Air pollution in Tokyo down by half

Mainichi reports that levels of airborne soot, emitted mainly by diesel vehicles, have declined by half in downtown Tokyo over the past four years. Strict rules on emissions are clearly working.

A University of Tokyo research laboratory say the findings prove that the government's efforts to reduce emissions of black carbon, including a 2003 ban on diesel vehicles that cannot meet emission standards in Tokyo, Chiba, Saitama and Kanagawa prefectures, have been effective:

Black carbon, emitted from diesel engines, amongst other sources, is suspected to be both an allergen and a carcinogen, they say. Moreover, experts say reductions in black carbon emissions can help reduce the effects of global warming.

"It's important to measure black carbon levels in areas outside Tokyo to evaluate the effects of restrictions (on diesel vehicle exhaust fumes)," said Yutaka Kondo, a professor at the University of Tokyo Research Center for Advanced Science and Technology. "Japan's strengthening of restrictions will help encourage other Asian cities, such as Beijing and Bangkok where the density of black carbon is higher than in Tokyo, to take their own measures."

The research center used a newly developed device to precisely measure the airborne density of black carbon in the Komaba district of Meguro-ku and Shinjuku-ku since May 2003.

Levels of black carbon in Komaba, which stood at 0.0023 milligrams per cubic meter per hour between 2003 and 2005, dropped by half to 0.0011 milligrams over the January-July period of this year, they say.