A Nanoparticle Flaps its Wings

You may have heard the saying that “a butterfly flaps its wings and…” insert your absurd unintended, chaotic, massive consequence here (e.g., a hurricane). We may not have much control over butterflies, but we do make choices as industries, governments, and individuals on which products we produce, regulate, and consume. Examples of such products that we initially thought were wonderful advances for humankind include chlorofluorocarbons (refrigerants), tetraethyl lead (makes engines run smooth), and DDT (curbed malaria epidemics). Unfortunately, the unintended consequences of such substances included a hole in the ozone layer, elevated blood lead, and poisoned ecosystems.Chasing Butterflies (MS ClipArt)

What can we learn from these experiences? Now we are in the midst of another industrial boom: Nanotechnology. It is estimated that thousands of tons of nanomaterials are now being produced each year. Why is there such an interest in nanomaterials? Well, to put it simply- they are “special”. Nanomaterials have unique properties in the size range of 1-100 nanometers that differ from their behavior as larger particles or in dissolved forms. Could these unique properties be a concern to the environment? This is a topic explored by the Virginia Tech Sustainable Nanotechnology (VT SuN) Interdisciplinary Graduate Education Program (IGEP). The aim is to be proactive, and think ahead in terms of what negative consequences our next engineering feats could lead to and nip them in the bud. For example, nanoparticles can be produced with numerous core materials, coatings, and surface modifications- maybe minor tweaks in design now could save the environment later.

In our article to come out in Water Research (Ma et al. 2014 doi.org/10.1016/j.watres.2014.09.008) we sought to determine if commonly produced nanoparticles, made of titanium dioxide, silver, ceria, or iron, might disrupt important water purification processes at wastewater treatment plants when flushed down the drain. We focused in on nitrifying bacteria, which are responsible for removing toxic ammonia, as our canaries in the coal mine. The good news- no observable effects of any of the nanomaterials on nitrifying bacterial activity! However, pyrosequencing of 16S rRNA genes revealed that there were some shifts in the microbial community structure unique to the presence of nanosilver. Future research may explore this further, especially with longer-term dosing, since this study took place in lab-scale simulated wastewater treatment plants over only about 8 weeks. Nonetheless, if there is ultimately good news that nanoparticles can be flushed safely down the drain without environmental impact, well, then that is good news! But, we will not know this for certain unless we test it out- and there are numerous more forms of nanoparticles that need investigating. The earlier we can identify the safest forms of nanoparticles, the better we can guide our “butterflies” in terms of the time and money invested in technological advances and hopefully avoid paying a grave price with unintended environmental consequences.


Amy Pruden

Amy Pruden is a professor of Civil & Environmental Engineering and Associate Dean for Interdisciplinary Graduate Education at Virginia Tech.

4 thoughts on “A Nanoparticle Flaps its Wings

  1. Amy,

    Thanks for the heads-up. and this interesting post.

    Apologies in advance if my questions are simply off-base, since I am neither a chemist nor a microbiologist. But from the perspective of a research architect (or building ecologist), I am curious to know how some of these things interact and affect each other and change in the dynamic processes — in water,in air, on surfaces, or anywhere in the processes that are constantly occurring in our built environment, especially those that affect human exposures.

    Can you clarify what you mean by the “forms” of nanoparticles. You wrote: “…The earlier we can identify the safest forms of nanoparticles, the better we can guide our “butterflies” …” What I gather is you are referring to the specific chemical compounds, and not to phiysical form (size, shape, denisty, etc).

    I was focused on the chemical composition but not the physical form of the nanoparticles as I read your post and looked through the manuscript, but now I am wondering whether I missed something — probably did, right? Since size, shape, and density can, at least theoretically, all play a role in the evolution (environmental fate) of the nanoparticles and, possibly the impacts you studied.

    Then going beyond your scope, can you comment on the research needs for nanoparticles released into indoor air and their potential impact on the indoor microbiome, airborne and on surfaces?

    Thanks in advance for any thoughts you might have on this

    1. Great questions, Hal. I am not only referring to the chemical forms of the nanomaterials (i.e., what material is at the center of the nanoparticle- such as gold, silver, cellulose, etc.), but also the diameter, coating, and chemical surface modification.

      A nanoparticle is somewhat arbitrarily defined as being within the 1 to 100 nanometer range. In reality, the precise diameter can make a difference in behavior, such as catalytic properties and aggregation tendency.

      The surface can be functionalized in all sorts of manners, including a coating to stabalize the particles, as well as the addition of a whole host of chemical groups– for example, pharmaceutically active chemicals for drug delivery or antibodies for pathogen detection.

      As far as implications for the built environment, besides entering our water system through disposal to the drain, they can also be emitted to the indoor air through use in consumer products such as a nanosilver hair dryer that was recently marketed to make the hair shine. They are also being impregnated in various materials as antimicrobials- I am not sure if they might be used as an antimicrobial in HVAC systems? For outdoor air, probably the main concern is combustion. For example, nanoceria is emitted from diesel engines. Linsey Marr is doing excellent work on understanding sources and behaviors of both indoor and outdoor nanoparticles.

      1. Thanks, Amy. More than I bargained for and very helpful.

        ASHRAE’s Environmental Health Committee is responsible for identifying “emerging issues.” Nanoparticles have been discussed as a possible topic, but not much has happened. I will make the committee aware of your work, paper, and your posts on microbe.net.

        Linsey Marr has done some great work and I have blogged about it on this web site. I will contact her to follow-up on that lead. thanks again.

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