Document zQ5w1gV0MdpEGQ1Yn18x8RX2z

19 and the course of the individual's health status or the cause of his death Although the data in these two instances were not exactly similar in form, the inclusion of records from the personnel department at As bestos covering employees who had retired, died or become disabled provided data sufficiently alike for the purpose of the study. From this information it was possible to formulate for both Asbestos and Thetford Mines "cohorts" which could be well defined, should be representative of each group, and could be followed (or a de finite period of time. All of the available experience indicates that the development of asbestosis in less than five years.of exposure must be somewhat rare. Accordingly, the cohorts were defined as including every worker who had a total exposure of five or more years, and who was on the employment rolls at Asbestos or Thetford Mines in 1950. These cohorts were then followed by means of the annual physical ex amination records through a six-year interval, 1950 through 1955. AH data regarding these groups were then tabulated in order to determine the characteristics of the cohorts. For those who survived the entire period, reference was made to the physical examination results and xray findings at the end of the period. Those who had died were tabulated separately and the cause of death corroborated by examination of the death certificates. A further search was made concerning those in the original cohorts who remained unaccounted for when the living and the known dead bad been tabulated. They represent men who had left