Every time I come across to someone who teaches a bad/unsafe way of doing science, it makes me mad. I am not saying everything I do is right and I am not saying everyone I trained is perfect, but as a science teacher, you need to understand what the consequence of not teaching the right way.
This happened when I was doing my Master degree in Biological Sciences. It was about 8 months after I joined the lab that I deiced to do my thesis project when I developed sun-sensitivity. I just could not go under the sun and if I do I developed red rash and my skin would exfoliate (peel). I had never experienced something like that up till then, and every doctor I saw had no idea why it happened to me.
Now that I reflect the experience, I think it might have been the chemicals I was exposed to in the lab. I was dealing with chemicals like CHAPS, SDS powders without any protective ware. I was weighting these chemicals outside the chemical hood. No body told me to use protective ware except I was told "If you need them, we have them".
We also had projects that required arsenite, arcenate, selenate etc and person who was on the project weighted all these chemical outside the hood.
I still remember my supervisor making his coffee using water from a MilliQ in the lab.
This is what happens when you spend so much time in the lab. You become immune to so many things that are actually/potentially dangerous.
Having said that I still respect my supervisor as a scientist even though he might not have been a really good example as a teacher.
I continued to experience the sun-sensitivity condition even after my graduation. It finally went away after 2 years I left the lab.