---
                                                                            ---

                                      CND
Craik, 2016
                                                                           0.82
                                                                           9.18
                                                                           1.97
                                                                           1.13
                                                                            322
                                                                             85
                                                                             85

Deshommes et al., 2016
                                                                           3.31
                                                                           3.72
                                                                           5.31
                                                                           4.04
                                                                             73
                                                                             12
                                                                             10

Hayes et al., 2014
                                                                           1.01
                                                                           1.80
                                                                           6.00
                                                                           3.53
                                                                             24
                                                                              1
                                                                              1

Muylwyk, 2016
                                                                           1.24
                                                                           3.15
                                                                           1.00
                                                                           0.50
                                                                            450
                                                                            225
                                                                            224
                                    No LSL
                                    Partial
                                      USA
Del Toral, 2016
                                                                           1.74
                                                                           3.71
                                                                           8.33
                                                                           6.85
                                                                            222
                                                                             11
                                                                              7

DC Water, 2016
                                                                           1.92
                                                                           2.02
                                                                           7.50
                                                                           4.47
                                                                             15
                                                                              1
                                                                              1

Swertfeger et al., 2006; Desmarais et al., 2015; Triantafyllidou et al., 2015
                                                                           2.41
                                                                           3.59
                                                                           0.38
                                                                           0.00
                                                                             61
                                                                             61
                                                                              5

                                      CND
Camara et al., 2013
                                                                           1.42
                                                                           2.98
                                                                           2.00
                                                                           1.29
                                                                              4
                                                                              1
                                                                              1
                                    No LSL
                                Representative
                                      USA
Del Toral, 2016
                                                                           0.66
                                                                           1.81
                                                                           6.87
                                                                           4.87
                                                                            118
                                                                              7
                                                                              4

DC Water, 2016
                                                                           0.66
                                                                           2.39
                                                                           6.44
                                                                           3.83
                                                                             51
                                                                              4
                                                                              4

                                      CND
None
                                                                            ---
                                                                            ---
                                                                            ---
                                                                            ---
                                                                            ---
                                                                            ---
                                                                            ---
[a] Each citation contains data from a single city water system (Exhibit 6-1). Some citations have entries in multiple categories.
[b] Arithmetic mean and SD of the "profile liter" term and number of individual sample bottles, profiles, and sites provide information regarding some of the differences in sampling methods observed among studies. Studies with fewer samples, or with smaller sample volumes, have smaller values of profile liter. Some studies always collected the same sample volume and others sampled to a particular point (e.g., until the water had run cold from the tap). CND = Canada, USA = United States of America, and SD = standard deviation.

Exhibit 6-5: Summary Statistics, Including Geometric Mean, Standard Deviation (SD), Maximum Value, and Sample Size for Tap Water Lead Concentration Sample Data by LSL and CCT Status Used in Statistical Modeling*
                                  LSL Status
                                  CCT Status
                         Number of Individual Samples
                   Geometric Mean Lead Concentration (ug/L)
                       Geometric SD Lead Concentration
                       Maximum Lead Concentration (ug/L)
LSL
 None
                                     2,055
                                     17.79
                                     2.27
                                      170
Partial
 None
                                     1,408
                                     8.61
                                      3.9
                                      180
No LSL
 None
                                      869
                                     1.15
                                     5.32
                                     119.3
LSL
 Partial
                                     4,331
                                     4.99
                                     4.13
                                     2,970
Partial
 Partial
                                      217
                                     6.49
                                     2.97
                                     81.13
No LSL
 Partial
                                      302
                                     1.86
                                      3.6
                                       36
LSL
 Representative
                                     8,129
                                     2.37
                                     3.60
                                      714
Partial
 Representative
                                      559
                                     1.63
                                     2.95
                                     38.03
No LSL
 Representative
                                      169
                                     0.66
                                     1.98
                                      12.3
Note: The table shows values based on the full dataset used for the analysis shown in Section 6.2.2, not just those at a particular position in a sampling series. These values were not directly used in blood lead modeling, as they do not adequately control for repeated sampling within sites and city water systems, or for differences in profile liter.
* CCT designations changed from "Representative" to "Partial" for three city water systems based on public comment. These changes are reflected in this table and the following analysis.
Coding
After cleaning the data as described above, EPA added a centered "profile liter" term and contrast-coded variables describing LSL and CCT for use in fitting models. The profile liter term controls for differences in cumulative sample volume and sampling profile series position, as described in Section <IP_ADDRESS>. Centering the intercept at the mean value of a profile liter for all samples allowed for improved interpretation of interaction terms. Contrast codes likewise improve interpretability and ease of projection from the fitted model, particularly when interactions are included.
To produce the centered profile liter term, EPA calculated the midpoint of the cumulative sample volume, as described in Section <IP_ADDRESS>. Then, the mean of the original profile liter term was subtracted from the profile liter term for all samples. This sets the intercept for the model to a profile liter of approximately 4.5, this point is analogous to the fifth liter drawn from the tap after stagnation.
EPA used the sample data's descriptive information on LSL status to generate two contrast variables that allow for the statistical comparison of water lead concentrations between the three LSL scenarios represented in the data ("LSL," "Partial," and "No LSL"). The "LSL (yes/no)" variable indicates lead concentration samples that come from sites with a full LSL compared to samples from locations with no LSL. "LSL (no/partial)" designates samples that come from sites with a partial LSL in place compared to site samples that come from locations with no LSL. Used together in the statistical model, these two variables allow EPA to compare water lead concentrations in homes with no LSLs to concentrations in homes with full LSLs and homes with partial LSLs. Exhibit 6-6 shows the numeric codes used to describe LSL status in the analysis.
EPA determined corrosion control levels for each lead concentration sample reported through records of CCT practices and implementation dates, as well as water quality samples. CCT was coded as a single contrast variable, "CCT (yes/no)," marking those tap samples taken in the presence of corrosion control against those sample taken at sights without CCT. This variable is used to quantify the difference between water lead concentrations at sites with representative CCT, partial CCT, and no CCT. Exhibit 6-7 shows the codes used to represent CCT in the analysis.
Exhibit 6-6: Numeric Values Assigned to Two Discrete Contrast Variables Representing LSL Status in the Estimated Drinking Water Lead Concentration Regression Model
                                  LSL Status
                                 LSL (yes/no)
                               LSL (no/partial)
                                      LSL
                                      -0.5
                                       0
                                    Partial
                                       0
                                     -0.5
                                    No LSL
                                      0.5
                                      0.5

Exhibit 6-7: Numeric Values Assigned to a Discrete Contrast Variable Representing CCT Status Use in the Estimated Drinking Water Lead Concentration Regression Model
                                  CCT Status
                                 CCT (yes/no)
                                     None
                                      -0.5
                                    Partial
                                       0
                                Representative
                                      0.5

Drinking Water Lead Concentration Model Fitting and Selection
Next, EPA developed a model to estimate typical lead concentrations for each intervention category. The intervention category is confounded with differences in profile liter of individual samples, as well as with numbers of sites and profiles from each city water system (Exhibit 6-4, Exhibit 6-5). Therefore, geometric means cannot be directly compared across intervention categories. Rather than selecting only samples from some common profile liter (e.g., the "first liter"), and aggregating within sites and city water systems to produce a homogeneous subset of the dataset, EPA fit linear mixed-effects models with explicit terms to statistically control for the differences in profile liter, city water system, site, and sampling event. This single-step meta-analysis allowed for the greatest inclusion of available data, while limiting the effects of different methods.
EPA fit multiple, nested, linear mixed-effects models (Equation 1 - 5, Exhibit 6-8) of tap water lead concentration as predicted by LSL presence ("LSL" or "No LSL"), LSL extent ("None" or "Partial"), CCT status, and profile liter. To simplify model fitting, these models assumed equal variance in lead concentration among combinations of LSL and CCT status, profile liter, and sampling events. This assumption means the model may slightly over- or under-estimate the variation in lead water concentrations in some scenarios. For instance, increased variability may occur as lead flushes from residential pipes after LSLR; or in cases of "partial" CCT, where poorly optimized and changing corrosion control may interact unpredictably with pipe chemistry to produce more variable concentrations than would be expected with fully optimized corrosion control. To understand how this assumption of equal variance might affect model results, EPA performed additional sensitivity analyses using multiple means and variances for lead water concentrations (Appendix F).
EPA compared several models, from simple to more complex, to find the best function for use in predicting lead concentrations at the tap (Equation 1 - 5). For all models, EPA allowed the intercept of the fitted equation (mean lead concentration at the fifth liter assuming no LSL or CCT; see Section <IP_ADDRESS>) to vary by sampling event and location, with each sampling event nested within a site and each site nested within a city water system. EPA also considered models that accounted for random variation in parameters, such as differences in length of a service line among sites, or specific features that could change the effectiveness of CCT, related to event, site, and city water system, but found that the collected dataset does not contain sufficient information to fit such models.
To describe the non-linear effects of the profile liter, the models include a natural cubic spline. The spline models the effect of the profile liter as a curve, and allows the fitted lead concentration to increase and decrease as water is drawn through the household and service line (Exhibit 6-2 and Exhibit 6-3). This spline included three interior knots and two boundary knots. Knots define points where different pieces of the curve meet and allow the model to be fit with different "sub" curves for each piece between the knots. The three interior knots correspond to the first 0.5, 4, and 8 liters after beginning sampling and have curves at either end. Boundary knots correspond to 0.06 liters and 13 liters after beginning sampling. These knots produce linear sections at either end of the curve where there were few samples. Models were fitted with the lme4 package in R (Bates, 2010; Bates et al., 2015; Pinheiro et al., 2017; R Core Team, 2016) with full-information maximum likelihood (FIML) for model comparisons and restricted maximum likelihood (REML) to produce final parameters after model selection (Bolker et al., 2009).
In the equations below, "i" identifies a particular water sample, and "j" identifies a sampling event, nested within a site and a city water system. β refers to the coefficient for each parameter. Thus, β0j is the intercept for a particular sampling event j. βs terms refer to matrices of spline coefficients (not shown) for each model term that includes a spline. Thus, βs1 is the matrix of spline coefficients for the effect of the profile liter term alone.
Full spline model:

