Category Archives: Research

The Arctic was not what I expected

By Neal Bailey

I was surprised from the moment I stepped off the bush plane. No exposed rock, snow, or cold winds. Instead, a sunny and warm stretch of flat, mossy soil extended to a low crest of hills ahead. There were a handful of fuel barrels placed strategically across the landscape as markers – an attempt to impose some sort of border on the landscape. There was a cabin – Green Cabin; a single room with a table, some supplies, and a small camp oven. Everything else was the Arctic summer- the blaze of a sun that swung overhead in a perpetual arc. I hadn’t read that it would be hot. I had, however, read about the mosquitos. They saw us, correctly, as their only chance for blood, and I applaud their persistence. Persistence, in the Arctic, is key.

 

Banks_Island
Banks Island – Location of the Thomsen River

 

Aulavik sees few visitors; in a typical year, perhaps a dozen people set foot there. Usually, these few are either Parks Canada employees on a survey, or people looking for a chance to canoe up the most northerly navigable river in North America. The costs and conditions involved are both forbidding – planes need to be specially chartered, supplies need to be carried, and the terrain is vast and almost playfully unfriendly. The sheer isolation of the place is what makes it interesting to a scientist; here we have a corner of the world almost as far from human impacts as possible, and yet still the shadows of our influence loom. Each year, the winter grows softer and the summer season longer. The northern reaches of the Thomsen valley looked more like Scottish highlands than a classical Arctic scene; rolling terrain draped in bright green. Rain falls constantly, a stark contrast to the Arctic desert pictured in textbooks.

surprisingly green
Thomsen River Bank
surprisingly green 2
Grassy hillsides in northern Aulavik Park

As a researcher, I’d come to Aulavik to look at permafrost slumps, and how they chemically impact the aquatic ecosystem. The damage is obvious – jagged scars of black earth run down the sides of mountains, draining into muddy riverbanks below. It’s visible from miles away. What’s less visible is what is actually in the slumps. The clear water of the Thomsen River flows brown for kilometers downstream of the muddy wounds, but without samples to analyze, such descriptions are meaningless. So, we began a canoe trip spanning over 100 km, riding the Thomsen as it rolls into the Arctic Ocean.

Soils provide records of the past, and the sediments of Aulavik, locked in permafrost, tell a history different from the rocky spars of the eastern Arctic. Southern soils are sandy, dull and pale brown, whereas the northern reaches of the park darken to near black. Mounds of vegetation give way underfoot, releasing pools of tea-colored water in each footprint; in moments, those footprints vanish as the ground springs back, seemingly eager to erase any trace of our presence. Strange patterns of narrow gullies and raised hillocks stretch across the valleys, interspersed by shallow, dark lakes. No one has ever cultivated these lands, and nobody is sure what’s in the ground. This is why we need to gather samples from both the soil itself and the water in tandem.

slumps in the distance
Black streaks of visible permafrost slumping in Aulavik Park

Sample gathering for trace metals in water is challenging. Out in the field, in the snow and wind, there can be many complications. We needed two people for the clean hands-dirty hands protocol – one person is ‘clean hands’ and is the only one who comes into direct contact with the sampling environment, the samples themselves, and the containers that hold the samples. The other is ‘dirty hands’, and is responsible for handling more or less everything else. This method is designed to avoid contamination at all costs, and under harsh conditions it’s absolutely necessary to make sure everything is done properly. The biggest complication was never the weather, but the ‘wildlife’: when the temperature got above 6 degrees or so, bugs would start appearing, like some strange haze rising from the soil.

sampling
Water sampling in southern Aulavik Park

Thankfully it was usually too cold (we were in Canada’s coldest spot for a while there!) but when they could fly, they would fly into everything: sample bottles, gloves (as you’re putting them on), clothes, hair, ziplock bags, open mouths.

Permafrost cores were also collected. Depending on what’s in the permafrost, there are a huge variety of ways the slumps could impact the waters. Heavy metals such as mercury could find their way into phytoplankton, the base of the food chain. Mercury in particular can be methylated via bacterial processes and then easily sequester itself into basal biota, at which point it poses a risk to more complex forms of life further up the food chain [1]. Mercury was suspect number 1 in the tests we conducted.

Tests are ongoing, but initial analysis reveals a pristine river, with minimal mercury impacts in even the densest slumps. This, at least, is good news for the ecosystem. So far. Only total mercury concentration has been examined to date, and mercury’s toxicity varies drastically depending on speciation. Of key interest are organo-mercury compounds, which are not only very toxic but tend to sequester in tissue and biomagnify up the food chain [2,3]. Depending on the methyl mercury (and to a less extent dimethyl mercury, which usually degrades into methyl mercury in situ), the river’s fish population may have excessive mercury loads.

