EPA internally questioned its ability to properly regulate pet collars linked to tens of thousands of injury reports

Investigate Midwest
11 min readMar 24, 2022


For years, U.S. Environmental Protection Agency officials have raised concerns that the agency’s process for determining the danger of the more than 400 pet flea and tick products it regulates is deeply flawed and has resulted in the use of pesticides that are potentially harmful to pets and their human owners.

By Johnathan Hettinger, Investigate Midwest

This story is supported with a grant from the Fund for Investigative Journalism. This story was co-published with USA TODAY. It is embargoed until April 4, 2022.


EPA documents released in batches since July through a Freedom of Information lawsuit reveal the depth of those concerns and the internal debate over one product in particular that’s linked to numerous reports about harm to pets. The records also show that the scientists say they were warned by their superiors not to document their concerns in emails, which are subject to public records disclosure.

Some EPA managers were concerned enough that they discussed with top-level officials turning over regulation of pet products to the Food and Drug Administration, which regulates many other pet products. Indeed, the FDA is now assisting the EPA in a review of a popular pet collar that is the target of consumer complaints.

The issue of ineffective regulation and oversight came to a head in March 2021 when an Investigate Midwest and USA TODAY investigation revealed that the EPA had received more than 75,000 reports from pet owners and veterinarians about adverse incidents linked to the popular Seresto collar. In those reports, pet owners and veterinarians said dogs and cats were having skin rashes, seizures and dying after wearing the collars.

“Looks like the sh** has hit the fan,” wrote EPA wildlife biologist Nicholas Mastrota in an email to a colleague on March 3. “Will be interesting seeing where this goes. I hope there is a FOIA for all communications on this so that our emails are made public. We have been screaming about (Seresto) for many years.”

After the story, EPA staff provided a stark assessment of how the EPA’s process compares to the FDA’s in a presentation to Michal Freedhoff, the EPA’s assistant administrator for the Office of Chemical Safety and Pollution Prevention. In that role, which is confirmed by Congress, Freedhoff oversees all pesticide regulation.

The EPA is responsible for regulating pet pesticide products that are “not systemic,” or ones that aren’t supposed to enter the bloodstream, while the FDA regulates “systemic” pet pesticide products, which are generally consumed by pets.

In that presentation, agency staff had a few key takeaways:

  • The EPA’s approval process is dated and relies on company-funded studies. That process, along with small sample sizes and use of less sensitive pet breeds, makes the data less useful, the staff said.
  • The FDA has a much more comprehensive pet product regulation process, which includes pre-market clinical trials and post-market surveillance.
  • The EPA has no process for evaluating pet incident reports or any defined precedent for when incident numbers trigger further review — even when they’re linked to a high number of pet deaths.
  • When pet owners or veterinarians do report a problem, they don’t report enough information to give the EPA the ability to properly analyze incidents. Internal comparisons found Seresto had a high number of incident reports compared to other products.

Canada’s pesticide office declined to approve Seresto for use in that country because it had a rate of pesticide incidents 50 times greater than the average flea and tick collar, and at least 36 times the rate Canada deemed safe.

Since March 2021, more than 11,000 additional complaints about the Seresto collar — which works by releasing two pesticides, imidacloprid and flumethrin, onto an animal’s fur for up to eight months at a time — were filed with the EPA.

These incident reports, which are filed by pet owners and veterinarians, do not necessarily mean that the collar causes the problem. The EPA has said it lacks data to properly evaluate that connection, and has requested and received more information from the collar’s manufacturers to further look into the connection.

Seresto’s manufacturer, Elanco, maintains the collar is safe. The company said the rate of complaints has declined since the product was put on the market in 2012 by Bayer. Elanco — which bought the entire Bayer Animal Health unit, including Seresto, from the German pharmaceutical giant in 2020 for $7.6 billion — has said its own extensive studies into the product show that the incidents of harm reported by pet owners are likely related to other factors and not the collar itself.

The EPA PowerPoint presentation was among thousands of pages of documents released by the agency in response to a lawsuit by the nonprofit Center for Biological Diversity, which works to watchdog the EPA to protect endangered species.

The documents reveal that for at least six years, Mastrota and other EPA scientists had warned superiors about the number of pet deaths and incidents involving the Seresto collars.