logePb ugLij=β0j+SplineProfile Literi*βs1+β1LSL yesnoii +β2LSL nopartiali+β3CCTi +β4LSL yesnoii*CCTi +β5LSL nopartiali* CCTi +SplineProfile Literi*βs2LSL yesnoii+SplineProfile Literi* βs5 LSL nopartiali+SplineProfile Literi* βs4 CCTi+SplineProfile Literi*βs5LSL yesnoii* CCTi+SplineProfile Literi*βs6LSL nopartiali* CCTi+ εi
                                 (Equation 1)
Reduced spline model with CCT interactions:

logePb ugLij=β0j+SplineProfile Literi*βs1 +β1LSL yesnoi +β2LSL nopartiali+β3CCTleveli                 +β4LSL (yes/no) i*CCTi+β5LSL (no/partial)i* CCTi +SplineProfile Literi*βs2LSL (yes/no)i+SplineProfile Literi* βs5 LSL nopartiali+ εi
                                 (Equation 2)
Reduced spline model without CCT interactions:

logePb ugLij=β0j+SplineProfile Literi*βs1+β1LSL(yes/no)i+β2LSL nopartiali+β3CCTi+SplineProfile Literi*βs2LSL yesnoi+SplineProfile Literi* βs5 LSL nopartiali+ εi
                                 (Equation 3)
Spline model with no interactions:

logePb ugLij=β0j+SplineProfile Literi*βs1+β1LSLyesnoi+β2LSL (no/partial)i+β3CCTi+ εi
(Equation 4)
Linear model with no interactions:

logePb ugLij=β0j+β1Profile Literi+β2LSL (yes/no)i+β3LSL (no/partial)i+β4CCTi+ εi
                                 (Equation 5)

EPA selected the "Reduced spline model with CCT interactions" (Equation 2) to produce simulated lead concentrations for use in the benefits analysis. Although the most complex "full spline" model showed the best fit overall (Equation 1, Exhibit 6-8), the improvement in fit was small relative to the increase in complexity, and a close examination of the fitted model suggested that the full spline model over-fit specific study parameters and produced predictions that were likely unrealistic. The full model projected a gradual rise in lead concentration after the service line peak for some intervention combinations, which is unlikely to be realistic given that the water represented in this tail of the profile represents non-stagnated water from the system main. In addition, for homes with no LSLs, the full model produced predictions of relatively high lead concentrations in homes with representative CCT, and relatively low concentrations in homes with no CCT. Again, this is unlikely to represent the true effects of CCT; therefore, the simpler model was selected for simulation.
Exhibit 6-8: Comparison of Tap Sample Lead Concentration Model Results Based on Maximum Likelihood Estimators for Goodness of Fit
                                     Model
                                     DF[a]
                                Log-Likelihood
                                      AIC
                                      BIC
 Full spline (Equation 1)
                                      34
                                   -19,922
                                    39,912
                                    40,177
 Reduced spline with CCT interaction (Equation 2)
                                      22
                                   -20,016
                                    40,077
                                    40,248
 Reduced spline without CCT interaction (Equation 3)
                                      20
                                   -20,036
                                    40,112
                                    40,268
 Spline model with no interactions (Equation 4)
                                      12
                                   -20,139
                                    40,302
                                    40,395
 Linear with no interactions (Equation 5)
                                       9
                                   -20,675
                                    41,367
                                    41,437
a Degrees of freedom (DF) are the number of parameters estimated for the model, including the variance for each random effects level (sampling event is nested within the site nested within the city water system), fixed coefficients, and the residual error. The other columns provide model fit statistics for comparing the fixed terms of the model. AIC is Akaike's Information Criterion & BIC is Bayesian Information Criterion. For AIC and BIC, the smaller numbers imply more preferred models; and for log-likelihood, the larger numbers imply a better fit to the underlying data.
The reduced spline model with CCT interactions suggests that besides water system, residence, and sampling event, the largest effects on lead concentration come from LSLs and the number of liters drawn since the last stagnation period (Exhibit 6-9).
Exhibit 6-9: Results from the Reduced Cubic Spline Interaction Model with CCT Interactions: Fixed Effects and Random Effects for Sampling Event, Site, and City Water System
                                 Fixed Effects
                                     β[a]
                                     SE[b]
                              F (Type III SS)[c]
Intercept
                                     1.41
                                     0.165
                                      80
Cumulative volume (spline)
                                      ---
                                      ---
                                      165
LSL (yes/no)
                                     -1.06
                                     0.094
                                      128
LSL (no/partial)
                                     -0.89
                                     0.173
                                      27
CCT (no/representative)
                                     -0.74
                                     0.164
                                      21
LSL (yes/no)* CCT (no/representative)
                                     0.95
                                     0.182
                                      27
LSL (no/partial)* CCT (no/representative)
                                     1.78
                                     0.321
                                      31
LSL (yes/no)* Cumulative volume (spline)
                                      ---
                                      ---
                                      38
LSL (no/partial)* Cumulative volume (spline)
                                      ---
                                      ---
                                      25
                               Random Effects[d]
                                       N
                                      SD
Sampling event in site in city water system
                                     3,102
                                     0.53
Site in city water system
                                     1,638
                                     1.07
City water system
                                      14
                                     0.59
Individual samples (Total N)[e]
                                    18,039

a β, the unstandardized regression coefficient, provides the size and direction of the relationship between each model term and log-transformed lead concentration. β for spline effects are too complex to show in this exhibit.
[b] SE shows the standard error estimated for each coefficient.
[c] F provides the F statistic for each coefficient after controlling for all other coefficients for type III sums of squares (SS). Unbalanced sample sizes for random effects complicate accurate degrees of freedom (DF) calculations, and no p-values are provided. However, larger F values indicate stronger effects.
d For random effects, N shows the number of groups at each level, and  SD provides the attributable to that level of random effect.
e Total N is the number of individual sample bottles.
N = number of observations, and SD = standard deviation.

The fitted model for the reduced cubic spline interaction (Equation 2) was used to produce simulated concentrations of lead at the kitchen tap that statistically control for variation in the sample dataset due to differences in profile liter among studies, the city water system, the site, and the sampling event. Additionally, the simulated concentrations incorporate variation in lead levels found among sampling events, sites, and city water systems.
Simulated Drinking Water Lead Concentrations Based on Selected Model Fit
For use in blood lead modeling, EPA produced 500,000 simulated lead concentrations based on the final model (reduced spline with CCT interactions; Equation 2; Exhibit 6-9). These concentrations were simulated using the arithmetic mean profile liter value of the original dataset (4.45) taken after stagnation (Exhibit 6-10), which, on average, was the peak lead concentration for residences with "LSL" or "Partial LSL" regardless of CCT level. The dataset simulates concentrations for new cities, sites, and sampling events not included in the original dataset using estimates of variability and uncertainty from the fitted model, and given information on LSL and CCT status. While the simulated dataset includes variability similar to the original data, individual simulated estimates are best thought of as central tendencies of possible concentration values given fitted model parameters and estimated variance. The simulated results also incorporate the model assumptions of equal variance in lead concentration among different scenarios, and equal variance over the range of profile liters, as previously discussed in Section 6.2.2.
Exhibit 6-10: Estimates for the Simulated Data Showing the Relationship between Tap Lead Concentration and Profile Liter for Each Combination of CCT and LSL Status

Note: Central estimates are solid lines, and 95 percent confidence intervals (CIs) (bootstrapped) are indicated by shaded areas bounded by dotted lines. The highest concentrations occur, on average, roughly 5 liters after the last stagnation period in homes with LSLs in place. Note that CIs can overlap somewhat even where there is a significant effect of scenario (i.e., CCT and LSL presence). However, for scenarios with no LSLs, CIs for CCT scenarios overlap almost completely.

Though CCT produced significant reductions in lead water concentrations, the simulated predictions for sites with full LSL removals primarily overlapped for all CCT conditions in the final model (Exhibit 6-8). Therefore, EPA used the pooled estimate for all CCT conditions in residences with no LSL in place (this is referred to as "combined CCT"). Because of this overlap in the simulated data, EPA was unable to quantify the impacts of improvements in CCT status on non-LSL households using these data.
Exhibit 6-11: LSL and CCT Scenarios and Simulated Geometric Mean Tap Water Lead Concentrations and Standard Deviations at the Fifth Liter Drawn after Stagnation for Each Combination of LSL and CCT Status
                                  LSL Status
                                  CCT Status
                      Simulated Mean of Log Lead
(ug/L)
                         Simulated SD[a] of Log Lead

