Nanomaterials and the environment: The views of the Royal Commission on Environmental Pollution (UK)
With the advent of new technologies, novel substances inevitably escape into the environment, where they may give rise to unexpected effects. The Royal Commission on Environmental Pollution (RCEP) is an independent UK body, established in 1970 to advise Parliament and the British Government on actual and potential environmental threats. In 2006, the Commission began to gather evidence about the potential damage to the environment and human health that novel materials might cause. It soon became apparent that the vast majority of the evidence focused on nanotechnologies and nanomaterials. Consequently, the report, which was published in November 2008, centered primarily on these substances (http://www.rcep.org.uk/). Novel materials and new applications for existing materials are continually being developed. They are intended to improve the performance of existing technologies, such as fuel additives for enhanced energy performance of vehicles, or to allow the construction of new devices, such as MP3 players and mobile telephones. Other drivers include the need to find substitutes for raw materials that are in short supply or that have adverse effects on the environment or human health. In some cases, the discovery of novel functionality may stimulate a search for profitable applications. The novel materials sector and the nanomaterials sector in particular are not monolithic research-innovation- manufacturing sectors. They are highly complex webs of interaction involving many key players. The nanomaterials market is growing rapidly. The Woodrow Wilson Center's database lists over 600 products self-identified as containing nanomaterials currently available in the global marketplace (http://www.nanotechproject.org/inventories/consumer/).
The improved efficiency and functionality of nanomaterials can bring tangible environmental benefits, such as those offered by the development of photovoltaic devices, fuel cells, and lightweight composites for cars and aircraft. The properties of nanomaterials arise from two key attributes: the chemical composition of the material and its physical size and shape. As scientists exert ever more sophisticated control over molecular-level organization, the morphology of materials is becoming increasingly important. For example, in its natural bulk form, gold is famously inert. However, as a nanoparticle of 2- to 5-nm diameter, gold becomes highly reactive. The chemical composition of these two materials is identical; it is the different physical size of bulk materials and the nanoscale form that accounts for their very different properties.
No single classification has yet been devised for nanomaterials. Each approach to classification emphasizes the different characteristics of the materials in question and their applications. In practice, however, the functionality of the material and what it is capable of doing appears to be the most valuable focus for evaluating its potential environmental and human health implications. This emphasis on functionality, not on how a material is produced, or on physical size alone, is key to understanding the threats and opportunities offered by nanomaterials.
The small size of nanomaterials endows them with specific or enhanced physicochemical properties, compared with the same materials at the macroscale, offering potential for development for different uses and products 1. A working definition of a nanomaterial is one that is between 1 and 100 nm in at least one dimension. Nanomaterials can have one, two, or three dimensions in the nanoscale. One dimensional nanomaterials include layers, multilayers, thin films, platelets, and surface coatings. They have been used for decades, particularly in the electronics industry. Materials that are nanoscale in two dimensions include nanowires, nanofibers made from a variety of elements other than carbon, nanotubes, and a subset of this group, carbon nanotubes. Materials that are nanoscale in three dimensions are known as nanoparticles. They exist naturally (for example, natural ammonium sulfate particles), but they can also be manufactured, for example metal oxides such as titanium dioxide and zinc oxide. Metal oxide nanoparticles already have applications in cosmetics, textiles, and paints and, in the longer term, could potentially be used for targeted drug delivery. Buckminster fullerenes (also known as fullerenes and Buckyballs) are a class of nanomaterial of which carbon-60 (C60) is perhaps the best known. Potential applications include use as lubricants and electrical conductors.
As already emphasized, the properties and functions of nanomaterials can be very different from those of the bulk form. Furthermore, some of the properties discovered have not previously been observed in conventional chemistry or materials science 2. While the resulting difference in behavior from the bulk form makes it possible to use nanomaterials in novel ways, it may also give rise to different mobility and toxicity in organisms and the environment. The features of nanoparticles underlying these properties and behavior include greatly increased surface area per unit mass, changes in surface reactivity and charge, and modified electronic characteristics. The electronic features can become quantized, leading to so-called quantum effects that can influence optical, electrical, magnetic, and catalytic behavior (Andrew Maynard, Woodrow Wilson Center, Washington, DC). The strong surface forces exhibited at this size range are also important as they can play a significant role in self-assembly of nanostructures. It follows that some novel properties of nanoparticles are predictable, but others will be unexpected. These effects may be understood in terms of their causal relationship to the functionalities for which the new properties are being exploited. However, they are usually much less well characterized in terms of fate and behavior in organisms and the environment, or not characterized at all. While the basic principles used in describing substances for health and environmental effects are the same whether or not they are in the nanoform, certain properties are particularly or uniquely important in the case of nanomaterials. These include particle size, particle shape, surface properties, solubility, agglomeration, and aggregation. The way these properties determine behavior can be profoundly influenced by extrinsic variables, such as temperature, pH, ionic strength of containing medium, and the presence or absence of light.