The documents include repeated comparisons of Seresto to other products by EPA staff, as well as records of multiple meetings with Bayer Animal Health, which developed the collar, and Canadian regulators, who chose not to approve the collar for use in that country based on U.S. incidents.

The new documents have been released as a Congressional oversight subcommittee continues to investigate the Seresto collar, and the EPA conducts a formal review of the product. The documents showcase how the EPA’s Office of Pesticide Programs — which is currently under an internal review — struggles to regulate pesticides under the federal pesticide law.

Rep. Raja Krishnamoorthi (D, Illinois), who last year called for an investigation into Seresto as Chairman of the House Subcommittee on Economic and Consumer Policy, expressed concern about the documents.

“I launched an investigation in March 2021 when I learned that EPA allowed a product linked to almost 1,700 pet deaths to remain on the market,” Krishnamoorthi said in an emailed statement. “I am extremely concerned by documents showing that scientists within the EPA raised warning flags, but EPA never listened. Our investigation is ongoing, and we will get to the bottom of this issue to make sure EPA is doing its job to protect Americans and their pets from harmful pesticides.”

The EPA did not respond to specific questions about the internal strife or discussions about transferring regulation to the FDA. An EPA spokeswoman said the EPA has sought the advice and counsel of the FDA on Seresto.

EPA spokeswoman Cathy Milbourn emailed a statement, saying the agency “understands and shares the public’s concerns about reported incidents with these collars.” Milbourn wrote that the agency requested more information from Bayer and Elanco about the incidents and is in the process of reviewing that data.

“Upon completing the analysis and assessment, EPA may take further action, if needed,” Milbourn wrote.

Previous reviews of pet collar complaints and issues have taken years to resolve.

FDA assisting in investigation of Seresto

In an emailed statement, an FDA spokesperson said that the agency “has been providing advice and expertise on EPA’s review of the post-market safety data associated with Seresto collars.”

At first, the EPA struggled to get the attention of the FDA, documents show.

The documents show that at one point, Ed Messina, director of the Office of Pesticide Programs, which oversees all pesticides, attempted to reach out to the FDA, but FDA staff members declined to give Messina the email for Dr. Steven Solomon, director of the FDA’s Center for Veterinary Medicine.

“FDA counterparts don’t seem to want to give us his contact information. We don’t know what to do, it’s a very odd situation,” wrote Meredith Laws, an EPA employee.

Messina eventually reached Solomon by using Solomon’s publicly available contact information.

Some EPA scientists endorsed the idea of transferring regulation to the FDA, citing concerns about the EPA’s process.

However, the FDA statement said that is a question that goes beyond just that agency.

“Any future changes to regulatory oversight would need to be consistent with each agency’s mission and legal authority and would likely involve stakeholder and Congressional input,” an FDA spokesperson said.

‘Why is Seresto even registered?’

Over the years, Robert Miller, who oversaw the EPA’s incident reporting program, raised concerns a number of times about Seresto, which has had the most incidents of any pet pesticide product, according to an EPA database. There have been at least 86,000 incident reports filed with the EPA, and more than 28 million collars sold — making it one of the most popular collars on the market.

In one email in August 2020, Miller wrote to his supervisor that he had compared the best-selling flea and tick collar to other products “ well known to kill and maim pets “ and found that Seresto was “much more harmful” than those products combined.

After the public learned of the concerns in March 2021, Miller was inundated with emails of stories of dead and sick pets. He seemed to find one email particularly upsetting. A California wildlife biologist working with the San Joaquin Kit Fox asked whether she should be concerned about her use of the collar on the endangered species.

Miller forwarded the request, with a note: “I will respond if you like, but I may lose my cool. Why is Seresto even registered? At the very least Seresto should not be used on the endangered San Joaquin Kit Fox.”

In response, Miller was admonished by a superior, Marietta Echeverria, acting director of the Pesticide Registration Division. Echeverria had overseen Seresto in a previous role and told Miller he needed to respond professionally.

“With all due respect your email is insulting. Respond professionally to my internal colleagues? Do you remember the time you had Melissa Panger pull Nick Mastrota and me aside to tell us not to express our concerns about Seresto in emails? Was that professional? One can only hope this email finds its way into a FOIA request,” Miller wrote.

It is not clear if anyone responded to the California wildlife biologist, who did not return calls requesting comment. Miller, who has since retired from the agency, declined further comment. Milbourn, the EPA spokeswoman, also declined to comment on the exchange.

