Citizens of Seoul, S. korea, were put on highest alert Monday morning after the density of fine particles in the air hit a record level.
Seoul city officials said the city has been under siege since 1 a.m. when the density of sand, dust and aerosols, or fine solid or liquid particles suspended in the air, measured 1,042 micrograms per cubic meter. The figure hit a record 2,070 micrograms per cubic meter at 4 a.m. and is steadily decreasing, officials said.