Glossary

Type a term:

Pesticides and Herbicides

Pesticides and Herbicides Many products containing pesticides and herbicides are applied on our fields, in our homes, and in our communities to help control pests and weeds. These chemicals can then leach into our water supplies, or stay on surfaces on which we (including our children) live, play and work, or remain on our foods, both fresh and processed.

Many of these chemicals mimic estrogens and exposures to high levels of these products have been shown to increase breast cancer rates.

What are the chemicals that are causing concern and where are they found?

Pesticides and herbicides include a variety of chemical compounds used to control and eliminate weeds and pests in both agricultural and non-agricultural settings. These products are used extensively on agricultural fields. They are also used to control weeds in forests, pastures, parks, athletic fields, golf courses, ponds, lakes, and home lawns and gardens, as well as for pest control in products such as termite-resistant plywood, as well as more broadly in homes, apartment buildings, schools, and businesses.

Some classes of pesticides and herbicides, and examples of chemicals involved include:

  • Organochlorine pesticides: DDT, DDE, Chlordane, Heptachlor, Dieldrin, Methoxane
  • Organophosphate pesticides: Diazinon, Chlorpyrifos
  • Triazine herbicides: Atrazine, Simazine, Cyanazine
  • Chlorophenoxy herbicides: 2,4-D, 2,4,5-T, Agent Orange

How do these chemicals enter the body?

Pesticides and herbicides are applied in a variety of settings. As a result, exposure occurs frequently and often unknowingly. Pesticides and herbicides that are sprayed on agricultural crops can stay on produce and enter the body when these products are ingested. Chemicals applied to golf courses, fields, and home lawns and gardens can seep into groundwater and collect in aquifers. Sometimes they are not filtered out through public water systems and ultimately end up in the water that is used for drinking, cooking, and bathing. Other chemicals that are used to control pests (such as ants, cockroaches, etc.) in the home end up in the air and dust and can then be easily taken into the body through breathing and absorption through the skin. People may come in contact with both pesticides and herbicides by walking or playing in treated areas. Children may be especially susceptible to some of the toxic effects of pesticides [National Research Council, 1993]. Once in the body, these chemicals tend to be persistent and accumulate in fatty tissue, including the breast.

What are the mechanisms by which these substances might increase the risk for breast cancer?

Many pesticides and herbicides are xenoestrogens, or chemicals that mimic the actions of natural estrogens. In addition, organochlorine pesticides alter the ratio of different estrogen metabolites or breakdown products present in the body. The result is that there is an elevated production of the kind of estrogens that enhance breast cell growth, increase unscheduled DNA synthesis, and gene expression. In addition, there is a modest decrease in the concentration of the kind of estrogen metabolites that have been shown to inhibit breast cell growth [Bradlow et al., 2005]. Together these changes may increase the likelihood of breast cancer.