Alarmed by signs of potential radiation effects, baggage handlers at Hong Kong International Airport are demanding annual health checkups and a full investigation to ensure their work environment is free of radiation hazards.

The handlers, who work below the baggage carousels, have complained of increasing headaches, hair loss and sick days since the airport began using a radio frequency identification (RFID) system to direct baggage in 2005.

The workers, citing anecdotal evidence, fear that prolonged exposure to radiation on a daily basis could increase their susceptibility to cancer.

Chow Siu-sung, general secretary of the Airport Air Freight Employees' Association, says he has nearly 1,000 signatures on a petition demanding that the Airport Authority Hong Kong pay more attention to worker safety.

One of the workers, surnamed Ng, said he has suffered from increasingly frequent headaches since the new system was implemented.

He added that a colleague had developed leukemia, though doctors have been unable to link the cancer to prolonged radiation exposure.

According to Ng, who has been handling baggage for more than 10 years, a number of large scanning machines hang above the place where the handlers worked during their 9-hour days.

"It is like having giant scanners shooting radiation at us from all angles, day after day," he said.

Chow said that he enquired in November about the system's safety with Hong Kong Airport Services - the joint venture between Cathay Pacific Airways and Dragonair that employs the workers.

But Chow said he has yet to receive a reply.

Responding to a press inquiry, Jon Conway, that company's director and general manager, said it would follow up with an investigation on workplace safety.

But he pointed out that only 1.11 percent of workers took sick leave last year, which was down from 1.59 percent in 2005.

An employee for the Airport Authority Hong Kong said that it has yet to receive any complaints from workers, but would look further into the matter.

The employee also noted that a 2004 study conducted by researchers at City University of Hong Kong found that the RFID technology's effect on human beings was 30 times less than the radiation caused by mobile phones, and well below internationally accepted standards.

Edward Yung Kai-ning, director of the Wireless Communications Research Center at City University, said that researchers had visited the airport last week to take samples, and found the radiation levels low.

The Labour Department said it is concerned about the situation, and would send people to investigate further.

Hong Kong International Airport handles an average of 1.6 million pieces of luggage every month, and spent about HK$50 million in 2005 to introduce the RFID system.

Previously, baggage sorting was conducted by hand - using bar codes - a more cumbersome system that was prone to errors.