International Review of Surveillance and Control of Workplace Exposures: NOHSAC Technical Report 5
3.3 The purpose of occupational health surveillance
Occupational health surveillance is essential for the planning, implementation and evaluation of occupational health programmes, and the control of work-related ill health and injuries (p12). Workers’ health surveillance (i.e. outcomes-focused surveillance in Viner’s time zone 3) involves producing and examining indicators of mortality, work disability/ability, occupational diseases and injuries, work absenteeism, occurrence of symptoms, life-style factors and so on. Surveillance of the work environment (i.e. hazard exposure-focused surveillance in Viner’s time zones 1 and 2) includes the identification and evaluation of environmental factors that have the potential to affect the workers’ health.
Rantanen et al (p12) suggest that surveillance of the work environment includes the assessment of occupational hygiene conditions, work organisation factors that may pose health risks, and collective and personal protective equipment, exposure to hazardous agents, and hazard control systems.
Thus a central purpose of surveillance systems is informing the need for and the type of risk control that will bring about improvement in workplace health and safety. Surveillance enables the formulation of policy that will drive a programme of action that will bring about change, set priorities and evaluate trends. This change may be monitored and measured through the use of indicators (i.e. some measure that may be used to identify change or a characteristic. This is summarised in Figure 3.
Inevitably, work environment surveillance offers greater opportunities to influence risk control that will precipitate earlier reduction in incidence, especially where agents that cause diseases with long latent periods are concerned.
Sabic et al’s review of possible applications of the minimum dataset for NOHSC identified:
“Since valid and representative exposure measurements can be very difficult to obtain, and monitoring of diseases is complicated by the long latency period and other factors, there may be benefit in monitoring measures of safety performance. These could include the proportion of machinery with appropriate exposure controls (e.g., acceptable maximum noise levels or complete enclosure of a process involving volatile substances), the proportion of relevant workplaces with a functioning risk management program to minimise and monitor exposures, and the proportion of relevant workplaces where appropriate personal protective equipment is supplied and used. These process measures have the advantage of being responsive to changes in the workplaces and potentially easier to obtain, through inspection of workplaces or surveys of employers, than direct information on exposure or disease. However, it would be important to choose the measures carefully, as it is possible for such measures to show improvement even though the outcome they are trying to prevent (in this case high exposure leading to disease) has not improved.” (p41)
Later in the same report, the authors suggest other indicators, such as spray booth approvals by WorkCover New South Wales, and the Hazardous Substances Register operated by the Department of Employment, Training and Industrial Relations in Queensland (where each workplace provides details of storages in excess of specified minimums of hazardous substances located on the premises). The results of biological monitoring (e.g. blood levels recorded under lead regulation requirements in Victoria) may also be used (p49). Biological monitoring (rather than biological effect monitoring) is a valid form of work environment surveillance and parallels air sampling in exposure assessment, while having the benefit of accounting for all routes of entry of substances to the body.
Perhaps one of the clearest exemplars of the use of exposure data to monitor changes and trends in risk control is the Singapore Ministry of Manpower’s noise and chemicals exposure surveillance system. Through regular monitoring as required by the Ministry, noise and chemicals exposures have been monitored for several years, facilitating the production of summary reports as shown in Figure 4.
This database seems to make the most comprehensive use of exposure data for the purposes of risk control. Many do not have such an explicit strategy for use of data and thus the link with risk control is less clear. In the past, there have been commentaries on the tendency for hygiene work to focus on risk assessment without adequate link to or emphasis on risk control,[16, 17] and the current literature review suggests that there is still some room for strengthening the linkages.
It is evident from the previous discussion that there is strong support for an increased emphasis on work environment surveillance and that there are opportunities to influence risk control.