Stanford Report, November 1, 2000
|Exposure to workplace
inhalants increases risk of lung diseases
BY CHARLES CLAWSON
A soon-to-be-published study reports a strong association between obstructive lung diseases and workplace exposures to gases, dust and fumes. In the study, evidence of obstructive lung diseases was manifested by recurrent lung infections, chronic bronchitis, and the need to use bronchodilators, or inhalers. The findings are consistent with those from other air pollution research.
"The study shows that chronic exposure to gases, dusts and fumes may contribute to -- and cause -- chronic respiratory disorders," said the article's senior author, Ware G. Kuschner, MD, assistant professor of medicine at the Stanford School of Medicine. "The study reinforces the importance of preventing exposures to these inhalants in the workplace through engineering controls. And it reinforces the fact that respiratory protection -- including respirators -- should be used by workers whenever there are potential exposures to inhalants."
The retrospective study focused on the records of 517 never-smokers who had pulmonary function tests at the Veterans Affairs Medical Center in Palo Alto between 1986 and 1999. During that period, patients undergoing pulmonary tests were asked to report whether or not they had histories of recurrent lung infections, asthma, chronic bronchitis, or use of bronchodilator inhalers. (Use of the inhalers is a marker for obstructive lung diseases such as asthma, emphysema and bronchitis.)
"We found that patients reporting a history of exposure to workplace inhalants were about twice as likely to report a history of bronchitis, a history of recurrent lung infections, and a history of using bronchodilators," said Kuschner.
In addition, patient records included information about pulmonary physiology from "spirometer" tests during the patients' visits to the lab. Such tests identify lung diseases that cause airflow obstruction, due either to narrowed airways, problems that allow airways to collapse, or fluid in the airways. The three principle causes of such obstructions are asthma, emphysema and chronic bronchitis.
"We found that patients reporting inhalant exposure also showed about a two-fold increase in obstructive lung disease, based on pulmonary function testing," said Kuschner.
No association was found between exposure to inhalants and asthma. "There's a little bit of discordance there," Kuschner said. "Asthma is a little tricky in that people have episodes in which they have normal lung function, and and other episodes in which they have abnormal lung function."
The upshot of the study is that people who work around inhalants -- a definition that even includes dust -- are twice as likely to suffer obstructive lung problems than the greater population. The findings are particularly dramatic because of the study's focus on non-smokers. "We specifically focused on never-smokers," said Kuschner, "in order to eliminate the contribution of smoking to lung disease."
Limitations of the study, according to Kuschner, are important to note. Results were determined retrospectively by responses on a standard questionnaire, in which subjects were simply asked: "Have you ever worked near gases or fumes?" and "Have you ever worked in a dusty place?"
"So, importantly, we have no information about the specific exposures, other than that they were exposed to gases, dusts and fumes," said Kuschner. "Also, we have no specific information on concentration, intensity and duration of the exposure." A further limitation is the potential for "recall bias," a problem based in the observation that patients who have histories of lung diseases may be more likely to recall a history of exposure -- whether accurate or not -- than subjects reporting good health.
To allow for recall bias, Kushner obtained objective evidence of lung problems in the pulmonary function lab during patients' visits. Much of the damage would be unknown to patients, and therefore would not interfere with their recall of lung problems, Kuschner said. "The same patients who gave a history of exposure also happened to have objectively defined deficits," Kuschner said. "Still, some might characterize this as a 'hypothesis generating study,' where follow-up studies would be useful."
The abstract for the article is to be published in the journal Chest and was presented as part of Chest 2000, this year's American College of Chest Physicians Conference, which was held October 22-26 in San Francisco.
Collaborators with Kuschner
include the study's primary researcher, Gordon K. Mak, MD, and
Michael K. Gould, MD. The three authors of the study work in the
division of pulmonary and critical care medicine at the Veterans
Affairs Palo Alto Health Care System.