Evaluation of geochemical composition and heavy metals related occupational health risks of Ambo sandstone quarry sites, West Shewa of Ethiopia

Abstract

• Geochemical evaluation of Ambo sandstone from West Shewa, Ethiopia was conducted. • Level of trace metals & associated health risks from occupational exposure were assessed. • Level of Cr exceed the Earth’s crust average and FAO/WHO permissible level in soil. • Target hazard quotient (HQ) and hazard index (HI) of heavy metals were below unity. • Total cancer risk from mixtures of Ni, Cr, Cd & Pb exceeded safe limit for cancer. Prolonged exposure to sandstone dust from quarry sites has been associated with adverse health hazards. This study was aimed to evaluate the geochemistry (major oxides and trace heavy metal(loid)s) of Ambo sandstone, and human health risks of heavy metals due to exposure to the sandstone dust from main quarry sites of West Shewa, Ethiopia. Lithium metaborate fusion-FAAS and wet acid digestion-ICP-OES were used for major oxides and heavy metal(loid)s determination, respectively. The mean concentration of major oxides in the sandstones was in decreasing order of: SiO 2 > Al 2 O 3 > Na 2 O > Fe 2 O 3 > K 2 O > CaO > MgO > MnO. Geochemical results of Ambo sandstones indicated that they are mineralogically immature and classified into Greywacke. The mean levels of heavy metal(loid)s in Ambo sandstone were ranged 10.37‒28.20, 9.37‒19.07, 1.71‒8.15, 12.20‒15.28, 5.89‒15.38 and 100.35‒138.92 in mg/kg for Pb, Zn, Cd, Cu, Ni and Cr, respectively. Hazard quotient and hazard index were < 1, signifying no non-carcinogenic health risks due to exposure to Ambo sandstone dusts. The cancer risk values for the individual metal(loid)s (Cd, Ni, Cr, Pb and As) is within the tolerable range or insignificant (ILCR ≤ 1.0 × 10 –4 ). However, total cancer risks resulting from exposure to multiple elements exceeded the acceptable threshold value of cancer risk (2.1 × 10 –4 (Senkelle) and 1.05 × 10 –4 (Aleltu)), demonstrating possible carcinogenic risk to the exposed workforces. Carcinogenic risk result revealed that Cr contributed the most significant risk with ingestion route as the primary exposure pathway. The finding signifies the requirement of strict regulatory control by all stakeholders to mitigate the carcinogenic health risks. It also highlights the need for awareness creation of the potential dangers due to prolonged exposure to the sandstone dust. Continuous surveillance and research on metal(loid)s accumulation in sandstone dust, agricultural soil and vegetables near quarry sites are vital to safeguard public health.