On-line Research Tools

Occupational hygienists often have to make judgements about potential exposure to harmful substances (chemical products, dusts, etc.) without being able to take direct measurements. This can be the case when the appropriate measurement tools, financing or time are unavailable. For example, during an overall risk analysis with the goal of establishing the entire catalogue of risks present, exposure levels often have to be estimated in the absence of objective data.

This situation occurs quite frequently for healthcare professionals working in developing countries. They often only have very limited means of measuring exposure to chemical products and dusts. Despite this, judgements and decisions must be made, and these can have important consequences, both on human health and finances.

Thus, decisions tend to be made based on the occupational hygienist's experience, knowledge of the scientific literature and direct personal observations (odours, visible dust, surface deposits, ...). However, without objective data, it is clear that evaluating the concentrations of a pollutant in the ambiant air is an extremely difficult thing to do: it is not like guessing the weight of a parcel or the length of a pole. Estimating an airborne pollutant's concentration is far less instinctive as it is not a part of our daily experience. Nevertheless, occupational hygienists have to make decisions in these kinds of conditions.

Even when accurate exposure measurements can be taken, they are only valid for a precise point in time (and usually on a specific day). Knowing that such measurements can vary significantly and randomly over time, any measurement must be assumed to contain a certain degree of uncertainty.

Another possibility is to take advantage previous measurements taken in other similar situations, revealed in the literature or stored in exposure databases. Occupational hygienists will often do this informally when they must make their decisions based on their professional experience. In this context, the IST makes its database of occupational hygiene measurements available to hygiene professionals (the exposure register).

The IST is currently trying to develop the capability and tools to overcome the difficulties. Its objective is to develop the tools which would allow occupational hygienists to make decisions in less uncertain circumstances. With the current state of knowledge, these tools cannot claim to be perfect or to offer any definitive truths. However, they should allow exposure assessments to be linked to estimations of other, more easily accessible and quantifiable variables, which when combined in a mathematical model can provide and an exposure concentration.

The IST is currently developing three mathematical tools in this field:

  • The UPERCUT skin exposure model, developed in partnership with the University of de Montreal.
  • A two-compartment model, which allows an exposure assessment to be made based on a representation of the workplace in the form of two symmetrical compartments (one close to the NF, the other far from the FF).
  • A modified two-compartment model, which allows an exposure assessment to made based on the above model, but also integrating the fact that the distribution of pollutants is not spread evenly throughout the workspace.
  • An expert Bayesian system, which allows the integration of several sources of information at once, namely: measurements, data from the physical model and historical data from a statistical model.

These tools are available for free, but they come with no performance guarantees. They must thus be considered as experimental tools that are part of a process of improving long-term exposure assessment. They constitute the first step towards a more objective and robust way of estimating exposure by occupational hygienists. The intention is also to promote professional discussions and exchanges in the field of occupational hygiene.