Sterilization: past, present, future.

Globally, sterilization protects more couples from pregnancy than any other contraceptive method. However, use of sterilization has grown only gradually and annual rates of adoption remain low. The high prevalence of sterilization can be explained by its excellent continuation rate, its appeal to a broad age range at the time of adoption, and its long history of availability. International patterns show that sterilization users are concentrated in the two large countries of China and India, but numerous smaller countries also have high proportions of couples using the method. Four personal characteristics differentiate its use within each country: age, parity, residence, and sex. A new projection method indicates that approximately 159 million sterilization adoptions are expected between 1990 and 2000, half of them in China. Most future sterilization users will be found where they have been in the past, due to their concentration in China and India and to the large carry-over of current users in all countries. Projections for sterilization are more dependable than are those for other contraceptive methods, because most current users are young enough to remain in the pool of active users for 10 years. They constitute a large component of the expected total in the year 2000--about 269 million users, or 29 percent of all couples.     

Anthrax vaccines: past, present and future.

Most livestock vaccines in use throughout the world today for immunization against anthrax are derivatives of the live spore vaccine formulated by Sterne in 1937 and still use descendants of his strain 34F2. Credit belongs to this formulation for effective control in many countries with considerable reduction, sometimes complete elimination, of the disease in animals and, since man generally acquires it from livestock, in man also. However, there are some contraindications of its use and situations in which it cannot be easily administered, and room for development of a successor is discussed. The human vaccines, formulated for at-risk occupations and situations, date from the 1950s (UK vaccine) and 1960s (US vaccine). The rather greater need for improvement of these as compared with the veterinary vaccine stimulated valuable research during the 1980s which has led to a number of promising candidate alternatives for the future.     

Medicare: past, present and future

The history of the Medicare program, including changes that have been enacted over the years in an effort to control spiraling costs, is reviewed. Medigap insurance and preventive medical care for the elderly are examined, as is the impact of Medicare coverage for the terminally ill. Trends indicate that the Medicare system as presently structured is not financially viable. The question is: what will replace it?     

Saccharin: past, present, and future

Saccharin, first synthesized in 1879 by Fahlberg, has been used as a non-caloric sweetener with several advantages. It is sweet, non-caloric, and stable, can now be synthesized with relatively few impurities, and is inexpensive. Its toxicity, imagined and real, has long been a source of concern and debate. Intensive studies on the potential carcinogenicity of saccharin have been performed, extending the limits of our technology to evaluate carcinogenic risk of chemicals. Saccharin has been found to be a carcinogen only in rats and only if administered over two generations. The effect seems to be directed primarily to the lower urinary tract and is greater in males than in females. Also, saccharin has been found to enhance or promote the carcinogenic process in rat models. The form of saccharin administered in the diet or drinking water has been the sodium salt. No effects have been found with acid saccharin. Epidemiological studies in human beings have not found an increased risk of developing bladder cancer with exposure to saccharin.     

Risk estimates: past, present, and future

Risk estimates for genetic disease developed over the past 30 y have been reviewed. The influence of dose rate and nonlinear dose-response curves on low dose estimates are discussed, and a reevaluation of doubling dose from acute irradiation is presented. The issue of differential sensitivity between human and mouse data are discussed with respect to the lack of an observable induced mutation rate in the offspring of A-bomb survivors. It is concluded that the "presumably" more sensitive mouse-derived risk estimates would not predict a significant increase in F1 abnormalities in humans. Therefore, it may be premature to accept the interpretation that man is less radiosensitive than the mouse.