Bioaccessibility of potentially harmful elements (PHEs) from environmental matrices and implications for human health

Boisa, Ndokiari (2013) Bioaccessibility of potentially harmful elements (PHEs) from environmental matrices and implications for human health. Doctoral thesis, Northumbria University.

Preview

PDF (PhD thesis) boisa.ndokiari_phd.pdf - Accepted Version Download (6MB) | Preview

Abstract

Internationally publicized impacts upon human health associated with exposure to potentially harmful elements (PHE) have been reported globally. Particular concern has surrounded the exposure to Pb indicated by the presence of highly elevated concentrations of Pb in blood and hair samples amongst internally displaced populations (IDPs) in Mitrovica, Kosovo, following the Kosovan War (Runow, 2005). The exposure risk to humans depends in part on the potential of the PHE to mobilise from its matrices in the human digestive and respiratory systems (bioaccessibility) and enter the blood stream (bioavailability). This study utilizes physiologically based in-vitro extraction methods to assess the bioaccessibility of PHEs in surface soils and metallurgical waste in Mitrovica and assesses the potential daily ingestion of soil-bound PHEs (As, Cd, Cu, Mn, Pb, and Zn) and inhalation (Pb) of particulate matter < 10 μm (PM10).

A total of 63 samples (52 surface soils and 11 mine/smelter waste) were selected based on PHE loadings and their spatial distribution. For the in-vitro oral bioaccessibility 0.3 g subsamples were analysed using the UBM method (adopted by BARGE, Wragg et al., 2009). The mean bioaccessibility of Cd, Pb and Zn in the gastric phase is 51 %, 57 % and 41 %, respectively, compared to 18 %, 16% and 14%, respectively, in the gastric-intestinal phase. The trend with As and Cu data is less consistent across the sample locations, with a mean of 20 % and 22 % in the gastric phase and 22 % and 26 % bioaccessibility in the gastric-intestinal phase, respectively. To investigate the role of mineralogy in understanding the bioaccessibility data subsamples (< 250 μm) were submitted to the British Geological Survey, Nottingham, for X-ray diffraction (XRD) analyses. Samples associated with lower bioaccessibilities typically contain a number of XRD-identifiable primary and secondary mineral phases, particularly As- and Pb-bearing arseninian pyrite, beudantite, galena and cerrusite. For the inhalation bioaccessibility, PM10 subsamples were extracted from 33 samples using a locally developed laboratory based wet method. The 0.3 g PM10 subsamples were analysed using a new tracheobronchial fluid and protocol developed as part of this study. The bioaccessibility of Pb for all the 33 samples tested ranged from 0.02 to 11 % and it is consistent with a range (0.17 to 11 %) previously reported by Harris and Silberman (1988) for Pb bioaccessibility in inhalable particulates (< 22 μm) using canine serum.

Quantification of the potential human exposure risk associated with the inhalation and ingestion of soil-associated PHEs indicates the likely possibility of local populations exceeding the recommended tolerable daily intake of Pb. IEUBK model (USEPA, 2007) predicted mean blood Pb concentrations for children based on bioaccessible (ingestion) data are above the CDC level of concern (10 μg/dL).

Actions (login required)

View Item

Downloads