Implications of toxicity testing for health risk assessment of vapor-phase and PM_2.5-bound polycyclic aromatic hydrocarbons during the diesel engine combustion

Abstract

It is challenging to estimate the health risks posed by exposure to particulate pollutants due to limited information for chemicals bound to particles in toxicity databases. This study predicted the cancer risks posed by the vapor-phase and fine particulate matter (PM_2.5)-bound polycyclic aromatic hydrocarbon (PAH) emissions during diesel combustion in an industrialized city in southern Taiwan by using two different approaches. In the first approach, the cancer risks were estimated based on the vapor-phase and PM_2.5-bound PAH concentrations in the exhausts, while the observations of the vapor-phase and PM_2.5-bound samples in the in vitro cell toxicity tests, including Ames test, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and tumor necrosis factor-alpha (TNF-alpha) detection were employed to modify the risks posed by the PM_2.5-bound emission in the second approach. The results show that the vapor-phase concentrations of total PAH (30,944-118,565 ng/m³) and benzo(a)pyrene toxic equivalence quotient (BaP-TEQ; 8.2–69.1 ng/m³) were significantly higher than the PM_2.5-bound concentrations (the total concentration and BaP-TEQ were 11.9–45.0 and 0.27–12.94 ng/m³, respectively), resulting in the dominance of the vapor-phase risk (71–98%) over the total risk (8.92 × 10⁻⁹–1.03 × 10⁻⁷). With the modification of the cell test results, the total risks were increased to 1.62 × 10⁻⁸–1.33 × 10⁻⁷. The ratios of the PM_2.5-bound risk to the total risk in different conditions have been increased by 2–26 times (from 2–29% to 45–61%), suggesting the mixture effect of PM-bound pollutants on health risk assessment.

Keywords:

• Health risk assessment
• In vitro cell toxicity test
• polycyclic aromatic hydrocarbon
• fine particulate matter (PM_2.5) diesel combustion

Acknowledgments

This research was conducted under the auspices of the Ministry of Science and Technology (MOST) under contact numbers (109-2811-E-110-507, 107-2221-E-110-003-MY3, and 106-EPA-F-011-001). Additional financial support from the NSYSU-KMU JOINT RESEARCH PROJECT, (#NSYSUKMU 105-I007) and Our Fellow Man Alliance (OFMA) in Taiwan is greatly appreciated.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this article.

Additional information

Funding

This work was supported by the Ministry of Science and Technology and the NSYSU-KMU Joint Research Project, Taiwan.