HO CHI MINH CITY, Jan. 3 (Xinhua) -- Smog that has appeared frequently in Vietnam's Ho Chi Minh City, with the most recent recorded on Wednesday, shows that local air pollution is now at an alarming level.

The warning was made by Ho Quoc Bang, head of the air pollution and climate change division at the Institute for Environment and Natural Resources under the Vietnam National University - Ho Chi Minh City, Vietnam News Agency reported.

He said traffic, construction and industrial activities are the main causes of air pollution in cities. Traffic activities discharge nearly 85 percent of the total carbon monoxide emissions and many other hazardous substances.

Air pollution at construction sites is five or six times higher than the standard. These activities also produce noise that worsens air pollution.

According to the city's environmental protection sub-department, local air pollution is mainly caused by floating dust and noise from traffic activities. Up to 72 percent of the dust data and 97 percent of the noise statistics collected at 12 locations exceeded Vietnam's standards.

Bang said air pollution ranks fourth among the causes of premature death in the world. In Vietnam, air pollution makes about 1.5 million people suffer from chronic lung disease every year.