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Background and aims: One of the goals of human biomonitoring by the Flemish Centre of Environment and Health was to investigate exposure-response associations for various biomarkers of exposure and effect. The aim of this study is to describe the results of the exposure-effect associations involving exposure to metals and metalloids. Methods: Participants donated blood and/or urine for determination of concentrations of metals and metalloids (by ICP-MS) and biomarkers of effect (by various analytical methods). All subjects filled in a questionnaire to provide information on health, life-style and personal factors. The age groups sampled were mother-newborn pairs (maternal and cord blood), 14-15 year old adolescents (blood and urine) and 20-40 year old adults (urine). Regression models were fitted to determine associations between effect- and exposure markers, adjusted for relevant confounders and covariates (e.g. smoking, age, gender). Results: Many significant associations were in line with previously reported findings, while some were not published before. The size of newborns was negatively correlated with cord blood As, and positively with Cu. For adolescent girls, blood and urinary Tl were negatively correlated with development of pubic hair and breasts. In boys negative correlations were found between urinary Tl and pubic hair development, and between both urinary Tl and blood Pb and genital development. In adolescents, urinary Cd showed a negative correlation with the T4 thyroid hormone and a positive correlation with an indicator of DNA damage, while urinary Cd and urinary Cr showed positive correlation with indicators of kidney damage. Various correlations were found between metals and sex hormones (aromatase, SHBG, testosterone, estradiol) in boys. In adults, there was only a significant negative association between urinary As and blood platelet aggregation. Conclusions: Many exposure-effect associations were supported by the literature, some were reported earlier in a previous cycle of the Flemish human biomonitoring.

In 2002, the Centre for Environment and Health in Flanders, Belgium started a human biomonitoring program (FLEHS I). For 1679 adolescents, residing in nine study areas with differing pollution pressure, exposure to the pesticides p,p'-DDE and HCB, hormone levels and the degree of sexual maturation were measured. Possible confounding effects of lifestyle and personal characteristics were taken into account. In 2007, a second cycle of the Flemish human biomonitoring program (FLEHS II) started. The main purpose was generating reference values for several biomarkers, both of exposure and of effect, and establishing dose-effect relationships. In this survey, not only the pesticides p,p'-DDE and HCB were measured, but also metabolites from organophosphate pesticides and para-dichlorophenol (2,5-DCP), a metabolite of para-dichlorobenzene. Data on internal exposure of the pesticides p,p'-DDE and HCB showed a positive correlation with sexual maturation and the aromatase index for boys and with free T4 (both boys andgirls), while a negative association with sexual development in girls was found. For HCB also a positive correlation was found with testosterone (boys) and TSH levels in the blood (boys and girls). The organophosphate pesticide metabolites were negatively associated with sex hormone levels in the blood of the boys and with sexual maturation (both boys and girls). The pesticide metabolite 2,5-DCP was negatively correlated with free T4, while a positive association with TSH was reported (boys and girls). These results show that even relatively low concentrations of pesticides can have significant influences on hormone levels and the degree of sexual maturation in 14-15 year-old adolescents.

Environmental justice research suggests that inequalities in the distribution of environmental quality systematically disadvantage the lower social strata of society. The effects of these inequalities on the human exposure to specific chemical pollution remain, however, to a large extend unknown, especially in hotspot areas where surrounding neighbourhoods are exposed to a mixture of diverse pollution. In Flanders, the northern part of Belgium, a community-based participatory approach was set up between 2009-2010 to collect blood, urine and hair samples of 197 socially and ethnically diverse adolescents (14-15 years of age) living in the close proximity of a non-ferro industrial area. We conduct a socio- stratification of human biomonitoring results by associating the internal body concentration of three types of chemical pollution (heavy metals, POPs and volatile compounds) with individual socioeconomic status (SES) and ethnic background. Social gradients in exposure to these chemicals are assessed with geometric means, using multiple regression models, controlling for covariates and confounders. Our results show that, depending on the (type of) pollutant, adolescents with a lower SES can either have higher or lower internal concentrations. Socially constructed factors, such as dietary and lifestyle habits, play an important role in these relations. We conclude that when assessing the human exposure concentrations of pollutants, more complex patterns of social stratification emerge than can be assumed on the basis of the environmental justice hypothesis. It therefore remains important to consider the chemical environment in relation to the social environment when monitoring environmental health risks. By emphasising on transparent communication and relevant interaction between residents, local stakeholders and scientists, monitoring environmental health could enhance the empowerment of socioeconomically disadvantaged communities.

Since 2002 a human biomonitoring network has been established in Flanders (Belgium) as part of a programme on environmental health surveillance. The human biomonitoring network should support environmental health policy by identifying priorities for further action. The first cycle of the programme (2002-2006) confirmed the hypotheses that living in areas with different environmental pressure is reflected in different loads of environmental chemicals in the residents. In the second cycle of the programme(2007-2011) the number of environmental chemicals for which human biomonitoring data were obtained was expanded substantially. The goal of the Flemish programme is to use and translate the scientific results into policy actions. Its further orientation in the second cycle to human biomonitoring in hot spots and sensitive age groups or susceptible persons with underlying complications (e.g.persons with diabetes) are linked to these goals. Interaction with stakeholders is embedded in the programmeemphasizing transparency of the choices that are made and direct communication. The Flemish human biomonitoring programme is organized centrally with major involvement of research partners from different disciplines which allows engrafting environmental health research on the programme. One of the major focuses is the question whether combinations of pollutants in the general population are associated with biological effects. The objective of this paper is to review and discuss the options that were taken in the human biomonitoring programme in order to achieve its goals.