Most parts of Taiwan have recorded a high level of PM2.5 air particles on Wednesday, the island's environment department said.

At 5 p.m. Wednesday, the reading of PM 2.5, airborne particles measuring less than 2.5 microns, was 76 micrograms per cubic meter in downtown Taipei, the highest of the island's ten-scale index, according to the department's air quality monitoring chart.

In Taiwan, readings above 70 micrograms per cubic meter are considered "extremely high," while readings between 54 and 70 are considered "high."

The readings along the island's west coast, where major cities like Taichung, Tainan and Kaohsiung are located, all reached the highest level on the index.

Air quality in central and eastern parts of the island was better but only one monitoring location recorded a low 36 PM2.5 reading.

The department suggested residents stay indoors, especially seniors, children and adults with heart and respiratory diseases.