Exposure to Heavy Metals in Soot Samples and Cancer Risk Assessment in Port Harcourt, Nigeria

Background. Port Harcourt is an oil-rich city in Nigeria's Niger delta region. For over two years, Port Harcourt experienced black soot deposition in the environment. In November 2016, residents woke up to black soot covering cars, clothes, houses, plants, etc. Soot concentrations continued to increase until the first quarter of 2017. After public outcry, the frequency and concentration of soot deposition began to decline. Objective. The present study was carried out to determine the presence and levels of heavy metals in soot along with a cancer risk assessment of heavy metals exposure in Port Harcourt, Nigeria. Method. Three residential locations were sampled: Aba road, Woji and Iwofe. Sampling was performed from 6:00 am to 6:00 pm, to simulate the estimated duration that most residents who do not work in offices are exposed to soot in places such as the open market and business areas. Five heavy metals (iron (Fe), nickel (Ni), chromium (Cr), cadmium (Cd) and lead (Pb)) were investigated. The data obtained were subjected to Pearson correlation and one-way analysis of variance using SPSS software to test the correlation and significant differences between metals concentrations. Results. Lead was found to have a significant correlation with Cd (0.808), indicating that both metals originated from the same source. Concentrations of heavy metals were higher than control values and the World Health Organization's specifications for ambient air. Chromium concentrations were the lowest. The order of concentration of heavy metals was Fe > Pb > Cd > Ni > Cr. Conclusions. Non-carcinogenic and carcinogenic health risks of these heavy metals were evaluated using the target hazard quotient (THQ) and the incremental lifetime cancer risk (ILCR). Obtained ILCR values were within the acceptable limits for cancer risks. However, the total ILCR values for Cd and Pb for children were 3 times higher than those for adults. This is a source of concern as their prevalence in ambient air puts children and residents in Port Harcourt metropolis at risk of various types of cancers. Competing Interests. The authors declare no competing financial interests.