In classical chemistry a substance exhibits consistent properties: nickel is always nickel, ferric oxide is always ferric oxide, and each of the forms of carbon always behaves consistently. However, when physics, and especially quantum mechanics, is introduced, substances may behave in quite different ways.
That is the issue facing nanotechnology. Environmentally the change in behavior may be beneficial or it may be deleterious. In many cases all that's known so far is that nanoparticles may behave in a different way compared to the conventional bulk substance.
What are they?
In common parlance, nanomaterials are substances with a particle dimension ranging from 1 to 100 nanometers. For comparison, a human hair has a diameter of about 60,000 nanometers. The extremely small particle size means that the substance may have different properties than those associated with the conventional substance. It may have a different physical strength, different solubility, or different chemical reactivity. Perhaps of greatest concern is that the particles may be so small that they can pass through the skin of humans and other living organisms and may be able to enter and disrupt the cells from which all living things are constructed. With different ways of producing nanomaterials, even those with the same chemistry -- but from different manufacturers -- may have different properties.
The reasons that nanomaterials have different properties from the larger particle size material include:
-- the relative surface area is large compared to the mass, potentially increasing the reactivity, and hence the toxicity, significantly; and
-- quantum effects apply to very small objects. These quantum effects can change optical, magnetic and electrical properties and may cause nanoparticles to agglomerate or adsorb to each other. For example, while a graphite pencil lead doesn't conduct electricity, a carbon nanotube that is one atom thick can act as a semi-conductor. For more than a decade nanomaterials have been presented as a marvel of technology. They are now used in coatings, plastics, cosmetics, toothpaste and many more consumer products. The Woodrow Wilson Institute has listed more than 1,015 consumer products in the US and around the world that contain nanomaterials, yet there is no widely accepted definition of a nanomaterial, no labeling requirements, little in the way of environmental and health impact assessment, and little government regulation. Consumer products containing nanomaterials on the Canadian market are as diverse as skin cleansers, water resistant clothing, antibacterial coating for hot tubs, and oral tablets that claim to help people lose weight faster.
In a report published in 2008, an Expert Panel of the Council of Canadian Academies concluded that there is not enough information available to assess the safety of nanomaterials. This is a highly qualified group; the members of the Council of Canadian Academies are: the Royal Society of Canada: The Academies of Arts, Humanities and Sciences of Canada; the Canadian Academy of Engineering; and the Canadian Academy of Health Sciences.
One challenge of nanomaterials is that conventional toxicity tests, which often require dissolving a substance in water, may not be applicable. If an inorganic nanomaterial is dissolved in water it's most likely no longer in the form of a nanomaterial (note that some nanomaterials -- including carbon "Bucky balls" -- may retain their molecular structure when dissolved) so testing the solution for toxicity is not a proxy for toxicity of the solid material. Toxicity tests for exposure through inhalation or dermal absorption are much more complex and hence much less commonly used, but may be the only appropriate type of tests for nanoparticles.
Risks
Some of the potential risks associated with nanomaterials include that nanomaterials may contain impurities or byproducts that could affect the toxicity. For example, carbon nanotubes have been found to contain iron, cobalt and molybdenum (used as a catalyst) as well as smaller amounts of chromium, copper and lead.
Some nanomaterials are toxic materials in their own right such as heavy metals and can enter cells such as the human lung. The design of experiments to test nanomaterials for toxicity may not be scientifically valid. For example, many toxicity tests require dissolving the material in water but nanoparticles are insoluble in water.
Nanoparticles are so small they may behave somewhat like a gas and may be carried high into the stratosphere or washed down into soil and water by a rainstorm. They may also enter the environment through wastewater discharges, such as industrial waste streams and effluent from wet scrubbers used for pollution control.
