DESPIKING HIGH-RESOLUTION ADCP DATA

Abstract

Background: Few studies of environmental justice examine inequities indrinking water contamination. Those studies that have done so usuallyanalyze either disparities in exposure/harm or inequitableimplementation of environmental policies. The US EPA's 2001 RevisedArsenic Rule, which tightened the drinking water standard for arsenicfrom 50 mu g/L to 10 mu g/L, offers an opportunity to analyze bothaspects of environmental justice.Methods: We hypothesized that Community Water Systems (CWSs) serving ahigher proportion of minority residents or residents of lowersocioeconomic status (SES) have higher drinking water arsenic levels andhigher odds of non-compliance with the revised standard. Using waterquality sampling data for arsenic and maximum contaminant level (MCL)violation data for 464 CWSs actively operating from 2005-2007 inCalifornia's San Joaquin Valley we ran bivariate tests and linearregression models.Results: Higher home ownership rate was associated with lower arseniclevels (beta-coefficient = -0.27 mu g As/L, 95% (CI), -0.5, -0.05).This relationship was stronger in smaller systems (beta-coefficient =-0.43, CI, -0.84, -0.03). CWSs with higher rates of homeownership hadlower odds of receiving an MCL violation (OR, 0.33; 95% CI, 0.16,0.67); those serving higher percentages of minorities had higher odds(OR, 2.6; 95% CI, 1.2, 5.4) of an MCL violation.Conclusions: We found that higher arsenic levels and higher odds ofreceiving an MCL violation were most common in CWSs servingpredominantly socio-economically disadvantaged communities. Our findingssuggest that communities with greater proportions of low SES residentsnot only face disproportionate arsenic exposures, but unequal MCLcompliance challenges.