrin levels in agricultural soils, it reported residues for soils in India. This study is not representative of exposures to aldrin from agricultural soils that may occur in the United States. The uses of aldrin as a pesticide and termiticide have been cancelled since 1974 and 1987, respectively. Based on the cancellations of its uses in the United States and the rapid conversion of aldrin to dieldrin in the environment ( ATSDR, 2000), subpopulations are more likely to be exposed to dieldrin than aldrin in soils.

Dieldrin Several studies have reported dieldrin concentrations in agricultural soils of the United States. These concentrations range from < 0.00002 to 0.071 mg/ kg ( Harner et al., 1999 and Aigner et al., 1998). Based on these concentrations and an intake rate of 480 mg/ day ( USEPA, 1997), for a contact intensive worker, the average daily intake of dieldrin from soil for a 70 kg adult worker would range from 1.4 × 10 10 to 2.9 × 10 5 mg/ kg day. A high end estimate of potential subpopulation exposures to dieldrin in agricultural soils can be determined based on the highest concentration reported by Aigner et al. ( 1998) of 4.25 mg/ kg. At this concentration and an intake rate of 480 mg/ day ( USEPA, 1997), a 70 kg adult, contact intensive worker would have an average daily dieldrin intake of 2.9 × 10 5 mg/ kg day.

5.4 Other Residential Exposures ( Not Drinking Water Related)

Aldrin and dieldrin residues have been reported in rainfall and carpet. Dieldrin has additionally been detected in sediments.

Aldrin Aldrin was detected in rainfall collected from the Great Lakes Basin during 1986, approximately 10 years after aldrin and dieldrin use was restricted. Aldrin was present in wet precipitation at three of four sampling sites located around the basin, in 6.7% of the samples collected at a mean concentrations ranging from 0.01 ng/ L ( 1 × 10 5 ppb) to 0.24 ng/ L ( 2.4 × 10 4 5 14 Aldrin/ Dieldrin   February 2003 ppb). The highest aldrin concentrations were found in samples collected at Pelee Island at the western end of Lake Erie at a maximum concentration of 3.4 ng/ L ( 3.4 × 10 3 ppb) ( ATSDR, 2000).

Tepper et al. ( 1995) studied contaminants in carpets with a history of human health related complaints. Pesticide concentrations in the carpets were determined using Soxhletextraction ( with 6% diethyl ether/ hexane) and GC/ MS. Trace amounts of pesticides were detected in both carpet samples. Aldrin concentrations extracted from the first carpet ranged from ND 83 : g/ m2. In the second carpet, extracts contained 130 to 150 : g/ m2 aldrin. Estimates of aldrin emissions from each carpet type were not determined in this study.

Dieldrin Dieldrin was present in rainfall measured at three points in Canada during 1984, at mean concentrations of 0.78 ng/ L ( 7.8 × 10 4 ppb) over Lake Superior, 0.27 ng/ L in New Brunswick, and 0.38 ng/ L ( 3.8 × 10 4 ppb) over northern Saskatchewan ( Strachan, 1988). Dieldrin was detected in rainfall over College Station, Texas, at average concentrations of 0.80 ng/ L ( 8 × 10 4 ppb), with a washout ratio ( concentration in rain/ concentration in air) of approximately 8.9 ( Atlas and Giam, 1988).

Dieldrin concentrations in rainfall were collected in the Great Lakes Basin in 1986, approximately 10 years after aldrin and dieldrin use was restricted. Dieldrin was detected at all four sites and in more than 60% of the samples at mean concentrations ranging from 0.41 to 1.81 ng/ L ( 4.1 × 10 4 to 1.8 × 10 3 ppb). The highest concentrations of dieldrin were found in samples collected at Pelee Island at the western end of Lake Erie, with a maximum concentration of 5.9 ng/ L ( 5.9 × 10 3 ppb) ( ATSDR, 2000).

Tepper et al. ( 1995) studied contaminants in carpets with a history of human health related complaints. Pesticide concentrations in the carpets were determined using Soxhletextraction ( with 6% diethyl ether/ hexane) and GC/ MS. Trace amounts of pesticides were detected in both carpet samples. Dieldrin concentrations extracted from the first carpet ranged from ND 120 : g/ m2. In the second carpet, extracts contained 190 to 230 : g/ m2 dieldrin. Dieldrin emissions from each carpet type were not determined in this study.

