Preterm babies are those born three or more weeks before their due date.

According to the video below, these children "are more likely to die in the first year of life, or develop heart disease, diabetes, or have trouble learning".

The narrator, SFU health sciences professor Bruce Lanphear, notes that about a third of preterm births are a result of infection, poor nutrition, or having triplets.

But many others are linked to environmental factors.

According to Lanphear, a single environmental toxin can cause a baby to be born three to seven days before reaching full term. And in some countries, up to 18 percent of babies are born preterm.

Taking actions against toxins can have a positive effect. In Scotland, for example, the number of preterm births dropped 15 percent after outdoor smoking was banned. This reduced expectant mothers' exposure to secondhand tobacco toxins, thereby increasing the chances of their kids avoiding future health and learning difficulties.

Lanphear also states that in the United States, which has the most extensive biomonitoring, 17 percent of expectant mothers are exposed to three or more environmental toxins. And that poses risks to their children, given that a single toxin can bring on an early birth.

There are positive steps people can take, such as not using pesticides in the home, eating fish low in mercury, and frequently cleaning floors and carpets to remove dust that contains lead. They can also get engaged politically to support bans on cosmetic pesticides in their communities.

For those interested in more information, the SFU-based Canadian Environmental Health Atlas offers a online storehouse of environmental data and its impact on health.