Prenatal methylmercury exposure and developmental outcomes: review of the evidence and discussion of future directions.

I conducted a review of the published literature to assess the strength of the evidence for an association between prenatal exposure to methylmercury (MeHg) and subsequent child development. I identified 12 studies on this subject published since 1980. Of these, 3 were longitudinal studies--2 conducted in the Seychelle Islands, and 1 in the Faroe Islands. Nine were cross-sectional studies conducted in different countries where seafood, a source of MeHg, constituted a major part of the diet. The ages of the children studied ranged from 2 weeks to 12 years. The results of the longitudinal studies were contradictory. Researchers in the Faroe Islands identified an association between MeHg exposure and developmental effects, whereas those in the Seychelle Islands identified no such association. This inconsistency was mirrored in the results of the cross-sectional studies where there were some positive and some negative findings. It was concluded that it was not possible from currently available data to determine whether there is an association between prenatal MeHg exposure and adverse developmental effects in children. In advance of future research, consideration should be given to resolving the uncertainties surrounding exposure assessment and outcome measurement, as both elements varied between studies. It was suggested that questions of exposure assessment would benefit from the application of an expert review process. Outcome assessment would benefit from the development of theoretically based measures of specific aspects of cognitive functioning to replace the relatively crude measures of attainment and IQ currently employed in most studies. This would assist in the development of classic longitudinal studies by allowing repeated assessment over the full age range and providing data that are more readily interpretable and comparable between studies.

Models of unexplained symptoms associated with occupational and environmental exposures.

Unexplained illnesses characterized by nonspecific, multisystem complaints are often attributed to occupational or environmental chemical exposures. This raises difficulties for the regulatory authorities, who are frequently unable to agree on the existence, nature, or source of such illnesses. It is proposed that many of these difficulties derive from an adherence to a traditional medical model of disease and that the application of a biopsychosocial approach would be more effective for both research and individual case management. A number of models derived from the field of health psychology are discussed in terms of their application to occupational and environmental syndromes. A specific example is described that relates to the health problems experienced by sheep farmers in the United Kingdom who are exposed to organophosphate-based pesticides. The source of their complaints and the responses of the health professionals and the regulatory authorities are discussed within the context of a biopsychosocial approach that focuses on illness rather than on organic disease as the unit of study and explores the interaction between the various physical and psychosocial variables involved. It is proposed that this approach, which is already well established in the fields of human and social sciences, should be adopted more readily by those concerned with occupational and environmental epidemiology.

Recent developments in low-level lead exposure and intellectual impairment in children.

In the last decade children's blood lead levels have fallen significantly in a number of countries, and current mean levels in developed countries are in the region of 3 Mu g/dL. Despite this reduction, childhood lead poisoning continues to be a major public health problem for certain at-risk groups of children, and concerns remain over the effects of lead on intellectual development in infants and children. The evidence for lowered cognitive ability in children exposed to lead has come largely from prospective epidemiologic studies. The current World Health Organization/Centers for Disease Control and Prevention blood level of concern reflects this and stands at 10 Mu g/dL. However, a recent study on a cohort of children whose lifetime peak blood levels were consistently less than 10 Mu g/dL has extended the association of blood lead and intellectual impairment to lower levels of lead exposure and suggests there is no safety margin at existing exposures. Because of the importance of this finding, we reviewed this study in detail along with other recent developments in the field of low-level lead exposure and children's cognitive development. We conclude that these findings are important scientifically, and efforts should continue to reduce childhood exposure. However, from a public health perspective, exposure to lead should be seen within the many other risk factors impacting on normal childhood development, in particular the influence of the learning environment itself. Current lead exposure accounts for a very small amount of variance in cognitive ability (1-4%), whereas social and parenting factors account for 40% or more.

The mental health of Chinese immigrants in Birmingham, UK.

OBJECTIVES: The objectives of this study were to describe the life experiences associated with migration to the UK and to explore in-depth information about the process of life adjustment to migration and the circumstances of mental health in Chinese immigrants living in a large city area. METHOD: A two-part research strategy using both quantitative and qualitative methods was employed. In the cross-sectional quantitative survey, 113 Chinese respondents completed a questionnaire investigating demographic factors, life experiences associated with migration, proficiency in the English language and mental health status. In the qualitative phase of the research, interviews were conducted with a further 24 immigrants to explore these factors in more depth. RESULTS: In the questionnaire survey, over 60% of the group reported symptoms of poor mental health. Qualitative research shows that for those who were employed in catering, psychological adjustment was heavily dependent on strong ties with the Chinese community and there was minimal contact with the host society. By contrast, those concerned with professional development experienced conflict as a result of a high perceived need for integration and a recognition of the problems associated with this. CONCLUSION: The psychological distress experienced by immigrants of Chinese origin continues to be a largely invisible cause for concern.