The coefficient for the state dummy will then indicate the average propensity for water quality violations being reported in a state due to either water quality violations or enforcement effort. State-level enforcement can differ due to variation in sampling protocols, technical capacity, and financial resources. Meanwhile, controlling for state-level effects is important because the SDWA is enforced primarily at the state level. Year dummy variables control for changes in federal regulations or compliance over time. The model includes dummy variables for each year ( T t) and state ( S k). Each water supplier i is associated with a county j and state k. The probability of a CWS having a violation is estimated as a function of time-invariant water supplier characteristics ( x i) and county-level community characteristics ( C jt) for county j in year t. Where y it is a binary indicator of violation occurrence for water supplier i in year t. The study found that private ownership does not generally affect compliance. Meanwhile, Wallsten and Kosec ( 9) develop count regressions that relate community and water system characteristics to SDWA violations from 1997 to 2003. However, given that only summary statistics are presented, results do not isolate the association between violations and specific utility characteristics. A key finding is that similar proportions of small and large systems incur health-based violations. Rubin ( 8) describes summary statistics of violations for four SDWA rules for the year 2011. The two studies in the peer review literature that address SDWA violations nationwide have study periods limited to a single year ( 8) or 7 y ( 9). Several studies focus on a single state (e.g., refs. Past analyses of the association between water system characteristics and violations have generally been limited in terms of geographic area and/or study period. Currently, there is not a good understanding of quality violations and few peer-reviewed studies have been done on SDWA compliance. This paper presents a national assessment of trends in drinking water quality violations across several decades. However, from 1993 to 2009, compliance with Safe Drinking Water Act (SDWA) health-based regulations ranged from 79 to 94% of the population served by CWSs ( 4). The Environmental Protection Agency (EPA) has a strategic objective to achieve consistent compliance for 91% of the population served by CWSs ( 4). While this rate is relatively low, improved compliance is needed to ensure safe drinking water nationwide. However, in a given year, about 7–8% of CWSs report at least one health-based violation. Generally, water systems in the United States provide reliable and high-quality drinking water. Equity concerns are also gaining recognition as evidence builds regarding lower-income and minority communities receiving poor quality water ( 2, 3). Identifying threats and potential improvements to water services are needed, given that an estimated 16.4 million cases of acute gastroenteritis each year in the United States are attributed to community water systems (CWSs) ( 1). We discuss why certain violations might be clustered in some regions and strategies for improving national drinking water quality. These findings indicate the types of underperforming systems that might benefit from assistance in achieving consistent compliance. Meanwhile, private ownership and purchased water source are associated with compliance. In terms of vulnerability factors, we find that violation incidence in rural areas is substantially higher than in urbanized areas. Repeat violations are prevalent in locations of violation hot spots, indicating that water systems in these regions struggle with recurring issues. Increasing time trends and violation hot spots are detected in several states, particularly in the Southwest region. We also identify vulnerability factors of communities and water systems through probit regression. In this paper, we evaluate spatial and temporal patterns in health-related violations of the Safe Drinking Water Act using a panel dataset of 17,900 community water systems over the period 1982–2015. Efforts to reduce violations are of national concern given that, in 2015, nearly 21 million people relied on community water systems that violated health-based quality standards. However, no nationwide assessment has yet been conducted on trends in drinking water quality violations across several decades. In the aftermath of the Flint lead crisis, there is an urgent need to assess the current state of US drinking water. Ensuring safe water supply for communities across the United States is a growing challenge in the face of aging infrastructure, impaired source water, and strained community finances.
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