Scientific committee sounds warning on nanotech assessments

The EU’s chemical assessment regime may not be suitable for gauging the environmental risks posed by future nanotechnology products, an expert committee has warned.1

The broad outline of measures for addressing nanotechnology’s environmental and health risks were set out in the EU’s strategy and action plan in 2005, but details of how existing chemicals regulations might be adapted to address the risks were scarce (ENDS Report 365, pp 48-49 ).

In the same year, the European Commission asked its Scientific Committee on Emerging and Newly Identified Health Risks for its views on whether existing risk assessment methodologies were appropriate.

Issued for consultation in April, the committee’s Opinion says the existing risk assessment guidelines are "generally able" to assess the risks of nanomaterials’ to human health. But it voices concern that the basic criteria against which substances’ environmental risks are assessed - persistence, bioaccumulation and toxicity - may not be appropriate, or easily measured, for such materials.

The committee also thinks that the limited information available on nanoparticles’ environmental fate and behaviour will hinder researchers trying to compare environmental concentrations with those expected to cause harm - the other major test in the EU’s environmental risk assessment regime.

Particles with diameters of 100 nanometres or less often have different properties to bulk versions of the same substance, but the differences are not consistent enough to allow a unified approach at this stage. Instead, assessments should be done on a case-by-case basis, the committee says.

Although its report focuses on the EU’s existing chemicals Regulation, which will be annulled on 1 June, the new REACH regime will require only individual substances to be assessed, so nano-scale versions of existing chemical substances will escape separate evaluation.

The Commission and European Chemicals Agency will consider the consequences for REACH of the committee’s findings once they have been finalised following the consultation.

The committee believes the existing test methodologies are inappropriate for several reasons. First, they focus on the total concentration of a particular substance, whereas an approach based on the number and surface area of particles would be more suitable for nanotechnology.

Nanoparticles also have a tendency to clump together under some environmental conditions, which may require properties such as surface charge and solubility to be considered.

The committee also calls for more research on nanoparticles’ interactions with biological systems. It is still unclear, for instance, whether nanoparticles can cross the blood-brain barrier and what effects impurities could have.

It says it cannot provide guidance on the suitability of the species currently used to assess bioaccumulation and toxicity at this stage and instead proposes a tentative risk analysis framework. This could help determine the level of testing particular substances might require, and includes existing tests alongside new measures, such as a substance’s dispersal potential and dose-response relationship. But Aleksandra Kordecka of Friends of the Earth warned that the committee’s approach would allow some substances to escape scrutiny.

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