Naoya Kojima

Structural analysis of the interrelationship between economic activities and water pollution in Vietnam in the period of 2000–2011

Rapid economic growth and poor waste management have left Vietnam with severe water pollution problems. It is thus important to develop a model to evaluate the relationship between economic activities and water pollution to identify water pollution mitigation strategies within the context of economic development. Recent works have demonstrated the effectiveness of the input–output model in analyzing the interplay between the economy and the environment. To comprehensively understand this relationship, the behavior and trend of water pollution during a specified period should be investigated on. The interaction of different economic sectors and its impacts on water pollution should also be analyzed. For the Vietnamese economy, such aspects have not been fully addressed in previous studies. This work thus examines the state of water pollution in Vietnam as indicated by water quality parameters, total suspended solids and biological oxygen demand, with particular attention to the individual contribution of various economic sectors. The period between the years 2000 and 2011 is taken into account in this work. Environmentally extended input–output analysis coupled with vertical integrated coefficient method is used to analyze the interindustry linkages of sectors and to classify sector role as either key sector or pollution puller or pusher. The pollution trend reveals the tremendous increase in total suspended solids from 345,000 tonnes in 2000 to 1,199,000 tonnes in 2011, while the total biological oxygen demand increased from 43,400 tonnes in 2000 to 123,000 tonnes in 2011. Results show that the basic metals industry was the major contributor of total suspended solids, while the food, beverage and tobacco and agriculture, fishery and forestry sectors contributed most to the biological oxygen demand. The results of sectoral linkage evaluation highlight that food, beverage and tobacco and agriculture, fishery and forestry sectors were key sectors for both water quality parameters. These results provide environmental managers and policy maker insights on how to prioritize economic sectors to achieve emission reduction targets.

Flow, stock, and impact assessment of refrigerants in the Japanese household air conditioner sector

Refrigerants provide society with great benefits while have the potential to cause adverse effects on the environment and human health. The present study estimated time-dependent flows and stocks and assessed the effects of refrigerants (R-22, R-410a, and R-32) in household air conditioners in Japan. It was found that stock of R-22 and R-410a peaked at 49,147t in 2000 and 55,994t in 2017, respectively. The largest flow of R-22 and R-410a to waste phase occurred at 3417t/yr. in 2005 and 4011t/yr. in 2023, respectively. The total global warming potential (GWP) due to refrigerant emissions increased from 3.6kt CO2 eq. in 1952 to 6999kt CO2 eq. in 2019, and then decreased to 5314kt CO2 eq. in 2030. The ozone depletion potential (ODP) peaked at 141t CFC-11 eq. in 2002. When substituting R-410a for R-22, the ODP decreased 50% while the GDP increased 8%. When substituting R-32 for R-410a, there was no effect on the ODP while the GDP decreased 6%. The human health damage due to the global warming effect of refrigerant emission was much higher than that due to the ozone depleting effect. The refrigerant emission in use and waste management phases dominated the human health damage. The dynamic estimation not only allows us to evaluate the performance of past policies but also supports the future sustainable management associated with the health effects of refrigerants.

Flows, stocks, and emissions of DEHP products in Japan

The usage of products containing Bis (2‑ethylhexyl) Phthalate (DEHP) is widespread, mainly through the great variety of PVC products. However, DEHP has become a worldwide concern, due to the potential health and environmental risks it presents. In this study, material flow analysis and emission estimations for DEHP products in Japan, from 1948 to 2030, were performed. Moreover, an evaluation of the potentially damaging impacts on human health and the environment was completed through a lifecycle impact assessment approach. The analysis focused on three representative lifecycle phases - Production, Use and Treatment and Disposal. The peak flows of DEHP from Production to the Use phase were in 1996 with 285,300 tons for shipment and the stocks peaked in 2001 with 1,981,908 tons. Accordingly, in 2006 the peak of DEHP waste to the Treatment and disposal phase was 190,792 tons. The primary emissions were observed in the Use phase, due to the large stocks, with DEHP mostly being released to the pedosphere. The total emissions from the Use phase reached the maximum of 48,960 tons in 2000, whereas in the Production and Treatment and disposal phase it was 248 tons and 15 tons, respectively. Subsequently, concerning the evaluation of impacts, the damage to the human health was the most widespread impact, totaling 13,782 disability-adjusted life years (DALYs), compared with the damage to the ecosystems, with 0.12 species·year. Furthermore, the risk-risk tradeoffs between the lifecycle phases were clarified throughout the years.

