RISK ASSESSMENT OF MERCURY IN ALTA-FLORESTA - AMAZON BASIN BRAZIL

In the last 15 years gold mining activity has been the main source of the mercury (1-18) emissions into the atmosphere in the Amazon Basin. The first phase of gold production takes place in remote areas. In gen eral the second one happens in the local urban area, where the gold is commercialized and sent to the great economic centers. In the last 3 years, this activity started to decline as a consequence of the high c ost of the gold production but in the Municipality of Alta Floresta, t he gold trade still plays an important role in the local economy. This paper addresses the assessment of the Hg exposure scenarios and their quantitative risk for inhalation of metallic Hg vapor and for ingesti on of total Hg, using indirect exposure measurements, for different ag e groups of the urban area of Alta Floresta. This work took into accou nt the field study which provided background information, such as char acteristics of local and regional environment, Hg concentrations in di fferent environmental media, and the character of the local urban popu lation. The mean levels of Hg in the atmosphere of the urban area rang ed from 210 ng/m(3) to 880 ng/m(3). Alta Floresta has no riverside pop ulation and there is a low fish consumption rate of 8 g/d among the ge neral population. However, mercury levels in focally consumed carnivor ous fish, ranged from 0.3 to 3.6 mg/kg, depending on the species and o n the period of the year. The levels of mercury in soil surrounding th e residential areas near the Hg emissions sources, ranged from 0.05 to 4.10 mg/kg. Hg in soil may represent an important source of mercury i ngestion for local children up to 4 years of age. The mean Hazard Inde x estimated for the general adult population was 1.4. For the general population, regarding the number of persons exposed in the urban area, inhalation of metallic Hg vapor is the main route of exposure. The re sults for water ingestion for all groups are negligible. For families of fishermen the Hazard Index was estimated to be 9.3, with a contribu tion of 92% from fish ingestion.