i found this on a health website:
"Both marijuana and cigarettes are associated with breaks in the DNA of sperm. The more you smoke, whether it is marijuana or tobacco, the more DNA breaks occur. The effect does not seem to be greater with marijuana. However, marijuana is metabolized in the liver, and unlike tobacco, it can affect the liver over the long term in such a way as to increase estrogen levels. Higher estrogen levels in males can increase the risk of abnormal sperm counts or motility. If your semen analysis is normal, this is not likely an issue"
http://www.ivillagehealth.com/expert...=adid=11499886