A report by the UK's Health and Safety Executive has concluded that the safety of the tiny particles created by the emerging nanotechnology industry has not been fully assessed.
The HSE's study focused on the entire spectrum of nanotechnology, which in the pharmaceutical arena has been mostly associated with particles for improved drug delivery and as reagents for drug discovery research, such as quantum dots.
The safety of nanotechnology has been under scrutiny for some time. It first emerged in the 1980s when Eric Drexler, senior research fellow of the Molecular Engineering Research Institute in the US and a long-standing researcher in the area of nanoscale machines, published a book warning of self-replicating nanomachines that could go out of control - creating what has now become the infamous 'grey goo'.
Drexler has since revised his stance - now maintaining that self-replicating machines are unnecessary to advance the field - but other studies have since warned of different dangers, focusing on the impact of nanoparticles entering the body.
Last year, a study was reported showing that inhaled nano-sized particles accumulate in the nasal cavities, lungs and brains of rats, raising concerns that this build-up could lead to harmful inflammation and a risk of brain damage or other central nervous system disorders.
In its report, the HSE identified approximately 2,000 people in the UK currently working in universities, research centres and new nanotechnology companies who could potentially be exposed to nanoparticles in some form. This number is expected to double within five years, it adds.
But while 500 workers are considered to be potentially exposed to nanoparticles through existing ultrafine, manufacturing processes, mostly the manufacture of carbon black, around 100,000 individuals may be exposed to fine powders through various powder handling processes, including in the pharmaceutical industry.
The report notes that the four main nanoparticle production processes are gas-phase, vapour deposition, colloidal and attrition, all of which could result in exposure through inhalation, dermal or ingestion routes.
"From an occupational hygiene perspective, these processes are not too different to existing chemical production processes," according to the HSE.
Only gas-phase processes have the potential to cause exposure to primary nanoparticles by inhalation during the synthesis stage, it notes, but all the processes may give rise toexposure (by inhalation, dermal and ingestion) to agglomerated nanoparticles duringrecovery, powder handling and product processing.
For exposure by inhalation, protection methods already exist that should be effective against nanoparticles, but for dermal and ingestion exposure, current control methods based on personal protective equipment may not be as effective as they are for chemical production processes, said the HSE.
Worryingly, the HSE states that no information is available concerning workers' exposure to nanoparticles in the UK, but information from other powder handling processes suggests that exposures may be significant.
"In summary, we conclude that there is little evidence to suggest that the exposure of workers arising from the production of nanoparticles has been adequately assessed," it states.
Key knowledge gaps identified in the study include the absence of agreed definitions or descriptions for nanoparticles or nanoparticle aerosols, and these should define a size interval to take account of the distribution in sizes likely to be present, to consider whether the definition should be based on physical dimensions (e.g. length, diameter, surface area) or on some behavioural property such as diffusivity and take account of agglomerated aerosols.
Progress in this area will be best achieved by building consensus, and the HSE has organised a workshop this month to address these concerns.
Other outstanding issues include a lack of tools to measure nanoparticle exposure in the workplace, little information on adequate control measures and a lack of data for risk assessments.
A copy of the 111-page report can be downloaded from the HSE website .