Are pesticides evil, or awesome?

Are pesticides helpful things that allow us to produce more food, and keep us safe from deadly diseases? Or are they dangerous things that kill animals and could possibly be hurting us in ways we haven't even totally figured out just yet?

Actually, they're both.

This week, scientists released a research paper looking at the health benefits (or lack thereof) of organic food—a category which largely exists as a response to pesticide use in agriculture. Meanwhile, Rachel Carson's book Silent Spring, which forced Americans to really think about the health impacts of pesticides for the first time, was published 50 years ago this month.

The juxtaposition really drove home a key point: We're still trying to figure out how to balance benefits and risks when it comes to technology. That's because there's no easy, one-size-fits-all answer. Should we use pesticides, or should we not use them? The data we look at is objective but the answer is, frankly, subjective. It also depends on a wide variety of factors: what specific pesticide are we talking about; where is it being used and how is it being applied; what have we done to educate the people who are applying it in proper, safe usage. It's complicated. And it's not just about how well the tools work. It's also about how we used them.

“It is not my contention,” Carson wrote in Silent Spring, “that chemical insecticides must never be used. I do contend that we have put poisonous and biologically potent chemicals indiscriminately into the hands of persons largely or wholly ignorant of their potentials for harm. We have subjected enormous numbers of people to contact with these poisons, without their consent and often without their knowledge.”

You can see why this isn't an easy issue. It's legitimate to be concerned about how pesticides affect biodiversity. It's also legitimate to be concerned about having access to the tools we need to protect people from malaria. At some point, you have to make a decision, but you're fooling yourself if you think that decision is clear-cut.

The situation gets doubly confusing when you start adding in the fact that we don't actually have a lot of great data on the human health impacts of pesticides. In fact, we might never have good data on that.

Xeni had a nice write up on the organic food paper earlier this week, but I'd also recommend reading the story that Emily Sohn wrote at Discovery News. The organic food study you read about this week was actually a review paper—a study of studies. Scientists looked at hundreds of research papers comparing organic and conventional food and tried to use that data to figure out what we do and don't know in the big picture. Studies like this are a lot more meaningful than single papers alone, but it also means there's a ton of stuff going on and understanding it all gets very confusing very quickly. Sohn does a really nice job of breaking down the details of the paper and she digs into the key problem: We don't have enough evidence to answer the questions that really matter.

Only 17 studies compared groups of people eating different diets, and most showed no difference on measures like sperm motility, levels of fatty acids in breast milk or antioxidant levels in blood.

“We evaluated just under 6,000 potentially relevant articles…and identified 17 studies that looked at people eating diets that were organic or conventional,” said Dena Bravata, a general internist and health researcher at Stanford University and Castlight Health in San Francisco. “Here’s this gigantic industry and there have been 17 studies. To highlight the paucity of evidence that really directly answers the question we had, I think that’s interesting.”

Together, the results are too inconclusive and disparate to draw any major conclusions, said Betsy Wattenberg, a toxicologist at the University of Minnesota, Twin Cities.

In order to really know anything about food-related risks that people tend to care most about, such as cancer or reproductive and developmental health issues, we would need carefully controlled studies that last for years or even decades.

Those kinds of studies don’t exist, and they are likely impossible to do.

Read Emily Sohn's full article on the organic food study

Read a retrospective on Rachel Carson's work written by William Souder at Slate

Image: A soldier sprays a mixture of DDT and kerosene in an Italian home. Spraying like this helped to drastically reduce malaria in Italy. Otis Historical Archives National Museum of Health and Medicine.