Determination and Risk Assessment of Heavy Metals Concentrations collected from Indoor houses at Lagos State of Nigeria

Abstract

The aim of this study is to determine the levels of selected heavy metals (As, Pb, Zn, Cu and Cr) at 60 homes from the 20 local governments in Lagos State, Nigeria. Approval was sought from respective residential landlords and occupants of the sampled
communities. Three dust samples were collected from each local government. A total of 60 dust samples were collected and
labelled according to the first three letters of each Local government. Indoor dust samples from households (furniture, container
bags, window slides, ceiling fan and standing fan) were collected using soft paint brushes. 0.5g of the homogenized mixture was
measured in triplicate labelled 1, 2 and 3 in different boiling tubes for digestion process. Each triplicate samples were digested
using aqua regia for 1 hour at a temperature of about 100 degree celcius. Heavy metal concentrations were determined using
Agilent Technologies 4210 MP-AES Atomic Absorption Spectrometer (AAS). The concentration of heavy metals in the indoor dust
were dominated by Arsenic with an average concentration of 57.76-111.93 mg/kg followed Lead 13.81-116.60 mg/kg, Zinc 22.73-
224.2 mg/kg, Copper 8.27-228.75 mg/kg and Chromium with concentration of 2.53-22.60 mg/kg respectively. The concentrations
of heavy metal in the areas investigated followed the order: Ar>Pb>Zn>Cu>Cr. The exposure dose was also estimated through
ingestion, inhalation and dermal contacts, and the exposure route was highest for ingestion pathway. The health risk (carcinogenic and non-carcinogenic) of these heavy metals were assessed based on the United States Environmental Protection
Agency health risk models. The estimated values were compared to standard guidelines and human health limits by the United
States Environmental Protection Agency, USEPA and California Environmental Protection Agency, Ca/EPA. For noncarcinogenic risk, the hazard index values for all the studied metals were lower than the safe level of 1. The Total Lifetime Cancer Risk for adults and children were below the limit (1x10-6– 1x10-4) as standardized by USEPA except in children which was slightly higher than the permissible limit in two local government areas; (Shomolu L.G.A 1.03x10-4) and (Lagos Mainland 1.02x10-4). This indicates that the risk of carcinogenic effect occurring is likely in children with exposure to arsenic