Sometimes environmentalists get accused of being against everything, so it\u2019s important to speak out when the science suggests that a new technology is not obviously harmful to the environment.\u00a0 Right now, I think that is the case with most forms of manufactured nanoparticles. \u00a0I expected the worst, but the available science is more reassuring.<\/p>\n
Just what are nanoparticles? \u00a0Like the name suggests, these are very small particles\u2014less than about 300 nanometers in diameter.\u00a0 At the moment, the EPA regulates air pollution by particles that are less than 2.5 micrometers in diameter, known as PM2.5<\/sub>, which includes nanoparticles, but also particles that are as much as 8X larger.\u00a0 Particles less than 2.5 um in diameter can be inhaled deep into our lungs, where they can lead to undesirable effects.<\/p>\n Very small particles are ubiquitous in nature. Many of the clay minerals in soils are found in particles that fall into the size range of nanoparticles. Woodsmoke also contains particles of that size and larger.<\/p>\n Manufactured nanoparticles are produced with specific purposes in mind.\u00a0\u00a0 For example, nanoparticles of titanium oxide form the basis of many sunscreens, because they increase the reflection of sunlight away from a treated surface. \u00a0Nanoparticles produced with silver are useful as antimicrobial agents that have revolutionized the treatment of burns.\u00a0 Silver nanoparticles are also added to athletic-wear, such as socks to kill the microbes associated with \u201cfoot odor.\u201d\u00a0 (My mother would have certainly appreciated that when I was growing up.)<\/p>\n Their small size is one reason nanoparticles are so effective.\u00a0 Most of the atoms in a nanoparticle are found at or near the surface, so they deliver an effective dose of reactive material to the target. Already, huge quantities of nanoparticles are in industrial production.\u00a0 A 2011 assessment by Dr. Christine Hendren and her collaborators at Duke\u2019s Center for the Environmental Impacts of Nanotechnology (CEINT) reported production of titanium nanoparticles alone is likely to exceed 38000 tons\/year.\u00a0 Of course, most of the nanoparticles in sunscreens and antibacterial clothing are likely to be washed off in water and enter the sewage-treatment stream of modern society.<\/p>\n One might expect a host of environmental impacts of antimicrobial particles in nature, particularly when they enter wetlands. \u00a0Silver and copper have biocidal properties that have been recognized for centuries.\u00a0 At high concentrations, titanium nanoparticles can alter bacterial composition in freshwater environments.\u00a0\u00a0Nano-particles are taken up by phytoplankton and passed to higher levels of the food chain.\u00a0 Nanoparticles can also be taken up by larger wetland plants and accumulate in their tissues.\u00a0 Silver nanoparticles are known to kill bacteria in wetland sediments, even at the low dosage that is carried in sewage waters that have been diluted by other effluent. The purposeful and inadvertent impacts of nanoparticles are often determined by their surface affinity to other components of the environment. \u00a0Ben Colman, also at Duke, has shown that nanoparticles are altered and degraded in nature, making them less effective in their anticipated role.<\/p>\n In an ideal world, the best available science would inform policy.\u00a0 Certainly, policy should be responsive to change as new scientific results are delivered.\u00a0 But, my read at the moment suggests that nano-particles have a benefit\/cost ratio significantly greater than 1.0.\u00a0 Let\u2019s not stop studying the potential impacts of nanoparticles; something bad may turn up.\u00a0 But let\u2019s not sound premature alarm either.<\/p>\n <\/p>\n References<\/p>\n Bernhardt, E.S., B.P. Colman, M.F. Hochella, B.J. Cardinale, R.M. Nisbet, C.J. Richardson and L. Yin. 2010.\u00a0 An ecological perspective on nanomaterial impacts in the environment.\u00a0 Journal of Environmental Quality 39: 1954-1965.<\/p>\n Echavarri-Bravo, V. , L. Paterson, T.J. Aspray, J.S. Porter, M.K. Winson, B. Thornton and M.G.J. Hartl.\u00a0\u00a0 2015.\u00a0 Shifts in the metabolic function of a benthic estuarine microbial community following a single pulse exposure to silver nanoparticles.\u00a0 Environmental Pollution 201: 91-99.<\/p>\n Hendren, C.O., X. Mesnard, J. Droge, and M.E. Wiesner. 2011. Estimating production data for five engineered nanomaterials as a basis for exposure assessment.\u00a0 Environmental Science and Technology 45: 2562-2569<\/p>\n Jomini, Stephane, Hugues Clivot, Pascale Bauda, Christophe Pagnout.\u00a0 2015. Impact of manufactured TiO2 <\/sub>nanoparticles on planktonic and sessile bacterial communities.\u00a0 Environmetnal Pollution 202: 196-204.<\/p>\n Judy, J.D. and P.M. Bertsch. 2014.\u00a0 Bioavailability, toxicity and fate of manufactured nanomaterials in terrestrial ecosystems.\u00a0 Advances in Agronomy 123: 1-64.<\/p>\n Kumar, P., A. Robins, S. Vardoulakis, and R. Britter. 2010. A review of the characteristics of nanoparticles in the urban atmosphere and the prospects for developing regulatory controls.\u00a0 Atmospheric Environment 44: 5035-5052.<\/p>\n Lee, W.-M., S.J. Yoon, Y.J. Shin, and Y.J. An. 2015.\u00a0 Trophic transfer of gold nanoparticles from Euglena gracilis<\/em> or Chlamydomonasreinhardtii<\/em> to Daphnia magna.<\/em>\u00a0 Environmental Pollution 201: 10-16.<\/p>\n Ma, H., P.L. Williams and S.A. Diamond. 2013.\u00a0\u00a0 Ecotoxicity of manufactured ZnO nanoparticles\u2014a review.\u00a0 Environmental Pollution 172: 76-85<\/p>\n Navarro, D.A., J.K. Kirby, M.J. McLaughlin, L. Waddington and R.S. Kookana. 2014.\u00a0 Remobilisation of silver and silver sulphinde nanoparticles in soils.\u00a0 Environmental Pollution 193: 102-110.<\/p>\n Pan, B. and B. Xing. 2012.\u00a0 Applications and implications of manufactured nanoparticles in soils: A review.\u00a0 European Journal of Soil Science 63: 437-456.<\/p>\n Sanderson, P., J. M. Delgado-Saborit, and R.M. Harrison. 2014.\u00a0 A review of chemical and physical characteristics of atmospheric metallic nanoparticles. Atmospheric Environment 94: 353-365.<\/p>\n <\/p>\n","protected":false},"excerpt":{"rendered":"