Impacts on air pollution and health by changing commuting from car to bicycle

Abstract

Our study is based on individual data on people's home and work addresses, as well as their age, sex and physical capacity, in order to establish realistic bicycle-travel distances. A transport model is used to single out data on commuting preferences in the County Stockholm. Our analysis shows there is a very large potential for reducing emissions and exposure if all car drivers living within a distance corresponding to a maximum of a 30min bicycle ride to work would change to commuting by bicycle. It would result in >111,000 new cyclists, corresponding to an increase of 209% compared to the current situation. Mean population exposure would be reduced by about 7% for both NO and black carbon (BC) in the most densely populated area of the inner city of Stockholm. Applying a relative risk for NO of 8% decrease in all-cause mortality associated with a 10μgm decrease in NO, this corresponds to >449 (95% CI: 340-558) years of life saved annually for the Stockholm county area with 2.1 million inhabitants. This is more than double the effect of the reduced mortality estimated for the introduction of congestion charge in Stockholm in 2006. Using NO or BC as indicator of health impacts, we obtain 395 (95% CI: 172-617) and 185 (95% CI: 158-209) years of life saved for the population, respectively. The calculated exposure of BC and its corresponding impacts on mortality are likely underestimated. With this in mind the estimates using NO, NO and BC show quite similar health impacts considering the 95% confidence intervals.

Air pollution as a risk factor in health impact assessments of a travel mode shift towards cycling

“…For example, Maizlish et al [34] and Woodcock et al [35,36], who evaluated the mode of transport shift to active travel in whole population. In one study, Johansson et al [37], individual data on people’s home and work addresses were used, as well as their age, sex, and expected physical capacity, in order to establish realistic bicycle travel distances. Rojas-Rueda et al [38] and Woodcock et al [39] evaluated the current benefit of increased cycling due to a public bicycle-sharing program.…”

“…Nine studies examined the air pollution impact on the general population [34–37,40,41,46,48,50], four estimated impacts on active commuters [38,39,42,43], and five included impacts on both the general population and active commuters [22,44,45,47,49]. The included studies modeled both particulate and gaseous pollutants such as particulate matter (PM) less than 2.5 µm and less than 10 µm (PM2.5 and PM10), sulfur dioxide, nitrogen dioxide (NO 2) and nitrogen oxides (NOx), carbon monoxide, ammonia, etc.…”

“…Dhondt et al [40] selected elemental carbon (EC) for their analysis due to its sensitivity to combustion-related emissions, for example, diesel exhaust, and to its high relevance to health compared with PM. Johansson et al [37] used NOx, NO 2 and black carbon (BC) as exhaust indicators and compared the size of the estimated health impacts. Some studies also employed air pollutants in their sensitivity analysis that were different from the pollutants in their main analysis [38,44].…”

“…One difference between the approaches is whether or not established emission factors were used and how detailed these are reported in the paper. Some papers give a reference to how emissions were calculated (typically from vehicle fleet, flow, speed, and published emission factors) [34,35,37,40,41,48,50], whereas a few report the emission factors explicitly in the text [36,46,49]. Buekers et al [47] did not use emission factors; instead, they used the proportion of the concentration originating from traffic.…”

“…The studies assessed associated risk by using RRs and exposure-response functions given in previously published literature to calculate the impact of changes in transport emissions either on mortality [22,37,43,44] or on BoD. Among the studies including morbidity and mortality outcomes that quantified BoD, the Disability adjusted Life Years (DALYs) was estimated by calculating YLD and YLL [34–36,39,40,42,45,46].…”