No abstract

Late effects of continuous exposure to ionizing radiation are potential hazards to workers in radiation facilities as well as to the general public. Recently, low-dose-rate and low-dose effects have become a serious concern. Using a total of 4000 mice, we studied the late biological effects of chronic exposure to low-dose-rate radiation as assayed by life span. Two thousand male and 2000 female 8-week-old specific-pathogen-free (SPF) B6C3F1 mice were randomly divided into four groups (one nonirradiated control and three irradiated). Irradiation was carried out for approximately 400 days using (137)Cs gamma rays at dose rates of 21 mGy day(-1), 1.1 mGy day(-1) and 0.05 mGy day(-1) with total doses equivalent to 8000 mGy, 400 mGy and 20 mGy, respectively. All mice were kept under SPF conditions until they died spontaneously. Statistical analyses showed that the life spans of mice of both sexes irradiated with 21 mGy day(-1) (P < 0.0001) and of females irradiated with 1.1 mGy day(-1) (P < 0.05) were significantly shorter than those of the control group. Our results show no evidence of lengthened life span in mice continuously exposed to very low dose rates of gamma rays.

Epidemiologic studies have been playing frontier roles to explore determinants of sarcoidosis by observing affected persons with the related population. Since 1990, more than 100 epidemiologic papers have been added to the Medline and PubMed databases. Of them, just a few were dated after March 2001. This article is focused on the papers after that time, referring to a number of previous important epidemiologic studies. The review is arranged according to two major epidemiologic categories: (1) host-related findings such as age, sex, race, familial clustering, and lifestyle; and also (2) time- and space-related findings such as exposures, geographical variation, local clustering, climate and seasonal variation, migration, and time-space clustering (transmission).