Mercury concentrations higher than the national average have been detected at the peak of Mt. Fuji, which might be caused by cross-border pollution from China, a research group has announced.
The group, which includes Prof. Osamu Nagafuchi at the University of Shiga Prefecture, measured 2.8 nanograms of mercury per cubic meter of air at the summit of Mt. Fuji in August, and a record 25.1 nanograms in 2007.
The Environment Ministry will begin a fixed-point observation project in the Asia-Pacific region jointly with the United States, Vietnam and other nations next year.
Though the observed figures are not at a level harmful to humans, they exceeded the average around the mountain peak, which is almost completely free from factory pollutants.
"When analysing the situation, including weather conditions, the reason seems to be contaminated air flowing over from China," said Nagafuchi, an expert in environmental science.
According to the Environment Ministry, the average figure at all 261 observation points in the nation was 2.1 nanograms in fiscal 2011.
A guideline of the Air Pollution Control Law stipulates the yearly average should be 40 nanograms or lower to prevent health problems.
Nagafuchi and other researchers have carried out a survey at the peak of Mt. Fuji, 3,776 meters above sea level, for about two weeks every summer since 2007.