Households can register for free PM2.5 testing in their homes, which will take place for 10,000 local families to study indoor PM2.5 and its effects with other common indoor pollutants like formaldehyde and benzene, the Shanghai Environmental Protection Industry Association said yesterday.

Shanghai Environmental Protection Bureau will officially start using the PM2.5 gauge for reporting daily air pollution in June. [Xinhua]

Before August 31, interested people can call the association's hotline 5115 7376 or register at its website, www.shaepi.org.cn or www.51157376.com.

Qian Hua of the Shanghai Academy of Environmental Sciences said indoor PM2.5 comes from pollutants such as kitchen smoke and cigarettes.

"Kitchen smoke contains a lot of harmful elements, which enters people's respiratory system," Qian said. "Research has found that people who cook have a much higher incidence of lung cancer and nasopharynx cancer."

Experts said indoor PM2.5 is closely related to outdoor PM2.5 density. "Not opening the window when there is haze reduces PM2.5 pollution at home," he said.

PM2.5 refers to tiny particles measuring 2.5 microns or less in diameter.

It can affect air quality and visibility and poses major health risks as the tiny particles are small enough to lodge deep in the lungs and even enter the bloodstream, causing premature death and chronic diseases.

While the Shanghai Environmental Protection Bureau said it will officially start using the PM2.5 gauge for reporting daily air pollution in June, experts suggest the authority announce the figure multiple times a day, instead of just once, to help local residents take effective countermeasures.