Health significance of human biomonitoring data obtained in areas with different environmental loads: Correlation between biomarkers of exposure and biomarkers of effect

Abstract

Introduction: Recently results have become available of a large-scale biomonitoring campaign in Flanders. The major goal was surveillance of the environmental health status of residents from different areas. Biomarkers of exposure and effects have been measured and referece values have been calculated. The hypothesis tested was whether living in different geographic areas resulted in significant differences in geometric means and P90 values of the different biomarkers. The significance of these findings for health risks was approached by studying associations between exposure and effect markers. Methods: A total of 1200 mother-child pairs and 1600 adolescents (14 to 15 years old) were systematically recruited in 8 distinct regions in Flanders (Northern part of Belgium), including rural areas, urban areas, and industrial sites. Inclusion criteria for participation in the campaign were residing at least 5 years in the area, giving written informed consent, and being able to fill in an extensive Dutch questionnaire on lifestyle factors, socioeconomic status, dietary habits, occupation and hobbies, and health status. Concentrations of lead, cadmium, polychlorobiphenyls, and 138,153,180, hexachlorobenzene, p,p′-DDE were measured in cord blood samples of the newborns and in blood samples from adolescents; additionally, dioxin-like activity (determined by means of the Calux bioassay) was measured in the cord blood samples and tt-muconic acid and 1-hydroxypyrene were measured in spot urine samples of adolescents. After correction for confounders such as age and smoking behavior, reference values for the biomarkers of exposure were calculated (geometric means and P90). From each of the participants, health effect indicators were obtained; these included biomarkers of effect (DNA comet assay, hormone levels in adolescents), data from existing health registers at the maternity hospitals and student support centers (growth characteristics), and data from questionnaires, which gave information on occurence of asthma and allergy in mothers and adolescents, fertility of the mothers, and growth and puberty development of the adolescents. Results: Statistical analysis using ANOVA revealed for most biomarkers significant differences in the geometric means of biomarkers of exposure between residents of different areas. Unexpectedly, all chlorinated compounds measured were significantly elevated in rural areas (P >0.05). Hypotheses on the correlations between exposure to chlorinated compounds and fertility, growth and development parameters were analyzed by regression analysis using all the available data from each cohort. This approach allowed to add some information to the surveillance program on health relevance of the exposure markers. Discussion: Exposure biomarkers and effect markers in the same study design give complementary information. Exposure markers are always a limited tool for environmental health surveillance since it is not possible to measure all potential contaminants. Effect markers, although much less specific for exposure to chemicals, have an additional role in surveillance provided that confounders and covariables are carefully taken into account.