If marijuana were a serious toxicity, you would have heard about it more. Up to 1 in six people experience significant asthma symptoms with smoking marijuana. This is while they are smoking and it goes away rapidly when they are not. In cigarettes, there is worse lung function WHILE smoking. Otherwise, the effects from smoking do not reverse quickly at all. In cigarettes it is months after quitting before significant healing occurs. Best is strengthening the diaphram with incentive spirometry which will have some improvement in 2 weeks in breathing ability. Information on how long marijuana is in the body, other long term effects of it would be a different question; obtainable with a premium direct question.