How radiation can affect health

The blasts at the Fukushima Daiichi plant in Japan have raised fears about the adverse health effects of the fission products, iodine-131 and caesium-137 released from the reactors’ core.



On March 17, the levels of radiation 30 km away from the plant rose from 80 to 170 microsievert (mSv) per hour at one site and from 26 to 95 mSv per hour at another. North-west of the nuclear power plant, the levels were between 3 to 170 mSv. Highest levels were found 30 km from the plant. At reactor 4 of the plant, radiation level as high as 400 mSv per hour was measured.

This is low compared to the radiation levels that people at Chernobyl in Ukraine in 1986 were exposed to. Emergency personnel at the Chernobyl reactor were exposed to radiation as high as 20,000 mSv on the first day.

Adverse effects are still seen at the sight. A study published in February 2011 showed that brain development was impaired in birds living in the contaminated area. Their brain size was reduced by almost five per cent due to the exposure to high levels of radiation. The effect varied amongst species and is expected to affect cognition. High oxidative stress and low levels of antioxidants were to blame.

In humans, epidemiological studies show strong links between radiation and cancer especially that of the thyroid gland. More the exposure, more is the risk. Children and adolescents are more at risk due to deficiency of stable iodine in their bodies. Chernobyl clean-up workers were found to have higher risk of leukaemia and other blood related cancers, cataracts and cardiovascular diseases.

Dose limit for radiation workers averaged over 5 years =100 mSv

Dose limit for members of the general public per year = 1 mSv

Radiation dose after one chest X-ray = 0.2 mSv

Radiation exposure per year due to all natural sources = 2.4 mSv

Lowest level at which any increase in cancer is clearly evident = 100 mSv/yr

Criterion for relocating people after Chernobyl accident = 350 mSv

Temporary radiation sickness such as nausea and decreased white blood cell count = 1,000 mSv

Q&A

Does short term exposure to nuclear radiation cause adverse health effects?

Exposure to one sievert of radiation can cause nausea, diarrhoea, headaches and fever. Higher levels of exposure can cause damage to internal organs along with the above symptoms. Exposure to four sievert is generally fatal.

Can radiation sickness be treated?

To an extent. Drugs like potassium iodide help increase production of white blood-cells which reduces damage to the immune-system. Potassium iodide saturates the thyroid gland and blocks the absorption of carcinogenic radioactive iodine.

How does radiation harm the body?

Ionising radiation produced by decaying radioactive material affect the body’s chemistry. Bone marrow cells, thyroid gland, soft tissue of the stomach and lungs are very susceptible to the radiation. For example, the thyroid gland can absorb the reactive iodine produced during the breakdown of radioactive material. Food exposed to radiation is also harmful.

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