Several studies have reported dieldrin residues in sediments. Composite sediment bed samples collected from 24 navigation pools of the upper Mississippi River in 1994 ( after the 1993 flooding) were analyzed for organochlorine pesticides. While dieldrin was detected in several of the navigation pools, specific concentrations were not reported ( Barber and Writer, 1998).

An analysis of sediment samples taken from Lake Ontario in 1981 showed that dieldrin levels had increased from approximately 0.026 mg/ kg in 1970 to 0.048 mg/ kg in 1980, although the use of dieldrin was banned in much of the Great Lakes Basin in the early 1970s ( Eisenreich et al., 1989). 5 15 Aldrin/ Dieldrin   February 2003 Eighty two and 84 sediment samples were collected in 1994 and 1995, respectively, from estuaries along the Carolinian Province ( Cape Henry, Virginia, to St. Lucie Inlet, Florida) as part of the EPA and NOAA's Environmental Monitoring and Assessment Program ( EMAP). Dieldrin concentrations ranged from 0 to1.4 ng/ g ( 0 to 1.4 × 10 2 mg/ kg) in 1994, and from 0 to 38.5 ng/ g ( 0 to 3.9 × 10 1 mg/ kg) in 1995 ( Hyland et al., 1998).

Bed sediments were collected from 16 sites along the Lauritzen Canal and Richmond Harbor of the San Francisco Bay area during 1994 to study the distribution of contaminants from a pesticide processing facility point source ( also a National Priorities List [ NPL] site) along the canal into the San Francisco Bay. Dieldrin concentrations in sediments ( up to 5 cm depths) ranged from < 0.1 to 400 ng/ g ( 1.1 × 10 4 to 0.4 mg/ kg) dry weight. Concentrations decreased with distance from the head of the canal, as the three sites with dieldrin concentrations above 11 ng/ g ( 1.1 × 10 2 mg/ kg) were located in Lauritzen Canal ( Pereira et al., 1996).

Burt and Ebell ( 1995) analyzed sediment samples from an industrial, commercial, and recreational area off the coast of Perth, Australia, during November 1991 for organic pollutants. Dieldrin was detected at 3 of the 135 sites sampled at concentrations of 0.002 mg/ kg dry weight.

5.5 Summary of Exposure to Aldrin/ Dieldrin in Media Other Than Water Concentration and estimated intake values for aldrin and dieldrin in media other than water are summarized in Tables 5 3 to 5 6 below. Most exposure to aldrin and dieldrin for the general population and agricultural worker subpopulation appears to occur through diet.

Table 5 3. Summary of General Population Exposures to Aldrin in Media Other than Water Parameter Medium Food Air Soil Adult Child Adult Child Adult Child Concentration in Medium Non Fish Food ( NF):

0.0016 mg/ kg Fish and Shellfish ( F):

0.01 to 0.12 mg/ kg 4.5 x 10 7 mg/ m3 NA1 Estimated Daily Intake ( mg/ kg day) NF:

3.0 x 10 5 F:

2.9 x 10 6 to 3.5 x 10 5 NF:

1.3 x 10 4 F:

4.0 x 10 6 to 4.8 x 10 5 1.3 x 10 7 6.8 x 10 7  2

1 NA = Not Available. 2  = Unable to estimate from available information. 5 16 Aldrin/ Dieldrin   February 2003 Table 5 4. Summary of General Population Exposure to Dieldrin in Media Other than Water Parameter Medium Food Air Soil Adult Child Adult Child Adult Child Concentration in Medium Non Fish Food ( NF):

0.0015 mg/ kg Fish Food ( F):

0.028 mg/ kg 1.6 x 10 6 mg/ m3 0.03 to 1.1 mg/ kg Estimated Daily Intake ( mg/ kg day) NF:

2.8 x 10 5 F:

8.0 x 10 6 NF:

1.3 x 10 4 F:

1.1 x 10 5 4.6 x 10 7 2.4 x 10 6 2.1 x 10 8 to 7.9 x 10 7 3.0 x 10 7 to 1.1 x 10 5 Table 5 5. Summary of Subpopulation Exposures to Aldrin in Media Other than Water Parameter Medium Food Air Soil Adult Worker Adult Worker Adult Worker Concentration in Medium NA1 NA NA Estimated Daily Intake ( mg/ kg day)  2

