the combo of joos and tweed has no effect. well not on me anyways. i had to get a vasectomy to stop my swimmers. basically your friend is full of shit.
people hear what they want to hear. this has been disproven many times, but your friends will still quote old medical studies, and then discredit newer studies to the contrary.
assuming fecal matter is not present on the seat, not much, there are millions less germs on the toilet seat than the door knob going into most building.
I was having a convo with someone about MJ affects and they said it affects the quality of sperm, not just quantity. Meaning if youre a man and smoke MJ, you could give your child birth defects. Is this true?