No new or unknown risks from common nanomaterials

29 Aug 2011

There are no new or unknown risks from seven of the most commonly used nanomaterials, said a report from the Danish Environmental Protection Agency (DEPA). But the body said a fundamental lack of knowledge meant it was unable to give the nano-substances its full safety backing.

In a 136-page document, scientists from the Denmark aimed to provide an overview of the functions of the most used materials and identify potential areas of concerns linked to their employment.

But while declaring their work brought to light no new risks from the substance, it was also clearly stressed that a decisive risk assessment was beyond current knowledge. Much remains unknown with significant more research crucial to deepen understanding, said the paper.

Lack of consensus

Noting the lack of consensus of the definition of nanomaterials, DEPA said they are “often” described as “materials having one or more external dimensions in the nanoscale (1 nm to 100 nm) or materials which are nanostructured (possessing a structure comprising contiguous elements with one or more dimensions in the nanoscale but excluding any primary atomic or molecular structure)”.

The seven nanomaterials examined were: Titanium dioxide, Cerium dioxide, Fullerenes (Carbon balls), Silver, Zero-valent iron, Silicium dioxide and Nanoclay.

While the authors identified cosmetics, sports equipment and lubricants as the most current common uses of the technology, areas such as food packaging and formulation are generally acknowledged as two other areas where potential future use is greatest. Nanosilver is used for its antimicrobial properties in packaging while adoption of nanoclay is centred on its oxygen barrier abilities.

The research found that Titanium dioxide, nanoclay and silicium dioxide were the materials used most in

Denmark.

“The use of nanosilver has not been confirmed, but indications exist that some products/brands may contain nanosilver”, added the authors. The use of nanosilver in food and cosmetics products is a hotly debated one. In June 2010 the German Federal Risk Assessment body (BfR) declared there was “no place” for the substance in the applications until there was conclusive proof of its safety.

Use of cerium dioxide remained unconfirmed and no was available on fullerenes and zero-valent iron.

Unanswered questions

The report sets out a raft of information - characteristics, uses, manufacture and possible hazards – but it also underlines that “the specific knowledge base is limited and that more information is needed for sufficient characterisation of the nanomaterialsand for illustration of the relevant (eco) toxicological endpoints”.

There are also significant knowledge gaps “with regard to fate, behaviour and kinetics” and, crucially, three is the need for a consensus on methodology for risk assessment.

“Conclusive risk assessments were therefore not possible to develop within the framework of the present project,” said the group.

It added: “Based on the reviewed literature the seven selected nanomaterials were not found to exhibit new and completely unknown risks to the consumer or to the environment in the current application.”

It estimated that products in the form of liquids or free particles would lead to the highest exposures in the environment and to humans - particularly liquids intended to come in direct contact with the body.

It cautioned that potential risk is likely to increase with increased exposure – but added again that more research was need, especially relating to engineered nanomaterials.

A key question was whether risk assessments regarding the bulk counterpart of such substances as Titanium Dioxide, could be applied to nanoscale materials.

A further debate topic is that while some nanomaterials are naturally occurring and have been used for decades, they can be modified with different surface coating, which can alter their physical-chemical properties and toxicity, added DEPA.

Source: Danish Environmental Protection Agency