Abstract

The study assessed non-cancer human health risk from exposure to mecury (Hg), cadmium (Cd), arsenic (As), copper (Cu), and lead (Pb) in surface and groundwater in Tinga, in the Bole-Bamboi District. A total of 42 water samples were collected for a period of six months. Mean concentration of Hg, Cd, and Pb were found to be (0.050 ± 0.04 mg/L), (0.031 ± 0.02 mg/L) and (0.07 ± 0.05 mg/L), respectively. These were all above the World Health Organization (WHO) recommended guideline values for drinking water. Non-cancer human health risk as a result of exposure to Hg and Cd through ingestion of borehole water was found to be high. Hazard quotients (HQ) as a result of exposure to mercury for adults and children ranged from 2.5 to 30 through central tendency exposure (CTE) and 4.6 to 60 through reasonable maximum exposure (RME). For Cd, CTE ranged from 0.96 to 2.7 and RME ranged from 1.8 to 5.4. The HQ for exposure to Hg and Cd through ingestion of ground water exceeded the acceptable United States Environmental Protection Agency (USEPA) value of 1.0. This implies that resident children and adults are likely to develop diseases (such as low intelligent quotient, tremor, kidney failure, increased hypertension and cardiovascular diseases) associated with long term exposure to Hg and Cd.

Key words: Small-scale mining, Tinga, non-cancer, health risk, hazard quotient, borehole, surface water.