Japan nuclear health risks minimal, experts say

Source from: http://www.sfgate.com
Japan's nuclear catastrophe is considered the worst disaster of its kind since the Chernobyl meltdown 25 years ago, but the health hazards are probably minimal at this point even to those living relatively close by, radiation experts said Tuesday.

Concern over possible health risks in Japan has risen in recent days as radiation levels have climbed since the Fukushima Dai-ichi nuclear power plant was damaged by last week's massive earthquake and tsunami.

Radiation levels haven't climbed high enough to cause immediate health problems, which could include symptoms like nausea, vomiting and burns associated with large, one-time bursts of radiation. But the threat from long-term exposure to lower levels of radiation remains a worry, especially for workers inside the nuclear plant. Such exposure could cause cancers and genetic damage decades from now.

"In Japan, this is very serious. And if I were in the area, I'd be moving out of there," said Thomas McKone, an environmental health sciences adjunct professor at UC Berkeley.

Long-term concerns

From what they've seen so far, radiation experts said it's unlikely that anyone outside the plant - including residents in nearby communities who have been evacuated in recent days - has been exposed to enough radiation to do long-term damage.

But with the ongoing nuclear disaster far from contained, the possibility for health issues exists.

"At this point, it's going to be very difficult to measure whether anyone got cancer from this or not," said John Murnane, a radiation oncology professor and chairman of the UCSF Radiation Safety Committee. "It all depends on the dose, and if it stays. People need to keep in mind we're exposed to radiation every day of our lives."

Radiation is a type of energy given off in waves or particles as they move through space. The sun gives off radiation in the form of ultraviolet waves, for example.

Ionizing radiation is a type of especially energetic or aggressive radiation that can be harmful to the body, and that's the type of radiation that is cause for concern in a nuclear incident. Some forms of ionizing radiation can be helpful but still can pose health risks. X-rays or radiation therapy to kill cancer cells come to mind.

Ionizing radiation is dangerous because it can kill cells in large doses, and, in smaller doses, it can do irreparable damage to human DNA, potentially setting off a chain of events that can cause tumors to grow decades later.

Learned from victims

Scientists understand the effects of radiation from studying the victims of the atom bombs dropped on Hiroshima and Nagasaki during World War II. Scientists began measuring the doses received by individuals almost immediately, McKone said, and the survivors have been studied for several decades now.

It was from those victims, and from Chernobyl, that scientists learned that cancer was the primary cause for concern for survivors of major radiation exposure decades later. Leukemia is the most common form of cancer from radiation and the fastest to spread. But the type of cancer depends on the type of radiation.

Radioactive iodine has been detected in the radiation leaked from the Fukushima Dai-ichi nuclear plant. Because the thyroid gland absorbs iodine - whether it's radioactive or not - thyroid cancer is the most pressing concern.

The Japanese government has distributed doses of stable iodine, or potassium iodide, to people who have been evacuated from nearby communities. Potassium iodide works by "filling" the thyroid with healthy iodine before it can absorb the radioactive iodine, but it must be taken before exposure occurs.

Public health and radiation experts stressed Tuesday that there is no need for people in the United States to stockpile potassium iodide tablets, much less take them. Radiation levels high enough to present health risks will not reach the West Coast, public health and radiation experts said.

In Japan, it may be years or decades before the true health and environmental repercussions of the current disaster are fully understood.

"If they get large amounts of materials into the soil, it's not that the people will necessarily get a high dose, but the area will have to be evacuated for years and cleaned up," McKone said. "They may not be at risk for a lot of disease. They may lose their villages and their lands."