Toxicological risk evaluation of polycyclic aromatic hydrocarbons in boreholes located within unsanitary dumpsite in Nnewi, Anambra State, Nigeria

Abstract

ABSTRACT Polycyclic aromatic hydrocarbons (PAHs) from unlined dumpsites have contributed significantly to the pollution of the environment. This study investigates the pollution level of unlined dumpsite by determining the PAH levels of boreholes around the dumpsite. 16 upstream samples and 16 downstream samples (control) were obtained during the wet and dry seasons. The levels of PAH were evaluated using Gas Chromatography interfaced with a flame ionisation detector. Carcinogenic (TEQ) and mutagenic (MEQ) equivalents of PAHs in the borehole samples were evaluated. Carcinogenic and non-carcinogenic related risks were evaluated via dermal and ingestion pathways. Possible sources of PAHs in the borehole were evaluated. The PAH levels in the upstream and downstream locations ranged from ND – 113.13 µg/L and ND – 1.25 µg/L respectively. Total PAHs concentrations in the upstream and downstream ranged from 12.36–135.68 µg/L and 3.63–5.57 µg/L respectively. The upstream samples PAHs concentrations were greater than the downstream samples PAHs values in the wet and dry seasons. The PAH values in the rainy season were greater than the dry season values, which was associated with leachate infiltration from the dumpsite. Dibenz(a,h)anthracene was established to be of greater carcinogenic and mutagenic threats in the borehole samples from the study areas. The non-carcinogenic risk seems unlikely through dermal absorption, while they are a possibility of carcinogenic risk through dermal absorption for both child and adult age categories. The hazard index value of 3.219 recorded for the child age category at the upstream location, was the only possible chance of non-carcinogenic risk through ingestion. Carcinogenic risks through ingestion were unlikely but can accumulate to toxic levels if not checked. Diagnostic ratio’s values inferred that PAH’s origins arepredominantly from pyrolytic and petrogenic sources for upstream sites and petrogenic sources for downstream sites.