Pesticide Cocktails Kill At “Safe” Doses

Facts matter: Sign up for the free Mother Jones Daily newsletter. Support our nonprofit reporting. Subscribe to our print magazine.


591px-Rana_sphenocephala.jpg Combinations of ten of the world’s most popular pesticides decimate amphibian populations even if the concentrations are within EPA safe limits for each chemical individually. These supposedly safe low-dose cocktails kill 99 percent of leopard frog tadpoles. One pesticide alone—endosulfan, a neurotoxin banned in several nations but still used extensively in US agriculture—killed 84 percent of the leopard frogs all on its own.

Obviously we can’t get a new EPA chief fast enough.

Biologist Rick Relyea at the U of Pittsburgh exposed gray tree frog and leopard frog tadpoles to small amounts of the 10 most widely used pesticides on Earth. He chose five insecticides (carbaryl, chlorpyrifos, diazinon, endosulfan, and malathion) and five herbicides (acetochlor, atrazine, glyphosate, metolachlor, and 2,4-D). He then administered: each of the pesticides alone, all the insecticides combined, a mix of the five herbicides, or all 10 of the poisons.

The findings published in Oecologia: A mixture of all 10 chemicals killed 99 percent of leopard frog tadpoles. The insecticide-only mixture killed 99 percent of leopard frog tadpoles. The herbicide mixture had no effect on the tadpoles. When leopard frogs perished, gray tree frogs did not succumb and flourished in the absence of leopard frog competitors.

This study builds on a 9-year effort by Relyea to understand links between the global amphibian decline, pesticide use, and the threat to humans. Leopard frogs were once plentiful across North America but their population has declined in recent years as pollution and deforestation have increased.

Okay, here’s one link: Humans get more populous and pudgy as frogs and forests decline.

Another study Relyea published in Ecological Applications last month reports that gradual amounts of malathion—the most popular insecticide in the US—too small to kill developing leopard frog tadpoles, instead sparked a biological chain of events that deprived them of their primary food source. Consequently nearly half the tadpoles in the experiment failed to reach maturity and would have died in nature.

Relyea also published papers in 2005 suggesting the popular weed-killer Roundup® is extremely lethal to amphibians in concentrations currently found in the environment.

Relyea for EPA chief?

Julia Whitty is Mother Jones’ environmental correspondent, lecturer, and 2008 winner of the PEN USA Literary Award, the Kiriyama Prize and the John Burroughs Medal.

THE TRUTH...

is the first thing despots go after. An unwavering commitment to it is probably what draws you to Mother Jones' journalism. And as we're seeing in the US and the world around, authoritarians seek to poison the discourse and the way we relate to each other because they can't stand people coming together around a shared sense of the truth—it's a huge threat to them.

Which is also a pretty great way to describe Mother Jones' mission: People coming together around the truth to hold power accountable.

And right now, we need to raise about $400,000 from our online readers over the next two months to hit our annual goal and make good on that mission. Read more about the information war we find ourselves in and how people-powered, independent reporting can and must rise to the challenge—and please support our team's truth-telling journalism with a donation if you can right now.

payment methods

THE TRUTH...

is the first thing despots go after. An unwavering commitment to it is probably what draws you to Mother Jones' journalism. And as we're seeing in the US and the world around, authoritarians seek to poison the discourse and the way we relate to each other because they can't stand people coming together around a shared sense of the truth—it's a huge threat to them.

Which is also a pretty great way to describe Mother Jones' mission: People coming together around the truth to hold power accountable.

And right now, we need to raise about $400,000 from our online readers over the next two months to hit our annual goal and make good on that mission. Read more about the information war we find ourselves in and how people-powered, independent reporting can and must rise to the challenge—and please support our team's truth-telling journalism with a donation if you can right now.

payment methods

We Recommend

Latest

Sign up for our free newsletter

Subscribe to the Mother Jones Daily to have our top stories delivered directly to your inbox.

Get our award-winning magazine

Save big on a full year of investigations, ideas, and insights.

Subscribe

Support our journalism

Help Mother Jones' reporters dig deep with a tax-deductible donation.

Donate