1 NA = Not Available.

2  = Unable to estimate from available information. 5 17 Aldrin/ Dieldrin   February 2003 Table 5 6. Summary of Subpopulation Exposures to Dieldrin in Media Other than Water Parameter Medium Food Air Soil Adult Worker Adult Worker Adult Worker1 Concentration in Medium 0.015 to 0.028 mg/ kg NA2 < 2 x10 5 to 0.071 mg/ kg high end: 4.25 mg/ kg Estimated Daily Intake ( mg/ kg day) 2.8 x 10 4 to 5.2 x 10 4  3 1.4 x 10 10 to 2.9 x 10 5 high end: 2.9 x 10 5 1 Estimates are intensive contact worker.

2 NA = Not Available.

3  = Unable to estimate from available information. 5 18 Aldrin/ Dieldrin   February 2003 References Agnihotri, N. P., G. Kulshrestha, V. T. Gajbhiye, S. P. Mohapatra and S. B. Singh. 1996. Organochlorine insecticide residues in agricultural soils of the Indo Gangetic Plain. Environ. Monit. Assess. 40: 279 288.

Ahmed, F. E., D. Hattis, R. E. Wolke, and D. Steinman. 1993. Risk assessment and management of chemical contaminants in fishery products consumed in the USA. J. App. Toxicol. 13 ( 6): 395 410.

Aigner E. J., A. Leone, and R. L. Falconer. 1998. Concentrations and enantiomeric ratios of organochlorine pesticides in soils from the U. S. corn belt. Environ. Sci. Technol. 32: 1162 1168.

Anderson, D. J. and R. A. Hites. 1988. Chlorinated pesticides in indoor air. Environ. Sci. Technol. 22: 717 720 ( as cited in Wallace et al., 1996)

Atlas, E. and C. S. Giam. 1988. Ambient concentration and precipitation scavenging of atmospheric organic pollutants. Wat. Air Soil Pollut. 38: 19 36 ( as cited in ATSDR, 2000).

ATSDR. 2000. Agency for Toxic Substances and Disease Registry. Toxicological profile for aldrin/ dieldrin ( Update). Draft for public comment. Atlanta, GA: U. S. Dept. of Health and Human Services, Public Health Service, ATSDR.

Barber, L. B. and J. H. Writer. 1998. Impact of the 1993 Flood on the distribution of organic contaminants in bed sediments of the upper Mississippi River. Environ. Sci. Technol. 32 ( 14): 2077 2083.

Blynn et al. 1994. Citation not found.

Bond, A. E., G. G. Akland, R. G. Lewis, and C. J. Nelson. 1993. A pilot study for measuring environmental exposures from agricultural applications of pesticides: an overview. In: Proceedings of the 1993 USEPA/ AWMA symposium on measurements of toxic and related air pollutants ( Research Triangle Park, N. C. May 3 7, 1993). VIP 34. Air and Waste Management Association, Pittsburgh, PA. p. 691 697.

Burt, J. S. and G. F. Ebell. 1995. Organic pollutants in mussels and sediments of the coastal waters off Perth, Western Australia. Mar. Pollut. Bull. 30 ( 11): 723 732.

Davies, K. 1988. Concentrations and dietary intake of selected organochlorines, including PCB's in fresh food composites grown in Ontario, Canada. Chemosphere 17: 263 276 ( as cited in ATSDR, 2000).

Dey, B. P. and C. Manzoor. 1997. Chemical residue limits in meat, poultry, and eggs for residue violation information system development. USDA Food Safety and Inspection Service ( as cited in Levengood et al., 1999). 5 19 Aldrin/ Dieldrin   February 2003 Dingle, J. H. P., W. A. Palmer, and R. R. Black. 1989. Residues of DDT and dieldrin in the subcutaneous fat and butterfat of cattle. Australian Journal of Experimental Agriculture 29: 497 501 ( as cited in ATSDR, 2000).

Dobbs, A. J. and N. Williams. 1983. Indoor air pollution from pesticides used in wood remedial treatments. Environ. Pollut. ( Series B) 6: 271 296 ( as cited in ATSDR, 2000).

Eisenreich, S. J., P. D. Capel, J. A. Robbins, and R. Bourbonniere. 1989. Accumulation and digenesis of chlorinated hydrocarbons in lacustrine sediments. Environ. Sci. Technol. 23: 1116 1126 ( as cited in ATSDR, 2000).