USGS Warns Millions of Americans May Be Drinking Contaminated Water
By U.S. Geological Survey
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| This map shows extensive PFAS presence in the groundwater where most Charlestown residents draw their drinking water |
An estimated 71 to 95 million people in the contiguous United States—over 20% of the nation’s population—may depend on groundwater containing detectable levels of per- and polyfluoroalkyl substances (PFAS) for their drinking water. This data comes from a U.S. Geological Survey study published on October 24.
The predictive model results can help members of the public,
water suppliers, and regulators understand the potential for PFAS
contamination, guide future studies, and inform strategic planning for water
resources.
USGS scientists are the first to report national estimates
of PFAS occurrence in untreated groundwater that supplies water to public and
private wells. This research also provides the first estimate of the number of
people across the country who are potentially affected by PFAS-contaminated
groundwater.
Along with a scientific report, the USGS published an interactive, online map so users can
see probability estimates of PFAS occurrence. Note that predictive results are
intended to be evaluated at state, regional, and national scales rather than at
individual household levels. Probability estimates are for the presence of PFAS
in groundwater and do not account for any subsequent actions taken by states,
municipalities, or individuals to treat drinking water. The model does not
include estimates of PFAS concentrations; testing is the only way to confirm
the presence of contaminants.
Health Risks and Environmental Persistence of PFAS
Exposure to certain PFAS may lead to adverse health risks in
people, according to the U.S. Environmental Protection Agency. PFAS are a group
of synthetic chemicals used in a wide variety of common applications, from the
linings of fast-food boxes and non-stick cookware to fire-fighting foams and
other purposes. PFAS are commonly called “forever chemicals” because many of
them do not easily break down and can build up over time, making them a concern
for drinking water quality.
“This study’s findings indicate widespread PFAS
contamination in groundwater that is used for public and private drinking water
supplies in the U.S.,” said Andrea Tokranov, USGS research hydrologist and lead
author of this study. “This new predictive model can help prioritize areas for
future sampling to help ensure people aren’t unknowingly drinking contaminated
water. This is especially important for private well users, who may not have
information on water quality in their region and may not have the same access
to testing and treatment that public water suppliers do.”
The EPA has established legally enforceable levels, called
maximum contaminant levels, for six types of PFAS in drinking water. The EPA
regulates public water supplies, and some states have additional regulations
for drinking water. Some homes use private water supplies, where residents are
responsible for the maintenance, testing, and treatment of their drinking
water. Those interested in treatment processes and testing options can read EPA’s guidance or contact their
state officials or water suppliers.
USGS national estimates of the probability for PFAS in
groundwater at the depth of private drinking water supply. Credit: U.S.
Geological Survey
The states with the largest populations relying on public
water supplies with potentially contaminated groundwater sources are Florida
and California. Regarding private wells, Michigan, Florida, North Carolina,
Pennsylvania, New York, and Ohio have the largest populations relying on
potentially contaminated groundwater.
State-Level Data on PFAS Risk
The study also presents data according to population
percentage. In Massachusetts, for example, the source water for 86 to 98% of
people who rely on groundwater from public water supplies could be contaminated
with PFAS. In Connecticut, the source water for 67 to 87% of the people who
rely on groundwater from private wells could be affected. Details by state can
be seen in the report’s tables S6 through S8.
“To derive these estimates, the team analyzed 1,238
groundwater samples collected by USGS scientists and determined how factors
such as urban development and well depth can impact PFAS occurrence,” continued
Tokranov. “With that information, a detailed machine learning model
was developed and used to identify which geographic areas have a higher
likelihood for contamination. That information was combined with existing USGS
research on the number of people in a given area who rely on groundwater for
drinking water to establish population estimates.”
Scientists present separate estimates for public and private
wells because they typically receive water from different groundwater depths.
Public wells using groundwater as the primary water source are usually deeper
than private wells.
There are more than 12,000 types of PFAS, not all of which
can be detected with current tests; the USGS study tested for the presence of
24 common types. The USGS estimates consider the presence of at least one of
those 24 types of PFAS. The most frequently detected compounds were
perfluorobutane sulfonate known as PFBS, perfluorooctane sulfonate known as
PFOS, and perfluorooctanoate known as PFOA.
This research provides a broad outlook for the Lower 48
states and presents state-level estimates. Scientists did not look in detail at
specific cities or provide estimates for the types of PFAS present or PFAS
concentrations.
Reference: “Predictions of groundwater PFAS occurrence at
drinking water supply depths in the United States” by Andrea K. Tokranov,
Katherine M. Ransom, Laura M. Bexfield, Bruce D. Lindsey, Elise Watson,
Danielle I. Dupuy, Paul E. Stackelberg, Miranda S. Fram, Stefan A. Voss, James
A. Kingsbury, Bryant C. Jurgens, Kelly L. Smalling and Paul M. Bradley, 24
October 2024, Science.
DOI:
10.1126/science.ado6638