Exposure Assessment of Pregnant Portuguese Women to Methylmercury Through the Ingestion of Fish: Cross-Sectional Survey and Biomarker Validation

Abstract

Methylmercury (MeHg) contamination is a critical public health problem in Portugal, where fish is an important component of the daily diet. The Portuguese are the third largest consumers in the world (after Japan and Iceland) but first in Europe. Prenatal exposure to MeHg is believed to be linked to fetal/child neurodevelopment and behavioral impairments due to the neurotoxicity of the compound. The objective of this study was to assess the exposure of pregnant Portuguese women to mercury (Hg) due to fish consumption, calculating the indices of risk and confirming exposure through analyses of a biomarker of exposure. The study consisted of a cross-sectional evaluation of 343 pregnant women recruited at their visit to two antenatal care units in Lisbon, Portugal. A food frequency questionnaire was used to estimate prenatal exposure. Total Hg levels in hair were analyzed by atomic absorption, in samples from 186 women. The average fish consumption was 3.1 meals per week. Median Hg level in the hair was 1.26 μg/g (range: 0.07–5.3 μg/g). The mean calculated risk index was 0.81; however, 28% of the pregnant women ingested levels above the provisional tolerable weekly intake (PTWI) level recommended by the World Health Organization (WHO; 1.6 mg/kg per body weight), indicating the possibility of risk due to MeHg exposure. Multiple linear regression analysis showed the risk index was reliably predicted from predatory fish species and number of fish meals consumed per week. Ingestion of black and silver scabbard fish as well as mixed predatory fish cooked in traditional dishes enhanced the toxicity risk. In conclusion, some exposure levels exceeded the reference value; therefore, nutritional counseling needs to be provided to populations at risk.