[Heavy metals (Pb, Cd, Cr and Hg) in the general adult population near an urban waste treatment plant in Biscay, Spain, in 2006].

Background: The possible emissions from a municipal urban solid waste treatment plant (MUSWTP) include heavy metals. The purpose of this study is to ascertain the levels of heavy metals in the blood and urine of the general population of Biscay.

Methods: The level of Pb was measured in 95 blood samples (BPb) and Cd, Cr and Hg in 93 urine samples (UCd, UCr, UHg) taken from adults in the general population of Biscay, Basque Country, in 2006. The samples were obtained in two areas with high traffic density in the metropolitan area of Bilbao close to an MUSWTP which had just commenced operation, a third area in downtown Bilbao with heavy traffic and at a distance from the area of influence of possible emissions from the MUSWTP, and a fourth area at a distance from the plant and with low traffic density. The objective was to select a minimum of 20 participants from each area, with an equal number of male and female subjects, and with half the subjects aged between 20 and 44 years and the other half between 45 and 69. A chi-squared test was used to study the association between categorical variables, Students t-test was used as a comparison of means test, and ANOVA was used for variables with two or more categories. A multiple linear regression model was used to adjust for confounding factors.

Results: The mean concentrations were: BPb: 2.68 microg/100ml; UCd: 0.54 microg/g creatinine; UCr: 0.51 microg/g creatinine; UHg: 0.65 microg/g creatinine.

Conclusion: No significant differences were observed between the areas. The single-factor and multifactor analyses showed that the BPb levels increased with age and were associated with the consumption of local horticultural products and with employment in the metallurgy sector. The UCd levels also increased with age, and higher levels were observed in the upper social classes as well as in women and smokers. The UCr levels were higher in areas at a distance from the MUSWTP and in the upper classes, and UHg levels were higher in women than in men.