Small amounts of radiation thought to come from Japan's crisis-stricken Fukushima nuclear power plant have been detected across Europe.

On Tuesday (29 March), Britain's Health Protection Agency (HPA) said "the minutest" levels of radioactive iodine had been detected at its air monitoring stations in Oxfordshire and Glasgow over the past nine days.

Shipping companies are working on plans to prevent the spread of radioactive material by sea (Photo: Colin Thompson)

It stressed however that the levels were too low to cause any risk to human health, peaking at 300 micro-becquerels per cubic metre but averaging a much lower 11 micro-becquerels over the nine-day period.

"Levels may rise in the coming days and weeks but they will be significantly below any level that could cause harm to public health," the HPA said in a statement.

Similar amounts of radioactive material have been detected in Germany and Switzerland, as workers in Japan continue their struggle to prevent radioactive water from seeping into the sea.

It emerged on Tuesday that seawater near the damaged Fukushima nuclear reactors is more contaminated that previously reported, with water near reactor 1 containing radioactive iodine at 3,355 times the legal limit, according to Japan's nuclear safety agency.

Iodine 131's relatively short half-life of eight days, the time it takes to halve the radiation through natural decay, reduces the likelihood of risk to humans said an official.

"Even considering its concentration in marine life, it will have deteriorated considerably by the time it reaches people," Hidehiko Nishiyama, deputy director-general of Japan's nuclear safety agency said.

In the Ukraine, Iodine 131 was blamed for the high occurrence of thyroid cancer among children exposed to radioactivity after the 1986 Chernobyl nuclear disaster.

Japanese officials are also fighting to prevent more dangerous radioactive liquid seeping into the sea, after small amounts of plutonium were detected in soil at the plant.

Shipping companies are currently working on contingency plans to prevent boats passing near Japan from carrying contaminated materials across the globe.

The 'MOL Presence' was turned away from a Chinese port this week after Geiger counters detected higher-than-normal radiation levels, reports Financial Times Deutschland. Earlier it had passed within 120 miles of Japan's Fukushima plant.

As the global fallout continues to spread, EU leaders meeting in Brussels last week asked the European Commission and the European Nuclear Safety Regulatory Group (Ensreg) to develop the scope and criteria of safety tests to be conducted on European nuclear power plants.

EU energy commissioner Gunther Oettinger earlier this month suggested the tests were likely to look at the risks posed by earthquakes, tsunamis, terrorist attacks and electricity power cuts, among other variables.

It now appears however that France is unwilling to include the risk from terrorist attacks or planes crashing into nuclear power plants.

"If they are included then this can't be called 'lessons learned from Japan,'" Andre-Claude Lacoste, head of the Autorite de Surete Nucleaire, said on Monday. "I will do what I can to keep risks from planes and terrorism out of the audits."

French President Nicolas Sarkozy is set to become the first leader to visit Japan on Thursday since the country experienced a 9.0-magnitude earthquake on 11 March.