SEOUL-- Two consecutive days of exposure to fine dust can raise the risk of death by 0.5 percent, a joint study by researchers from South Korea, Japan and China said Tuesday.

Published in Environment International, the study tracked the associations between mortality and extended exposure to microdust by analyzing data between 1993 and 2009 for periods when air pollution concentration exceeded the normal range (75 micrograms per cubic meter) for two days or longer.

In case of South Korea, the longest streak of 6.96 days of heavy air pollution spiked the mortality risk to nearly 3.4 percent, the study said.

Twenty-eight cities from the three countries were surveyed for the study. Results showed that with each additional consecutive day of high pollution, the total daily non-accidental mortality numbers increased for all countries. The increase ranged from 0.68 percent in Japan to 0.48 percent in South Korea and 0.24 percent in China.

The annual maximum number of consecutive days with elevated fine dust was 2.4 days in Japan, 6.96 days in South Korea and 42.26 days in China. The increases in non-accidental deaths for those days were 1.64 percent for Japan, 3.37 percent for South Korea and 10.43 percent for China, according to the study.

The biggest increase in mortality risk was in respiratory disease-related deaths, which marked 8.1 percent in South Korea and 33.4 percent in China.

The study concludes that the duration and intensity of fine dust pollution is associated with risks of death.

"A better understanding of differential risks will help guide public policy decisions regarding risk assessments and air pollution standards," it said.

Source: Yonhap News Agency