Recent spikes in the concentration of PM2.5 air pollutants over wide areas of Japan have once again raised alarms over the health risks from the small particles. While increases in PM2.5 levels are often linked to pollutants drifting over from China, there are also domestic sources that warrant further study and coordinated cross-border action.

According to the Environment Ministry, the daily average concentration of PM2.5 in eight prefectures — Fukushima, Niigata, Toyama, Ishikawa, Fukui, Osaka, Hyogo and Kagawa — exceeded 70 micrograms per cubic meter on Feb. 26, setting off an alert under the government’s provisional guidelines. Local municipalities urged people to wear masks and avoid heavy exercise outdoors.

PM2.5 particles measure up to 2.5 microns, or 0.0025 millimeter, in diameter. These fine particulates can easily penetrate the lungs, causing asthma or raising the risk of lung cancer. They are also linked to arrhythmia, an irregular heartbeat condition.

Around the same time as the alert, a large part of northern China was shrouded in smog that included much greater concentrations of PM2.5. For days, Beijing was in its second-most serious smog alert with visibility down to a few hundred meters. The air-pollutant concentration reading in Beijing topped 500 — 20 times the World Health Organization’s recommended safe limit of 25

According to the Japan Weather Association, spikes in PM2.5 concentration in parts of Japan were likely the result of weather conditions that facilitated the inflow of pollutants from China as well as stable atmospheric patterns over Japan itself that trapped in pollutants including locally generated ones.

PM2.5 particles vary by type and composition. Sources range from factory smoke and car exhaust to volcanic gas. The government’s Meteorological Research Institute said rises in PM2.5 readings in the Kanto and Tokai regions last summer were partly attributable to gas containing sulfur dioxide released from Mount Sakurajima in Kagoshima Prefecture. The fact that some of these particulates are the result of chemical reactions in the atmosphere makes action against them difficult.

The hazards from PM2.5 pollution have been known since the 1970s. High concentrations were reported in some parts of Japan well before China faced serious pollution problems. Japan lags behind other industrialized economies in taking abatement action against PM2.5, but in 2009, it did establish relevant environment guidelines and is gradually building up its monitoring systems.

As of 2012, the PM2.5 pollution level had exceeded the per-cubic-meter safety ceiling of 15 micrograms (annual average) and 35 micrograms (daily average) at about 60 percent of the monitoring sites around the country. Much more needs to be done domestically to reduce the pollution, including further research on the particles themselves and better ways to monitor them.

China’s serious air pollution is an outcome of its having placed priority on rapid economic growth at the expense of the environment. As a major power, it now needs to take responsibility for the effects of this decision and to reduce its emissions.

The massive scale of China’s pollution and its cross-border impact means that regional cooperation is necessary. Japan should offer its knowledge and experience gained while battling its own severe air pollution problems in the past.

A regional acid-rain monitoring network involving 13 countries in East Asia, including Japan, China and South Korea, could serve as a model for such cooperation. Dialogue with China for joint action on the PM2.5 problem should not be sidelined by the current chill in bilateral diplomatic ties.

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