 |
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.
