Kids' exposure to second-hand smoke in cars fell by more than a third during the five years that most provinces phased in bans on smoking in vehicles with children.
The percentage of children under 16 who reported being in a car with a smoking adult fell to 28 per cent in 2010 from 43 per cent in 2005, according to the Canadian Tobacco Use Monitoring Survey.
New research published on Thursday in the Cancer Advocacy Coalition of Canada's annual report card suggests the decline by province during that period mirrored the sequential adoption of bans across Canada.
Bans took effect beginning in Nova Scotia in April, 2008, and concluding in Saskatchewan in October 2010. Newfoundland and Alberta enacted bans in 2011 and 2013, respectively. Quebec does not have a similar prohibition.
The research shows that Ontario, which was the second province to enact a ban, recorded the largest reduction, at almost 38 per cent, while the decline of 3 per cent in Saskatchewan was the smallest.
Children's exposure to second-hand smoke in cars fell by 23 per cent in Nova Scotia, 33 per cent in British Columbia, 22 per cent in Prince Edward Island, 18 per cent in New Brunswick and 25 per cent in Manitoba.
By contrast, exposure in the three provinces that did not have prohibitions dropped collectively by just 17 per cent, according to the research, which culled data from the tobacco-use survey and youth smoking surveys conducted by Statistics Canada.
Hai Nguyen, an economist and post-doctoral researcher in the Faculty of Pharmacy at the University of Toronto, acknowledged the overall reduction nationwide was attributable to other factors besides the bans. The percentage of Canadians who smoke has been steadily declining for years.
Mr. Nguyen said, however, that the bans appear to have been a contributing factor.
"These bans are effective at reducing the level of exposure of second-hand smoke by children in a private vehicle by a significant number," Mr. Nguyen said.