Occurrence, spatial distribution, seasonal variations, potential sources, and inhalation-based health risk assessment of organic/inorganic pollutants in ambient air of Tehran

Our plain-English summary of Occurrence, spatial distribution, seasonal variations, potential sources, and inhalation-based health risk assessment of organic/inorganic pollutants in ambient air of Tehran, by M. Kermani, Z. Asadgol, M. Gholami, et al (Environmental Geochemistry and Health, 2021).

The study

• Authors: M. Kermani, Z. Asadgol, M. Gholami, A.J. Jafari, A. Shahsavani, B. Goodarzi, H. Arfaeinia
• Journal: Environmental Geochemistry and Health
• Published: 2021;43(5):1983-2006
• Cited by: 15 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The present study evaluated the concentrations, spatial distribution, seasonal variations, potential sources, and risk assessment of organic/inorganic pollutants in ambient air of Tehran city. Totally, 180 air samples were taken from 9 sampling stations from March 2018 to March 2019 and were analyzed to determine the concentrations of organic pollutants (BTEX compounds and PM2.5-bound PAHs) plus inorganic pollutants (PM2.5-bound metals and asbestos fibers). The results revealed that the mean concentrations of ∑ PAHs, BTEX, ∑ heavy metals, and asbestos fibers were 5.34 ng/m3, 60.55 µg/m3, 8585.12 ng/m3, and 4.13 fiber/ml in the cold season, respectively, and 3.88 ng/m3, 33.86 µg/m3, 5682.61 ng/m3, and 3.21 fiber/ml in the warm season, respectively. Source apportionment of emission of the air pollutants showed that PAHs are emitted from diesel vehicles and industrial activities. BTEX and asbestos are also released mainly by vehicles. The results of the inhalation-based risk assessment indicated that the carcinogenic risk of PAHs, BTEX, and asbestos exceeded the recommended limit by The US environmental protection agency (US EPA) and WHO (1 × 10-4). The risk of carcinogenesis of heavy metal of lead and chromium also exceeded the recommended limit. Thus, proper management strategies are required to control the concentration of these pollutants in Tehran's ambient air in order to maintain the health of Tehran's citizens.

In plain English

This study measured air pollutants at 9 monitoring stations in urban northeast Tehran, Iran, in warm and cold seasons (May 2018 to March 2019 according to the methods; the abstract gives March 2018 as the start). Besides PAHs, BTEX compounds and metals, the authors counted airborne asbestos fibers by phase contrast microscopy; fiber types were not named. Mean asbestos levels were 4.13 × 10^-3 fibers/ml in the cold season and 3.21 × 10^-3 fibers/ml in the warm season. The abstract omits the factor of 10^-3. Both values exceeded the World Health Organization value of 0.0022 fibers/ml cited by the authors. Levels were highest at station S4, near a spinning and fiber production factory, followed by high-traffic stations S8 and S2. The authors attributed asbestos mostly to vehicle parts such as brakes. They estimated the public's excess lifetime cancer risk from asbestos at 1.77 to 3.56 per 10,000 people, using minimum and maximum fiber counts, and judged it above the US EPA target range. Estimated cancer risks from PAHs, benzene, ethylbenzene, chromium and lead also exceeded the recommended limits. The authors concluded that these pollutants can pose serious health risks to Tehran's citizens.

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 seasonal comparison, spatial mapping, source apportionment and inhalation-based health risk assessment (US EPA methodology)
• Who was studied: Ambient air at 9 monitoring stations in urban northeast Tehran, Iran (one industrial, two high-traffic, the rest middle and low traffic). The methods give the period as May 2018 to March 2019; the abstract gives March 2018 to March 2019. The methods report 108 samples in warm and cold seasons, including 36 for asbestos. Risks were modeled for children and adults and, for asbestos, for age groups from 0 to 30 years.
• Exposure: Airborne asbestos fibers in outdoor city air (fiber type not specified). Samples were taken for 8 hours at 6 l/min, 3 m above ground, and counted by phase contrast microscopy using the NIOSH 7400 method. The study also measured PM2.5-bound PAHs and metals, and BTEX compounds.
• Main results:
  • Mean asbestos concentration was 4.13 × 10^-3 F/ml in the cold season and 3.21 × 10^-3 F/ml in the warm season.
  • Asbestos concentrations in both seasons exceeded the World Health Organization value of 0.0022 F/ml cited by the authors.
  • The highest annual asbestos concentration was at station S4, which the authors note is near a spinning and fiber production factory. Next were the high-traffic stations S8 and S2.
  • The authors attributed the high asbestos level mostly to vehicle parts. This was an interpretation citing earlier work; no formal source model was applied to asbestos.
  • For the public exposure scenario, the estimated total excess lifetime cancer risk from asbestos ranged from 1.77 × 10^-4 (minimum fiber counts) to 3.56 × 10^-4 (maximum fiber counts).
  • The authors judged that the asbestos risk exceeded the US EPA target range of 1 × 10^-6 to 1 × 10^-4.
  • Estimated lifetime cancer risk in children was 6.62 × 10^-3 for benzene and 9.87 × 10^-3 for ethylbenzene.
  • Cancer risk from chromium and lead was above 1 × 10^-4 in both children and adults. For chromium it was 2.81 × 10^-3 in children and 1.21 × 10^-3 in adults; for lead it was 1.98 × 10^-4 in children and 1.17 × 10^-4 in adults.
  • Pollutant concentrations were higher in the cold season than in the warm season.
• The authors' conclusion: The authors concluded that concentrations of PAHs, BTEX, heavy metals and asbestos fibers in Tehran's air are significantly higher than recommended values and can pose serious health risks to Tehran's citizens.
• Limitations the authors state:
  • PAHs and metals were measured only on PM2.5 particles, and only the particle phase of PAHs was analyzed, so the reported PAH and metal values may be underestimated.
  • Only the particulate phase of PAHs was analyzed, although PAHs are also released as gas.
  • The source apportionment and risk assessment methods used can have a bias.

Topics

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

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