SC
UNEP/POPS/POPRC.4/INF/3
Distr.: General
2 September 2008
Stockholm Convention
on Persistent Organic
Pollutants
English only
Persistent Organic Pollutants Review Committee
Fourth meeting
Geneva, 13–17 October 2008
Item 3 (b) of the provisional agenda*
Operational issues: Toxic interactions between
persistent organic pollutants
Toxic interactions between persistent organic pollutants
Note by the Secretariat
1.
Paragraph (b) of Annex E of the Stockholm Convention lists a “hazard assessment for the
endpoint or endpoints of concern, including a consideration of toxicological interactions involving
multiple chemicals” as an element of the risk profiles to be prepared by the Committee.
2.
At its third meeting, the Committee took note of the considerable discussion on risk profiles and
toxic effects and requested the Secretariat to make arrangements to further the discussion on the subject
of toxicant interactions, and in particular, to arrange for a presentation to be made during its fourth
meeting.1
3.
In response the Secretariat coordinated with Mr. Henk Bowman (South Africa) and Mr. José
Tarazona (Spain) to develop a concept note on the topic to guide the discussions during a plenary
presentation and a side event. The concept note is included in the annex to the present note.
4.
Mr. Marco Vighi from the University of Milan (Italy) has been invited to give a presentation on
the subject during the fourth meeting.
5.
A side event on toxicant interactions will be organized during the lunch period on Monday,
13 October, at which Mr. Rolf Altenburger, Helmholtz Centre for Environmental Research-UFZ
(Germany), and Mr. Vighi will give further presentations on the subject.
*
1
K0841719
UNEP/POPS/POPRC.4/1.
UNEP/POPS/POPRC.3/20, para 106.
xx0908
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meetings and not to request additional copies.
UNEP/POPS/POPRC.4/INF/3
Annex
Concept note on toxicological interactions
I.
Background
1.
If, under Annex D of the Convention, a chemical has been judged to have persistent organic
pollutant characteristics such that it warrants further consideration, then the Committee undertakes a
more in-depth assessment of the chemical under Annex E.
2.
The topic of toxicological interactions, within the scope of the Committee’s deliberations, is
specified in paragraph (b) of Annex E, i.e., “Hazard assessment for the endpoint or endpoints of
concern, including a consideration of toxicological interactions involving multiple chemicals”.
3.
The Committee has yet to deal with toxicological interactions with multiple chemicals, other
than the specific isomers of the nominated chemical itself. Since some current and future chemicals will
have effects on endpoints in combination with other chemicals, it is likely that these interactions may
become of greater importance in the deliberations and decisions of the Committee.
4.
The Committee does not have a framework within which toxicological interactions may be
considered. Additivity, antagonism and synergism are three of the possible effects that could have an
impact on endpoints. The Committee may wish to consider an ad hoc approach to this issue or may
wish to develop a more systematic approach for addressing toxicological interactions of nominated
chemicals.
II.
Questions to address and possible topics for discussion
5.
Since the Committee has deliberated and developed criteria, working definitions and documents
on other topics relevant to evaluations under Annexes D, E and F, a discussion and development of a
possible framework to assess toxicological interactions could be timely. The Committee may wish to
consider the following broad questions:
(a)
(b)
(c)
(d)
6.
A.
B.
The possible topics for further discussion include:
Overview of “toxicological interactions”
(a)
History of research on toxicological interactions;
(b)
Likelihood of interactions given the character of real world pollution scenarios;
(c)
Endpoints typical of multiple chemical interactions;
(d)
Recent developments and examples where multiple chemical effects have been seen in
the lab and nature.
Approaches taken to investigate toxicological interactions
(a)
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What additional information is needed to enable the Persistent Organic Pollutants
Review Committee to address toxic interactions in its deliberations?
What specific information on persistent organic pollutant interactions should be
included in a risk profile?
What would be the possible implications of interactive effects of persistent organic
pollutants on the application of the precautionary approach as described in Annex E?
What guidance on the preparation of a risk profile should the Persistent Organic
Pollutants Review Committee provide regarding consideration of interactive effects?
Contrasting the study of single chemicals (or classes of chemicals) with multiple
chemicals;
UNEP/POPS/POPRC.4/INF/3
(b)
C.
Methods for understanding the toxicity of mixtures of congeners and isomers, covering
two alternatives:
(i)
Integration of data from toxicity studies conducted with individual congeners,
isomers or mixtures of a limited number of congeners when assessing the
toxicity and adverse effects of the whole mixture;
(ii)
Analysis of the information obtained in toxicity studies conducted with a
complex mixture for assessing the toxicity and adverse effects of individual
congeners, isomers or selected mixtures different from those assayed.
Frameworks for chemical management which take account of toxicological
interactions
(a)
Methods for summing up the potential for combined adverse effects of mixtures of
persistent organic pollutants that are individually at low exposure levels;
(b)
Existing frameworks that consider such interactions;
(c)
Proposed framework(s) that may be used or adopted by the Committee.
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