unions do more than just strong-arm negotiation.
"While union representation is not a magic bullet to workplace safety problems, there is little doubt that it makes a positive difference. A recent report surveying the construction industry published by the Illinois Economic Policy Institute based on publicly reported OSHA data found that union worksites are 19% less likely to have an OSHA violation and had 34% fewer violations per OSHA inspection than non-union worksites. Overall, while unions represent 14% of the construction industry employees, their employers account for only 5% of the industry’s OSHA violations."
https://blog.dol.gov/2022/05/11/the-connection-between-unions-and-worker-safety