New warning on health risks of low levels of X-ray radiation

Low doses of radiation may lead to a heart attack or stroke and it could have implications for patients undergoing X-rays, warn scientists.

An increased risk of circulatory diseases has been linked to nuclear workers for years- even though it has not been proven biologically.

Now a study of more than 22,000 nuclear staff in Russia shows almost four in ten developed high blood pressure.

This is more than the rate among Japanese survivors of the atomic bomb at the end of World War II.

The condition, known medically as hypertension, can to lead to a heart attack, stroke, heart failure and other serious health problems.

Cancer is the illness most commonly associated with exposure to radiation by doctors and scientists.

Lead author Dr Tamara Azizova, of the Southern Urals Biophysics Institute, Russia, said: “We believe an estimate of the detrimental health consequences of radiation exposure should also include non cancer health outcomes.

“We now have evidence suggesting radiation exposure may also lead to increased risks of hypertension, cardiovascular disease and cerebrovascular disease, as well.”

She pointed out in recent years, the number of people exposed to radiation in everyday life, such as during diagnostic procedures, has increased.

Dr Azizova said: “It is necessary to inform the public that not only high doses of radiation, but low to moderate doses also increase the risk of hypertension and other circulatory system diseases, which today contribute significantly to death and disability.

“As a result, all radiological protection principles and dose limits should be strictly followed for workers and the general public.”

The study published in the journal Hypertension followed employees at Russia’s biggest nuclear weapons factory in Mayak hired between 1948 and 1982.

Their careers lasted an average of 18 years, with half being there for more than a decade.

All the participants had comprehensive annual health check-ups and screening tests with advanced evaluations every five years.

The data included age, smoking history, alcohol consumption and BMI (body mass index).

An analysis of these records up to 2013 found more than 8,400 (38%) were diagnosed with high blood pressure – a systolic and diastolic reading of 140 and 90 mm Hg, respectively.

The former is the maximum pressure the heart exerts while beating and the latter the amount in the arteries between beats.

Hypertension was significantly linked to the cumulative dose.

To put it in perspective, incidence was higher than after Hiroshima, but lower than for clean-up workers following the Chernobyl nuclear accident.

The differences may be explained by variations in exposure among the three groups, said the researchers.

Following the atomic bombing, the Japanese experienced a single, high-dose exposure of radiation.

The Chernobyl workers were exposed to radiation for a short time period over days and months, while the Mayak staff were chronically exposed to low doses over many years.

The mechanism by which radiation exposure may increase the risk of high blood pressure is still unknown.

Dr Azizova said: “So far, the mechanisms remain unclear, not only for certain cohorts but also for the general population.

“One of the main tasks for the coming decade is to study the mechanisms of hypertension and heart and brain atherosclerosis occurring in people who are – and who were exposed – to radiation.”

A study by Imperial College London ten years ago also suggested low doses of radiation can cause cardiovascular disease.

It found radiation kills chemicals called monocytes, which travel across the arterial wall to mop up a protein called MCP-1.

High levels of MCP-1 are thought to cause the inflammation which leads to cardiovascular disease.

The team’s mathematical model was consistent with the rates of heart disease seen in nuclear workers.

 

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