(AGI) Beijing, Dec 2 - Factories have closed in Beijing after afifth day of heavy smog. Chinese authorities ordered more than2,100 factories emitting high levels of prollutants to stopproduction, calling a halt to all building yard operations. Athick greyish-yellow cloud hangs over the city, reducingvisibility to only a couple of dozen metres. The pollutionindicator at the U.S. Embassy showed that particulate matter(PM) measured 588 microgrammes per square metre of air early onWednesday afternoon, one of its highest levels yet. Tinyparticles of PM 2.5 reached more than 400 micrograms per cubicmetre in some of the worst-affected areas, 15 times the levelof 25 microgrammes per cubic metre advised by the World HealthOrganisation. On Sunday the authorities issued an "orangealert", the second highest possible, after the layer of smogintensified, asking children and the elderly to stay at home,as they did on Wednesday. Teams of inspectors from the Ministryfor Environmental Protection have been enforcing therestrictions on businesses causing the greatest environmentalimpact, finding at least 21 instances of law-breaking inBeijing alone. The smog has also affected air traffic, withmore than 30 flights from Beijing and Shanghai cancelled. Manyof these were to the worst-hit parts of the country, such asthe northern Shanxi province. Beijing is also consideringimplementing swinging fines for businesses producing thegreatest pollution. Zhang Guohong, Deputy Director of BeijingMunicipal Commission of Development and Reform, said firmswould be obliged to pay professionals to improve their existingemissions treatment facilities or build new ones in order tocomply with anti-pollution regulations. At the climate changeconference in Paris, China's President Xi Jinping renewedpromises to cut polluting emissions, but stressed the need forindustrialised countries to lead the fight against climatechange, rather than those which, like China, are stilldeveloping countries. (AGI). .