On the carbon side, chemical changes are obvious; the volume of soil and nutrients draining into the river from the permafrost melt is massive. Organic carbon compounds form the bedrock for all manner of food webs in natural waters, but whether this is good news or not is up for debate. Rapid changes in fragile, easily disturbed ecosystems have a habit of causing problems, even if it would at first appear that a simple equation of more food equals more productive river would apply. As we look into the specifics of the system, we can hopefully answer questions about the river’s health and apply them to similar Arctic ecosystems, many of which are changing rapidly today.

Neal Bailey studies environmental chemistry at University of Manitoba. Previously a writer, he was drawn to environmental science both for its contemporary relevance, and the option to work in both laboratory and natural environments.

References

  1. Chasar et al; Mercury Cycling in Stream Ecosystems. 3. Trophic Dynamics and Methylmercury Bioaccumulation; Environmental Science and Technology (2009), Vol 43 Issue 8 pp 2733-2739
  2. Morel F. M. M., Kraepiel A. M. L., Amyot M.; The Chemical Cycle and Bioaccumulation of Mercury; Annual Review of Ecology and Systematics (1998), Vol 29 pp 543-566
  3. Mason R. P., Reinfelder J. R., Morel F. M. M.; Bioaccumulation of Mercury and Methylmercury; Water Air and Soil Pollution (1995), Vol 80 Issue 1-4 pp 915-921

Our World at the Nanoscale

By Alexis Wormington

What are nanoparticles?

Nanoparticles are particles with at least one dimension sized on the nanoscale, which is usually defined as 1-100 nanometers1 (Figure 1). Put in simpler terms, nanoparticles are very small.

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Figure 1. The nanoscale2

Nanoparticles are on the same scale as many biomolecules, including antibodies, proteins, and sugars. We can’t see them, but, just like bacteria, they’re all over the place!

Where do nanoparticles come from?

Nanoparticles occur naturally in the environment – common sources include volcanic ash, ocean spray, dust, and sand3. Researchers are primarily interested in nanoparticles of synthetic (man-made) origin. Synthetic nanoparticles can be unintentional by-products of many commercial processes or intentionally synthesized for a variety of technological and industrial applications4. The latter are commonly referred to as engineered nanoparticles or engineered nanomaterials.

How do we use nanoparticles?

There are hundreds of different types of nanoparticles, and researchers are constantly engineering new ones in order to expand and invigorate the field of nanotechnology. Nanoparticles can be produced from a variety of elements, including carbon and metals such as titanium, gold, and silver.

Nanoparticles are interesting and useful because they have unique thermal, chemical, and optical properties compared to their larger, bulk elemental counterparts. These properties lend to a variety of applications, including those in the medical, environmental, engineering, technology, and commercial industries. Nanoparticles are often used as conductors in circuits and displays in electronic devices5, in textiles to improve or add functionalities (such as bacterial resistance, breathability, and strength6), as targeted drug-delivery vehicles in many cancer therapies7, and in environmental remediation efforts to bind and neutralize toxins.8

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Figure 2. The many applications of nanotechnology9.

In other words, nanoparticles are everywhere! For example, the active ingredient in most SPF (sun protection factor) cosmetics is zinc or titanium dioxide nanoparticles. Soon, carbon nanotubes will replace silicon as semi-conducting transistors inside of our computers and smartphones. Some make-up products even contain gold nanoparticles!

Nanoparticles sound awesome – should we be concerned about them?

In the last ten years, the presence of nano-enabled (contains nanoparticles or nanoscale materials) products on the consumer market has increased exponentially. The Project on Emerging Nanotechnologies works on documenting nano-enabled consumer products in something called a Consumer Products Inventory (CPI). As of 2014, the CPI lists 1814 nano-enabled products currently available on the consumer market, compared to just 54 products listed in 200510. That’s an average increase of 362% every year!

A consumer market full of nano-enabled products means that nanoparticles and nanomaterials will inevitably end up in the surrounding environment – which means the water we drink and the air we breathe. The Environmental Protection Agency is currently researching the “most prevalent nanomaterials that may have human and environmental health implications”, which includes silver nanoparticles, carbon nanotubes, cerium and titanium dioxide, iron nanoparticles, and copper nanoparticles11.

