Risk assessment and source analysis of heavy metals in soil around an asbestos mine in an arid plateau region, China

Our plain-English summary of Risk assessment and source analysis of heavy metals in soil around an asbestos mine in an arid plateau region, China, by X. Li, D. Ding, W. Xie, et al (Scientific Reports, 2024).

The study

• Authors: X. Li, D. Ding, W. Xie, Y. Zhang, L. Kong, M. Li, M. Li, S. Deng
• Journal: Scientific Reports
• Published: 2024;14(1):7552
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Asbestos is widely used in construction, manufacturing, and other common industrial fields. Human activities such as mining, processing, and transportation can release heavy metals from asbestos into the surrounding soil environment, posing a health hazard to the mining area's environment and its surrounding residents. The purpose of the present study was to determine the extent of ecological and human health damage caused by asbestos pollution, as well as the primary contributors to the contamination, by examining a large asbestos mine and the surrounding soil in China. The level of heavy metal pollution in soil and sources were analyzed using methods such as the geo-accumulation index (Igeo), potential ecological risk index (RI), and positive matrix factorization (PMF) model. A Monte Carlo simulation-based health risk model was employed to assess the health risks of heavy metals in the study area's soil to human beings. The results showed that the concentrations of As, Pb, Cr, Cu, and Ni in the soil were 1.74, 0.13, 13.31, 0.33, and 33.37 times higher than the local soil background values, respectively. The Igeo assessment indicated significant accumulation effects for Ni, Cr, and As. The RI evaluation revealed extremely high comprehensive ecological risks (RI ≥ 444) in the vicinity of the waste residue heap and beneficiation area, with Ni exhibiting strong individual potential ecological risk (Eir ≥ 320). The soil health risk assessment demonstrated that As and Cr posed carcinogenic risks to adults, with mean carcinogenic indices (CR) of 1.56E - 05 and 4.14E - 06, respectively. As, Cr, and Cd posed carcinogenic risks to children, with mean CRs of 1.08E - 04, 1.61E - 05, and 2.68E - 06, respectively. Cr also posed certain non-carcinogenic risks to both adults and children. The PMF model identified asbestos contamination as the primary source of heavy metals in the soil surrounding the asbestos mining area, contributing to 79.0%. According to this study, it is recommended that management exercise oversight and regulation over the concentrations of Ni, Cr, Cd, and As in the soil adjacent to asbestos mines, establish a designated control zone to restrict population activities, and locate residential zones at a safe distance from the asbestos mine production zone.

© 2024. The Author(s).

In plain English

This study measured eight heavy metals in soil at and around a large chrysotile asbestos mine in an arid plateau region of China. It did not measure asbestos fibers. The authors sampled surface soil at 84 points in mining, beneficiation, waste-pile, residential and bare-land areas, plus 12 asbestos ore, tailings, product and dust samples. Average soil nickel and chromium were 33.37 and 13.31 times higher than local background values. The overall ecological risk index averaged 269.40 (high); 29.76% of sampling points were rated extremely high. A model of exposure by swallowing, skin contact and breathing gave mean arsenic cancer risk indices of 1.56E-05 for adults and 1.08E-04 for children. The authors judged that arsenic and chromium posed carcinogenic risks to adults, and arsenic, chromium and cadmium to children. They also judged that chromium posed certain non-cancer risks to both. A source model attributed 79.0% of soil heavy metals to asbestos pollution, 11.1% to coal combustion and 9.9% to natural sources. The authors recommended monitoring and controlling nickel, chromium, cadmium and arsenic in soils near such mines and restricting activity there.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Environmental soil survey with pollution indices, ecological risk index, probabilistic (Monte Carlo) human health risk modeling and source apportionment (positive matrix factorization, PMF)
• Who was studied: 84 surface soil samples (0 to 30 cm) from 84 sampling points in the mining area, beneficiation area, area around waste residue piles, residential area and bare land of a large asbestos mine in an arid plateau region of China. Local background values were from non-agricultural land in Ruoqiang County, Xinjiang. A further 12 pollution-source samples were taken (asbestos ore, tailings, products and dust, three of each). Adults and children were modeled as hypothetical receptors. Sampling dates were not given.
• Exposure: Heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, Zn) in soil around a 62-year-old open-pit chrysotile (clinochrysotile) asbestos mine. Health risk was modeled for oral ingestion, dermal contact and inhalation of soil. Asbestos fibers themselves were not measured.
• Main results:
  • In study-area soil, average concentrations of As, Pb, Cr, Cu and Ni were 1.74, 0.13, 13.31, 0.33 and 33.37 times higher than local background values, respectively.
  • Mean geo-accumulation index values were above 0 only for Ni (3.58), Cr (2.46) and As (0.04); 3.57% of sample points were severely enriched with As.
  • Nickel had the highest mean individual ecological risk (171.87), and 48.81% of sampling points were rated high risk or above for Ni.
  • The comprehensive ecological risk index across sampling points averaged 269.40 (high), with a range of 41.82 to 755.01.
  • 29.76% of sampling points had extremely high comprehensive ecological risk (RI of 444 or more).
  • Modeled mean carcinogenic risk indices for adults were As 1.56E-05 and Cr 4.14E-06.
  • Modeled mean carcinogenic risk indices for children were As 1.08E-04, Cr 1.61E-05 and Cd 2.68E-06.
  • Mean total carcinogenic risk (TCR) was 2.00E-5 for adults and 1.27E-4 for children.
  • Mean and 95th percentile non-carcinogenic hazard quotients for chromium were greater than 1 for both adults and children.
  • Mean hazard index (HI) was 7.94E-01 for adults and 1.85 for children.
  • The PMF model attributed soil heavy metals to asbestos pollution sources (79.0%), coal combustion sources (11.1%) and natural sources (9.9%).
• The authors' conclusion: The authors concluded that their results apply to risk prediction for heavy metals in soils around asbestos mines of the same type in China. They recommended monitoring Ni, Cr and As in agricultural soils near such mines. They also recommended that authorities monitor and control Ni, Cr, Cd and As near the mines and delineate areas where people's activities are restricted.

Topics

Medical terms in this study, explained in our Lexicon: Carcinogenic.

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