From the article:  "This indicates that children exposed to marijuana smoke are also more likely to be exposed to tobacco smoke, which increases their risk for cognitive deficits and respiratory ailments."

So, marijuana is harmful because....  tobacco smoke?   -  LOL  - Give us a break!  -  How desperate to throw dirt on marijuana!

This study is contrived propaganda.  -  Science has shown even FIRST-HAND marijuana smoke has no significant harms.  --   The country's leading researcher of marijuana and lung disease, UCLA's Dr. Donald Tashkin, conducted investigations over 30 years, initially believing there must be a causal relationship. But he finally concluded that smoking marijuana does NOT cause cancer or ANY other serious disease.

Tashkin said:  "We hypothesized that there would be a positive association between marijuana use and lung cancer, and that the association would be more positive with heavier use. What we found instead was no association at all, and even some suggestion of a protective effect."

As Ms. Forsman has shown, our bodies make our own endocannabinoids, so certainly, with the just the trace elements discussed here, marijuana could turn out to have a beneficial effect - even for children.
  
But when that's discovered, don't look for it to splashed on the news wire like this bogus study was.   -  Nothing like politicized "science"