Airways Obstruction From Asbestos Exposure: Methods
The men with asbestosis and the age-matched asbestos-exposed comparison men were from 8,720 workers studied at 47 sites across the United States from California to Florida. The asbestos exposed men (ILO profusion 0/0 and 0/1) were individually matched for age to men with asbestosis (ILO profusion 1 /0 to 3/3) in each smoking category using a computer algorithm. A few current and ex-smokers, older than 65 years, were matched to the next youngest or oldest individual if the match pool for their identical age was exhausted. Most of the men with asbestosis had ILO profusions of 1/0 to 1/2, 3 percent had profusions of 2/1 to 2/3, and only 0.3 percent had profusions of 3/2 or greater.
Many of the workers were active or retired members of the International Brotherhood of Boilermakers, Blacksmiths, Welders, Forgers, and Iron Ship Makers or the United Association of Journeymen and Apprentices of Plumbers and Pipefitters of the United States and Canada. Others were from metal trades and chemical unions. Although responses might differ due to exposures to welding, grinding, painting, paint removal, and sandblasting, the boilermakers and pipefitters were not different from each other or from other trades. inhalers for asthma
Occupational exposure to asbestos had began 15 or more years earlier and lasted at least 5 years. Union business agents sent letters of invitation explaining the asbestos disease screening and pulmonary examinations to active and retired members. Members desiring examinations made appointments with our office. The study was approved by the Human Subjects Institutional Review Board of the University of Southern California. Informed consent was obtained from each worker.
The 370 men without asbestos exposure were a proportional population sample from a large industrial state who were without histories of asbestos exposure. Irregular opacities were present in only 0.5 percent of their chest radiographs. Their pulmonary status had been characterized as referents for a poly-brominated biphenyl-exposed population using identical methods.