Smog levels are on the increase in Japan, and according to the Japan Times, many think that China is the blame:

Toshimasa Ohara, a chief researcher at the National Institute for Environmental Studies, said, “It’s quite possible this is cross-border pollution from the Asian continent.”

Last June, Fukuoka Gov. Wataru Aso told then Environment Minister Masatoshi Wakabayashi that Japan’s photochemical smog may be caused by contaminants from China. “If such a cause-and-effect relationship becomes clear, I would like you to strongly call on China to reduce such emissions,” he said.

China’s nitrogen oxide emissions have increased 3.8 times in the last 25 years. If such emissions continue to increase, the annual average ozone density in Japan will likely reach 60 ppb by 2020.

Ozone has a strong greenhouse effect, accelerates global warming and is harmful to humans if inhaled. In North America and Europe, there are already moves to strengthen the regulatory limits for ozone.

The U.S. Environmental Protection Agency said ozone reduces lung functions and damages the trachea even in relatively low densities. The EPA proposed in June that the ozone in the air be limited to 70 to 75 ppb for eight hours from 80 ppb.

Some environmental protection groups said the proposal is still lukewarm and pointed to the need to further lower the limit to 60 ppb or below. The World Health Organization lowered its limit from 60 ppb to 50 ppb in 2005.

The article goes on to state that the increasing levels of ozone have been causing major declines in wheat and soybean production in China, and there is fear Japan may experience similar drops as the wind brings more smog clouds from the continent.