Inequalities in Public Water Arsenic Concentrations in Counties and Community

Overview

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Key numbers

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• METHODS: We estimated 3-y average arsenic concentrations for 36,406 CWSs (98%) and 2,740 counties (87%) and compared differences in means
• RESULTS: From 2006–2008 to 2009–2011, mean and 95th percentile CWS arsenic (in micrograms per liter) declined by 10.3% (95% CI: 6.5%, 14.1%)
• (61.1%), served by groundwater (94.7%), serving smaller populations (mean 1,102 persons), and serving Hispanic communities (38.3%).
• (Awata et al. 2017a, 2017b; Cubadda et al. 2017; Jones et al. from Wisconsin and West Virginia that likely reported LODs in
• water arsenic exposure for sociodemographic and geographic ter), we imputed the corrected LOD divided by the square root of 2
• States, to inform future national- and state-level arsenic MCL the value of 0:35 lg=L (the U.S. EPA LOD of 0:5 lg=L divided
• arsenic-related disease. remaining 5,437 records for which LODs were reported as
• following subgroups in our analysis: a) U.S. region (CWS and sion criteria). The final sample size included 36,406 CWSs (98%
• county level); b) sociodemographic county cluster (CWS and of CWSs in the SYR3) serving a total of 2,740 counties (87% of
• Collection Request process (voluntarily sent in from states, territo- and varied substantially across CWSs (range: 1–1,506; mean: 4)
• period (2006–2011), which included approximately 13 million ana- alytical decision, see Tables S1 and S2). Few CWSs reported
• lion people annually. Data from 46 states, Washington DC, the the same year (N = 1,182). When the 3-y average of arsenic in fin-
• 1, 4, 5, 8, and 9, representing 95% of all public water systems and (N = 336 CWSs), we calculated the 3-y average with only the fin-
• 92% of the total population served by public water systems nation- ished water samples.
• nondetections. CWSs serving that county reported serving at least 50% or more of
• with the LOD divided by the square root of 2. Although the U.S. mated the public water–reliant population for each county using the
• reported lower and higher LODs or did not report record-specific tap water source from the 1990 U.S. Census (Ruggles et al. 2019),
• LODs. When records reported the laboratory LOD as <5 lg=L, which was also recently used by the U.S. Geologic Survey (USGS)
• we replaced arsenic values below the LOD with the LOD divided (Ayotte et al. 2017). For descriptive purposes, we also calculated
• by the square root of 2 (N = 30,256 records); for 1,202 records county-level 6-y average water arsenic concentrations as the
• county-level estimates of water arsenic averages across the conter- root of 2), regardless of the LOD reported in each record.
• minous United States using the maps package in R version 3.5.3 Second, we excluded records with a reported LOD of ≥5 lg=L.
• Statistical Analysis: Water Arsenic Exposure Estimates reported serving at least 70% and 80% or more of the public
• (N = 36,406) and county level (N = 2,740) for the entire United We assigned all CWSs and counties to one of four MCL compli-
• States. We also compared mean differences between the two time ance categories using the 10 lg=L MCL cut point based on the
• clusters (N = 8 distinct clusters) were derived by Wallace et al. age arsenic concentrations at the CWS and county level and a re-
• sociodemographic county-clusters to identify characteristics of pop- Nationwide, the mean CWS arsenic concentrations (95% confi-
• sure. These sociodemographic county-clusters are as follows: Semi- 1:89 lg=L (95% CI: 1.84, 1.94) and 1:7 lg=L (95% CI: 1.64,
• Hispanic; Mostly Rural, Mid SES; Rural, Mid/Low SES; Young, sponding percentage decrease = 10:1% (95% CI: 14.1%, 6.5%)
• Urban, Mid/High SES; Rural, American Indian; and Rural, High (Table 1)). By region, CWS arsenic concentrations for the first
• (groundwater vs. surface water, as reported in SDWIS) and by the (mean = 3:59 lg=L (95% CI: 3.41, 3.76)), followed by Alaska/
• We conducted sensitivity analyses for the comparison of Eastern Midwest (mean = 2:03 lg=L (95% CI: 1.92, 2.14)) (Table 1;
• Table 1. Arithmetic means (95% CIs), mean differences (95% CIs), and corresponding percentage differences (95% CIs) of 3-y average water arsenic concen-
• trations (lg=L) in community water systems (CWSs) from 2006–2008 and 2009–2011, stratified by CWS subgroup (total N = 36,406 CWSs).
• graphic county-cluster analyses (N = 36,674).
• 2006–2008 and 2009–2011 (mean difference = − 0:75 lg=L (95% corresponding percentage decrease = 45:3%), the Eastern Midwest
• CI: −1:35, −0:15); corresponding percentage decrease = 36:8% (decline of 8:44 lg=L (95% CI: 11.83, 5.05); corresponding
• (95% CI: 7.4%, 66.1%)), followed by the Southwest (mean percentage decrease = 40:5%), the Southwest (decline of 3:46 lg=L
• difference = − 0:41 lg=L (95% CI: −0:65, −0:17); corresponding (95% CI: 9.00, 2.08); corresponding percentage decrease = 11:5%),
• percentage decrease = 11:4% (95% CI: 4.7%, 18.1%)); and Eastern and the Mid-Atlantic (decline of 2:43 lg=L (95% CI: 4.46, 0.40); cor-
• Midwest (mean difference = − 0:40 lg=L (95% CI: −0:54, responding percentage decrease = 23:1%) (Figure 2; Table S5).
• −0:25); corresponding percentage decrease = 19:7% (95% CI: At the county level, nationwide weighted average water ar-

