Exposure to multiple pesticides significantly increases the risk of childhood cancers compared to exposures to just one pesticide, first-of-its-kind research finds, raising new fears that children are more at risk to the substances’ harmful effects than previously thought.

The study’s authors say they are the first to look at the link between exposures to multiple widely used pesticides and the most common childhood cancers. Most research considers pesticides’ toxicity on an individual basis, and the substances are regulated as if exposures occur in isolation from one another.

But people are exposed to multiple pesticides in water, produce, meat, fish and processed foods. In agricultural communities, children can be even further exposed to multiple pesticides in water, air, dust, and in the home.

Of the 32 pesticides researchers examined, they found the most potent mixes were among herbicides such as dicamba, glyphosate and paraquat – controversial products that are each sprayed on tens of millions of acres of cropland nationally.