Should we be concerned?
The Commission found no evidence of actual harm caused by nanomaterials to people or to the environment in the material it received, but the question arose: “How would we know if harm was being caused?” We were repeatedly told by competent organizations and individuals that insufficient information was available to form a definitive judgment about the safety of many types of nanomaterials. In some cases, the methods and data needed to understand the toxicology and exposure routes are insufficiently standardized or even absent. More worrisome, there is no consensus among scientists about how to address this deficit. Current toxicological protocols for evaluating chemical substances are fairly coarse screening methods that tend to pick up acute effects. Almost by definition, with novel materials and particularly nanomaterials, few data on chronic, long-term effects on people, other organisms, or the wider environment exist.
New toxicological and ecotoxicological testing protocols are required, and experts indicate that, using current approaches, it will take up to 15 years for a new testing protocol to achieve regulatory acceptance. Given the rapid pace of market penetration of nanomaterials and the products that contain them, existing regulatory approaches cannot be relied upon to even detect, let alone manage, environmental and human health threats before a material becomes ubiquitous. Difficulties also arise because the form of materials going into the environment might not be the same as that encountered during manufacture. Many free nanoparticles agglomerate and aggregate in the natural environment, forming larger structures that may have different toxicological properties than those of the original nanoform. Most nanomaterials are incorporated into products whose specific behavior and properties are often well understood, but very little thought has been given to environmental effects as nanomaterials become detached from products in use or at the point of final disposal. Techniques for routine monitoring of nanomaterials in the environment are not available, nor is it currently possible to determine their persistence or their transformation into other forms in real-world settings. Laboratory assessments of toxicity suggest that some nanomaterials could give rise to biological damage. To date, however, adverse effects on populations or communities of organisms in situ have not been investigated and potential effects on ecosystem structure and processes have not been addressed. Ignorance of these matters brings into question the level of confidence that can be placed in current regulatory arrangements.
As nanomaterials become incorporated into an increasing number of consumer and industrial products, the routes by which they might enter organisms and the environment rapidly increases (http://www.epa.gov/OSA/pdfs/EPA_nanotechnology_ white_paper_external_review_draft_12-02-2005.pdf). They may be discharged directly into rivers or the atmosphere by industry, or inadvertently escape when products are used or disposed of, for example, paints, cosmetics, sunscreens, and pharmaceuticals. In the absence of evidence of harmful impacts or of the safety of manufactured nanomaterials entering ecosystems, we can only examine the plausibility of damage based on the extrapolation of evidence from laboratory investigations and occupational exposure studies on dust and other related substances. A conventional toxicological approach involves identifying the characteristics of each manufactured nanomaterial, determining its bioavailability and persistence in realistic settings, and using data derived from measured or estimated concentrations in the environment as well as toxicological research in the laboratory to assess potential hazards and risks. Although there is a widespread consensus that comprehensive characterization of nanomaterials during manufacture, use, and disposal is required to understand their potential fate and effects on human health and the environment 3, this information is lacking in the vast majority of cases.
Effects in the environment and on human health
Free manufactured nanoparticles and nanotubes (e.g., powders) are likely to present the most immediate toxicological hazard to living organisms as they can easily interact with organisms in the wider environment 4. Fixed nanomaterials (those incorporated into solid matrices or attached to surfaces) do not present us with as much cause for concern, although potentially they may become detached and enter ecosystems, especially when products containing them abrade or weather or when they are disposed of as waste or are recycled 5. Evidence on the environmental and human health risks posed by nanomaterials has often been contradictory. Some environmental scientists and policy makers feel strongly that the threat posed is small, whereas others are worried about the possible toxicity of some nanomaterials, both to the wider environment and to human health. Concern was expressed about an increased risk of lung and cardiovascular damage from carbon nanotubes and C60 in humans, and the effects of nanosilver particles on microbial communities and sediment-feeding organisms. There is agreement that mechanisms of toxicity are poorly understood and that, with minor exceptions 5, appropriate ecological studies have not been undertaken, in particular, studies that address food web transfer and multigenerational effects. Currently, lack of knowledge about so many aspects of their fate and toxicology makes it extremely difficult to evaluate the safety of some nanomaterials. From an extensive review of the original published literature, several important conclusions can be drawn: (1) There is little consensus over the critical or even most important characteristics of manufactured nanomaterials that determine their toxicity profiles; (2) little information is available on how the various physical and chemical properties interact to generate an overall toxicity profile for a particular nanoscale material; (3) not much effort has been made to use standard particles to study individual characteristics and their interactions, nor concerted attempts to develop approaches similar to quantitative structure–activity relationships (QSARs) that are currently being used for conventional chemical forms; and (4) knowledge of the medical applications of nanomaterials to organ, cellular, and sub-cellular localization has not been effectively harnessed to aid the development of a predictive toxicology.
