The results of an air pollution experiment, which turned a rat's lungs black, have been exaggerated in media reports and the effect on humans will not be so severe, according to research fellows at the Shanghai-based Fudan University, who conducted an experiment relating to cough medicines on rats over six days.

Song Weimin, a professor with the university's School of Public Health, said that in the experiment, which was to test two kinds of cough medicine, the rat was injected with doses of PM2.5 particles (airborne particles measuring less than 2.5 microns in diameter) directly into its lungs. The density of PM2.5 in the experiment was far higher than human beings would encounter, he said.

A report from news website chinanews.com on Monday indicated that smog could turn a normal lung black within six days, and this was an exaggeration, Song said.

The report cited Song as saying that once the PM2.5 particles had caused damage to the rat's lungs, the time and cost required for health treatments would increase significantly and if they turned black there was not likely to be any recovery.

The report even posted several pictures of the experiment, which showed the change in the color of the lungs. The dramatic imagery whipped Net users into a frenzy, given the recent smoggy weather that  blanketed much of the country, and prompted commentary on China's increasing rates of lung cancer.

On November 4, an 8-year-old girl became the country's youngest lung cancer sufferer, the China News Service reported. Doctors linked her condition with high levels of PM2.5 particles.

Li Qiang, a research fellow with the National Office of Tobacco Control, told the Global Times that the PM2.5 particles, which penetrate deep into the lungs, are very harmful to the human respiratory and cardiovascular systems, and long-term exposure to high densities of the particles is likely to cause lung cancer.

"Experts were uncertain about the exact link between lung cancer and exposure to PM2.5 previously, but findings by a World Health Organization (WHO) body released last month proved their relationship," said Li.

On October 17, the International Agency for Research on Cancer (IARC) under the WHO announced that studies showed that outdoor air pollution as well as its major component - particulate matter - are carcinogenic to humans.

The IARC said that there is sufficient evidence that exposure to outdoor air pollution causes lung cancer, which applies to all regions of the world. Although the dangers of smoggy weather to human health have been confirmed by the WHO, some Net users noted that the public should not panic or listen to rumors without applying skepticism.

On Friday, Kan Haidong, another professor of the School of Public Health at Fudan University, denied a rumor that indicated that smog could cause infertility, according to daily health publication Health News.