Thomas Backhaus

The University of Gothenburg just published this press release (in Swedish) on our State of the Art report,  which was taken up by Göteborgs Posten, the local newspaper here. Miljöaktuellt published it here, Forskning.se here.

Thomas

PS.: and here are the English versions: Chemicals Health Monitor, Medical News

PPS.: and  Eureka, X-Journals, (although I don’t particularly like that they ripped of my photo from the site), ScienceDaily, ChemicalProcessing, EMaxHealth, etc…

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Our State of the Art report on the toxicology and ecotoxicology of chemical mixtures has just been published by the European Commission. It is actually open for discussion, i.e. the Commisssion invites feedback until the 30th of April.

Our main conclusions are:

1. We need a European guideline for the assement of the toxic effects of chemical mixtures on human health and the environment. Current US guidelines can serve as a template, but efforts should be made to incorporate human health oriented efforts with environmental assessments.
2. Only a strong legal mandate (as it recently has been implemented in the new European pesticide regulation) would motivate a wide-spread and regular consideration of ”cocktail effects” of chemical mixtures in environmental and human health oriented regulations.
3. Especially media-oriented regulations, such as the IPPC and WFD Directives (the latter was not considered within the report), provide a suitable perspective for the consideration of mixtures in regulatory settings.
4. Concentration Addition should be used as a first, default assessment concept for chemical mixtures in general.
5. It needs to be ensure that the generation, storage and dissemination of toxicological and ecotoxicological data facilitates their use for a later modeling of mixture effects.

The work was led by Andreas Kortenkamp of the London School of Pharmacy. Michael Faust and myself teamed up with him for the work. The tasks of the report were to analyze

• the scientific literature on mixture toxicity,
• current EU risk assessment regimes relevant to mixture toxicity assessments,
• the practical experiences in assessing mixture toxicity, approaches and methodologies used for this purpose in the EU, and
• approaches to assess mixture toxicity in major competing economies of EU and international bodies

with respect to human toxicology and ecotoxicology. You find the report as a whole PDF for download here.

The reports starts with an executive summary and it is introduced by the discussion of a series of common mixture-related questions:

• Is an assessment of the effects of chemical mixtures necessary from a scientific
  viewpoint?
• Is there not sufficient protection against mixture effects if we make sure that each
  chemical is present individually at exposures unlikely to pose risks?
• Is it necessary to test every conceivable combination of chemicals or is it possible to
  predict the effects of a mixture?
• Which of the two assessment and prediction concepts, dose addition or independent
  action, should be utilized in practice?
• Which chemicals should be subjected to mixtures risk assessment?
• How should mixture effect assessment concepts be applied in practice?
• What knowledge gaps hamper the consideration of mixture toxicology and
  ecotoxicology in chemical risk assessment?

We then also provide an overview of the current European regulatory system with respect to chemical mixtures and feedback that we received from a questionaire on the practical experiences with mixture toxicity assessments in the European member states.

Thomas

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Here is a short but comprehensive overview of the currently regulatory system for chemicals in the US. Lead author is Emily Monosson, who is also taking up the issue of chemical mixtures in the article:

The FQPA [Food Quality Protection Acti] is changing the way pesticide residues are regulated by setting ‘health-based’ standards for ALL pesticides in foods. ‘All’ in this case means combined residues from several different pesticides, or, chemical mixtures. The importance of this amendment, with respect to chemical mixtures should not be underestimated. This is one of the first attempts to regulate the permitting of individual chemicals based on their potential for combined toxicity. It will require development of innovative and reliable techniques to address combined toxicity. Although we will discuss the methodology used to determine new pesticide limits later, we should point out that this combined approach for now is limited to similarly acting pesticides. Currently, the FQPA does not address pesticide mixtures that act through different mechanisms. For example, several different organophosphate pesticides may occur in combination along with arsenic. The mixtures assessment will consider the combination of organophosphates, but nonetheless will assess arsenic separately. The rational for only extending combined toxicity to similarly acting pesticides should become clear as we discuss the toxicological tools available for such work.

Together, the FFDCA and FIFRA regulate a large share of chemicals to which humans are likely to be exposed, by setting tolerances and allowable concentrations for chemicals, one chemical at a time, up until 1997. This is almost a one hundred year history of single chemical regulation. Not only does toxicology and regulatory policy have a long history based upon the single-chemical approach, but they must now address the reality of chemical mixtures. Although clearly the single-chemical approach has provided a strong foundation for chemical control, the utility or relevance of these techniques for addressing multiple chemical exposures is currently unclear.

Unfortuantely, I couldn’t find the promised discussion on why the legislation is restricted to similarly acting chemicals. Mental note to myself: Need to check the mentioned amendments. Guess it’s the old “mixtures of dissimilarly acting chemicals do not show a combination effect if all individual substances are at or below their toxicological thresholds”. Please see the rebuttal here.

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