Bioaccessibility of potentially toxic metals in soil, sediments and tailings from a north Africa phosphate-mining area: Insight into human health risk assessment

Faten Khelifi; Antonio G Caporale; Younes Hamed; Paola Adamo

doi:10.1016/j.jenvman.2020.111634

Bioaccessibility of potentially toxic metals in soil, sediments and tailings from a north Africa phosphate-mining area: Insight into human health risk assessment

J Environ Manage. 2021 Feb 1:279:111634. doi: 10.1016/j.jenvman.2020.111634. Epub 2020 Nov 17.

Authors

Faten Khelifi¹, Antonio G Caporale², Younes Hamed³, Paola Adamo⁴

Affiliations

¹ Department of Earth Sciences, Faculty of Sciences of Bizerte, University of Carthage, Jarzouna, 7021, Bizerte, Tunisia; Laboratory for the Application of Materials to the Environment, Water and Energy Faculty of Sciences of Gafsa, University of Gafsa, Campus Sidi Ahmed Zarroug, 2112, Gafsa, Tunisia.
² Department of Agricultural Sciences, University of Naples Federico II, Portici, Italy. Electronic address: ag.caporale@unina.it.
³ Laboratory for the Application of Materials to the Environment, Water and Energy Faculty of Sciences of Gafsa, University of Gafsa, Campus Sidi Ahmed Zarroug, 2112, Gafsa, Tunisia.
⁴ Department of Agricultural Sciences, University of Naples Federico II, Portici, Italy; Interdepartmental Research Centre on the "Earth Critical Zone" for Supporting the Landscape and Agroenvironment Management (CRISP), University of Naples Federico II, Portici, Italy.

PMID: 33213991
DOI: 10.1016/j.jenvman.2020.111634

Abstract

The risk assessment of phosphate mining/processing industrial activities on the environment and human health is crucial to properly manage and minimize the risks over time. In this work, we studied the inhalation and dermal bioaccessibility of potentially toxic metals (PTM) in different particle-size fractions of urban soil, sediments and tailings from Gafsa-Metlaoui phosphate mining area, to assess afterwards the non-carcinogenic (NCR) and carcinogenic (CR) risks for the health of local citizens and workers constantly exposed to airborne particulate matter (PM) originating from these sources of contamination. Samples were separated in particle-size fractions by centrifugation and consecutive cycles of sedimentation and decanting. The pseudo-total concentrations and bioaccessible fractions of PTM were extracted by aqua regia and in vitro bioaccessibility tests, respectively. Both sediments and tailings showed higher-than-background concentrations of PTM (mainly Cd, Zn and Cr), with a tendency to accumulate these metals in fine particles (<10 μm). In urban soil, only Cd was above the background concentration. The bioaccessibility of PTM via inhalation was significantly higher in artificial lysosomal fluid (ALF) than in simulated epithelial lung fluid (SELF): basically, Cd was the most bioaccessible metal (relative bioaccessibility up to 80%), followed by the medium-to-high bioaccessible Zn (47%), Pb (46%) and Cu (39%), and the least bioaccessible Cr (16%). In synthetic skin surface liquid (NIHS 96-10), only Cd was bioaccessible at worrying extent (20-44%). On the basis of US.EPA risk assessment, the exposure to PTM bioaccessible fractions or pseudo-total concentrations would not cause serious NCR and CR risks for human health. Significant health risks (Hazard Index >1 and CR > 10^-4), especially for children, can occur if ingestion route is also considered. The findings underline the need for adequate protection of contaminated soil, sediments and mine tailings laying nearby urban agglomerates, to reduce the health risks for inhabitants and workers of Gafsa-Metlaoui mining area.

Keywords: Airborne particulate matter; Exposure to inorganic contaminants; Gafsa mining basin; Inhalation and dermal bioaccessibility; Non-carcinogenic/carcinogenic health risks; Trace metals.

MeSH terms

Child
Environmental Monitoring
Humans
Metals, Heavy* / analysis
Phosphates
Risk Assessment
Soil
Soil Pollutants* / analysis
Tunisia

Substances

Metals, Heavy
Phosphates
Soil
Soil Pollutants