Oral bioaccessibility of potentially toxic elements (PTEs) in urban dusts of Abakaliki, Ebonyi State, Nigeria

Abstract

ABSTRACT:A literature survey has shown that no study has investigated the oral bioaccessibility of PTEs in Nigeria dusts. Studies on human health risk of PTEs from urban Nigeria dust have been based only on total elemental concentrations. Whilst this protocol is useful in assessing human health of PTEs, it could lead to an over estimation of the risk considering the elemental sequestration in the dust samples. This study deviated from previous studies by examining the total concentrations as well as the oral bioaccessibility of 8 PTEs in 15 urban dust samples collected from Abakaliki, Ebonyi State, Nigeria. The result showed that high concentrations of Pb (ranging from 236 -1815 mg/kg) were observed in 5 locations. The Unified Bioaccessibility Method (UBM) was used to investigate the oral bioaccessibility of these PTEs in the urban dust samples. The result revealed that all the PTEs were more bioaccessible in the gastric phase that the gastric + intestinal phase. The lead tolerable daily intake (TDI), as well as the bioaccessible TDI, was computed and results compared with a guideline value. © JASEM http://dx.doi.org/10.4314/jasem.v18 i2.13.Introduction: The occurrence and distribution of high concentration of PTEs in urban dusts have been widely reported (Okorie et al., 2012;Xinwei et al., 2009;Al-Khashman, 2007). They sources are also well documented (Wei et al., 2010;Manasreh, 2010). The presence of these PTEs in urban dusts is a potential threat to human health and the ecosystem in general. This is because these elements could enter the human body via the exposure pathways (oral ingestion, inhalation and dermal absorption) (Aelion et al., 2008). In addition, it has been reported that these PTEs have irreversible adverse effects on humans particularly children due to their pica behaviour, physiology, unique exposures and special vulnerabilities (Landrigan et al., 2000). This makes children at a higher risk as their immature organs tend to be more susceptible to PTEs than other contaminants (Egeghy et al., 2011).A literature survey has shown that only a few authors (e.g. Shinggu et al., 2007;Mashi et al., 2005) have investigated the occurrence of PTEs in Nigerian urban dusts, but none for Abakaliki, Ebonyi State. The survey also showed that all the studies determined only the total elemental concentrations. No study has investigated the bioaccessibility of PTEs in Nigerian dust. It is to be noted that in assessing the human health risk of PTEs, it is not the total concentration of PTEs in urban dust that is of greatest concern but the fraction that is released in the human body (bioaccessible fraction) when dust is ingested. Thus, the use of only total elemental concentration in assessing human health risk of PTEs could be seen as an over estimation of the risk associated with oral ingestion of soil based on the principle of PTEs sequestration within various heterogeneous dust samples; a scenario whereby the total elemental content present in the ingested dust is not readily accessible for absorption and trans...