Canadian and U.S. authorities have both cut back radiation reporting after detecting only minuscule increases following the Fukushima Daiichi nuclear crisis, despite ongoing clean-up efforts in Japan.

"The quantities of radiation reaching Canada are very small and do not pose any health risk to Canadians," said a statement posted by Health Canada online.

"We have seen very slight increases in radiation across the country, smaller than the normal day-to-day fluctuations," said the website.

As a result the daily reporting of radiation levels has been rolled back to weekly reporting by Health Canada.

"Health Canada will change the frequency of publishing the data from all monitoring networks on the website to once a week starting the first week in May," said the website.

Natural Resources Canada also conducted mobile surveys on Vancouver Island and the B.C. mainland in March and April, but also found no significant increase in radiation.

U.S. cuts back testing

South of the border the U.S. Environmental Protection Agency has also ratcheted down that nation's radiation monitoring program for rain, drinking water and milk in response to a consistent drop in the levels of fallout detected.

Numerous radioactive particles have been detected in milk, water and air tests nationwide since the magnitude-9.0 earthquake and tsunami struck the power plant on March 11, but agency officials said Friday the levels were so minuscule they were not harmful to public health.

After seeing the levels drop in recent weeks, EPA cut back to resume sampling water and milk once every three months.

But some critics felt the move was premature given that the world's second-worst nuclear accident is still unfolding.

"Throughout this and other radiation accidents it has always turned out that more radiation was involved than we initially thought," said Ira Helfand, a co-founder of Physicians for Social Responsibility and a physician who practices internal medicine in Springfield, Mass.

"The U.S. should continue to monitor milk and rainwater until we can be sure that the plant is under control and there are no further emissions."

Workers enter damaged reactor

The nuclear crisis began on March 12 when the Daiichi nuclear plant lost its power and cooling systems following the 9.0 magnitude earthquake and tsunami, triggering fires, explosions and radiation leaks.

Radiation leaking from the plant forced 80,000 people living within a 19-kilometre radius to flee their homes, and many still are living in gymnasiums and community centres.

Last week, radiation levels at the damaged reactors dropped enough to allow workers in special protective gear to enter the plant for 25 minutes, but officials are still predicting it will take months to get the reactors fully under control.

In Vienna, International Atomic Energy Agency expert Hartmut Nies also predicted last week that traces of Cesium 134 and Cesium 137 leaking from the plant will be carried by the Pacific's Kuroshio current to the North American coast within two years.

But the detected levels would be "very low" and there were no specific concerns, said Denis Flory, an IAEA deputy director general.

In March the radioactive contamination of seawater around the Fukushima Daiichi nuclear plant in northeastern Japan soared to 1,250 times the normal figure, according to the Japanese Nuclear and Industrial Safety Agency.