Heavily polluted smog returned to haunt China on Friday coinciding with the annual session of the Parliament during which legislators plan to propose several measures including “smog tax” to deal with the problem.

As Beijing, the city of over 22 million people, was enveloped by heavily polluted smog, forecast said the annual sessions of the National People’s Congress (NPC), starting on Saturday and the advisory body Chinese People’s Political Consultative Conference (CPPCC) which started its session on Thursday will be hit by smog.

Both houses have over 2200 members each attending the meetings expected to last for a fortnight.

They have been considering several proposals to curb the levels of smog in China’s top cities which is a major concern of the people.

The Beijing Municipal Environmental Protection Bureau issued a yellow alert for heavy air pollution on on Wednesday night, after the hourly average density of PM2.

5 — airborne particles with a diameter of less than 2.5 micrometres — hit 162 microgrammes per cubic metre, the Ministry of Environmental Protection said on Thursday.

During the smog-wary annual session, several members of the CPPCC proposed measures to curb smog and protect people’s health.

Xu Jiankang, a member of the CPPCC National Committee, proposed the imposition of a “smog tax” on gasoline to encourage the use of new-energy vehicles.

Yang Ying, a member of the Shaanxi Provincial Committee of the CPPCC, also filed a proposal to grant subsidies to those who suffer from hazardous smog when working outdoors, such as sanitation workers and traffic police officers, state run Global Times reported.

Expressing concern several netizens expressed hope on social media to see the same blue skies as at last year’s two sessions, like during last year’s APEC summit.

Factories in Beijing and six neighbouring provinces were shut down to ensure clear skies.

China’s capital was shrouded by air pollution nearly half of 2015 during which Beijing also issued its first—ever red alert against heavy smog that lead to closure of schools and restricted traffic, the Bureau had said in January.

Despite Beijing’s attempts to limit air pollution, the capital saw only 186 days with air quality that met the national standard in 2015.