                   Simulated Geometric Mean of Lead
(ug/L)
                       Simulated Geometric SD[a] of Lead
 LSL
                                     None
                                     2.89
                                     1.33
                                     18.08
                                     3.78
 Partial
                                     None
                                     2.13
                                     1.33
                                     8.43
                                     3.77
 No LSL
                                     None
                                   -0.19[b]
                                    1.35[b]
                                    0.82[b]
                                    3.86[b]
 LSL
                                    Partial
                                     2.29
                                     1.33
                                     9.92
                                     3.78
 Partial
                                    Partial
                                     1.55
                                     1.32
                                     4.72
                                     3.75
 No LSL
                                    Partial
                                   -0.19[b]
                                    1.35[b]
                                    0.82[b]
                                    3.86[b]
 LSL
                                Representative
                                     1.70
                                     1.33
                                     5.48
                                     3.77
 Partial
                                Representative
                                     0.97
                                     1.32
                                     2.64
                                     3.76
 No LSL
                                Representative
                                   -0.19[b]
                                    1.35[b]
                                    0.82[b]
                                    3.86[b]
[a] SD reflects "among-sampling event" variability.
[b] Bolded values show how simulated results were pooled to produce a common estimate for homes with no LSL across CCT conditions.
LSL = lead service line, CCT = corrosion control treatment, and SD = standard deviation.
Although the existing data did not provide enough information to estimate the effect of CCT where no LSL were present (Exhibit 6-10 and Exhibit 6-11), the CCT status of the PWS is tracked in the analysis regardless of LSL status. This is described in Section 6.3. Note in Exhibit 6-11 that the statistics describing the distribution of tap water lead concentrations are the same for all three rows for "no LSLs," regardless of whether there is representative, partial, or no CCT. Effectively, in the primary analysis EPA did not quantify the incremental benefits of CCT when LSLs are absent. On the other hand, because CCT is done on a system-wide basis, there are no incremental costs associated with providing CCT to homes without LSLs when it is being provided for the entire system. The impact of CCT for these no LSL homes likely varies by location depending on whether there are legacy system and/or household lead solder or higher lead content brass parts.
Two approaches for alternative water modeling in the absence of LSLs are discussed in the appendices. Appendix F outlines an approach for considering the potential increase in benefits that may accrue to non-LSL households experiencing changes in CCT as a result of the rule if indeed the effect of CCT for these households is larger than assumed in the main analysis. This first supplemental analysis incorporates data from homes in Michigan where CCT presence/absence and LSL status were known, and first liter samples were available for homes without LSL. The second analysis, described in Appendix G, also approximates the lead concentration of water in non-LSL homes where CCT changes occur as a result of the rule using the mean value lead tap concentration values from the original cleaned profile dataset, rather than the simulated data output. The existing cleaned profile liter data used to fit the curves for simulation did not contain enough profiles before and after the implementation of representative CCT from homes without LSL to fit parameter estimates. Therefore, these estimates were based on close examination of the existing data for homes without LSLs under varying CCT conditions, as well as expert knowledge regarding the potential effects of improving CCT. Neither of these methods, however, account for inter- and intra-system water quality variability in the need for LSLR or the distribution of household ages. Again, EPA did not look at the potential for the impact of added CCT to be less than estimated in the primary analysis presented in this chapter. To maintain a consistent data-driven underpinning for the primary benefits analysis, these estimates were not used for the primary benefits calculation, but are presented in Appendix F as part of a sensitivity analysis.
Determination of Point-of-Use Water Concentrations
In addition to modeled drinking water concentrations, the following water filtration devices are also considered:
 A point-of-use (POU) device is a water filtration device physically installed or connected to a single fixture, outlet, or tap to reduce or remove contaminants in drinking water. For the purposes of subpart I, it is certified by an American National Standards Institute (ANSI)-accredited certifier to reduce lead in drinking water.
 A pitcher filter means a non-plumbed water filtration device that consists of a gravity feed water filtration cartridge and a filtered drinking water reservoir, and is certified by an ANSI-accredited certifier to reduce lead in drinking water.
To estimate benefits, only the first bullet is included under "POU" device. Pitcher filters are useful in some cases, such as mitigating potential short-term increases in lead exposure after the replacement of an LSL. However, only the physical installation of a POU device is included in the rule option. POU devices that are potentially used under the LCRR as part of the treatment technique requirements must be certified by an ANSI-accredited certifier to reduce lead in drinking water. To be certified, POU devices need to demonstrate an ability to remove at least 93 percent of lead. One third-party certification organization, NSF International, conducts demonstration tests well beyond manufacturers' recommended filter replacement schedules (NSF International, 2019). Due to the high efficiency of these filters, EPA chose to assign the lowest-modeled water concentration (0.82 μg/L) to those households using POU devices, regardless of LSL and CCT status. In doing so, EPA assumes that POU devices are properly used and maintained. EPA did not perform sampling to confirm this assumption.
Limitations of Baseline and Post-Rule Water Concentration Estimates
Although EPA tried to account for and model variability in lead concentrations at the tap using all available historical datasets that met inclusion criteria, the underlying data and chosen modeling strategy have limitations. First, the datasets came from 14 water systems in the United States and Canada (Exhibit 6-1, Exhibit 6-4, and Exhibit 6-5). Within the United States, datasets include only samples from the Northeast and from a few water systems in the upper Midwest. Therefore, the source data do not fully represent water quality conditions, chemistry differences in pipe scale, and treatment practices across all United States regions. There was not enough information to include housing age, which may be related to additional sources of lead. Additionally, the original studies (Exhibit 6-1, Exhibit 6-4, and Exhibit 6-5) were conducted for different reasons by different entities, and sometimes varied in their sampling methods. Both of these issues may limit generalizability of the data.
The simulated concentrations statistically control for differences in methodology among studies by standardizing the "profile liter" term and including random effects to control for repeated samples within sampling event, site, and city water system. This approach is not equivalent to conducting a large new study to collect consistent samples over a broader variety of water systems. As previously discussed, using simulated concentrations also incorporates some assumptions, such as equal variance in lead concentrations among different combinations of CCT and LSL status.
Assignment of Drinking Water Lead Tap Concentrations to PWS Populations
This section first describes how the simulated drinking water concentrations described in Section 6.2 are assigned to each type of PWS, and next describes how the number of people in each PWS are estimated and tracked through the analysis period. Each tap water lead concentration displayed in Exhibit 6-11 is assigned to the various LSL, POU, and CCT scenarios under the rule. Due to data limitations, some scenarios have been assigned the same lead tap water concentration. As illustrated in Exhibit 6-10, in the case where there is no LSL, CIs on modeled drinking water concentrations, regardless of CCT status, all overlap. Therefore, as described in Section 6.2.1, these were combined in the analysis. It is possible that given more data, one might expect to see lower drinking water lead levels when CCT is optimized. For this reason, EPA kept these scenarios separate in the benefits modeling, including tracking the number of people in PWSs with this LSL/CCT status.
Mapping Exhibit 6-11 drinking water concentrations to modeled benefit scenarios is illustrated in Exhibit 6-12.
Exhibit 6-12: Mapping Simulated Drinking Water Lead Tap Concentrations to Benefit Scenarios
                                  LSL Status
                                  CCT Status
            Geometric Mean Tap Water Lead Concentration[a] (μg/L)
                                 Geometric SD
                                      LSL
                                     None
                                     18.08
                                     3.78
                                    Partial
                                     None
                                     8.43
                                     3.77
                                    No LSL
                                     None
                                    0.82[b]
                                    3.86[b]
                                      LSL
                                    Partial
                                     9.92
                                     3.78
                                    Partial
                                    Partial
                                     4.72
                                     3.75
                                    No LSL
                                    Partial
                                    0.82[b]
                                    3.86[b]
                                      LSL
                                Representative
                                     5.48
                                     3.77
                                    Partial
                                Representative
                                     2.64
                                     3.76
                                    No LSL
                                Representative
                                    0.82[b]
                                    3.86[b]
                                      POU
                                    0.82[b]
                                    3.86[b]
           [a] Simulated geometric mean water concentrations are based on available data for various LSL and CCT scenarios, as described in Section 6.2.3.
           [b] Bolded values show how simulated results were pooled to produce a common estimate for homes with no LSLs across CCT conditions. Also, these "No LSL" values were used for POU lead tap concentrations.
EPA estimated benefits under both the low- and high-cost scenarios used in the LCRR that characterize uncertainty in the cost estimates. The low- and high-cost scenario differ in their assumptions about 1) the existing number of LSLs in PWSs, 2) the number of PWS above the action level (AL) or trigger level (TL) under the previous and final rule monitoring requirements, 3) the cost of installing and optimizing CCT, 4) the effectiveness of CCT in mitigating lead concentrations, and 5) the cost of LSLR.
The monetary benefits of the rule are modeled in the SafeWater Lead and Copper Rule (LCR) model. For each model PWS, a population cohort is created in the SafeWater LCR model. Each simulated population cohort for each PWS has an age distribution equal to that of the general population, and is followed in the benefits analysis for 35 years. A new cohort of infants is added in each subsequent year of the 35-year analysis based on birth rates from the 2000 United States Census. Thus, 35 cohorts of children are modeled to age 7 and can possibly accrue benefits due to implementation of the rule  -  one cohort for each year of the analysis. EPA does not quantify avoided IQ loss for children who have not reached age 7 by the end of the analysis period. This assumption would underestimate benefits for the LCRR given that children ages 1 - 6 in the final (35[th]) year of the analysis are not predicted to experience quantified avoided IQ loss in this approach but are expected to experience a reduction in lead exposure.
In the analysis, EPA assumes that characteristics of households with LSLs have the same characteristics as the general population. Each statistical person within a model PWS in the SafeWater LCR model is initially assigned to one of the simulated drinking water lead concentrations in Exhibit 6-11, depending on the CCT status and number of LSLs assigned to that modeled system in the baseline. Depending on the rule requirements, implementation schedule, and each year's tracked system level 90[th] percentile tap sample lead concentration, a modeled PWS may experience changes in CCT, LSL, and POU status if the system has a TL or AL exceedance. Based on these modeled changes in CCT, POU, and LSL status, specific proportions of the modeled population within the system will be assigned to a new lead tap water concentration category representing the new technology in place at the system in each year of the 35-year period of performance.
For a further discussion of how this is implemented in the SafeWater LCR model, see the flow charts in Appendix B; and for the following discussions, see Section B.3, Estimating the Cost of Compliance with the LCRR:
 Small community water systems (CWSs) serving 3,300 or fewer people and all non-transient non-community water systems (NTNCWSs) can choose POU, CCT, or LSLR; and are assumed to choose whichever compliance option has the lowest cost,
 How the SafeWater LCR model determines if a PWS installs/optimizes CCT or installs a POU device, and
 How the SafeWater LCR model determines if a PWS replaces LSLs.
Due to different assumptions, different numbers of people will experience benefits under the low- and high-cost scenarios.
Exhibit 6-13 and Exhibit 6-14 summarize the number of people who move from one treatment combination (i.e., beginning condition) to another (i.e., ending condition) over the 35-year analysis period across all model PWS strata in the SafeWater LCR model for the low- and high-cost scenarios, respectively. These exhibits include people who move more than once over the 35-year period. These exhibits do not display the total number of people in the Nation with this type of treatment; rather, it displays those who are estimated to experience a change in water lead concentration as a result of the final rule. The exhibits present the number of people experiencing a change from a baseline water lead concentration, represented in the "Beginning Concentration" column of the exhibits; to a new water lead concentration, labeled "Ending Concentration" over the 35-year period of analysis as a result of implementing the LCRR requirements with the SafeWater LCR model. In the case of a CCT installation or re-optimization, the entire population of a model PWS will move to the new CCT status at the same time. EPA also assumes that the entire PWS moves to the drinking water lead concentration (from Exhibit 6-12), assigned to a POU device when this option is implemented by the PWS, which implies that everyone is properly using the POU device. Thus, a corresponding change in the concentration of lead in drinking water will occur for the entire PWS population in the year the change is implemented. Chapter 5 provides more detail on these assumptions.
For LSLR, the portion of the population corresponding to the number of households undergoing LSLR each year will change to the lower drinking water lead concentrations and BLLs in the year the LSL is replaced. For each year of analysis, IQ benefits are captured once a child reaches 7 years of age, which is described in more detail in Section 6.4. To simplify the analysis, EPA assumes no change in other sources of lead exposure besides drinking water over the 35-year timeline used in the analysis. This includes exposure to lead in drinking water not consumed in the home.
EPA did not quantify the benefits of reduced lead exposure to individuals who reside and work in buildings that do not have LSLs. These buildings, while not having an LSL in place, may still contain leaded plumbing materials, including leaded brass fixtures and leaded solder. EPA expects that the LCRR requirements will result in reduced lead exposure to the occupants of these buildings as a result of improved monitoring and additional actions to optimize CCT. In the analysis of the final rule, approximately 20 million people (8 million households) for the low-cost scenario and 44 million people (17 million households) for the high-cost scenario could potentially be affected by reductions in lead drinking water concentrations that result from water systems' increasing their corrosion control during the 35-year analysis period. A sensitivity analysis of this assumption using alternative water concentrations is presented in Appendix G.
In the main LCRR analysis, EPA assumes there is no difference in the geometric mean water lead concentration in households with no LSL, regardless of CCT status. In other words, for each of the three scenarios of no LSL (i.e., no LSL  -  no CCT, no LSL  -  partial CCT, and no LSL  -  representative CCT), the geometric mean water lead concentration is equivalent to 0.82 ug/L, which is likely to lead to an underestimate of benefits. EPA assessed potential benefits to children in these homes by also estimating alternative water concentrations for these scenarios. This approach assumes that there is still a benefit to CCT in the absence of an LSL due to the potential leaching of lead from internal fixtures such as lead solder on brass water faucets. The Agency has determined that the data are too limited and the uncertainties too significant to include this assessment in the primary quantified and monetized benefit estimates of this regulation. This analysis is presented in Appendix G.