The health implications of exposure to nanoparticles vary depending on the type of particle and the route of exposure, but researchers have proposed that nanoparticles smaller than 10 nm can enter biological tissue12. Silver nanoparticles, utilized commonly in the textile industry for their antibacterial properties, release silver ions which are associated with mitochondrial and oxidative damage in both vertebrates and invertebrates13. A famous pilot study published in Nature Nanotechnology in 2008 found that commercially available carbon nanotube fibers induced mesothelioma-like pathologies in the abdominal cavity of mice due to their structural similarity to asbestos14. Copper oxide nanoparticles, used not only as a semi-conductor but as the active spermicide in many intrauterine devices (a form of long-term birth control), are associated with multiple organ-level effects in experimental organisms15.

There are many organizations around the world that specialize in nanosafety research. These research groups focus on understanding the behavior of nanoparticles throughout the life cycle (manufacturing, product use, and disposal) in order to determine whether they pose a potential threat to humans or the environment11. This can be a daunting task – because some types of nanomaterials are more harmful than others, and some exposure scenarios are more relevant than others (i.e. inhalation versus ingestion versus injection). Nanoparticles are also maddeningly difficult to detect, which makes studying them a headache! For example, detecting carbon nanotubes in biological tissues is often described as “searching for a carbon needle in a carbon haystack”, and detection methods are still being optimized. Detection methods vary for different types of nanoparticles and range from microscopic methods (such as transmission electron microscopy), to light scattering methods, to spectroscopy techniques, to x-ray based methods16. Often times, researchers will send their samples off to another lab for quantification, because they simply do not have the proper equipment at hand!

Nanoparticles, while useful and incredibly versatile, should be approached with caution. The research on them is still in the preliminary stages, and there is still much we do not know about their potential effects on human and environmental health. As the field of nanotechnology grows, it is important to remain informed and vigilant to ensure that these particles are used safely and efficiently.

alexis


Alexis Wormington
is a PhD Student at the Center for Environmental Toxicology & Chemistry at the University of Florida. Her research is focused on the toxicity of nanomaterials in aquatic ecosystems.

 

References 

  1. “Nanomaterials.” National Institutes of Environmental Health Sciences. National Institute of Health, n.d. Web. 11 Jan. 2017.
  2. Tarafdar, J.C., Adhikari, T. (2015). Nanotechnology in Soil Science. In Ratten, R.K. et al (Eds.), Soil Science: An Introduction (pp 775-807).
  3. Lohse, Sam. “Nanoparticles Are All Around Us.” Blog post. Sustainable Nano. Center for Sustainable Nanotechnology, 25 Mar. 2013. Web. 11 Jan. 2017.
  4. org. “The Future Belongs to Nano.” Omni Nano – The Curriculum to Inspire the Scientists, Entrepreneurs and Engineers of Tomorrow! N.p., n.d. Web. 03 Feb. 2017.
  5. Bhatia, S., Raman, A., & Lal, N. (2013). The shift from Microelectronics to Nanoelectronics: a review. Internat J Advanc Res Comp Communic Engin, 2, 11.
  6. Rivero, P. J., Urrutia, A., Goicoechea, J., & Arregui, F. J. (2015). Nanomaterials for functional textiles and fibers. Nanoscale research letters, 10(1), 501.
  7. Salata, O. V. (2004). Applications of nanoparticles in biology and medicine. Journal of nanobiotechnology, 2(1), 3.
  8. Khin, M. M., Nair, A. S., Babu, V. J., Murugan, R., & Ramakrishna, S. (2012). A review on nanomaterials for environmental remediation. Energy & Environmental Science, 5(8), 8075-8109.
  9. Buzea, C., Pacheco, I. I., & Robbie, K. (2007). Nanomaterials and nanoparticles: Sources and toxicity. Biointerphases, 2(4), MR17-MR71.
  10. Vance, M. E., Kuiken, T., Vejerano, E. P., McGinnis, S. P., Hochella, M. F., Jr., Rejeski, D. and Hull, M. S. (2015). Nanotechnology in the real world: Redeveloping the nanomaterial consumer products inventory. Beilstein Journal of Nanotechnology, 6, 1769-1780.
  11. “Research on Nanomaterials.” EPA. Environmental Protection Agency, 18 Oct. 2016. Web. 11 Jan. 2017.
  12. Bahadar, H., Maqbool, F., Niaz, K., & Abdollahi, M. (2015). Toxicity of Nanoparticles and an Overview of Current Experimental Models. Iranian biomedical journal, 20(1), 1-11.
  13. Stensberg, M. C., Wei, Q., McLamore, E. S., Porterfield, D. M., Wei, A., & Sepúlveda, M. S. (2011). Toxicological studies on silver nanoparticles: challenges and opportunities in assessment, monitoring and imaging. Nanomedicine, 6(5), 879-898.
  14. Poland, C. A., Duffin, R., Kinloch, I., Maynard, A., Wallace, W. A., Seaton, A., … & Donaldson, K. (2008). Carbon nanotubes introduced into the abdominal cavity of mice show asbestos-like pathogenicity in a pilot study. Nature nanotechnology, 3(7), 423-428.
  15. Bahadar, H., Maqbool, F., Niaz, K., & Abdollahi, M. (2015). Toxicity of Nanoparticles and an Overview of Current Experimental Models. Iranian biomedical journal, 20(1), 1-11.
  16. López-Serrano, A., Olivas, R. M., Landaluze, J. S., & Cámara, C. (2014). Nanoparticles: a global vision. Characterization, separation, and quantification methods. Potential environmental and health impact. Analytical Methods, 6(1), 38-56.

