Does having a certified occupational health and safety management system lead to a greater injury rate reduction?

This study examines whether formal certification of an occupational health and safety management system leads to measurable safety improvements in practice. Focusing on Ontario’s Certificate of Recognition (COR) program, the findings show that certified firms generally experienced greater reductions in serious workplace injury rates than similar non-certified firms. The strongest benefits were seen in larger firms, more recently certified firms, and especially those in the construction sector, while smaller firms and non-construction firms saw much less benefit.

Summary
The study concludes that certified occupational health and safety management systems can contribute to meaningful reductions in workplace injury rates, but their effectiveness depends heavily on context.
Firms that achieved COR certification had greater reductions in lost-time and high-impact injury rates than comparable firms that did not become certified.
However, the benefits were not uniform. The strongest improvements were found in larger firms, construction firms, and those certified more recently, while no clear benefit was found for non-construction firms or for no-lost-time injuries.
The report’s major finding is that COR certification was associated with a 28% greater reduction in lost-time injury rates and a 20% greater reduction in high-impact injury rates compared with matched non-certified firms. This suggests that formal safety management certification can improve safety performance, particularly where firms have the scale, structure, and sector conditions that support effective implementation.
A key insight is that certification does not appear to work equally well for all employers. Small firms may face practical barriers such as limited resources, simpler management structures, and tighter operating margins, which can reduce the impact of a formal management system. Likewise, firms outside construction did not show the same measurable gains, suggesting that the program may be best suited to environments where COR is already well integrated into procurement and operational expectations.
Overall, the study argues that COR is a promising intervention for improving workplace safety, especially in large construction firms, but it is not a one-size-fits-all solution. The authors also caution that some of the observed benefit in construction may partly reflect selection effects, since COR increasingly became a pre-bid requirement for publicly funded infrastructure work.

Aim & Context
The study explored whether firms that obtained occupational health and safety management system certification through Ontario’s COR program achieved greater injury rate reductions than similar firms that did not become certified.
It was designed in response to ongoing uncertainty in the research literature about whether certified safety management systems actually reduce workplace injuries.
The authors also placed the study in the context of growing international use of OHSMS standards such as OHSAS 18001 and ISO 45001, noting that previous research has shown mixed results and that stronger evaluation methods are needed.

Methodology
The study used a matched difference-in-differences design.
It linked firm-level and claim-level data from Ontario’s Workplace Safety and Insurance Board with COR registration data from the Infrastructure Health and Safety Association for the years 2009 to 2020.
Certified firms were matched with similar non-certified firms using coarsened exact matching, based on industry classification, firm size, assessment year, and pre-baseline lost-time injury rate.
The analysis included 346 certified firms matched with 310 non-certified firms. Population-averaged negative binomial regression models were then used to assess whether certification was associated with changes in injury rates over time.
Three firm-level injury outcomes were examined:
•    Lost-time injury claims
•    High-impact injury claims
•    No-lost-time injury claims

Key Findings

1. COR certification reduced more serious injury rates
Firms that became COR certified experienced stronger reductions in more serious injury outcomes than similar non-certified firms.
Certification was associated with a 28% greater reduction in the lost-time injury rate and a 20% greater reduction in the high-impact injury rate.

2. No clear effect was found for no-lost-time injuries
The study found no reduction in the no-lost-time injury rate associated with certification.
This suggests that COR may be more effective in reducing more serious injuries than less severe incidents requiring treatment but not time away from work.

3. Larger firms benefited more than smaller firms

The impact of certification was stronger in larger firms.
Large firms appeared better able to translate certification into measurable safety gains, likely because they have more resources, more formal structures, and greater capacity to implement and maintain management systems effectively.

4. Construction firms drove most of the positive effect
Most of the observed benefit came from firms in the construction sector.
Non-construction firms did not show the same measurable improvements, indicating that COR in Ontario is especially effective in the sector where it is most embedded and most commonly used.

5. More recent certification appeared more effective
The findings suggest that COR’s effectiveness strengthened in more recent years.
The authors interpret this as possible evidence of program maturation, improved implementation, or stronger alignment between the program and industry practice over time.

Takeaways for Practice
Certified safety management systems can improve workplace safety, but they work best when firms have the resources and operating environment to support them.
For large construction firms, COR appears to be a practical and effective tool for reducing more serious workplace injuries.
For smaller firms, a formal certification model may be less effective on its own, and alternative or more tailored approaches may be needed.
Policymakers, regulators, and industry associations should be cautious about assuming that certification has the same value across all sectors and firm sizes.
The study also suggests that future evaluations should look more closely at procurement effects, firm selection into certification, and the specific audit and implementation features that make certification more or less effective.

Read the full research study here:
Macpherson, R. A., & McLeod, C. B. (2026). Does having a certified occupational health and safety management system lead to a greater injury rate reduction? An evaluation of the Certificate of Recognition program in Ontario, Canada. Journal of Safety Research, 97, 1–8. https://doi.org/10.1016/j.jsr.2026.01.017