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Vol. LXIII, No. 6
March 18, 2011

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Pesticide Use Linked to Lupus, Rheumatoid Arthritis
Dr. Rajesh Ranganathan

Dr. Christine G. Parks of NIEHS led a study showing that frequent or extended exposure to pesticides may increase the risk of developing such autoimmune diseases as lupus and rheumatoid arthritis.

Along with what you say, be careful what you spray. Frequent or extended exposure to pesticides may increase the risk for developing autoimmune diseases such as lupus and rheumatoid arthritis, according to the results of a longterm follow-up study of thousands of postmenopausal women.

The findings were recently presented by lead scientist Dr. Christine G. Parks of the National Institute of Environmental Health Sciences and her colleagues.

Nearly a billion pounds of pesticides, typically used to kill termites, fleas and household bugs, are spread into the environment each year, through both agricultural and nonagricultural use. According to the 2008-2009 Annual Report of the President’s Cancer Panel, nearly 1,400 pesticides have been registered and approved by the Environmental Protection Agency. However, the report notes, exposure to chemicals found in pesticides has been associated with a variety of cancers including breast, colon, prostate and lung cancer. Further, some research has shown higher rates of various cancers in farmers, pesticide applicators and manufacturers compared to the general, non-using public.

In addition, it is believed that the chemical substances found in pesticides can be toxic to the developing brain. This is backed by recent findings showing that prenatal pesticide exposure may affect intelligence and learning in children, when tested at 3 years of age. Other recent studies show that pesticide exposure may elevate the risk of Parkinson’s disease.

Now it appears that a new series of conditions referred to as autoimmune rheumatic disorders— lupus and rheumatoid arthritis (RA)— may also be linked to pesticide exposure.

Parks and her associates looked at the possible relationship between self-reported household insecticide application and the development of either lupus or RA in almost 77,000 women participating in the Women’s Health Initiative. The WHI Observational Study, a cohort investigation that began in 1991, was initially designed to track the most common causes of mortality, disability and poor quality of life.

“Although the hypothesis was well-founded [based on higher rates of some autoimmune diseases associated with farming], I was somewhat surprised at the findings,” said Parks, who reported that the strongest association between pesticides and the two autoimmune disorders was seen in women who lived on a farm and reported personally applying insecticides. These individuals displayed nearly three times the risk for disease development, compared to women who used no pesticides whatsoever. Meanwhile, lupus/RA risk was doubled for women who underwent 20 or more years of direct exposure (personally applying pesticides) and for those who reported applying insecticides six or more times annually.

While most of the women in the study were Caucasian, no racial differences were seen and the findings were not changed in analyses that accounted for other disease risk factors.

Lupus, also known as systemic lupus erythematosus, is an autoimmune disease—a condition in which the body attacks itself—causing inflammation and damage to healthy tissues and key organs including the heart, lungs and brain. Most lupus patients are female, indicating the condition could have a hormonal or other gender-specific component. RA, another autoimmune disorder, causes joint inflammation and pain, fatigue and other symptoms that may persist for years. Affecting more than a million children and adults, the disease is more prominent in women than men.

In general, the etiology as well as the role of external factors in the development of autoimmune diseases are not well understood. Although data are scarce, most recent findings indicate that the environment may play a contributing role.

While the findings are notable, Parks’ study did have a few shortcomings, she explained. For example, because of the general type of question asked “we were not able to determine which specific insecticides were applied.” Also, she pointed out, the data were based on participants’ long-term recall.

Still, the findings were robust, that is—“We could see a similar pattern of association for both diseases and a dose response for both increasing frequency and duration of use,” said Parks. In other words, the more the exposure, the greater likelihood of developing lupus or RA. She noted that, based on previous studies of farm work, similar findings might be expected in men.

The NIEHS scientist added that a prudent approach would be to limit one’s exposure to pesticides as much as possible.

The findings were reported in the February issue of Arthritis Care and Research.NIHRecord Icon

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