The recent scandal over Volkswagen's diesel emission cheating has led to an increased focus on diesel pollution and its negative health impacts. And there is indeed ample evidence to suggest that exposure to diesel fumes can cause chronic health impacts ranging from coughing and asthma to heart attacks and death.
But what levels of diesel pollution are we exposed to each day? And where are the highest concentrations?
Tim Johns of the BBC set out to find out, tracking the levels of diesel-related particulate matter he was exposed to during the course of an average week traveling around both central London and suburban Bedford. He was surprised by the results.
Below are some of the results that Johns recorded during his experiment; the figures represent black carbon particles measured in micrograms per cubic meter. For reference, Johns was told to expect between 0 and 3 micrograms when indoors and away from traffic. Experts did not give a specific level that's considered safe, but advised that we should all try to limit our exposure where possible (see editor's note below):
Work office environment (London)—0.8
Riding on diesel train—8.5
Riding on electric train—2.4
Waiting on train station platform—13.2
Riding in taxi in slow traffic (London)—19.9
What's interesting, to me, is the fact that these numbers show that diesel pollution is a societal problem. While we may be able to individually reduce our risk somewhat by avoiding high-exposure areas or activities, some of the things we do to reduce our own emissions may actually increase our exposure. (Riding on a diesel train as opposed to driving by car, for example.)
Ultimately, this is one more reason why we need to cut back on emissions at the source. Fortunately, from double decker electric buses to a huge reduction in the use of the private car and a shift to cycling, there are signs that London us finally getting serious about cleaning up its air.
I am sure Johns and his fellow commuters will be mighty glad for it.
(The BBC article makes no mention of unsafe limits, but the World Health Organization notes that small particulate pollution has health impacts even at very low concentrations, "No threshold has been identified below which no damage to health is observed." The WHO 2005 guideline limits (which can be seen here) aimed to achieve the lowest concentrations of PM possible. –Editor)