KUALA LUMPUR — Haze conditions worsened sharply across Malaysia overnight, with 21 areas recording unhealthy air quality as of 8am today, almost double the 11 reported yesterday afternoon.

Johor was the worst-affected state, accounting for eight of the unhealthy readings, according to data from the Air Pollutant Index Management System (APIMS).

Batu Pahat recorded the highest Air Pollutant Index (API) reading nationwide at 188, followed by Kluang at 169, Segamat and Larkin at 166, Pasir Gudang at 165 and Tangkak at 164.

Kota Tinggi recorded an API of 155, while Pengerang stood at 154.

Elsewhere, Nilai in Negeri Sembilan recorded 161 and Seremban 157, while Bandaraya Melaka registered 155.

Balok Baru Kuantan in Pahang recorded an API of 153, Putrajaya 152 and Rompin, also in Pahang, 152.

Unhealthy readings were also recorded at Indera Mahkota Kuantan at 142, Cheras at 140, Kemaman at 134, Batu Muda at 120, Bukit Rambai at 115, Paka at 111 and Jerantut at 102.

The deterioration was not uniform nationwide. IPD Serian in Sarawak and Johan Setia in Selangor, which had recorded unhealthy air quality yesterday afternoon, improved to moderate readings of 98 this morning.

A further 41 areas recorded moderate air quality, while only five stations remained in the good range: Minden in Penang at 45, Kota Kinabalu at 44, Kangar at 35, Langkawi at 29 and Balik Pulau at 23.

The latest readings mark a broad worsening from 4pm yesterday, when 11 areas were classified as unhealthy and 55 as moderate.

Under Malaysia’s API scale, readings between zero and 50 are considered good, 51 to 100 moderate and 101 to 200 unhealthy. Readings of 201 to 300 are classified as very unhealthy, while anything above 300 is deemed hazardous.