Academic journal article Environmental Health Perspectives

A State-of-the-Science Review of Mercury Biomarkers in Human Populations Worldwide between 2000 and 2018

Academic journal article Environmental Health Perspectives

A State-of-the-Science Review of Mercury Biomarkers in Human Populations Worldwide between 2000 and 2018

Article excerpt

Introduction

Mercury is a pollutant of global concern largely because of its adverse effects on human health. The current state of knowledge concerning the human health impacts of mercury has been extensively reviewed by international agencies (IPCS 1990, 2003; JECFA 2007a, 2007b, 2011; EFSA CONTAM Panel 2012) as well as by national agencies and other authors (ATSDR 1999; NRC 2000; U.S. EPA 1997, 2001; Clarkson and Magos 2006; Eagles-Smith et al. 2018; Ha et al. 2017; Karagas et al. 2012).

All populations worldwide are likely exposed to some amount of mercury (UNEP/WHO 2008). Human exposures to elemental and inorganic mercury may occur in occupational settings [e.g., in artisanal and small-scale gold mining (ASGM) and dentistry], from contact with certain products (e.g., dental amalgams, some skin-lightening creams, broken fluorescent bulbs and other waste products), and from environmental contamination (Mergler et al. 2007; ATSDR 1999; Clarkson and Magos 2006; UNEP/WHO 2008; Eagles-Smith et al. 2018; Ha et al. 2017). Mercury released into the environment may be converted by microorganisms to methylmercury, which bioaccumulates and biomagnifies through the food web, particularly in aquatic systems (Obrist et al. 2018). Seafood is the main source of protein for about 1 billion people worldwide (FAO 2014). Sampling of seafood has found widespread methylmercury contamination (Sioen et al. 2009; GEMS/ Food Contaminants 2018), with some widely consumed predatory species (e.g., tuna, swordfish, grouper, mackerel) being among the most highly contaminated (GEMS/Food Contaminants 2018; Groth 2010). Therefore, for many communities, dietary consumption of contaminated fish, shellfish, and marine mammals is an important source of exposure. Other foods, such as rice grown in sites heavily contaminated with mercury, may also represent a source of exposure for some communities (Rothenberg et al. 2014).

The entry into force of the Minamata Convention on Mercury on 16 August 2017 signaled the global commitment by governments to reduce the use and environmental release of mercury in order to protect human health and the environment (Article 1) (UNEP 2017). Notably, Convention Article 16 is titled "Health Aspects," and Article 19 ("Research, Development and Monitoring") emphasizes a need to focus on vulnerable populations (19.1c) and to follow harmonized methods (19.1d). Article 22 describes the process for evaluating the effectiveness of the convention, which includes monitoring trends in human exposure. The onus is now on parties to the convention to develop and implement strategies and programs to identify and protect populations at risk of exposure, particularly vulnerable populations; to set targets for mercury exposure reduction; and to develop means for assessing the effectiveness of control measures, for example, by monitoring human exposure to mercury.

Human exposures can be assessed through the measurement of mercury concentrations in a number of different biological sample types, and key approaches for mercury biomonitoring have been reviewed by UNEP/WHO (2008) and the U.S. EPA (1997). The most commonly used biomarkers are the concentrations of mercury in hair, urine, blood, and cord blood, and their selection can depend on factors such as the potential source of exposure, chemical form, and exposure life stage. Here we briefly elaborate on these biomarkers.

Analysis of hair is commonly used to assess exposure to methylmercury, which accounts for 80-90% of the total mercury content within this matrix (Clarkson and Magos 2006; UNEP/WHO 2008; NRC 2000). Once incorporated, the mercury remains in the hair, and this biomarker can therefore provide an integrated measurement of internal exposure to methylmercury. Because hair grows at approximately 1 cm per month, exposure can be tracked over time by careful sampling. Hair has the advantage that it is easy to collect and transport, although, based on the authors' experiences in several countries, there may be cultural objections to taking hair samples in some communities. …

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