I think if you google Forest Service marking paint study it might pop up. It was done during the 1990s and the results are not exactly concise. They monitored timber marker's hair for bad stuff. Some came to work with higher levels of paint chemicals after a weekend off but had spent the weekend painting their house. So, one kind of decides for oneself. I've had guys who smoked demanding respirators to mark in. They did not want them when they found out they'd have to shave off their beards. I know of two women who had non-normal babies. One was terminated early after it was determined to be brain dead and have other major problems, the other was born with Down's Syndrome . That isn't conclusive either. One of those couples then had a normal kid. Most timber markers I know of have healthy kids. It is a long read though. Suitable for a nasty weather day.