In hundreds of U.S. towns and cities, a largely unspoken issue is increasingly impacting public health: raw sewage overflows. According to recent research by Boston University’s School of Public Health, the risk of acute gastrointestinal illness surges by up to 62% following certain types of sewer overflows. This issue, already significant, is poised to worsen with the intensifying effects of climate change, particularly as extreme rainfall events become more common.
The story begins in the mid-1800s when combined sewer systems were introduced on the U.S. East Coast. These systems, designed to handle both raw waste and stormwater in a single pipe, were a quick fix for rapidly growing cities. However, they come with a significant downside: during heavy rainfall, these systems often become overwhelmed, leading to the discharge of untreated wastewater into local bodies of water.
Today, approximately 700 communities still rely on these outdated systems, primarily in older areas along the East Coast and Midwest. Even minimal rainfall less than 0.3 inches can trigger overflows, contaminating rivers and streams with harmful pathogens, heavy metals, and other pollutants.
For residents in these communities, sewer overflows pose a serious public health risk. The Boston University study highlights a clear link between these overflows and gastrointestinal illnesses, including vomiting, diarrhea, and infections. The risk is particularly high following extreme overflows, with the top 1% of incidents increasing the likelihood of illness by 62%.
While the study focused on emergency department visits, the true number of affected individuals is likely higher, as many people may treat their symptoms at home without seeking medical care. Fortunately, the research confirms that treated drinking water remains safe, even after an overflow event.
Role of Climate Change: More Rain, More Overflows
Climate change is exacerbating the problem, particularly in regions where combined sewer systems are prevalent. As global temperatures rise, the atmosphere holds more moisture, leading to more intense rainfall events. These deluges are increasingly overwhelming outdated sewer systems, resulting in more frequent and severe overflows.
The U.S. Global Change Research Program reports that the Northeast and Midwest are experiencing significant increases in extreme rainfall events, contributing to a rise in sewer overflows. This trend is expected to continue, posing an ongoing threat to public health in affected communities.
In response to this growing crisis, the federal government has allocated billions of dollars for wastewater and stormwater improvement projects. The Environmental Protection Agency (EPA) now requires all communities with combined sewer systems to develop mitigation plans aimed at reducing or eliminating overflows.
However, fixing these systems is a costly and time-consuming process, often requiring the replacement of entire sewer networks—a task that can cost hundreds of millions to billions of dollars and take many years to complete.
In the meantime, many cities are turning to green infrastructure as a more immediate, cost-effective solution. By planting trees, installing rain gardens, and creating green roofs, urban areas can absorb rainwater where it falls, reducing the volume of stormwater entering the sewer system. While these strategies are helpful, more work is needed to combat the increasing rainfall driven by climate change.
As climate change continues to intensify extreme weather events, communities across the U.S. must confront the growing challenge of sewer overflows and their impact on public health. With federal support and innovative green infrastructure solutions, there is hope for reducing these risks. However, addressing the root causes of the problem will require significant investment, long-term planning, and a commitment to protecting both public health and the environment.
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