Spatio-seasonal variation of airborne asbestos concentration in urban areas of Shiraz, Iran

Our plain-English summary of Spatio-seasonal variation of airborne asbestos concentration in urban areas of Shiraz, Iran, by M.K. Fathi Fathabadi, A. Abdolahnejad, H. Teiri, et al (International Journal of Occupational and Environmental Health, 2017).

The study

• Authors: M.K. Fathi Fathabadi, A. Abdolahnejad, H. Teiri, Y. Hajizadeh
• Journal: International Journal of Occupational and Environmental Health
• Published: 2017;23(2):143-150
• Cited by: 10 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background Asbestos fiber is mainly released from friction product in brakes and clutch linings and from reinforcing agent in the asbestos-cement industry. It leads to serious health problem such as mesothelioma and lung cancer. The objectives of this study were to monitor the levels of asbestos fibers in ambient air of Shiraz, Iran during 2014, and to draw its GIS distribution map for the city. Methods Samples were collected by mixed cellulose ester filters mounted on an open-faced filter holder using a SKC sampling pump. Fiber counting was conducted using both phase contrast microscopy (PCM) method to determine total fibers, and scanning electron microscopy (SEM) method to identify non-asbestos from asbestos fibers. Results The average concentrations of asbestos fibers in ambient air of the city were 1.11 ± 0.25 PCM f/l and 12.21 ± 2.52 SEM f/l. The highest concentration of asbestos fibers was measured in Valiasr square amounting 1.96 ± 0.34 PCM f/l and 16.87 ± 2.14 SEM f/l. Conclusions The average of asbestos fibers in all sampling points was higher than the WHO guideline (0.05 PCM f/l, 2.2 SEM f/l). This may be attributed to the frequently occurrence of heavy traffic, the existence of relevant industries in and around the city, and the topographic characteristics of the city. Thus, product substitution, traffic smoothing and industrial sites relocating are suggested to eliminate the asbestos fibers emission.

In plain English

This study measured asbestos fibers in outdoor air at eight sampling points in Shiraz, Iran, from January to December 2014. The sites were chosen with regard to traffic, population density, industrial sources and wind direction. Air was drawn through filters. Fibers were counted by light microscopy (PCM) and by scanning electron microscopy (SEM), with chemical analysis used to separate asbestos from non-asbestos fibers. About 25% of the fibers seen by SEM were non-asbestos and were excluded. The average across all sites was 1.11 fibers per liter by PCM and 12.21 by SEM. Valiasr square had the highest levels (1.96 PCM and 16.87 SEM fibers per liter), and Moallem square the lowest (0.69 and 8.05). Winter levels were highest, but the differences between seasons were not statistically significant. No notable relationship with weather was found. Levels were significantly above the WHO guideline of 2.2 SEM fibers per liter. One example fiber was identified as crocidolite. The study measured air levels, not illness. The authors concluded that exposure in Shiraz is much higher than WHO standards. They attributed this to heavy traffic, asbestos-using industries and the city's geography.

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 monitoring study (outdoor air sampling with fiber counting by PCM and SEM; no health outcomes measured)
• Who was studied: outdoor (ambient) air at 8 sampling points covering four regions of Shiraz, Iran, sampled repeatedly from January to December 2014
• Exposure: airborne asbestos fibers in urban outdoor air; fibers longer than 5 μm, thinner than 3 μm, with a length-to-width ratio of 3:1 were counted; SEM with EDX was used to tell asbestos from non-asbestos fibers and identify fiber types
• Main results:
  • Average across all sampling points: 1.11 (SD 0.25) fibers per liter by PCM and 12.21 (SD 2.52) fibers per liter by SEM
  • Highest concentration at Valiasr square: 1.96 plus or minus 0.34 PCM fibers per liter and 16.87 plus or minus 2.14 SEM fibers per liter (Table 1 gives the SEM SD as 4.25)
  • Lowest station average in Table 1 was Moallem square (8 samples): 0.69 PCM fibers per liter and 8.05 SEM fibers per liter
  • Winter had the highest seasonal average (1.14 plus or minus 0.43 PCM fibers per liter, 13.41 plus or minus 3.8 SEM fibers per liter), but there was no statistically significant difference between seasons (p greater than 0.161)
  • Concentrations in the studied seasons differed significantly from the WHO recommended standard of 2.2 SEM fibers per liter (p less than 0.0001), being higher at most stations
  • No notable correlation was found between asbestos fiber concentration and weather measures (p greater than 0.05, r less than 0.2)
  • About 25% of fibers seen by SEM were non-asbestos and were removed from the counts
  • An example SEM image and EDX spectrum of an airborne fiber was identified as crocidolite; the article does not report counts by fiber type
• The authors' conclusion: The authors concluded that exposure to airborne asbestos fibers in Shiraz is much higher than WHO recommended standards. They attributed the high levels to heavy traffic, asbestos-using industries in and around the city, and the city's geography, and stated that exposure probably has negative health effects on residents.
• Limitations the authors state:
  • The PCM method cannot distinguish asbestos fibers from non-asbestos fibers
  • PCM cannot detect fibers thinner than 0.25 μm
  • SEM fiber counting accuracy is poor because only a small area can be scanned at high magnification

Topics

The National Library of Medicine indexes this study under subjects our site covers: Construction.

Medical terms in this study, explained in our Lexicon: Asbestos-Cement, Mesothelioma, Lung Cancer, Mixed Cellulose Ester Filter, Fiber Counting, phase contrast microscopy (PCM), Scanning Electron Microscopy (SEM).

Related studies

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• Monitoring of airborne asbestos fibers in an urban ambient air of Shahryar City, Iran: levels, spatial distribution, seasonal variations, and health risk assessment — F. Taghizadeh, A.J. Jafari, et al. (2019)
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• Assessment of airborne asbestos exposure at an asbestos cement sheet and pipe factory in Iran — H. Marioryad, H. Kakooei, et al. (2011)
• Protocol for identification of airborne asbestos fibres in the urban areas and spatio-temporal trend — Y. Hajizadeh, N. Jafari, et al. (2019)
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