If you were to get on Interstate 5 near the Mexican border and drive north through Los Angeles, Sacramento, Portland and Seattle, the first stoplight youâd encounter would be in Canada -- just inside Vancouverâs city limits.  Thatâs because I-5 ends just south of Vancouver, British Columbia, making it the only major city in North America without an interstate running through it, says Deputy City Manager Sadhu Johnston.  With a dense downtown, a strong public transportation system and miles of bike lanes, itâs the âmost walkable city in Canada,â Johnston says.  The shift away from a car-centered culture in one reason the city also has some of the cleanest air in the world.  Other reasons include strict environmental standards for buildings and businesses, and a natural environment -- marked by evergreen forests and ocean breezes -- that helps purify air pollutants.  Air quality is a good indicator for health in any city, says Janice Nolen, assistant vice president for national policy at the American Lung Association. â(Pollution) can kill people,â she says. âIt can shorten lives by days to months.â  It can cause heart attacks and strokes, asthma in children, low birth weight and, of course, lung cancer.  Car emissions are a major source of these pollutants. Research has showed that people who live close to a busy highway breathe in many more particles and harmful chemicals than those who donât, Nolen says.  In 2011, Vancouver adopted the Greenest City 2020 Action Plan, which aims to make the Canadian metro area the most environmentally friendly city in the world.  Vancouverâs leaders have done a lot to protect and celebrate its natural environment, Johnston says. Residents have easy access to acres of green space, fresh water, the ocean and nearby mountains.  At the same time, businesses and government have collaborated to build up downtown. As a result, there has been about a 75% increase in the number of people who live and work in Vancouverâs center in the past 20 years, which means fewer commuters driving in and out of the city.  Overall, Vancouver has seen a 6% reduction in its carbon emissions since 1990, Johnston says, despite a nearly 30% growth in population and an 18% growth in jobs. He says the city has showed that âyou can create a clean and green environment without impacting your quality of life and your economy.â
Our health is not just a byproduct of how we live. Itâs also about where we live. Just ask residents of the world's 10 healthiest cities.