One of the goals of the Health Protection Agency (HPA) is to minimise the preventable burden of disease attributable to radiation, chemical, and environmental hazards.

The range and complexity of environmental hazards to which populations are exposed is vast and environmental effects on health are multi-faceted. The World Health Organisation (WHO) Burden of Disease programme estimated that in the UK 18/1000 Disability Adjusted Life Years (DALYs) can be attributed to environmental factors. This corresponds to 14% of the total burden of disease in the UK including 99,400 (WHO 2008) deaths each year. Using similar methods, the HPA (2005) estimated the burden of disease associated with environmental pollutants at around 8-9% of the total burden of disease. This apparent discrepancy is due to different inclusion criteria in the two reports. 

To reduce the complex web of environmental exposures to manageable proportions, there is a need to develop a risk assessment methodology for identification and prioritisation of hazards. This work will objectively and transparently assess environmental hazards and develop a methodology for prioritising the most significant in order to focus scarce resources where the greatest benefit can be realised. It will also result in a prioritisation of environmental hazards that can be used to build up the future Environmental Public Health Tracking (EPHT) programme.

The work is divided into three stages. In Stage 1, a Multi-Criteria Decision Analysis (MCDA) approach is used to prioritise a list of potential environmental hazards. The MCDA approach consists of several steps. The first step defines the criteria against which the environmental hazards will be assessed and compared. The second step rates each environmental hazard against each of the criteria. The third step attaches relative weights  (relative importance) to  each of the  criteria and the final step integrates the ratings of each hazard on each of the criteria with the relative weights of the criteria to provide an integrated score for each environmental hazard for comparing across all the hazards. In Stage 2, the findings of the MCDA exercise are  reviewed by  a panel of stakeholders and experts. Finally in Stage 3, the environmental hazards on the top of the prioritised list will be subjected to detailed quantitative assessments.

It is important to note that environmental health hazards chosen as priorities can change, therefore the methodology is transparent and dynamic and as more data or evidence is available hazards can be updated and re-evaluated using the MCDA model.

Hypothetical example

The objective is to rank 5 hazards (A to E) in terms of 5 criteria ("Robust evidence for risk", "Highly regulated", "Acceptance of risk", "Prospect of intervention", "Acceptance of intervention") using Multi-Criteria Decision analysis (MCDA).

The illustration on this page shows the results of a MCDA software tool used to construct and run the example.  The bottom panel ("Ratings") gives the rating of each hazard on each criterion. The numbers are purely for illustrative purposes. 

The middle panel marked "Weightings" give the relative weights that a policy-maker/decision-maker attaches to each criterion. A weight of zero means that the criterion is ignored and a weight of one is the highest that can be assigned. 

Based on the data in the lower and middle panels (inputs to the MCDA), the top panel gives the overall score of each hazard (outputs of the MCDA). The tool integrates the ratings of the hazard on the criteria with the weightings of the criteria to give an overall score for the hazard.  The hazard with the highest score (Hazard A in this case) would have the highest priority.