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expert reaction to study looking at air pollution in people with emphysema, and making comparisons with smoking

Research, published JAMA, reports a connection between the level of air pollution where a person lives, and their risk of developing emphysema. Comparison is also drawn with the effects of cigarette smoking. 


Prof Stephen Holgate, UKRI Clean Air Champion and RCP Special Advisor on Air Quality, University of Southampton, said:

“It has been known for some time that in those genetically susceptible to emphysema cigarette smoking and air pollution accelerates their development of emphysema.  Here we have a large study showing at the population level the same is true.  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.

“This is a large and well conducted study conducted between 1999 and 2018 involving 7071 participants (6814 MESA participants and 257 MESA Air study participants) aged 45 to 84 years from 6 US cities, using CT scanning to assess lung density as a proxy for emphysema.  They also studied lung function by spirometry over the same time period.  Percent emphysema was defined as the percent of lung pixels less than −950 Hounsfield units and was assessed up to 5 times per participant via cardiac CT scan (2000-2007) and equivalent regions on lung CT scans (2010-2018).  Spirometry was performed up to 3 times per participant (2004-2018).  Using both measures, they explored the longitudinal impact of several air pollutants.  They took account of many potential confounders and showed for both outcomes there was significantly greater effects of ozone, but interestingly not PM2.5 or NO2 on CT indices of emphysema and loss of lung function.

“While most key covariates were 99% to 100% complete, 5% of participants were missing complete information to calculate pack-years of smoking and therefore they assigned such participants a value of zero and adjusted for an indicator variable reflecting missing pack-years data.  Other limitations recognised by the investigators included the estimation of pollutants only in outside (ambient) air, not indoors where people spend most of their time; percent emphysema was measured only in the lower two-thirds of the lung; the need to adjust for stratification by scanner type; and no volume correction of CT data was performed.

“The strength of the association between O3 and emphysema looks impressive and as a powerful oxidant, has a good mechanistic basis especially since outdoor air pollution, and again O3 was associated with disease severity in α1-antitrypsin deficiency (Wood AM et al. European Respiratory Journal 2009; 34: 346-353), a strong genetic driver for emphysema.”


‘Association between long-term exposure to ambient air pollution and change in quantitatively assessed emphysema and lung function’ by MengWang et al. was published in JAMA at 16:00 UK time on Tuesday 13 August 2019. 

DOI: 10.1001/jama.2019.10255


Declared interests

None received.

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