March 17, 2011 12:12:39 am
Worsening conditions at the Fukushima Daiichi nuclear power plant in Japan have raised fears that people will be harmed by radiation. But experts say that in terms of public health,the Japanese have already taken precautions that should prevent the accident from becoming another Chernobyl,even if additional radiation is released.
The Japanese government has evacuated people closest to the plant,told others to stay indoors and distributed the drug potassium iodide to protect the thyroid gland from radioactive iodine.
The great tragedy of Chernobyl was an epidemic of thyroid cancer among people exposed to the radiation as children more than 6,000 cases so far,with more expected for many years to come. There is no reason for it to be repeated in Japan.
The epidemic in Chernobyl was preventable and would probably not have happened if people had been told to stop drinking locally produced milk,the most important source of radiation. Cows ate grass contaminated by fallout from the reactors and secreted radioactive iodine in their milk.
The thyroid gland needs iodine and readily takes in the radioactive form,which can cause cancer. Children are especially vulnerable. Potassium iodide pills are meant to flood the thyroid with ordinary iodine in the hope that it will prevent the gland from taking in the radioactive type. The drug may be unnecessary if people avoid drinking the milk,but for most people,there is no harm in taking it. And if radioactive iodine has already started building up in the thyroid,the pills can help get rid of it,said Dr Richard J Vetter,a professor emeritus of biophysics at the Mayo Clinic in Rochester.
There are several ways to tell if someone has been exposed to radiation. A Geiger counter will detect radioactivity outside the body,on clothing,hair and skin. People found to be contaminated should be advised to take a shower,and their clothing should be discarded as hazardous waste,Vetter said.
Another device,a sodium iodide detector,can be held an inch or so from the neck to check for radioactive iodine in the thyroid gland; if it detects any,the person may be given iodide pills.
In photographs from Japan,health workers appear to be screening members of the public with both Geiger counters and sodium iodide detectors.
If there is a suspicion that someone has been exposed to a large dose of radiation,the first test that doctors are likely to perform is a complete blood count,Vetter said. Abnormalities in the count fewer white cells than would be expected,for example can show up within a day or so,and give a ballpark estimate of how bad the exposure was.
In Japan,its unlikely that the public would get a dose of radiation that would decrease blood cells, Vetter said. If anyone got that dose,its people working in the nuclear plants themselves.