Japan's neighbors say they don't foresee their countries having any immediate effects of radiation from Japan's nuclear crisis.
The Russian Emergencies Ministry said Tuesday it had detected no increase in radiation levels. Far eastern Russia, the Korean peninsula and China are Japan's nearest neighbors.
Jae Moo-sung, a nuclear engineering expert at Seoul's Hanyang University, said wind speed and direction would be the most important factors. He said a full meltdown could spread radioactivity to the Korean peninsula.
The Xinhua News Agency quoted Chinese meteorologists Wednesday saying rain and snow forecast in northern Japan should help prevent any spread.
Singapore said no abnormal changes in radiation levels have been detected. Fake text messages have claimed acid rain could reach the island more than 3,000 miles (5,000 kilometers) southwest of Japan.