BIOMONITORING OF URINARY MERCURY IN FAMILIES LIVING IN THE VICINITY OF A CHLOR-ALKALI PLANT: EVALUATION IN TWO SUCCESSIVE YEARS

The mercury cell chlor-alkali plants have been identified as major sources of mercury input into to the environment. However, the information about background exposure of human populations to mercury is very limited. The main purpose of this study was to evaluate the urinary mercury levels in two parishes (Beduído and Veiros) surrounding the Estarreja Chemical Complex (ECC) and from a reference parish (Ouca), in two consecutive years, 2011 and 2012. The ECC, in North-Western Portugal, consists of several industrial units, namely, a chlor-alkali plant which used, for more than 4 decades, to produced chlorine and caustic soda by the mercury cell process. In 1994 this plant began to change the production process which was concluded in 2002. Some recent studies still indicate the presence of mercury in soils, groundwater, forage plants and crops (eg tomato and cabbage).

In order to evaluate the urinary mercury levels in children and their mothers living in the vicinity of the ECC, a total of 53 families provided two morning urine samples, one from the mother and other from her child (7-15 years). A total of 42 families living in the vicinity of the ECC and 11 families living in a control area were studied. According to the results 95% of the individuals selected lives in these places for more than ten years. All families have answered a questionnaire regarding their diet and health, among other aspects.

The most important conclusion of this study is that all urinary Hg levels are lower than 10 µg l^-1, the level normally expected in an asymptomatic population. In global terms there are no significant differences in exposure to Hg between the populations of Estarreja and Ouca. The levels are slightly higher in the survey of 2012. Nevertheless, and for both years, there are significant differences between the two parishes of Estarreja: in Veiros, more rural and more affected by the ECC, the levels of urinary mercury are higher.