Turns out a new generation of supposedly safer pesticides isn't so safe after all. In the latest entry of a growing body of evidence, scientists announced last week that pyrethroid pesticides — now in hundreds of pest control products sold for home use — can interfere with the healthy development of an infant's nervous system when moms are exposed during pregnancy. Here we go again.
History tells us that substituting one type of pesticide for another "safer" variety just doesn't work out very well.
In the beginning, there were organochlorine pesticides (OCs). The post-WWII explosion in the use of these longlasting chemicals was based on belief that the "miraculous" pesticides were pretty much harmless to humans. In time, scientists began to understand the dangers of chemicals like DDT and endosulfan (both OCs). They last for years in the environment, build up in the tissues of animals (including humans), pass from mother to child during pregnancy and can wreak havoc on the human nervous, hormone and immune systems. Some organochlorines can also cause cancer. Harmless? Not very.
Next up was the family of pesticides called organophosphates (OPs), which didn't last nearly so long in the environment or build up in human tissue. Safer, right? The catch is, they're much more toxic in the short term. OPs have been linked to many, many health harms, including higher rates of ADHD in children, reproductive harms, and increased risk of Parkinson's Disease. Many have been banned from household products because they are especially dangerous to children, but use on farms is still widespread.
Pyrethroids were then introduced — not so many years ago — as a new, safer alternative to OPs. Pyrethroids are synthesized to mimic the natural insecticide pyrethrum, which is extracted from certain species of chrysanthemum. But once again, scientists are discovering that the synthetic version is far from harmless.
The latest study, released on February 7th in the journal Pediatrics, tracked prenatal exposure to pyrethroids among 348 women in New York City. The moms-to-be were rigged with air sampling backpacks to measure their intake of pyrethroid insecticides. Researchers actually looked for piperonyl butoxide, an easy-to-measure marker chemical that's added to pyrethroid products to boost their potency. They took prenatal blood samples too.
Researcher Megan Horton and her colleagues then caught up with the new moms 3 years later, and used standard tests to assess the children's cognitive and motor development. Kids exposed to more pyrethroids were 3 times more likely to have developmental delays. Given that there are currently about 2,500 products on the market containing this new "safer" family of chemicals, these findings are important news for parents and parents-to-be. And a significant wake-up call for pesticide policymakers.
In the grand scheme of things, the history of synthetic pesticide use isn't so very long. But sadly, that history is long enough that tens (maybe hundreds) of thousands of children have suffered the consequences — measured in life-changing health harms — of assuming the next generation of chemicals will be safe. And it's definitely long enough to learn this basic lesson: constantly shifting to the next best chemical fix not only doesn't work very well for controlling pests (that's a whole other story), it also isn't good for our health.