PM2.5 concentration highest in Yunlin County last year: Gov't data

Taipei, March 24 (CNA) Yunlin County ranked first in Taiwan for annual average concentration of particulate matter smaller than 2.5 micrometers (PM2.5) in 2023, according to data from the Ministry of Environment (MOENV).

The southern Taiwan county recorded an average PM2.5 concentration of 19.3 micrograms per cubic meter (µg/m³), followed by nearby Chiayi County and Chiayi City, as well as outlying Kinmen, all at 18.8 µg/m³, the data showed.

Taiwan is hoping to keep its annual average PM2.5 level under 13 µg/m³ and the annual average PM2.5 concentration in central and southern Taiwan under 15 µg/m³ by 2027, according to the ministry.

Chang Shun-chin (張順欽), head of the MOENV's Department of Atmospheric Environment, explained to CNA that a higher PM 2.5 level in central and southern Taiwan was mainly a result of less rain and low wind speeds there.

Those conditions led to particulate matter not being able to diffuse into the air, resulting in the local accumulation of pollutants, Chang said.

In terms of the annual average concentration of nitrogen dioxide (NO2), data showed that Taipei led the nation with 13.87 parts per billion (ppb), followed by Kaohsiung at 11.49 ppb.

Areas such as New Taipei, Taoyuan, Hsinchu City and Taichung also recorded relatively high levels.

The situation had much to do with mobile sources of pollution and topography, Chang said.

In Taipei, for instance, a high number of vehicles, coupled with its basin topography and poor dispersion, resulted in relatively higher NO2 concentrations.

Additionally, since NO2 serves as a precursor to ozone, the overall ozone concentrations in the western part of Taiwan -- where those cities are situated -- are also higher than those in the east, the official said.

The MOENV data also showed the status of other major pollutants, such as particulate matter smaller than 10 micrometers (PM10), whose annual average was highest in Yunlin County (41.5 µg/m³), followed by Changhua County (40.8 µg/m³), and Chiayi County (40.2 µg/m³).

However, all these values were below the annual average of 50 µg/m³ set by the ministry.