Exhibit 6-13: Summary of Geometric Mean Water Lead Concentration Changes Resulting from Rule Implementation, and Associated Number of People for Each Treatment Combination Change over 35-Year Analysis Period (Low-Cost Scenario)
                              Beginning Condition
                               Ending Condition
                       Number of People (over 35 years)
                                      LSL
                                      CCT
                             Concentration (ug/L)
                                      LSL
                                      CCT
                                      POU
                             Concentration (ug/L)
                                    Baseline
                                     Option
                                  Incremental
 LSL
 None
                                                                          18.08
 No LSL
 None
 None
                                                                           0.82
                                                                             93
                                                                          1,322
                                                                          1,229
 LSL
 None
                                                                          18.08
 LSL
 Representative
 None
                                                                           5.48
                                                                            322
                                                                              0
                                                                           -322
 LSL
 None
                                                                          18.08
 No LSL
 Representative
 None
                                                                           0.82
                                                                              0
                                                                              0
                                                                              0
 LSL
 None
                                                                          18.08
 LSL
 None
 Yes
                                                                           0.82
                                                                              0
                                                                              6
                                                                              6
 Partial
 None
                                                                           8.43
 No LSL
 Partial
 None
                                                                           0.82
                                                                              0
                                                                            333
                                                                            333
 Partial
 None
                                                                           8.43
 Partial
 Representative
 None
                                                                           2.64
                                                                              0
                                                                              0
                                                                              0
 Partial
 None
                                                                           8.43
 No LSL
 Representative
 None
                                                                           0.82
                                                                              0
                                                                              0
                                                                              0
 Partial
 None
                                                                           8.43
 Partial
 Partial
 Yes
                                                                           0.82
                                                                              0
                                                                              2
                                                                              2
 No LSL
 None
                                                                           0.82
 No LSL
 Representative
 None
                                                                           0.82
                                                                      1,855,625
                                                                      1,645,916
                                                                       -209,710
 No LSL
 None
                                                                           0.82
 No LSL
 None
 Yes
                                                                           0.82
                                                                              0
                                                                        206,907
                                                                        206,907
 LSL
 Partial
                                                                           9.92
 No LSL
 Partial
 No
                                                                           0.82
                                                                         10,470
                                                                        630,532
                                                                        620,062
 LSL
 Partial
                                                                           9.92
 LSL
 Representative
 None
                                                                           5.48
                                                                         44,487
                                                                      2,357,596
                                                                      2,313,109
 LSL
 Partial
                                                                           9.92
 No LSL
 Representative
 None
                                                                           0.82
                                                                              0
                                                                         90,505
                                                                         90,505
 LSL
 Partial
                                                                           9.92
 LSL
 Partial
 Yes
                                                                           0.82
                                                                              0
                                                                          1,857
                                                                          1,857
 Partial
 Partial
                                                                           4.72
 No LSL
 Partial
 No
                                                                           0.82
                                                                         15,371
                                                                        152,245
                                                                        136,874
 Partial
 Partial
                                                                           4.72
 Partial
 Representative
 None
                                                                           2.64
                                                                         64,514
                                                                        584,661
                                                                        520,147
 Partial
 Partial
                                                                           4.72
 No LSL
 Representative
 None
                                                                           0.82
                                                                              0
                                                                         22,621
                                                                         22,621
 Partial
 Partial
                                                                           4.72
 Partial
 Partial
 Yes
                                                                           0.82
                                                                              0
                                                                             52
                                                                             52
 No LSL
 Partial
                                                                           0.82
 No LSL
 Representative
 None
                                                                           0.82
                                                                      4,170,466
                                                                     23,895,595
                                                                     19,725,129
 No LSL
 Partial
                                                                           0.82
 No LSL
 Partial
 Yes
                                                                           0.82
                                                                              0
                                                                         29,455
                                                                         29,455
 LSL
 Representative
                                                                           5.48
 No LSL
 Representative
 None
                                                                           0.82
                                                                              0
                                                                        133,346
                                                                        133,346
 LSL
 Representative
                                                                           5.48
 LSL
 Representative
 Yes
                                                                           0.82
                                                                              0
                                                                              0
                                                                              0
 Partial
 Representative
                                                                           2.64
 Partial
 Representative
 Yes
                                                                           0.82
                                                                              0
                                                                              0
                                                                              0
 No LSL
 Representative
                                                                           0.82
 No LSL
 Representative
 Yes
                                                                           0.82
                                                                              0
                                                                              0
                                                                              0
Note: This exhibit summarizes the number of people who move from one treatment combination (i.e., beginning condition) to another (i.e., ending condition) over the 35-year analysis period across all modeled PWSs in the SafeWater LCR model.

