"Despite our findings that 30% of the children in our study tested positive for drugs of abuse in their hair, we found that the vast majority were in good health at the time of examination, which was within 1 to 2 weeks from their removal from their homes [in which marijuana was grown]. The rates of the mostly minor health issues observed were well within the range expected in Canada and other developed countries."

Source

Moller, Monique; Koren, Gideon; Karaskov, Tatyana; and Garcia-Bournissen, Facundo, "Examining the Health and Drug Exposures among Canadian Children Residing in Drug-Producing Homes," The Journal of Pediatrics (Cincinnati, OH: July 2011), p. 3.
http://www.ncbi.nlm.nih.gov/p…