My grandaughter is 2 next month and my son and his partner smoke weed around her every day and so do all her family when they there. Wot are effects?

Not good. While i was learning about perinatal addiction (infants of subtance-abusing mothers), i visited some prostitutes who showed me how they blew marijuana smoke up their babies/toddlers noses to keep the children quiet while they were..Uh, busy with their customers. There is no way being " stoned" helps a child's development, report this to child protective services. Cps will not divulge your name.
Not Good. Unless you think it is good for your granddaughter to be stoned, she should not be exposed to smoke. Since her lungs are very efficient she will adsorb what ever is in the air more readily. Marijuana will affect her lungs and the psychoactive effect will alter her brain development. She cannot choose to avoid this, this is child abuse. This should be reported to child welfare authorities.