Late last month, the U.K.’s Department for Environment, Food and Rural Affairs (DEFRA) published "Characterising the Potential Risks Posed by Engineered Nanoparticles: A Second U.K. Government Research Report." The report addresses potential nano-related EHS issues in the context of five DEFRA task-forces: (i) Metrology, Characterization, Standardization and Reference Materials; (ii) Exposures: Sources, Pathways and Technologies; (iii) Human Health Hazard and Risk Assessment; (iv) Environmental Hazard and Risk Assessment; and (v) Social and Economic Dimensions of Nanotechnologies.
Task Force 1 (Metrology, Characterization, Standardization and Reference Materials)
DEFRA acknowledges the importance of baseline research. The report emphasizes the need for dose quantification toxicology studies; quantification and characterization of the differences between engineered nanoscale materials and incidental nanoscale materials; surface area and chemistry characterization for nanoscale materials; and inexpensive and easy workplace monitoring methods. To this end, DEFRA proposes several characteristics of nanoscale materials that it recommends exploring on a material-by-material basis: (i) aerodynamic equivalent diameter; (ii) absolute length; (iii) specific surface area; (iv) number of particles per unit mass; (v) concentration of bulk and/or surface contaminants; and (vi) "polymorphic composition."
DEFRA also suggests establishing a reference bank of nanoparticles which are of prime EHS importance. Nanoscale materials would be selected using three criteria (i) production and likelihood of exposure; (ii) expected physio-chemical interaction with living systems; and (iii) the current existence of standardized comparative studies. Applying these criteria, DEFRA identifies seven priority materials for reference development: carbon black; TiO2; ZnO; single-walled and multi-walled carbon nanotubes; polystyrene; metal & metal oxide; combustion-derived nanoparticles. DEFRA has also identified eight (unnamed) lower priority materials for consideration.
This DEFRA task-force recommends additional research regarding the ignition and explosion propensities of different nanoscale materials and the development of new test methods including ways to measure and assess the of exposure of nanoparticles in soil and water.
This section concludes with a summary of the U.K.’s role in various standardization activities being conducted by the British Standards Institute (BSI NTI/1); European Committee for Standardization (CEN/TC 352); International Standards Organization (ISO/TC) 229; and International Electrotechnical Commission (IEC/TC 113).
Task Force 2 (Exposures: Sources, Pathways and Technologies)
This DEFRA task-force identifies its current research priorities as: (i) exploring the exposure differences between engineered and incidental nanoscale materials; (ii) determining the proper exposure metric(s) for future EHS research; (iii) developing new nano-specific life-cycle assessment methodology; (iv) generating nanoscale material exposure data and computer modeling techniques; and (v) developing nano-specific workplace engineering controls.
Also of importance is the NanoAlert help-desk funded by HSE which is essentially a EHS bulletin service. NanoAlert has already published two bulletins regarding nano-related EHS issues.
Regarding life-cycle analysis, DEFRA briefly explains the efforts underway at the University College of London and future practical case studies it might conduct using the example of carbon nanotubes in automobile tires.
This task-force also calls for the development of new technologies to measure ambient exposure and understanding of fate and behavior of nanoparticles in air. As an example, the task-force points to the DuPont led Nanoparticle Occupational Safety and Health (NOSH) Consortium which has developed methods for reproducible generation of different types of nanoparticle aerosols.
This section concludes by briefly touching upon (i) pilot exposure monitoring studies being conducted by NANOSH, (ii) HSL funded research (Nanochallenge) regarding exposure assessment and control; (iii) fire and explosion issues; (iv) the development of in vitro toxicology assays, and (v) the personal protective equipment and containment research being conducted by NANOSAFE 2. The section ends with a summary of nanotechnology EHS efforts by OECD; EU 7th Framework Programme; NIOSH; and U.S. EPA.
