BACKGROUND: Fish are an excellent source of nutrients such as omega-3 fatty acids, which are essential for maternal and fetal health; however, fish may also contain harmful contaminants such as methylmercury. The US EPA and FDA recommend that women of child bearing age consume 1-2 meals a week of fish low in mercury in order to maximize the health benefits, while keeping their body burden of mercury low (i.e., hair mercury below 1 ppm) to avoid harmful health effects. State and federal agencies issue complex fish consumption guidelines for this population to encourage consumption of a variety of fish and to avoid or limit certain species. Recent biomonitoring activities suggest that elevated mercury may be of concern among women of childbearing age in the Lake Superior basin. Thus, a clinical intervention was implemented in northern Wisconsin to educate women about mercury and fish consumption.
METHODS: Women of childbearing age (n=255) were recruited to participate in two study visits separated by six months. At each visit, a hair sample was collected and participants completed a detailed fish consumption questionnaire. Mercury hair levels exceeding 1 ppm triggered a case investigation for possible sources of exposure by examining fish consumption habits reported on the detailed surveys. Species-specific consumption frequencies were examined and compared to established fish consumption guidelines.
RESULTS: There were six cases of elevated hair mercury levels at baseline (range: 1.42 ppm-1.87 ppm) and 14 cases of elevated mercury at follow-up (range: 1.03 ppm – 2.62 ppm). Five cases exceeded the advice for the “do not eat” species, nine cases exceeded the advice for “up to one meal per month”, and three cases exceeded the advice for “up to one meal per week”. Six species were identified as the likely source of exposure to mercury: swordfish, albacore canned tuna, fresh tuna, king mackerel, light canned tuna, and walleye.
CONCLUSIONS: Future outreach efforts should include targeted messaging on the species frequently associated with elevated hair mercury levels, as well as outreach emphasizing the importance of following Wisconsin’s fish consumption advisories with increased focused on the importance of following the “up to one meal per month” category.