If you are speaking of legal matters the Nuclear Regulatory Agency says this is safe for occupational exposure.
5 times your age minus 18 REM per year.
So if you are 20 that would be 2 times 5 which would equal 10 REM (Rad Equivalent Man).
Then the NRC defines the Lethal dose (LD) as:
The dose of radiation expected to cause death to 50 percent of an exposed population within 30 days (LD 50/30). Typically, the LD 50/30 is in the range from 400 to 450 rem (4 to 5 sieverts) received over a very short period.
So safe is probably somewhere in between.
Does that mean that if you get old enough you’re immune to radiation?