We could have a debate about whether this is a good way to do things, and surely it could be improved, but it has worked not too badly in the past.
I think this is a little different though. The IARC is publishing a review of the literature, but it is both the author and the publisher. As such there's no intermediate, outside and independent step, and they should be extremely transparent about how they came to their conclusions. They should have reams of studies cited, and they should detail exactly how they weigh contrary strands of evidence. Simply saying, "it was sponsored by industry" is an inappropriate reason to eliminate a study. Again, each study stands on its own data, cited sources, and arguments. Be more critical if you don't trust the source, but consider the data and arguments.
I'm struck by how the IPCC seems to operate by casting a wide net for experts and striving to build a consensus everyone can get behind, and sign their name to. Shouldn't the IARC work the same way?
If the reasoning process is not thoroughly detailed in the original monograph, they absolutely should release an anonymized version of the deliberations.
A hazard is something that can harm potentially harm you. Risk quantifies how likely that will happen.
Edit: wording
Show me the data!
If I can examine it and reach the same or a different conclusion, then we can begin a real discussion on why. That's science.
The point is that the intermediate drafts of the evaluation itself do not need to be public and it's fair to deliberately keep them in the circle of people who are working on it or reviewing it.
What should be open is the final reasoning, the results and data that go into a conclusion. But the process of getting there should allow people to make all sorts of mistakes until they get it right, without facing undue scrutiny during that process.
There are far too many biased groups that will take any indication of a simple arithmetic error that gets corrected as a sign of corruption or manipulation.
In mathematics, a proof shows all the work, but you don't have to show all your failed attempts until you get to a proof. I don't think that these scientists should be treated differently.