General space background measurement (inevitable normal radiation from the universe and surface minerals, etc.). ) in Dandong, Liaoning Province, it is about 1~ 1.5mSv/ year (I estimate, unofficial figure).
The warning line of X-ray flaw detector in industrial occasions is generally 15mSv/ year, and it is safe for employees to receive radiation for five consecutive years with an average of no more than 20mSv/ year.
For ordinary people and non-employees, the level below 5mSv/ year can be considered as harmless to health.
Doses above 3000~5000mSv/ year will cause obvious harm to human health.