GreenScreen™ hazard assessment of silver and nanosilver demonstrates what we know, what we don't, and what we'd like to know before we get too cozy with nanomaterials
Posted June 11, 2013
Although there have been numerous published reports and reviews of the hazards of nanosilver and other nanomaterials, the results of this project, using GreenScreen™ established methods, are to our knowledge the most comprehensive systematic hazard screen of nanomaterials to date. The results provide some evidence that these materials can be assessed for hazards, and identify specific data gaps that must be filled. It’s simply not acceptable to allow nanomaterials to be commercialized while wringing our scientific hands and twiddling our regulatory thumbs saying we cannot assess their hazards.
Nanomaterials are pitched as “new and improved” chemicals, engineered at the teeny-tiny “nano” scale (one-thousandth of a micrometer) to be stronger, lighter, faster, brighter, or just plain better than their normal-scale chemical counterparts. And, they are rapidly replacing hazardous chemicals that are being phased out or forced out of consumer products, either through market demands or regulatory restrictions.
But, are we really risk-trading downwards? Or are we just replacing the risks we know about with ones we don’t? After all, we have limited understanding of the full-cycle impacts of nano applications to know if they are actually safe, and there are no validated or accepted toxicity tests designed for nanomaterials. At least, that’s what the experts say. But, although the chemical properties are new – at least at the nanoscale –what we want to know hasn’t changed. Does it cause cancer when fed to a lab mouse over a lifetime? Does it cause birth defects when ingested or inhaled during pregnancy? Does it make me cough or make my skin itch or eyes water? Nanomaterials are new, but the criteria for calling a chemical toxic hasn’t changed –biology is still the same.
The problem is that there are currently no standardized testing protocols, no labeling requirements, and weak regulation of most nanomaterials. And, what we don’t know about the environmental and occupational impacts of nanomaterials may be hurting us. We do not know enough about these materials to make informed decisions about how they should – or should not be used.
And, that’s where we set out to take some baby steps forward to show that we can evaluate the hazards of nanomaterials where data are available, and identify where information is absent. We used an established screening tool, the GreenScreen® – a hazard-level screening assessment tool based in part on the US EPA Design for the Environment Program (DfE) Criteria for Hazard Evaluation, and widely accepted by a growing number of governments, non-profit groups, and companies, like the state of Maine, the independent US Green Building Council LEED building certification program and Hewlett-Packard.
We contracted with NSF International, an independent not-for-profit company that is a licensed GreenScreen™ Profiler. We asked them to conduct three screens: 1) nanoscale metallic silver, 2) a silica-silver Nano composite, and 3) silver (low-solubility dispersed silver/silver salts).
What did the NSF scientists find? Both silver and nanoscale silver scored a benchmark of high concern, based on high aquatic toxicity, high persistence (long-lasting in the environment), and acute inhalation toxicity concerns. The identified data gaps include: reactivity, flammability, carcinogenicity, reproductive toxicity, and endocrine disruption.
The silica-nanosilver composite was not able to be scored because of too many data gaps, and therefore not enough data to evaluate the hazards with confidence. This is gravely ironic given EPA conditionally approved its use earlier in 2012 for textiles – giving it full market access to be used in all sorts of consumer textiles, including bedding, children’s blankets and clothes.(see NRDC lawsuit challenging the approval of the chemical here)
These results – albeit with limitations, data gaps, and imperfections – will be of great interest to scientists, regulators, risk assessors, chemical experts, environmental and occupational health experts, product designers and unions.
Nanomaterials are increasingly popular because they can make products more attractive, useful or helpful: fabrics that repel stains; auto paints that won’t chip; ketchup that flows with fewer globs; sunscreens that go on clear instead of white; and skin wound creams that promise to help us heal faster and feel better. (See an inventory of nano-enabled consumer products here). They sound fantastic. But what happens when chemical particles so small, pass through our skin, our blood and our lungs uninhibited, and from multiple sources, on a daily basis?
Despite these unanswered questions, the research and development of nanotechnology has skyrocketed in recent years. The independent advisory firm, Research, predicts that in 2015 nanotechnology value chain sales could reach $2.5 trillion. The U.S. government and U.S. corporations spend more money on nanotechnology than any other country, and nanomaterials are found in thousands of everyday products. Russia, the EU and many Asian countries also spend billions each year on new nano chemicals.
The White House is telling the public not to worry, that existing regulatory frameworks are handling these novel nanomaterials adequately.
In contrast, many non-government organizations (NGOs) are calling for a precautionary approach, often promoting the use of established best practices followed in other chemical handling facilities to protect workers. Without mandatory oversight for the development, use, and disposal of nanomaterials, companies will remain reluctant to invest resources into new products or technologies without knowing their future regulatory fate or liability risks.
More details about the GreenScreen™ and the nanosilver/silver methods and results are here.
A recent scientific review of nanosilver toxicology is here.