Category Archives: pollution

Documentary of bikes vs cars from Swedish film directors

Based on the trailer alone, I am not rushing out to see the new documentary Bikes vs. Cars. It seems to me we have already been through most of these arguments, especially from advocates. I guess it might be new for a Swedish director. The “international flair” might be new. But otherwise, I hope documentaries like this dig a bit deeper. Maybe it does.

Cyclists defensive about the pollution they emit

Cyclists recently came out in hoards to repel the comments from the Washington State politician who claimed, “Since CO2 is deemed to be a greenhouse gas and a pollutant, bicyclists are actually polluting when they ride.” Both the Seattle times and Velonews picked it up. And, the politician has since apologized.

It reminds me of the GM ad telling college students to stop pedaling and to start driving–an ad that was met with so much opposition that it was pulled by GM back in the fall of 2011.

** And just fyi, here are two “journalistic reporting stats” that appeared in the Seattle Times report: (1) On average, cars emit about three-quarters of a pound of carbon dioxide per mile, while bicycling releases just over 1 ounce per mile, including manufacturing, according to analysis by the European Cyclists Federation. and (2) food calories burned by a rider may well be equivalent to 650 miles per gallon, figures Todd Litman, of the Victoria Transport Policy Institute.

Health tradeoffs (some of them) hitting popular press

The Atlantic Cities has a diddy exposing some of the pollution ill-effects of cycling. But, the larger question is still left open. Even considering the air pollution burden from cycling–and perhaps even the safety risks owing to crashes–is it healthy? We need to look at the larger context. The prevailing evidence, I would argue, suggests that cycling is healthy–overall–because of the physical activity benefits.

Cycling on busy roads and concentrated auto exhaust

I received the following email inquiry this morning:


Mr Krizek,

Some have questioned the wisdom of promoting bike use on roadways especially very busy ones or at busiest times because of the health hazards of heavy breathing in concentrated auto exhaust.
What can you say about that?

Here is a response, fresh off the press from the book recently edited by John Parkin of the UK:

Kevin J. Krizek (2012). Cycling, Urban Form and Cities: What Do We Know and How Should We Respond? Cycling and Sustainability; Transport and Sustainability, Volume 1. John Parkin, editor. Chapter 5; 111-130. Emerald Group Publishing, UK.

…from page 121

“Some recent research on cycling aims to better understand unintended consequences linked with increased exposure to air pollution (Panis, 2011; Zuurbier et al., 2010). Despite the many virtues of cities for cycling, including relatively high land use densities, a drawback to cycle use is related to air quality and this becomes more important when the activity in question requires significant amounts of oxygen intake. Air pollution can affect the respiratory system because of the deep draw down of air into the lungs and may even lead to heart rate variability (Weichenthal et al., 2011). Of particular concern are ultrafine particulates. Hazards from air pollution are extremely localized and require close proximity (a very few metres), which is just the position of cycle traffic in relation to localized air pollution problems caused by motor traffic. Various treatments have been proposed such as separating cycle traffic from motor traffic by more than the requisite distance, allowing and encouraging bicycles to wait for a traffic signal green light in front of the queue of motor traffic (in so-called bicycle boxes or behind so-called advanced stop lines, which also then have the advantage that they allow cycle traffic a head start before motor traffic accelerates from a stop), or, through appropriate area wide traffic management to create a tiered system of routes with cycle traffic and motor traffic encouraged to use adjacent parallel routes. Overall, however, the evidence suggests that there are potential consequences to cycling in urban areas dominated by motor traffic that need to be addressed in order to avert the potential for cycling in cities being increasingly associated with health risks (Zuurbier et al., 2010).”

Ride your %^&#$% #^$&@ bike

The humorous–almost self-deprecating videos keep coming. This one is questionable in terms of appropriateness for the blog. It is a bit risqué; you will want to turn off the sound if you’re at work or keep the kids in the other room. The interesting thing about all of these videos is how these “artist” pieces so strongly resonate with their own subset of the cycling population. 

Advancing “total health:” shining light on somewhat competing issues of physical activity & air pollution exposure

What if a community had all the successful ingredients leading to higher rates of cycling and walking (e.g., population density, intersection density, diverse mix of land uses, bike paths galore, etc)? Would planners then being doing their job? How would this relate to the total health for residents?
A small but growing number of studies are looking at two criteria of health simultaneously: exercise and air pollution. The results suggest these things might not always move together in the same direction—a “wake up” call for planners who have typically been obsessed with increasing physical activity. This study helps bring to light that the health benefits from increased physical activity in highly walkable neighborhoods may be offset by adverse effects of air pollution exposure. In the words of one of the co-authors, “city planning efforts have been planning to optimize one risk factor [lack of physical activity], when there are multiple risk factors to be taken into account.” <just fyi, another health consideration is bicycle/traffic safety, but that issue might be less controversial>
Should we worry about this? Of course. Is it a growing issue that has the potential to further divide planning initiatives? Hopefully not. Two possibilities:
·         Will cleaner cars, cleaner businesses, and cleaner everything else coming on-line possibly lessen the need to be concerned about pollution.
·         Is the fact that the study is based in Los Angeles—a basin that has perennially been out of compliance with EPA standards and probably has a disproportionate share of polluting car use (both in terms of sheer use and % of fleet that is old)—reason to suggest the issues there are not as bad as other places?
It is hard to say. I don’t think the solution is pollution filter face masks. This work merely suggests an area worth of further investigation to ensure we are not shooting ourselves in the foot.
Background: Physical inactivity and exposure to air pollution are important risk factors for death and disease globally. The built environment may influence exposures to these risk factors in different ways and thus differentially affect the health of urban populations.
Objective: We investigated the built environment’s association with air pollution and physical inactivity, and estimated attributable health risks.
Methods: We used a regional travel survey to estimate within-urban variability in physical inactivity and home-based air pollution exposure [particulate matter with aerodynamic diameter ≤ 2.5 μm (PM2.5), nitrogen oxides (NOx), and ozone (O3)] for 30,007 individuals in southern California. We then estimated the resulting risk for ischemic heart disease (IHD) using literature-derived dose–response values. Using a cross-sectional approach, we compared estimated IHD mortality risks among neighborhoods based on “walkability” scores.
Results: The proportion of physically active individuals was higher in high- versus low-walkability neighborhoods (24.9% vs. 12.5%); however, only a small proportion of the population was physically active, and between-neighborhood variability in estimated IHD mortality attributable to physical inactivity was modest (7 fewer IHD deaths/100,000/year in high- vs. low-walkability neighborhoods). Between-neighborhood differences in estimated IHD mortality from air pollution were comparable in magnitude (9 more IHD deaths/100,000/year for PM2.5 and 3 fewer IHD deaths for O3 in high- vs. low-walkability neighborhoods), suggesting that population health benefits from increased physical activity in high-walkability neighborhoods may be offset by adverse effects of air pollution exposure.
Policy implications: Currently, planning efforts mainly focus on increasing physical activity through neighborhood design. Our results suggest that differences in population health impacts among neighborhoods are similar in magnitude for air pollution and physical activity. Thus, physical activity and exposure to air pollution are critical aspects of planning for cleaner, health-promoting cities.