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Airway Obstruction and Hypersensitivity among Young Workers: 16 Year Follow- up of Machinist and Construction Apprentices
RS2007-OG04
Final Report Date: December 2010
| Principal Investigator: | Susan Kennedy (University of British Columbia) |
| Kay Teschke, Karen Bartlett, Paul Demers, Anne Marie Nicol, Mark Fitzgerald, Barbara Karlen, Christie Hurrell, Cheryl Peters, Cathy Jensen, Christian Turner, Reid Chambers, Randy Urbanowski, Cornel Lencar, Emily Carpenter, Kathleen McLean, Celine Horner |
For more information about this project, please contact Barbara Karlen.
Issue
In 1988, UBC researchers began a long term study of the development of asthma and other breathing problems in response to irritants and allergens in work environments. They tested four groups of apprentices (machinists, electricians, insulators and painters) at the beginning of the study and two years later to identify early changes in respiratory health. In the latest phase of the study, researchers followed up with over 200 of the original participants to determine whether the breathing problems identified earlier in some of the apprentices were associated with respiratory problems later on. For machinists, the research also examined whether breathing problems were associated with exposures to highly irritating metalworking fluids in the air.
Key findings
- The workers who experienced a sharp drop in lung function or developed new hypersponsive airways during the first two years of apprenticeship were the most likely to develop more serious respiratory health problems later.
- For machinists working in the trade the full 16 years, there was a ‘dose-response’ relationship between their cumulative exposure to metalworking fluid aerosols and decreases in lung function. Based on these results, the researchers conclude that current exposure limits for metalworking fluid aerosols are not sufficient.
- Testing of metalworking fluid aerosols in small machine shops in B.C. indicated that the levels were highest when the shops use grinding or using computer numeric controlled (CNC) machines (even if the machines were fitted with enclosures).
Objectives
- To learn whether lung changes in young workers in response to irritants or allergens at work predict the development of chronic breathing problems later on.
- To evaluate the impact of exposure to metalworking fluids aerosols on the respiratory health of machinists.
Methods
In 1988, the researchers started a long‐term study of apprentices in four trades in BC: machinists, who are exposed to highly irritating metalworking fluids in the air, and three other construction trades which are at lower risk for lung disease from irritants at work (painters, insulators, and electricians). Researchers measured the function and responsiveness of their lungs three times: at the beginning of the study (1988-1990), two years later (1991‐1993), and 16 years later (2004-2006). There were 356 apprentices originally enrolled in the study, and over 200 of those participants were tested in this follow-up phase.
Breathing tests included spirometry, which assesses whether a person’s air passages have become chronically damaged from exposure to irritants, and an airway sensitivity test (methacholine challenge), which measures whether the lungs are overly responsive to short‐term inhalation of irritants or allergens.
Participants also completed questionnaires about their job tasks, work history and respiratory health. For current and former machinists, exposure to metalworking fluids was estimated based on detailed questions about the job and worksite characteristics, and a previously developed model for estimating metalworking fluid aerosol concentration. To update the model, researchers conducted new testing of metalworking fluid aerosols in many small machine shops in B.C.
Data from the respiratory health assessments were also linked with information about whether participants’ visited health providers to get help with asthma or other respiratory conditions. This data linkage was conducted without personally identifying information, to protect the privacy of participants.
Results
First follow-up (two years after baseline testing)
- 30% of all apprentices experienced a substantial decline in their lung function, while a comparison group of marine workers experienced only a 12% decline over the same period.
- Machinists developed more sensitive airways and more asthma than the other apprentices, so their airways were more likely to be irritated by substances they encountered at work.
- 14% of the machinists quit their trade during the first two years of working life, compared with only 1.5% of workers in the other three trades.
Second follow-up (16 years after beginning employment)
- Workers were more likely to develop asthma or other respiratory diseases later on if their two year follow-up testing and questionnaire responses showed early breathing problems such as coughing or wheezing, a rapid decline in lung function, or the development of very sensitive airways.
- For machinists who worked in the trade during the full sixteen years, there was a ‘dose-response’ relationship between decreased lung function and cumulativeexposure to metalworking fluid aerosols.
- Machinists who had lung problems at the second year follow-up continued to have these problems sixteen years later, even if they had quit the trade.
- Workers who quit their trade for health reasons other than injuries were more likely to have been exposed to irritants and allergens at past workplaces, or (for former machinists) to have been exposed to higher levels of metalworking fluid contaminants than other machinists.
Measurements of Metalworking Fluid Aerosols
- The highest air concentrations of metalworking fluid aerosols were linked to grinding and the use of computer numeric controlled (CNC) machines, especially those that are partially or fully enclosed.
Conclusions
The researchers conclude that workers with early breathing problems developed in response to workplace irritants and allergens are more likely to develop asthma and other chronic breathing problems later on.
Based on the dose-response relationship found between metalworking fluids in the air and the development of lung problems for machinists working in the trade long term, the researchers conclude that stronger regulations regarding exposure limits for metalworking fluid aerosols are needed.
The research findings will also be helpful for implementing screening programs in workplaces, and motivating workplaces to minimize exposures to metalworking fluid aerosols, especially those associated with grinding and CNC machining.
Future directions
Areas identified for further research include:
- Conducting additional research to confirm the findings of this project
- Assessing the value of intervening early (e.g., through treatment and/or exposure reduction) when workers experience a large drop in lung function
- Evaluating the impact of control measures to reduce exposure to metalworking fluid aerosols, especially for computer numeric controlled machines
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