It is not in any way related to my own area of research, I looked into it as a parent wondering what would be best for my own kid. However, there is not really that much research out there on this- so I was able to review much of the primary research, as well as various review articles that try to consider all of it together.

How would you define "domain of expertise"? Reviewing literature from other fields I don't research myself and forming an opinion on how it applies to my research is part of my job and something I do almost every day. I am even also called upon to peer review articles and grant proposals that are not within my direct field of research, as is general practice to get "outside opinions."

In cases like this, I am able to be familiar with basically everything published on the issue. However an actual researcher in a specific field will have additional knowledge and opinions from firsthand experience, that cannot be found in literature.

In general, I think it is okay to have your own opinion on something even if you aren't e.g. a professional whose whole life is focused exactly on that one issue. No formal training, credentials, or firsthand experience are necessarily required to have an informed opinion. However, you still have the burden of making sure you really understand the issue deeply - which is probably something like 100x the effort most people think it would be. Anyone can do that if they take the time to do so. I wish more people would.

In any case, this was a few years back when I looked into it, and it seems like these concerns have become more mainstream and less controversial in the last few years, e.g. https://ntp.niehs.nih.gov/publications/monographs/mgraph08

It’s totally reasonable to make this as a simple risk balancing decision: “unknown but probably small risk, vs. known and definitely small benefit” is not the kind of fact pattern that we should persecute people for differing on.