Mercury Exposure Associated with Autoimmunity

Exposure to even low levels of mercury may be associated with autoimmune disorder development among women of childbearing age, according to a new study published in Environmental Health Perspectives.

Researchers examined women aged 16 to 49 years who participated in the National Health and Nutrition Examination Survey between 1999 and 2004. They studied 3 biomarkers of mercury exposure: hair, blood, and urine.

Subjects who consumed higher levels of mercury tended to have a higher rate of antinuclear antibodies (ANAs), which are often associated with autoimmune disease. ANAs are produced when an individual’s immune system cannot differentiate between naturally occurring proteins in the body and foreign or dangerous ones.

One of the most common ways in which women are exposed to mercury is through fish consumption. While eating fish has a range of health benefits, women—especially those who are pregnant—might want to pay attention to the quantity and type of fish they are consuming.

“For women of childbearing age, who are at particular risk of developing this type of disease, it may be especially important to keep track of seafood consumption,” said lead author Emily Somers, PhD, ScM, an associate professor in the departments of Internal Medicine in the division of Rheumatology, Environmental Health Sciences, and Obstetrics & Gynecology at the University of Michigan Medical and Public Health Schools, in a press release.

A pregnant woman who consumes methylmercury-contaminated fish or shellfish can pass her mercury exposure to the fetus through the placenta. Infants exposed to methylmercury could experience developmental abnormalities and cerebral palsy, according to the US Centers for Disease Control and Prevention (CDC).

The CDC notes that larger and older fish tend to contain more mercury. Furthermore, an FDA report on mercury levels in commercial fish and shellfish determined that scallops, canned salmon, clams, shrimp, and oysters had the lowest mercury levels, while tilefish, swordfish, shark, tuna, and orange roughy had the highest.

“The presence of autoantibodies doesn’t necessarily mean they will lead to an autoimmune disease,” Dr. Somers said. “However, we know that autoantibodies are significant predictors of future autoimmune disease and may predate the symptoms and diagnosis of an autoimmune disease by years.”

Nearly 50 million Americans have autoimmune disorders, which include Crohn’s disease, rheumatoid arthritis, and multiple sclerosis.