How I ended up in the Arctic

By Sara Pedro

I became interested in contamination of the polar regions during my master’s while researching mercury concentrations in Antarctic Gentoo penguins (Pygoscelis papua). This species spends their complete life cycle in many of the sub-Antarctic islands, such as South Georgia and the Kerguelen Islands, and reproduce in colonies of about 320 000 breeding pairs (Borboroglu and Boersma 2013). Because of their large numbers, wide distribution in the Antarctic Ocean, and easy access, Gentoo penguins are good biomonitors of local contaminant concentrations; a major reason we studied this species. We found that mercury concentrations in Gentoo penguins were not at concerning levels (Pedro et al. 2015). Nevertheless, the fact that mercury accumulates in species in the Antarctic, one of the most remote regions in the world, indicates the widespread contamination of pollutants released mostly in industrialized areas.

In transitioning to my PhD, I switched poles to focus on the Arctic. Like in the Antarctic, the Arctic region is impacted by global pollution. At the same time, the Arctic has been facing marked sea-ice loss associated with increasing temperatures. The Arctic is more susceptible to these changes in climate than other regions around the globe (Screen and Simmonds 2010) due to the albedo effect: less sea-ice to reflect solar radiation leads to more absorption by the ‘darker’ ocean surface. Because contaminants are transported by air and oceanic currents, climate change will likely alter contaminant dynamics and pathways into Arctic ecosystems (Macdonald et al. 2005). One situation that leads to this change in contaminant dynamics is the alteration of Arctic food web structure, such as the replacement of native with invasive prey fish.

My current PhD project at the University of Connecticut focuses on legacy persistent organic pollutants (POPs) and mercury in invasive versus native prey fish in the Eastern Canadian Arctic, and consequent levels in ringed seals (Pusa hispida). Legacy POPs include several pesticides and polychlorinated biphenyls (PCBs) that can travel long distances, often by atmospheric transport, eventually accumulating in remote regions. These POPs take a long time to break down in the environment, and can accumulate in animals to potentially cause toxic effects (Letcher et al. 2010). Mercury is released mainly during gold mining and coal burning and is transported to remote regions where, similarly to POPs, it can accumulate in the food web and cause toxic effects (Dietz et al. 2013).

With the recent increases in average temperatures in the Arctic, some fish species have expanded their habitat ranges from boreal areas to more northern regions and are now found more frequently in the Canadian Arctic. Studies on Arctic seabird and marine mammal diets suggest that invasive fish such as capelin (Mallotus villosus) and sand lance (Ammodytes sp.) are replacing Arctic cod (Boreogadus saida) as the most important prey species in lower Arctic regions (Provencher et al. 2012; Chambellant et al. 2013; Hop and Gjøsæter 2013). Although POPs and mercury are transported to the Arctic, they are still at higher environmental levels closer to the direct sources (e.g. intense agricultural areas, waste incineration). A switch in diet from native to invasive fishes may therefore change ringed seal contaminant burdens. My PhD research will compare contaminant levels in invasive capelin and sand lance to Arctic native fish species, including Arctic cod. I will also determine contaminant levels in ringed seals to better understand how climate change impacts contaminant transfer in Arctic food webs. The results of this project are also important for local communities because, although they do not eat these invasive and native Arctic fishes in particular, locals eat Arctic marine mammals, such as ringed seals that feed on these fishes.

Part of this project includes visiting the local communities in the Arctic that are the most affected by these habitat changes. Arviat, Nunavut is one of the communities collaborating in this project and participated in collecting fish samples. This was my opportunity to visit the Arctic! Last spring, I flew up to Arviat (Figure 1) and gave a few talks regarding preliminary results of my research at the high school, the Arctic College, and the Hunters and Trappers Association.

Figure 1: Town of Arviat, Nunavut (left) in the Eastern Canadian Arctic (right).

