The main purpose of this project is to investigate air pollutants (PM2.5, metals, PAHs, VOCs, and acidic gas) in Taichung City by field campaigns and model simulations for further evaluations of health risk assessment and regulations of emission reduction plans. The project was conducted in four parts, as follows: (I) to collect and analyze ambient air pollutants in Taichung City; (II) to explore the concentration variations of air pollutants among different sampling sites and seasons; (III) to assess health risks based on the measurement of pollutant concentrations in situ; and (IV) to evaluate the contribution from the major pollution sources in Taichung and to investigate the draft for risk management.
Among the nine sampling districts, the highest mean concentrations of pollutants were found in the center district of Taichung City, while the lowest concentrations were found in the non-industry district. However, the concentrations among the nine sampling districts did not show a large amplitude of differences. The three-years sampling data also showed that in none of sampling stations had high concentrations of pollutants occurred obviously and consistently. For seasonal variations, mass concentrations of PM2.5, and concentrations of metal and PAHs in PM2.5 all had the lowest values in the summer season. Furthermore, PAHs showed the highest value in the winter season, while the seasonal variations were not obvious for VOCs. Compared with other investigation data from numerous studies, the pollutant concentrations of this project were within the range of previous studies. However, compared to the studies focusing on the effects of pollution sources at nearby sites, this study focusing on the air quality of the living environment for residents of Taichung City showed obviously lower values. Associated with wind direction and characteristic elements of pollution sources, a sampling site suggests that it was polluted by a steel plant.
This study calculated, evaluated, and thoroughly discussed the life-time average daily dose (LADD) and health risk assessments based on the measurement of pollutant concentrations in situ. The 50% percentile and 95% percentile of cancer risk in Taichung City were 7.61E-06 and 1.39E-05, respectively. The five top pollutants of cancer risk contributors in Taichung City were: As, benzene, Cr6+, Cd , and Ni. The results of the hazard indices of non-carcinogenic risk showed that the developmental system, reproductive system, and respiratory system were all higher than the minimum target risk level of 1 in Houli district, where the dominant pollutant was Ni. The hazard indices of non-carcinogenic risk for the nervous system was higher than 1 for Harbor district , Houli district ,and Industry-C district, where the dominant pollutant was Mn.
Based on the data on stack samples analysis in Taichung, the results of peer-reviewed scientific papers related to the industries in Taichung and the profiles in the USEPA Speciate database in conjunction with the emission dataset of TEDS 10, an emission dataset of 12 hazardous air pollutants: As, Benzene, Ni, Cr6+, Cd, PAHs, Dichloromethane, Pb, Mn, Hg, Toluene, Dioxin, was constructed.
The environmental variables for the modelling system were set up and the evaluations of the mesoscale meteorological modeling and regional air quality modeling for the base year conducted; the comparisons with observation were in good agreement. In addition, simulations of the 7 major emission sources were conducted and the results showed that the areas affected by these sources were always where they were located and the surrounding areas. In addition, the major sources with higher stack height and larger emission have more obvious impact in the whole city, compared to other major sources.
The risk management plans were suggested based on the results of environmental pollution surveys, the emission dataset of hazardous air pollutants and the simulation results of different emission reduction scenarios. It showed that steel industries and power plants are the major sources that need to reduce the hazardous air pollutants emission in the beginning. A long-term air pollutant control strategy can be developed by referring to the TCEQ and MATES in the States, in order to effectively reduce the environmental hazardous air pollutants.