As thick smog continues to smother much of the country with moderate to unhealthy levels, the Meteorological Department has issued awarning on haze-induced low visibility of less than five kilometres over the waters off nine states today.

It said in a statement that the affected areas are Kedah, Penang, Perak, Selangor, Negri Sembilan, Malacca, Johor, Pahang and Sarawak, reported Bernama .

"The condition is risky to sea vessels without navigational equipment," it said.

The department also said thunderstorms over the waters off Kuching, Rejang, Mukah, Miri and Bintulu in Sarawak are expected to persist this morning.

It said the accompanying strong winds of up to 50 kmph and high waves of up to 3.5 metres are dangerous to small boats.

According to the Department of Environment website today, Johor, Malacca, Negri Sembilan, Selangor and Kuala Lumpur are experiencing Air Pollutant Index (API) readings in the unhealthy bracket with readings at least from 100 to 140.

Elsewhere the haze is reported to be at moderate API readings except for Kelantan and parts of Sarawak and Sabah, with below 50 readings.

Kelana Jaya MP Wong Chen last week complained that the Department of Environment's (DOE) API standard is far lower than the one used by Singapore and Indonesia, which would result in higher API readings.

Wong urged the DOE to release the higher readings, which he said is already in the department's possession in several stations.

S'pore at unhealthy levels

Meanwhile Bernama also reported the haze persisting in Singapore today despite some improvement yesterday, with the 24-hour pollutant standard index (PSI) remaining in the unhealthy range.

As at 9am today, the 24-hour PSI read 123 to 153, between the mid and high sections of the unhealthy ranges, and the three-hour PSI was 177, according to the National Environment Agency (NEA).

The current hazy conditions are expected to persist with a possibility of some deterioration.

The 24-hr PSI for today is expected to be between the mid and high sections of the unhealthy range, and may enter the low end of the very Unhealthy range if denser haze is blown in.

NEA said visibility today is likely to deteriorate especially in the morning when humidity is high, as moisture has a swelling effect on the haze particles.

Haze worsens through day

Later this afternoon Bernama reported the haze does not appear to be diminishing, with 13 areas recording unhealthy air quality as of this afternoon.

According to the DOE's website, as at 12 noon, another area here, Cheras recorded an API reading of 107, compared to 96 at 9 am today.

The most affected areas are Nilai in Negeri Sembilan (147); Seremban in Negeri Sembilan (143); Port Klang, Selangor (137); Shah Alam, Selangor (134); and Bandaraya Melaka (131) and Bukit Rambai (128) in Melaka.

Other areas are Batu Muda, Kuala Lumpur (123); Putrajaya (123); Petaling Jaya and Banting, Selangor (122 and 118 respectively); Port Dickson, Negeri Sembilan (116); and Pasir Gudang, Johor (110).

The API reading was moderate for 27 areas including Larkin Lama, Muar and Kota Tinggi in Johor (100, 93 and 92, respectively); Balok Baru, Kuantan (90); Seri Manjung, Perak (87); and Seberang Jaya 2, Perai, Penang (85).

Meanwhile, areas that recorded good air quality are Sekolah Menengah Tanjung Chat, Kota Baharu, Kelantan (49); Sandakan, Sabah (47); Sibu, Sarawak (44); and Keningau and Kota Kinabalu in Sabah (39 and 35, respectively).

An API reading of 0 to 50 indicates good air quality; 51 to 100, moderate; 101 to 200, unhealthy; 201 to 300, very unhealthy and 300 and above, hazardous.

The public can obtain updates through apims.doe.gov.my.