Analysis highlights
impact of wastewater management decisions on drinking water quality
From the Silent Spring
Institute
A new analysis shows
that septic systems in the United States routinely discharge pharmaceuticals,
consumer product chemicals, and other potentially hazardous chemicals into the
environment.
The study, published
June 15 in the journal Environmental Science & Technology, is
the most comprehensive assessment to date of septic systems as important
sources of emerging contaminants, raising 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. rivers, lakes, and drinking water supplies.
However, the U.S.
Environmental Protection Agency does not currently regulate them in drinking
water. 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. And 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,” says Laurel Schaider, an environmental chemist at Silent Spring Institute
and the study’s lead author.
“What’s concerning is that we are potentially re-exposed to these chemicals as mixtures through our drinking water and we have no idea what the health effects from those exposures are.”
Approximately 20 percent
of U.S. households rely on septic systems to process their wastewater. In some
parts of the country, the number is much higher. In Cape Cod, Massachusetts,
for instance, 85 percent of residents rely on septic systems.
Although septic systems
are known sources of nutrient pollution and have been associated with disease
outbreaks, questions remain regarding the extent to which they contribute
emerging contaminants to the environment.
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 the most comprehensive dataset on emerging contaminants commonly
discharged into the environment.
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 others 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, she says, when these residents also rely on private, shallow
groundwater wells for their drinking water, as is often the case in states like
Massachusetts, Delaware, Florida, Maryland, New Jersey, and New York.
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.”
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Funding for this study
was provided by the Commonwealth of Massachusetts and charitable donations to
Silent Spring Institute.
Reference:
Schaider L.A., K.M.
Rodgers, R.A. Rudel. 2017. Review of
Organic Wastewater Compound Concentrations and Removal in Onsite Wastewater
Treatment Systems(link is external). Environmental
Science & Technology. doi:10.1021/acs.est.6b04778