Methods (brief)

• (Awata et al. 2017a, 2017b; Cubadda et al. 2017; Jones et al. from Wisconsin and West Virginia that likely reported LODs in
• water arsenic exposure for sociodemographic and geographic ter), we imputed the corrected LOD divided by the square root of 2
• States, to inform future national- and state-level arsenic MCL the value of 0:35 lg=L (the U.S. EPA LOD of 0:5 lg=L divided
• water arsenic exposure by subgroup contributes to disparities in reported below the LOD without record-specific LOD; and b) the
• arsenic-related disease. remaining 5,437 records for which LODs were reported as
• following subgroups in our analysis: a) U.S. region (CWS and sion criteria). The final sample size included 36,406 CWSs (98%
• lytical records from 139,000 public water systems serving 290 mil- records of both raw and finished (i.e., treated) water samples within
• Navajo Nation, and American Indian tribes from U.S. EPA Regions ished water samples was lower than in raw concentrations
• 92% of the total population served by public water systems nation- ished water samples.
• We replaced arsenic values below the limit of detection (LOD) the public water–reliant population in the entire county. We esti-
• with the LOD divided by the square root of 2. Although the U.S. mated the public water–reliant population for each county using the
• EPA established the maximum LOD of 0:5 lg=L, many systems latest nationwide U.S. Census statistic on county-level household
• reported lower and higher LODs or did not report record-specific tap water source from the 1990 U.S. Census (Ruggles et al. 2019),
• LODs. When records reported the laboratory LOD as <5 lg=L, which was also recently used by the U.S. Geologic Survey (USGS)
• we replaced arsenic values below the LOD with the LOD divided (Ayotte et al. 2017). For descriptive purposes, we also calculated
• average of the two 3-y period estimations. We mapped 3- and 6-y 0:35 lg=L (the standard U.S. EPA LOD divided by the square
• county-level estimates of water arsenic averages across the conter- root of 2), regardless of the LOD reported in each record.
• minous United States using the maps package in R version 3.5.3 Second, we excluded records with a reported LOD of ≥5 lg=L.

Implications

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Wiki pages this source may touch

• Fish — marine, non-predatory (sardines, anchovies, salmon, cod)
• Mercury
• Cadmium
• Lead
• Arsenic

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