Was there a denialism effort about lead? As far as I know there just were no regulators to crack down on it back in the day. It’s still used in things where it’s impractical to replace and in theory is disposed of carefully.
With cigarettes, I seem to remember that a branch of the US government declared them unsafe in the 70’s. Academics usually will raise the alarm in a big way if they find something really dangerous and it’s not dealt with swiftly. Legislators can be a different matter (see cigarettes, climate change and so on), but when it comes to food don’t tend to get involved.