My visit in April was short and sweet, consisting of 4 different flights each way… 8 flights in three days (luckily, none of the flights were delayed)! Given the thaw doesn’t happen until June/July in Arviat, late April means snow boots and warm coats. Hudson Bay was a beautiful, expansive white plain (Figure 2)! However, I could tell that it was the spring for them. The locals were walking on the streets, kids were out playing and the roads were clear enough to easily drive through. Everyone looked happy and they were very welcoming. At the high school, I gave a few talks to different classes about my research. The students were interested and engaged, and I even got the wise question “So why does this matter?” from a 12-year-old. Another girl told me that she didn’t like fish and when I asked what she eats instead, she told me about how her father hunts caribou. She invited me to join them on a hunt. If it weren’t for my tight schedule, I would have definitely gone out for a caribou hunt! In this region, they mostly depend on caribou (Rangifer tarandus), seals, and Arctic char (Salvelinus alpinus) for subsistence. High school students will often miss classes and come in tired because the main priority for many of them is to help their families hunt and fish.

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Figure 2: Frozen Hudson Bay in Arviat, NU

After visiting the high school, I went to the Arctic College (Figure 3). Most of the students were gone for the summer but I met a few that stick around and volunteer for research projects. Getting locals involved in environmental research in these remote regions is very important given their sensitivity to climate change and environmental pollution. Fishers and hunters at the Hunters and Trappers Association are concerned about having contaminants in their food, since they depend largely on local food sources. The Arctic Monitoring and Assessment Program (AMAP) has been monitoring contaminants in the Canadian Arctic for over twenty years. The levels of some POPs, such as DDT and PCBs have been declining or have stabilized in the Arctic, mostly since the Stockholm Convention to ban these contaminants (Stockholm Convention 2008). However other contaminants such as mercury have been increasing in some Arctic animals (Riget et al. 2010; McKinney et al. 2015). As a polar environmental scientist, it is my duty to continue researching the impacts of climate change on contaminant levels in these remote regions and to address the communities’ questions and concerns.

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Figure 3: Arctic College, Arviat, NU

Being able to visit one of the most fascinating regions in the world while doing environmental research is why I enjoy being a scientist!

Sara Pedro has a Master’s in Ecology and is currently a PhD student in the Natural Resources and the Environment department of the University of Connecticut, CT.

References:

Borboroglu PG, Boersma PD (2013) Penguins: Natural History and Conservation. University of Washington Press, Seattle

Chambellant M, Stirling I, Ferguson SH (2013) Temporal variation in western Hudson Bay ringed seal (Phoca hispida) diet in relation to environment. Mar Ecol Prog Ser 481:269.

Dietz R, Sonne C, Basu N, et al (2013) What are the toxicological effects of mercury in Arctic biota? Sci Total Environ 443:775–790. doi: 10.1016/j.scitotenv.2012.11.046

Hop H, Gjøsæter H (2013) Polar cod (Boreogadus saida) and capelin (Mallotus villosus) as key species in marine food webs of the Arctic and the Barents Sea. Mar Biol Res 9:878–894.

Letcher RJ, Bustnes JO, Dietz R, et al (2010) Exposure and effects assessment of persistent organohalogen contaminants in arctic wildlife and fish. Sci Total Environ 408:2995–3043. doi: 10.1016/j.scitotenv.2009.10.038

Macdonald RW, Harner T, Fyfe J (2005) Recent climate change in the Arctic and its impact on contaminant pathways and interpretation of temporal trend data. Sci Total Environ 342:5–86. doi: 10.1016/j.scitotenv.2004.12.059

McKinney MA, Pedro S, Dietz R, et al (2015) A review of ecological impacts of global climate change on persistent organic pollutant and mercury pathways and exposures in arctic marine ecosystems. Curr Zool 61:617–628.

Pedro S, Xavier JC, Tavares S, et al (2015) Mercury accumulation in gentoo penguins Pygoscelis papua: spatial, temporal and sexual intraspecific variations. Polar Biol. doi: 10.1007/s00300-015-1697-9

Provencher JF, Gaston  AJ, O’Hara PD, Gilchrist HG (2012) Seabird diet indicates changing Arctic marine communities in eastern Canada. Mar Ecol Prog Ser 454:171–182. doi: 10.3354/meps09299

Riget F, Bignert A, Braune B, et al (2010) Temporal trends of legacy POPs in Arctic biota, an update. Sci Total Environ 408:2874–2884. doi: 10.1016/j.scitotenv.2009.07.036