Nanoparticles are likely to remain suspended in the air for some time and hence could be inhaled. Aquatic species may be exposed through their gills. They may be toxic to environmental organisms. For example, earthworms may ingest nanoparticles from contaminated soils. Fullerenes (molecular carbon nanomaterials) have strong antibacterial action so spills and disposals can cause environmental impacts. Insoluble nanoparticles may settle into aquatic sediments and could pose a risk to sediment species.
Policy and technical challenges
In Canada most nanomaterials, those with a chemical structure identical to that of a conventional substance, are considered by Environment Canada to be the same as the conventional substance, even though this is known not to be the case; hence no notification is required under the New Substances Program of the Domestic Substances List. There are some exceptions where notification is required, for example if a proposed use requires a Significant New Activity Notice. Approvals are still required for nanomaterials used in such regulated products as pesticides or foods.
In the United States, cumulative government investment in research on the environment, health and safety implications of nanomaterials totals $350 million, mostly since 2005. A further funding request of $88 million to cover increased research on the type and amount of nanomaterials in biological systems, the environment and the workplace has been requested for 2010. Some of the research findings and initiatives include:
-- Coating nanoparticles with a layer of certain materials changes their toxicity.
-- Iron oxide nanocrystals can remove 98 to 99 per cent of arsenic from drinking water.
-- The US National Institute for Occupational Health and Safety (NIOSH) aims to control occupational exposure to fine and ultrafine titanium dioxide.
-- The FDA is developing new tools to detect and characterize nanomaterials in food, food additives, nutritional supplements, cosmetics, drugs, medical devices and biologicals in terms of toxicity, biocompatibility, and exposure.
United States' government research is also planned to: improve sampling and analysis for workplace and airborne exposures; develop recommendations and establish guidance for engineering controls, protective equipment and safe handling for controlling occupational exposure to carbon nanotubes; and, to address gaps in information on sampling, analysis, exposure assessment, instrumentation and controls, long term health effects, and explosive potential of nanomaterials. The US and Canada are also reported to be working with the OECD on an international level. EPA is testing 14 nanomaterials on 59 environmental end points.
In June of this year, the US-based Investor Environmental Health Network, which includes NGOs as well as investment management firms, compared the lack of disclosure about nanotechnology to what the group calls the "asbestos litigation disaster for investors." It calls on the securities commission to close eight major loopholes to improve disclosure. The loopholes identified by the IEHN include:
-- Shortsightedness: Regulations currently allow companies to take the short view and avoid disclosure and estimation of longer-term liabilities.
-- Concealed Science: Regulators currently allow companies to conceal emerging science that forewarns of potential liabilities in the future.
-- The Known Minimum: Regulations currently require accrual of only the "known minimum" of pending liabilities when greater likelihood of higher liabilities is uncertain.
-- Privileging Secrecy: Privileging concealment by using attorney-client relations as a shield against estimating liability for investors.
-- Inconsistent Estimates: Providing larger liability estimates to insurers than to investors.
-- Hidden Assumptions: Using hidden assumptions to minimize estimates of liability.
-- Missing Benchmarks: No requirement to benchmark liabilities against other companies whose experience with relevant claims demonstrates realistic estimates of liability.
-- Risk-Free Proxies: Refusing to allow shareholders to propose annual proxy ballot requests for corporate reports on specific risks of concern to investors.
More information about the environmental implications of nanotechnology can be found in a book sponsored by AMEC and published earlier this year:
Sellers, Kathleen, Christopher Mackay, Lynn L. Bergeson, Stephen R. Clough, Marilyn Hoyt, Julie Chen, Kim Henry, and Jane Hamblen, Boca Raton, Florida: CRC Press (Taylor and Francis Group), 2009. Price: US$99.95 ISBN: 9781420060195 CRC Press Online http://www.crcpress.com/ [and search for title. Price reduction to US$79.95]. HMM
Colin Isaacs is an environmental analyst, consultant, and writer with more than 25 years experience. He is editor of the Gallon Environment Letter and his commentaries also appear regularly in this magazine's affiliate information products, such as EcoLog news. Contact Colin at colin@cialgroup.com