Exertion and air pollution: new news

There was something very surprising in a recent journal article -- something that has stood on its head a long-standing assumption about bike commuting and health.

Most of the studies before that one [1] assumed that cyclists, runners, and walkers near traffic enjoyed a small amount of protection from the traffic pollutants, compared to car drivers and passengers, because of the physics of air movement between cars passing each other from opposite directions. It now seems that that was wishful thinking. [2]

Even though biking is great for my heart...
... I inhale a lot more air in the street (because of exertion) than a driver does. And traffic air is polluted air. Because of less exertion needed for driving, every volume of air that I inhale ..... ... is dwarfed by the 4.3 volumes of air that I inhale. Particulate matter (PM) -- tiny specks of soot -- are particles of carbon that can be breathed deep into the  lungs. The smallest PM can even get into and through the alveoli, the tiny air sacks which pass oxygen into the blood stream. Particulate Matter (PM) this size (10 microns) or <i>larger</i>, can usually be caught by the inside of the nose and throat, mitigating harm. PM2.5 (2.5 microns) leads to high plaque deposits in arteries, which contribute to a hardening of the arteries. And that can lead to heart attacks and other cardiovascular problems. Tiny particles of air pollution -- less than one tenth the width of a human hair -- can trigger clotting in the blood... [which] helps explain how air pollution causes heart attacks and strokes. image of a tailpipe and exhaust Outdoor air pollution in the U.S. due to particulate pollution alone was estimated by the EPA in 1997 to cause at least 20,000 premature deaths each year... Globally, about 800,000 people per year die prematurely due to outdoor air pollution Exercise in general is a huge benefit to health, but inhaling polluted air during exercise takes a bite out of the benefit. One extreme ratio for exertion near traffic is 51% benefit and 49% detriment... ... and the opposite extreme is 99% benefit and only !% detriment. The point is to work toward a world where exercise, no matter how near to a city street, is an unmitigated benefit (no detriment). The air pollution is less on the sidewalk than in the street... ... not to mention that riding on the sidewalk is alot safer. Unfortunately, it's only a partial solution, because the air's only 15% better on the sidewalk.. Moreover, walkers and runners are probably exerting themselves more than a cyclist, and are thus inhaling an even greater volume than the cyclist is. What about just walking, running, or cycling on a side street -- won't that solve it? No; other traffic pollutants collect in higher concentration on side streets. The ultimate solution, of course, is to reduce the amount of pollution, by creating an incentive to pollute less. That incentive might best come from incorporating the health-care costs of a pollutant-producing fuel into the cost of the fuel itself. In addition to cutting health costs and climate change, there could also be a cut in joblessness: Infrastructure to make bicycling safe and healthy is the most effective transportation-related solution to creating jobs. Thus, even though bicycling, running, and walking are superior healthwise to driving a car, there is still a cost imposed by the car's emissions,  and that cost may not go away until it's imposed as part of the cost of the gas.

Main sources

[1] Luc Int Panis, et. al., Exposure to particulate matter in traffic: A comparison of cyclists and car passengers, Atmospheric Environment Volume 44, Issue 19, June 2010, Pages 2263-2270.

[2] Kaur et al., 2005 S. Kaur, M. Nieuwenhuijsen and R. Colvile, Personal exposure of street canyon intersection users to PM2.5, ultrafine particle counts and carbon monoxide in Central London, UK, Atmospheric Environment 39 (2005), pp. 3629–3641.

Notes

... the amount of lung pollutants for those who are exerting themselves, compared to those who are not, has been found to be about 4.3 to 1. (fig 4): Panis et al. (2010), Exposure to particulate matter in traffic: A comparison of cyclists and car passengers, Atmospheric Environment Volume 44, Issue 19, June 2010, Pages 2263-2270.

..."On any given day, scientists estimate that about 10 MILLION tons of solid particulate matter are suspended in our atmosphere." (fig 5.1), Particulate Matter Pollution, www.wunderground.com/health/pm.asp?, summarizing air quality information from the US Environmental Protection Agency. See www.airnow.gov/

... "Ultra fine particles can also be absorbed in the blood, which may have damaging effects." (fig 5.2): Mills et al. (2011)Combustion-derived nanoparticulate induces the adverse vascular effects of diesel exhaust inhalation. European Heart Journal, July 13, 2011 DOI: 10.1093/eurheartj/ehr195

(figs 5.5 and 5.6) The images comparing the sizes of particulate matter to that of a human hair are modified from this image on the US EPA website: www.epa.gov/airscience/quick-finder/particulate-matter-image.htm

... PM2.5 (2.5 microns) leads to high plaque deposits in arteries, which contribute to a hardening of the arteries (f5.6): Pope et al. (2002) Cancer, cardiopulmonary mortality, and long-term exposure to fine particulate air pollution, J. Amer. Med. Assoc. 287 (9): 1132–1141. doi:10.1001/jama.287.9.1132. PMID 11879110, at http://jama.ama-assn.org/cgi/reprint/287/9/1132.

