When we determine which communities are more likely to get their water from contaminated supplies, median household income is not the best measure.
That's according to a recent study led by researchers at The University of Texas at Austin that found social factors -- such as low population density, high housing vacancy, disability and race -- can have a stronger influence than median household income on whether a community's municipal water supply is more likely to have health-based water-quality violations. In general, rural communities and communities that grew up around large industries that have since left are most likely to face water-quality issues.
About 10% of community water systems in the contiguous United States have a reported health-based violation. The study's findings are important because many state and federal agencies use median household income as the primary factor when deciding how to distribute funding meant to assist disadvantaged communities.
"As states are developing definitions and trying to prioritize disadvantaged communities, they should look at a number of different parameters and see which ones apply best for them," said lead author Bridget Scanlon, a senior research scientist at the UT Bureau of Economic Geology. "The study offers a useful tool that lawmakers can use to learn more about how different types of social vulnerability are associated with different water-quality issues. This can then aid in coming up with lasting solutions that community water systems need to fix these issues."
The study was published in Environmental Research Letters.
Scanlon and her collaborators were inspired to look into the connection between social vulnerability and water-quality violations due to the passage of new federal drinking water infrastructure laws. The new laws require states to allocate at least 49% of about $50 billion in federal funding to address water issues in disadvantaged communities.
But which communities are considered disadvantaged is often left up to state policymakers to decide, with most states opting to use median household income as the primary (or the only) factor, according to the study
The researchers tested how well median income matched up with water-quality violations reported during 2018-2020 in community water systems across the contiguous United States. It then compared the results with those from a new social vulnerability index created for the study that took 15 social factors into account. The study's social index is modified from a similar index created by the Centers for Disease Control and Prevention that's used for identifying communities that may need more support during natural disasters and public health emergencies.
The index created by the researchers proved to be a better indicator, capturing three times as much of the population affected by community water-quality violations as median household income did. The results underscore the connection between social vulnerability and water quality. About 70% of people subjected to health-based water-quality violations were ranked among the most socially vulnerable, based on the index.
The study also highlighted the specific social factors that are connected to an increased probability of facing water-quality issues, and how they vary based on the specific water-quality issue at hand.
For example, most of the water-quality problems come from naturally occurring minerals seeping from the rocks -- such as arsenic -- and the byproducts of water treatment used to kill bacteria. Most of the communities facing these problems are in rural and deindustrialized areas. The index found that vacant housing, population density, and disability rate were the top three factors that most increased the probability of facing a health-based water-quality violation.
According to the study authors, many of the water-quality challenges are downstream of demographics, with many community water systems lacking the financial, managerial and technical abilities to address the water-quality issues.
The study was funded by the Environmental Protection Agency through the Texas Commission on Environmental Quality and the Jackson School of Geosciences. It was co-authored by Robert Reedy and Sarah Fakhreddine, both researchers at the Bureau of Economic Geology, and Gregory Pierce, a researcher at the University of California, Los Angeles.
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