EPA not protecting public from neonic exposure
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The analysis examined
five studies that exposed pregnant rats’ to various types of insecticides known
as neonicotinoids (commonly called neonics). The studies found that the
offspring born to the exposed rats suffered shrunken brains and other problems.
Statistically significant shrinkage of brain tissue was seen
in the offspring of rats exposed to high doses of five types of neonics –
acetamiprid, clothianidin, imidacloprid, thiacloprid, and thiamethoxam, the
paper states. The authors said the impacts on the brain appeared similar to the
effects of nicotine, which they said is known to disrupt mammalian neurological
development.
The animal studies also support the possibility of a link
between neonic exposure and attention deficit hyperactivity disorder (ADHD),
the authors said.
In most cases, the companies submitting the studies did not
submit data for all dosage levels, leading the Environmental Protection Agency
(EPA) to assume negative effects were only seen at the high dose, according to
the study.
“We found numerous deficiencies in the Environmental Protection Agency (EPA)’s regulatory oversight and data analyses,” the authors state in the paper, published in the journal Frontiers in Toxicology. The industry studies, which the EPA used to determine what neonic exposure levels are considered safe for humans, were not publicly available and were obtained through a Freedom of Information Act (FOIA) request.
“Consistently, effects were found at the high dose and EPA
did not demand data for the lower doses, therefore leaving it unclear how
little of a substance it takes to actually cause adverse effects such as
reduced size of certain brain regions,” said Bill Freese, the science director
for the environmental advocacy group Center for Food Safety and an author of
the study.
The study found that the EPA consistently made
determinations about what levels of neonic exposure were “safe” for humans
without enough data to support its conclusions. For example, a 2001 study
submitted to the agency by the pesticide manufacturer Bayer found effects on
fetal brain development when pregnant rats were exposed to high doses of the
pesticide imidacloprid. The EPA asked the company for mid- and low-dose data,
then set a limit for imidacloprid at the mid-dose level even though it never
received data showing that exposure at this level was safe.
“EPA needs to more rigorously demand data from registrants
when they fail to submit,” said Freese. “They’re making a decision to say these
lower levels cause no harm, even though they have no data to back that.”
Since two of the neonics, imidacloprid and thiacloprid,
break down into so-called metabolites that are as potent as nicotine, “one
might expect to see neurodevelopmental impacts of exposure to their parent
chemicals at low exposure levels,” the authors write.
The authors also concluded that the EPA should assess the
cumulative exposure and risk for neonics as a group, a measure required under
the Food Quality Protection Act for pesticides that work similarly.
The findings come as the EPA proposes reevaluating
occupational exposures to three neonics, clothianidin,
imidacloprid, and thiamethoxam, by 2025, as the agency carries out its
standard registration review of
neonics as a class. The EPA identified additional risks to workers while
treating the seeds with the chemicals and cleaning seed treatment equipment,
“even when the use of maximum personal protective equipment is considered.”
“These compounds have been approved for decades and now EPA
is saying, ‘maybe we underestimated the risk,’” says Freese.
The European Union banned outdoor uses of
all three pesticides in 2018.
Neonics, like other pesticides sold or distributed in the
US, undergo an “in-depth evaluation of potential risks…to the environment and
the US population,” said the EPA in an email. “The rodent developmental
neurotoxicity studies discussed in this article have been independently
reviewed by EPA and incorporated into the most current human health risk
assessments for these neonicotinoid pesticides,” said the EPA.
Neonics were first introduced in the 1990s as safer
replacements for older pesticides and are now the most widely used insect-killing
chemicals in the US and around the world. In addition to their agricultural use
as a coating on seed crops such as corn and soybeans, neonics are sprayed on
lawns, gardens, parks and playgrounds, and are applied on pets in flea and tick
treatments.
In recent years, neonics have been detected in surface waters and treated
drinking water in the Midwest, and a 2022 study found the chemicals in the
bodies of over 95% of pregnant women across the US. A 2015-2016
monitoring study by the
Centers for Disease Control and Prevention found the highest levels of neonics
in young children. In the most recent Food and Drug Administration pesticide
residue monitoring report,
imidacloprid was tied for the pesticide most frequently found in human food
samples, while acetamiprid and thiamethoxam made the top ten.
Research increasingly calls the safety of neonics into
question. Some scientists suspect that neonics are driving losses in
populations of important pollinators, including bees. A 2023 EPA assessment found
that three commonly used neonics may be driving over 200 endangered plants and
animals towards extinction. Another 2023 study found
behavioral changes in zebrafish exposed to neonics, with effects persisting
into adulthood, while a study published
this summer found that exposure to the neonic clothianidin caused behavioral
changes in developing female mice.
In contrast, a 2015 review by the companies Bayer,
Syngenta, and other pesticide manufacturers concluded that “the collective
evidence indicates the neonicotinoid insecticides are not developmental
neurotoxicants.”