Long-term exposure to air pollution, especially ground-level ozone, is like smoking about a pack of cigarettes a day for many years, according to a new study.
Like smoking, it can lead to emphysema, a lung condition that causes shortness of breath, and is usually associated with cigarette smoking. It's a debilitating chronic disease that shrinks the amount of oxygen that reaches your bloodstream.
The study, published Tuesday in the medical journal JAMA, is the largest of its kind. It examined the exposure to air pollution, specifically ground-level ozone, fine particulate matter, nitrogen oxide, and black carbon.
It examined more than 7,000 adults aged 45 to 84 for over a decade in six US metropolitan areas including Baltimore, Chicago, Los Angeles, New York City, St. Paul, Minnesota, and Winston-Salem, North Carolina.
‘Findings’
The researchers were able to see by using a CT scan that the exposure to each of the pollutants was associated with the development of emphysema.
They were able to show a decline in lung function with spirometry, a simple test that measures how much air you can breathe out in one forced breath.
The patients were all healthy when they started the study, and researchers controlled for factors that could compromise lung health, including age and whether the person was a smoker or was regularly exposed to secondhand smoke.
The strongest association between a pollutant and emphysema was seen with exposure to ozone, which was the only pollutant associated with an additional decline in lung function.
Exposure to ozone irritates and inflames the lining of our lungs when we breathe it in, it can leave us winded, cause asthma attacks, and make us more susceptible to infection.
Ground-level ozone is the part of smog that you cannot see, it is colorless and comes from the photochemical transformation that occurs when pollutants interact with sunlight.
"The increase in emphysema we observed was relatively large, similar to the lung damage caused by 29 pack-years of smoking and 3 years of aging," said Dr. R. Graham Barr, the Hamilton Southworth professor of medicine and epidemiology at Columbia University Irving Medical Center and a senior author of the paper.
One pack-year means smoking a pack of cigarettes a day for a year.
Air pollution levels were estimated at the home addresses of the participants. They were taking part in the Multi-Ethnic Study of Atherosclerosis Air Pollution (MESA Air) and MESA Lung studies.
Ambient concentrations of fine particulates and nitrous oxide, but not ozone, decreased significantly over the study period, the researchers said.
"These findings matter since ground-level ozone levels are rising, and the amount of emphysema on CT scans predicts hospitalization from and deaths due to chronic lower respiratory disease," said Barr.
With the climate crisis, there could be much higher levels of ground-level ozone in the future.
"Ground-level ozone is produced when UV light reacts with pollutants from fossil fuels," added Barr. "This process is accelerated by heatwaves, so ground-level ozone will likely continue to increase unless additional steps are taken to reduce fossil fuel emissions and curb climate change. But it's not clear what level of ozone, if any, is safe for human health."
Stephen Holgate, a special adviser on air quality at the Royal College of Physicians in the UK, said that while it had been known for some time that air pollution and cigarette smoking accelerates the development of emphysema in those who are genetically susceptible to it, this study showed that the same was true in the general population. Holgate was not involved in the research.
"This important study adds to the massive evidence base that air pollution, in this case specifically ozone, is harming people, especially those who are vulnerable with co-existent lung disease," he told the Science Media Centre in the UK.
Holgate noted that the study did have some limitations, including the fact that it didn't measure air pollution indoors, where most people spend their time.
"That is the challenge of this kind of research," said study co-author Dr. Joel Kaufman, physician epidemiologist and faculty member at University of Washington.
Studies like this essentially measure pollution as if you spent all your time on your front porch, he said. It doesn't take into account the time you spend in your house or your office, but it's a good general measure that shows exposure to pollution increases lung problems in the general population.
Kaufman says he hopes people will look at research like this and will use it to encourage their leaders to work on better environmental policies and pay attention to their fossil fuel consumption.
‘Fatalities’
World Health Organization (Who) estimated that around seven million people die every year from exposure to fine particles in polluted air that lead to diseases such as stroke, heart disease, lung cancer, chronic obstructive pulmonary diseases and respiratory infections, including pneumonia.
The tobacco epidemic is one of the biggest public health threats the world has ever faced, killing more than 8 million people a year around the world. More than 7 million of those deaths are the result of direct tobacco use while around 1.2 million are the result of non-smokers being exposed to second-hand smoke, according to WHO.
Around 80% of the 1.1 billion smokers worldwide live in low- and middle-income countries, where the burden of tobacco-related illness and death is heaviest. Tobacco use contributes to poverty by perting household spending from basic needs such as food and shelter to tobacco. This spending behavior is difficult to curb because tobacco is so addictive.
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