Team:Concordia/Safety/NPEssay
Nanoparticles and their Effects on the Environment: A Gray Area
By Concordia University’s iGEM Team 2016
An Introduction to Nanoparticles
Nanotechnology, an emerging field of science which combines engineering, biology, and chemistry, specializes in the study of nanometer-scale materials and their potential applications. Among such nanomaterials are “nanoparticles”, or particles that range in diameter between 0 and 100 nanometers (1). Nanoparticles is a broad term used to describe an incredible plethora of nano-sized substances that vary in property in terms of size, shape and composition (1). They are found both in nature and may also be manufactured synthetically. For instance, nanoparticles can be generated using materials such as gold, silver, silica, or titanium, to name a few. The variety of unique characteristics of these particles has made their study and application an impressionable area of research and industry. A notable feature of these nanoparticles is their nano-scale dimensions which influence their properties - their use is dependent on their size, where they are found to have a larger surface area to volume ratio compared to their larger-scale versions (1). The inherent complexity of nanoparticles and the ability of scientists to manipulate their structure allows nanotechnologists to utilize them for a diverse range of purposes, including but not limited to cosmetics, material coatings, as tools for mechanical engineering, in the design of electronic devices, materials in biomedical applications like drug delivery, for imaging, and in the transportation industry (2). For example, nanoparticles are used as a coating for glassware in order to prevent scratch marks, in sunscreens as a light-reflecting element, and also as devices to enhance the capacity for diagnostic work (3, 4, 5). Although the field of nanotechnology had only begun developing as of 1959, its popularity truly flourished into the late 1980’s and it continues to grow with time as scientists are now uncovering and exploring the potential employments of such substances (6).
Their Environmental Impact: A Lacking Subject
While the number of industrial and laboratory nanoparticle users has skyrocketed since the 1980’s, the amount of research that has been done to assess both the environmental impact and human health effects of nanoparticles has not kept up. The manufacturing of products made of, with or even simply containing nanoparticles and also the engineering of nanoparticles themselves has spiked, without a balancing amount of research to ensure adequate safety for the users of these substances (7). In fact, millions of tons of these nanoparticle products are being produced yearly - a concerning quantity considering the lack of knowledge on the long-term effects of nanoparticle exposure, as well as the cause-and-effect health impacts, and finite maximum exposure limits are not well-established in some cases (7). Without the data to fill in this missing information, it is concerning to realize that many household products, such as deodorants and sunscreens, do not contain a warning label to notify consumers of their nanoparticle content (13). The reason for alarm is founded in the small amount of nanoparticle research that has been conducted with respect to environmental impact and in relation to human health. Furthermore, cases of nanoparticle hazards in the laboratory have also been documented. For instance, a case was reported that in a poorly ventilated Chinese factory where two female workers who were responsible for spraying paint containing nanoparticles and that has not been wearing proper personal protective equipment, became very ill and perished as a result of nanoparticle exposure (14). It is cases like these that bring to light, the importance of understanding the implications associated with nanoparticle usage and exposure.
To make matters worse, environmentalists foresee a drastic increase in the concentration of nanoparticles that will be exposed to the environment as their usage continues to rise. Environmentalists need to further research whether this will pose a risk or not. Researching the environmental effects that certain nanoparticles may impose requires the consideration of the following factors: identifying the type of nanoparticle, quantifying the amount of nanoparticles reaching the environment, and observing the life-cycle of these nanoparticles within the specific environment they were released into (8). More specifically, the life-cycle of nanoparticles encompasses both the diffusion patterns and chemical reactions that occur as a result of existing within the environments they are released (8). Then, upon assessing both the potential long-term and the short-term effects of the presence of these nanoparticles in question, the level of hazard can be determined (8). As straight-forward as the research process may appear, environmentalists are faced with many challenges when analyzing the impacts of nanoparticles. Henceforth, the amount of available information on the effects of nanoparticles on the environment is unfortunately lacking for this reason and several others. One such additional reason is likely the worry from corporations that the research may show how nanoparticles are more harmful than we currently perceive, and that the best way to cope would be to remove their usage from within the numerous products they are found. This would be monetarily harmful to the many companies and associations that use nanoparticles and sell products that benefit from their use. In this essay, the many reasons will be further discussed, as well as the imperative for determining and providing the information on their environmental impacts of nanoparticles.
Figure 1 - Average global outputs of engineered nanomaterials (10).
Put Simply: Toxicity to the Environment
Before delving into the many issues that account for the insufficient amount of information available to the public regarding the environmental effects of nanoparticles, it is noteworthy to mention what it takes for a substance to be officially declared “toxic.” In general, a substance is classified as toxic if it in any way proves to be harmful toward a biological process or organism (8). With specific regard to the environment, a material can only be considered a risk if it has the capacity to be exposed to the ecosystem and if it can garner significant negative consequences as a result of that exposure (8).