...In a polluted environment, a volume the size of a sugar cube can contain as many as 200,000 particles! (fig 5.6): Kaur et al. (2005) Personal exposure of street canyon intersection users to PM2.5, ultrafine particle counts and carbon monoxide in Central London, UK, Atmospheric Environment 39 (2005), pp. 3629–3641.

..."Tiny particles of air pollution ... can trigger clotting in the blood" (fig7): Steenhuysen, J. (2007), Air pollution triggers blood clots: study, at http://www.reuters.com/article/2007/09/21/environment-heart-pollution-dc-idUSN2042863220070921?sp=true The study which this article reports on is in the Journal of Occupational and Environmental Medicine here: http://www.acoem.org/Page2Column.aspx?PageID=7392&id=7092

...Although traffic exhaust accounts for only 7.4% of all heart attacks...that 7.4% amounts to the single most serious preventable cause of heart attack in the general public (fig 7) : Nawrot et al. (2011) Public health importance of triggers of myocardial infarction: a comparative risk assessment, Lancet 377: 732-740.

...Other problems that can be traced directly to traffic exhaust are stroke, lung cancer, and asthma (fig 7)
Relevant to stroke:
Brook et al. (2010) Particulate Matter Air Pollution and Cardiovascular Disease: An Update to the Scientific Statement From the American Heart Association, in Circulation 2010, 121:2331-2378. See also Evidence growing of air pollution’s link to heart disease, death, at http://newsroom.heart.org/pr/aha/1029.aspx?link_page_rss=212867 American Heart Association.

Relevant to lung cancer:
Pope et al. (2002) Cancer, cardiopulmonary mortality, and long-term exposure to fine particulate air pollution, J. Amer. Med. Assoc. 287 (9): 1132–1141, at http://jama.ama-assn.org/content/287/9/1132.full.pdf+html See also: http://www.sciencedaily.com/releases/2007/12/071205190853.htm

Relevant to asthma:
Li et al. (2003) Particulate air pollutants and asthma—a paradigm for the role of oxidative stress in PM-induced adverse health effects Clin Immunol 109: 250–265.14697739. See also Diesel Exhaust Fumes Affect People With Asthma...

... Outdoor air pollution in the U.S. due to particulate pollution alone was estimated by the EPA in 1997 to cause at least 20,000 premature deaths each year and ...Other estimates [of premature death] place this number at 50,000 to 100,000 deaths per year" (fig 6a) from Masters,J. Ph.D, Air Pollution, http://www.wunderground.com/health/airpollution.asp?MR=1 last accessed Nov. 13, 2011.

..."Globally, about 800,000 people per year die prematurely due to outdoor air pollution" and ...The 800,000 represents about 1.2 percent of total annual global deaths (fig 6b) from Masters,J. Ph.D, Air Pollution, http://www.wunderground.com/health/airpollution.asp?MR=1 last accessed Nov. 13, 2011.

..."strong evidence that regular physical activity contributes to the prevention of chronic conditions..." (fig Venn 1) Panis et al. (2010) Exposure to particulate matter in traffic: A comparison of cyclists and car passengers, Atmospheric Environment 44 (19):2263-2270.
Compare to:
..."cyclists in traffic have more oxidative DNA damage"(fig Venn 1) Vinzents et al. (2005), Personal Exposure to Ultrafine Particles and Oxidative DNA Damage, Environmental Health Perspectives, Vol 113(11).

....the concentration of particulate matter on the sidewalk is 85% of the concentration in the street (fig 12) Kaur et al. (2005) Personal exposure of street canyon intersection users to PM2.5, ultrafine particle counts and carbon monoxide in Central London, UK, Atmospheric Environment 39 pp. 3629–3641.

...walkers and runners are.... inhaling an even greater volume than the cyclist is (fig 13) Briggs, David J, et.al, (2008), Effects of travel mode on exposures to particulate air pollution, Environment International, 34(1) 12-22.

...other traffic pollutants collect in higher concentration on side streets (fig 14) Hertel et al. (2008), A proper choice of route significantly reduces air pollution exposure — A study on bicycle and bus trips in urban streets, Science of the Total Environment 389, 58–70.

...working to reduce particulate matter will not only help to protect your health; it will also help to lessen climate change (fig 15) The US Environmental Protection Agency, http://www.epa.gov/airscience/quick-finder/climate-change.htm

...For every $1 million spent, cycling infrastructure projects created an average of 11.4 jobs...(fig 16): http://www.peri.umass.edu/236/hash/64a34bab6a183a2fc06fdc212875a3ad/publication/467/

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