Nearly 10,000 dogs force-fed pesticides for 90 days — most of it pointless, study finds

"We thought they were sacrificed for humanity."

Puppies just four to six months old — not yet fully grown — are cradled in the arms of researchers. At first glance, it looks as though they are simply being fed. The reality is the opposite.

The animals are being force-fed pesticides and herbicides as part of toxicity tests conducted before agrochemical products reach the market, to determine how harmful the compounds are to humans.

The forced dosing lasts a minimum of 90 days. And regardless of how toxic the pesticide turns out to be, the dogs' fate is rarely a bright one.

Even dogs that survive the dosing period are not spared. Their organs and tissues are examined after death to determine what toxic effects the pesticide caused — meaning none leave the laboratory alive.

It might be tempting to view this as an unavoidable cost of protecting human health. But a striking finding has upended that assumption.

Cases where dogs were genuinely indispensable to pesticide hazard testing turned out to be a small fraction of the total.

Just 4.6 percent, to be precise. Over the past 24 years, roughly 10,000 dogs were used in pesticide trials alone — and the vast majority, researchers now say, were subjected to experiments unnecessarily.

The use of animals in pesticide toxicity testing is common internationally. Under the US Environmental Protection Agency's guidelines for 90-day oral toxicity studies in non-rodents, the test species must be a non-rodent mammal — and the animal of choice is almost always the dog, specifically the beagle, a breed long favored for laboratory use.

When dogs are used, dosing typically begins at four to six months of age and no later than nine months. The protocol requires at least three dose groups plus a control group, with a minimum of four males and four females per group — at least eight animals per dose level. Even a basic study design calls for a minimum of 32 dogs.

Pesticide compounds are administered by mixing them into feed or drinking water, or by gavage or capsule. After 90 days, most surviving animals are also killed. Autopsies examine everything from external surfaces to the brain, heart, liver, kidneys and reproductive organs to check for signs of toxicity.

Dogs are far from the only animals sacrificed for human convenience — pharmaceuticals and other product testing claim vast numbers as well. South Korea is no exception. According to annual data from the Animal Experiment Ethics Committee compiled by the Animal and Plant Quarantine Agency, about 4.95 million animals were used in domestic experiments last year, an average of roughly 13,000 per day.

The central question is how much useful information these tests actually provide when assessing and applying human safety standards — in other words, whether the tests were truly necessary in the first place. An analysis of decades of pesticide toxicity data suggests that, in most cases, dog testing was not required at all.

In 2023, researchers affiliated with the animal protection organization Humane Society (now Humane World for Animals) and the agrochemical company Syngenta published a paper in the journal Critical Reviews in Toxicology examining existing test data for 195 pesticides evaluated by the EPA between 1998 and 2021.

The researchers found that dog studies provided data that could not be replaced by other sources for only 9 of the 195 pesticides reviewed — just 4.6 percent. Of the roughly 9,700 dogs used across all 195 substances, only 522 were involved in testing the 9 pesticides where dog data actually influenced the hazard assessment.

For the vast majority of cases, comparable levels of health protection could have been achieved using rat studies or other existing data alone. More than 9,200 dogs were sacrificed for tests where alternatives were available.

Yet dog testing for pesticides continues. Long-standing regulations and testing standards remain on the books, and progress toward establishing alternative criteria that would allow dog studies to be skipped has been slow.

Findings questioning the added value of dog testing for pesticides have continued to accumulate. The European Food Safety Authority also revisited the question last July, re-examining whether dog toxicity studies were genuinely necessary across 461 pesticides.

In most cases, dogs were not found to be meaningfully more sensitive to pesticides than rats or other animals. That held for 97 percent of cases when setting acceptable daily intake levels — the amount a person can safely consume over a lifetime — and for 95 percent of cases when establishing safety standards for workers who handle pesticides.

The findings suggest that in most instances, comparable safety standards could have been set using other animal studies or existing data without conducting dog tests at all. The authority recommended shifting away from routinely repeating dog studies for every pesticide, proposing instead that existing data be reviewed first and new dog tests conducted only when strictly necessary.

South Korea faces the same issue. Last November, a researcher from the National Institute of Agricultural Sciences presented findings at an international EFSA workshop, analyzing domestic pesticide data. A review of 18 newly registered pesticide compounds found that dog test results had been used in a significant number of cases when setting human safety standards.

When dog test results were set aside and compared against data from rats and other animals, however, the picture changed. A substantial share of cases that had relied on dog data were found to be replaceable with results from other sources.

For acceptable daily intake standards, the share of cases deemed to require dog testing fell from 22 percent to 5.56 percent. For worker safety standards, it dropped from 50 percent to 11.1 percent. The findings suggest that for a significant number of domestic pesticides, safety standards could potentially be set without putting dogs through testing at all.

Policy efforts to reduce animal testing are also moving forward. In the United States, a mandatory one-year dog toxicity study previously required for pesticide approval was abolished in 2007, leaving only the 90-day requirement. This past January, the EPA reaffirmed its goal of phasing out mammalian animal testing entirely by 2035.

The South Korean government has also belatedly moved to expand the use of alternative testing methods. The Ministry of Climate, Environment and Energy this year established a joint public-private task force and is developing a strategy to promote animal-free alternatives for chemical testing between 2027 and 2035, along with a plan to gradually restrict animal testing.

But change has been slow. The one-year dog study is gone, but the 90-day dog toxicity test remains in use for pesticide safety evaluations. Research findings questioning the necessity of dog testing have mounted, yet translating those findings into actual changes to regulations and testing standards is taking considerable time.

Researchers and animal protection groups say that by making fuller use of accumulated toxicity data and validated alternative methods, unnecessary dog testing could be reduced far more quickly than current progress suggests.

"If we could end the one-year test, we can end the 90-day test," Humane World for Animals said. "In almost every case, this cruel experiment provides no additional value in determining the risk of pesticides to humans."