Radiation from the Fukushima nuclear plant in Japan will unlikely affect Hong Kong via air or sea currents, Hong Kong's Secretary for Food and Health York Chow said Wednesday.

Chow said Hong Kong's radiation level was within normal limits and was not hazardous to citizens.

"We will for now focus more on imports of Japanese products that may be contaminated, particularly food. We will continue the monitoring as well as the daily testing of all the targeted products, for example all the food imported from Japan. If we detect anything, we will ensure it will not go on the market," he told reporters.

Chow added testing would continue until it was confirmed there was no further risk.

Also in the day, Hong Kong Observatory Director Lee Boon-ying said easterly to northeasterly winds are expected to continue to trigger artificial radionuclide iodine-131 readings in Hong Kong over the next three days.

But the minute level will not pose health risks, he told a press conference.

The outgoing director said trace amounts of the radionuclide have been recorded in Hong Kong's atmosphere since the weekend. The observatory has increased the frequency of air sampling to once a day to monitor the situation.

Lee said the sampling process takes 22 hours. As last Saturday was the first time the radionuclide had been recorded in Hong Kong, the measurement had to be repeated to re-confirm the results, which were confirmed and announced on Tuesday.

From now on, no more repeat measurements will be required, he said, adding the collection and testing process will take one day.

The observatory's Acting Assistant Director Ma Wai-man said the level detected was so low people would have to inhale it for 500 years to experience the equivalent radiation of a single X-ray.

Responding to news reports claiming a trace amount of plutonium would be fatal to the world's entire population, Senior Physicist of the Department of Health Cheng Kit Man said the International Agency for Research on Cancer has not listed plutonium as a cancer-causing substance and a tiny amount would not be hazardous to health.

Since Hong Kong is 3,000 km away from Japan's Fukushima Prefecture, it would be highly unlikely plutonium would reach Hong Kong by air, said Cheng.

A trace amount of plutonium can be found in local seabed mud and shoals from nuclear tests conducted elsewhere from the 1950s to 1970s, but the effect on human is minimal, Lee added.