Radiation exposure: Background radiation high in Kerala, but no risk, says study

Source: The post is based on the article “Background radiation high in Kerala, but no risk, says study” published in The Hindu on 20th March 2023.

What is the News?

A pan India survey of Bhabha Atomic Research Centre (BARC) on background radiation levels has been released recently.

What are the sources of radiation?

Radiation results from the disintegrating nucleus of an unstable element. These can be from anywhere, including inside human bodies, constituents of matter, natural sources such as rocks, sand or mountains. Gamma rays are a kind of radiation that can pass unobstructed through matter. Though extremely energetic, they are harmless unless present in large concentrated doses.

What is the prescribed amount of radiation exposure?

The International Atomic Energy Agency (IAEA) specifies maximum radiation exposure levels. Accordingly, Public radiation exposure should not exceed 1 milli­Sievert every year. For those who work in plants or are by virtue of their occupation, the exposure shouldn’t be over 30 milli­Sievert every year.

Note: Sievert, Gray, and Rem are different scales to measure radiation exposure. Gray refers to radiation emitted. Sievert and rem refer to biological exposure to radiation. 1 Gray is equivalent to 1 Sievert and 1 rem is equivalent to one-hundredth of a sievert.

The IAEA level has also been adopted in India. Accordingly, gamma radiation levels are monitored around nuclear plants and also the average quantity of radiation that plant workers are exposed.

What are the findings of BARC study on radiation exposure?

The average natural background level of gamma radiation in India was 94 nGy/hr (nano Gray per hour) (or roughly 0.8 milli sievert/year). The last such study was conducted in 1986 and computed such radiation to be 89 nGy/hr.

High radiation exposure in Kerala: The 1986 study measured the highest radiation exposure at Chavara, Kerala (3002 nGy/hr). The present study found that the levels in Kollam district (where Chavara is situated) were 9,562 nGy/hr, or about three times more. This is about 70 milliGray a year, or a little more than what a worker in a nuclear plant is exposed to.

Reason for high exposure: The presence of granite and basaltic, volcanic rock have led to higher levels of radiation from uranium deposits in southern India.

The higher radiation levels in Kollam are attributed to monazite sands that are high in thorium.

No harm with high exposure in Kerala: Extensive studies in the past have checked for higher rates of cancer or mortality in Kerala but found no evidence associated with high radiation levels.