The air quality in western parts of Taiwan was at an unhealthy level on Wednesday, with the index for fine particulate matter smaller than 2.5 micrometers (PM2.5) hitting hazardously high levels, according to the Environmental Protection Administration (EPA).
Except for the eastern counties of Hualien and Taitung, other parts of Taiwan hit hazardous air quality levels, with most EPA stations in western Taiwan recording the highest level of 10 on the 1-10 PM2.5 index Wednesday morning.
Level 10 on the index represents PM2.5 concentrations of 71 micrograms per cubic meter or above.
The poor air quality was attributed to a cold air mass moving into Taiwan from the northwest that brought with it pollutants from China, according to the EPA.
The air quality is expected to turn better beginning Wednesday afternoon in northern Taiwan but remain poor in central and southern Taiwan for an extended period because of local pollutants from factories and the lack of conditions enabling the pollutants to disperse, the EPA said.
According to the EPA, measurements above level 7 on the PM2.5 index (54 to 58 micrograms per cubic meter) are deemed severe enough to cause tangible discomfort and health problems.
The elderly and those with chronic lung problems or heart disease in affected areas should avoid prolonged or strenuous outdoor physical activity, the EPA advised, urging people to wear facial masks when going out.
People with asthma may also need to use inhalers more often, it said.
In 2005, the World Health Organization set guideline values for PM2.5 particles of 10 micrograms per cubic meter as an annual mean and 25 micrograms per cubic meter as a 24-hour mean to reduce pollution-related deaths.
It warned, however, that PM2.5 concentrations below those levels could still have an adverse affect on average life expectancy.