Assessment of the risks of exposure to mercury used in gold mining :

Abstract

Exposure to environmental toxins is a major contributing factor to the expected increase in chronic diseases within developing countries in the next 20 years. Due to its ubiquitous distribution and persistent nature, mercury (Hg) is an example of a toxic substance that has garnered global concern because of its known detrimental. effects on human and ecosystem health. The estimated daily intake (EDI) and the relative contribution of various sources of Hg to humans differ significantly between individuals, ethnic groups, and across continents. This thesis focuses on small scale gold mining as the major source of mercury exposure in Kitumbi-Kayonza, Mubende district. The project was completed based on the following tasks. Firstly, operation owners and miners were involved in an interview to obtain estimates of Hg used, gold. obtained and Hg that was lost -to the surroundings. Secondly, a total number of sixteen (16) sediment samples (done in duplicates) were taken from tailings pond and processing areas in a mined out area in order to determine its vulnerability to becoming a mining hotspot. The area was then mapped using a GPS receiver in order to determine amount of area that has been mined out. These samples. were taken to Auranda Minerals laboratory for analysis. Thirdly, an exposure assessment model developed by D' Souza (2008) and Health Canada (2004) was used to identify the occupational sources of greatest concern for various age groups in Kitumbi-Kayonza, Mubende district. The. results show that in the course of a dry season, a total of 50,925g of gold is- produced monthly and consequently 139, 800g of Hg is lost to the surrounding. 83.925B of mercury lost per month are released as vapour. This is the quantity from which miners in Kitumbi-Kayonza are likely to be exposed via inhalation, 55,875g of mercury is released to tailings as free mercury and is likely to be methylated by bacteria and other organisms thereby accumulating within the food chain through plants and fish. The- sediment sampling results were very high in mercury concentration and were above the ERL value (0.15ppm). Subsequently, because of this mercury hotspot due to mining were found and delineated. The research area is considered to be contaminated as it relates to mercury contamination and is at a great risk. Highest absorbed -doses due to exposure to mercury were realized when dealing with roasting where mercury is driven off from amalgam by heating.