Antioxidants may reduce harm from air pollution.

Aug 10, 2012

Canova C, C Dunster, FJ Kelly, C Minelli, PL Shah, C Caneja, MK Tumilty, P Burneya. 2012. PM10-induced hospital admissions for asthma and chronic obstructive pulmonary disease: The modifying effect of individual characteristics. Epidemiology

Synopsis by Virginia T. Guidry

People who have asthma and COPD are more vulnerable to particulate air pollution if they have low levels of vitamin C in their blood, a study from London found. The results suggest a diet rich in fruits and vegetables may suppress some of the harmful effects of air pollution.

Eat your fruits and vegetables, especially if you have chronic respiratory ailments.

A study of adults with asthma and chronic obstructive pulmonary disease (COPD) found that those with lower levels of certain antioxidants in their blood were more vulnerable to the harmful effects of air pollution. Air pollution can aggravate both asthma and COPD, producing symptoms that can be strong enough to lead to hospitalization.

This study is important because it indicates that a healthy diet including fruits and vegetables may protect against the common health threat of air pollution.

Particulate matter (PM) – the main pollutant measured in this study – is produced by traffic and combustion of fossil fuels. PM less than 10 micrometers in diameter, or PM10, is known to exacerbate respiratory illness and increase the risk of heart attacks and other cardiovascular disease. The potential for individual characteristics – such as diet or genetics – to modify these known effects is a new area of research.

One way air pollutants can harm health is through oxidative stress. Harmful oxidant molecules can form when air pollutants are absorbed through the lungs. These oxidants – also called free radicals – roam the body and bombard and damage cells. The body constantly tries to counteract oxidant molecules with protective ones (antioxidant). If not enough anti-oxidant molecules are available to cancel them out, oxidative stress can occur.

In this study, the researchers wanted to see if individual levels of antioxidants and related genetic markers would protect against harm from oxidative stress imposed by particulate air pollution. Participants included 209 adults who were admitted to a London hospital for asthma or COPD between 2008 and 2010. The authors compared PM10 levels on the day of admission with PM10 levels on two control days – the day two weeks before and the day two weeks after admission. Participants were grouped by the level of antioxidants – vitamins C, E, A and uric acid – in their blood and certain genes that may protect against oxidative stress.

As in prior studies, the results showed that PM10 levels were higher on the days prior to hospital admissions for asthma or COPD. Smokers and those older than 75 years of age were especially vulnerable to air pollution effects.

Participants with low levels of vitamin C in their blood were also more vulnerable to PM10. This effect was not seen with other antioxidants and genes.

One strength of this study was the use of a case-crossover design, in which individuals are compared to themselves at different times, rather than to other people. This prevents differences among people – such as gender and socioeconomic status – from complicating the results.

This study emphasizes that some people, such as those with preexisting respiratory disease, are more susceptible to the harmful effects of air pollution than others. This is an important consideration for public health.

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