Environmental Monitoring and Assessment (2006) 118: 51–63DOI: 10.1007/s10661-006-0773-6c Springer 2006NON-CANCER HEALTH RISK ASSESSMENT FROM EXPOSURE TOCYANIDE BY RESIDENT ADULTS FROM THE MINING OPERATIONSOF BOGOSO GOLD LIMITED IN GHANAS. OBIRI, D.K. DODOO∗, F. OKAI-SAM and D.K. ESSUMANGEnvironmental Research Group, Department of Chemistry, University of Cape Coast, Cape Coast(∗author for correspondence, e-mail: [email protected])(Received 11 February 2005; accepted 6 July 2005)Abstract. Cyanide is a very toxic chemical that is used to extract gold from its ores. Wastewaters fromgold mining companies such as Bogoso Gold Limited (BGL) contain cyanide and other potentiallytoxic chemicals that have adverse effects on human beings and aquatic organisms. This study wasconducted to evaluate the human health risk assessment from exposure to free cyanide via oral anddermal contact of surface/underground water by resident adults within the concession of BogosoGold Limited. The chronic non-cancer health risk from exposure to cyanide in River Bogo Upstreamis 230 and 43 (by Central Tendency Exposure (CTE) parameters respectively). This means thatapproximately 230 and 43 resident adults are likely to suffer diseases related to cyanide intoxicationvia oral and dermal contact respectively. For chronic exposure to River Bogo Downstream by residentadults, the non-cancer health risks are: 0.031 and 0.57 via oral and dermal contact for CTE parametersrespectively, which also means that, the non-cancer health risks associated with cyanide intoxicationis negligible as the hazard index is less than 1.0 via oral and dermal contacts respectively. The resultsshowed that health risk for acute exposure to cyanide by the resident adults is very high. Hence theresidents attribute most of the unexplained deaths in the communities to accidental ingestion anddermal contact of cyanide water.Keywords: Bogoso, Dumasi, free cyanide, Prestea, River Ankobra, River Aprepre (popularly knownas River Dumasi), River Bogo1. IntroductionGold mining in Ghana has played a central role in the socio-economic and politicallife of the country for the past 100 years. In Ghana, most of the mining compa-nies have adopted the use of cyanide in extracting gold from its ore. The use ofcyanide has made it possible for the mining companies to make huge profits frommining very low grades of ores. However, cyanidation as an extractive techniquein gold mining in Ghana has become unpopular as a result of cyanide spillages andenvironmental damages the country has witnessed. Ghana has witnessed about 11cyanide spillages between 1989 and 2004. Notably among them are:• In 1989, Obenemase Mines near Konongo spilled large quantities of cyanidesolution, which contaminated a tributary of River Oweri.52 S. OBIRI ET AL.• In 1996, large quantities of cyanide solution was spilled by Teberebe Goldfieldsinto Angonaben stream, a tributary of River Bonsa, causing harm to human livesand aquatic organisms.• Bogoso Gold Limited had a major spillage in 1994. Large volumes of cyanidewere discharged into River Anikoko, which flows into River Bodwire. The com-pany constructed boreholes for some of the affected communities but in placeswhere the boreholes were not operational, the farmers were forced to drink thepolluted river or streams, posing significant health hazard to them. The affectedcommunities, especially the people of Anikoko and Brakwaline were forced toabandon their farms. The communities had to resettle in other communities, asthey could not contain the effects of the spillage.• Again, on October 23rd 2004, there was another spillage by BGL. The spillagewas from the new tailings dam of the company into River Aprepre, whichflows into other rivers including Egya Nsiah, Bemanyah, Manse and Ankobra.This river flows into the big River Ankobra. The cyanide spillage has affectedDumase and other towns including Goloto, Juaben and Egyabroni. Some resi-dents of Dumase and other villages picked and ate dead fishes, crabs, shrimpsand other aquatic organisms that were found floating on the surface of theriver.In all these cases, members of the affected communities drank the cyanide-contaminated water from the rivers and the streams before they were told of thecyanide spillage and hence they showed the symptoms of cyanide intoxication(Amegbey and Adimado, 2003). However, operators of mining companies main-tain that cyanide breaks down quickly into less toxic forms; as such the effects ofcyanide spillage on human beings in the communities are minimal. This claim isalso collaborated by the regulators (i.e., Ghana Environmental Protection Agency,Chamber of Mines and the Mines Department). The breakdown of spilled cyanideis very slow. The breakdown compounds are potentially toxic to fish, aquatic or-ganisms, and human beings and may persist in the environment for long periods oftime (Moran, 1998). They can also be absorbed or bioaccumulate in plant, humanbeings and other aquatic organisms which are found in mining communities wherecyanide spillages had occurred (Moran, 1998; Heming, 1989; Eisler, 1991). Foodcrops such as cassava, cocoyam, just to mention a few which are grown in areasabsorb these toxic chemicals or cyanide and their derivatives (Adzei and Golow,2002; Eisler, 1991).Risk Assessment is the methodological approach in which the toxicity of achemical is identified, characterized and analyzed. It quantifies the perceived riskposed to the defined receptors by a proposed action (Eldon and Bradley, 1992).According to USEPA Risk Assessment Guidance for Superfund (RAGS): Volume I-Human Health Evaluation Manual (HHEM), human health risk assessment consistsof four distinct steps namely:NON-CANCER HEALTH RISK ASSESSMENT FROM EXPOSURE TO CYANIDE 53• Hazard Identification:- identifies the COC (constituent of concern) – free cyanidethat makes significant contribution to exposure and health risk in the study area.• Exposure Assessment:- evaluates the pathways by which resident adults couldbe exposed to free cyanide present in the study areas.• Toxicity Assessment:- identifies which toxicity criteria have to be used in eval-uating the human health risk from exposure to free cyanide in the study area.• Risk Characterization:- this incorporates information from hazard identification,exposure assessment, toxicity assessment and risk estimation to evaluate thepotential risk exposed to the individuals at the study areas.It is against this background