Pesticide exposure, menstrual cycle characteristics and timing of menopause: An analysis of the agricultural health study

Certain pesticides act as hormone agonists or antagonists and may adversely affect the ovary and estrous cycle in animals. Using data from the Agricultural Health Study I examined the associations between pesticide use and menstrual cycle characteristics and timing of menopause among women living and working on farms. Six pesticides were classified as "probable" endocrine disruptors or ovotoxicants based on the toxicology literature: atrazine, carbaryl, carbon tetrachloride, DDT, lindane, and mancozeb. Among 3,103 women aged 21 to 40 in the Agricultural Health Study, use of probable hormonally active pesticides was associated with greater odds of longer menstrual cycles, missed periods, and inter-menstrual bleeding, and reduced odds of irregular cycles. Among 8,040 women aged 35 to 55 in the Agricultural Health Study, use of probable hormonally active pesticides was associated with a later age at menopause. Longer menstrual cycles and missed periods may be associated with fewer ovulatory cycles over time and a later age at menopause. Therefore, the association between pesticide use and timing of menopause may be mediated through an association with menstrual cycles. Alternatively, the probable hormonally active pesticides may directly affect timing of menopause due to effects on follicle-stimulating hormone and luteinizing hormone, two hormones that play a role in the menopausal transition. These results suggest that use of hormonally active pesticides may affect a woman's menstrual cycles. Changes in the menstrual cycle may have implications for fecundability as well as chronic diseases associated with reproductive hormones.