In December, the World Health Organisation (WHO) published guidelines on protecting workers from potential risks of manufactured nanomaterials (MNMs)[i]. The focus of the guidelines is on low- and middle-income countries where nanotechnology is an important means of economic progress. The guidelines are intended to help policy-makers and professionals in the field of occupational health and safety in making decisions about the best protection against potential risks specific to MNMs in workplaces. The guidelines are also intended to support workers and employers. However, they are not intended as a handbook or manual for safe handling of MNMs in the workplace because this would require addressing more general occupational hygiene issues beyond the scope of the guidelines.
Challenges identified in characterizing risks of nanomaterials include:
- Materials with the same chemical composition may have different physiochemical properties due to their different sizes and shapes
- MNMs are being used in a rapidly growing number of products and industries
- The number of workers exposed is not known, but it is increasing
- Lack of information on human exposure pathways, the fate of MNMs in the human body and their ability to induce unwanted biological effects
- Only a small number of controlled studies have assessed the rate and health effects of MNMs in humans
- Data from cell and animal studies are available for only a few MNMs.
So far, no long-term adverse health effects in humans have been observed. This could be due to the recent introduction of MNMs, the precautionary approach to avoid exposure and ethical concerns about conducting studies on humans. This means that, except for a few materials where human studies are available, health recommendations must be based on extrapolation of the evidence from in vitro, animal or other studies from fields that involve exposure to nanoscale particles, such as air pollution, to the possible effects in humans.
The following key issues were addressed in the guidelines:
- Risks of MNMs
- Specific hazard classes
- Forms and routes of exposure
- Typical exposure situations
- Exposure measurement and assessment
- Occupational exposure limit (OEL) values
- Control banding
- Specific risk mitigation techniques
- Training for workers to prevent risks from exposure
- Health surveillance to detect and prevent risks from exposure
- Involvement of workers and their representatives
Systematic reviews were conducted into each of these areas, except for number 11, for which no studies were found. A precautionary approach was taken when devising the guidelines, meaning that exposure has to be reduced despite uncertainty about the adverse health effects. The guidelines also used the principle of the hierarchy of controls, meaning that, for example, elimination of exposure altogether is better than the use of personal protective equipment.
The Guidelines consist of 11 recommendations and two additional conclusions covering hazard and exposure assessment and risk mitigation measures for nanomaterials in the workplace. The recommendations are:
- Assign hazard classes to all MNMs
- Update safety data sheets with MNM-specific hazard information, or indicate lack of evidence for toxicology
- For respirable fibres and granular biopersistent particles, use the available classification of MNMs for provisional classifications of MNMs of the same group
- Assess workers’ exposure in workplaces with methods similar to those used for the proposed specific occupational exposure limit (OEL) value of the MNM
- Because there are no specific regulatory OEL values for MNMs in workpalces, assess whether the workplace exposure exceeds a proposed OEL. A list of proposed OEL values is provided in the guidelines.
- If specific OELs for MNMs are not available in workplaces, use a stepwise approach for inhalation exposure. Assess the potential for exposure, conduct basic exposure assessment and conduct comprehensive exposure assessment.
- Based on the precautionary approach, focus control of exposure on preventing inhalation exposure by reducing exposure as much as possible.
[i] WHO Guidelines on protecting workers from potential risks of manufactured nanomaterials. World Health Organisation. Published 12 December 2017 https://blogs.cdc.gov/niosh-science-blog/2017/12/15/who-nano/ (Accessed 27 December 2017)