Are there any brand safety measures for Amazon advertising?

Yes. Amazon utilizes the following practices.

Evaluate each bid request in real-time to detect and block invalid traffic.
Apply proprietary blacklists as well as IAB bot filters and blacklists to avoid poor placements across its ecosystem.
Block unauthorized requests using ads.txt to remove unauthorized reselling and counterfeit inventory from the programmatic supply. The Amazon DSP will block unauthorized publishers from selling impressions on certain third-party exchange inventory.
Use third-party systems and technology such as comScore to verify website environment quality available on the open exchanges (SSPs) as well as pre-bid targeting from IAS, DoubleVerify, and ODC.
Provide advertisers with post-impression traffic and adjacency standards checks
Manually audit inventory for compliance with Amazon’s quality and adjacency standards.
Accept blacklists from advertisers and agencies to weed out any website to steer clear of before the campaign goes live.