Pollution level and health risk assessment of road dust from an expressway.
Thirteen road dust and four soil samples were analyzed using instrumental neutron activation analysis (INAA) to determine the elemental composition of road dust collected from Islamabad Expressway. The amounts of most of the elements determined were generally in the lower range of the global data with the exception of Ce, Nd, Sn and Zr, which were measured at higher concentrations in Islamabad. The magnitudes of Enrichment Factors (EFs) showed that the area around Islamabad Expressway is low to moderately polluted especially by elements such as Mg and Sb. Elemental health risk was assessed through dose calculations for carcinogenic and non-carcinogenic metals; and by the determination of LADD (lifetime average daily dose). The carcinogenic metals studied showed the following variation in their LADD values; Cr>Ni>Co>Cd>As. Dose calculations for non-cancerous and cancerous elements showed the data obtained to lie within the safe threshold of 10(-3)-10(-6) mg kg(-1) day(-1) for most elements. The Soil-based elements Al, Fe, K, Mg, Na and Ti were the exception and originated from the exposed soil around the highway. Moreover highest Hazard Index (HI) was found to be associated with the presence of Al, Cr, Pb and V in road dust showing soil, transport and industry to be the major sources of road dust.