Nanomaterial Risk AssessmentNov 11th, 2012 | By Katarzyna Branny | Category: Health and Safety
The process for conducting a nanomaterial risk assessment was published by the European Agency for Safety and Health at Work (EU OSHA) on September 12, 2012. The draft Practical Guidance, Working Safely with Engineered Nanomaterials and Nanoproducts, applies to companies that use or manufacture nanomaterials and companies that handle products containing nanomaterials.
As stated in the Practical Guidance, the methodology for conducting a nanomaterial risk assessment cannot be used in place of risk assessment and management practices required for conventional (non-nano) substances.
The Practical Guidance recommends that a MNM (manufactured nanomaterials) risk assessment be undertaken in ten steps as described below.
1. Inventory MNMs
As a first step, the employer is encouraged to identify all materials that could contain MNMs that are used, manufactured, or supplied in the workplace. If the employer cannot obtain information from a supplier regarding MNMs, it should assume that MNMs are present in the material.
2. Characterize MNMs
In this phase, the Practical Guidance suggests compiling detailed information about every nanoproduct to better understand the occupational health risks from exposure. Table 1 in the Guidance contains a list of the necessary criteria to record for each nanoproduct, such as:
- Name(s) of MNMs present in the material or nanoproduct;
- Whether any of the MNMs (or their material) have been classified as carcinogenic, mutagenic, or a substance toxic to reproduction (CMR substances);
- Density of the MNMs (in kg/dm3).
3. Identify Occupational Health Hazards
As a third step in the process of assessing MNM risks, the employer is encouraged to evaluate and rank the health hazards posed by each MNM. The Practical Guidance proposes four nominal hazard categories:
- Category 1 includes MNMs that are rigid, biopersistent nanofibers for which effects similar to those of asbestos cannot be excluded. Examples include SWCNT (single-wall carbon nanotube) or metal oxide fibers.
- Category 2a includes biopersistent granular nanomaterial (non-fibrous) with a density greater than 6,000 kg/m3. Examples include particles such as silver (Ag), gold (Au), and cerium oxide (CeO2).
- Category 2b includes biopersistent granular nanomaterials and nanofibers with a density less than 6,000 kg/m3 for which effects similar to those of asbestos can be excluded. Examples include particles such as titanium dioxide, calcium carbonate, carbon black, and polystyrene.
- Category 3 includes MNMs that are unlikely to exhibit any nano-specific effects because they are biodegradable and soluble. Examples include particles such as sodium chloride, flour, and sucrose.
4. Summarize Activities Involving MNMs
Step 4 requires the employer to identify all activities that may potentially involve the release of MNMs. The employer must assess the whole “life cycle” of the nanoproduct from the moment it enters the company to the moment it leaves.
5. Identify Possible Exposure to MNMs
The Guidance identifies three exposure categories:
I. Emission of primary MNMs (1 – 100 nm) is possible, for example, during handling of dry powders.
II. Emission of larger MNMs (>100 nm), for example, MNMs embedded in a solid or liquid matrix during weighing or adding MNMs, or through polishing, spraying, or sanding a nanoproduct.
III. Emission of MNMs (1 – 100 nm) minimized as far as technically possible due to the use of a fully closed system.
An exposure category (I-III) should be assigned to each activity identified in Step 4.
6. Select Appropriate Levels of Control
In selecting appropriate levels of control, the Practical Guidance follows internationally employed Control Banding. It distinguishes three different control levels and discusses how to select them:
- Control Level A (Risk level: High; Priority Control Measures: Highest) — the Practical Guidance recommends strict application of the occupational hygienic strategy. It also advises to implement all protective measures that are both technically and organizationally feasible.
- Control Level B (Risk level: Uncertain; Priority Control Measures: Medium) — the technical and organizational control measures can be assessed based on their economic feasibility.
- Control Level C (Risk level: Low; Priority Control Measures: Lowest) — the Practical Guidance advises employing the control measures that are normally used to control the exposure risks at the workplace, that is, measures used for non-nano bulk and other conventional materials.
7. Measure and Evaluate Exposure
For activities conducted at Control Levels A and B (step 6), the employer is encouraged to measure the actual concentration of MNM in the breathing zone of exposed workers. There is manual equipment available that allows simultaneous measurement of the particles’ concentration and the diameter of the particles. The concentration levels can be compared to the occupational exposure limits or derived no-effect levels that have been adopted by industries or research institutes. The Practical Guidance provides a table with the proposed occupational exposure limits specifically designed for MNMs. For example, for MWCNT (Multi-Wall Carbon Nanotube) Baytubes, the 8-hour TWA (time weighted average) exposure limit is 50 μg/m3, while for MWCNT (Nanocyl), the exposure limit is 2.5 μg/m3.
8. Implement Control Measures
As Step 8, the Practical Guidance recommends development of an action plan that includes all control measures that should be introduced to ensure a safe working environment. The plan should be reviewed with workers or their representatives and occupational, health, and safety experts.
9-10. Exposure Register and Medical Surveillance
Finally, the Guidance recommends that due to the current level of uncertainty with respect to the occupational hazards posed by MNMs, the employer should keep a record of all workers that might be exposed to MNMs. Employers may also consider subjecting exposed workers to medical observation.
The draft Practical Guidance is available online in English.
About the Author
Katarzyna Branny works at Enhesa Inc. where she is a regulatory consultant for Poland and the European Union. Ms. Branny monitors regulatory developments and develops audit protocols for these areas. She holds a Master’s degree from the George Washington Law School, as well as a Law Degree from the Jagiellonian University in Krakow, Poland. She is also a member of Polish and Washington D.C. bars.
Photograph: Light Explosion by David Ritter, Phoenix, Arizona, U.S.A.