Very few research centers are involved in nanotoxicology, and they often use different materials and experimental protocols. Standardization and coordination of efforts is needed to produce reliable, useful data. Efforts are being made to address these problems by the Organization for Economic Co-operation and Development (OECD). There is also remarkably little linkage between knowledge gained from ecotoxicology and that gained from the study of toxicity in mammals including humans. Toxicology as a discipline has declined over the last 20 years in the UK, Europe, and the U.S., with reduced training and career development dedicated to this subject. Experts agree that lead times of several decades could easily be involved in training sufficient numbers of toxicologists and ecotoxicologists to meet future challenges associated with novel materials. As a consequence, significant toxicological uncertainties and areas of ignorance will remain.
The policy challenge
The policy challenge posed by novel materials is a specific instance of the more general dilemma of deciding how to govern the emergence of new technologies where knowledge and understanding of potential risks are uncertain. This is characterized as a trans-scientific problem 6. Scientists and regulators, as well as the wider public, invariably use world views to interpret data or other kinds of evidence. But where information is missing or evidence is ambiguous, people draw even more heavily on world views to inform their decision making. Different organizations and individuals interpret the same information, or lack of it, in very different ways, reflecting their broader interests and outlooks. Of those presenting evidence to RCEP, some expressed the optimistic view that no regulatory attention to novel materials could be justified unless and until there were clear indications that harm is being caused. Unjustified regulatory intervention might stifle innovation. A less optimistic view was that any attempts to devise governance arrangements for novel materials should be risk-based and that technology should be controlled only if scientific reasons for concern had been articulated. The cost of risk reduction should be proportionate to the probability and degree of danger. At the other extreme, some were opposed to using novel materials until their safety had been demonstrated beyond any reasonable doubt.
History is replete with examples where assumptions of the safety of particular chemicals were shown to be flawed too late to avoid serious consequences. The assumption that scientific methods allow us to detect problems at an early enough stage to prevent widespread damage is not borne out by experience. However, adoption of the ultra-cautious approach would deny citizens and consumers the real lifestyle and health benefits that technologies based on novel materials might provide. Increasingly, it will be impossible to determine the environmental and human health impacts of nano- and many other new materials in a consistent and timely manner using current risk-based regulatory frameworks. Also, in a technologically interdependent world, individual states cannot monitor and enforce rules governing the incorporation of materials in a wide range of products or of their disposal. This is an example of a technology control dilemma 7. In the early stages of a technology, not enough is known to establish the most appropriate controls for managing it. But by the time problems emerge, the technology is too entrenched to be changed without major disruptions. The solution to this dilemma is being vigilant to the development of inflexible technologies that are harder to abandon or modify. Key questions are, “How reversible is the commitment to the technology and how difficult would remediation be if problems arose?” Nanotechnologies, like other emerging technologies, require an adaptive governance regimen capable of monitoring materials and applications as they are developed. While a blanket moratorium does not seem appropriate, in specific cases it may be necessary to slow or even halt the development while concerns are investigated.
Regulations governing nanomaterials
The uncertainty and ignorance that characterize our understanding of the impacts of nanomaterials mean that traditional top-down regulatory mechanisms on their own may not provide protection without adversely affecting innovation. The UK and Europe do not have specific regulations for nanotechnologies or nanomaterials. Instead, the manufacture, use, and disposal of nanomaterials are covered, at least in principle, by a complex set of existing regulatory regimens. These include REACH, which is concerned with the Registration, Evaluation, Authorisation, and Restriction of Chemical substances 8 and product- or sector-specific regulations for pharmaceuticals, veterinary medicines, pesticides, and biocides. Specific regimens deal with toys, cosmetics, and end-of-life practices, such as the Waste Electrical and Electronic Equipment Directive 9. The purpose of REACH is to impose a responsibility on those who manufacture and sell the products to identify and understand potential threats to human health and the environment, and to minimize or eliminate the risk of adverse effects. It operates on the premise of “no data, no market.” At least in principle, it appears that, with some adjustment, REACH is capable of meeting the criteria for effective governance of nanomaterials. It provides a framework for the continuing review of authorizations, and even for the revision of key elements of the regulation itself. But a potentially major weakness is that regulatory instruments such as REACH have not been specifically designed with nanomaterial products and their applications in mind. The European Commission for the Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) has requested a review of REACH to identify possible modifications to deal with nanomaterials.
