Commonly used herbicides across the U.S. contain highly toxic undisclosed “inert” ingredients that are lethal to bumblebees, according to a new study published Friday in the Journal of Applied Ecology.

The study reviewed several herbicide products and found that most contained glyphosate, an ingredient best recognized from Roundup products and the most widely used herbicide in the U.S. and worldwide.

While the devastating impacts of glyphosate on bee populations are more broadly recognized, the toxicity levels of inert ingredients are less understood because they are not subjected to the same mandatory testing by the Environmental Protection Agency (EPA).

“Pesticides are manufactured and sold as formulations that contain a mixture of compounds, including one or more active ingredients and, potentially, many inert ingredients,” explained the Center for Food Safety in a statement. “The inert ingredients are added to pesticides to aid in mixing and to enhance the products’ ability to stick to plant leaves, among other purposes.”

The study found that these inert substances can be highly toxic and even block bees’ breathing capacity, essentially causing them to drown. While researchers found that some of the combinations of […]