National trends in drinking water quality violations

Abstract

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. In the aftermath of the Flint lead crisis, there is an urgent need to assess the current state of US drinking water. However, no nationwide assessment has yet been conducted on trends in drinking water quality violations across several decades. 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. 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. We also identify vulnerability factors of communities and water systems through probit regression. Increasing time trends and violation hot spots are detected in several states, particularly in the Southwest region. Repeat violations are prevalent in locations of violation hot spots, indicating that water systems in these regions struggle with recurring issues. In terms of vulnerability factors, we find that violation incidence in rural areas is substantially higher than in urbanized areas. Meanwhile, private ownership and purchased water source are associated with compliance. These findings indicate the types of underperforming systems that might benefit from assistance in achieving consistent compliance. We discuss why certain violations might be clustered in some regions and strategies for improving national drinking water quality.

Keywords: Safe Drinking Water Act; drinking water; regulatory compliance; violations; water quality.

Fig. 1.

Number of health-based violations, 1982–2015, by contaminant type.

Fig. 2.

Number of health-based violations, 1982–2015. Gray bars represent dates that major components of rules became enforceable.

Fig. 3.

Total violations per water system, by housing density category and income group. Low-income counties have median household income below 75% of national median household income. In year 2015, national median household income was $55,775 and 45% of rural CWSs are located in counties defined as low-income.

Fig. 4.

Number of violations per CWS, 1982–2015, by county. (A) Total violations. (B) Total coliform violations. Intervals in legend are selected based on the Jenks natural breaks classification method.

Fig. 5.

Spatial clusters (hot spots) of health-based violations, 1982–2015. Hot spots for number of total violations per CWS, by county. Intervals in legend are selected based on the Jenks natural breaks classification method.