By Kim Se-jeong

Korea's Air pollution is far worse compared to that in other OECD developed countries, according to a U.S. non-profit organization.

According to the Health Effects Institute (HEI)'s recent report, "State of Global Air," Korea's annual average concentration of fine particulate matter PM 2.5 _ 2.5 nanometers in diameter _ increased from 26 micrograms per cubic meter in 1990 to 29 micrograms in 2015. In that year, the 35-state OECD average was 15 micrograms. Fine dust is a big pollutant.

Among other Asian countries, Korea's air pollution was better than China and North Korea _ 58 and 34 micrograms, respectively _ but worse than Japan which had 13 micrograms.

The level of ozone concentration in Korea also worsened over the the same period _ from 66 micrograms to 68. The OECD average went down to 60 from 61 micrograms.

"We're seeing increasing air pollution problems worldwide, and this new report and website details why the air pollution is a major contributor to early death," Dan Greenbaum, president of HEI said. "The trend we report shows that we have seen progress in some parts of the world _ but serious challenges remain."

Researchers from the University of Washington and University of British Columbia contributed to the story.

The Korean government's effort to curb fine dust emissions includes subsidizing obsolete diesel-run vehicles and the purchase of electric vehicles and shutting down old coal-fired power plants. Vehicles and coal are believed to be the main source of fine dust. Earlier this week, the government also announced a plan to restrict the number of cars on the highways.