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Brussels, 8 June, 1999

Exposure to mercury before birth may cause high blood pressure

Keywords: health, environment, mercury

A long-term research project in the Faeroe Islands, co-financed by the European Commission, has demonstrated that even low-level exposure to mercury before birth is associated with a risk of developing high blood pressure. The results will be published in the July issue of "Epidemiology". At the same time, another EU-funded study in Madeira has confirmed earlier findings in the Faeroes indicating that prenatal mercury exposure could cause delays in neurological development. The results of this study will be published in the July/August edition of "Neurotoxicology and Teratology". The new findings are being discussed by experts from WHO and FAO, who are meeting in Rome to discuss the safe limits of exposure to mercury from fish.

Increased exposure to mercury can occur in communities whose diet is based on seafood. Following a study in the Faeroes, where the traditional diet includes a large element of whale-meat, an international research project co-funded by the European Union under its Environment and Climate research programme, examined 149 children from a fishing village on Madeira. Their mercury exposure comes mainly from a deep-sea fish named the black scabbard, a predatory species that accumulates mercury. Mercury exposures in the Madeira community were found to be even higher than on the Faeroes. In agreement with the findings on the Faeroe Islands, the researchers found that electrical signals from the brain, the "evoked potentials", tended to slow down when the children had been exposed to higher concentrations of mercury. The results of this study will be published in the July/August edition of the journal Neurotoxicology and Teratology.

Perhaps the most intriguing finding, however, relates to blood pressure. In a separate study, researchers examined the results from the Faeroes and found that exposure to mercury before birth is associated with a greater risk of developing high blood pressure. Hypertension is a main determinant of cardiovascular disease, and the risk factors involved in early stages of increased blood pressure during childhood and adolescence are therefore of considerable clinical and public-health interest. The researchers measured blood pressure at age 7 years and were surprised to see that it tended to increase even at very small increases of mercury exposure. No further increase was seen at high mercury exposure levels. The results will be published in the July issue of the journal Epidemiology.

"We have been very worried about the effects on brain function, because they suggest that prenatal mercury exposure will cause lasting effects on cognitive functions," says Professor Grandjean, who coordinated the research. "However, the new findings on blood pressure suggest that mercury may also contribute to the development of serious diseases and perhaps mortality."

The German government has recently taken steps to decrease its exposure limits for mercury. However, the new findings revealed that even doses of mercury below the new German limit correlated with increased blood pressure. In fact, above this limit, no clear effect was seen. Thus, contrary to expectation, the association occurred within an exposure range characteristic of communities not depending on marine food.

The new findings are being considered by the WHO-FAO experts, who will decide this week whether to recommend lower limits internationally.

For further information, please contact:

Prof. Philippe Grandjean, M.D.
Institute of Community Health, Odense University
Fax: +45.6591.1458
E-mail: p.grandjean@winsloew.ou.dk

Mr Stephen Gosden
Press and Information Officer, DG XII
Fax: +32.2.29.58220
E-mail: Stephen.Gosden@ec.europa.eu

Abstract of the paper to be published in Epidemiology,
and presented at the 5th International Conference on Mercury as a Global Pollutant,
23-28 May 1999, Rio de Janeiro, Brazil

Prenatal methylmercury exposure as a cardiovascular risk factor at seven years of age

Nicolina Sřrensen (1), Katsuyuki Murata (2), Esben Budtz-Jřrgensen (3), Pál Weihe (1,4) and Philippe Grandjean (4,5)

1. Department of Occupational and Public Health, Faeroese Hospital System, Tórshavn, Faeroe Islands;
2. Department of Public Health, Faculty of Medicine, University of Tokyo, Tokyo, Japan;
3. Department of Biostatistics, Panum Institute, University of Copenhagen, Copenhagen, Denmark;
4. Institute of Community Health, Odense University, Odense, Denmark; and 5
5. Departments of Environmental Health and Neurology, Boston University Schools of Medicine and Public Health, Boston, MA

Correspondence to P Grandjean, Department of Environmental Medicine, Winslřwparken 17, DK-5000 Odense C, Denmark.