Screen JA, Simmonds I (2010) The central role of diminishing sea ice in recent Arctic temperature amplification. Nature 464:1334–1337. doi: 10.1038/nature09051

Stockholm Convention (2008) Listing of POPs in the Stockholm Convention. http://chm.pops.int/TheConvention/ThePOPs/ListingofPOPs/tabid/2509/Default.aspx. Accessed 28 May 2015

Human Exposure to Pharmaceuticals via Vegetables: Current Research and Future Directions

By Sara Nason

Like many scientists, I often find myself explaining my research to my friends and family.  However, I am usually hesitant to launch into a full explanation of my projects, as most people are not as interested in the mechanisms of how plants take up pharmaceuticals as I am. As soon as I start describing my research, all sorts of questions come up – most of which are not directly related to my work.

When deciding on a topic to write about for the SETAC student blog, I considered focusing on the research that I work on every day.  However, I would probably digress into a detailed description using lots of scientific jargon, and my blog entry would not be very exciting.  Instead, this post is about an issue that often comes up when I discuss my research with someone outside of my field – human exposure to pharmaceuticals that have been taken up by crop plants.  Specifically, I focus here on a recent paper in Environmental Science and Technology by Ora Paltiel and others: Human exposure to wastewater-derived pharmaceuticals in fresh produce: A randomized controlled trial focusing on carbamazepine.1

Scientists working at the Hebrew University of Jerusalem recently detected carbamazepine, an anti-epileptic drug, in the urine of people eating vegetables that were irrigated with treated wastewater.  This is the first study to demonstrate that pharmaceutical contamination in irrigation water results in human exposure to pharmaceuticals via consumption of irrigated crops.

Researchers provided study participants with a box of vegetables to consume over the course of a week. Some participants received vegetables grown with freshwater irrigation, while others received vegetables grown using treated wastewater irrigation. New boxes were provided the following week that only contained vegetables irrigated with freshwater.  The scientists collected urine samples from the participants throughout the two weeks, and found that urine concentrations of carbamazepine increased during the first week for participants eating the treated wastewater vegetables, but not for the freshwater group.  Carbamazepine levels returned to baseline levels by the end of the second week.

Irrigation using treated wastewater is a surprisingly common practice worldwide, especially in arid locations.  In California, where most of the produce in the United States is grown, nearly half of treated wastewater is used for agriculture, and in Israel, more than 70% of treated wastewater is used directly for irrigating crops.2 Pharmaceuticals enter the wastewater treatment system because humans and animals do not fully break down most drugs and a significant portion is excreted in urine. Even in fully industrialized nations, most wastewater treatment does not fully remove pharmaceuticals, so the chemicals go wherever the treated wastewater goes – into lakes, rivers, and streams, or directly onto crop plants.

Plant uptake of pharmaceuticals became a topic of concern starting about 10 years ago, after several studies found pharmaceuticals in run-off water from crop fields.  The first few years of research focused largely on proof-of-concept experiments – tests where plants were grown in labs and greenhouses and exposed to higher concentrations of pharmaceuticals than are typically found in the environment.  These studies showed that plants can take up many types of pharmaceuticals.  More recent studies have investigated exposures to lower concentrations of pharmaceuticals using plants grown in more realistic scenarios, showing that the potential for plants to take up pharmaceuticals in standard agricultural systems clearly exists.3

The big question that is still up for debate is whether or not human exposure to pharmaceuticals via consumption of contaminated crops might have impacts on human health. Within the big question, there are two smaller questions that are the focus of current research.

PPCPFlowchart
Figure 1: A recent publication demonstrates that people can be exposed to pharmaceuticals by eating vegetables that were irrigated with treated wastewater. Continuing research focuses on understanding the exposure pathway well enough to predict any potential health impacts.

First, we need to know more about the effects low concentrations of pharmaceuticals may have on human health – at what amount (in plants) will pharmaceuticals begin to have an effect on people?  Pharmaceuticals in the environment are usually present as mixtures, so although the concentration of each one may not be close to a normal therapeutic dose, there could be unexpected effects from drug mixtures and interactions.  While scientists are currently researching the effects of very low doses of pharmaceutical mixtures, much of the research that has been done so far has focused on model organisms for aquatic ecosystems, such as water fleas, zebra fish, and minnows, rather than on plants and humans. Most human risk assessment so far has used estimates of toxicity based on the molecular structure of pharmaceuticals and not on experimental data.

Second, we need to have a better understanding of how much of different pharmaceuticals is being taken up by crop plants in the field – enough to meet the threshold for effects on humans? While more than 100 pharmaceuticals have been studied in plant uptake experiments,3 thousands more are currently in use, with new drugs constantly being developed.  Testing all produce samples for the presence of pharmaceuticals is highly impractical, so accurate predictions of plant uptake are necessary. Some scientists have attempted to use models to predict plant uptake, but there are still large gaps in our understanding of the biological and chemical processes involved.

