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ENVIRONMENTAL EXPOSURE ASSESSMENT<br />

considered. The same applies to anaerobic conditions in l<strong>and</strong>fills <strong>and</strong> treatment of sewage<br />

sludge. Salinity <strong>and</strong> pH are examples of other environmental conditions that may influence the<br />

degradation.<br />

In the risk assessment a proper functioning of waste treatment is assumed. However, if thermal<br />

treatment of waste is operated at insufficient <strong>technical</strong> conditions, organic substances may be<br />

<strong>for</strong>med having a PBT 1 or POP profile. This may be the case in particular in the presence of<br />

halogens (Cl <strong>and</strong> Br) <strong>and</strong> catalysing metals (e.g. copper). If the <strong>for</strong>mation of PBT or POP<br />

substances is identified as a special concern, this should be noted in the risk assessment. In that<br />

case it could be considered to add an appendix to the risk assessment report with further<br />

in<strong>for</strong>mation on the possible <strong>for</strong>mation of substances with a PBT or POP profile.<br />

2.1.1 Measured / calculated environmental concentrations<br />

No measured environmental concentrations will normally be available <strong>for</strong> new substances.<br />

There<strong>for</strong>e, concentrations of a substance in the environment must be estimated. In contrast, the<br />

exposure assessment of existing substances does not always depend upon modelling. Data on<br />

measured levels in various environmental compartments have been gathered <strong>for</strong> a number of<br />

existing substances. They can provide the potential <strong>for</strong> greater insight into specific steps of the<br />

exposure assessment procedure (e.g. concentration in industrial emissions, “background”<br />

concentrations in specific compartments, characterisation of distribution behaviour). The specific<br />

<strong>guidance</strong> <strong>for</strong> existing <strong>and</strong> new chemicals given below should also be applied in general <strong>for</strong><br />

biocides.<br />

In many cases, a range of concentrations from measured data or modelling will be obtained. This<br />

range can reflect different conditions during manufacturing <strong>and</strong> use of the substance, or may be<br />

due to assumptions in or limitations of the modelling or measurement procedures. It may seem<br />

that measurements always give more reliable results than model estimations. However, measured<br />

concentrations can have a considerable uncertainty associated with them, due to temporal <strong>and</strong><br />

spatial variations. Both approaches complement each other in the complex interpretation <strong>and</strong><br />

integration of the data. There<strong>for</strong>e, the availability of adequate measured data does not imply that<br />

PEC calculations are unnecessary.<br />

For existing substances, the rapporteur should initially make the generic “reasonable worst-case”<br />

exposure assessment based on modelling, to derive an EU environmental concentration.<br />

Measured data, i.e., site-specific or monitoring in<strong>for</strong>mation, can then be used to revise the<br />

calculated concentrations. Other site-specific in<strong>for</strong>mation such as effluent volumes, size of STP,<br />

river flow etc. may also be useful. In carrying out this revision, the rapporteur is recommended<br />

to include in the exposure assessment of existing substances, a table containing availability of<br />

site-specific in<strong>for</strong>mation <strong>for</strong> each production site (if limited in number) or group of production<br />

sites (if numerous), as far as confidentiality issues allow. The “site-specific” concentrations<br />

estimated may involve the use of actual site-specific in<strong>for</strong>mation <strong>and</strong> more generic values (<strong>and</strong><br />

possibly extrapolated values as described below). The rapporteur should then consider in which<br />

cases extrapolation is possible from sites with site-specific in<strong>for</strong>mation to a site without<br />

in<strong>for</strong>mation. Aspects to consider here include the proportion of the industry covered by specific<br />

in<strong>for</strong>mation, the nature of the industry <strong>and</strong> in<strong>for</strong>mation about its distribution, the comparative<br />

size of sites, the types of process used etc. The rapporteur should justify in the risk assessment<br />

1 Substances being persistent, bioaccumulative <strong>and</strong> toxic (PBT) or substances classified as a persistent organic<br />

pollutant under the UN Stockholm Convention on Persistent Organic Pollutants.<br />

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