Beijing, Rabi'I 7, 1437, Dec 18, 2015, SPA -- Beijing issued a red alert for smog on Friday, urging schools to close and residents to stay indoors for the second time in 10 days, dpa reported. Restrictions begin Saturday and last until Tuesday, the city's emergency management headquarters announced on the Beijing government website. Measures included pausing factory work and restricting road traffic, except electric vehicles. The alert reflects a forecast of three days of PM2.5 - airborne particulate matter 2.5 microns and smaller - levels above 200 micrograms per cubic metre. PM2.5 pollution is fine enough to penetrate deep into the lungs, and is associated with increased risk of heart attack, stroke, lung cancer and asthma. The World Health Organization's recommended safe maximum is 25 micrograms. --SPA 10:41 LOCAL TIME 07:41 GMT www.spa.gov.sa/w