The earthquake and tsunami on March 11, 2011 in Japan, has led to worries growing over the radiation leak at the Fukushima Daiichi nuclear power plant. There have been concerns over the health effects of radiation exposure. The questions raised here are, how much radiation can damage health or what are the consequences of radiation exposure.
The optimum levelsNatural radiation exposure for a common man is 0.2 to 0.3 milliSieverts (mSv) per year. This comes from cosmic radiation, possible emissions from building materials and natural radioactive substances in the environment. According to the BARC scientists, the dose limit of radiation exposure for public is one mSv per year and for occupational workers is 20 mSv per year.
Dr Susan Langhorst, assistant professor, Department of Radiology, radiation safety officer at Washington University in Saint Louis, USA, avers that it is the responsibility of medical professionals to weigh the risks and benefits of radiation used in diagnostics and treatment. However, as per the US Nuclear Regulatory Commission reports, people undergoing medical radiation as in X-rays, CT scans and MRI scans etc there is no exposure limit.
Exposure – health effects
The health effects caused by radiation exposure depend on its level, type and duration. An acute very high single dose of radiation is much more harmful than accumulated radiation exposure over time. Health physicians and safety experts at BARC reveal that acute (high) radiation exposure may cause radiation burns, loss of hair and nausea and vomiting. However, nausea and vomiting can be initiated by other reasons including anxiety. In addition, US Centres for Disease Control and Prevention report diarrhoea followed by fever, fatigue, loss of appetite, gastrointestinal problems as symptoms, which can last for long.
The health effects caused by radiation exposure depend on its level, type and duration. An acute very high single dose of radiation is much more harmful than accumulated radiation exposure over time. Health physicians and safety experts at BARC reveal that acute (high) radiation exposure may cause radiation burns, loss of hair and nausea and vomiting. However, nausea and vomiting can be initiated by other reasons including anxiety. In addition, US Centres for Disease Control and Prevention report diarrhoea followed by fever, fatigue, loss of appetite, gastrointestinal problems as symptoms, which can last for long.
As per the World Nuclear Association, London, UK figures, single one mSv dose of radiation may cause transient radiation sickness and lower the white blood cell count but is not lethal. Fortunately, acute radiation sickness usually sets in only after a whole-body dose of three mSv, which is almost 3,000 times the recommended public dose limit per year.
The long-term effects of low-dose radiation are difficult to estimate. Researchers have reported DNA damage from ionizing radiation such as X-rays and gamma rays, which can cause mutations resulting in cancer of gastrointestinal tract, reproductive system and bone marrow. However, the risk may be very small and studies in a large exposed group are unavailable.
Diagnostic techniques
Several diagnostic techniques such as X –rays, CT scan, MRI, PET scan etc use radioactive materials. In some procedures, tracers are used, which emit gamma rays from within the body. These tracers are generally short-lived radioactive isotopes linked to chemical compounds that are used for certain tests. They can be given by injection, inhalation or orally. The mean effective dose of radiation is 4.6 mSv per diagnostic procedure as reported by the World Nuclear Association.
Several diagnostic techniques such as X –rays, CT scan, MRI, PET scan etc use radioactive materials. In some procedures, tracers are used, which emit gamma rays from within the body. These tracers are generally short-lived radioactive isotopes linked to chemical compounds that are used for certain tests. They can be given by injection, inhalation or orally. The mean effective dose of radiation is 4.6 mSv per diagnostic procedure as reported by the World Nuclear Association.
Explains Mumbai-based practicing radiologist Dr Srirang Rane, “When it comes to radiation exposure, professionals who frequently work with radioactive materials, whether in a hospital or a nuclear power plant, abide by the ALARA principle - as low as reasonably achievable. Radiation exposure limits are conservatively set well below the levels known to induce radiation sickness or suspected of causing long-term health effects. Temporary exposure to dosages many times these limits, however, is not necessarily dangerous.”
Dr SB Grover and his colleagues from Department of Radiology, Vardhaman Mahavir Medical College and Safdarjang Hospital, New Delhi, says, “There are various Regulatory Bodies at the international and National level, which lay down norms for radiation protection. These are the International Commission for Radiation Protection (ICRP) the National Commission for Radiation Protection (NCRP) in the US and the Atomic Energy Regulatory Board (AERB) in India.”
“Enough aluminium shielding is done for radiation protection. There is no reason for worry. For pregnant women, we avoid an X-ray during the first trimester and if an X-ray is required later, we shield the abdomen”, says Dr Rane.
