In Australia, between 1987 and 2010, asbestos exposure is predicted to result in 16,000 deaths from mesothelioma and 40,000 deaths from lung cancer. The serious health risks posed by workplace exposure to nanomaterials share some striking similarities to those presented by asbestos. As with exposure to asbestos or other toxic dusts, workplace exposure to nanoparticles has the potential to cause serious pulmonary and related cardiovascular disease. However the most important similarity between asbestos and nanoparticle exposure may be the lag time before the potential onset of serious harm to health – resulting in significant human and financial cost.
Insurers Nanotechnology Safeguards
To safeguard against a repeat of the asbestos experience, the world’s second largest re-insurer, Swiss Re, has advocated a strict application of the precautionary principle in the regulation of nanotechnology. Swiss Re emphasizes that conservative regulation that puts health and safety first must be adopted, irrespective of uncertainties in scientific circles.
The Head of the Science Strategy and Statistics Division of the UK Health and Safety Executive has also recommended that rigorous regulation be developed to prevent nanoparticle exposure becoming the ‘new asbestos’. He noted that if regulators introduce “controls that are too lax, significant health effects [will] harm many people. The history of asbestos should warn all of society of the human and financial costs of this possibility”.
However despite the hundreds of products containing nanomaterials that are already being manufactured commercially, and the emerging body of scientific literature demonstrating the serious risks associated with nanotoxicity , there are still no laws to manage workplace exposure and to ensure workers’ safety. This suggests that governments have learnt little from their experiences with asbestos.
Why Are Nanomaterials Different From Larger Particles?
Nanomaterials are the result of engineering at the molecular level to create extremely small-scale materials with unique properties. One nanometre (nm) is one billionth of a metre (m). Nanomaterials are defined as those particles (metal oxides, carbon nanotubes, nanowires, quantum dots, fullerenes (buckyballs), nanocrystals etc) that exist at a scale of 100nm or less, or that have at least one dimension that affects their functional behaviour at this scale. To put 100 nanometres in context: a strand of DNA is 2.5nm wide, a protein molecule is 5nm, a virus particle 150nm, a red blood cell 7,000 nm and a human hair is 80,000 nm wide.
The fundamental properties of matter change at the nanoscale. The properties of atoms and molecules are not governed by the same physical laws as larger objects or even larger particles, but by “quantum mechanics”. The physical and chemical properties of nanoparticles can therefore be quite different from those of larger particles of the same substance. Altered properties can include colour, solubility, material strength, electrical conductivity, magnetic behaviour, mobility (within the environment and within the human body), chemical reactivity and biological activity.
The altered properties of nano-sized particles have created new possibilities for profitable products and applications. These altered properties also raise significant health and environmental risks that remain poorly studied, poorly understood and wholly unregulated.
Evidence Of Probable Harm Associated With Workplace Exposure To Nanomaterials
There is a general relationship between toxicity and particle size. The smaller a particle, the greater its surface area compared to its volume, the higher its chemical reactivity and biological activity, and the more likely it is to prove toxic. There is often no relationship between the toxicity of a nanoparticle and the toxicity of a larger particle of the same substance. This key principle is yet to be reflected in the regulatory system.
Because of their small size, nanoparticles are more readily inhaled and ingested than larger particles, and are more likely than larger particles to penetrate human skin . Once in the blood stream, nanoparticles may be transported around the body and are taken up by individual cells, tissues and organs. We know very little about how long nanoparticles may remain in the body and what sort of ‘dose’ produces a toxic effect.
Animal studies have routinely demonstrated an increase in lung inflammation, oxidative stress and negative impacts in other organs following exposure to implanted or inhaled engineered nanoparticles. Irespective of their chemical composition, engineered nanoparticles are also recognized to be potent inducers of inflammatory lung injury in humans.
Workplace exposure to nanoscale fibres (e.g. carbon nanotubes) is of obvious concern given the well-established association of fibres such as asbestos with serious pulmonary disease. A recent study exposed rodents to carbon nanotubes at levels that proportionately reflected the existing permissible exposure limit for carbon graphite particles (there are no set exposure limits for nanomaterials). This resulted in inflammation, reduced pulmonary function and the early onset of fibrosis. Carbon nanotubes were more toxic than comparable quantities (by weight) of ultra-fine carbon black or silica dust. The authors concluded that if workers were exposed to carbon nanotubes at the current permissible exposure limit for graphite particles, they would be at risk of developing lung lesions.
Once in the blood stream, nanomaterials are transported around the body and are taken up by organs and tissues including the brain, heart, liver, kidneys, spleen, bone marrow and nervous system. Nanoparticles are able to cross membranes and gain access to cells, tissues and organs that larger sized particles normally cannot. Unlike larger particles, nanoparticles may be transported within cells and be taken up by cell mitochondria and the cell nucleus, where they can induce major structural damage to mitochondria, cause DNA mutation and even result in cell death.
Nanoparticles have proved toxic to tissue and cell cultures in vitro. Nanoparticle exposure has resulted in increased oxidative stress, inflammatory cytokine production and even cell death. Even low levels of fullerene (buckyball) exposure have been shown to be toxic to human liver cells . Fullerenes have also been found to cause brain damage in fish, kill water fleas and have bactericidal properties.
We still don’t know whether nanoparticles are able to penetrate intact skin. We know that organic liquids, lipid-based pharmaceuticals and phthalate monoesters in personal care products may be taken up by the skin. However few studies have examined the ability of nanoparticles to penetrate the skin, and the variety of circumstances in which occupational skin exposure to nanomaterials is likely to take place has not yet been investigated. For example uptake of nanoparticles may be influenced by skin flexing, pressure, wet vs dry conditions, the presence of bacteria and exposure to other substances.
The ability of micro-scale particles (1000nm) to access the dermis when the skin was flexed has been demonstrated, suggesting that the uptake of particles <100nm is possible in at least some circumstances. Broken skin is known to enable the uptake of microparticles up to 7,000nm wide – 70 times the size of nanoparticles.
Key gaps in our understanding and other critical obstacles to providing worker protection from nanoparticle exposure
Workers may be exposed to nanoparticles during the research, development, manufacture, packaging, handling and transport of nanotech products. Exposure may also occur in cleaning and maintaining research, production and handling facilities. But despite the commercial availability of over 720 products containing nanomaterials , we don’t know how many companies are using nanomaterials, how many workers are exposed, the source or levels of their exposure, and how to manage or prevent this exposure to ensure workers’ safety.
Preventing Unsafe Workplace Exposure
Critical obstacles to preventing unsafe workplace exposure to nanomaterials include:
• No consistent nomenclature, terminology and measurement standards to characterise and describe nanoparticles and exposure
• Inadequate understanding of nanotoxicity, in particular to determine whether acceptable exposure limits exist
• No effective methods to measure and assess workplace exposure to nanoparticles; no data on existing or predicted workplace exposure
• No effective control methods to protect workers from exposure
Essentially, occupational health and safety experts know enough to recognise that nanoparticles are highly reactive, highly mobile, more likely than larger-sized particles to produce a toxic effect in workers, and likely to be ineffectively controlled by current workplace practice and likely to result in harm to those exposed on a regular basis. However they don’t know enough to predict the particular risks associated with particular workplace exposures, and nor do they know how to manage these risks to protect workers’ health. It is completely unknown what sort of levels of exposure can be considered safe.
To prevent nanotechnology becoming the ‘new asbestos’ The Friends of the Earth claim there is an urgent need for a moratorium on the commercial research, development, production and release of nanoproducts while regulations are developed to protect the health and safety of workers, the public and the environment.