Taipei: Continental cold air masses are set to carry overseas pollutants that will bring air quality in Taiwan to an orange alert level, with sensitive groups advised to avoid outdoor activities, according to the Ministry of Environment (MOENV).

According to Focus Taiwan, the ministry advises children, older adults, and people with heart or respiratory conditions to limit outdoor activity, reduce physical exertion, or wear masks when outside under an orange AQI alert. Healthy individuals who experience irritation or coughing should also cut back on outdoor activities, while students are advised to avoid prolonged or intense exercise.

The MOENV stated in a news release that a haze was observed across parts of eastern China from Shandong to Shanghai. As the continental cold air masses move south, the pollutants they bring will affect Taiwan's air quality, pushing it to mostly moderate or orange alert levels. Early morning radiational cooling is likely to allow pollutants to accumulate in southern Taiwan, while additional inflows of overseas pollution later in the day are expected to keep air quality at orange alert levels.

The air quality in central and northern Taiwan is expected to remain poor until Wednesday afternoon before improving, while orange alerts in southern Taiwan could persist through Saturday. Conditions in southern Taiwan are forecast to improve on Sunday as a northeast monsoon strengthens and overseas pollution subsides.

Hourly concentrations of fine particulate matter, or PM2.5, in the Shanghai and Shandong regions - which lie upwind of Taiwan under northeasterly monsoon conditions and are considered key indicators of transboundary pollution - ranged from about 40 to 90 micrograms per cubic meter (µg/m3) and continued to rise. In northern Taiwan, PM2.5 hourly concentrations could reach 25 to 40 µg/m3 on Tuesday afternoon, with PM10 hourly concentrations reaching 50-90 µg/m3. As northeasterly winds shift southward, air quality in most regions is expected to reach orange alert levels.