[1] Release of Nanoparticles into the Environment
It is important to identify the source of released nanoparticles, since it is considered the start of the nanoparticle life-cycle within the environment - an important factor in risk assessment (8).
As previously described, nanoparticles can be generated in nature and thus have existed long before mankind. With innovation though, humans now have the capacity to also synthetically produce nanoparticles. The sources of nanoparticle production are organized into so called ‘classified sources’ (9). Two main classified branches of such sources are those which produce nanoparticles unintentionally and those which produce particles intentionally (9). Unintentionally generated nanoparticles are usually found in the atmosphere and are typically sized between 1 and 10 nm (9). Due to the small size of these particles, they are referred to as ‘ultrafine’ particles (9). Their ultrafine size is what makes them more harmful to biological organisms, since this property facilitates the possibility of their inhalation or passage across biological cell membranes in the case of bodily contact (9). For this particular reason, the concentration of ultrafine nanoparticles in the atmosphere is monitored and regulated by air quality agencies (9). A method in which this is monitored is by using chemical or electric ventilation air filters to capture these particles by size distribution as they diffuse through the atmosphere (9).
The classification of unintentionally produced nanoparticles can be further broken down into ‘primary’ and ‘secondary’ unintentionally produced nanoparticles (9). Primary unintentionally produced nanoparticles are directly released from the source or process of generation (9). This can occur naturally from a fire, a volcano, from sea spray, or through erosion of materials (9). Primary particles may also be released unnaturally, via human activity through emissions produced either by traffic due to human transportation methods or by factories (9). The major sources for primary ultrafine nanoparticles occur due to transport by road travel and through combustion processes, including industrial, commercial, residential combustion and energy production (9). On the other hand, secondary unintentionally produced particles are formed by gas-to-particle transformations which occur in the atmosphere and grow by coagulation or by adhering to other particles in the environment (9).
The other major classification of nanoparticles, are those that fit into the category of being intentionally produced (9). For example, nanoparticles have been manufactured by industrial companies for decades for their use in skin care products and for structural applications (9). They have also been engineered and tailored by biotechnologists to be suitable for targeted drug delivery, as biosensors, diagnostic markers, and also by environmentalists for nanofiltration purposes (9). Unfortunately, the toxicity data that would complement manufactured nanoparticles is often unavailable (9). Of the toxicological data that does exist, most work on nanoparticles has been done with carbon black (CB), titanium dioxide (TiO2), iron oxides and amorphous silica nanomaterials (9). Nanoparticles composed of these substances are produced in quantities measurable up to several tons per year (9). More often than not, these nanoparticles are neglected within working environments and mistaken for dust, until further investigated once individuals experience health effects (9). It was observed that prolonged exposure to these nanoparticles in rats can cause inflammation and lung tumours (9). It was also noticed that the production and release of these nanoparticles contributes to the increase in total concentration of ultrafine nanoparticles found within the atmosphere (9). In turn, this contributes to an increase in the mortality rate from a respiratory disease (9).
The many ways in which nanoparticles can be released into the environment collectively blur the understanding of their specific effects on the environment. Moreover, an environment may be occupied by more than one type of nanoparticle (9). This makes it difficult to carry out a risk assessment, as results may be influenced by the presence of other nanoparticles (9). Also, it is possible for a single type of nanoparticle to have been released by multiple sources (9). For these reasons, it is hard to depict the start of a life cycle for a particular nanoparticle, which leads to difficulties ineffectively initiating an appropriate filtration or cleansing process for remediation (9).
Figure 2 - Possible pathways for nanoparticle entry into the environment, how they react within the environment and how they reach living organisms (9).
[2] Diversity of Nanoparticles
Composition, size and shape are all factors which are accounted for when assessing the toxicity of nanoparticles. The extensive variety of nanoparticles that exist thereby pose a challenge to toxicologists (8). Atop the great diversity of nanoparticles are considerations that need to be made in terms of assessing nanoparticle concentrations within given environments, while also examining the environmental conditions themselves (8). These numerous variables create a unique circumstance when evaluating the toxicity of a given nanoparticle under certain conditions. In other words, when performing a risk assessment, the observations made and the level of toxicity that is deemed appropriate, apply to that situation in question exclusively. Should any variable differ from another circumstance between assessments, then it would not be sensible to make a comparison or prediction between those given situations (9).
