Oxidative potential (OP) and mineralogy of iron ore particulate matter at the Gol-E-Gohar Mining and Industrial Facility (Iran)

Our plain-English summary of Oxidative potential (OP) and mineralogy of iron ore particulate matter at the Gol-E-Gohar Mining and Industrial Facility (Iran), by N. Soltani, B. Keshavarzi, A. Sorooshian, et al (Environmental Geochemistry and Health, 2018).

The study

• Authors: N. Soltani, B. Keshavarzi, A. Sorooshian, F. Moore, C. Dunster, A.O. Dominguez, F.J. Kelly, P. Dhakal, M.R. Ahmadi, S. Asadi
• Journal: Environmental Geochemistry and Health
• Published: 2018;40(5):1785-1802
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Concentrations of total suspended particulate matter, particulate matter with aerodynamic diameter <2.5 μm (PM2.5), particulate matter <10 μm (PM10), and fallout dust were measured at the Iranian Gol-E-Gohar Mining and Industrial Facility. Samples were characterized in terms of mineralogy, morphology, and oxidative potential. Results show that indoor samples exceeded the 24-h PM2.5 and PM10 mass concentration limits (35 and 150 µg m-3, respectively) set by the US National Ambient Air Quality Standards. Calcite, magnetite, tremolite, pyrite, talc, and clay minerals such as kaolinite, vermiculite, and illite are the major phases of the iron ore PM. Accessory minerals are quartz, dolomite, hematite, actinolite, biotite, albite, nimite, laumontite, diopside, and muscovite. The scanning electron microscope structure of fibrous-elongated minerals revealed individual fibers in the range of 1.5 nm to 71.65 µm in length and 0.2 nm to 3.7 µm in diameter. The presence of minerals related to respiratory diseases, such as talc, crystalline silica, and needle-shaped minerals like amphibole asbestos (tremolite and actinolite), strongly suggests the need for detailed health-based studies in the region. The particulate samples show low to medium oxidative potential per unit of mass, in relation to an urban road side control, being more reactive with ascorbate than with glutathione or urate. However, the PM oxidative potential per volume of air is exceptionally high, confirming that the workers are exposed to a considerable oxidative environment. PM released by iron ore mining and processing activities should be considered a potential health risk to the mine workers and nearby employees, and strategies to combat the issue are suggested.

In plain English

This study measured airborne dust at the Gol-E-Gohar iron ore mining and processing complex in Kerman Province, Iran. Between December 2014 and May 2015 the authors collected 60 air samples in three particle sizes (PM2.5, PM10 and total suspended particulate matter, TSP) at six indoor and four outdoor sites, along with fallout dust and rock samples. Dust levels were highest at the iron ore concentration plant, where TSP reached 399,245 micrograms per cubic metre. Tremolite made up as much as 23.8% of PM10 at the primary crusher, and actinolite as much as 23.5%. Chemical analysis indicated that actinolite was the dominant amphibole asbestos mineral. Talc reached 34.5% of TSP and crystalline silica 7.3% of PM10. In a laboratory test with artificial lung-lining fluid, the dust reacted mainly with ascorbate. Per microgram, it was less reactive than a London roadside sample. The authors concluded that, because dust concentrations were so high, workers are exposed to a considerable oxidative load. The study measured dust, not workers' health.

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 air and dust sampling study with mineral analysis (X-ray diffraction, polarized light microscopy, electron microscopy with chemical analysis) and a laboratory oxidative potential test in a synthetic lung-lining fluid containing no cells or tissue
• Who was studied: 60 airborne particulate samples (20 PM2.5, 20 PM10, 20 TSP) from ten sites (six indoor processing areas, four outdoor areas) at the Gol-E-Gohar complex, 55 km southwest of Sirjan, Kerman Province, Iran, collected December 17 2014 to May 21 2015. The authors also collected 10 fallout dust and 15 drill-core rock samples. No workers were examined.
• Exposure: Iron ore particulate matter from dry mining and processing. Minerals present included the amphibole asbestos minerals tremolite and actinolite, talc and crystalline silica.
• Main results:
  • At the iron ore concentration plant (ICP), mass concentrations were TSP 399,245, PM10 45,288 and PM2.5 10,692 micrograms per cubic metre. These were higher than at all other sites.
  • By volume percentage, tremolite reached up to 23.8% of PM10 at the primary crusher (PC) and 21.2% of TSP at the tail bin (TB).
  • Actinolite accounted for 10.3% of TSP at the ICP site and 23.5% of PM10 at the PC site.
  • Crystalline silica made up as much as 7.3% of PM10 at the PC station. Talc made up as much as 34.5% of TSP at the ICP station.
  • Electron microscope chemical analysis indicated that actinolite was the dominant amphibole asbestos mineral in the dust samples.
  • Needle-shaped minerals in the dust ranged from 1.5 nm to 71.65 micrometres in length and from 0.2 nm to 4.26 micrometres in diameter.
  • The length-to-diameter ratio of all fibrous minerals ranged from 7.5 to 24.
  • In the synthetic lung-lining fluid, the samples reacted mainly with ascorbate, with negligible oxidation of glutathione and urate.
  • Ascorbate oxidation per microgram of dust (indoor and outdoor, respectively) was: PM2.5 1.16 and 1.05; PM10 0.88 and 0.85; TSP 1.18 and 0.76.
  • These per-microgram values were lower than for the London roadside control sample tested in the same experiments (2.2).
  • Ascorbate oxidation per cubic metre of air was higher indoors than outdoors: 26.6 times higher for TSP, 15 times for PM2.5 and 6 times for PM10.
  • The authors reported a significant correlation between indoor TSP mass concentration and ascorbate oxidation per cubic metre (N = 5, rs = 0.6). No relationship was found for outdoor TSP, PM2.5 or PM10.
• The authors' conclusion: The authors concluded that the dust's oxidant activity against ascorbic acid was low to medium per unit of mass compared with urban roadside dust. However, because the mass concentration of iron ore dust at the facility was high, they concluded that workers are exposed to a considerable oxidative load from inhaled particles.
• Limitations the authors state:
  • Mining and processing began only about 20 years ago, so records of worker exposure may be limited, given the long latency period of the inhaled minerals.
  • The boundary between tremolite and actinolite, defined by iron content, is not universally recognized and has changed over time. The two minerals may occur together as a continuous series.
  • The semi-quantitative X-ray diffraction analysis is described as a qualitative method for bulk mineral composition.
  • Only one field blank was taken for the oxidative potential assay.

Topics

Medical terms in this study, explained in our Lexicon: Mineralogy, Tremolite, Talc, vermiculite, Accessory Mineral, Dolomite, Hematite, Actinolite.

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• Respiratory effects of exposure to dust in taconite mining and processing — T.C. Clark, V.A. Harrington, et al. (1980)
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