You're right, but no one knows anything. All science can do is DISprove theories. It can't prove anything.
It can't? Did I miss something? Hasn't science proven gravity, tectonic plates, the atomic weight of hydrogen, molecular structures, chemical bonding, that aspirin eats the stomach lining, that THC is the effective chemical in marijuana, et ad nauseum?
Actually, no. Science hasn't technically proven anything. The scientific method, which I'm sure all of us science dorks are familiar with, stresses that we can only DISprove a theory. All of our findings/conclusions are based merely on the evidence we have currently. There are many things that are "proven" only to be disproved later. The point is...all we can do is provide strong (sometimes seemingly indisputable) correlational evidence that A causes B.
Many of the "teratogens" that are currently called such have no real world chance of causing any detrimental effect to a developing fetus. The tests showing their potential "harm" is performed on naked DNA (which isn't ever the case in humans) and at crazy high concentrations and durations. Most of these are done in vitro as well, which further removes them from real world physiological conditions. Compound A will show 1 base mutation per X nucleotides in naked DNA in vitro at some insane concentration, which is significantly higher "statistically" than the normal rate of mutation in DNA. In essence, this means absolutely nothing...especially in the real world.