The main reason for the inability to apply the same assessment between nanoparticles in different environments is due to the fact that the behavior and properties of nanoparticles are size-dependent, introducing an increasing level of complexity to each assessment (9). For example, titanium dioxide and zinc oxide nanoparticles can both absorb short wavelengths of UV radiation and emit longer wavelengths of visible light, being size-dependent properties, despite their differing material composition (10). Their light-reflecting property is the reason these specific nanoparticles have become a typical ingredient in the production of sunscreens and also used as diagnostic markers (10). Further on the matter of light reflection, it is notable that the colour or wavelength of light emitted from nanoparticles with varying diameters were different, indicating that nanoparticles which differ in size almost act as different chemical substances (10). Given the immense number of possible properties a nanoparticle may hold as well as the various environments in which they may exist, it is understandable that researching each and every one within each condition would take a very long time.
Figure 3 - A look at various nanoparticle classifications (9).
[3] Nanoparticle Toxicity to Living Organisms
While there is concern for the implications of nanoparticle exposure to the environment, this also raises the issue of how humans and other living organisms can be impacted. The main reason as to why nanoparticles can be considered toxic is due to the fact that their size ranges on the scale of 0 to 100 nanometers (2). Their tiny size permits their passage into cells if placed into contact with living tissue, which is dangerous since their presence has the capacity to disrupt many biological processes essential for cell survival (2). Normally within cells, metals such as copper, potassium, sodium, calcium, iron, and magnesium, are all present in minute concentrations (2). If a metallic nanoparticle were to penetrate a cell membrane, the concentration of that given metal would increase substantially, causing toxicity to the cell (2). This could lead to either impairment of proper cell function and even induction of cell death or apoptosis (2). Though there is not much evidence to describe nanoparticle distribution among cells once they have penetrated a living tissue, they have been linked to multiple diseases (Figure 4) (2, 11). In the case of humans, there are a variety of routes by which nanoparticles could enter the body. Their potential for different methods of bodily entry complicates nanoparticle risk assessment, making the articulation of regulations for their production, consumption and disposal more challenging (8). The main route through which nanoparticles enter the body is also the most dangerous: by inhalation. Inhalation of nanoparticles allows these tiny substances to reach crucial areas of the human body, such as the olfactory bulb of the forebrain, lungs, kidneys, heart, and other vital organs through the bloodstream (11). Ingestion and dermal exposure are other common entry routes (2).
Figure 4 - A look at different types of nanoparticles and their proven carcinogenicity (2).
[4] The Positive Impacts of Nanoparticles on the Environment
Despite the potential damage that nanoparticles may cause, there are also several benefits of nanoparticles with respect to the environment and human use. They can certainly be perceived in a positive light, as they can be used for many therapeutic purposes, including drug delivery, and can also leave favorable influence if released into the environment in certain cases. For instance, certain nanoparticles have been used to clean up oil spills and convert harmful pollutants, found in the air and water, into harmless molecules (12). For nee, nanoparticles can serve to rid water of trichloroethene, a harmful pollutant found in wastewater (12). Manganese oxide nanofibers rid of volatile organic compounds found within the atmosphere, being a result of smoke produced from factories (12). In other cases, potassium manganese oxide nanowires can be used to clean up oil spills and even recover oil in such spills (12). While all of this is true, nanofabrication-based pollution control has its own obstacles to overcome before it can become entirely mass-commercialized. Some major obstacles include the high cost of implementing these remediation techniques and the difficulty of obtaining the nanoparticles required for pollution control into a workable form (12).
Conclusion
The lack of public awareness on the mere existence of nanoparticles combined with the amount of unavailable information on their potential environmental impacts should be of great concern to the environmentalists and the government. Aside from the matter of nanoparticle-related information being absent for the public, are the immediate issues that this leaves. For instance, the neglect toward nanoparticle research could infer that crucial filtration systems and regulations on nanoparticle usage and disposal are not being initiated or properly implemented and followed. As a result, nanoparticle pollution can accumulate within the environment, which will more than likely be dangerous to the ecosystems and biological organisms exposed in years to come (10). This is especially considerable as nanoparticles can be found and released from a multitude of sources. Tracking the sources, migration patterns, and chemical behaviors of nanoparticles, all the while considering their composition, creates a complex situation for environmental toxicologists to assess. While the main reasons that account for the lack of information on the effects of nanoparticles on the environment stand to be quite understandable, health, safety and the environment are top priorities that should not be ignored.
With regards to both the pros and the cons associated with nanoparticles, many are led to believe that the synthesis and production of nanoparticles should not come to a halt, at the expense of their environmental and health impacts, since their effects are still not well understood. Between being manufactured into everyday consumer products, to their applications in the medical field, and their use in bioremediation, nanoparticles have proven to be of much use in ways that would make it inconvenient to discontinue their production. While this stands true, there is reason to deduce that further nanoparticle research is imperative to assess their effects on both animal health and for the environment. Much like the negative health revelations that came with years of research done on smoking cigarettes, whose effects remained unknown for a substantial period of time, there is reason to entrust that the potential long-term effects of nanoparticles should be better looked into. Further, public awareness could be made possible with the release of nanoparticle information and warning labels on consumer products.
