Construction trade workers are at significantly increased risk of developing occupational lung disease that involves a restrictive spirometry pattern (RSP) due to exposure from hazardous materials, according to a recently published study in the American Journal of Industrial Medicine. Restriction happens when the lungs become stiff after inhaling dust over time, which causes scarring that reduces the person’s ability to breathe in.
The study and others like it could change the medical approach to these types of diseases and point to the need for more preventive measures for workers, said John Dement, PhD, professor emeritus in Duke’s Occupational & Environmental Medicine Division in the Department of Family Medicine and Community Health, who led the study.
The researchers discovered that 28.6% of 18,145 participating construction workers developed RSP. Results showed those with RSP were at an increased risk of all-cause death, and death from cardiovascular disease, respiratory disease, and lung cancer.
“This is not just a disease of the lung that causes adverse effects. People are actually at increased risk of mortality because of this lung disease,” Dement said.
Dement said the most surprising finding of the study was the high prevalence of RSP in this population and how strongly it's tied to construction jobs. Workers were classified into 16 different construction trade groups. Asbestos workers had the highest prevalence of RSP at 35.3%, followed by teamsters, which are truck drivers, at 32.9%, and boilermakers ranked third with a prevalence of 31.2%. Plumbers, steamfitters, and pipefitters ranked fifth at 29.0%, and electricians ranked seventh at 28.4%.
During this study, Dement and his team performed several cross-sectional analyses aimed at determining risk factors for RSP including how frequently construction trade workers performed tasks that exposed them to hazardous material. Construction workers experience frequent exposures to asbestos, silica (found in concrete), and welding fumes. Those are all substances known to cause interstitial lung diseases. “A lot of exposure that construction trade workers get, comes from the work that they’re doing, but they’re also in the vicinity of all this work being done, so they’re also getting exposure from jobs they’re not doing themselves,” Dement said.
Dement has served as a member of the Department of Energy’s Building Trade Program (BTMed) since 1997. The program provides services and occupational medical exams to construction workers who’ve worked at government-owned, contractor-led sites to detect health problems related to work. In his role, Dement primarily focused on providing the epidemiology, the statistical data analysis, and the industrial hygiene components of this program.
Dement said that one of the biggest risks for construction trade workers developing RSP is inhalation hazards, so the respiratory system is a major focal point of the exam. BTMed has conducted about 44,000 medical exams since its inception. They are performed by occupational medical nurses who gather a detailed work history, and demographic information like race, age, and gender.
A spirometry test is also conducted. It’s a standard breathing test approved by the American Thoracic Society to determine whether there are any abnormalities. Nurses have a person breathe into a machine as deep as they can, then have them blow out as fast as they can to test for two things. First, the machine measures how much air is blown out in one second (FEV1). Dement said most people should be able to blow out 80% of their total lung capacity in that amount of time. Then the machine measures the total amount that’s blown out, which is called the forced vital capacity (FVC).
Results are then compared to data from NHANES, the National Health and Examination Survey. That group is part of the CDC’s National Center for Health Statistics that compiles data on the US population. That data is maintained by BTMed and is used for studies. Dement said they look at the data from a population-based perspective, rather than individually. “The important thing is the worker themselves during the exam, but when you back up and use that information to learn, ‘okay this worker had an asbestos-related disease, and then we can ask well, do all these types of workers generally have an increased risk of asbestos-related disease by looking at the data in total,’” Dement said.
The results from the spirometry test are then divided up into three different categories: obstruction, restriction, or a mix of obstruction and restriction. Workers with obstruction have blocked airways, similar to what happens in people with chronic obstructive pulmonary disease (COPD). Dement said this causes their FEV1 numbers to be lower during the test. While the lung volume is big enough for people in this category, they can’t breathe out the air fast enough.
Restriction, which was the primary focus of this study, reduces lung volume, Dement said, which means a person can’t take in as much air. “Some types of exposure, like asbestos, can also cause disease of the pleural space, which is the lining of the lung,” he said. In workers exposed to asbestos, that can cause two things: the lining can thicken, which is called diffuse pleural thickening, or calcified plaque can develop, which is called pleural plaque. “The presence of this sort of encasing of the lung prevents the lung from expanding all the way,” Dement said.
During the spirometry test, workers in the restrictive category display a very low FVC. “The lungs just can’t expand to that volume in the prediction that’s based on their age and other factors,” Dement said. But, study authors found many of these workers actually have a combination of obstruction and restriction due to the different types of exposure.
Dement said the magnitude of the increased risk of death from RSP is surprising, especially for those in this mixed category. “Those people are really at increased risk of premature mortality due to all of the causes we looked at,” Dement said.
The most common symptoms of RSP reported in workers were cough, phlegm, dyspnea, which is difficulty breathing, and wheezing. Majority of the study population worked in construction trades for an average of 21.5 years. The highest occurrence of RSP was found in those aged 60-69. The highest prevalence was found in former smokers at 29.9%, followed by current smokers at 26.8%. An increase in body mass index (BMI) was also observed in those with RSP.
Dement and the other authors are pushing for RSP to be added to the list of health effects documented among US nuclear weapons workers. He said that would make it easier for workers with RSP to receive compensation from the government. Currently, workers in the national occupational compensation program are given funds once it’s been proven that a job caused an illness, effectively shortening the process. Restrictive impairment is not currently listed as a presumed illness but Dement said the additional classification would simplify the payout process.
Dement believes this study and others like it could change the medical approach to these types of illnesses. “As this body of information is gathered, and the relationships are established, then it translates more into prevention as opposed to trying to treat diseases,” he said. Dement said eliminating exposures by substituting chemicals with less hazardous ones, and providing personal protective gear is a good way to start. “RSP is related to work, and construction workers are at least one group where we have established that increased risk, and there are more,” he added.