Absence of conflict of interest.
Citation
Highlights
- The study's objective was to examine the impact of plumbing apprenticeship programs on occupational health and safety among journey level plumbers.
- The authors used a statistical model to compare the occupational illness and injury outcomes for journey level plumbers who had either completed a plumbing apprenticeship, participated in some apprenticeship training, or had not had any apprenticeship training. The study relied on the State of Washington's data on licensed plumbers, registered apprentices, workers’ compensation claims, and unemployment insurance, covering the period from January 1, 2000 through December 31, 2018.
- Journey level plumbers who completed a plumbing apprenticeship had lower rates of workers’ compensation claims and lower rates of wage replacement/disability claims, compared to journey level plumbers with no apprenticeship training.
- The quality of causal evidence presented in this report is low because the authors did not ensure that the groups being compared were equivalent, aside from whether they received the intervention. This means we are not confident that the estimated effects are attributable to completing a plumbing apprenticeship; other factors are likely to have contributed.
Intervention Examined
Apprenticeship Programs for Plumbers
Features of the Intervention
Apprenticeship programs combine on-the-job training from an experienced professional with supplemental instruction, such as classroom instruction or online courses, to train individuals in a specific trade or profession. Apprenticeship programs are governed by specific state and federal regulations, which include the requirement to provide training and instruction on workplace safety. In the State of Washington, all journey level plumbers must be licensed and certified by the Washington State Plumber Certification Program. Plumbers complete these requirements by working 8,000 hours as a trainee under a current journey level plumber, completing 8 hours annually of continuing instruction, and passing a state exam. Although not required, some journey level plumbers fulfill these requirements by participating in a plumbing apprenticeship program.
Features of the Study
The study authors used a regression model to compare occupational injuries and illness rates for journey level plumbers who had either completed a plumbing apprenticeship, participated in some apprenticeship training, or had not had any apprenticeship training. The study authors also compared rates of workers compensation claims in the five years prior to journey level certification and in the years following journey level certification, across the three apprenticeship participation statuses.
The study used data from the State of Washington over the period beginning on January 1, 2000 through December 31, 2018. Information on licensed journey level plumbers and apprenticeship program participation was collected from databases maintained by the Washington State Department of Labor & Industries. Information on employment was collected from the Washington Unemployment Insurance database. Information on workers’ compensation claims was collected from the Washington workers’ compensation claims database.
Between 2000 and 2018, 4,086 plumbers in Washington State obtained an initial journey level certification. Of these, the study sample included 3,327 journey level plumbers with wage and hour data reported in the Washington Unemployment Insurance database. The study sample consisted of 768 journey level plumbers who had completed an apprenticeship program, 357 journey level plumbers who had received some apprenticeship training, and 2,202 journey level plumbers who had received no apprenticeship training.
Journey level plumbers who had completed a plumbing apprenticeship or received some apprenticeship training were on average younger at the time of their initial journey level certification (32 and 35 years old, respectively), compared to those who did not participate in any apprenticeship training (38 years old at the time of initial certification).
Findings
Health and Safety
- Study findings suggested that during the years that they held a journey level plumbing license, journey level plumbers who had completed an apprenticeship program had lower rates of accepted workers’ compensation claims, lower rates of wage replacement/disability claims, lower rates of workers’ compensation claims for acute injuries, and lower rates of workers’ compensation claims for musculoskeletal injuries, compared to those who had no apprenticeship training.
- Study findings suggested that compared to claim rates prior to holding a journey level plumbing license, journey level plumbers who had completed an apprenticeship program saw larger percent declines in rates of accepted workers’ compensation claims and in rates of claims for acute injuries, compared to those who had no apprenticeship training.
- The study did not detect statistically significant differences in health and safety outcomes for journey level plumbers who had completed an apprenticeship program, compared to journey level plumbers who had participated in some apprenticeship training.
Considerations for Interpreting the Findings
In their regression model, the study authors adjusted for age at journey level certification, the year of initial certification, the number of hours worked per quarter, the number of employers a plumber had while working as a journey level plumber, the size of employer, whether the plumber held an additional license for a plumbing specialty, and workers’ compensation claim rate in the five years prior to journey level certification. However, the authors do not include statistical controls for other potentially important individual-level characteristics such as race, ethnicity, and gender, that could have contributed to the difference between outcomes for journey level plumbers who had completed an apprenticeship program and those who had not participated in an apprenticeship program.
Causal Evidence Rating
The quality of causal evidence presented in this report is low because the authors did not ensure that the groups being compared were equivalent, aside from whether they received the intervention. This means we are not confident that the estimated effects are attributable to completing a plumbing apprenticeship; other factors are likely to have contributed.