Exhibit 6-14: Summary of Geometric Mean Water Lead Concentration Changes Resulting from Rule Implementation, and Associated Number of People for Each Treatment Combination Change over 35-Year Analysis Period (High-Cost Scenario)
                              Beginning Condition
                               Ending Condition
                       Number of People (over 35 years)
                                      LSL
                                      CCT
                             Concentration
(ug/L)
                                      LSL
                                      CCT
                                      POU
                             Concentration (ug/L)
                                    Baseline
                                     Option
                                  Incremental
 LSL
 None
                                                                          18.08
 No LSL
 None
 None
                                                                           0.82
                                                                          8,450
                                                                          6,895
                                                                         -1,555
 LSL
 None
                                                                          18.08
 LSL
 Representative
 None
                                                                           5.48
                                                                         31,482
                                                                         34,379
                                                                          2,897
 LSL
 None
                                                                          18.08
 No LSL
 Representative
 None
                                                                           0.82
                                                                              0
                                                                              1
                                                                              1
 LSL
 None
                                                                          18.08
 LSL
 None
 Yes
                                                                           0.82
                                                                              0
                                                                         14,941
                                                                         14,941
 Partial
 None
                                                                           8.43
 No LSL
 Partial
 None
                                                                           0.82
                                                                              0
                                                                          1,874
                                                                          1,874
 Partial
 None
                                                                           8.43
 Partial
 Representative
 None
                                                                           2.64
                                                                              0
                                                                          8,595
                                                                          8,595
 Partial
 None
                                                                           8.43
 No LSL
 Representative
 None
                                                                           0.82
                                                                              0
                                                                              0
                                                                              0
 Partial
 None
                                                                           8.43
 Partial
 Partial
 Yes
                                                                           0.82
                                                                              0
                                                                          3,735
                                                                          3,735
 No LSL
 None
                                                                           0.82
 No LSL
 Representative
 None
                                                                           0.82
                                                                      4,250,688
                                                                      3,675,454
                                                                       -575,234
 No LSL
 None
                                                                           0.82
 No LSL
 None
 Yes
                                                                           0.82
                                                                              0
                                                                        496,093
                                                                        496,093
 LSL
 Partial
                                                                           9.92
 No LSL
 Partial
 No
                                                                           0.82
                                                                        132,648
                                                                        934,467
                                                                        801,820
 LSL
 Partial
                                                                           9.92
 LSL
 Representative
 None
                                                                           5.48
                                                                        610,584
                                                                      6,716,410
                                                                      6,105,826
 LSL
 Partial
                                                                           9.92
 No LSL
 Representative
 None
                                                                           0.82
                                                                              0
                                                                        181,779
                                                                        181,779
 LSL
 Partial
                                                                           9.92
 LSL
 Partial
 Yes
                                                                           0.82
                                                                              0
                                                                        135,027
                                                                        135,027
 Partial
 Partial
                                                                           4.72
 No LSL
 Partial
 No
                                                                           0.82
                                                                        219,833
                                                                        226,360
                                                                          6,527
 Partial
 Partial
                                                                           4.72
 Partial
 Representative
 None
                                                                           2.64
                                                                        980,129
                                                                      1,670,537
                                                                        690,408
 Partial
 Partial
                                                                           4.72
 No LSL
 Representative
 None
                                                                           0.82
                                                                              0
                                                                         45,438
                                                                         45,438
 Partial
 Partial
                                                                           4.72
 Partial
 Partial
 Yes
                                                                           0.82
                                                                              0
                                                                         31,656
                                                                         31,656
 No LSL
 Partial
                                                                           0.82
 No LSL
 Representative
 None
                                                                           0.82
                                                                     16,034,874
                                                                     61,039,398
                                                                     45,004,523
 No LSL
 Partial
                                                                           0.82
 No LSL
 Partial
 Yes
                                                                           0.82
                                                                              0
                                                                         89,077
                                                                         89,077
 LSL
 Representative
                                                                           5.48
 No LSL
 Representative
 None
                                                                           0.82
                                                                              0
                                                                        281,271
                                                                        281,271
 LSL
 Representative
                                                                           5.48
 LSL
 Representative
 Yes
                                                                           0.82
                                                                              0
                                                                              0
                                                                              0
 Partial
 Representative
                                                                           2.64
 Partial
 Representative
 Yes
                                                                           0.82
                                                                              0
                                                                              0
                                                                              0
 No LSL
 Representative
                                                                           0.82
 No LSL
 Representative
 Yes
                                                                           0.82
                                                                              0
                                                                              0
                                                                              0
Note: This exhibit summarizes the number of people who move from one treatment combination (i.e., beginning condition) to another (i.e., ending condition) over the 35-year analysis period across all modeled PWSs in the SafeWater LCR model.

Quantification and Monetization of Children's Benefits from Reductions in Lead Drinking Water Concentrations
EPA assessed benefits of the final LCRR in terms of avoided losses in IQ in children that result from additional actions required under the final rule. Section 6.4.1 describes methods used to estimate BLLs in children, which are presented in Section 6.4.2. Concentration-response functions used to estimate changes in IQ are described in Section 6.4.3 and Section 6.4.4 outlines methods used for valuation of these effects on children's IQ. Lastly, estimates of the benefits of the LCRR in children are presented in Section 6.4.6. Appendix G presents sensitivity analyses of the IQ benefits in children. These sensitivity analyses explore alternative blood modeling assumptions, concentration-response functions, and the estimates for the value of an IQ point. Appendix I presents potential methods for quantifying 1) decreases in cases of attention deficit hyperactivity disorder (ADHD) based on reduced BLLs in children ages 8 to 15, and 2) avoided reductions in birth weight based on reduced maternal BLLs. These methods have not undergone extensive peer review and have therefore not been quantified or monetized as part of the primary benefits assessment of the final rule.
Methods for Estimating Blood Lead Levels in Children
Estimating benefits of the final LCRR in children requires estimates of BLLs from ages 0 to 7. Specifically, to estimate the effects of lead exposures on IQ, estimates of BLLs in each year of life and lifetime BLLs for each year of life from ages 0 to 7 are needed.
The Agency compiled available environmental lead concentration data across various media (i.e., soil, air, food, and water). The lead concentration estimates for soil, air, and food in this analysis are held constant in the blood lead modeling in order to represent background lead levels, with the only varying concentration being drinking water. In order to estimate the potential changes in BLLs that result from the LCRR requirements, EPA used several modeled/estimated drinking water lead concentration values associated with drinking water system scenarios that represent possible combinations of CCT and LSL status, as described in Section 6.3 above and Exhibit 6-12. The Stochastic Human Exposure and Dose Simulation (SHEDS)-Multimedia model, using environmental lead concentration data available across various media and modeled/estimated drinking water lead concentrations from the drinking water system scenarios, generated estimates of daily lead intakes (in ug/day), or exposures, from various environmental media for each year of life. Next, EPA used the estimated lead intakes/exposures from each environmental medium multiplied by applicable absorption factors (e.g., ingestion and inhalation) and summed them to estimate the total daily available lead uptake. Lastly, EPA derived regression equations from the Integrated Exposure Uptake Biokinetic (IEUBK) model and used them to relate total lead absorbed into the body to a set of BLLs representing the different CCT and LSL scenarios.
This section begins with an overview of the two models, followed by a detailed description of the methods for coupling the models.
SHEDS-Multimedia Modeling
SHEDS-Multimedia is a probabilistic model that simulates aggregate (i.e., multimedia) and cumulative population exposures to chemicals over space and time based on realistic activity patterns, concentration distributions, and exposure factors (Zartarian et al., 2006, 2012; Xue et al., 2010, 2012a, 2012b, 2014a, 2014b; Glen et al., 2012; USEPA, 2016).
The SHEDS-Multimedia model has undergone numerous peer reviews and has been well-validated for use in assessing exposures to diverse chemicals (USEPA, 2016). SHEDS-Multimedia provides exposure estimates as a result of both dietary and residential exposures, and it can be used to estimate these exposures by sex and age. SHEDS-Multimedia has the capability to assess exposures via ingestion, inhalation, and dermal pathways. However, dermal exposures are not considered in the current analysis because lead exposures through this pathway are assumed to be negligible.
Inputs to the model are the concentrations of the chemical(s) of interest in various media and human behavior data from EPA's Consolidated Human Activity Database (CHAD) and the Centers for Disease Control and Prevention's (CDC's) National Health and Nutrition Examination Survey (NHANES) (CDC, 2014). SHEDS-Multimedia first uses individual time-activity diaries from CDC's NHANES and EPA's CHAD for the specified population of interest to simulate longitudinal activity diaries. Information from these diaries is then combined with relevant input distributions (e.g., outdoor air lead concentrations, inhalation rates) to estimate exposure. For example, drinking water consumption values (see Section <IP_ADDRESS>) were obtained from 2005 to 2012 NHANES. These values represent direct and indirect (e.g., tea, infant formula) consumption of public water system water but do not include bottled water. Within the SHEDS-Multimedia program, for any modeled individual on a given day, one person with drinking water information was randomly selected from the NHANES data pool based on similar socioeconomic characteristics (i.e., age, sex) and drinking water exposure was simulated. For detailed information on other default values in SHEDS-Multimedia, please refer to the technical guidance document for the model (Zartarian et al., 2008). Outputs of the model are distributions of exposures in the specified population(s) of interest. Exhibit 6-15 provides an overview of the SHEDS-Multimedia methodology.
Exhibit 6-15: Overview of SHEDS-Multimedia Methodology

SHEDS-Multimedia has several strengths that make it a powerful tool to assess chemical exposures, such as the ability to consider correlated inputs (e.g., correlations between concentrations of contaminants in dust and soil); and the use of two-stage Monte Carlo sampling, which allows variability in population exposure and dose estimates, and uncertainty associated with different percentiles to be quantified.
IEUBK Model
The IEUBK model was developed as a simulation tool to predict BLLs in children from birth up to age 7 and thereby assist in the risk assessment of contaminated sites (USEPA, 1994). The model is intended to "enable rapid calculations and recalculations of an extremely complex set of equations that includes scores of exposure, uptake, and biokinetic parameters" (USEPA, 1994, p. 1-1). It provides an estimate of the BLL for a population of similarly exposed children associated with specified concentrations of lead in media (e.g., water, soil) in the child's environment (USEPA, 2007). In addition, the IEUBK model estimates the probability that a population of similarly exposed children with a given exposure scenario will have a BLL greater than a specified level. Users can modify inputs and assumptions within the model (e.g., concentrations of lead in environmental media, intake rates for environmental media) to explore the effects on children's BLLs. An overview of the model is presented in Exhibit 6-16.
Exhibit 6-16: Structure of the IEUBK Model for Lead in Children

