Heavy smog blanketed Korea this week blown in by northwesterly winds from China. The concentration of ultrafine particles is often at its worst between December and March, with most of the smog comes from Beijing and surrounding Hebei Province.
The smog crosses the West Sea and reaches the Korean peninsula anywhere between six hours and a day later. Meteorologists say the smog is diluted as it crosses the West Sea, but 40 to 50 percent still reaches Korea.
On Thursday, the concentration of ultrafine particles in Dongducheon, Gyeonggi Province north of Seoul, reached 255㎍/㎥, five times the normal level in the region. It stood at 138 ㎍/㎥ in Incheon and 112㎍/㎥ in the capital.
The concentration of ultrafine particles in Dongducheon was 2.5 times greater than the safe level set by the Environment Ministry of 100㎍/㎥ per day.
Winter smog carries more ultrafine particles and is more hazardous than the sandstorms that blow over here in spring. According to the National Institute of Environmental Research, around 20 to 30 percent of sandstorms consist of ultrafine particles, but smog contains 60 to 70 percent.
Dust can cause asthma and other respiratory illnesses as well as cardiovascular diseases, but the most hazardous substance is ultrafine particles that are not filtered by the bronchial tubes and directly enter the lungs, where they can cause pneumonia.
Smog also contains toxic heavy metals such as lead, cadmium and arsenic. "Unlike sandstorms, smog contains various chemicals and heavy metals that react with the sunlight and multiply," said Chun Young-shin at the Korea Meteorological Administration.
It is difficult to predict smog levels since it is not clear where it originates and how many pollutants it contains. The Chinese government does not reveal data about the origin of pollutants, but the most polluted parts of China are along the east coast, which is near Korea.
Chances of smog increase each time northwesterly winds blow over from China. Although the concentration of ultrafine particles in smog weakened temporarily between Wednesday and Thursday, the KMA warned it will rise again on Friday.
Korea, China and Japan decided in a regional meeting in May to form a joint committee to discuss this problem. Chung Bok-young at the Environment Ministry said the Korean government hopes to gain access to Chinese data while offering to share clean fuel technology with China.
But it will take some time before the trilateral group can be formed. "The only thing we can do right now is to try to predict exact smog levels and prepare to deal with it as best we can," said a KMA official.
At present, the KMA announces forecasts only of fine particles but not of ultrafine ones. There are only 20 sensors in Korea that can detect ultrafine particles. The ministry plans to provide forecasts for ultrafine particles starting in 2015.