The science of the very small will lurk in many a Christmas gift this year. Nanomaterials add strength to golf clubs, odour resistance to socks and ultraviolet protection to cosmetics. But some of their properties could also pose health risks, and regulations covering their manufacture and use have failed to keep pace with the rush to market.
With sizes measured in mere billionths of a metre, nanomaterials have very high surface area relative to their mass, and this could alter their toxicity compared with the same material in bulk. Yet many nanomaterials are not regulated separately — in part because the high-quality nanotoxicity research needed for regulation is lacking, as an assessment presented at last week’s Materials Research Society meeting in Boston, Massachusetts, made clear.
Groups representing food manufacturers had asked Cantox Health Sciences International, a consultancy in Mississauga, Canada, to review the literature for studies that could shed light on the effects of consuming nanoparticles from food packaging, in which they may be used to improve strength or even detect spoilage.
Cantox sampled 30 papers describing studies in which nanoparticles were fed to animals or applied in vitro to cells of the gastrointestinal tract. Of 21 animal studies, the Cantox researchers found that 15 failed to attain the highest grade on the Klimisch test, a quality-control criterion that assesses whether basic data, such as the number or gender of animals used, have been reported. “Some didn’t give the dosage. This is a fairly important aspect,” says Jeffrey Card, a toxicologist at Cantox who led the study.
The underlying materials science was equally spotty. Of 10 parameters that Cantox concluded should be reported in a nanotoxicity study, such as particle size, shape and surface chemistry, more than half were missing from 14 of the animal studies1.
Yongping Bao of the University of East Anglia in Norwich, UK, an author on one of the studies2 given low marks by Cantox, points out that some of the missing data appear in other papers by his group. But he believes that the review highlights the need for government regulatory agencies to establish agreed standards for this sort of research. “Anyone can set his or her own criteria to review nanotoxicity literature, so a gold standard is urgently needed,” he says. Nanotoxicity studies arguably require additional standards, because nanoparticles can vary within a batch much more widely than do bulk chemicals, for example.
Altaf Carim, assistant director of nanotechnology at the White House Office of Science and Technology Policy, says that the US National Nanotechnology Initiative’s Environmental, Health, and Safety Research Strategy3, unveiled in October, will develop a set of standards that should help researchers and agencies to plug that gap. “We are certainly hoping the broader community is going to make use of it,” Carim says.
Nanotoxicologists have also lacked standard reference materials for defining nanoparticles. The US National Institute of Standards and Technology has produced references for gold and polystyrene nanoparticles, but has yet to issue similar samples of other nanomaterials.
Later this month, however, the institute will release its first batch of standard reference carbon nanotubes — the result of three years’ work, according to Kalman Migler, who is overseeing the project. Researchers will be able to buy vials of the nanotubes to calibrate their measurement equipment and assess levels of common contaminants in their samples. The reference nanotubes, the first ever provided by a national standards agency, should help nanotoxicologists to pinpoint whether any observed adverse reactions are the result of nanoparticles rather than impurities, for example.
Yet the latest nanotechnology decree from Europe perhaps shows how far regulation efforts still have to go. On 18 October, the European Commission finally adopted a definition of a nanomaterial: one in which half or more of the particles in a sample have one dimension that measures between 1 and 100 nanometres4. The definition had been requested by the European Parliament in April 2009.