Airborne total gaseous mercury and exposure in a Venezuelan mining area

This paper presents a short-term monitoring study of total gaseous mercury (TGM) in air, and exposure to airborne mercury. The evaluation was carried out in polluted mining sites (El Callao, Venezuela), where for decades mercury has been used in diverse stages of gold mining activities. The contamination is mainly due to emission of Hg0 during gold amalgamation and burning, which can cause direct human health risks. Total gaseous mercury (TGM) in air was analysed in mill, jewellery and indoor house sites, and at different heights (height profiles near the surface) at polluted and not polluted sites. Mercury concentration in air was measured with a portable mercury analyser (Lumex Ra-915+). Time weighted average mercury (TWA) was calculated for the evaluation of mercury exposure. TWA values ranged between 0.28 microg m(-3) and >100 microg m(-3). These measurements were done during sunny and dry days. In the case of mills and gold workshops, the values were over the limit recommended by the World Health Organization to exposure (25 microg m(-3)) and NIOSH limit (50 microg m(-3)). Indoors in a house, the air Hg average value was 2.58 microg m(-3) exceeding EPA (0.3 microg m(-3)) and ATSDR (1 microg m(-3)) guidelines. The mercury concentration at different height profiles, varied between 1766 microg m(-3) and 0.014 microg m(-3). Mercury height profiles were described by a power function model of the form c(Hg) = ah(-b), where a parameter describes the magnitude of Hg emission. For polluted sites there was a significant correlation between a and Hg in soil or Hg emission from soil to air, while b is only significantly correlated with air temperature. An air and soil mercury measurement transect was carried out at a mill site up to a distance of 1000 m, and it was observed that the air mercury concentration decreases with increasing distance from the mill site, and inversely to Hg soil content.