However, only one or two studies involving each type of outcome could be found, and all studies in this group were considered to have moderate methodological limitations. These limitations arose largely from the simple study designs that were employed.
In addition to weaknesses of internal validity, three of the four studies involved single workplaces (one with two sites), which makes the direct applicability of the results to other workplaces uncertain. Similar concerns about generalizability arise in the fourth study; it had a 20-workplace sample, but this sample was recruited in the context of a research study in which the refusal rate was high.
The single workplace studies must also be regarded cautiously from the point of reporting bias (favouring ‘positive’ results). While researchers outside the workplace tend not to publish null findings, workplace representatives who champion interventions (and thus have a vested interest in their success) have an even greater tendency not to publish them. All three reports on single workplace interventions appeared to have been authored by workplace champions. The intervention failure rate seen in this small sample of studies (0 per cent) is markedly different than the rate of 67 to 93 per cent reported for quality management systems (Gardner, 2000). There is no reason to expect the failure rate of OHSMSs to be markedly different than that for quality, since many of the issues identified in the context of quality system implementation are relevant to OHS (e.g., management commitment, culture change).
In sum, there is insufficient evidence in the published, peer-reviewed literature on the effectiveness of voluntary OHSMSs to make recommendations either in favour of or against them.
Evidence for the effectiveness of mandatory OHSMS interventions The studies on mandatory OHSMS interventions also indicated consistently positive effects. They suggest that mandatory interventions result in:
increased OHSMS implementation over time;
intermediate effects (e.g., increased HES awareness; improved employee perceptions of the physical working environment and the psychosocial environment; and increased workers’ participation in HES activities);
decreases in loss-time injury rates; and
increases in workplace productivity.
The size of the observed changes in OHSMS development and the decline in injury rate observed are likely of practical importance to stakeholders.
Effectiveness of Occupational Health & Safety Management Systems: A Systematic Review