Abstract
Exposure to methylmercury (MeHg) through fish is a global public health problem. Exposure monitoring is 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 (1996-2019). The 655 included mothers were part of the POPUP study (Persistent Organic Pollutants in Uppsala Primiparas) conducted by the Swedish Food Agency (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=0.97). Maternal characteristics and fish consumption were obtained via questionnaires. The median concentration of total Hg in hair was 0.38mg/kg (range 0.17-1.5) in 1996 and 0.25mg/kg (range 0.03-1.1) in 2019. On average the women consumed 11±8.2 meals of fish per month, and fish consumption was positively correlated with total Hg in hair (Spearman correlation: 0.39; p<0.001). In multiple regression analyses, the geometric mean annual decrease of total Hg in hair was-2.5% (95% CI: -3.2,-1.8%). Total fish consumption increased up to 2011 (B: 0.32 times/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 with maternal age and education, and inversely associated with pre-pregnancy BMI. In conclusion, the exposure to MeHg via fish appears to be slowly declining among Swedish pregnant women.
Highlights
Fish is considered to be a part of a healthy diet, the simultaneous exposure to environmental contaminants present in fish raises concern for human health (Mozaffarian and Rimm, 2006)
We explored the association of total Hg in hair and year of collection categorized into 5-year intervals (1996e2000, 2001e2006, 2007e2011, 2012e2016, !2017) using 1996e2000 as the reference category
It should be noted that about 5% of the women reported that they did not consume fish, but still total Hg was detected in their hair
Summary
Fish is considered to be a part of a healthy diet, the simultaneous exposure to environmental contaminants present in fish raises concern for human health (Mozaffarian and Rimm, 2006). Exposure to methylmercury (MeHg) occurs almost exclusively via consumption of fish and seafood (EFSA, 2012). The MeHg concentrations have been shown to vary widely between different species of fish, and the highest concentrations have been found in predatory fish (EFSA, 2012). The ingested MeHg is efficiently absorbed in the gastrointestinal tract (Aberg et al, 1969), after which it is distributed to all tissues in the body, readily passing the blood-brain and placenta barrier (Berlin and Ullberg, 1963; Reynolds and Pitkin, 1975). The target organ for MeHg toxicity is the brain, which is especially susceptible during development (EFSA, 2012; NRC, 2000). Based on the established neurotoxicity of MeHg, several authorities, including the Swedish Food Agency (SFA), have established recommendations to pregnant and breastfeeding women concerning restricted consumption of certain fish species. It is highly important to conduct biomonitoring of exposure to MeHg in susceptible groups such as pregnant women
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