Pesticides Linked to Vitamin D Deficiency

Pesticides could be suppressing vitamin D levels in people, leading to deficiency and disease, say scientists. This comes from a new study which discovered that adults with high serum concentrations of organochlorine pesticides, such as DDT, have lower vitamin D levels, further proving that these chemicals have a long-lasting impact on human health. While not widely appreciated, some organochlorine pesticides continue to be used in the U.S., resulting in exposure through our diet, environment, and prescription drugs, while most organochlorine pesticides have been banned in the U.S. and much of the world.

Exposure to low doses of organochlorine pesticides has been previously linked to common diseases like type 2 diabetes, metabolic syndrome and cardiovascular disease. Vitamin D deficiency has similarly been associated with a rise in chronic diseases, but the two have been studied separately by researchers in different fields. The study, "Associations between Organochlorine Pesticides and Vitamin D Deficiency in the U.S. Population,” compared serum concentrations of organochlorine (OC) pesticides with serum concentrations of 25-hydroxyvitamin D (25(OH)D), a vitamin D pre-hormone, which is used to assess vitamin D levels in the body. It concludes that background exposure to some OC pesticides can lead to vitamin D deficiency in humans.

The U.S.-Korean research team studied 1275 adults from the National Health and Nutrition Examination Survey (NHANES), 2003–2004, aged 20 years or older, and checked their blood for several organochlorine pesticides. Cross-sectional associations of serum OC pesticides with serum 25(OH)D were examined. DDT and beta-hexachlorocyclohexane levels in the study volunteers showed significant associations with lower serum concentrations of the vitamin D pre-hormone, 25(OH)D. Stronger associations tended to be observed among subjects with old age, white race, or chronic diseases.

"We have known for many years that DDT causes egg shell thinning,” says David Carpenter, PhD, director of the Institute for Health and Environment at the University of Albany, New York. “Since egg shell thickness is regulated by vitamin D, this study shows that the same suppression of vitamin D occurs in humans.”

Most organochlorine pesticides were banned in the U.S. decades ago, but are still detectable in people because they resist biodegradation in the environment, are lipophilic and accumulate in fat tissues. However, organochlorine uses do continue in the U.S., although EPA has proclaimed that they represent unreasonable risks. Under an agreement EPA negotiated in July 2010, most currently approved endosulfan crop uses will end in 2012, including over 30 crop uses plus use on ornamental trees, shrubs, and herbaceous plants. About 12 other crop uses will end over the following four years. Of these 12, the last four endosulfan uses will end on July 31, 2016. See details on EPA’s phase-out agreement. Under a separate agreement signed last year, dicofol, an organochlorine miticide/pesticide, may continue to be used through 2016 for foliar applications on cotton, apples, citrus, strawberries, mint, beans, peppers, tomatoes, pecans, walnuts, stonefruit, cucurbits, and non-residential lawns/ornamentals. According to EPA, “[T]race amounts of DDT (<0.1%) have been measured in dicofol products given its use in the manufacture of dicofol..." Lindane shampoos for lice and lotion for scabies is still permitted by the Food ad Drug Administration as prescription only products. The wood preservative, pentachlorophenol, is still allowed by EPA to be used on treated telephone poles that line streets and backyards across the country.

Organochlorines have been linked to a number of adverse effects to human health, including birth defects and diabetes. One study found a correlation between organochlorine metabolites in fatty tissue and an increased risk of non-Hodgkin’s Lymphoma. The most infamous member of this class of pesticides if DDT. A long line of recent studies associated with the negative health effects of DDT include breast cancer and autism. Despite the fact that DDT was banned in the U.S. in 1972, concentrations of this toxic chemical’s major metabolite, DDE, have remained alarmingly high in many ecosystems, including surface waters, the arctic, and even U.S. national parks.

Studies like these illustrate how the health impacts of pesticides can be often subtle and delayed, and pesticides once considered to pose “acceptable” risks are continuing to affect public health. In response to the growing evidence linking pesticide exposures to numerous human health effects, Beyond Pesticides’ Pesticide-Induced Diseases Database captures the range of diseases linked to pesticides through epidemiologic studies. The database, which currently contains hundreds of entries of epidemiologic and laboratory exposure studies, is continually updated to track the emerging findings and trends.