I also think that in recent years, the progressive re-classification of poisons has resulted in whole categories of chemicals being recognised as poisons for different reasons.
As an example, Benzene was a common solvent used in laboratories and industry years ago. During my teens, my neighbour brought a pint milk bottle full of the stuff home from his employers factory. The milk bottle was sealed with a rubber bung. What did he want it for? To clean oil stains off his car using a sponge soaked in solvent. The carcinogenic properties of Benzene were largely unrecognised at the time.
Similarly, lots of people used Carbon Tetrachloride as a solvent until its hepatotoxicity was recognised. You could even buy the stuff to remove the debris left behind on removing a sticking plaster!
I used the Sudan dyes out of 50ml glass stoppered dropper bottles for lipid analysis in school oblivious to their carcinogenic properties.
In recent years though, the dangers of chemical teratogens have come to the forefront. These are toxins that can cause birth defects and development delays and include the Polycyclic Aromatic Hydrocarbons such as Benzopyrene that for years were not really recognised as carcinogenic.
I wouldn't want to go back to those seemingly carefree days of using chemicals though and I think that the HSE keeps the public and scientists safe from lots of very dangerous stuff.