Leaders of the World Health Organization say they are concerned about the air quality and health efiects on citizens during a recent outbreak of heavy pollution in Beijing.Still,they said they were unsure of the exact amount the air pollution takes on any person's body,casting doubts on local reports tying the area's dirty air to particular cases of illness.    Speaking at a briefing on Tuesday,the WHO's Western Pacific regional director, Shin Young--Soo,cited reports about poor air quality causing lung cancer in recent weeks. "The WHO is skeptical of the information,"she said."We're cautious of whether the illness is related to air po11ution. We know it has an impact on health,but we don't know how much."     The officials didn't cite particular reports.The comments follow a number of articles since late last year connecting some cases of diseases like lung cancer with pollution,.including one in November regarding an 8-year-old girl.    The health impact of Beijing's gray skies has been on the minds of many over the past week. Local authorities on Tuesday preserved an orange alert the city's second highest pollution-warning level--and again warned people to stay indoors.Experts widely agree that small particulates  known as PM2.5 carry significant short-and long-term health risks,particularly with children.Other studies find a certain link between pollution and shorter life spans.  Chinese state media have noted a rise in cancer levels in Beijing,without specifying  whether the new cases are the main result of pollution,smoking,other sources or some combination. Bernhard Schwartlander,the organization's China chief,said he is concerned and has been in contact with national authorities."There is no easy solution,"Dr. Schwartlainder said,adding that solving the problem requires managing industry and the economy.WHO leaders advised citizens.to stay indoors and limit exposure to the harmful particulates.When asked if wearing a face mask has any proven efficacy in preventing health effects of air pollution,Dr. Schwartlainder said,"Whatever you do,it's better than nothing." What would be the best title of this passage?
The dangers of heavy pollution The impacts of pollution on health The importance of protecting the environment The uncertainty of relationship between pollution and health