D or equivalent doctoral degree or 3 full years of progressively higher level graduate education leading to such a degree, or LL.M., in one of the following fields of study: safety or occupational health fields (safety, occupational health, industrial hygiene), or degree in other related fields that included or was supplemented by at least 24 semester hours of study from among the following (or closely related) disciplines: safety, occupational health, industrial hygiene, occupational medicine, toxicology, public health, mathematics, physics, chemistry, biological sciences, engineering, and industrial psychology. Combination: Combinations of successfully completed post-high school education and experience may be used to meet total qualification requirements for grade levels GS-11 and may be computed by first determining the applicants total qualifying experience as a percentage of the experience required for the grade level; then determining the applicants education as a percentage of the education required for the grade level; and then adding the two percentages.