The effects of air pollution within subway systems on public health has far been overlooked. A few previous studies have warned that particulate matter (PM)-bound metals in subway air pose a serious threat to public health, but these have been limited by insufficient risk measurement and limited regional data. Present study aimed to determine the levels of human health risk associated with PM10 and PM2.5-bound trace metals in twelve city subways across North America, Asia, and Europe using the human exposure method. Human health risks were estimated via ingestion, inhalation, and dermal exposure methods. The Monte Carlo statistical method using 50,000 iterations was adopted to calculate the probable risk levels for children and adults. Significant levels of non-cancer and cancer risks (CR) were found in subway systems at all regions, regardless of age, although CR were relatively higher in adults. Inhalation and dermal absorption, in which the acceptable range of carcinogenic risk for subway systems was exceeded. Exposure through ingestion made the greatest contributions to overall CR. Among the all subways Tehran and Seoul were estimated as higher CR zone (Total CR > 10−3). Therefore, the Asian subway systems is not only polluted with respect to particulate matter but also recognized as a highly CR zone among the other continents. Cr and Pb have been identified as PM-bound carcinogenic elements that significantly influence cancer risk by inhalation/dermal absorption and ingestion, respectively. Although, the subway is a convenient transportation system for millions of city inhabitants globally, but these findings support the view that indoor air pollutant levels in subway systems can have a serious impact on the cancerous and non-cancerous risks to human health. Strengthening the regulation of indoor air quality or the application of active air purification techniques in subway systems are highly suggested to manage the worst situation.
Bibliographical noteFunding Information:
This research was supported by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education (No. 2018R1A6A1A08025348 ); This study also partially supported by Korea Ministry of Environment (MOE) as “Knowledge-based environmental service Human Resource Development Project” and the National Research Foundation of Korea (NRF; No. 2019R1A4A1024764 ) grant funded by the Korea government ( MSIT ).
All Science Journal Classification (ASJC) codes
- Environmental Engineering
- Civil and Structural Engineering
- Geography, Planning and Development
- Building and Construction