Meeting the Health and Safety Challenges Posed by Nanoparticles and Nanomaterials

Nanochallenge is a three year programme of work funded by HSL and HSE. The program is divided into three main projects, where HSL has established (or is developing) expertise:

NanoChallenge Project I - E xposure Assessment and Control
NanoChallenge Project II - Toxicology Screening Tool and Modelling
NanoChallenge Project III - Fire and Explosion Properties

Project I - Exposure Assessment and Control

This project includes:

• Improved methods for generation of nanoparticle aerosols. This part of the work is to equip the laboratory with a comprehensive range of nanoaerosol generation techniques to enable the evaluation of:
  • the instruments used for assessing exposure to nanoparticles;
  • the performance of PPE and RPE, containment systems and other methods of exposure control.
• Efficient sampling and monitoring. This part of the work will develop methods for the collection of airborne engineered nanoparticles in workplaces and their characterization and discrimination against combustion by-products or ultrafines by transmission electron microscopy (TEM). It will also focus on the evaluation of where biological monitoring might be best applied and on contributions to exposure assessment and studies of the effectiveness of PPE.
• Safe handling and control. This part of the work will investigate whether the current HSL dustiness test is suitable for evaluating the dustiness behaviour of nanopowders and if not to propose and investigate alternative options for particle dispersal and measurement.

Back to the top

Project II - Toxicology Screening Tool and Modelling

This project will focus on:

• Developing and validating cost effective human in vitro toxicological assays for assessing the health effects of manufactured nanomaterials.
• Providing data on the transport, circulation and toxicity of nanomaterials to develop in silico models of human exposure (either PBPK or models of distribution that no not assume portioning or metabolism).

• NanoChallenge Project II aims to develop a novel human in vitro screen for potential toxicity of manufactured nanomaterials based upon freshly isolated human blood. Multiple endpoints will be investigated, including assessment of total cell death, immunological responses and cellular oxidative stress. Effects on the blood coagulation pathway (a critical risk factor for cardiovascular disease) will also be examined.

  The strength of this approach is that unanticipated toxic effects of these nanomaterials may arise from interactions between different types of cells, thereby mimicking what is likely to happen following human inhalation of a nanomaterial. This testing strategy will also provide valuable information about variability of the human response to these materials.

  A longer-term aim of this work is to provide data for computational toxicological models that can predict the effects on humans of exposure to nanomaterials and hence to derive effective in vitro analyses of the toxicity of nanoparticles for manufacturers and occupational health professionals. The combination of human in vitro and in silico models addresses the need to replace and reduce the use of animals in toxicity tests.

  Back to the top

Project III - Fire and Explosion Properties

This project will focus on:

• Developing a suitable test system to measure ignition and explosion characteristics of nanoparticles, using far smaller quantities than used by existing tests.

• Fine powders are known to be an explosion risk, particularly organic and metallic powders. The ignition energy of particulates reduces as size decreases, but tends to plateau at about 75mm. However, there is an indication that as particles approach molecular sizes, the ignition energy of particulates should approach that of a gas, which is too small to be measured using conventional dust-cloud apparatus.

  The explosion properties of micron-scale materials are well documented. However, a literature search has found no explosion data relating to nonomaterials. Additionally, it is considered that the extrapolation of the data for micron-scale particles to the nano-scale particles cannot be carried out with any degree of confidence, due to the marked change in chemical and physical properties of particles below sizes of about 100 nm.

  For fine particulates, there is standard test equipment available to determine the explosion and ignition characteristics for powders, but these typically require reasonably large quantities of powder. Much smaller test apparatus is required for nanomaterial testing. Also, the powder is dispersed in the standard apparatus using compressed air. With nanomaterials, their large surface to volume ratio means that many are spontaneously flammable on contact with air, or surface oxidation alters their properties. Hence equipment that avoids oxidation until the point of ignition is required. Currently, there is no commercial equipment available to satisfy this requirement.

  To meet this need, HSL are developing specialised equipment that will have the capability to measure both ignition energy and explosion characteristics. The intention is to prove the concept and make suitable pilot equipment.

  As part of this development, HSL are reviewing knowledge and technology that currently exists. This will reveal if the technology has been attempted before, and the outcome of previous failures or successes. The potential for developing apparatus, which can measure both ignition energy and explosion characteristics will be explored. The outcome will be the design of small-scale pilot equipment and the development of the techniques required for characterising the explosion properties of nanomaterials.

  To commission this new equipment, the explosion properties of materials with known properties will be measured. A comparison of the results from standard explosion test equipment is to be done to determine scalability of the newly developed equipment.