Monitoring of airborne asbestos fibers in an urban ambient air of Shahryar City, Iran: levels, spatial distribution, seasonal variations, and health risk assessment

Our plain-English summary of Monitoring of airborne asbestos fibers in an urban ambient air of Shahryar City, Iran: levels, spatial distribution, seasonal variations, and health risk assessment, by F. Taghizadeh, A.J. Jafari, M. Gholami, et al (Environmental Science and Pollution Research International, 2019).

The study

• Authors: F. Taghizadeh, A.J. Jafari, M. Gholami, M. Kermani, H. Arfaeinia, S. Mohammadi, M. Dowlati, A. Shahsavani
• Journal: Environmental Science and Pollution Research International
• Published: 2019;26(7):6450-6459
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Asbestos, as with other pollutants in the air, has adverse effects on the health of human beings and animals. Today, the relationship between presence of asbestos fibers in the air breathed by humans and developing serious diseases such as lung cancer (asbestosis) and mesothelioma has been proven. This study was designed and conducted within the time period of August 2017 and June 2018 to determine the concentration of asbestos fiber in the ambient air of Shahryar City and to evaluate their health effects for the general population of the city. For this purpose, samples were taken from four points, and overall 32 air samples were taken along the year. The samples were then analyzed by the phase contrast microscopy (PCM) method. Also, to investigate the type of asbestos and for more accurate counting of fibers, SEM analysis was utilized. Finally, based on the EPA IRIS method, the health effects resulting from asbestos risks were also evaluated. The results of this study indicated that the mean annual concentration of asbestos fiber in the ambient air of Shahryar City was obtained as 0.0019 f/ml PCM and 0.0072 f/ml SEM. Furthermore, the most polluted point was S1 point (0.0119 -0.0026 f/ml, PCM), while the lowest concentration was related to S4 point (0.001 f/ml PCM-0.0021 f/ml SEM). The mean annual risk resulting from airborne asbestos fiber in the ambient air of Shahryar City for all samples was obtained as 1.72 × 10-6 to 2.2 × 10-4, which was higher than the recommended risk range in some points.

In plain English

The authors measured airborne asbestos fibers outdoors in Shahryar City, Iran, from August 2017 to June 2018. They took 32 air samples across four seasons at four sites: near a fiber and spinning factory (S1), near mining (S2), at the busiest traffic point (S3) and in a residential area (S4). Fibers were counted by light microscopy (PCM); electron microscopy (SEM) identified crocidolite, tremolite and fibers the article calls chrysolite. The yearly average was 0.0019 f/ml by PCM and 0.0072 f/ml by SEM (abstract and site averages; the results text prints 0.0018 and 0.0089). The authors called this far above a guideline of 0.0022 f/ml (SEM). S1 had the highest levels and S4 the lowest. Levels peaked in fall and were lowest in spring, with no statistically significant link to temperature or humidity. Estimated excess lifetime cancer risk for residents ranged from 1.72 × 10^-6 to 2.2 × 10^-4; the highest estimates, at S1 and S3, exceeded the US EPA target range of 1 × 10^-6 to 1 × 10^-4. The authors said their risk method was simple and tends to overestimate.

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 with a modelled (calculated) cancer risk assessment; no people were examined
• Who was studied: Outdoor (ambient) air at four sampling stations in Shahryar City, Tehran Province, Iran, sampled from August 2017 to June 2018 over four seasons; 32 samples in total. The risk estimates apply to the city's general population (residents).
• Exposure: Airborne asbestos fibers in outdoor air. Sampling stations were near mining operations, an industrial town, high-traffic points and residential areas. Fiber types identified by SEM-EDX were crocidolite, tremolite and 'chrysolite' (the article's spelling; it calls this white asbestos).
• Main results:
  • The abstract gives the mean annual asbestos fiber concentration in Shahryar outdoor air as 0.0019 f/ml by PCM and 0.0072 f/ml by SEM. These figures match the average of the four station means in Table 1. The results section instead prints 0.0018 f/ml (PCM) and 0.0089 f/ml (SEM).
  • The authors said the mean annual concentration was far higher than the SEM-based guideline value of 0.0022 f/ml.
  • Station S1 (near a fiber and spinning factory) had the highest concentration (0.0026 f/ml PCM, 0.0119 f/ml SEM), followed by S3 (the highest-traffic point; 0.0023 f/ml PCM).
  • Station S4 had the lowest concentration: 0.001 f/ml by PCM and 0.0021 f/ml by SEM.
  • At S1 the fibers observed were mostly chrysolite. Crocidolite and tremolite fibers were mostly observed at residential and high-traffic sites such as S4 and S3.
  • No statistically significant relationship was found between asbestos concentration and temperature or humidity.
  • The highest seasonal mean concentration was in fall and the lowest in spring. The authors attributed this to temperature inversions and to precipitation.
  • Estimated excess lifetime cancer risk (ELCR) for residents across all samples ranged from 1.72 × 10^-6 to 2.2 × 10^-4. The highest estimates were at S1 (2.2 × 10^-4) and S3 (1.83 × 10^-4). The authors compared these with the US EPA target range of 1 × 10^-6 to 1 × 10^-4.
  • The estimated risk at S4 was the lowest, and the authors described it as almost within the allowable range.
  • Of the age groups modelled (0–2, 2–6, 6–16 and 16–30 years), the highest exposure concentrations and risk estimates at all stations were for the 16–30 years group.
• The authors' conclusion: The authors concluded that Shahryar City is very polluted with asbestos fibers, with levels higher than values recommended for lifetime exposure. They attributed the high levels mostly to industrial activities, traffic, mining and sand and gravel extraction, weather conditions and geographical location.
• Limitations the authors state:
  • The risk assessment method was simple and conservative, tends to overestimate, and its results cannot be considered definitive.
  • Exposure calculations assumed residents live full-time in Shahryar, although people spend much time indoors, where concentrations differ.
  • Fiber concentrations change daily and hourly, so they do not stay constant over a person's lifetime.
  • Risk calculations used only minimum and maximum concentrations, so the real risk should lie between the two.
  • Risk calculations were based on PCM total fiber counts and did not distinguish between fiber types.
  • Smoking habits and diet of exposed people were not considered.

Topics

Medical terms in this study, explained in our Lexicon: Lung Cancer, Mesothelioma, phase contrast microscopy (PCM).

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