We studied the dust fractions of the smelting slag, mine tailings, and soil from the former Ni-Cu mining and processing district in Selebi-Phikwe (eastern Botswana). Multi-method chemical and mineralogical investigations were combined with oral bioaccessibility testing of the fine dust fractions (<48 and <10 μm) in a simulated gastric fluid to assess the potential risk of the intake of metal(loid)s contaminants. The total concentrations of the major contaminants varied significantly (Cu: 301-9,600 mg/kg, Ni: 850-7,000 mg/kg, Co: 48-791 mg/kg) but were generally higher in the finer dust fractions. The highest bioaccessible concentrations of Co, Cu, and Ni were found in the slag and mine tailing dusts, where these metals were mostly bound in sulfides (pentlandite, pyrrhotite, chalcopyrite). On the contrary, the soil dusts exhibited substantially lower bioaccessible fractions of these metals due to their binding in less soluble spinel-group oxides. The results indicate that slag dusts are assumed to be risk materials, especially when children are considered as a target group. Still, this exposure scenario seems unrealistic due to (a) the fencing of the former mine area and its inaccessibility to the local community and (b) the low proportion of the fine particles in the granulated slag dump and improbability of their transport by wind. The human health risk related to the incidental ingestion of the soil dust, the most accessible to the local population, seems to be quite limited in the Selebi-Phikwe area, even when a higher dust ingestion rate (280 mg/d) is considered.

• Keywords
• Botswana, Ni‐Cu mining and smelting, Selebi‐Phikwe, dust, metal(loid)s, oral bioaccessibility,
• Publication type
• Journal Article MeSH

The laterite Ni ore smelting operations in Niquelândia and Barro Alto (Goiás State, Brazil) have produced large amounts of fine-grained smelting wastes, which have been stockpiled on dumps and in settling ponds. We investigated granulated slag dusts (n = 5) and fly ash samples (n = 4) with a special focus on their leaching behaviour in deionised water and on the in vitro bioaccessibility in a simulated gastric fluid, to assess the potential exposure risk for humans. Bulk chemical analyses indicated that both wastes contained significant amounts of contaminants: up to 2.6 wt% Ni, 7580 mg/kg Cr, and 508 mg/kg Co. In only one fly ash sample, after 24 h of leaching in deionised water, the concentrations of leached Ni exceeded the limit for hazardous waste according to EU legislation, whereas the other dusts were classified as inert wastes. Bioaccessible fractions (BAF) of the major contaminants (Ni, Co, and Cr) were quite low for the slag dusts and accounted for less than 2 % of total concentrations. In contrast, BAF values were significantly higher for fly ash materials, which reached 13 % for Ni and 19 % for Co. Daily intakes via oral exposure, calculated for an adult (70 kg, dust ingestion rate of 50 mg/day), exceeded neither the tolerable daily intake (TDI) nor the background exposure limits for all of the studied contaminants. Only if a higher ingestion rate is assumed (e.g. 100 mg dust per day for workers in the smelter), the TDI limit for Ni recently defined by European Food Safety Authority (196 µg/day) was exceeded (324 µg/day) for one fly ash sample. Our data indicate that there is only a limited risk to human health related to the ingestion of dust materials generated by laterite Ni ore smelting operations if appropriate safety measures are adopted at the waste disposal sites and within the smelter facility.

• Keywords
• Bioaccessibility, Dust, Fly ash, Laterite, Ni smelting, Slag,
• MeSH
• Inorganic Chemicals administration & dosage   MeSH
• Administration, Oral MeSH
• Models, Biological MeSH
• Chromium analysis   MeSH
• Metallurgy * MeSH
• Cobalt analysis   MeSH
• Humans MeSH
• Hazardous Waste analysis   MeSH
• Nickel analysis   MeSH
• Refuse Disposal methods   MeSH
• Coal Ash analysis   MeSH
• Dust analysis   MeSH
• Industrial Waste MeSH
• Environmental Exposure * MeSH
• Gastric Juice MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Brazil MeSH
• Names of Substances
• Inorganic Chemicals MeSH
• Chromium MeSH
• Cobalt MeSH
• Hazardous Waste MeSH
• Nickel MeSH
• Coal Ash MeSH
• Dust MeSH
• Industrial Waste MeSH

Historical mining activities in the village of Kaňk (in the northern part of the Kutná Hora ore district, Czech Republic) produced large amounts of mine wastes which contain significant amounts of metal(loid) contaminants such as As, Cu, Pb, and Zn. Given the proximity of residential communities to these mining residues, we investigated samples of mine waste (n = 5), urban soil (n = 6), and road dust (n = 5) with a special focus on the solid speciation of As, Cu, Pb, and Zn using a combination of methods (XRD, SEM/EDS, oxalate extractions), as well as on in vitro bioaccessibility in simulated gastric and lung fluids to assess the potential exposure risks for humans. Bulk chemical analyses indicated that As is the most important contaminant in the mine wastes (~1.15 wt%), urban soils (~2900 mg/kg) and road dusts (~440 mg/kg). Bioaccessible fractions of As were quite low (4-13%) in both the simulated gastric and lung fluids, while the bioaccessibility of metals ranged between <0.01% (Pb) and 68% (Zn). The bioaccessibilities of the metal(loid)s were dependent on the mineralogy and different adsorption properties of the metal(loid)s. Based on our results, a potential health risk, especially for children, was recognized from the ingestion of mine waste materials and highly contaminated urban soil. Based on the risk assessment, arsenic was found to be the element posing the greatest risk.

• Keywords
• Bioaccessibility, Metal(oid)s, Mine waste, Mineralogy, Street dust, Topsoil,
• MeSH
• Arsenic analysis   MeSH
• Biological Availability MeSH
• X-Ray Diffraction MeSH
• Mining * MeSH
• Soil Pollutants analysis   MeSH
• Copper analysis   MeSH
• Microscopy, Electron, Scanning MeSH
• Lead analysis   MeSH
• Dust analysis   MeSH
• Spectrometry, X-Ray Emission MeSH
• Zinc analysis   MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Czech Republic MeSH
• Names of Substances
• Arsenic MeSH
• Soil Pollutants MeSH
• Copper MeSH
• Lead MeSH
• Dust MeSH
• Zinc MeSH