Empa, Swiss Federal Laboratories for Materials Science and Technology, led a 3.5 year project, NanoHouse, investigating whether or not nanoparticles added to paint used on building facades might prove a health hazard. From a Jan. 13, 2014 news item on Nanowerk (Note: A link has been removed),
After 42 months the EU research project “NanoHouse” has ended, and the verdict is a cautious “all clear” – nanoparticles in the paint used on building façades do not represent a particular health risk. In the course of a “Technology Briefing” Empa researchers discussed these results with specialists from the construction industry.
Five Empa laboratories were involved in the EU NanoHouse project, along with four other European research institutes and four industrial partners. The aim of the project was to investigate the opportunities and risks presented by the nanomaterials used in the surface coatings applied to building façades. For the first time not only were freshly manufactured products studied to see if they set free nanoparticles, but also aged samples.
The January 13, 2014 Empa press release, which originated the news item, provides more details about the recent NanoHouse technology briefing,
… Claudia Som briefly introduced the «NanoHouse» project, for which she acted as Empa coordinator. This project, which is financially supported through the EU’s 7th Research Framework Program, began in 2010 with the aim of investigating possible health effects caused by nanoparticles in building materials and houses. Various aspects of the research program included rubbing tests on model façades, attempts to wash out nanoparticles from surface coatings and an analysis of the biological effects on humans and the environment.
…
Tina Kuenniger, an Empa expert on the protection of wood surfaces against weathering, explained how nanoparticles work in paint. Some paints containing silicon dioxide are water repellent, easy to clean and scratch resistant. Nano titanium-dioxide has photocatalytic properties and can decompose air pollutants. Nano titanium-dioxide, along with nano zinc-oxide and nano-iron oxide, can be used to provide UV protection and, depending on the size of the particles used, also to protect against infrared radiation, i.e. heat. Similarly, nanoparticles can protect against attack by blue stain fungus and algae. Whilst many laboratory studies have confirmed the effectiveness of nanoparticles, in practice one question remains open: how much of the nanomaterial does one have to mix with the paint to ensure that it functions as expected? For this reason only a few products for external façades containing nano-materials are available on the market to date. The greatest opportunity nanoparticles offer lies in the combination of various functional properties, for example scratch resistance and easy (or self) cleaning characteristics.
The results of the tests surprised researchers from Empa and other consortium members (from the press release),
Bernd Nowack, head of Empa’s Environmental Risk Assessment and Management group, then presented the results of the investigations into how much nanomaterial is set free from façades. The release rate is generally very low – only 1 to 2% of the nanoparticles find their way into the environment. And in most cases they are released not as nanoparticles but bound to large paint particles, which significantly reduces their nano-scale effects. “We were very surprised at how few nanoparticles were actually set free”, Nowack admitted. The researchers had expected that the catalytically active nanoparticles would also attack the paint surrounding them, leading to more frequent release.
Jean–Pierre Kaiser showed by means of his toxicological studies that paints containing nanoparticles have the same effect on the behaviour of cells from the gastrointestinal tract and immune system as do similar paints which do not contain nanoparticles. The Empa researcher does not therefore expect that these nanoparticle-containing paints will represent a new, acute health risk. However, the investigations did at the same time show that nanoparticles are absorbed by the cells. Whether this accumulation of nanoparticles in the cells might lead to longer-term effects cannot yet be definitively determined.
Empa environmental scientist Roland Hischier made a plea for a reasonable balance in the assessment of the possible environmental damage. For a house with an assumed lifetime of eighty years, painting the façade with nanomaterial based paint would be more economic if this lasted for 30% longer than conventional coatings. Then, over the lifetime of the house, one would have to repaint the façade one time fewer, avoiding all the environmental effects caused by manufacturing the paint and disposing of the leftover material.
This theory remains somewhat controversial however –houses are frequently repainted for aesthetic reasons and not because a new coating is strictly necessary. In this case the advantage offered by the longer lifetime of nanoparticle-based coatings becomes completely irrelevant.
The researchers performed an industry survey revealing what professional paint companies believe to be true about nanoparticles in paint (from the press release),
… Ingrid Hincapie, a risk researcher on the Empa staff, reported on the results of her industrial survey. Many companies expected paint containing nanoparticles to have a longer lifetime than conventional paint. Some expected it to be easy to handle, for example because it dries faster. But exactly how one correctly disposes of leftover paint containing nanoparticles is something that only a handful of respondents knew.
Peter Seehafer of the Painter’s and Plasterer’s Association, gave the view from the sharp end, where quite simply the customer is king, and sometimes demands the latest in paint technology. On the other hand, about half of all painters are female, so protection from possibly unhealthy chemicals is therefore particularly important. “Our professional association needs more information, so that we can take up a clear position with respect to our customers and our employees”, demanded Seehafer.
Finally, André Hauser of the Swiss Federal Office of the Environment explained the current regulations covering the disposal of waste material containing nanoparticles. On its website www.bafu.admin.ch/abfall/01472/12850 the SFOE offers tips on how to dispose of such material properly. The current regulations relating to safe working practices with nanomaterials were explained by Kaspar Schmid of the Swiss government’s State Secretariat for Economic Affairs (SECO). The essential point here is that the manufacturer of the material must provide a Material Safety Data Sheet, as is the case with other chemicals.
In addition to the NanoHouse link given earlier, there is this Empa NanoHouse webpage which provides more information about the work including the survey of nanopaint producers from the project’s Survey webpage,
A survey of industrial producers of nanoparticles and paints showed that the most mentioned potential benefits of nano-enhanced façade coatings are: water and dirt repellent “easy to clean”, followed by UV-protection, antimicrobial resistance and protection from mechanical wear (i.e. scratch resistance). The ENP [engineered nanopartilces], which are the most used in Europe to improve the different functionalities of the façade coatings were: Ag [silver], functionalised silanes, TiO2 [titanium dioxide] and SiO2.[silicon dioxide]
The quality of a nano-paint compared to a traditional paint could be gradually (25% of responses) and noticeably (25%) improved, but 50% of the respondents reported no functionality improvement. The companies gave relevance on studies from the specialised press (90%), on participating in dialogue events (80%) (e.g. with authorities or taking part in projects such as NanoHouse), on getting expert opinions (70%) and on toxicology test (20%).
The overall impression from the survey was that improvement of the environmental performance seems not yet to be in the focus of innovation of ENP in façade coatings.
It’s a bit disappointing that the environmental performance of nanocoatings does not, according to this project’s findings, does not live up to the promises made by the various purveyors of nanotechnology-enabled paint.