          GI = gastrointestinal.
                Source: USEPA, 1994.
The IEUBK model uses four main components to mathematically and statistically link environmental lead exposure to children's BLLs: exposure, uptake, biokinetics, and variability (White et al., 1998). Exposures are quantified by combining information on the concentration of lead in environmental media, the amount of contact with the media (e.g., amount of drinking water ingested per day), and the duration of the contact (e.g., number of days) (White et al., 1998). The environmental media included in the IEUBK model are drinking water, soil, household dust, air, and food; exposure to leaded paint is assessed via its contribution to household dust and soil concentrations (White et al., 1998). The uptake component models the transfer of lead to the bloodstream (i.e., the absorption) after intake into the child's body via inhalation or ingestion routes. In the present analysis, EPA used information from the IEUBK model on uptake and biokinetics only, as further described below in the SHEDS-IEUBK coupling section.
Background Lead Exposure Inputs into SHEDS
Exhibit 6-17 to 6-20 provide a summary of the main inputs for the SHEDS-IEUBK analyses, which were previously published in the supplemental material of Zartarian et al. (2017). The estimates for daily water consumption are used in conjunction with the set of drinking water system scenario modeled lead concentrations in Exhibit 6-12. The other levels, such as daily lead from food, dust, and soil are used as background and do not change across drinking water system scenarios. While the distributions are summarized in these tables, the full distribution of data (all the data points) are imputed into the SHEDS-Multimedia model, allowing for the full range of available data to be included in the modeling. BLLs are estimated for each drinking water system scenario modeled.
Exhibit 6-17: Summary of Daily Water Consumption Inputs for Drinking Water Consumption in SHEDS-IEUBK Coupling (Zartarian et al., 2017)
                       Daily Water Consumption (mL/day)
                              NHANESa 2005 - 2012
                                  Age (years)
                                Age (months)[b]
                                       N
                                     Mean
                                      SD
                               50[th] Percentile
                                Geometric Mean
                                 Geometric SD
                               75[th] Percentile
                               95[th] Percentile
                               99[th] Percentile
                                   06 months
                                   0 - 6[c]
                                     1,246
                                      662
                                      320
                                      630
                                      526
                                      2.5
                                      854
                                     1,216
                                     1,481
                                       0
                                   0 - 11[c]
                                     2,618
                                      581
                                      349
                                      532
                                      410
                                      3.0
                                      806
                                     1,172
                                     1,489
                                       1
                                    12 - 23
                                     1,792
                                      247
                                      247
                                      219
                                      151
                                      3.3
                                      306
                                      690
                                     1,148
                                       2
                                    24 - 35
                                     1,948
                                      300
                                      312
                                      251
                                      176
                                      3.4
                                      360
                                      909
                                     1,424
                                       3
                                    36 - 47
                                     1,272
                                      316
                                      313
                                      257
                                      193
                                      3.1
                                      398
                                      917
                                     1,640
                                       4
                                    48 - 59
                                     1,358
                                      320
                                      333
                                      261
                                      197
                                      3.2
                                      404
                                      874
                                     1,434
                                       5
                                    60 - 71
                                     1,196
                                      364
                                      366
                                      303
                                      213
                                      3.5
                                      447
                                     1,037
                                     1,802
                                       6
                                    72 - 83
                                     1,306
                                      377
                                      353
                                      332
                                      228
                                      3.5
                                      480
                                     1,067
                                     1,601
Note: This exhibit summarizes drinking water consumption values that were used as inputs for the SHEDS-IEUBK analysis. These values were previously published in the supplemental material of Zartarian et al. (2017).
N = number of observations, and SD = standard deviation.
[a] The National Health and Nutrition Examination Survey (NHANES) is a program of studies designed to assess the health and nutritional status of adults and children in the United States. It provides nationally representative data on the United States population, including estimates of drinking water consumption.
b Age in months was added to clarify the age ranges listed in years.
[c] Water consumption for 0 - 11 months was used in the modeling for 6 - 11 month-old infants.
Exhibit 6-18: Summary of Daily Inputs for Dietary Lead Intake (μg/day) in SHEDS-IEUBK (Xue et al., 2010)
                                      Age
                                    (years)
                                Age (months)[a]
                                       N
                                     Mean
                                      SD
                                    Median
                                Geometric Mean
                                 Geometric SD
                               75[th] Percentile
                               95[th] Percentile
                               99[th] Percentile
                                   06 months
                                     0 - 6
                                     1,072
                                      0.7
                                     0.98
                                      0.3
                                     0.27
                                     4.75
                                     0.91
                                     2.71
                                     3.47
                                       1
                                    12 - 23
                                     2,226
                                     2.58
                                     1.84
                                     2.17
                                       2
                                     2.16
                                     3.41
                                     5.83
                                     7.63
                                      2
                                    24 - 35
                                     1,788
                                     3.44
                                     2.03
                                     3.06
                                     2.85
                                     1.94
                                     4.49
                                     7.23
                                     8.46
                                      3
                                    36 - 47
                                     1,160
                                     3.54
                                     2.06
                                     3.18
                                     2.98
                                     1.89
                                     4.63
                                     7.26
                                     8.43
                                      4
                                    48 - 59
                                     1,240
                                     3.57
                                     2.16
                                     3.18
                                       3
                                     1.87
                                     4.55
                                     7.25
                                     8.63
                                      5
                                    60 - 71
                                     1,066
                                     3.85
                                     2.18
                                     3.43
                                     3.31
                                     1.77
                                     4.83
                                     7.86
                                     9.52
                                      6
                                    72 - 83
                                     1,086
                                      3.8
                                     2.02
                                     3.51
                                     3.29
                                     1.76
                                     4.84
                                     7.55
                                      8.3
Notes: This exhibit summarizes dietary lead intake values that were used as inputs for the SHEDS-IEUBK analysis. These values were previously published in the supplemental material of Zartarian et al. (2017).
N = number of observations, and SD = standard deviation.
Data sources: United States Food and Drug Administration's (FDA's) Total Diet Study (TDS) 2007 - 2013 and recipe mapping data from the Center for Food Safety and Applied Nutrition (CFSAN).
Method source: Xue et al., 2010. N=Number of Observations
a Age in months was added to clarify the age ranges listed in years. Data for 6 - 11 month-old infants not available.

Exhibit 6-19: Summary of Daily Inputs for Soil and Dust Lead Concentration (ppm) in SHEDS-IEUBK Coupling (Zartarian et al., 2017)
                                     Media
                                   House Age
                                       N
                                     Mean
                                      SD
                                    Median
                                Geometric Mean
                                 Geometric SD
                                Fitted Log Mean
                              Fitted Log Mean SD
                               75[th] Percentile
                               95[th] Percentile
                               99[th] Percentile
                                     Dust
                                  Before 1950
                                      223
                                     207.7
                                     238.2
                                     113.3
                                     133.9
                                     2.47
                                     4.89
                                     0.88
                                     238.6
                                     706.6
                                    1,108.9
                                     Dust
                                  After 1950
                                      908
                                      79
                                     77.2
                                     64.5
                                     61.3
                                       2
                                     4.12
                                     0.63
                                     87.1
                                     195.3
                                     353.1
                                     Soil
                                  Before 1950
                                      193
                                     532.2
                                     912.6
                                     203.2
                                     221.1
                                     3.89
                                     5.38
                                      1.3
                                     774.5
                                    1,841.3
                                    5,793.7
                                     Soil
                                  After 1950
                                      749
                                     63.7
                                      202
                                     19.2
                                      23
                                     3.37
                                     3.18
                                     1.05
                                     39.9
                                     207.7
                                     933.3
Notes: This exhibit summarizes soil and dust lead concentration values that were used as inputs for the SHEDS-IEUBK analysis. These values were previously published in the supplemental material of Zartarian et al. (2017). Empirical distribution from the United States Department of Housing and Urban Development (HUD, 2011) American Healthy Homes Survey (AHHS) 2005 - 2006 data, http://portal.hud.gov/hudportal/documents/huddoc?id=AHHS_Report.pdf.
N = number of observations, and SD = standard deviation.
Exhibit 6-20: Summary of Daily Inputs for Soil/Dust Ingestion (mg/day) in SHEDS-IEUBK Coupling (Ozkaynak et al., 2011)
                                      Age
                                    (years)
                                Age (months)[a]
                                   Soil/Dust
                                     Mean
                                      SD
                               50[th] Percentile
                                Geometric Mean
                                 Geometric SD
                               95[th] Percentile
                              97.5[th] Percentile
                               99[th] Percentile
                                      1
                                    12 - 23
                                   mg total
                                     43.9
                                     54.8
                                     27.8
                                     26.6
                                      2.8
                                      135
                                      188
                                      262
                                      2
                                    24 - 35
                                   mg total
                                     45.2
                                     58.8
                                     25.8
                                     25.9
                                      3.0
                                      146
                                      201
                                      276
                                      3
                                    36 - 47
                                   mg total
                                     51.7
                                     64.2
                                     31.1
                                     28.9
                                      3.2
                                      168
                                      220
                                      304
                                      4
                                    48 - 59
                                   mg total
                                     57.8
                                     75.5
                                      34
                                     31.6
                                      3.2
                                      197
                                      268
                                      364
                                      5
                                    60 - 71
                                   mg total
                                     62.6
                                     79.8
                                     37.9
                                     34.4
                                      3.2
                                      204
                                      270
                                      380
                                      6
                                    72 - 83
                                   mg total
                                     54.3
                                     76.1
                                     30.4
                                     29.2
                                      3.2
                                      183
                                      252
                                      357
Notes: This exhibit summarizes soil/dust ingestion values, which were used as inputs for the SHEDS-IEUBK analysis. These values were previously published in the supplemental material of Zartarian et al. (2017) and were originally developed in Ozkaynak et al. (2011).
Data for ages 0 - 11 months were unavailable.
[a] Age in months was added to clarify the age ranges listed in years. Data for 0 - 11 month-old infants not available. Inputs for 12 - 23 month-old infants were used for 0 - 11 month-old toddlers.
SD = standard deviation.
Coupling of SHEDS-IEUBK
To estimate changes in children's BLLs as a result of the rule, EPA first used SHEDS-Multimedia to generate probabilistic estimates of lead intakes from all routes of exposure for children aged 0 to 7. In the coupling methodology, SHEDS-Multimedia takes the place of the exposure and variability components of the IEUBK model by generating a probability distribution of lead intakes (ug/day).
The distributions of inputs from SHEDS are then converted to lead uptakes by multiplying by the route-specific (e.g., inhalation, ingestion) absorption fractions, thereby accounting for the uptake component of IEUBK. The absorption fractions are summarized in Exhibit 6-21 and are the default values in IEUBK.
Exhibit 6-21: Default Lead Absorption Fractions across Media Used in SHEDS-IEUBK Model Runs
Media
Absorption Fraction
(%)
                                     Soil
                                      30
                                     Dust
                                      30
                                     Water
                                      50
                                     Diet
                                      50
                                      Air
                                      32
                  Note: This exhibit summarizes absorption fractions across media, which are the default IEUBK values.
                  Source: White et al. (1998).