Supported by grants from the U.S. National Institute of Environmental Health Sciences (ES06112), the European Commission (Environment and Climate Research Programme), the Danish Medical Research Council, and the Dannin Foundation.

Abstract

Blood pressure in childhood is an important determinant of hypertension risk later in life, and methylmercury exposure is a potential environmental risk factor. A birth cohort of 1,000 children from the Faeroe Islands was examined for prenatal exposure to methylmercury, and at age seven years, blood pressure, heart rate, and heart rate variability were deter mined. After adjustment for body weight, diastolic and systolic blood pressure increased by 13.9 mm Hg (95% CI = 7.4- 20.4) and 14.6 mm Hg (95% CI = 8.3-20.8), respectively, when cord blood mercury concentrations increased from 1 µg/l to 10 µg/l cord blood. Above this level, which corresponds to a current exposure limit, no further increase was seen. Birth weight acted as a modifier, with the mercury effect being stronger in children with greater birth weights. In boys, the heart rate variability decreased with increasing mercury exposures, particularly from 1 µg/l to 10 µg/l cord blood where the variability was reduced by 47% (95% CI = 14-68%). These findings suggest that prenatal exposure to methylmercury may affect the development of cardiovascular homeostasis.

Abstract of paper to be published in the July/August of "Neurotoxicology and Teratology"

Delayed Evoked Potentials in Children Exposed to Methylmercury from Seafood

Katsuyuki Murata (1), Pal Weihe (2,3), Aristeo Renzoni (4), Frodi Debes (2), Rui Vasconcelos (5), Francis Zino (6), Shunichi Araki (1), Poul J Jřrgensen (7), Roberta F White (3,8,9), Philippe Grandjean (3,9)

1. Department of Public Health, University of Tokyo, Tokyo, Japan
2. Department of Occupational and Public Health, Faeroese Hospital System, FO-100 Tórshavn, Faeroe Islands
3. Institute of Community Health, Odense University, DK-5000 Odense, Denmark
4. Department of Environmental Biology, University of Siena, Siena, Italy
5. Funchal General Hospital, Funchal, Madeira, Portugal
6. General Practice, Funchal, Madeira, Portugal
7. Department of Clinical Chemistry, Odense University Hospital, DK-5000 Odense, Denmark
8. Departments of Neurology and Environmental Health, Boston University Schools of Medicine and Public Health, Boston, MA 02118
9. Environmental Hazards Center and Department of Psychology, Boston Department of Veterans Affairs Medical Center, Boston, MA 02130

Editorial correspondence to:

Philippe Grandjean
Odense University
Winslowparken 17
5000 Odense
Denmark
Phone: +45-6557.3769.
Fax: +45-6591.1458.
Email: p.grandjean@winsloew.ou.dk

Abstract

Methylmercury poisoning may cause constriction of visual fields and deafness, especially if exposure occurs prenatally. However, the risks associated with exposure from contaminated seafood is unclear. We examined 149 children attending first grade in a Madeiran fishing community. As maternal dietary habits were relatively unchanged, current maternal hair concentrations were used as indicator of the child's prenatal exposure to methylmercury [geometric average, 9.64 µg/g (48.2 nmol/g)]. After adjustment for age and sex, the mean (+SD) latency of peak III of the brainstem auditory evoked potentials at 40 Hz was increased by 0.128 + 0.047 ms when maternal hair-mercury concentrations exceeded 10 µg/g (50 nmol/g) (p for association, 0.002), and the increase of the N145 pattern-reversal visual evoked potential latency at 15' was 3.16 +1.57 ms (p for association, 0.002). No such relationships were seen with the child's own hair- mercury concentration, and other clinical examinations revealed no mercury-associated deficits. Neurophysiological evidence of adverse effects on brain function are relatively independent of confounders and should be considered in the risk assessment of this seafood pollutant.

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