Task Force 3 (Human Health Hazard and Risk Assessment)
This DEFRA task-force identifies several issues needing urgent consideration: (i) developing standard reference nanoscale materials for testing purposes; (ii) determining the specific characteristics of nanomaterials that confer toxicity; (iii) conducting inhalation studies; and (iv) conducting dermal penetration studies. The task-force recognizes in vitro studies can be effectively used as a screening tool for hazard assessment, however, it believes in vivo data is needed "before definite conclusions could be drawn for hazard assessment." Interestingly, the task-force notes:
A number of recent reports have concluded that current methods used to assess the health effects of chemicals, based largely on experimental studies in animals, are generally appropriate for manufactured [engineered] nanomaterials.
The task-force also recommends giving special attention to methodology and dosimetry issues and recognizes the need for more targeted work on human toxicology.
Regarding nanotoxicology, the task-force finds two texts provide the best overview of the state of current science: (i) K. Donaldson, et al., Particle Toxicology, CRC, Taylor & Francis Group (2007); (ii) N.A. Monteiro-Riviere, et al., Nanotoxicology: characterization, dosage and health effects. Informa Healthcare (2007). Beyond these two texts, the task-force notes the need for a systematic appraisal of existing nanotoxicology literature to identify EHS research gaps in a coordinated way.
On another nanotoxicology issue, the task-force takes a position that is sure to be controversial to some NGOs:
The idea that nanoparticles have unique properties that set them apart from all other particles in terms of the nature and extent of their toxicity, now seems increasingly unlikely to be true: this represents a change in thinking over the past ten or so years. Work using surface area as the dose metric, for example, has allowed nanosized titanium dioxide particles to be placed on the same dose-response curve as regards pulmonary inflammation as larger titanium dioxide particles. . . . It seems to be thought, now, that the reactivity of the particle surface, expressed in units of reactivity per unit surface area, is unchanged by reducing particle size to nano-dimensions.
At the same time, the task-force believes current science accepts nanoparticles can (i) gain access to cell locations and tissues inaccessible to larger particles (including cell mitochondria and the central nervous system); (ii) enter lung interstitium easier that larger particles; (iii) enter the bloodstream where their ultimate fate is "imperfectly known. "
This task-force also explains the importance of nanofiber toxicity research. To this end, DEFRA is currently funding a project to determine whether and when aspect ratios of certain nanofibers should raise the similar concerns as asbestos fibers. Finally, this section of the report describes DEFRA funding of projects studying physio-chemical factors controlling nanoparticle penetration of respiratory epithelium, and recognizes the need to develop new in vitro testing and epidemiological studies.
Task Force 4 (Environmental Hazard and Risk Assessment)
Key priorities for this task-force are the U.K’s Environmental Nanoscience Initiative; development of characterization and other baseline nano-science issues; development of standard materials for benchmark ecotoxicological studies; creating new ecohazard case studies; and evaluating the appropriateness of current environmental hazard assessment methods. In this section, the task-force explains the U.K.’s Environmental Nanoscience Initiative which was launched in September 2006. The program initially considered 37 nano-related EHS research submissions and made 10 grants made in April 2007. A second round produced 23 submissions and an additional 8 grants. The task-force concludes this section noting the "critical need to develop nanomaterials characterisation and analysis infrastructural support," and the "need for guidance on an agreed suite of dose metrics for reporting in ecohazard studies." The report also briefly mentions ongoing ecohazard studies being conducted at University of Exeter; Napier University; University of York; and University of Birmingham.
Task Force 5 (Social and Economic Dimensions of Nanotechnologies)
This DEFRA task-force identified several nano-related societal research priorities to which the U.K. government is committed: (i) predicting social and economic impacts of nanotechnology commercialization; (ii) analyzing the sufficiency of existing regulatory mechanisms; (iii) identifying factors influencing public acceptance of nanotechnology; (iv) addressing resource consumption issues specific to nanotechnology; and (v) establishing methods for effective public engagement in nanotechnology dialogues. The the task-force notes two recent studies show the public in the U.K. currently has the same attitude towards nanotechnology as towards any other new technology. At the same time, the studies show developing public EHS concerns, as well as strong existing support for fundamental nano-science research and development. This section closes with a brief summary of five past government funded public dialogues on societal issues and identifies several existing U.K. and international nano-related societal impact projects underway.