Nuclear radiation bombards us every day of our lives. Some comes from natural sources and some comes from human activity.
Natural sources include cosmic radiation from space, unstable atomic nuclei produced by interactions of cosmic radiation with atoms in the atmosphere and radioactive decay of natural nuclides in Earth’s crust.
Artificial radiation comes from medical procedures, commercial products, fallout from nuclear tests and radiation accidentally leaked into the environment.
Beliefs about the dangers of low-level radiation span a broad continuum. At one end are those who believe there is an international conspiracy to hide its dangers from the public. At the other end are those who say it is an essential soup that is necessary for life and may help to limit cancer deaths.
There are two kinds of health effects from exposure to radiation. Direct, deterministic effects such as hair loss, skin burns, nausea or death occur soon after large direct doses. Stochastic effects are long-term effects, such as cancer.
An internal dose comes from ingesting or inhaling radioactive material. Internal exposure continues until the radioactive material is flushed from the body by natural processes or decays radioactively.
The external exposure stops when the person leaves the area of the source, and neither external nor internal doses can create additional radioactive substances.
Direct radiation is never a significant impact to public health. Normal radioisotope concentrations are millions of times too small for a direct dosage from the soil and water.
Stochastic effects, on the other hand, come from dispersal of radioisotopes into the environment and the subsequent ingestion or inhalation of those isotopes, which might spend a significant residence time in the body and cause various health effects.
From that perspective radioactive material essentially behaves the same as any other toxin. Once inside the body, it causes various forms of chemical damage in proportion to the amount ingested. Yet we visualize germs and chemicals as "soft" while radiation is "hard." There need be no great mystique about radiation. It is no worse than any other kind of poison.
Concerns about radiation from Fukushima are real but overstated and sensationalized.
Populations exposed to radiation doses above 100 millisieverts have a higher risk of contracting cancers of all kinds, according to the World Health Organization. The average annual dose from natural background radiation is about 2.4 millisieverts globally, with a range of 1-10 millisieverts.
Although one small area close to the power plant may have received more than 100 millisieverts, in the rest of Fukushima prefecture, WHO estimated the dose to be within the range of 1-10 millisieverts, while effective doses in most of Japan were put at just 0.1-1 millisievert.
In the rest of the world — including neighboring Indonesia, the Philippines, South Korea, far eastern parts of Russia and Southeast Asia — doses were 0.01 millisievert or less, about as much as half a chest X-ray.
A report from WHO in July will assess the prospect for long-term increases in cancer cases.
Radiation disasters are horrible, but so are oil spills and the other deleterious effects of petroleum, including the hazardous and toxic industrial chemicals made from it.
Richard Brill is a professor of science at Honolulu Community College. Email questions and comments to rickb@hcc.hawaii.edu.
