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SINGAPORE \u2013 The air quality in Singapore improved overnight as the hourly PM2.5 readings returned to \u201cnormal\u201d for all regions and the 24-hour PSI levels stood in the \u201cgood to moderate\u201d range for most regions.<\/p>\n
At 6am on Oct 22, the one-hour PM2.5 were 38 in the north, 40 in the south, 37 in the east, 36 in the west and 32 in the central region.<\/p>\n
The readings have been in the \u201cnormal\u201d range for all five regions since 1am.<\/p>\n
The hourly PM2.5 readings are measured in micrograms per cubic metre and are a gauge of the current air quality.<\/p>\n
Scores from zero to 55 represent normal values, those between 56 and 150 indicate an elevated concentration of fine particles, readings between 151 and 250 are considered high, and scores above 251 are classified as very high.<\/p>\n
For healthy people, short-term exposure to high levels of haze particles may cause irritation of the eyes, nose, and throat.<\/p>\n
Haze particles can also affect the heart and lungs, especially in people who already have chronic heart or lung disease, such as asthma, chronic obstructive pulmonary disease, or heart failure.<\/p>\n