(a) that the boards of health of not more than three county or part-county health districts or other bodies having the powers and duties of a board of health of a county or part-county health district may appoint the same person to serve as county health commissioner, county health director or, when authorized by the state sanitary code, public health director for said health districts, if the total population of health districts is not in excess of one hundred fifty thousand according to the latest federal decennial census, provided the approval of the commissioner is obtained; or

(b) the board of health or other body having the powers and duties of a board of health of a county or part-county health district of any county health district with a population of less than thirty-five thousand according to the latest federal decennial census may appoint the same person employed by a contiguous county or part-county health district to serve as county health commissioner, county health director or, when authorized by the state sanitary code, public health director without regard to the total population of both health districts, provided the approval of the commissioner is obtained. The commissioner shall periodically review his or her determination to ensure such employment of the same county health director, director of public health or county health commissioner continues to serve the interest of public health and may terminate his or her approval at his or her discretion. 2. If the commissioner has approved the appointment of the same person to serve as the county commissioner of health or public health director of more than one county or part-county health district pursuant to subdivision one of this section, then during the continuation of such approval the commissioner may also authorize the same members to be appointed to the board of health of each respective health district, notwithstanding their residency in the other county. 3. Any boards of health or other bodies having the powers and duties of a board of health of a county or part-county health district having the same members shall annually submit such information and reports regarding the effect of such employment on administration of the respective health districts and the provision of public health services as the commissioner may require. The commissioner shall use such information in determining whether such common membership continues to serve the interest of public health. 4. The county health commissioner or public health director shall possess such qualifications for office as are prescribed in the sanitary code. 5. The county health commissioner or public health director shall serve for a term of six years and shall not be removed during the term for which he or she shall have been appointed, except upon written charges after a hearing and upon notice. 6. The county health commissioner or public health director shall receive such compensation as may be fixed by the board of supervisors or, if the commissioner's approval has been obtained for the employment of the same person as the county health commissioner or public health director pursuant to subdivision one of this section, by the boards of supervisors.