Always cover your ass. Every "This is illegal" or "This is unsafe" email needs to be BCC'd to your private email adres.
I've had a company hire me as an indpendant consultant, because the law says they need someone qualified to check their waste management plans. Their plan basically said "We'll take one scoop of polluted soil, and mix it with the clean soil, making sure to stay under the legal limits for clean soil". I told them that was really, really illegal, would cost them their license, would cost me my license, and would cost every person who signed it several thousands of euro's personally. I also email them.
4 months later, I get inspectors ringing my doorbell, holding up the plan I very definitely didn't sign, with what absolutely was my signature. If I didn't have those emails, I'd be royally fucked. With those emails, we could add fraud to the charges.