In the meantime, many hope that organizations, such as the National Nanotechnology Initiative (NNI), continue to research the possible health and environmental impacts of nanoparticles as well as improve their nanoparticle-environment assessment methodologies. Given the results they are likely to obtain, it is plausible that new upcoming research will serve to implement stringent and well-defined laws that would regulate nanoparticle synthesis methods, handling procedures and disposal techniques for the overall betterment of the environment and health of living organisms.
--------------------------------------------------------------------------------------------------------
References
1. What’s so special about the Nanoscale? National Nanotechnology Initiative. Retrieved from http://www.nano.gov/nanotech-101/special. [Accessed August 15, 2016]
2. Buzea, C., Pacheco, I.I., and Robbie, K. (2007) Nanomaterials and nanoparticles: Sources and toxicity. Biointerphases, 2(4):MR17. DOI:10.1116/1.2815690.
3. CDC: Americans Carry Body burden of toxic Sunscreen chemical. The Environmental Working Group. Retrieved from http://www.ewg.org/news/testimony-official-correspondence/cdc-americans-carry-body-burden-toxic-sunscreen-chemical. Published March 25, 2008. [Accessed August 10, 2016]
4. Brigger, I., Dubernet, C., and Couvreur, P. (2012) Nanoparticles in Cancer Therapy and Diagnosis. Advanced Drug Delivery Reviews, 64:24–36. DOI:10.1016/j.addr.2012.09.006. Retrieved from http://www.sciencedirect.com/science/article/pii/S0169409X12002669. [Accessed October 15, 2016]
5. Evaluation of Scratch Resistance Test Methods for Organic Coatings. Paint and Coatings Industry. Published March 1, 2004. Retrieved from http://www.pcimag.com/articles/84395-evaluation-of-scratch-resistance-test-methods-for-organic-coatings. [Accessed August 10, 2016]
6. History of Nanotechnology. Foresight Institute. Retrieved from http://www.foresight.org/nano/history.html. [Accessed August 10, 2016]
7. Piccinno, F., Gottschalk, F., Seeger, S., and Nowack, B. (2012) Industrial Production Quantities and Uses of Ten Engineered Nanomaterials in Europe and the World. Journal of Nanoparticle Research, 14(9). DOI:10.1007/s11051-012-1109-9.
8. The Environmental Risks of Nanoparticles. NANOCAP. Retrieved from http://www.nanocap.eu/Flex/Site/Pagefdba.html?PageID=20815. [Accessed August 10, 2016]
9. Nowack, B. and Bucheli, T.D. (2007) Occurrence, Behavior and Effects of Nanoparticles in the Environment. Environmental Pollution, 150(1):5–22. DOI:10.1016/j.envpol.2007.06.006. Retrieved from http://www.sciencedirect.com/science/article/pii/S0269749107002734. [Accessed August 15, 2016]
10. Borm, P.J., Robbins, D., Haubold, S., et al. (2006) The Potential Risks of Nanomaterials: a Review Carried Out for ECETOC. Particle and Fibre Toxicology, 3(1):11. DOI:10.1186/1743-8977-3-11.
11.Maila P. (2006) The Appropriateness of Existing Methodologies to Assess the Potential Risks Associated with Engineered and Adventitious Products of Nanotechnologies, European Commission - Health and Consumer Protection Directorate-General. Retrieved from: http://ec.europa.eu/health/ph_risk/committees/04_scenihr/docs/scenihr_o_003b.pdf. [Accessed August 15, 2016]
12. Zhao J. Turning to Nanotechnology for Pollution Control: Applications of Nanoparticles. Dartmouth Undergraduate Journal of Science. Retrieved from http://dujs.dartmouth.edu/2009/02/turning-to-nanotechnology-for-pollution-control-applications-of-nanoparticles/#.WAKHAFKYXzI. [Accessed September 5, 2016]
13. Sutcliffe H. Nano in cosmetics and personal care. Nano&Me: Nanotechnology in our lives. Retrieved from http://www.nanoandme.org/nano-products/cosmetics-and-sunscreen/. [Accessed October 10, 2016]
14. Adams P. China Reports the First Human Nano-Fatalities. Popular Science. Retrieved from http://www.popsci.com/environment/article/2009-08/china-reports-first-human-nano-fatalities. [Accessed October 10, 2016]
