The benefits of living in a walkable neighborhood could be diminished by increased exposure to traffic-related air pollution, suggests a study led by St. Michael’s Hospital in Canada and ICES, a non-profit research institute that uses population-based health information to produce knowledge on a broad range of health care issues.

The open-access research, published in Environment International, and based on nearly 2.5 million adults from 15 Ontario municipalities, challenges the notion that living in walkable neighborhoods always improves overall health and well-being.

Walkability reflects how well neighborhoods afford opportunities for individuals to walk while performing daily tasks such as grocery shopping, running errands, or commuting to work.

Previous research has shown that individuals living in more walkable neighborhoods are more physically active, with downstream health benefits like lower rates of overweight and obesity, hypertension and diabete. But our findings confirm that walkability and air pollution are highly intertwined, potentially diminishing any health benefits derived from living in walkable, urban communities.

—study co-lead Dr. Gillian Booth, a scientist at St. Michael’s Hospital’s MAP Centre for Urban Health Solutions and ICES

The research team found that living in unwalkable neighborhoods was associated with a higher likelihood of having diabetes or hypertension than living in the most walkable communities. But, any observed benefit for those living in walkable areas appeared to decrease—or in some cases, disappear—as the level of air pollution increased.

Probability of hypertension and diabetes across levels of walkability and traffic-related air pollution.
Notes: all probabilities are adjusted for age, sex, ethnicity, immigration history, neighborhood income, and number of co-morbidities. Probabilities assessed at levels of covariates fixed at weighted average between categories for categorical predictors or mean value for continuous predictors. Walkability assessed using quintiles (Q5: highest, Q1: lowest). Howell et al.

Individuals living in highly walkable neighborhoods tend to be more likely to choose active forms of transportation, like walking or bicycling, as an alternative to driving. So they may be more exposed to air pollution based simply on the amount of time they spend outside.

—Nicholas Howell, co-lead of the research

The researchers said these results suggest that policies aimed at encouraging the development of walkable neighborhoods should consider strategies to mitigate residents’ exposure to air pollution.

Researchers used participant data from the Cardiovascular Health in Ambulatory Care Research Team (CANHEART) cohort—a population-based cohort drawn from databases including nearly all adults living in Ontario.

Resources

• Nicholas A. Howell, Jack V. Tu, Rahim Moineddin, Hong Chen, Anna Chu, Perry Hystad, Gillian L. Booth (2019) “Interaction between neighborhood walkability and traffic-related air pollution on hypertension and diabetes: The CANHEART cohort,” Environment International10.1016/j.envint.2019.04.070