How much is a low radiation dose? Experts have debated this for a long time, and even now the matter isn’t quite settled. The report issued by the United States’ National Academy of Science in 2006 proposed that low doses refer to doses below 100mSv, and most experts accept this.
According to the figure on the previous page, this radiation dose is the boundary at which acute radiation syndrome appears. You won’t get acute radiation syndrome if exposed to less than this dose; therefore, it is called the threshold dose for acute radiation syndrome.
People exposed to low radiation doses are those who are exposed to radiation at work such as in uranium mines, nuclear power plants and hospital laboratories. This kind of radiation exposure is called ‘occupational exposure’. The safety regulations for occupational exposure state exposure should not exceed 50mSv per year and should not exceed 100mSv over five years.
In addition, there is exposure to radiation by X-ray in hospitals. This is called ‘medical exposure’ but there are no regulations for this type of exposure. Japan has more medical exposure cases than anywhere in the world. It is estimated that nearly 10,000 people a year get cancer because of this.
There are reports that children living near nuclear power plants are more susceptible to leukemia due to radioactive materials discharged from plants. Hence nuclear power plant emissions are regulated to ensure the public are not exposed to more than 1mSv per year.
Living things don’t feel radiation. So why and how does radiation do harm? It is because radiation destroys an important mechanism that links life to life. Please see the next page.