The watchdog tested eight models of such portable devices - priced between HK$220 and HK$1,480, made in China and Korea - and found six to pose moderate to high risks for eyes and skin.

The council rated three handheld models and one box model as "high risk" when assessing their UV radiation hazard level to eyes and skin at 200 millimeters distance.

"High risk means that burns and injuries to the skin and eyes may result from a short period of exposure to the UV emitted," said the chairman of the council's research and testing committee, Nora Tam Fung-yee.

The three handheld models are "UVC LED Handheld Sterilizer X5" by 59S, "VRAY VR-03-KKY" by Prime Tech and "UV-C Pen QU3" by Momax.

The high-risk rated box model is "All-in-One UV-C Sanitizer Pad Pro ATPM02WH" by Amazing Thing.

The permissible time of exposure of those four ranged from 30 seconds to 12.8 minutes at a distance of 200 mm from the devices.

"The actual hazard posed by excessive UV exposure is determined by its wavelength, intensity, distance and time of exposure," Tam said. "The closer the distance to the devices, the shorter the permissible time."

The two models of portable devices rated at moderate risk may cause painful eyes, tears, or thermal discomfort.

Prolonged or high-dose exposure to UVC radiation can increase the risk of cataracts and skin cancer.

Consumers are advised to keep a safe distance from the light and not to stare at it. Children and pets should stay away from UV disinfection devices to avoid accidents.

In a follow-up, customs seized three models after receiving referrals that those devices might carry the risk of emitting excessive irradiance of UV radiation.

The department has seized 83 pieces of the three models found from a shop in Tsim Sha Tsui and another retailer's office in Kwun Tong.