An Overview of Radiation
Nuclear radiation is known for both, its benefits as well as the destructive potential. It is used in x-ray machines, nuclear power plants, some types of sterilization equipment, and also in nuclear weapons.
Radiation emitted by natural and man made sources, which is always present in the environment, is called background radiation. Natural elements are the main contributors, while man made sources account for 3% of the background radiation. Natural sources of radiation are present on earth, in space and atmosphere. For instance, food and water on earth; cosmic rays in space and radon gas in the atmosphere. Nuclear weapons testing, nuclear fuel processing, and nuclear medicines are examples of man made sources of radiation.
On an average, human beings are exposed to a background radiation level of about 2.4 millisievert (mSv) worldwide. Natural background radiation levels vary according to the area. The areas with significantly higher levels include Ramsar (Iran), Gaurapatri (Brazil), Kerala (India), Northern Flinders Ranges (Australia) and Yangiang (China). However, background radiation from natural sources generally does not cause any harmful effects in humans.
Harmful radiation levels
Radiation dose as low as 0.35 Sv can cause acute radiation syndrome characterized by headaches, nausea, vomiting, fatigue, fever and temporary skin reddening. Higher doses can cause radiation sickness, which may have hematopoietic, gastrointestinal or neurovascular presentation. Radiation levels of around 6-10 Sv can cause gastrointestinal presentation, while neurovascular presentation is caused by dose of about 10 Sv.
A radiation level as low as 50 mSv can cause cancer in adults. Incidence of fatal cancer, which is normally 25%, is increased to 30% on exposure to radiation levels above 1000mSv.
Treatment of radiation sickness
Prevention of further radioactive contamination, pacification of symptoms and management of organ damage and pain are the main aims of radiation treatment. Decontamination, which aims to get rid of external radioactive particles to the greatest extent possible, is the first line of action for treatment of radiation sickness.
Treatment for internal contamination differs according the specific type of radiation to which a person is exposed. Potassium iodide, Prussian blue and DTPA (Diethylenetriamine pentaacetic acid) are used for treatment of internal contamination. Supportive treatment to counter symptoms like headache, fever, bacterial infections, diarrhea, nausea and vomiting may be required.
Radiation levels in the US
Based on the ERD (Environmental Radiation Data) from 2009, the top ten states in the US with the highest levels of gross beta in airborne particulates, which is a good indicator of radiation, were: Arizona, Pennsylvania, Kansas, Tennessee, South Dakota, Missouri, California, West Virginia, New Mexico and Nebraska.
The levels of gross beta in airborne particulates in the cities of Phoenix (Arizona), Philadelphia (Pennsylvania), Kansas city (Kansas) and Oak Ridge (Tennessee) were around 0.018 pCi/m3, in Rapid city (South Dakota), Jefferson city (Missouri) and San Bernardo city (California) around 0.017 pCi/m3, while the levels in Charleston (West Virginia), Carlsbad (New Mexico) and Omaha (Nebraska) were close to 0.015 pCi/m3.
Major radiation disasters
The 1986, nuclear reactor accident at a power station in Chernobyl, Ukraine, was one of the worst in the history of mankind. Prior to evacuation, the inhalation dose for people in the vicinity of the accident was around 3-150 mSv. The accident resulted in 32 immediate deaths, 30 were caused by radiation and 2 by the fire. About 116,000 people living in30 km radius around the plant, now what is called the zone of alienation, had to be relocated. However, the effect of radiation was not confined to this area, spreading as far as countries like Germany and France.
The 9.0 magnitude earthquake and the resulting tsunami that hit Japan on 11th March 2011 also caused radiation leak from the Fukushima Dai-ichi nuclear plant. In a recent address, Prime Minister Naoto Kan asked people staying in 20 km radius of the plant to evacuate and those between 20 and 30 km radius to stay indoors. Efforts to contain damage and prevent contamination are being made.