Over the centuries, mankind has slowly reduced the risks and hazards that even as recently as a century ago kept life expectancy to a mere 45 years. Our average life span has improved to 77 years by remarkable progress in public health and safety. But with this improvement has come a demand for greater efforts to improve both life expectancy and the quality of life. The first edition of this book, published in 1982, was a pioneer in the development of logical, yet simple, analytic tools for discussion of the risks which we all face. This new edition, revised, expanded, and illustrated in detail, should be of value both to professionals in the field and to those who wish to understand these vital issues.