TEM images of carbon particles from foods containing caramelized sugar. Click to see larger image. Source: Palashudding et al.

Nanotechnology leads to novel materials, new exposures and potentially unique health and environmental risks – or so the argument goes.  But an increasing body of research is showing that relatively uniformly sized nanometer scale particles are part and parcel of the environment we live in.  For instance a number of simple organisms such as bacteria and diatoms have the capability to produce nanoparticles, either as part of their natural behavior or under specific conditions.  Nanoscale minerals, it seems, play an important role in shaping the world we live in.  Metals like silver wantonly shed silver nanoparticles into our food and water according to research published last year.  And now a group of researchers have shown that food containing caramelized sugar contains uniformly sized amorphous carbon particles.

This latest paper was published in the journal Science Progress a few weeks ago, and analyzes the carbon nanoparticle content of such everyday foods as bread, caramelized sugar, corn flakes and biscuits.  The authors found that products containing caramelized sugar – including baked goods such as bread – contained spherical carbon nanoparticles in the range 4 – 30 nm (with size being associated with the temperature of caramelization).  This isn’t that surprising as nanoparticle formation is closely associated with hot processes.  The authors point out that, as caramelized products have been eaten with no apparent health impacts for centuries, these particles are probably safe.  But the bigger question perhaps is whether these particles are sufficiently similar to some nanoparticles now being intentionally produced to provide insight into the safety of engineered nanoparticles, or whether there remain fundamental differences between the particles we are exposed to everyday, and those that smart technologists are dreaming up in laboratories around the world. As Gwyneth Shaw writes in the New Haven Independent,

“The presence of carbon nanoparticles in hamburger buns only illustrates the depth and complexity of the challenge for policymakers, in the U.S. and internationally, in ultimately deciding what’s “safe” and what might not be.”

This is not an easy question.  Hypothetically, it is possible to produce nanoscale particles that are so unlike anything we have evolved to handle that they interfere with our biology in potentially destructive ways.  And when some of the more esoteric types of nanomaterials now being explored are considered, this possibility is easy to imagine.  Yet in many cases commercial nanomaterials show a striking resemblance to those found in this study and elsewhere.  In these cases, there is a need to understand what is new in the context of what we are already regularly exposed to.

To do this requires more research into the nature of naturally occurring nanomaterials and our exposure to them.  And I can guarantee that this will be a contentious area of research, as it questions the prevalent dogma that exposure to uniform nanoparticles is both new and potentially dangerous.  In fact research in this area is so sensitive that my first reaction on reading the Science Progress paper was to wonder how valid the findings were.  Fortunately, the analysis stands up to scrutiny.  The authors were careful to test their findings using electron microscopy – which showed the presence of very uniform nanoparticles associated with caramelized sugar.  And to make sure the observed particles weren’t an artifact they carried out similar tests on uncaramalized sugar solutions – where they found no evidence of nanoparticles.

As usual though, the research raises as many questions as it answers.  While the size and composition of these particles has been measured, their concentration and precise chemical nature remains unknown.  So as ever there is more research to be done to pin down how many – or how few – carbon nanoparticles you are ingesting with your morning bowl of corn flakes, and to understand how these data affect how we approach intentionally manufactured nanoparticles.  But what is becoming increasingly clear is that the safe use of engineered nanomaterials cannot be understood in isolation from the nanopaterials that we eat and breathe every day of our lives.

End Notes:

Gwyneth Shaw has an excellent piece on this paper at the New Haven Independent: http://www.newhavenindependent.org/index.php/archives/entry/how_long_have_we_been_eating_nanoparticles/  I would strongly recommend anyone interested in following nanotechnology implications issues to subscribe to her writing in this area.

The papers cited above are:

Palashuddin Sk M., Jaiswal A., Paul A., Ghosh, S. S., and Chattopadhyay A. (2012) Presence of Amorphous Carbon Nanoparticles in Food Caramels. Scientific Reports 2:383, DOI: 10.1038/srep00383

POPESCU M., VELEA A., and  LÖRINCZI A. (2012) Biogenic Production of Nanoparticles. Digest Journal of Nanomaterials and Biostructures 5:4 pp1035-1040.

Hochella Jr. M. F., Lower S. K., Maurice P. A., Penn R. L. Sahai N.,  Sparks D. L., Twining B. S. (2008) Nanominerals, Mineral Nanoparticles, and Earth Systems.  Science 319 pp1631-1635. DOI: 10.1126/science.1141134

Glover R. D., John M. Miller J. M., and Hutchison J. E. (2011) Generation of Metal Nanoparticles from Silver and Copper Objects: Nanoparticle Dynamics on Surfaces and Potential Sources of Nanoparticles in the Environment.  ACS Nano, 2011, 5 (11), pp 8950–895  DOI:10.1021/nn2031319

Maynard A. D., Warheit D. B. and Philbert, M. A (2011) The New Toxicology of Sophisticated Materials: Nanotoxicology and Beyond. Tox. Sci. 120 (suppl 1): S109-S129. doi: 10.1093/toxsci/kfq372

And finally, any paper with a methods section that starts like this gets my approval 🙂

Bread buns were purchased from the local market (Homa Bread, Guwahati, India) and analysed to check the presence of CNPs within it. The top brown layer of bread was carefully excised and 1 g of it was dissolved in 20 mL methanol by sonicating it at 35 kHz in a bath sonicator (Elmasonic TI-H-5 Elma, Germany) for 10 min. Following sonication, the volume of the methanol was reduced to 3 mL in a rotary evaporator before further purification.

Andrew Maynard