My research focuses on these knowledge gaps – I look at variables such as soil pH, nutrient availability, and toxicity of pharmaceuticals to plants – factors that may affect how much of a pharmaceutical can enter and accumulate in a plant. I work with model organisms and do a lot of method development – things that don’t feel relevant to the outside world by themselves. Reading articles like the one described above and thinking about the larger questions connected to my research makes me feel like a part of the greater scientific community and like I am doing something of significance for the world.  I think that is one of the great things about being in the environmental toxicology and chemistry field.  It will be exciting to see where the science goes next!

Sara Nason is a PhD student in Environmental Chemistry and Technology at the University of Wisconsin-Madison

References:

(1)        Paltiel, O.; Fedorova, G.; Tadmor, G.; Kleinstern, G.; Maor, Y.; Chefetz, B. Human exposure to wastewater-derived pharmaceuticals in fresh produce: A randomized controlled trial focusing on carbamazepine. Environ. Sci. Technol. 2016, acs.est.5b06256.

(2)        Sato, T.; Qadir, M.; Yamamoto, S.; Endo, T.; Zahoor, A. Global, regional, and country level need for data on wastewater generation, treatment, and use. Agric. Water Manag. 2013, 130, 1–13.

(3)        Miller, E. L.; Nason, S. L.; Karthikeyan, K.; Pedersen, J. A. Root Uptake of Pharmaceutical and Personal Care Product Ingredients. Environ. Sci. Technol. 2015, acs.est.5b01546.

Antimicrobial Soaps and Other Products of Questionable Necessity

By David Faulkner

We’ve all seen phrases like “anti-bacterial” and “anti-microbial” emblazoned across aisles of imperious bottles of various soaps, and increasingly in other products such as cutting boards, gym bags and socks. But what is the purpose of antimicrobial compounds in these products? And do we truly need antimicrobial compounds to clean ourselves? The answers are nuanced, and depend on the product in question, but to begin with, we will consider a narrower case, for which there is ample evidence: hand soaps. To discuss the necessity of antimicrobials in hand soaps, let us begin by considering the process of hand washing to begin with.

We wash our hands to reduce disease transmission, and study after study has shown that proper hand washing before preparing and eating food can dramatically reduce rates of diarrheal diseases. Additional studies (1,2) have indicated that stringent hand washing regimens are vital in combating disease outbreaks in hospitals. Unfortunately, most of us don’t wash our hands for the recommended twenty seconds of scrubbing. In fact, one study found that health care workers washed their hands for just under nine seconds on average, while non-healthcare workers spent a little over four seconds at the faucet. The problem with this, is that while it may be satisfying to work up a good lather and rinse it off, the friction of rubbing your hands together and the flow of water to carry the bacteria away are the key to removing unwanted dirt and microbes. And the soap, while helpful for dislodging stubborn dirt and biofilms, is probably not as important as the running water when it comes to removing harmful bacteria – assuming that you’re washing properly. Why, then, is antibacterial soap so popular?

Part of the reason why antibacterial soaps are popular is because they’re useful: multiple studies have shown that they can be used effectively to control outbreaks of hospital-born illnesses, and the FDA has determined that the popular antimicrobial agent Triclosan is useful for controlling cavities and gum disease when added to toothpaste. Most people know that bacteria can make us sick, so it’s natural to think that if regular soap is good, then antibacterial soap must be better. Unfortunately, there’s not much evidence that this is the case for most products, in part because the concentration of antimicrobials found in consumer hand soaps is much lower than the concentrations used in hospital hand soaps, and in part because most people don’t wash their hands for long enough for it to matter anyway. But good marketing is good marketing, and consequently, antibacterial agents like Triclosan has been added to soaps and a menagerie of other products on the premise that it will kill the bacteria that cause disease and unpleasant odors – although the latter claim is even more questionable.

Triclosan is an antimicrobial agent, meaning that it kills microorganisms like bacteria and fungi. It’s considered a broad-spectrum antimicrobial because it can kill a wide variety of microbes, rather than only a specific type. This is because one of the ways that it kills microbial cells is by disrupting the membranes that make up the exterior and inner compartments of the cells, causing their contents to leak. There are several other ways that Triclosan kills bacteria, and one of them is similar to the way that other antibiotics kill bacteria – meaning that if bacteria develop resistance to Triclosan, they may become resistant to other antibiotics as well.  Resistance develops when a few bacteria survive an exposure to Triclosan, and they do so because they have developed mutations in their genes that protect them from the chemical. These bacteria then proliferate and can pass the Triclosan-resistance genes on to other bacteria, making them immune as well! Antibiotic resistance affects over 2 million people in the United States each year – some lethally so – and those numbers are increasing. One study found that by the year 2050, antibiotic resistance may cost the world economy over $100 trillion USD (4).

