Researchers at the Imperial College London found that exposure to air pollution more than 30 years ago may still affect an individual's mortality risk today, according to a study published Tuesday.

The new report comes from one of the world's longest running air pollution studies, which included 368,000 people in England and Wales followed over a 38 year period.

The researchers estimated air pollution levels in the areas where the individuals lived in 1971, 1981, 1991 and 2001, using measurements from Britain's extensive historic air pollution monitoring networks.

"We were surprised to find pollution has effects on mortality that persist over three decades after exposure," said lead author of the study, Dr. Anna Hansell, from the MRC-PHE Centre for Environment and Health at Imperial College London.

Highest risks were seen for respiratory disease, such as bronchitis, emphysema and for pneumonia. Air pollution also affected mortality risk from cardiovascular diseases such as heart disease, according to the study.

"Our study found that more recent exposures were more important for mortality risk than historic exposures, but we need to do more work on how air pollution affects health over a person's entire lifetime," said Hansell.

In the study, risks from pollution exposures were reported in units of 10 micrograms per cubic meter of air. Researchers compared these levels of exposure with data on disease and deaths. The study suggests that for every additional unit of pollution that people were exposed to in 1971, the risk of mortality in 2002 to 2009 increases by 2 percent.

The researchers also looked at more recent exposure and found a 24 percent increase in mortality risk in 2002 to 2009 for each additional unit of pollution people were exposed to in 2001.

"Our study adds to the weight of evidence that suggests breathing in air pollution isn't good for us in either the short or long-term. We need to continue collective efforts to reduce air pollution levels, both in the UK and internationally," said Hansell.

But Hansell also said pollution is still not the primary risk factor on health. "Your risk of dying early is much more dependent on other aspects of your lifestyle, like whether you smoke, how much you exercise, whether you are overweight, as well as on medical factors like your blood pressure." Endit