In Japan, long-term monitoring of acid deposition is carried out to detect its effects as early as possible and to forecast its effects in the future.

Dust and Sandstorms (DSS), which blows over from China and Mongolia, has been seen more frequently in Japan than in the past. China, Republic of Korea, Japan, and some other nations share a common interest in dealing with DSS. In Japan, the government has established DSS monitoring systems. In addition, China, Mongolia, Korea, Japan, the United Nations Environment Programme (UNEP), and some other international organizations are working together to explore effective measures to deal with DSS in the future.

## (2) Photochemical Oxidants

Photochemical oxidants is a collective term that includes ozone and some other secondary substances generated in the presence of sunlight (photochemical reaction) from nitrogen oxides (NOx), volatile organic compounds (VOCs), or other primary pollutants emitted from factories, businesses, or automobiles. Photochemical oxidants are the cause of photochemical smog, which causes eye and throat irritation and respiratory distress. In almost all regions throughout Japan, photochemical oxidants still exceed the environmental quality standard (EQS) (a one-hour value of 0.06 ppm or less).

As one of the measures to combat photochemical oxidants, the Air Pollution Control Law was revised in May 2004 to control VOC emissions from factories. By combining VOC emission regulations and voluntary measures by business operators, the revised law provides an effective solution for curbing VOC emissions. Since April 1, 2006, VOC-emitting firms have been required to submit notification of their VOC-emitting plants and comply with the emission criteria. As a result, these firms are expected to take voluntary action. In accordance with the Air

Changes in the Number of Monitoring Stations by Photochemical Oxidant Concentration Level (AAPMSs and RAPMSs) (FY 2000 – 2004)

Source: Compiled from the Ministry of the Environment, FY 2004 Report on the State of Air Pollution.

Pollution Control Law, Japan’s regulatory authority has put in place tighter restrictions on VOCs emitted from automobiles.

Through the Atmospheric Environmental Regional Observation System (nickname: Soramame-kun), the government collects on a real-time basis the nationwide atmospheric environment data measured at a prefectural level as well as the photochemical oxidant warning data, and makes these data available on the Internet.

## (3) Nitrogen Oxides

Nitrogen oxide (NOx) is a by-product of combustion, generated mainly from stationary sources (such as factories) and mobile sources (such as motor vehicles). NOx contributes to photochemical oxidants, suspended particulate matter, and acid deposition. High concentrations of Nitrogen dioxide (NO $ _{2} $ ) may have a negative impact on health by causing irritation to the respiratory organs.

Compared to the previous year, the achievement rates for the $ NO_{2} $ -related EQSs were slightly improved in FY2004. The achievement rate of the ambient air pollution monitoring stations (AAPMSs) was 100%, and that of the roadside air pollution monitoring stations (RAPMSs) was 89.2%.