Hair Mercury Sampling for a Health Impact Assessment in Alaska

BACKGROUND: Mercury, a potent human neurotoxin that is particularly harmful to developing fetuses, is an important exposure concern for many Alaskans who consume large quantities of fish. Consequently, the Alaska Section of Epidemiology (SOE) maintains a hair mercury biomonitoring program to characterize statewide mercury exposure levels, but data from the Upper Kuskokwim River region (UKR) are limited.  The UKR is of particular concern due to its close proximity to a former mercury mine and the fact that many UKR people consume pike, which contain high mercury concentrations. To address this biomonitoring data gap, the Alaska Health Impact Assessment (HIA) Program--which is conducting an HIA on a newly proposed gold mine in the region--collected hair samples from UKR residents for mercury analysis.

METHODS: The HIA Program collected a convenience sample of hair specimens from women of childbearing age (WCBA; i.e., women aged 15–45 years) and other adults in selected UKR communities during May–September 2012. The HIA Program selected communities based on their proximity to the proposed gold mine and solicited volunteers during visits to various community offices. The Alaska Public Health Laboratory performed direct mercury analysis on the hair samples. The resulting data were analyzed using SPSS software. All participants received a follow-up letter with their results and mercury-related health information.  

RESULTS: A total of 186 hair samples were obtained from eight UKR communities. The overall median hair mercury level was 0.51 parts per million (ppm; range: 0.03–3.71 ppm). Median hair mercury levels were 0.38 ppm (range: 0.03–2.63 ppm) for WCBA (n=79), 0.58 ppm (range: 0.05–3.71 ppm) for women aged >45 years (n=66), and 0.77 ppm (range: 0.13–3.64 ppm) for males (n=41). Overall, increasing median hairy mercury levels were weakly associated with increasing age (r²=0.28, p<0.05); mercury levels did not differ significantly by community. The median hair mercury levels among WCBA were lower than the statewide median (0.44 ppm, range: 0.01–7.82). All results fell below the Agency for Toxic Substances and Disease Registry’s No Observed Adverse Effect Level of 15.3 ppm.

CONCLUSIONS: These data provide reassurance to program participants and community members in the region at large that they are not being exposed to concentrations of environmental mercury that represent an imminent health threat. These data also help promote the consumption of subsistence foods, which confer numerous health, social/cultural, and economic benefits to the people of Alaska.