Nothing in this chapter shall prohibit the director of public health as provided herein from acting as health officer for any other city or town within the county, nor from acting as health officer in any adjoining county or any city or town within such county having a contract or agreement as provided in RCW 70.08.090: PROVIDED, HOWEVER, That before being appointed health officer for such adjoining county, the secretary of health shall first give his or her approval thereto.