Report from expert workshop on combination effects

At a workshop on combination effects and regulatory aspects held by the Ministry of the Environment in January 2009, the experts' conclusions and recommendations were clear: although there are still large gaps in our knowledge, we have in recent years learned enough about the combination effects of endocrine disrupting chemicals for the consideration of combination effects to be both possible and advisable when risk-assessing endocrine disruptors.

In the past few years, several studies have produced striking results concerning the combination effects (sometimes referred to as cocktail effects) of endocrine-disruptors. For example, Danish research discovered severe malformations in rat pups when pregnant rats were exposed to a mixture of endocrine-disruptors in concentrations at which the compounds, when acting individually, do not cause effects.

The Expert workshop in 2009 was a follow-up to these research findings. Several of the world's leading experts on chemicals with endocrine activity and combination effects met in Denmark. They were asked to give a briefing on the current state of the science concerning combination effects and the feasibility of regulation.

In the report, the experts point out that the risks associated with chemicals are currently underestimated, because no account is taken of our daily exposure to a cocktail of many different compounds, amongst them endocrine disruptors.

The message from the experts is that the state of science has now made the inclusion of combination effects in risk assessments of endocrine disruptors both possible and necessary. The experts also specify a method known as dose addition, which can be used as a default.

A further recommendation is made for the improvement of the legislative framework for chemicals within the EU, to make it compulsory to include the risk of combination effects in assessments of chemicals. The experts use the term 'cumulative risk assessment' synonymously with 'mixtures risk assessment'.

The experts make it clear that there is a significant knowledge gap with regard to combination effects and risk assessments of chemicals. We particularly lack knowledge concerning how we are exposed to the substances, which substances are involved and in what quantities.

The Expert report was prepared by Professor Andreas Kortenkamp of the University of London, acting as Scientific Lead for the Expert workshop and Senior Scientist Ulla Hass of the National Food Institute at the Technical University of Denmark, who was responsible for the new Danish studies of combination effects.

Read the report