Non-Cancer Human Health Risk Assessment of Heavy Metals in Black Carbon Monitored in Port Harcourt, Rivers State, Nigeria
Resumen
Due to the continuous presence of black carbon (soot) in the lower atmosphere of Port Harcourt and its environs; heavy metals, contained in the soot, are released into the environment with potential for absorption into systemic circulation through inhalation, ingestion and dermal contact. About forty samples were assessed and collected, in the dry and wet seasons, from different selected locations in the metropolis and their heavy metals concentration determined using atomic absorption spectrophotometer (AAS). Non-cancer health risk was assessed, using United State Environmental Protection Agency (USEPA) guidelines, to evaluate the hazard quotient (HQ) and the hazard index (HI) following exposure. The results showed that the mean concentration of Cd, Cr, Co, Pb and Ni in dry season are 0.39 mg/kg, 6.60 mg/kg, 1.61 mg/kg, 4.38 mg/kg and 1.03 mg/kg respectively and the mean concentrations of Cd, Co, Pb and Ni in wet season are 0.14 mg/kg, 0.11 mg/kg, 0.27 mg/kg and 0.19 mg/kg respectively. Concentration of Cr was below detectable level in the rainy season. The HQ and HI of these heavy metals were calculated for ingestion, dermal contact and inhalation exposure pathways and values obtained for dry season were higher than those obtained for wet season. All values of HQ and HI obtained in both dry and wet seasons for adults were lower than the USEPA guideline value of 1, showing that there is relatively low non-cancer health risk posed by the identified heavy metals in the soot. However, in the dry season only, dermal HQ for Co was 1.77 and HI value for all the five metals was 2.19, thus making the children resident vulnerable to lung and heart diseases as well as disease conditions such as allergic reactions, effect on developing fetus due to intake of cobalt. The HI values for children in both seasons were higher than that of adult in the study area. While HI of children is approximately 3 times that of adult in dry season, it is approximately double that of adults in the wet season. This implies that children are more susceptible and at greater non-cancer health risk of exposure to soot derived heavy metals than adults in Port Harcourt. There is need for effective measure to reduce the release of cobalt and other four metals due to their high HI of 2.19 in the environment to avert the potential noncancer health risk of not only Co but all the five metals. This risk assessment study can be used in health based risk communication to address the impact of heavy metals in soot continuously present in the lower atmosphere of Port Harcourt and its environs.
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Referencias
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