Impact of introducing net-zero carbon strategies on tropospheric ozone (O3) and fine particulate matter (PM2.5) concentrations in Japanese region in 2050.

In this study, we estimated the future emission inventory of primary air pollutants in Japan in 2050 after introducing low-carbon technology based on the results of the socio-economic model provided by the Japanese government. The results suggested that introducing net-zero carbon technology would contribute to a 50-60 % decrease in primary NOx, SO2, and CO emissions and a ~30 % decrease in primary emissions of volatile organic compounds (VOCs) and PM2.5. The estimated emission inventory and future meteorological conditions in 2050 were applied as inputs to a chemical transport model. A scenario involving the application of future reduction strategies with relatively moderate global warming (RCP4.5) was evaluated. The results showed that the concentration of tropospheric ozone (O3) was highly reduced compared with that in 2015 after applying net-zero carbon reduction strategies. On the other hand, the fine particulate matter (PM2.5) concentration under the 2050 scenario was expected to be equal or higher because of the growth in secondary aerosol formation caused by the increase in short-wave radiation. Finally, the premature mortality change from 2015 to 2050 was analyzed, and the change in air quality contributed by net-zero carbon technology will contribute to a ~4000 decrease in premature deaths in Japan.

Exposure and risk assessment of 1,3-butadiene in Japan.

1,3-Butadiene is on the list of Substances Requiring Priority Action published by the Central Environmental Council of Japan in 1996. Emission of 1,3-butadiene has been controlled by a voluntary reduction program since 1997. Although the industrial emission of 1,3-butadiene in Japan has decreased in recent years, primarily due to a voluntary industrial emissions reduction program, the risks of exposure to it remain largely unknown. We assessed the risks and consequences of exposure to 1,3-butadiene on human health. A remarkable advantage of our risk assessment approach is the detailed assessment of exposure. Previously, we developed two different models that can be applied for the assessment of exposure: the first, the AIST-ADMER model estimates regional concentration distributions, whereas the second, the METI-LIS model estimates concentration distributions in the vicinity of factories. Both models were used for the assessment of exposure to 1,3-butadiene. Using exposure concentration and carcinogenic potency determined and reported by Environment Canada and Health Canada, we evaluated the excess lifetime cancer risk for persons exposed to 1,3-butadiene over the course of a lifetime. The results suggested that the majority of the population in Japan has an excess lifetime cancer risk of less than 10(-5), whereas a small number of people living close to industrial sources had a risk of greater than 10(-5). The results of the present assessment also showed that 1,3-butadiene in the general environment originates primarily from automobile emissions, such that a countermeasure of reducing emissions from cars is expected to be effective at reducing the total cancer risk among Japanese. On the other hand, individual risks among a population living in the vicinity of certain industrial sources were found to be significantly higher than those of the population living elsewhere, such that a reduction in emissions from a small number of specific industrial sources should be realized in order to reduce the high level of individual risk. Based on the results of our assessment, the Industrial Structure Council of the Ministry of Economy, Trade and Industry (METI) in Japan decided to announce that the voluntary reduction program had been successful, and that emissions reductions should no longer be targeted across all industries in general, but instead that such reductions should be carried out in a small number of selected factories that emit excessively large amounts of emissions.

Estimating ambient concentration and cancer risk for 1,3-butadiene in Japan.

A detailed assessment of 1,3-butadiene exposure was performed for the purpose of risk assessment in Japan. The concentration of 1,3-butadiene and the 1,3-butadiene-exposure-related lifetime excess cancer risk in the general environment and in the vicinity of industrial point sources were estimated using two different types of diffusion models: the National Institute of Advanced Industrial Science and Technology-atmospheric dispersion model for exposure and risk assessment (AIST-ADMER) model ver. 1.0 for the estimation of regional scale concentrations and the Ministry of Economy, Trade and Industry - low rise industrial source dispersion (METI-LIS) model ver. 2.01 for the estimation of local concentrations near industrial sources. The calculated results indicate that the annual mean concentrations of 1,3-butadiene in residential areas are generally less than 0.5 microg/m(3), but in a few area near industrial point sources they exceed 1.7 microg/m(3), corresponding to a lifetime excess cancer risk of 10(-5). Using data on exposure concentrations and cancer unit risk, the lifetime excess cancer risk for persons exposed to 1,3-butadiene in Japan was evaluated. The results indicate that an extremely small number of people have a risk of developing 1,3-butadiene-exposure-related cancer that is greater than 10(-5), while that of most of the population in Japan is between 10(-5) and 10(-6). The total 1,3-butadiene-exposure-related cancer risk in Japan was calculated as 2.0 cases/year. A large proportion of the cancer risk was associated with general environmental areas. However, the individual risks of the population living in the vicinity of industrial point sources were significantly higher than those of the population living in the general environment.

Estimation of aggregate population cancer risk from dichloromethane for Japanese using atmospheric dispersion model.

The aggregate population cancer risk from dichloromethane exposure for each prefecture and for all of Japan was estimated using an atmospheric dispersion model and by considering the population within each calculation mesh (about 5 x 5 km). Indoor dichloromethane exposure was also taken into consideration. The number of lifetime dichloromethane-exposure-induced cancer cases for all of Japan was estimated to be only 1.3 (of 125 million people) using a most recently reported unit risk value. It was also found that the average ratio of the contribution to the aggregate population cancer risk attributable to outdoor emission sources (industrial factories) to the total emission sources was no more than 40% for all of Japan. From these results, it is believed that further reductions in dichloromethane emissions from industrial factories on a prefectural or a nationwide scale would not be effective in reducing cancer risk. It was also revealed that the average ambient concentration of dichloromethane measured at monitoring stations for hazardous air pollutants in each prefecture is a good measure of the average ambient dichloromethane concentration to which people in that prefecture are exposed. Therefore, it was suggested that the aggregate population cancer risk from dichloromethane exposure can be effectively estimated for entire Japan by simply using the average ambient concentration measured at monitoring stations in all of Japan taking into consideration indoor dichloromethane exposure.