Metal and Metalloid Contaminants in Atmospheric Dust and Aerosol Near an Active Copper Smelter

Abstract

Environmental lead (Pb) and arsenic (As) contamination still represents a potential health issue in many communities under the influence of smelter activities around the world. Activities associated with mining operations including ore smelting and mine tailings management, generate airborne metal and metalloid contaminants in a wide range of particle sizes. While fine particles (< 1µm diameter) are generated by smelting processes, coarse particles (> 1µm diameter) are produced by mechanical processes such as crushing of ore and wind erosion of mine tailings. Particle size determines the fate and transport of these contaminants in the environment and in the human respiratory system, while their content in toxic substances determines the potential risk. Fine particles can penetrate deeper in the human respiratory system.Dust and aerosols contaminated with metals and metalloid such as Pb and As have the potential of deteriorate the human health depending on the particle size and chemical composition. The main objective of this research was to determine the degree of effectiveness of penetration of dust and outdoor suspended particles containing Pb and As emitted from an active smelter complex into a school indoor environment, based on the size and composition of the particles. For this purpose, two Micro-Orifice Uniform Deposited Impactor (MOUDI) samplers were operated simultaneously in the outdoor and indoor sampling of a school located in the vicinity of an active smelter in Southern Arizona. The results showed that airborne fine particles penetrate to the indoor environment, but in a relative reduced amount due to removal of coarse particles by mechanical filtration of the outdoor air. The indoor fine fraction concentrations were around 50% of the corresponding outdoor values, however, the indoor mass concentrations of lead and arsenic, as well as mass ratio Pb/As were similar to the respective outdoor values and to the typical ratio observed in smelter emissions. On the other hand, it was found that indoor coarse particles comprised close to 20 % of the levels found in the same range of outdoor particles. Moreover, the results from the MOUDI sampling before and after an unexpected strike of the smelter company, confirmed that the main source of airborne metal and metalloids in the area is the smelter. Considering that meteorological conditions as wind speed and wind direction have an important role in the transport and deposition of contaminants to surface accessible to children, this study included a research to identify the multimedia potential risk hazard of the lead and arsenic content in aerosols, dust on playgrounds, harvest rainwater and residential soil. Furthermore, because exposure to Pb is extremely harmful to children (age 6 months-7 years), an assessment of the exposure to this contaminant was performed using the Integrated Exposure Uptake Biokinetic (IEUBK) with site specific data obtained during the study. This model allowed us to evaluate the likelihood of a child in the community under the influence of the smelter emissions to have blood lead levels above the recommended level. The results of this research can reinforce future multimedia Pb and As exposure assessments particularly those focused to evaluate the potential risk to children in schools which at the present is very limited and will be useful for future research and mitigation programs development.