Application of fuzzy c-means clustering to PRTR chemicals uncovering their release and toxicity characteristics

Increasing manufacture and usage of chemicals have not been matched by the increase in our understanding of their risks. Pollutant release and transfer register (PRTR) is becoming a popular measure for collecting chemical data and enhancing the public right to know. However, these data are usually in high dimensionality which restricts their wider use. The present study partitions Japanese PRTR chemicals into five fuzzy clusters by fuzzy c-mean clustering (FCM) to explore the implicit information. Each chemical with membership degrees belongs to each cluster. Cluster I features high releases from non-listed industries and the household sector and high environmental toxicity. Cluster II is characterized by high reported releases and transfers from 24 listed industries above the threshold, mutagenicity, and high environmental toxicity. Chemicals in cluster III have characteristics of high releases from non-listed industries and low toxicity. Cluster IV is characterized by high reported releases and transfers from 24 listed industries above the threshold and extremely high environmental toxicity. Cluster V is characterized by low releases yet mutagenicity and high carcinogenicity. Chemicals with the highest membership degree were identified as representatives for each cluster. For the highest membership degree, half of the chemicals have a value higher than 0.74. If we look at both the highest and the second highest membership degrees simultaneously, about 94% of the chemicals have a value higher than 0.5. FCM can serve as an approach to uncover the implicit information of highly complex chemical dataset, which subsequently supports the strategy development for efficient and effective chemical management.

An input–output linear programming model for assessing climate policy considering economic growth

Deploying new strategies to reduce the effect of climate change may constrain economic growth. It is thus necessary to develop a model which evaluates the trade-off between economic and environmental influences prior to a policy implementation. Recent studies have proved the effectiveness of input–output linear programming model in identifying the optimal solutions when different climate policies are considered. However, analyzing sectoral linkage to give priority sectors and then finding optimal solutions through reducing pollution from these sectors, which help avoid the economic losses from low-polluting sectors, have not been figured out in previous works. This study first uses input–output an (IO) analysis to provide a measure of structural interdependence among economic sectors and present priority sectors. An IO optimization model is then developed for minimizing the total greenhouse gas (GHG) emissions, in order to identify strategies for GHG intensity reduction in Vietnam, focusing on the priority sectors. In addition, the effect of GHG emissions on human health using the disability adjusted life years (DALY) is further evaluated. Six scenarios are considered to identify the potentials of highest GHG intensity reduction that can be obtained by the year 2020. These scenarios encompass BAU, the consideration of different GDP growth rates, differentiated economic sector growth, economic restructure, and the adaptation of lower-pollution technology implementation for the priority sectors. Each scenario quantifies sectoral final demand, sectoral gross domestic output, sectoral GHG emissions, GHG intensity, and DALY. The linkage analysis results indicate that agriculture, fishery and forestry, transport and communication, personal, community and household, manufacturing of non-metallic mineral products, and mining and quarrying are priority sectors. The optimization solutions present that the best strategy is by taking advantages of identified measures. The best solution obtains 20.3% reduction in GHG intensity compared to baseline. These obtained results become the useful suggestions for decision makers and environmental management in designing successful environmental regulations.

Decabromodiphenyl Ether (DecaBDE) in Electrical and Electronic Equipment in Japan: Stock, Emission, and Substitution Evaluation

DecaBDE has been widely used as flame retardant in electrical and electronic equipment (EEE). It has recently been listed in Annex A of the Stockholm Convention. The time series flow, stock, and emission of DecaBDE in EEE in Japan were quantified. On this basis, a risk/risk trade-off analysis of substituting DecaBDE with triphenyl phosphate (TPhP) that is one possible phosphorus-based alternative was conducted. The stock of DecaBDE reached a maximum of ∼42 000 t in 1995. Even though the demand flow was negligible in 2030, the stock was modeled to be still ∼470 t. The outflow of DecaBDE, from the use phase to the disposal phase, peaked at ∼4500 t/yr. in 2001. The DecaBDE emission to atmosphere was mainly derived from the production phase before 1990. The use phase became the largest contributor to the total emission from 1995 to 2000. Whereas the disposal phase dominated the total emission from 2000 onward. In the substitution analysis, a trade-off between human and ecological health effect was revealed in case of replacing DecaBDE with TPhP. This study attempted to give an overall picture of DecaBDE application at national level providing insights into relevant environmental policy making.