Study stresses the need to set safety standards for “forever chemicals” in seafood.
Morgan Kelly
A Dartmouth-led study suggests that people who frequently consume seafood may face an increased risk of exposure to PFAS, the family of ubiquitous and resilient human-made toxins known as “forever chemicals.”
The findings stress the need for more stringent public health guidelines that establish the amount of seafood people can safely consume to limit their exposure to perfluoroalkyl and polyfluoroalkyl substances, the researchers report in the journal Exposure and Health.
This need is especially urgent for coastal regions such as
New England where a legacy of industry and PFAS pollution bumps up against a
cultural predilection for fish, the authors write.
“Our
recommendation isn’t to not eat seafood—seafood is a great source of lean
protein and omega fatty acids. But it also is a potentially underestimated
source of PFAS exposure in humans,” says Megan Romano, the study’s
corresponding author and an associate professor of epidemiology at
the Geisel
School of Medicine.
“Understanding
this risk-benefit trade-off for seafood consumption is important for people
making decisions about diet, especially for vulnerable populations such as
pregnant people and children,” Romano says.
Most existing research focuses on PFAS levels in freshwater species, which are not what people primarily eat. We saw that as a knowledge gap in the literature, especially for a New England state.
The study paired an analysis of PFAS concentrations in fresh seafood with a statewide survey of eating habits in New Hampshire as a case study of seafood consumption in New England and other coastal states.
National data indicate
that New Hampshire—along with all of New England—is among the country’s top
consumers of seafood, which made the state ideal for understanding the extent
of people’s exposure to PFAS through fish and shellfish.
“Most
existing research focuses on PFAS levels in freshwater species, which are not
what people primarily eat,” says Romano, who studies the effects of PFAS and
other endocrine-disrupting chemicals in drinking water on New England
communities. “We saw that as a knowledge gap in the literature, especially for
a New England state where we know people love their seafood.”
The
study also drew on New Hampshire’s extensive data on the sources and effects of
PFAS, which are a staple of consumer products such as plastics and nonstick
coatings. The molecular stability that makes PFAS versatile also makes them
nearly indestructible, leading them to be called forever chemicals.
In
humans, PFAS are associated with cancer, fetal abnormalities, high cholesterol,
and thyroid, liver, and reproductive disorders. The chemicals have accumulated
in soil, water, and wildlife, and studies have shown that nearly all Americans
have measurable amounts in their blood.
“PFAS are not limited to manufacturing, fire-fighting foams, or municipal waste streams—they are a decades-long global challenge,” says study co-author Jonathan Petali, a toxicologist with the New Hampshire Department of Environmental Services.
“New Hampshire was among the first states to identify
PFAS in drinking water. We’re a data-rich state due to years spent
investigating the impacts of PFAS and trying to mitigate exposure.”
The
researchers measured the levels of 26 varieties of PFAS in samples of the most
consumed marine species: cod, haddock, lobster, salmon, scallop, shrimp, and
tuna. The seafood studied was purchased fresh from a market in coastal New
Hampshire and originated from various regions.
Shrimp
and lobster clocked the highest concentrations with averages ranging as high as
1.74 and 3.30 nanograms per gram of flesh, respectively, for certain PFAS
compounds, the researchers report. Concentrations of individual PFAS in other
fish and seafood measured generally less than one nanogram per gram.
The prevalence of PFAS in the environment makes it difficult to know exactly where and how the chemicals enter the marine food chain, the researchers report. Some shellfish may be especially vulnerable to the buildup of PFAS in their flesh due to feeding and living on the seafloor, as well as their proximity to sources of PFAS that are near the coast.
Larger marine species may ingest PFAS
by eating smaller species that, like shellfish, are prone to having the
compounds accumulate in their systems.
Buttressing
the study is a survey of 1,829 New Hampshire residents the researchers
conducted to gauge how much seafood Granite Staters eat—and it’s a lot.
The
survey found that men in New Hampshire eat just over one ounce of seafood per
day and women eat just under one ounce. Both are higher than what the National
Health and Nutrition Examination Survey found for men and women in the
Northeast, and more than 1.5 times the national average for both. Daily intake
for New Hampshire children aged 2 to 11 years old was about 0.2 ounces, the
highest end of the range for children nationwide.
About
95% of adults the researchers surveyed reported they ate seafood within the
past year, and 94% of that group consumed fish or shellfish within the previous
month. More than two-thirds of those respondents ate seafood within the past
week.
But
people in New Hampshire do not eat seafood uniformly. More than half of the
people who ate seafood in the week before the survey lived on the state’s coast
or near the border with Massachusetts. More than 60% of people with a household
income below $45,000 per year reported consuming seafood at least once per
week, whereas people with higher household incomes reported eating seafood less
often.
Of
the species the researchers tested for PFAS, shrimp, haddock, and salmon were
consumed by more than 70% of the adults who ate seafood once a month or more.
Lobster was eaten by just over 54% of these adults. Salmon, canned tuna,
shrimp, and haddock were the most commonly consumed species among children.
Federal
guidelines for safe seafood consumption exist for mercury and other
contaminants, but there are none for PFAS, says Celia Chen, a co-author of the study
and a research professor in the Department of Biological Sciences.
“Top
predator species such as tuna and sharks are known to contain high
concentrations of mercury, so we can use that knowledge to limit exposure. But
it’s less clear for PFAS, especially if you start looking at how the different
compounds behave in the environment,” says Chen, who leads several federally
funded projects examining how and where PFAS accumulate in aquatic food webs in New Hampshire and Vermont.
The
establishment of safety guidelines would help protect people who are especially
susceptible to pollutants, says Kathryn Crawford, the study’s first
author and an assistant professor of environmental studies at Middlebury
College.
“Seafood
consumption advisories often provide advice for those individuals that is more
conservative than for the rest of the population,” says Crawford, who began the
project as a postdoctoral researcher in the
Romano Lab at Dartmouth. “People who eat a balanced diet with
more typical, moderate amounts of seafood should be able to enjoy the health
benefits of seafood without excessive risk of PFAS exposure.”