Any time people start talking toxins and/or radiation I always like to point out the main factors that drive risk:
1) Toxicity/radiation type - This is how dangerous something is, the higher the toxicity of a potential item the greater likelihood of causing harm.
2) Concentration - This is the amount the person is exposed to. The more exposure the greater likelihood of causing harm.
3) Time duration of exposure - This is the length of time a person is exposed to something in one incident. The greater time, the greater likelihood of causing harm.
4) Chronic or repeated exposure - Some toxins and all radiation can add up over time so that even small exposures that wouldn’t normally be an issue can build over time and cause problems later on down the road.
(There are some toxins which one can build an immunity through repeated minor exposure. For example: Iocaine powder from the Princess Bride :)
I see you are a sections 11 & 12 guy, eh?
I’m a Section 3 and 15 type, myself...