NEW YORK (Reuters Health) - As the Japanese government grapples with a deepening crisis at the Fukushima Daiichi nuclear plant, Japanese people are increasingly worried about their potential health risks from exposure to radiation.
The World Health Organization has said the public health risk to Japan is "minimal." Japanese Prime Minister Naoto Kan said "this is fundamentally different from the Chernobyl accident."
Still, the 1986 meltdown at Chernobyl is the best-studied such incident and the most recent nuclear accident that affected a large population. For a look at the health risks Japan could face in the years to come, Reuters Health spoke with scientists who studied the 1986 Chernobyl meltdown.
Unlike the meltdown, explosion, and fires that happened at Chernobyl, radioactivity at Fukushima remains largely contained within the reactor. Currently, Fukushima rates a 4 on the seven-step scale of nuclear incidents, below Three Mile Island in 1979, which rated a 5, resulted in no deaths and had no impact on the incidence of cancer in the region. Chernobyl was a 7.
In the aftermath of Chernobyl, people exposed to radioactive fallout showed higher rates of thyroid cancer because the gland sequesters radioactive iodine, says Dr. Virginia LiVolsi, a surgical pathologist at the University of Pennsylvania, Philadelphia, and a member of the Pathology Review Panel for the Chernobyl Tissue Bank. One study estimated that radiation exposure would raise the number thyroid cancer cases - a rare cancer -- in Belarus by 80 percent over 50 years.
Most scientists attribute the extra risk not to airborne exposure, but to the fact that people kept drinking milk from contaminated areas. The Japanese population is already better protected because of higher levels of dietary iodine, and the government has distributed iodine pills, which will reduce the uptake of radioactive iodine in the air.
Even if the Japanese can avert a full meltdown, the population will still be faced with periodic venting of radioactive steam, which is expected to last months.
The related risks are unclear, experts say, but a growing body of evidence shows that long-term exposure to low level radiation in the air, water, and food poses some risk. Chernobyl studies have found that low level exposures can lead to increases in breast cancer, leukemia, premature aging, strokes, and heart attacks.
There are also concerns about birth defects. A 2005 U.N. report said there was no evidence for an increase in such birth defects following Chernobyl. In 2010, however, Dr. Wladimir Wertelecki, of the University of Southern Alabama in Mobile reported double to triple the normal rate of defects such as spina bifida and conjoined twins - also fairly rare -- in affected regions.
Still, larger reviews and government studies have played down these risks.
"As a whole, there is no good evidence of a clear link of diseases with exposure to low doses," says Vladimir Saenko, an epidemiologist at Nagasaki University in Japan, "Perhaps longer observations will help to gain insights into this problem."