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SINGAPORE: The hazy conditions present in Singapore since early Wednesday morning was due to an "accumulation of particulate matter", the National Environment Agency (NEA) said, as air quality edged into the "unhealthy" range in the eastern part of the country at about 11am, before readings in the south rose in the evening.

As of 7pm, the 24-hour PSI reading in the south was 105. The rest of the readings were:



92 in the north

98 in the east

90 in the west

88 in the central region

According to the National Environment Agency (NEA), PSI readings of 50 and below denote “good” air quality, “moderate” for 51-100 and “unhealthy” for 101-200.





"The haziness is taking time to clear as winds have remained light since yesterday evening. However, thunderstorms are expected in the afternoon which should help to improve the situation," the authority said in a Facebook post on Wednesday.



The one-hour PM2.5 reading at 7pm ranged between 34-71 µg/m3. The reading was the highest in the south region, registering at 71µg/m3, which is in the "Elevated" band.

"NEA is monitoring the situation closely and will provide further updates when necessary," the agency added.

PM2.5 is a measure of tiny particles less than 2.5 micrometres in diameter in the air. When the PM2.5 reading is in the elevated range, haze particles can affect the heart and lungs, especially in people who have chronic heart or lung conditions.

According to NEA, one-hour PM2.5 readings are a "good indicator of current air quality", and can be used for those deciding whether to go for immediate outdoor activities, such as a jog.

In September, Singapore experienced several days where the air quality was in the unhealthy range.