Spatio-seasonal variation, distribution, levels, and risk assessment of airborne asbestos concentration in the most industrial city of Iran: effect of meteorological factors

Our plain-English summary of Spatio-seasonal variation, distribution, levels, and risk assessment of airborne asbestos concentration in the most industrial city of Iran: effect of meteorological factors, by M. Kermani, A. Jonidi Jafari, M. Gholami, et al (Environmental Science and Pollution Research International, 2021).

The study

• Authors: M. Kermani, A. Jonidi Jafari, M. Gholami, H. Arfaeinia, M. Yousefi, A. Shahsavani, F. Fanaei
• Journal: Environmental Science and Pollution Research International
• Published: 2021;28(13):16434-16446
• Cited by: 19 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Like other dangerous pollutants in the air, asbestos has negative and adverse effects on human and animal health. The present study is designed to determine the concentration of asbestos in the air of the most industrial city of Iran (Karaj) in 2018-2019. For this purpose, 4 samples were taken from different areas of the air of Karaj during a year with an SKC pump and flow of 6 L/min for 8 h and in 45 days, and a total of 68 samples of asbestos fibers were collected. Then, the samples were analyzed by phase-contrast microscope (PCM) and scanning electron microscopy (SEM). Eventually, the health effects of asbestos fibers were evaluated by the IRIS EPA method. The average concentration of asbestos fibers was 1.84 f/L PCM and 18.16 f/L SEM. Also, the results of statistical correlation analysis indicated that asbestos fibers are positively correlated with wind speed but negatively correlated with the other three parameters (temperature, relative humidity, and pressure). On the other hand, the average annual risk of asbestos fiber in the ambient air of Karaj for all samples was in the range of 4.32 × 10-6 to 1.81 × 10-4 which in some places had more danger than the recommended risk range. According to the EPA guidelines, carcinogenicity acceptable levels are in the range of 10-4 and 10-6. Values higher than 10-4 have more carcinogenic risk and values lower than 10-6 have a lower carcinogenic risk.

In plain English

This cross-sectional study measured asbestos fibers in the outdoor air of Karaj, Iran, which the authors call the country's most industrial city. From March 2018 to March 2019, the authors collected 68 air samples at 17 stations in low-, medium- and high-traffic areas and counted fibers by phase-contrast microscopy (PCM) and scanning electron microscopy (SEM). The four-season average was 1.84 fibers per liter by PCM and 18.16 by SEM. Station 5 had the highest average (3.31 f/L PCM), station 13 the lowest (1.06 f/L PCM). Levels were highest in summer, then winter. SEM analysis indicated about 35% of counted fibers were non-asbestos and tremolite was the most common type. Fiber levels correlated positively with wind speed and weakly negatively with temperature and humidity; the negative correlation with pressure was not statistically significant. Using PCM results, the authors reported excess lifetime cancer risks of 4.32 × 10^-6 to 1.81 × 10^-4, though their own table lists a higher maximum, 3.54 × 10^-4, for ages 16 to 30. The authors concluded that residents face a serious health risk.

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: Cross-sectional descriptive air-monitoring study with a modeled cancer risk assessment (US EPA IRIS method)
• Who was studied: Outdoor (ambient) air at 17 sampling stations across Karaj, Iran, grouped by traffic load. Sampling ran from March 21, 2018, to March 20, 2019, for a total of 68 samples. The risk estimates were for the city's general population (about 2.5 million people), by age group.
• Exposure: Airborne asbestos fibers in ambient air. Samples were drawn at 6 L/min for 8 hours onto cellulose (MCE) filters and analyzed by PCM (NIOSH 7400) and SEM with EDX. Fiber types identified by SEM-EDX were crocidolite, chrysotile and tremolite. Suggested sources included traffic (brakes and clutches), construction and industry.
• Main results:
  • The four-season average concentration for the whole city was 1.84 fibers per liter by PCM and 18.16 fibers per liter by SEM.
  • Station 5 had the highest four-season average (3.31 f/L PCM, 29.60 f/L SEM), followed by station 8 (3.23 f/L PCM, 27.8 f/L SEM).
  • Station 13 had the lowest average annual concentration (1.06 f/L PCM, 8.71 f/L SEM).
  • Summer had the highest fiber levels and winter the second-highest.
  • SEM-EDX analysis indicated that about 35% of the counted fibers were non-asbestos.
  • Based on the SEM images, tremolite was the most common fiber type in Karaj air.
  • Pearson correlation results (Table 2) were: wind speed R 0.34 (p 0.017), a positive correlation; temperature R −0.324 (p 0.016) and relative humidity R −0.147 (p 0.012), both weak negative correlations. The negative correlation with pressure was not statistically significant (R −0.179, p 0.324).
  • The risk assessment used PCM concentrations. The authors state an excess lifetime cancer risk range of 4.32 × 10^-6 to 1.81 × 10^-4 for the general public across all age groups. In their Table 3, however, 1.81 × 10^-4 is the maximum for ages 6 to 16, and the maximum for ages 16 to 30 is 3.54 × 10^-4. The EPA target range they cite is 1 × 10^-6 to 1 × 10^-4.
  • The highest estimated exposure concentrations and cancer risks were in the 16-to-30-year age group.
• The authors' conclusion: The authors concluded that Karaj has very high airborne asbestos concentrations, higher than World Health Organization guidelines. They also concluded that the estimated cancer risk was much higher than recommended values and that residents face a serious health risk.
• Limitations the authors state:
  • The PCM method, on which the risk assessment was based, cannot tell asbestos fibers from non-asbestos fibers.
  • PCM cannot identify the type of asbestos fiber and misses very thin fibers.
  • Other weather factors were not measured, such as rainfall, dew point and ultraviolet rays.

Topics

Medical terms in this study, explained in our Lexicon: Scanning Electron Microscopy (SEM), Carcinogenic.

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