Haze shrouds Phnom Penh as air quality reaches "very unhealthy" levels in Cambodia's capital, according to air monitoring company IQAir. The country's environment ministry on February 1 called on the public to stop burning waste and to prevent forest fires in response to the deteriorating air quality. The level of PM2.5 pollutants -- cancer-causing microparticles small enough to enter the bloodstream through the lungs -- hit 148 micrograms per cubic metre in Phnom Penh, according to IQAir. A reading above 15 in a 24-hour period is considered unhealthy by the World Health Organization (WHO). IMAGES