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Quality of nano toxicity data is ‘not great’, says expert

By Elaine Watson , 22-Jun-2011
Last updated on 22-Jun-2011 at 17:56 GMT2011-06-22T17:56:21Z

Quality of nano toxicity data is ‘not great’, says expert

The limited nature of many toxicity studies into engineered nanoparticles used in the food and dietary supplements industry makes it very difficult to draw firm conclusions about their safety, according to one expert in the field.

Speaking at the IFT show last week, Dr Bernadene Magnuson, senior scientific and regulatory consultant at Cantox Health Sciences International, said an analysis of 30 studies toxicity studies into engineered nanoparticles highlighted gaps in the research and methodological problems.

For example, most in vivo tests were high, single-dose, acute studies, which were of “limited relevance to food exposure”, which should examine the impact of repeated low doses over a long period of time, she argued.

“There are a few short-term repeated dose studies, but no long-term, chronic studies. In general, the reliability of the data from nanomaterial toxicology studies is not great.

"We need to improve characterization and the quality of the studies," added Magnuson, a toxicologist best known for her work on assessing the safety of aspartame.

Testing methodologies must be validated

Meanwhile, many in vitro test results were equally unreliable because the nanomaterials in question could interfere with optical or other detector measurements and with colorimetric and fluorometric dyes used in cell cytotoxicity tests, she pointed out. “They can also interfere with assays for measurement of reactive oxygen species.”

Some nanomaterials could also adsorb essential growth factors and nutrients from the growth media, “leading to non-specific indirect growth inhibition and apparent cytotoxicity”, she added.

“You have to ask: Did the nanomaterial interfere with the assay itself? These tests must be validated.”

What was missing was reliable data on the detection and quantification of nanomaterials in tissues, especially those with multiple components that may not be stable in vivo, she said.

More research looking at the incorporation of nanomaterials in food matrices was also needed to find out whether they adhered to proteins or other food components in ways that could not be predicted from studying them in isolation, she said.

“We need studies on the effect of food matrices on the bioavailability of nanomaterials.”

Nanotechnology definitions

Several factors needed to be taken into consideration when considering whether a nanomaterial potentially raised any safety issues, she said, notably persistence/bio-accumulation in the body, anti-microbial activity; level of reactivity, complex morphology; and interaction with biomolecules such as proteins.

Therefore, the recent guidance document from the Food and Drug Administration (FDA), which said regulators would consider a range of factors as well as size in assessing nanomaterials, was welcome, she said.

“It’s really useful to have something in writing.”

FDA on nano labeling and legislation

Whether labels were advisable to alert consumers to products made using nanotechnology was a more difficult question, she said. “Then the scope of any legal definition would become very important. If you were just looking at size, you’d have to label milk, which would be very confusing to the consumer.”

When asked by FoodNavigator-USA.com whether a legal definition of nanomaterials was expected soon, or whether the FDA believed a nano labeling regime was required, a spokesman said it was too early to say.

He added: “At this time, the agency is seeking public comment on the points to consider presented in the draft guidance. We will consider all public comments in determining any follow-up actions on this draft guidance, including the agency’s consideration of any regulatory definitions in the future.”

On labeling: “FDA will continue to evaluate the need for, and appropriateness of, any labeling statements related to nanotechnology on a case-by-case basis, in accordance with its existing labeling regulations and policies.”

As to whether the current regulatory regime addressed concerns about the safety of nanoparticles, he said: “FDA believes that its existing statutory authorities are adequate to regulate the use of nanotechnology in FDA-regulated products.”

Click here to read more about the FDA's recent draft guidance document on nanotechnology.

Click here to read about applications of nanotechnology in the food industry.

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