Indiana researchers have discovered a link between herbicide ingredient glyphosate and breast cancer.

A recent study, performed by scientists from the Purdue Center for Cancer Research and the Institut National de la Santé et de la Recherche Médicale/Institut de Cancérologie de L’Ouest in Nantes, France, discovered that glyphosate causes tumor growth when combined with oxidative stress.

Oxidative stress is a chemical reaction that results from aging, diet, smoking and alcohol consumption, among other stressors.

“This is a major result and nobody has ever shown this before,” said Sophie Lelièvre, a professor of cancer pharmacology in Purdue’s College of Veterinary Medicine and co-leader of IBCN, in a press release. “Showing that glyphosate can trigger tumor growth, when combined with another frequently observed risk, is an important missing link when it comes to determining what causes cancer.”

The study, which was published in Frontiers in Genetics, did not find that glyphosate causes tumor growth without the presence of oxidative stress, but did discover that the combination of the two produced a more severe form of cancer.

“What was particularly alarming about the tumor growth was that it wasn’t the usual type of breast cancer we see in older women,” Lelièvre said. “It was the more aggressive form found in younger women, also known as luminal B cancer.”

In the past, the U.S. Environmental Protection Agency has classified glyphosate as both “not carcinogenic” and “probably carcinogenic.” It has also been linked to non-Hodgkin lymphoma. This new research lays the groundwork for further research into the dangers of glyphosate.

Lelièvre and the other study scientists believe this discovery could be a key part of both reversing and preventing breast cancer, which is the most common type of cancer.

Learn more about the study here. Learn more about glyphosate in Indiana here.