Twin Cities women who use skin-lightening products or who eat certain kinds of fish more often may be putting themselves and their babies at risk for mercury exposure, a new study by the Minnesota Department of Health (MDH) has found. Mercury is a neurotoxin that can harm the brain or nervous system and cause other health problems.

The Minnesota Family Environmental Exposure Tracking (MN FEET) project measured mercury, lead and cadmium in nearly 400 Twin Cities women and their babies. Pregnant women from Asian, East African, Latino and White communities were recruited for the study. The study focused on these groups because of communities’ concerns and information from other studies indicating they may have more of these chemicals in their bodies than women from other communities.

“Mercury exposure can be a significant health concern, but in this case the good news is that those groups we found to be at elevated risk have the power to reduce that risk,” Minnesota Commissioner of Health Jan Malcolm said. “This study shows that we have an opportunity to help people better understand the potential dangers of using skin-lightening products and frequently eating fish higher in mercury.”

MDH’s Minnesota Biomonitoring: Chemicals in People program conducted the study in partnership with HealthPartners Institute and SoLaHmo Partnership for Health & Wellness at Minnesota Community Care (formerly known as West Side Community Health Services). The Legislature funded the project and the Environmental Health Tracking and Biomonitoring Advisory Panel provided guidance.

The researchers found that women in the study who had used skin-lightening products in the past had more mercury in their urine than women who didn’t use these products. Follow-up contact with women who had high urine mercury levels found that using skin-lightening products was the main reason for the high levels. In some cases, when study partners visited participants in their homes, they found skin-lightening products that were putting mercury into the air that the whole family was breathing; they helped participants remove the products.  

In addition, the study found that women who ate more walleye, northern pike, bass, white bass or king fish had more mercury in their babies’ cord blood. Follow-up contact with women with high cord blood mercury found that most of them ate these fish more than once per month. MDH’s statewide fish consumption guidelines recommend pregnant women and children eat these types of fish once a month or less.

Researchers said Asian women in the study, especially Hmong women, had the highest levels of mercury among all participants. Some Hmong women in Minnesota may have high mercury exposures from using skin-lightening products with mercury and from eating fish higher in mercury, researchers concluded.

Using skin-lightening products may also be putting Latina and East African women in danger of high mercury levels. Some Latina women in the study had high mercury in their urine, and East African women in the study had the second-highest urine mercury after Hmong women.

While mercury was the contaminant of chief concern, the study also tested participants for lead and cadmium levels. When pregnant women are exposed to these metals, they can affect fetal brain development. Fortunately, the study found very low levels of both metals.

MDH and its public health partners are using the MN FEET results to take action and shape programs to help women in certain communities have less contact with mercury. While existing MDH programs give advice about eating fish low in mercury, the MN FEET results can help target future efforts. Similarly, MDH provides information to the general public, health care providers and certain communities about the dangers of skin lightening products. But MN FEET showed that more work is needed to reach women who speak languages other than English and who were not born in the U.S. to make sure they know that some skin lightening products have mercury.