More people are risking health problems by staying in the office longer or taking part in indoor activities to avoid the summer heat, a health official has said.

Poorly cleaned air conditioners have been found to be a major cause of health problems for most Chinese people, he said.

Dai Changfang, director of the public health department of the Guangdong center for disease control and prevention (CDC), said yesterday that ever since a recent national inspection found that more than 99 percent of central air-conditioning units are not cleaned regularly, the Guangdong CDC has been applying for approval from the State CDC to conduct a province-wide inspection and cleaning campaign.

Dai said he did not know how many central air-conditioning units were in Guangdong, but the number was likely close to that of Beijing and Shanghai.

The national inspection found there are about 5 million central air-conditioning units. Only 100 in Beijing and 200 in Shanghai are regularly cleaned.

"Dirty central air conditioners contain a lot of viruses. Some people have even found dead mice in them," Dai said.

He said Guangdong has never conducted a province-wide inspection to date, since it needs approval from the State CDC. Applicants are required to have proper equipment and qualified staff.

"We certainly hope to gain approval as soon as possible," Dai said.

Up to now, only the CDCs of Shanghai, Jiangsu and Tianjin have been approved.

"As soon as we get the nod, we will send staff to inspect and clean central air-conditioning units throughout the province, as well as commission eligible private cleaning companies to do the job," Dai said.

The Guangdong CDC, in the meantime, has conducted spot-checks on 33 public buildings which installed central air-conditioning units last month, 42 percent were found to contain legionella.

Legionella is a dangerous virus spread through the ventilation systems of air conditioners. People who contract the virus, suffer from fever, chest pains and experience difficulty breathing. The death rate from the virus is more than 30 percent.

"Office workers constitute the majority of the victims as they spend many more hours a day indoors than other people," Dai said.

Du Ping, an office worker in Guangzhou, suffers from rhinitis. She said she often sneezes and coughs while at work. She suspects the central air-conditioning unit in her office is to blame.

China Central Television's program Weekly Quality Report recently revealed that more than 40 national-level athletes, some of whom are world champions, were hit by flu at the beginning of the year while working out in gymnasiums.

An investigation found the central air-conditioning units were the cause of the virus.

(China Daily May 23, 2007)