In this page we take you through the Tier
process for XYZ Enterprises including problem identification, receptor
characterisation, exposure assessment, toxicity assessment, risk
characterisation, environmental risk management decisions.
Further ERA work is only likely to be required in a very small
number of sites, particularly where there is a significant ecological impact and
remedial actions are either very difficult or not possible, too expensive, or
could themselves result in unacceptable impacts.
At this tier, site-specific assessment criteria need to be
established through an extensive review of existing ecotoxicological data
including, if necessary specific ecotoxicity testing.
The assessor would determine the specific contaminants of
concern, the specific pathways by which the contaminant/s is/are conveyed, and
the specific receptor (usually down to species) that are known to be affected by
contaminants at the concentration measured.
At this tier you will need to have determined that the
receptor is present, and have undertaken an extensive review and field survey to
assess its habitat condition, behaviour, sensitive life stages and diet.
Having determined how the receptor might be exposed (e.g.
dermal, inhalation, ingestion, etc.), the exposure assessment would focus on the
predicted level of exposure. For example, where diet is the primary pathway for
exposure, the potential body burden of a sensitive life stage (e.g. juvenile
fish) will be determined based on the likely number/weight of prey (e.g. aquatic
insect larvae) it is likely to eat, and the amount of contaminant present in the
At this tier the assessor will have quite specific
information on the receptor of concern and how the receptor is likely to be
exposed to the contaminant. The toxicity assessment will build on that
information to establish a specific dose response relationship. While it is
possible that a toxicity assessment could be achieved at this tier through
literature review, specific testing may be required to establish this
At this stage, the assessor will be able to predict the likely
effect of the known contamination on a specific receptor through a given
pathway. The significance of this exposure is likely to be expressed in
quantitative probabilistic terms and in many cases uncertainties may also be
able to be expressed in quantitative probabilistic terms.
At this tier the information that is available, and the way
the risk is characterised, may be very technical and the assessor may need to
explain the results of this tier of assessment in more simple terms.
Risk management decisions taken at this stage should follow a
similar path to those described previously. Due to the intensive nature of the
assessment at this tier, Risk Management Decisions will most likely involve
consultation with or input from other parties such as the site owner or