The Government will buy only printing paper products that carry the Singapore Green Label come September.

Public agencies will also procure only electrical products certified with "high energy efficiency", starting with air-conditioners, refrigerators, televisions and lamps. For example, only air-conditioners rated at least three-ticks will be allowed.

Environment and Water Resources Minister Masagos Zulkifli made this commitment to signal the public sector's efforts to take the lead in encouraging sustainable practices. A Green Label indicates that suppliers practise sustainable forestry management, which helps tackle the root cause of transboundary haze pollution.

Mr Masagos also announced a key measure to tackle local air pollution: All new motorcycles above 200cc will need to comply with the Euro 4 emission standard from Jan 1, 2018. For new motorcycles under or equal to 200cc, the rules apply from Jan 1, 2020.

Motorcycles are significant contributors to carbon monoxide and ozone, Mr Masagos said.

The Euro 4 standard will reduce emissions of hydrocarbons and nitrogen oxides, which form ozone, by an estimated 50 per cent in new motorcycles, compared to Euro 3.

A study of the pollution caused by diesel vehicles in Singapore is also being done, to analyse the impact on public health and the environment. The results will be used to review vehicle emission policies.

MPs Faishal Ibrahim (Nee Soon GRC) and Louis Ng (Nee Soon GRC) asked about ongoing efforts by the National Environment Agency (NEA) to take to task companies responsible for illegal forest fires that caused last year's haze.

Mr Masagos said the NEA has sent Preventive Measures Notices under Singapore's Transboundary Haze Pollution Act to six Indonesia-based companies, asking them to take immediate steps to mitigate fires and prevent a repeat.

Two - PT Bumi Sriwijaya Sentosa and PT Wachyuni Mandira - have responded, and NEA is in touch with them to verify their information.

NEA is also reviewing information from Asia Pulp and Paper on its subsidiaries and steps taken by its Indonesian suppliers to put out fires in their concessions.

A foreign director from one of the four firms that have yet to respond was also recently served with a notice when he was in Singapore, asking him to give information and attend an interview related to the ongoing investigations.

Samantha Boh