It's a leap in logic to go from "PFAS impairs reproductive health" to "PFAS is a significant contributor to fertility decline". Your bayesian logic does not make sense. We know of dozens of other factors that are also casually known to lower fertility, and are pervasive in our society/environment. They can be contributors, but they can't all be significant contributors.
Again, repeating my prior comment: I'm not claiming PFAS generate zero effects on fertility. I claiming that there isn't good evidence that it's a significant factor in fertility decline.
Makes a lot of sense!
Note, this doesn't necessarily mean that we should do nothing about PFAS. We just have to be honest about the potential impacts. In other words, instead of gesturing that PFAS is the primary cause for fertility decline in the past few decades (like the linked scientific american article), you admit that the impact is unclear/low, but we should still work to remove it just in case.
Because it's the best available theory and even if it's wrong we're eliminating known toxins from our environment?
What other theories have an established mechanism of action and established population-scale exposure? That's why this one should be prioritized above others (at least any that I'm aware of?). Which other theory has these?
Looking at those two pieces of information alone, it’s naive to say “well we haven’t conclusively drawn a causal population-scale link between cause and effect.” It is incredibly difficult to eliminate all confounders at that scale and time horizon, which would be really dooming to the hypothesis if we didn’t already have separate knowledge of the mechanics.
The Bayesian priors are: PFAS are poisonous to humans (known). PFAS are everywhere in our environment (known). We are seeing population-scale effects similar to what you’d expect to see from population-scale PFAS poisoning (noisy).
The difficulty of finding sound causal links at generational, population scales cannot prevent us from taking action on things — again — we already know are poisonous to people and to which people are frequently exposed.