On Thursday, traces of radioactive iodine 131 were detected for the first time in Taiwan since Japans nuclear disaster broke out three weeks ago. But the radiation levels found were extremely low, at less than 0.1% of a typical chest X-ray, and therefore pose no risk to human health.

Low levels of iodine 131 have been found on the vegetable and fruit. The minor radioactive substance can be rinsed off from leaves and vegetables using water.

According to the Atomic Energy Council, Taiwan has found low levels of radioactive iodine 131 from Japan's stricken Fukushima nuclear plant in air samples from the island.

But doctors urge the public to stay calm as the half-life of iodine-131 is 8 days and the amount detected is a lot lower than what we get from X-ray for medical purposes.

The isotope tends to kill thyroid tissues, with a single dosage ranging from 30, 50, 100 to even 200 mSv.

For medical staff, the safety value of the isotope they receive each year is no more than 100 mSv.

Doctors say, based on the current amount of iodine-131 detected in the atmosphere, one would need to be exposed in tens of thousands of times to get enough radiation level, equivalent to that from a X-ray.

They advise people not to take potassium iodine pills to protect against radiation and suggest people to live their lives as they usually do.