Applying these absorption fractions results in distributions of lead uptake by exposure/media route, which can be summed across routes to give total lead uptake per day (ug/day). Next, EPA used age-based relationships derived from IEUBK to relate these lead uptakes (ug/day) to BLLs (ug/dL). Specifically, EPA developed regression equations between lead uptake and blood lead by running IEUBK with increasing amounts of lead intake. Since the relationship between lead uptake and blood lead in IEUBK is not perfectly linear, EPA used a polynomial regression to address the slight departures from linearity, which represent the non-linear binding of lead to red blood cells. Exhibit 6-22 shows age-specific regressions used to describe an age-dependent relationship relating lead uptake to blood lead. The coefficients pertain to a third-order polynomial regression of the form:

Blood lead (μg/dL) = 0 + 1 Uptake + 2 Uptake[2] + 3 Uptake[3] + e
                                 (Equation 6)
Coefficients for the month that represents the midpoint of the age range of interest were used in the analyses.
Exhibit 6-22: Age-Specific Polynomial Regressions Equations for Approximating IEUBK (Zartarian et al., 2017)
IEUBK Age Interval
(year)
Age
(months)[a]
β0
β1
β2
β3
                                    0.5 - 1
                                    6 - 11
                                   7.86E-03
                                   5.47E-01
                                   -1.31E-03
                                    6.01E-6
                                     1 - 2
                                    12 - 23
                                   -3.11E-04
                                   4.47E-01
                                   -6.37E-04
                                    1.53E-6
                                     2 - 3
                                    24 - 35
                                   1.23E-03
                                   3.79E-01
                                   -4.29E-04
                                    8.45E-7
                                     3 - 4
                                    36 - 47
                                   6.58E-04
                                   3.55E-01
                                   -3.71E-04
                                    6.24E-7
                                     4 - 5
                                    48 - 59
                                   6.36E-04
                                   3.36E-01
                                   -3.38E-04
                                    5.44E-7
                                     5 - 6
                                    60 - 71
                                   1.65E-03
                                   3.13E-01
                                   -2.78E-04
                                    3.57E-7
                                     6 - 7
                                    72 - 83
                                   1.32E-04
                                   2.88E-01
                                   -2.30E-04
                                    3.08E-7
Notes: R2 > 0.995. This exhibit summarizes the coefficients used for age-specific IEUBK modeling to predict BLLs.
[a] Age in months was added for consistency across input tables.

In its basic coupled form, SHEDS-IEUBK only represents exposure variability and does not consider biological variability associated with inter-individual differences in the relationship between lead exposure and blood lead. Uncoupled IEUBK applies a geometric SD of 1.6 to outputs to account for biological variability and measurement error, but because the IEUBK component of SHEDS-IEUBK has been reduced to deterministic regression equations, we are unable to apply this geometric SD to account for biological variability in our outputs. To account for this biological variability, EPA applied a biological variance correction factor of 0.185 for 1- to < 2-year-olds and 0.176 for 2- to < 7-year-olds to the predicted blood lead variance estimated by the SHEDS-IEUBK model. Additional details about the calculation of these biological variance correction factors can be found in Zartarian et al. (2017).
Exhibit 6-23 summarizes the SHEDS-IEUBK coupling method, which EPA used to develop distributions of BLLs for each scenario of exposure to lead in drinking water under the LCRR.
Exhibit 6-23: Summary of SHEDS-IEUBK Coupling

Estimates generated using the SHEDS-IEUBK coupling method were compared to BLL estimates reported from NHANES (2013 - 2014) and from the National Human Exposure Assessment Survey (NHEXAS) in Zartarian et al. (2017); and were shown to closely estimate these BLLs. For further information on SHEDS-IEUBK model development and evaluation, refer to Zartarian et al.'s (2017) paper, "Children's Lead Exposure: A Multimedia Modeling Analysis to Guide Public Health Decision-Making."
Estimates of Pre- and Post-Rule Blood Lead Levels in Children
Exhibit 6-24 presents modeled SHEDS-IEUBK geometric mean BLLs in children by year of life. The BLLs in this exhibit represent what children's BLLs would be if they lived under the corresponding drinking water system scenario for their entire lives from birth to age 7. These BLLs are used as inputs for the representative children in each corresponding PWS for the benefits modeling, and do not represent weighted population estimates. In the SafeWater LCR model analyses of benefits, EPA estimated lifetime BLLs from these values by taking the average of the BLLs for each year of the child's life, up to age 7, based on their drinking water system scenario status during each year. The age at implementation of the rule was taken into account when calculating lifetime average BLLs. If, for example, the child is age 3 at implementation of the rule, EPA would calculate lifetime average BLLs by averaging 3 years of pre-rule BLLs and 4 years of post-rule BLLs. Or, if the child is age 5 at implementation of the rule, EPA would calculate lifetime average BLLs by averaging 5 years of pre-rule BLLs and 2 years of post-rule BLLs. The column labeled "Average" contains calculated average lifetime BLLs, assuming a child lived in the corresponding LSL/CCT scenario for their entire life.
Exhibit 6-24: Modeled SHEDS-IEUBK Geometric Mean Blood Lead Levels in Children for Each Possible Drinking Water Lead Exposure Scenario for Each Year of Life
                                  LSL Status
                                  CCT Status
    Geometric Mean Blood Lead Level (ug/dL)[a] for Specified Year of Life

                                   0 - 1[b]
                                     1 - 2
                                     2 - 3
                                     3 - 4
                                     4 - 5
                                     5 - 6
                                     6 - 7
                                  Average[c]
LSL
None
                                     3.61
                                     2.47
                                     2.65
                                     2.47
                                     2.48
                                     2.66
                                     2.34
                                     2.67
Partial
None
                                     2.35
                                     1.83
                                     1.88
                                     1.81
                                     1.81
                                     1.88
                                     1.65
                                     1.89
No LSL
None
                                     0.97
                                     1.14
                                     1.18
                                     1.15
                                     1.14
                                     1.19
                                     0.98
                                     1.11
LSL
Partial
                                     2.57
                                     1.93
                                     2.05
                                     1.95
                                     1.94
                                     2.03
                                     1.76
                                     2.03
Partial
Partial
                                     1.72
                                     1.52
                                     1.57
                                     1.54
                                     1.51
                                     1.58
                                     1.37
                                     1.54
No LSL
Partial
                                     0.97
                                     1.14
                                     1.18
                                     1.15
                                     1.14
                                     1.19
                                     0.98
                                     1.11
LSL
Representative
                                     1.85
                                     1.57
                                     1.64
                                     1.60
                                     1.57
                                     1.63
                                     1.43
                                     1.62
Partial
Representative
                                     1.36
                                     1.33
                                     1.36
                                     1.34
                                     1.32
                                     1.37
                                     1.19
                                     1.32
No LSL
Representative
                                     0.97
                                     1.14
                                     1.18
                                     1.15
                                     1.14
                                     1.19
                                     0.98
                                     1.11
POU
                                     0.97
                                     1.14
                                     1.18
                                     1.15
                                     1.14
                                     1.19
                                     0.98
                                     1.11
Notes: This table presents modeled SHEDS-IEUBK BLLs in children by year of life and lifetime average.
[a] The geometric mean BLLs are used to represent the BLL for a child living with the LSL/CCT status in the first two columns of the exhibit. The BLL for each year of age corresponding to a representative child is summed and divided by seven in the model to estimate the lifetime average BLL.
b Due to lack of available data, BLLs for the first year of life are based on regression from IEUBK for 0.5- to 1-year-olds only.
[c] This column contains calculated average lifetime BLLs, assuming a representative child lived in the corresponding LSL/CCT scenario for their entire life.
Concentration-Response Functions for Lead and Changes in IQ
To estimate avoided IQ loss in children, EPA selected a concentration-response function from a study by Crump et al. (2013). This study used data from a 2005 paper by Lanphear et al. (2005) that has formed the basis of concentration-response functions used in several regulations. EPA explored the choice of two additional IQ functions in the sensitivity analysis presented in Appendix G, both using the corrected Lanphear et al. (2005) function, as reported in Kirrane and Patel (2014): one with a low-dose linearization and the other without a low-dose linearization.
This section provides an overview of these two key studies, as well as the rationale for selection of the concentration-response function from Crump et al. (2013). Additional details of Crump et al. (2013) and Lanphear et al. erratum (2019) can be found in Appendix J, which provides more in-depth summaries of the key studies used in the concentration-response functions for the benefits analysis, as well as the Kirrane and Patel (2014) correction to the Lanphear et al. (2005) results.
Lanphear et al. erratum (2019) conducted a pooled analysis of seven international cohort studies that investigated the relationship between BLLs and full-scale IQ (the composite of verbal and performance IQ scores) in children 5 - 10 years old. The pooled study sample comprised 1,333 children, with a lifetime average BLL of 12.4 ug/dL. All the children underwent IQ testing with the Wechsler Intelligence Scale for Children. The mean IQ in the study sample was approximately 93 points. Associations between IQ and four different measures of BLLs in children were examined: concurrent (measurement obtained closest to the IQ test), maximum (peak value at any time before the IQ test), early (mean BLL from 6 to 24 months of age), and lifetime (mean BLL from 6 months of age to concurrent). For each of these measures, Lanphear et al. erratum (2019) estimated the relationship between BLLs and IQ by constructing an adjusted log-linear model.
Results of the Lanphear et al. erratum (2019) study showed that all blood lead measures were significantly associated with IQ loss, and were highly correlated with one another. Based on the R[2] values for each regression model (data not presented in the paper), Lanphear et al. erratum (2019) determined that concurrent BLLs were the strongest predictors of IQ, followed by lifetime average BLLs. Changes in IQ associated with changes in BLLs were estimated using Equation 7 below.

