lead pipes, to cigarettes to asbestos
I think I disagree on these examples. I don't know that these were all proven safe. And not for very long. Even when they were proven "safe" temporarily, there were some science or medical events that caused concern.
Your idea of "proven-safe" is that they were used for two decades without proof of problems. Those examples fit that standard.
Basically: How does one pursue the truth when direct engagement with evidence is infeasible?
I came to this question while discussing GMO labeling. In this case I am obviously not in a position to experiment for myself, but furthermore: I do not have the time to build up the bank of background understanding to engage vigorously with the study results themselves. I can look at them with a decent secondary education's understanding of experimental method, genetics, and biology, but that is the extent of it.
In this situation I usually find myself reduced to weighing the proclamations of authorities: