After posting about a research on diesel pollution exposure on school buses previously, I thought it will be good to look deeper into the effects of such exposure. The journal article that I looked at did not provide any particularly surprising information to me, since I already had a rough idea about how polluted diesel exhaust is, and how they pose various problems to our respiratory tracts. What this article taught me more about is some specific respiratory effects (it is from a health journal, the New England Journal of Medicine!) and some considerations when it comes to possible experimental design.
McCreanor et al (2007) did a research on the short-term respiratory effects of exposure to diesel traffic in asthmatic persons in an urban, roadside environment. What this research aims to do is to build on research from previous studies that were conducted under laboratory conditions — previous studies have not been entirely consistent and exposure to those pollutants may not reflect that of real conditions. McCreanor et al (2007) suggests that these discrepancies may be due to interactions between different pollutants, or that pollutants under laboratory conditions may have removed. Instead of conducting the research indoors, they got participants to expose themselves to diesel traffic by the streets.
They got 60 adults with mild or moderate asthma to walk for 2 hours along Oxford Street, London, and Hyde Park on a separate occasion (I briefly mentioned in my first post that Oxford Street was raised in the spotlight just recently in 2015 for extremely high nitrogen dioxide levels!). The study was limited to winter months to avoid other variables such as exposure to pollen. As expected, participants had significantly higher exposure to fine particles, in particular, PM2.5 when walking along Oxford Street. There were also higher exposure to other ultrafine particles, elemental carbon, and nitrogen dioxide. As a result, participants with prolonged exposure to air pollution by the streets recorded consistent respiratory effects such as a reduction in the forced expiratory volume in 1 second and forced vital capacity. Respiratory tracts were also inflamed after prolonged exposure, and these effects are more severe for those with moderate asthma.
Of course, having an experimental design as such will lead to a lot more confounding variables — the authors mentioned that the respondents produced symptomatic responses, but other variables such as traffic noise may have played a part in increasing stress levels, which may trigger the onset of asthmatic symptoms too.
Diesel exhaust is also cancerous — according to NHS Choices, WHO’s International Agency for Research on Cancer (IARC) decided to classify diesel exhaust as carcinogenic instead of “probably carcinogenic” in 2012 after there is sufficient evidence that diesel exhaust is a cause of lung cancer.
How bad are diesel exhaust fumes? As a reference, The Daily Mail quoted Kurt Straif, director of the IARC department that evaluates cancer risks, who mentioned that the effects of breathing diesel exhaust is of the same magnitude as that of passive smoking. (So, try not to stay indoors too when there are people smoking in the room!)
(And since there are 2 pictures showing a lot of smoke, Diesel Exhaust + Cigarette smoke = Smoky Streets indeed! Can’t resist not mentioning the blog name, haha. Even though the contents of this blog should be much more than just this two topics!)
McCreanor, J., Cullinan, P. Nieuwenhuijsen, M.J., Stewart-Evans, J., Malliarou, E., Jarup, L. Harrington, R. Svartengren, M., Han, I., Ohman-Strickland, P., Chung, K.F., Zhang, J. (2007). ‘Respiratory Effects of Exposure to Diesel Traffic in Persons with Asthma’. The New England Journal of Medicine 357: 2348-2358.
NHS Choices (2012). ‘WHO: ‘Diesel Exhaust Fumes Cancerous”. [Online] Retrieved from: http://www.nhs.uk/news/2012/06june/Pages/who-classes-diesel-vehicle-exhaust-fumes-as-carcinogen.aspx [Last Accessed: 25 February 2015]
The Daily Mail (2012). ‘Diesel exhaust fumes are ‘major cancer risk’ and as deadly as asbestos and mustard gas, says World Health Organisation’. [Online] Retrieved from: http://www.dailymail.co.uk/health/article-2158574/Diesel-engine-exhaust-fumes-major-cancer-risk.html [Last Accessed: 26 February 2015]