You probably want to avoid pesticides, but do you know how the EPA determines whether to approve a pesticide that ends up in the food you and your family eat? This user-friendly overview examines the current (animal toxicity) methods used for determining whether a pesticide is safe enough to use and the changes the EPA is planning on making to those methods.
Here is an excerpt:
On September 10, 2019 the U.S. Environmental Protection Agency announced a major change to its approval process, with an ambitious plan to eliminate the use of all mammalian testing by the year 2035.
It’s a goal that some environmental groups say is too ambitious, potentially resulting in the unchecked approval of countless toxic chemicals. The scientists, regulators and advocates pursuing this change, however, disagree. They say the move will shift the agency towards a more accurate and humane approach to toxicity testing.
Chronic toxicity: beyond the poisonous dose
Some chemical formulations are made from synthetic ingredients, while others consist of only all-natural ingredients. Some persist or accumulate in the soil, water or in our bodies, while others break down relatively quickly. Still other chemicals are thought to have an endocrine-disrupting effect, even if they don’t bioaccumulate. The risk of harm usually depends on the exposure…
One of the earliest methods of testing toxic substances on animals was developed in 1920 by the British pharmacologist J.W. Trevan. Trevan designed the test that measures a chemical’s lethal dose—the point at which half of the animals in the test group have died due to chemical exposure.
Acute toxicity, that measurement of the lethal dose, is just one way of evaluating a chemical’s toxic effects but…it’s not necessarily the most relevant, especially given the way most of us are exposed to chemicals in our daily lives.
Most real human exposures are not acutely lethal (explaining the difference between acute and chronic toxicity) but have other, long-term or chronic effects that may or may not be toxic.
It’s these chronic effects that first began to cause greater alarm in the 1960’s, prompting a number of legislative attempts to create better regulatory oversight of agricultural toxicants. In 1970, President Nixon established the Environmental Protection Agency and, by 1972, all regulatory oversight of pesticides had shifted to the agency, where it remains to this day. While exact numbers aren’t available, Science reports that toxicology tests of these chemicals submitted to the EPA use anywhere from 20,000 to over 100,000 animals annually.
Rodent tests are poor predictors for human health risks
Despite animal toxicity testing’s long history, a growing coalition of scientists and animal rights advocates say these tests are both cruel and unreliable, a poor predictor for human disease. Human bodies aren’t quite the same as mice or rats, explains Lena Smirnova, PhD, a neuroscientist at the Johns Hopkins Center for Alternatives to Animal Testing.
Johns Hopkins was one of five universities awarded an EPA grant for work developing alternative toxicity tests that could eventually replace animal testing. The Baltimore-based lab is working with microphysiological systems dubbed “mini brains” to observe neurotoxic effects.
“[Rodents] have a different metabolism,” Smirnova explains. “They have different [types of] cells in the body. They react differently.” According to one study comparing human and animal drug toxicities, for example, rodent models correctly predicted human toxicity in only 43% of the cases…
For controversial pesticides like glyphosate or chlorpyrifos, more predictive testing of carcinogenicity and neurotoxicity could be able to provide some much-needed clarity. Chlorpyrifos, for example, is an organophosphate insecticide that the EPA declined to ban for agricultural use in 2017. Former EPA administrator Scott Pruitt questioned the reliance on epidemiological studies showing increasing rates of disease in agricultural communities.
The decision was controversial and, as a result of increasing pressure and lawsuits brought by environmental and farmworker advocacy groups, the state of California recently reached an agreement with the pesticide’s manufacturer to ban the chemical outright in the state. More toxicity evidence could shed new light on this controversy, potentially revealing more information about how these chemicals impact the human brain.
From inertia to a new way of thinking
In 2007, the National Academies of Sciences published a landmark report urging a reduction in animal testing and a move towards new methods for toxicity testing. But the report didn’t spark an immediate response from EPA regulators…
“You’ve got this inertia,” says Amy Clippinger, PhD, President of the International Science Consortium for People for the Ethical Treatment of Animals. Clippinger is also a member of the scientific advisory panel working towards reducing animal testing at the EPA and other government agencies. Overcoming inertia, she says, requires a real paradigm shift.
…the starting point was to involve the regulators themselves…real traction at the EPA [started] in 2013…when a new working group was formed that included EPA scientist Anna Lowit, PhD, who has been instrumental in implementing change…
The EPA [has now]…provided a statement that reads, in part:
Tools like data mining can reduce animal testing
…organizing the agency’s testing data into something searchable turned out to be a highly effective way to reduce unnecessary animal testing…With searchable systems in place, regulators can use data mining and other computational tools to locate previous testing results and determine whether the animal test is even needed.
…this is really a whole new framework for toxicity testing. The starting point… is not to simply replace the test but to first carefully consider the evidence that the test was actually providing.
In some cases, regulators are reviewing new chemicals that are virtually identical to many existing chemicals that are already well-tested. In those cases, additional testing may not be needed.
Researchers outside of government agencies are using many of these computational methods too, in some cases to make more accurate assessments of the risk of disease…
Example: a PETA researcher working on a study evaluating how useful the two year rat assay has been for predicting cancer risk. In a number of instances, animal tests were ordered even though the cancer risk was already abundantly clear. In those cases, you don’t need an additional test to predict cancer.
Mini brains and other human cell-based testing alternatives
At Johns Hopkins, Smirnova is testing the pesticides chlorpyrifos and rotenone on her lab’s “mini brains” to observe their neurotoxic impacts. These blob-like “organs-on-chip” may not look like much in their petri dishes, but scientists like Smirnova believe they’re the future of animal testing alternatives.
To create these mini brains, scientists first take blood or skin cells and genetically reprogram them back into an embryonic stem cell state. The stem cells can then be grown to mimic the key brain functions that the scientists want to test…
These human cell-based approaches have many different applications. Some researchers are working on animal testing alternatives in carcinogenicity, while others are working in the area of reproductive toxicity. There are also researchers developing computational models and data mining tools.
These days, the field of animal testing alternatives is exploding…
Animal rights advocates align with small government conservatives
Not all scientists agree that animal testing should be eliminated. The National Resources Defense Council’s (NRDC) position, for instance, is that animal tests work.
But the groups who do favor reduced animal testing are a bit of an unlikely coalition…these allies include not only traditional animal rights types who are predominately liberal but…animal lovers across the political spectrum [and] people who favor things like small government. The common thread is their agreement that these [animal] tests are not providing useful information.
See the EPA’s plan to eliminate the use of all mammalian testing by the year 2035.
Read the entire article here.