Total mercury in hair as biomarker for methylmercury exposure among women in central Sweden - a 23 year long temporal trend study

Exposure to methylmercury (MeHg) through fish is a global public health problem. Exposure monitoringis essential for health risk assessment, especially in pregnant women and children due to the documented neurotoxicity. Herein, we evaluate a time series of MeHg exposure via fish in primiparous Swedish women, covering a time period of 23 years (1996e2019). The 655 included mothers were part ofthe POPUP study (Persistent Organic Pollutants in Uppsala Primiparas) conducted by the Swedish FoodAgency (SFA). MeHg exposure was assessed via measurements of total mercury (Hg) in hair using either cold vapor atomic fluorescence spectrophotometry or inductively coupled plasma mass spectrometry, showing very good linear agreement (R2 ¼ 0.97). Maternal characteristics and fish consumption were obtained via questionnaires. The median concentration of total Hg in hair was 0.38 mg/kg (range 0.17e1.5) in 1996 and 0.25 mg/kg (range 0.03e1.1) in 2019. On average the women consumed 11 ± 8.2 mealsof fish per month, and fish consumption was positively correlated with total Hg in hair (Spearmancorrelation: 0.39; p < 0.001). In multiple regression analyses, the geometric mean annual decrease oftotal Hg in hair was 2.5% (95% CI: -3.2, 1.8%). Total fish consumption increased up to 2011 (B: 0.32times/month per year; 95% CI 0.17, 0.46) after which it started to decline (B: -0.66 times/month per year;95% CI -0.92, 0.40). Moreover, both total Hg in hair and fish consumption was positively associated withmaternal age and education, and inversely associated with pre-pregnancy BMI. In conclusion, theexposure to MeHg via fish appears to be slowly declining among Swedish pregnant women