New Research Finds 485 Chemicals in US Pesticide Products Linked to Breast Cancer

A particularly concerning finding in this study is that only around 145 of the 485 substances cited are registered as active pesticide ingredients. Many of the remainder are classed as ‘inert’ ingredients – substances added to pesticide formulations for purposes such as helping the active chemical spread or penetrate more effectively – and generally receive less regulatory scrutiny.

The researchers compiled their list using chemicals previously identified as causing mammary tumors in animals or interfering with estrogen or progesterone signaling in ways relevant to breast cancer. This does not mean that all 485 chemicals have been proven to cause breast cancer in humans. Nevertheless, the potential for widespread exposure is concerning. The researchers found breast-cancer-relevant chemicals not only in pesticides, but also in consumer products, food, drinking water, pharmaceuticals, and construction materials.

Breast cancer rates have continued to increase worldwide, particularly among younger women, and established risk factors do not fully explain the trend. While research continues into the contribution made by environmental chemicals, the precautionary principle suggests that unnecessary exposure to substances with evidence of cancer-related biological effects should be reduced wherever possible. Calling an ingredient ‘inert’ may have a regulatory meaning, but it does not mean the substance is necessarily biologically inactive in the human body. The new findings provide another compelling reason for regulators to examine the safety of complete pesticide formulations, rather than concentrating primarily on their designated active ingredients.

To read how a recent study found that almost half of the world’s farmers are poisoned by pesticides every single year, see this news story on our website.