Not well understood physics, then it was understood and quickly recognized as dangerous. Nothing was done because of nonexistent regulations and corporate money.
>leaded petrol
Recognized as dangerous to begin with ("December 1922, the US Surgeon General wrote to GM regarding growing concerns that environmental lead would become a serious menace to public health."), huge negative effects in workers noticed almost immediately. Nothing was done because of nonexistent regulations and corporate money. (https://www.damninteresting.com/the-ethyl-poisoned-earth/)
>asbestos
Recognized as dangerous by medical journals as far back as the 30s (About 40 years after it came into widespread use). Nothing was done because of nonexistent regulations and corporate money.
>cigarettes
Recognized as dangerous by medical journals as far back as the 40s. Nothing was done because of nonexistent regulations and corporate money.
>Non-ionizing radiation
Not recognized as dangerous despite every conceivable study being tried multiple times. No link to cancer. Technology has been widely used for a little under a century with no signs of population-level effects. No known mechanism of action (unlike all the others). Regardless, regulations limit human exposure and require standardized testing of all consumer products.