Evidence linking air pollution and bronchitis ‘inconsistent’

Government advisory board COMEAP reviews existing evidence on impact of air pollution on chronic bronchitis

An official UK review of scientific studies has concluded there is “suggestive but not sufficient” existing evidence linking air pollution and chronic bronchitis, and that no association should therefore be included in health impact assessments.

The review looked at the impacts of air pollution on prevalence of chronic bronchitis

Carried out by the government’s the Committee on the Medical Effects of Air Pollutants (COMEAP), the review did find some epidemiological evidence of an association between chronic bronchitis and air pollution — mainly particulate matter PM10.

It also found evidence of an association between NO2 and chronic bronchitis “and of a link between qualitative measures of exposure to traffic-related air pollutants and chronic bronchitis”.

However, it found that the overall body of evidence in this area “is inconsistent and is not sufficient to imply a casual relationship” between bronchitis and air pollution.

Published online this week (April 5) by COMEAP — which advises the government on health policy and is made up air quality experts and scientists — the review concludes: “The Committee, therefore, does not recommend quantifying the relationship between long-term exposure to air pollution and chronic bronchitis in core health impact assessments.”

Health Impact Assessments (HIA) are used to assess the health impacts of policies, plans and projects using various techniques.

Ambient air pollution is increasingly being linked to a range of human health conditions, such as diabetes, mental health issues, obesity and a wide range of cardiopulmonary problems.

However the review, published on the Public Health England website, notes that “important gaps in our knowledge remain and uncertainties exist”.

The review had looked at scientific studies going back a number of decades which considered the health impacts of long-term exposure to particulate matter (PM), nitrogen dioxide (NO2), ozone (O3) and sulphur dioxide (SO2).

“Although concluding that the evidence base is not sufficiently robust to link long-term exposure to ambient air pollution and chronic respiratory morbidity, the working group was able to estimate that for up to 18% of those individuals reporting chronic phlegm in 2010, the symptom was possibly due to ambient air pollution exposure” – Frank Kelly, COMEAP chair

It concludes: “In the case of chronic bronchitis, which affected nearly 4.5 million individuals in the UK in 2010, more detailed and well-controlled epidemiological studies are required.”

Chronic bronchitis

Chronic bronchitis has long been associated with air pollution and is globally “one of the most challenging public health problems” as the third leading cause of death worldwide, according to the review.

In the UK alone, 3 million people are estimated to have chronic bronchitis, yet only 900,000 have been diagnosed. The condition results in 130,000 emergency hospital admissions each year and is estimated to cost the UK’s healthcare system between £810-930 million annually.

The review also explains that the impacts of smoking — a major cause worldwide of bronchitis, or chronic obstructive pulmonary disease — are very similar to that of poor air quality, as it involves the inhalation of “rather similar toxicants albeit at much lower concentrations”.

Therefore, deciding how much of the reduction in bronchitis in the UK in recent years is down to improving air quality is difficult, as at the same time there has been a drop in the prevalence of smoking.

Premature deaths

The review forms part of COMEAP’s work towards an official estimate of the number of premature deaths caused by nitrogen dioxide and particle pollution combined, but a precise publication date for this information is still unknown as the calculation for bringing the two pollutants is said to be complex.

Currently, COMEAP’s UK-wide estimate puts the number of premature deaths at 29,000 caused by particulate matter alone, but no official estimate has been made of the impacts of NO2.

Other recent estimates have tried to bring the two pollutants together, with the Royal College of Physicians claiming a 40,000 figure (see AirQualityNews.com story), and a separate London Mayor report putting the number at roughly 9,500 for the UK capital alone (see AirQualityNews.com story).

Related Links:

–COMEAP report: ‘Long-term exposure to Air Pollution and Chronic Bronchitis’