The fumes actually make me nauseous basically instantly. My understanding is that modern vehicles can't vent the tank, so when you pump gas in vapor must exit via the same hole that the liquid is going in. So a fillup discharges ~20 gallons of fumes or something.
There is basically always wind where I live. The pumps shut off automatically. So I just turn the pump on and walk over to the curb, upwind from the fumes.