Kyla Bennett, director of science policy at the nonprofit Public Employees for Environmental Responsibility, was not surprised by the documents. Called PEER, the nonprofit organization works to support current and former public employees who protect the environment. Bennett, a lawyer who formerly worked at the EPA, said the documents are consistent with what she’s heard from EPA pesticide employees for years.

“Unfortunately, this is pretty damn typical,” Bennett said. “I feel awful for the scientists there who are trying to do the right thing. I know some of them are losing sleep at night because of their role in what is going on.”

‘EPA is not listening to scientists’

The pesticide office staff have said they cannot get the data they need from companies to accurately assess the risk of a pesticide, according to the PowerPoint presentation. The EPA allows the use of dozens of pesticides that have been banned in other countries.

“The Office of Pesticide Programs is a quintessential example of an agency being captured by interest groups,” said Perry Elerts, visiting associate professor at the George Washington University Law School. “EPA is not listening to scientists. It knows these products are dangerous, and is waiting for industry itself to do something about its bad product, instead of doing its job to cancel these products.”

Elerts, who has previously worked at the Center for Biological Diversity, teaches a class about pesticide law and policy, and he said he uses Seresto as an example in class.

“Seresto is a great example,” he said. “There are hundreds and thousands of reports. People themselves are being harmed. Pets are being harmed, and EPA time and time again has refused to cancel the product.”

In November, U.S. Senator Cory Booker (D, New Jersey) introduced a bill, called the Protect America’s Children from Toxic Pesticides Act, which would ban imidacloprid, a key ingredient in Seresto, and other neonicotinoid pesticides — which are banned in Europe because of concerns about pollinator health. The bill was introduced in the last session of Congress and has not gained widespread support.

While Bayer and Elanco maintain the rate of complaints has declined, agency scientists have said the numbers still raised concerns. An EPA veterinarian sent around a chart showing the number of deaths in November 2018, expressing concern and saying “This is the only product where we are seeing this trend…”

‘Facebook probably receives more reports’ than EPA

One concern raised by the EPA in the PowerPoint presentation is that “several” other pet products contain pesticides that are potentially hazardous to human health, and regulating Seresto could lead consumers to those products. These products include the chemicals fipronil, which is commonly sold as Frontline, and amitraz, commonly sold as Mitaban.

The PowerPoint and an EPA spokeswoman did not say why the EPA is not taking action on those chemicals. Documents including information about what actions it may be taking on Seresto are redacted.

However, Miriam Rotkin-Ellman, a senior scientist with the Natural Resources Defense Council, said the documents fit with a pattern she’s seen with the EPA in regulating pesticide products, in particular pet products. Rotkin-Ellman has worked for more than a decade to convince the EPA to ban collars containing tetrachlorvinphos, an organophosphate pesticide that can cause brain damage in children.

“This is very short-sighted,” Rotkin-Ellman said. “When they do this type of risk-trading, they are short-circuiting the research into opening up the market space to products that don’t harm either pets or people.”

Rotkin-Ellman said the failures of the EPA’s system require the public to take protection into their own hands, by raising awareness through things like websites and Facebook pages and working to educate retailers on the risks of EPA-approved products.

“The only thing I’ve seen in the last 15 years I’ve seen working is the public taking matters into their own hands,” she said.

This concern was shared by Miller, the EPA incident coordinator, who said in the emails that “ Facebook probably receives more reports” than EPA. Mastrota, the EPA wildlife biologist, said that the pets in the Facebook stories had consistent symptoms such as “ seizures, tremors, vomiting and anorexia.

However, documents show several EPA employees were hopeful some action would be taken. Those include Mastrota, who sent a note along with a table including the flurry of complaints that poured in during March 2021.

“I hope you can do something about this soon because a lot of pets are dying. These adverse events may be rare, but with such wide use of this product, it still results in a lot of dead dogs and cats,” Mastrota wrote in an email.

Top image: This graphic was included in the EPA emails obtained by the Center for Biological Diversity. It shows reports of deaths linked to the Seresto flea and tick collar from 2014–2018.

Originally published at https://investigatemidwest.org on March 24, 2022.



Investigate Midwest

www.investigatemidwest.org is a nonprofit, online newsroom offering investigative and enterprise coverage of agribusiness and Big Ag.