Session Title :

Health effects of mercury: the Seychelles Child Development Study perspective

Synopsis :

In this session, we will describe the setting, conduct, design, and summary of recent research findings from the Seychelles Child Development Studies (SCDS). Implications of mercury research on communities routinely exposed due to regular fish consumption will be discussed, with a special emphasis on the SCDS and Republic of Seychelles.

Description :

Mercury exposure from fish consumption and placement of dental amalgams has been of significant public health concern. All fish contain small amounts of methylmercury (MeHg), which is especially toxic to the developing nervous system at elevated exposure levels. However, about 20% of the world’s population derives at least one-fifth of its animal protein intake from fish, and protein intakes from fish are crucial in countries where the total protein intake is low. Fish also contains a variety of essential nutrients, including omega-3 long chain polyunsaturated fatty acids, selenium, iodine, and certain vitamins. Concerns remain regarding the safety of dental amalgams due to the potential for exposure to mercury vapor (Hg0). A number of epidemiological studies of neurobehavioral development in children have been conducted to investigate whether any risks are associated with Hg exposure from daily ocean fish consumption or dental amalgam placement, but results remain inconclusive.

For almost three decades, the Seychelles Child Development Study (SCDS) has examined potential adverse effects of prenatal MeHg exposure from fish consumption on neurodevelopmental outcomes. More recently, the SCDS has also investigated influences of maternal and child dental amalgams on such outcomes. The Seychelles population has many similarities to other countries worldwide and can therefore serve as a sentinel for the risks and benefits of fish consumption and potential harms of amalgam use. For example, exposure to MeHg is about 10 times higher than in the US due to a diet high in fish, and exposure to Hg0 is also substantial because of the routine use of dental amalgams.

In this session, we will describe the setting, conduct, and study design of SCDS, followed by a summary of recent research findings addressing the developmental influences of pre- and postnatal exposure to MeHg as well as Hg0. In addition, we will provide an overview of the statistical challenges associated with studies of low-level environmental exposure to toxicants and human health effects, including covariate selection, assessment of interaction, and statistical inference, and how we handled these challenges in our SCDS studies. We will also discuss the assessment of nutrients in fish, their correlation with MeHg and self-reported measures of fish consumption, and the challenges of extrapolating findings based on biomarkers to actual measures of intake. Finally, we will describe the implications of mercury research on communities potentially routinely exposed due to regular fish consumption, with a special emphasis on the SCDS and Republic of Seychelles.