Unfortunately, the risk of antibiotic resistance is not the only reason why we need to reconsider the use of Triclosan in consumer products: growing evidence suggests that it may pose a hazard to human and environmental health as well (5, 6, 7). Much of the Triclosan that enters the environment does so via our sinks and drains when we wash our hands or brush our teeth with products that contain the compound. Not all water treatment processes destroy Triclosan, and the compound may be released into the environment with the rest of the treated effluent, whereupon exposure to direct sunlight can cause Triclosan to break down into molecules from a potent class of environmental contaminants: dioxins. Algae and other aquatic microorganisms can absorb the Triclosan that doesn’t break down in the sunlight, causing the compound to accumulate in the fish and other animals that eat them. High doses of Triclosan have been shown to affect the swimming ability of fish and to disrupt the function of their muscles, and a number of studies have indicated that Triclosan may cause endocrine disruption in mammals although the specific mechanism by which it does so is poorly understood (6, 7, 8, 9, 10).

All of this is to say that while antibacterial compounds such as Triclosan do have their uses – and are indeed quite effective when used judiciously – they probably aren’t necessary in hand soaps, and may do more harm than good when overused. So while it may be tempting to battle germs with antibacterial soaps, the best thing to do is to simply take your time at the sink. Maybe sing the “Happy Birthday” song once or twice?

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Faulkner

David Faulkner is a PhD Candidate in Molecular Toxicology at The University of California at Berkeley. He has a few degrees from the University of Michigan, including a Master’s of Public Health. David’s research interests include green chemistry and hazard assessment of industrial toxicants. In his free time, he enjoys running, writing, and YouTube Videos.

Sources Cited:

  1. Jones, Rhonda D., Hanuman B. Jampani, Jerry L. Newman, and Andrew S. Lee. “Triclosan: a review of effectiveness and safety in health care settings.”American journal of infection control28, no. 2 (2000): 184-196.
  2. Pittet, Didier. “Compliance with hand disinfection and its impact on hospital-acquired infections.” Journal of Hospital Infection 48 (2001): S40-S46.
  3. Arias, Cesar A., and Barbara E. Murray. “A new antibiotic and the evolution of resistance.” New England Journal of Medicine 372, no. 12 (2015): 1168-1170.
  4. Review on Antimicrobial Resistance (London)., and Grande-Bretagne. Antimicrobial resistance: tackling a crisis for the health and wealth of nations. Review on Antimicrobial Resistance, 2014.
  5. Fang, Jia-Long, Robin L. Stingley, Frederick A. Beland, Wafa Harrouk, Debbie L. Lumpkins, and Paul Howard. “Occurrence, efficacy, metabolism, and toxicity of triclosan.” Journal of Environmental Science and Health, Part C 28, no. 3 (2010): 147-171.
  6. Yueh, Mei-Fei, and Robert H. Tukey. “Triclosan: a widespread environmental toxicant with many biological effects.” Annual review of pharmacology and toxicology 56 (2016): 251-272.
  7. Chalew, Talia EA, and Rolf U. Halden. “Environmental exposure of aquatic and terrestrial biota to triclosan and triclocarban1.” JAWRA Journal of the American Water Resources Association 45, no. 1 (2009): 4-13.
  8. Cherednichenko, Gennady, Rui Zhang, Roger A. Bannister, Valeriy Timofeyev, Ning Li, Erika B. Fritsch, Wei Feng et al. “Triclosan impairs excitation–contraction coupling and Ca2+ dynamics in striated muscle.” Proceedings of the National Academy of Sciences 109, no. 35 (2012): 14158-14163.
  9. Fritsch, Erika B., Richard E. Connon, Inge Werner, Rebecca E. Davies, Sebastian Beggel, Wei Feng, and Isaac N. Pessah. “Triclosan impairs swimming behavior and alters expression of excitation-contraction coupling proteins in fathead minnow (Pimephales promelas).” Environmental science & technology 47, no. 4 (2013): 2008-2017.
  10. Stoker, Tammy E., Emily K. Gibson, and Leah M. Zorrilla. “Triclosan exposure modulates estrogen-dependent responses in the female wistar rat.” Toxicological Sciences (2010): kfq180.