                           IQ Loss= βx lnPbB1PbB2
                                 (Equation 7)

Where:
	β 	=	Beta estimate from Lanphear et al. (2005)
	PbB1 	= 	Pre-rule BLL
	PbB2 	= 	Post-rule BLL
Exhibit 6-25 shows the beta estimates for the log-linear associations between each of the blood lead measures examined in Lanphear et al. erratum (2019). The estimated decreases in IQ associated with increases in concurrent BLLs from 2.4 to 10 ug/dL, 10 to 20 ug/dL, and 20 to 30 ug/dL were 3.8, 1.8, and 1.1 points, respectively. Consistent with the log-linear model, IQ deficits were greater at lower levels of lead exposures.
In their 2013 paper, Crump et al. had two aims: 1) to perform a reanalysis of the methods in Lanphear et al. (2005), and 2) to conduct an independent analysis of the data from Lanphear et al. (2005). In the reanalysis, Crump et al. (2013) identified a few minor errors in the original Lanphear et al. (2005) paper. The correction of these minor errors resulted in slight changes to the regression coefficients but did not affect the main conclusions of the paper. These errors were confirmed by EPA in a reanalysis by Kirrane and Patel (2014), which also reaffirmed that the main conclusions of Lanphear et al. (2005) remained unchanged, and Lanphear et al. erratum (2019) confirmed this in an Erratum of the original study. Kirrane and Patel (2014) additionally found that the early childhood blood lead measure had the highest R[2] value, though all R[2] values were similar.

In their independent analysis, Crump et al. (2013) made changes to the dataset used for final analysis (e.g., in selecting IQ measurements and defining blood lead measurements). Additionally, the authors opted to add 1 to BLLs before log-transformation so that IQ loss was equal to 0 when BLL was 0, as shown in Equation 8.

                         IQ Loss= βx lnPbB1+1PbB2 +1
                                 (Equation 8)
Where:
      β 	=	Beta estimate from Crump et al. (2013) independent analysis
      PbB1 	= 	Pre-rule BLL
	PbB2 	= 	Post-rule BLL
Exhibit 6-25 displays the regression coefficients and R[2] values for the Lanphear et al. erratum (2019), the Crump et al. (2013) and Kirrane and Patel (2014) reanalysis of Lanphear et al. (2005), and the Crump et al. (2013) independent analysis.
Exhibit 6-25: Comparison of Adjusted Coefficients from Lanphear et al. Erratum (2019) with Those Obtained in the Kirrane and Patel (2014) Reanalysis and Independent Analysis of Lanphear et al. (2005) by Crump et al. (2013)
BLL Variable
Kirrane and Patel (2014)
Lanphear et al. Erratum (2019)
Crump et al. (2013) Reanalysis ln(BLL)
Crump et al. (2013) Independent Analysis ln(BLL + 1)

β
(95% CI)
R2
β
(95% CI)
R[2][a]
β
(95% CI)
R[2]
β
(95% CI)
R[2]
                                     Early
                             -2.21 (-3.38, -1.04)
                                     0.643
                             -2.21 (-3.38, -1.04)
                                      n/a
                             -2.21 (-3.38, -1.03)
                                     0.643
                             -2.46 (-3.82, -1.10)
                                     0.659
                                     Peak
                             -2.86 (-4.10, -1.61)
                                     0.640
                             -2.86 (-4.10, -1.61)
                                      n/a
                             -2.86 (-4.10, -1.61)
                                     0.640
                             -2.48 (-3.83, -1.14)
                                     0.656
                                   Lifetime
                             -3.14 (-4.39, -1.88)
                                     0.641
                             -3.25 (-4.51, -1.99)
                                      n/a
                             -3.19 (-4.45, -1.94)
                                     0.641
                             -3.25 (-4.66, -1.83)
                                     0.659
                                  Concurrent
                             -2.65 (-3.69, -1.61)
                                     0.641
                             -2.65 (-3.69, -1.61)
                                      n/a
                             -2.65 (-3.69, -1.61)
                                     0.641
                             -3.32 (-4.55, -2.08)
                                     0.658
Notes: This table displays regression coefficients and R[2] values for the Lanphear et al. erratum (2019) analysis, the Crump et al. (2013) and Kirrane and Patel (2014) reanalysis of Lanphear et al. (2005), and the Crump et al. (2013) independent analysis of Lanphear et al. (2005). This table summarizes the relationship between BLL and IQ loss across various blood lead metrics.
Sources: Crump et al. (2013, Table 2 and Table 5), Kirrane and Patel (2014, Table 1), Lanphear et al. erratum (2019, Table 4).
a R[2] not reported in Lanphear et al. erratum (2019); however, the paper reported that the concurrent BLL was the largest R[2].
As can be seen in Exhibit 6-25, the R[2] values are all similar: the strength of the relationship between BLLs and IQ loss appears to be similar regardless of the blood lead metric used. Because lifetime average BLLs are more reflective of the long-term changes in lead exposure anticipated under the LCRR, EPA chose to model the benefits based on lifetime BLLs rather than concurrent BLLs. Lifetime BLLs also reflect varied BLLs over the representative child's life in the benefits analysis.
To estimate the benefits of the LCRR, EPA used the concentration-response function based on lifetime BLLs from the independent analysis by Crump et al. (2013) in the main analysis. EPA selected this function over the Lanphear et al. (2005) reanalysis reported in Kirrane and Patel (2014) and confirmed in the Lanphear et al. erratum (2019). This function was selected to minimize issues with overestimating predicted IQ loss at the lowest levels of lead exposure (less than 1 ug/dL), which is a result of the use of the log-linear function (the log of zero is undefined). The Crump et al. (2013) function avoids this issue by adding 1 to the estimated BLLs before log-transformation. Since the LCRR is expected to reduce chronic exposures to lead, EPA selected lifetime BLLs as the most appropriate measure with which to evaluate benefits. No threshold has been identified for the neurological effects of lead (Schwartz and Otto, 1991; Budtz-Jørgensen et al., 2013; Crump et al., 2013; USEPA, 2013). Therefore, EPA assumes that there is no threshold for this endpoint and quantified avoided IQ loss associated with all BLLs (Schwartz and Otto, 1991; Budtz-Jørgensen et al., 2013; Crump et al., 2013; USEPA, 2013). Budtz-Jørgensen et al. (2013), as well as the smaller cohort study of Min et al. (2009), used more recent BLLs than those used in the Crump and Lanphear analyses, and confirmed the results in Crump et al. (2013) and Lanphear et al. erratum (2019). Additionally, in Min et al. (2009), the steeper slopes at lower BLLs without log-transformation show increased deficits, which provides additional evidence that reducing lead levels in the lower range of average BLLs has a significant impact on preventing IQ loss.
EPA explored the choice of two additional IQ functions in the sensitivity analyses, which were based on Lanphear et al. erratum (2019), and similar to those from the quantitative risk assessment in support of the 2008 review of the United States National Ambient Air Quality Standards (NAAQS) for lead (USEPA, 2007). These functions and alternative benefits calculations are presented in Appendix G.
Exhibit 6-26 displays the avoided IQ loss per representative child associated with BLLs at the geometric mean, the 25[th] percentile, and the 75[th] percentile. This calculation assumes the representative child spends their lifetime from birth to age 7 either in the pre-rule water conditions or the post-rule water conditions in the same row. Observe that when "No LSL" is the beginning or post-rule state, 0.82 μg/L is the assumed concentration across all levels of CCT status (i.e., none, partial, representative). The extent to which changes in CCT status make a meaningful difference in lead concentrations for those without LSL cannot be determined from this exhibit.
Exhibit 6-26: Avoided IQ Loss per Child Associated with the Concentration-Response Function from Crump et al. (2013) and Additional Blood Lead Estimates
                            Pre-Rule Drinking Water
                           Post-Rule Drinking Water
        Avoided IQ Loss per Child Associated with Specified BLL Change
                              Lead Conc. (ug/L)
                                  LSL Status
                                  CCT Status
                              Lead Conc. (ug/L)
                                  LSL Status
                                  CCT Status
                                Geometric Mean
                               25[th] Percentile
                               75[th] Percentile
                                     18.08
                                      LSL
                                     None
                                     0.82
                                    No LSL
                                     None
                                     1.80
                                     1.36
                                     2.40
                                     18.08
                                      LSL
                                     None
                                     5.48
                                      LSL
                                Representative
                                     1.10
                                     0.83
                                     1.45
                                     18.08
                                      LSL
                                     None
                                     0.82
                                    No LSL
                                Representative
                                     1.80
                                     1.36
                                     2.40
                                     18.08
                                      LSL
                                     None
                                     0.82
                                      POU
                                     1.80
                                     1.36
                                     2.40
                                     8.43
                                    Partial
                                     None
                                     0.82
                                    No LSL
                                     None
                                     1.02
                                     0.77
                                     1.37
                                     8.43
                                    Partial
                                     None
                                     2.64
                                    Partial
                                Representative
                                     0.70
                                     0.51
                                     0.97
                                     8.43
                                    Partial
                                     None
                                     0.82
                                    No LSL
                                Representative
                                     1.02
                                     0.77
                                     1.37
                                     8.43
                                    Partial
                                     None
                                     0.82
                                      POU
                                     1.02
                                     0.77
                                     1.37
                                     0.82
                                    No LSL
                                     None
                                     0.82
                                    No LSL
                                Representative
                                     0.00
                                     0.00
                                     0.00
                                     0.82
                                    No LSL
                                     None
                                     0.82
                                      POU
                                     0.00
                                     0.00
                                     0.00
                                     9.92
                                      LSL
                                    Partial
                                     0.82
                                    No LSL
                                    Partial
                                     1.18
                                     0.88
                                     1.61
                                     9.92
                                      LSL
                                    Partial
                                     5.48
                                      LSL
                                Representative
                                     0.48
                                     0.35
                                     0.66