Everyday hazards such as inhaling polluted city air or other people's cigarette smoke are potentially worse for your health than being exposed to the radioactive fallout of an atomic bomb, according to new research.

A study of radiation exposure caused by the atomic bombs dropped on Japan in 1945 and the explosion at the Chernobyl nuclear power plant has suggested that they have posed similar or lower health risks to survivors than the more prevalent problems of air pollution, smoking and obesity.

Moving from Inverness to the more polluted streets of Central London could have worse consequences for your health than choosing to live in the contaminated exclusion zone around Chernobyl, the site of the world's worst nuclear disaster.

Millions of people were exposed to potentially dangerous levels of radiation when the former Soviet nuclear power plant in what is now Ukraine, exploded on April 26, 1986. But the latest findings suggest that the consequences of radiation exposure suffered by survivors of the incident or the bombs dropped on Japan during the Second World War may be much less damaging than previously thought.

The atomic bomb explosions at Hiroshima and Nagasaki together killed more than 200,000 people from a combination of blast effects, burns and acute radiation sickness.

Estimates suggest that a lifelong smoker might on average lose ten years of life because of the habit, while someone who is severely obese (defined as a body mass index score of more than 40) at 35 might lose four to ten years.

By contrast, atomic bomb survivors who were exposed to high levels of radiation within 1,500 metres of the hypocentre of a blast could expect their lives to be shortened by an average of 2.6 years, according to research published online today in the BioMed Central journal Public Health. All of the risks studied showed a similar, relatively small increase (about 1 per cent) in mortality rates among a given population.

A 1 per cent increased mortality rate due to radiation exposure equates to a risk of approximately 1 in 100 of contracting a fatal cancer in later life.

The increased risk of dying from heart disease caused by passive smoking if you live with a partner who smokes is estimated to be 1.7 per cent. This compares to a 2.8 per cent increased risk of dying from the adverse effects of the higher air pollution in Central London compared with Inverness.

Jim Smith, of the Centre for Ecology & Hydrology, who carried out the research, said: "It is well known that radiation can potentially cause fatal cancers in people, even at relatively low doses. But our understandable fear of radiation needs to be placed in the context of other risks we encounter in our daily lives.

"The immediate effects of the Hiroshima and Nagasaki atomic bombs led to approximately 210,000 deaths. However, radiation exposures experienced by the most exposed group of survivors led to an average loss of life expectancy significantly lower than that caused by severe obesity or active smoking."

Speaking at a briefing in London yesterday, Dr Smith admitted that his calculations were limited, as they excluded wider social and lifestyle factors, which had a much greater potential impact on health.

"Despite high levels of air pollution, people living in Kensington and Chelsea have the highest life expectancy of anyone in the UK." Dr Smith, who has worked extensively in the Chernobyl exclusion zone, said that the risks of premature death among this group were actually no greater than from being subjected to prolonged passive smoking, or from being obese.

Danger of dying

Average risk of death in any one year from these causes:

1 in 200

Ten cigarettes a day

1 in 300

Heart disease 1 in 400

All cancers

1 in 7,700

Exposure to natural background radiation

1 in 12m

Crash on British airline

Sources: National Radiation Protection Board (Health Protection Agency); Times Database

Risky business

These activities would have the same risk as that for exposure to 1 millisievert of radiation (5 in 100,000 of dying in any year): - Smoking 70 cigarettes (cancer, heart disease)

- Drinking 25 litres of wine (cirrhosis of the liver)

- 50 hours in a coal mine (black lung disease)

- Travelling 300 minutes by canoe (accident)

- Travelling 500 miles by bicycle (accident)

- Travelling 7,500 miles by car (accident)

- Eating 2,000 tablespoons of peanut butter (liver cancer caused by aflatoxin B)