Health effect studies
A meta-analysis refers to methods focused on contrasting and combining results from different studies to show a pooled effect. Meta-analyses of published epidemiological studies were conducted within ArcRisk to find out the blood concentration value which statistically significantly distinguishes a low exposure group from a high exposure group, to show possible health problems among population when exceeding this value.
The meta-analyses conducted in the ArcRisk project included the following selection criteria:
1) Inclusion of data on the association of some of the target substances with health outcomes.
2) Recently published articles (after year 2000) containing AMAP – protocol chemicals and the general human population.
A database with information regarding health effects and environmental exposures in the Arctic has been developed. This database includes previous AMAP cross sectional studies as well as other studies from the literature with quantitative data about exposures. Meta-analyses based on the information in this database were performed for sex-ratio (PCBs), birth weight (PCBs), child development - metabolic syndrome (Hg), and premenopausal breast cancer (PCBs).
Meta-analysis of the link between sex ratio and PCBs
A total of 140 articles were identified in a first screen of relevant studies, for which abstracts were reviewed. In the second step, 51 original articles were considered as relevant studies and they were retrieved for detailed evaluation. After full review, 27 articles met at least one of the exclusion criteria, and thus were excluded. Finally, 24 studies were included in review.
The meta-analysis showed that the high maternal PCB concentration seems to be slightly associated with low birth weight (Nieminen et al, manuscript in press).
Meta-analysis of the link between birth weight and PCBs
A total of 140 articles were identified in a first screen of relevant studies, for which titles and abstracts were reviewed. In the second step, 51 original articles were considered as relevant studies and they were retrieved for detailed evaluation. After full review, 27 articles met at least one of the exclusion criteria, and thus were excluded. Finally, 24 studies were included in review.
The meta-analysis showed that the high maternal PCB concentration seems to be slightly associated with low birth weight. For detailed methodological description and results see Nieminen et al, manuscript in press.
Meta-analysis of the link between child development and mercury
The first objective was to assess whether statistical reporting and poorly defined research questions (including several outcome variables and exposure variables) are associated with preferential reporting to the readers of statistical significant findings. The second objective was to point out the complexities and potential problems in literature retrieval of association between broadly defined outcome variable and one primary quantitative explanatory variable when the exposure measurement methods and controlling of other potential covariates varies between the reviewed studies. Finally, 82 studies were included in this literature evaluation.
Examples of possible effects on neurodevelopment are: motor and verbal skills, visual-motor and memory functions, behaviour, with putative hyperactive and attention deficit, and various visual functions (Julvez and Grandjean 2009).
