Why is this needed?
Smoking is smoking, whether one smokes tobacco or marijuana. Both create second-hand smoke. The impact of second-hand tobacco smoke on the health of others is beginning to be well understood. For example, researchers have found a 26 percent drop in heart attacks in smoke-free communities compared to communities without smoking bans. (1)

Scientists don’t know as much about second-hand marijuana smoke. They do know it contains more carcinogens than tobacco smoke and there is some evidence that it can affect nonsmokers. Research is needed to learn the full impact of second-hand marijuana smoke on nonsmokers, especially on children.

This provision will prohibit anyone from smoking marijuana in any smoke-free area. Research on the effects of second-hand marijuana smoke will be funded by the industry-financed fund described in Provision 5.
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References

1. Lightwood JM, Glantz SA. “Declines in acute myocardial infarction after smoke-free laws and individual risk attributable to secondhand smoke. Circulation. 2009 Oct 6;120(14):1373-9. Also, Meyers DG, Neuberger JS, He J and “Cardiovascular effect of bans on smoking in public places: a systematic review and meta-analysis.” J Am Coll Cardiol. 2009 Sep 29;54(14):1249-55.