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Limitations of Risk Assessment

What is a contaminated site?

Who does what?

Why is it important?

What is risk management?

Risk assessment fundamentals

Risk assessment methods

Limitations of risk assessment

What are RA tiers?


Problem Identification

Receptor Characterisation

Exposure Assessment

Toxicity Assessment

Risk Characterisation

RM Decisions





Risk assessment is one method in a much broader field of risk management. Risk assessment is a process that does not result in a fixed final answer. It is impossible to determine the true magnitude and extent of any actual contamination at a site.

Research on the effects of chemicals on microbes, plants, animals and humans is patchy at best and confounded by factors such as: 

  • Variations in individual and species tolerances to the effects of contaminants; 
  • Environmental conditions and processes affecting the properties of the contaminant such as partitioning, transformation, degradation, temperature, pH, organic material, etc; 
  • Uncertainty in extrapolating study data between species (e.g. using the outcome of animal testing to predict the effect on people) and within species (e.g. using the effects on a specific group of workers such as miners to predict the effect on other groups of people such as children); and 
  • Large information gaps about the effects of contaminant mixtures that might have synergistic, magnifying or other effects. 
  • Large information gaps about the specific mechanisms and processes affecting functions and organs within the body, how these interact, and how they might be affected by a contaminant.

Our understanding of the interactions between affected individual people, plants and animals within a population, populations within a community, and communities within habitats and ecosystems is extremely limited.

As a result, generally the best you can hope for is to determine some basic information about the risks posed by the site. These include: 

  • Whether there are contaminants present at a site and which contaminants are present (although determining all the compounds potentially present where more than one chemical has been released is unlikely to be achieved); 
  • Whether these contaminants are likely to have been contained on-site or might be moving off-site; 
  • What media the contamination has affected including water, soil, air or vegetation; 
  • Whether these contaminants might possibly be having an effect on microbes, plants, animals or humans; and 
  • What type of effect that might be.

However, by making informed, careful, and well-documented decisions through a systematic evaluation process, your ability to gauge the relative impact of a contaminant on receptors can be greatly enhanced, and the possibility of underestimating or overlooking adverse effects can be reduced.


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Page last updated: 01 May 2007

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