I wrote a blog post in 2022 (1.5 years ago) estimating that there were about 400 people working on technical AI safety and AI governance.

In the same post, I also created a mathematical model which said that the number of technical AI safety researchers was increasing by 28% per year.

Using this model for all AI safety researchers, we can estimate that there are now $400\times {1.28}^{1.5}\approx 580$ people working on AI safety.

I personally suspect that the number of people working on AI safety in academia has grown faster than the number of people in new EA orgs so the number could be much higher than this.