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Septic systems are a major source of emerging contaminants in drinking water

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septic-system-contamination
Photo credit: Silent Spring Institute.
septic-system-contamination
Photo credit: Silent Spring Institute.

A new analysis shows that septic systems in the U.S. routinely discharge pharmaceuticals, consumer product chemicals, and other potentially hazardous chemicals into the environment.

The study, published June 15, 2017 in the journal Environmental Science & Technology, is the most comprehensive assessment to date of septic systems as important sources of emerging contaminants. It raises health concerns since many of these chemicals, once discharged, end up in groundwater and drinking water supplies.

Known as contaminants of emerging concern (CECs), these types of pollutants are frequently detected in U.S. and Canadian rivers, lakes, and drinking water supplies. Many emerging contaminants are hormone disruptors. Their presence in the environment has been associated with the feminization of male fish and reduced fertility in other wildlife. Studies in humans have linked some CECs with thyroid disease, developmental disorders, decreased fertility, and even cancer.

“These are chemicals found in the products we use every day, and eventually they make their way down the drain,” said Laurel Schaider, an environmental chemist at Silent Spring Institute and the study’s lead author, in a press release. “What’s concerning is that we are potentially re-exposed to these chemicals through our drinking water and we have no idea what the health effects from those exposures are.”

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To assess the effectiveness of septic systems at removing contaminants, Schaider and her colleagues conducted a meta-analysis of 20 different studies on septic systems, creating a comprehensive dataset on emerging contaminants commonly discharged into the environment. According to the press release, the researchers identified 45 contaminants in total. These include pharmaceuticals, personal care product ingredients, chemicals in cleaning products, flame retardants, hormones (both natural and synthetic), and other common substances such as caffeine.

In the analysis, Schaider found that septic systems do a decent job at removing chemicals such as acetaminophen, caffeine, and alkyphenols—a common group of ingredients used in cleaning products. However, they’re much less effective at removing other contaminants. Chemicals that tend to slip through include TCEP, a carcinogenic flame retardant, an anti-epilepsy drug called carbamazepine, and the antibiotic sulfamethoxazole.

“In high density areas where you have a large number of homes with their own septic systems, these systems are likely the primary source of emerging contaminants in the groundwater,” says Schaider. That becomes especially problematic when these residents also rely on private, shallow groundwater wells for their drinking water.

The study also compared treated wastewater from conventional septic systems with that from centralized wastewater treatment plants and found similar levels of contaminants. This suggests that switching from septic systems to a centralized sewer system may not completely address problems of emerging contaminants entering the environment.

According to Schaider, the best way to protect drinking water quality is to keep septic systems away from areas that supply local drinking water wells. “It’s also important that people follow guidelines for maintaining their septic systems to make sure they’re in good working order,” she says. “And avoiding household products with harmful ingredients by switching to safer alternatives can make a real difference.”

To read the original press release, visit: www.silentspring.org

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