It's common knowledge that smoking near toddlers is bad, but it may be even worse than you think.
A Canadian study reveals that kids who were exposed to smoke early in childhood presented a wider body structure with a higher body mass index than other children.
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The results are the same for babies of mothers who smoked during their pregnancy.
Researchers say the results may actually be underestimated because of parents who underreport the amount they smoke out of shame.
40% of children around the world are exposed to secondhand smoke in their homes.
Click through the gallery to see e-cigarettes being used in schools: