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2 ENVIRONMENTAL EXPOSURE ASSESSMENT
2.1 INTRODUCTION
ENVIRONMENTAL EXPOSURE ASSESSMENT
The environment may be exposed to chemical substances during all stages of their life-cycle
from production to disposal or recovery. For each environmental compartment (air, soil, water,
sediment) potentially exposed, the exposure concentrations should be derived. The assessment
procedure should in principle consider the following stages of the life-cycle of a substance:
• production;
• transport and storage;
• formulation (blending and mixing of substances in preparations);
• industrial/Professional use (large scale use including processing (industry) and/or small
scale use (trade));
• private or consumer use;
• service life of articles;
• waste disposal (including waste treatment, landfill and recovery).
When assessing the exposure of the environment to existing chemicals, previous releases of the
chemical to the environment need to be considered. These releases may have a cumulative effect
that gives rise to a “background concentration” in the environment.
Exposure may also occur from sources not directly related to the life-cycle of the substance
being assessed. Examples of such sources are substances of natural origin, substances formed in
combustion processes and other indirect emissions of the substance (e.g. as by-product,
contaminant or degradation product of another substance). These kinds of sources have been
referred to as “unintentional sources”. Guidance on how to deal with emissions not covered by the
life-cycle of the priority existing substance or biocidal active substance is given in Appendix XIII.
In view of uncertainty in the assessment of exposure of the environment, the exposure levels
should be derived on the basis of both measured data, if available, and model calculations.
Relevant measured data from substances with analogous use and exposure patterns or analogous
properties, if available, should also be considered when applying model calculations. Preference
should be given to adequately measured, representative exposure data where these are available
(Sections 2.2.1 and 2.5).
Consideration should be given to whether the substance being assessed can be degraded,
biotically or abiotically, to give stable and/or toxic degradation products. Where such
degradation can occur, the assessment should give due consideration to the properties (including
toxic effects) of the products that might arise. For new substances, it is unlikely that information
will be available on such degradation products and thus only a qualitative assessment would
normally be possible. For existing substances and biocidal active substances, however, known
relevant degradation products should also be subject to risk assessment. Where no information is
available, a qualitative description of the degradation pathways can be made. A summary of
some of these is presented in Appendix X. Furthermore it should be noted that guidance on how
to assess and test relevant metabolites and transformation products is under preparation for plant
protection products under Directive 91/414. This guidance could be modified later for use for
biocides, and where appropriate for new and existing substances.
For many substances available biodegradation data is restricted to aerobic conditions. However,
for some compartments, e.g. sediment or ground water, anaerobic conditions should also be
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