Pollution indexing and health risk assessments of trace elements in indoor dusts from classrooms, living rooms and offices in Ogun State, Nigeria Olanrewaju Olujimi a,b,⇑ , Oliver Steiner b , Walter Goessler b a Department of Environmental Management and Toxicology, Federal University of Agriculture, P.M.B. 2240, Abeokuta, Ogun State, Nigeria b Institute of Chemistry, Analytical Chemistry, Karl-Franzens University, Graz, Universitaesplatz 1, 8010 Graz, Austria article info Article history: Received 30 January 2014 Received in revised form 11 October 2014 Accepted 15 October 2014 Available online 30 October 2014 Keywords: Trace elements Contamination Health risk Indoor dust Nigeria abstract Heavy metals are known to have a negative impact on human health especially children through oral ingestion. Total metal concentrations were determined in indoor dust from 19 locations consisting of classrooms, living rooms and offices in Ogun State, Nigeria. Digestion and instrumentation reproducibil- ity were validated using certified reference materials (BCR 723 (Road Dust), NIST 2711a (Montana Soil) and NIST SRM 1640e (Trace element in water)). The measured and certified values showed good agree- ment. Potential threat levels using geo-accumulation (I geo ) and human health risk for both children and adult were assessed. The mean I geo levels for the classified and probable carcinogens is in the order Cd (4.84) > Cr (3.28) > Pb (2.61) > Ni (2.48) > As (1.64) while other elements are in the order Zn (5.41) > Ba (4.86) > Sr (4.38) > Zn (4.27) > V (3.24) > Cu (3.14) > Hg (2.61)  TI (2.61). For human health risk, inges- tion was the main route of exposure followed by dermal uptake and inhalation. Hazard index values for all studied metals were lower than the safe level of 1 while Hg vapor exhibited the highest risk value (0.13) in the case of children. The carcinogenic risk for As, Cd, Co, Cr, Ni and Pb were all within the accept- able level (10 4 –10 6 ), but there was potential carcinogenic risk posed by Cr for both adults and children. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Globally, heavy metals pollution have drawn much attention from the academia, government agencies and pressure groups due to their potential health effects on human living both in rural and urban areas. Metals such as lead, cadmium, mercury, zinc and chromium are known for their persistent behavior in the environ- ment with consequent environmental, human and animal damage (Zheng et al., 2013; Zhu et al., 2013). Some of these metals are known human mutagens and carcinogen and are associated with various human ailments like cardiovascular, nervous system, blood and bone diseases, kidney failure, gingivitis, tremors among others (Rashed, 2008; Sun et al., 2013; Zheng et al., 2013). Human beings may be exposed to heavy metals through oral ingestion, inhalation and or dermal contacts (Zheng et al., 2010a,b; Zheng et al., 2013; Li et al., 2014). One of the common routes of these metals to children and adults is through indoor dust contact. Indoor environment may be contaminated with metal laden dust in several ways. These might be infiltration from outdoor sources majorly from vehicle emission, transfer of parti- cles by wind, legs or shoes and internally from smoking, incense burning, building and furniture materials, consumer products and occupants’ activities (Mielke et al., 2001; Rashed, 2008; Darus et al., 2012). Studies have shown that time spent indoors varies with occupation, age, gender and status. According to Schweizer et al. (2007), people living in urban cities almost spent 90% of their time exposed to the indoor atmosphere. Exposure of children to indoor dust is particularly of interest due to their ten- dency to play on the floor and their habit to put everything in their mouth (Zheng et al., 2010a,b; Luo et al., 2012; Saeedi et al., 2012). Unlike the developed countries, developing nations lacks ade- quate learning environment for children and subsequently, pupils and their teachers are often exposed to various contaminants within the educational facilities. Also, due to lack or poor imple- mentation of environmental sanitation policies, living and working environments are not as hygienic as in the developed countries. Due to the un-hygienic living conditions in many developing countries, children and adults are often exposed to different envi- ronmental pollutants and subsequently leading to illnesses and http://dx.doi.org/10.1016/j.jafrearsci.2014.10.007 1464-343X/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Department of Environmental Management and Toxicology, Federal University of Agriculture, P.M.B. 2240, Abeokuta, Ogun State, Nigeria. E-mail addresses: olujimio@funaab.edu.ng, olujimi@uni-graz.at (O. Olujimi). Journal of African Earth Sciences 101 (2015) 396–404 Contents lists available at ScienceDirect Journal of African Earth Sciences journal homepage: www.elsevier.com/locate/jafrearsci