This pamphlet is the sixth in a series of nine that discuss the Apollo-Soyuz mission and experiments. This set is designed as a curriculum supplement for secondary and college teachers, supervisors, curriculum specialists, textbook writers, and the general public. These booklets provide sources of ideas, examples of the scientific method, references to standard textbooks, and descriptions of space experiments. There are numerous illustrations, as well as questions for discussion (with answers) and a glossary of terms. This booklet is concerned with the radiation hazard in spacecraft, light flashes in the eyes of astronauts, and cosmic-ray effects on bacterial spores, seeds, and eggs. (MA)