Prenatal mercury exposure via mother's diet can impair certain brain functions.

2004 MAR 4 - (NewsRx.com & NewsRx.net) -- High levels of mercury passed from mother to child in utero were shown in a study to produce irreversible impairment to specific brain functions in children.

An international team of researchers published the findings in the February 2004 issue of the Journal of Pediatrics.

With methylmercury a worldwide contaminant of seafood and freshwater fish and known to produce adverse nervous system effects, especially during brain development, researchers from the Harvard School of Public Health and institutions in Japan, Denmark, and the Faroe Islands undertook an assessment of possible brain function impairment in adolescent children due to prenatal exposure to mercury when the mothers' diet was high in seafood.

The Faroe Islands are located in the North Atlantic Ocean between Norway and Iceland. The islands' economy is centered on the fishing industry and fish processing. The diet of the inhabitants includes high intake of seafood and whale meat.

Some 1,022 mothers and their children participated in the research. Mercury exposures among the children in the study were assessed through analyses of cord blood samples at birth and hair samples taken at ages 7 and 14. The mothers' hair mercury levels at childbirth in most cases exceeded 1 microgram per gram, the exposure limit recommended by the National Research Council and the U.S. Environmental Protection Agency (EPA). Follow-up testing of the children showed much lower exposure levels. At the most recent follow-up, more than 850 14 year olds participated in the study.

To assess the impact of the exposure to mercury, brainstem auditory evoked potentials (BAEP) were recorded using surface electrodes placed on the skull. At two different sound frequencies, the researchers measured the transmission of electrical signals in the brain from the acoustic nerve, via the pons (connecting the medulla oblongata to the thalamus) to the midbrain.

They found that the latency of the electrical transmission from the acoustic nerve to the pons was significantly increased at higher intrauterine exposure to mercury. This observation was found to be true both at 7 years and at 14 years, suggesting that this effect is lasting.