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OECD conclusions about nanomaterials and test guidelines disputed

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Researchers in Denmark and the US have criticised the OECD's Sponsorship Testing Programme for Nanomaterials and called for follow-up work to confirm its conclusions.

According to the researchers, led by Steffen Foss Hansen at the Technical University of Denmark, with support from colleagues at Arizona State University, the programme's conclusion “that the test guidelines used for regular chemical substances are in the most part suitable for use on nanomaterials” is not supported by the evidence in the dossiers.

They say that a further programme is needed to “systematically evaluate the applicability and interpretation of toxicity assays for nanomaterials, and to develop new methodologies where existing ones fall short”.

In a paper published in Environmental Science Nano, the researchers raise several objections about the work, which ended in 2015. They are:

  • Most of the studies were not designed to investigate the validity of the test guidelines.
  • Most of the contributors to the programme applied existing guidelines for chemicals, with little or no reporting of the test performance in relation to nanomaterials.
  • The studies that discuss test validity, and explain modifications made to accommodate nanomaterials, provide “substantial points of concern” about the general applicability of the OECD test guidelines.
  • The number of studies conducted for each endpoint was low. 
  • Although the dossiers have made available large data sets on certain nanomaterials, the value of the knowledge is “limited” because the information “often replicates what was already known in 2007”.

The programme was launched in 2007 to provide information on the safety of key nanomaterials, and decide if existing tests were generally suitable. It has published 11 dossiers, each on a different nanomaterial.

The OECD has defended it. Bob Diederich, head of its environment, health and safety division, told Chemical Watch: “The testing programme was always about gaining experience on the applicability of our test guidelines to nanomaterials. It was never about deriving actual regulatory risk assessments for these 11.”

He added: “Thanks to the testing programme, we have gained a lot of experience in how to characterise the properties of nanomaterials so that the results are fit for purpose in regulatory risk assessment. And we are well on our way in using this experience to adapt the regulatory tools for assessing the safety of nanomaterials.”

Peter Kearns, a principal administrator in the division, said although “the majority” of tests were found to be adequate for nanomaterial assessment, others were found to be in need of adaptation. Furthermore, the programme identified a need for new tests in certain areas. There are eight projects for new tests in the workplan as a direct result of the programme, he said. Additionally, updates to two inhalation tests are scheduled.

Dr Kearns disagreed that a further OECD programme was needed and said that, from the outset, the intention had been for the programme to be flexible and to take a pragmatic approach. It had, for example, included findings from other major initiatives with overlapping aims as they became available, often through workshops that brought together a wide range of experts. He cited the recently published guidance on sample preparation and dosimetry as one output for which the need was realised as the programme progressed. “Sample preparation is key for nanomaterials,” he said.

In October, the EU-funded Managing Risks of Nanomaterials (MARINA) project proposed changes to eight OECD ecotoxicity tests to account for nanomaterials.

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