Another problem is that some nanomaterials may simply escape attention. Under REACH, nanoscale versions of existing substances (e.g., titanium dioxide) are treated in the same way as the equivalent bulk material, even if they have very different properties. The most significant potential limitation of REACH in relation to nanomaterials is the one-ton threshold for registration. Because of the very large number of particles present even in tiny quantities of a nanomaterial, one ton may be too high a threshold to capture potentially problematic effects. Several regulatory gap analyses have concluded that the existing framework is capable of adaptation to deal with nanomaterials, provided that the adaptation is underpinned by research to assess impacts and inform the setting of standards (www.hse.gov.uk/horizons/nanotech/regulatoryreview.pdf).
Of the additional measures considered for managing nanomaterials, RCEP was most attracted by the development of some kind of early warning system, one that might be managed by the competent authorities for REACH. An early warning system incorporating reporting requirements is a vital component of the governance of nanomaterials. We recommend that such reporting be kept as simple as possible. A straightforward checklist aimed primarily at nanomaterials not currently captured by REACH might suffice. All importers or manufacturers of such materials, or of products containing them (above some still-to-be-decided threshold for the quantities involved) that are not captured by REACH, would be required to complete the checklist in as much detail as they are able with current knowledge. It should be designed so as not to be onerous, should elaborate the special properties of the nanomaterials including the reason for being produced or incorporated in the product, and should also consider the pathways of environmental and human exposure throughout the entire life cycle of the product—not just at the point of use. Experience suggests that checklist reporting will have to be compulsory if it is to be effective.
Whatever additional measures are used, a robust program of environmental monitoring is required, using new techniques to detect manufactured nanoparticles in living organisms and the environment. Monitoring is an essential component of any early warning system. While blanket monitoring of the environment is not practicable, targeted monitoring for particular nanomaterials such as nanoscale silver is highly desirable. Obvious points for surveillance might include sewage outfalls, river water, and sediments downstream from major conurbations, coastal marine sediments, and sediment-feeding organisms. Detection of significant quantities of a nanomaterial in a top predator (such as pike or otter) also could be cause for concern. We envisage that knowledge about nanomaterials, their behavior in organisms and the environment, and their potential risks will accumulate, and that over time REACH and the sector-specific regulations will be adjusted. In the meantime, vigilance is clearly needed. That is why we propose the development of an early warning system as a supplementary measure to ensure that significant and irreversible harm will not occur.
Finally, we return to the control dilemma; we have argued that this dilemma confronts us in the case of nanomaterials, and that our response should be to strive toward an open and adaptive system of governance grounded in reflective and informed technical and social intelligence. Such a regimen, while encouraging appropriate innovation, would seek to avoid technological inflexibility, would be vigilant, and would be capable of intervening selectively but decisively when developments pose a potential threat to humans or to the non-human environment. We have argued that a system of adaptive governance for novel materials would in part be served by modifying and extending the existing regulatory framework as a matter of urgency, and by developing an early warning system, which must include robust arrangements for environmental monitoring. As in other fields characterized by ignorance, uncertainty, and ubiquity, however, regulation must be complemented and informed by the full range of perspectives on innovation, and by the undoubted benefits, as well as the potential risks, presented by new technologies.
Some of the recommendations in the RCEP's report are applicable to novel materials other than nanomaterials and indeed to the governance of wider categories of emergent technologies, particularly those involving issues of trans-science and the control dilemma. In summary, the RCEP recommendations on nanomaterials reflect three main priorities: functionality, focus on the properties of specific nanomaterials as the key driver; information, establish a directed research program on the properties and functionalities of nanomaterials to inform risk assessment and risk management strategies; adaptive management, recognize the degree of ignorance and uncertainty and the time it will take to address these. Flexible and resilient adaptive management is needed to handle such difficult situations and emerging technologies.
The research requirements highlighted in this editorial need to be undertaken on a more systematic and strategic basis than is possible at present under response mode funding, and the Commission welcomes moves by UK Research Councils to develop a directed research program in this area, following a successful pilot program, with emphasis on regulatory and policy needs. But over and above research needs, the RCEP study has highlighted the need for new ways of managing novel materials and other new technologies. We hope that our report will be a catalyst for further debate in this area and the emergence of new ideas to address these challenges.