Beijing raised its air pollution alert to orange, the second-highest level, triggering limits on some industrial production as smog enveloped northern China for a second day.

The concentration of PM2.5, fine particulates that pose the greatest risk to human health, was 359 micrograms per cubic meter at 11 a.m. nearTiananmen Square in Beijing, the Beijing Municipal Environmental Monitoring Center saidon its website. The WHO recommends 24-hour exposure to PM2.5 at concentrations no higher than 25.

Under the orange alert, people are advised to cut down on outdoor activity, while the elderly and people with heart and lung ailments should stay inside. It was an upgrade from yesterday’s yellowalert, which called for measures such as increased road cleaning and spraying of water at construction sites, according to the Beijing Meteorological Bureau.

Reduced visibility led traffic authorities to close several highways out of Beijing, the official Xinhua News Agency said. The smog is partly the result of farmers burning stalks on their land after the autumn harvest, Xinhua said, citing the environmental protection bureau of Henan province.

Beijing is planning to impose pollution-control measures next month, similar to those enacted ahead of the 2008 Olympics, when leaders of the Asia-Pacific Economic Cooperation forum gather in the city for an annual summit. In August, the city ordered vehicles off the road to ensure clear skies for an APEC preparation meeting.

The city last month said it has fined hundreds of companies more than $2 million in the first six months of its stepped-up anti-air–pollution campaign.

Beijing’s monitoring center forecasts the pollution will remain heavy until Saturday. Seven cities out of 11 monitored by Hebei province, which surrounds the capital, saw severe pollution today, data from the provincial monitoring center showed.

via Beijing Raises Smog Alert as Pollution Envelops North China – Bloomberg.