Worker Education and Training

Establishing a program that includes the education and training of workers on the potential hazards of CNT and CNF and their safe handling is critical to preventing adverse health effects from exposure.

Research has shown that training can attain imme-diate and long-term objectives when (1) workers are educated about the potential hazards of their job, (2) there are improvements in knowledge and work practices, (3) workers are provided the neces-sary skills to perform their job safely, and (4) there

Table 6–6. Examples of engineering controls Containment category

and description Advantages Disadvantages

A. Dilution ventilation and no engineering controls Supply and exhaust large volumes of air (typically > 10 air changes/hr.) throughout the work area to dilute airborne emissions.

For general facility HVAC needs. Not recommended for controlling worker exposure to CNT and CNF.

No local exhaust ventilation (LEV) or equipment enclosures required.

Disperses/dilutes airborne emissions throughout work area.

Does not control exposure at the source, spreads emissions throughout work area potentially exposing other workers.

Often requires large airflow exhausts to dilute contaminants to below OEL increasing operating costs.

Should only be considered when contaminant generation is reasonably uniform and toxicity of material is low.

B. Local exhaust Ventilation (LEV)

Hoods or enclosures on process equipment that exhaust air at the emission source to collection equipment and away from the worker’s breathing zone.

Includes:

B.1. Laboratory fume hoods (typically 80–120 ft/min face velocity) with HEPA filter

B.2. Biological safety cabinet Class II

B.3. LEV incorporated at source of exposure and can be built into hand-held tools

Capture emissions at their source with well-designed hoods.

Hoods can be tailored to the process or work task to optimize the capture of emissions.

Usually requires less overall exhaust airflow rates than dilution ventilation systems.

Air volumes and face velocity of LEV must be maintained to ensure the capture of emissions.

Workers must be trained in the correct use.

Fume hood sash opening needs to be adjusted to ensure proper hood face velocity.

System exhaust flow rate may need careful evaluation to ensure adequate capture while minimizing loss of product.

C. Down flow booths Small room or enclosure with low velocity (100 ft/min) downward airflow to push/pull contaminants away from the worker’s breathing zone.

Emissions pushed away from the worker’s breathing zone.

Flexible control that can be used for several tasks/operations.

Useful for manual operations for which a more contained enclosure is not feasible (e.g., larger amounts of materials or equipment).

Air volumes and control velocities of booth must be monitored/maintained to ensure proper performance.

Worker technique and interface with the work process can interfere with the capture of emissions.

Workers must be trained in the correct use.

(Continued)

Containment category

and description Advantages Disadvantages

D. Closed process design (isolation)

All steps of the process or job task are sealed with little chance of worker exposure.

Examples:

D.1. Glove box isolators (with HEPA filtered exhaust) D.2. Biological safety cabinet

class III

Emission source confined.

Minimizes external contamination.

Need for worker PPE (e.g., respirator) reduced.

More time required moving materials and equipment in and out of enclosure.

Difficulty in manipulating materials when wearing gloves.

Limitations on size of material that can be placed inside of an isolator.

Need to periodically clean the enclosure.

Adapted from Industrial Ventilation [ACGIH 2007]

Table 6–6 (Continued). Examples of engineering controls

Table 6–7. Engineering controls to reduce CNT and CNF exposures

Process/activity Potential exposure source and recommended containment of exposure*

A. Pilot and research development

operations Exposure Source: Synthesis of CNT and CNF by fluidized-bed, chemical vapor deposition, etc.: a) collection/harvesting after synthesis, b) powder transfer, c) cleaning reactor, d) removal of CNT and CNF from a substrate, e) purification and/or functionalization of CNT or CNF [note: potential exposures are generally to small quantities of CNT and CNF (i.e., µg, mg) compared to exposure to larger amounts (e.g., kg) during full-scale manufacturing/synthesis (see C below)].

Exposure Controls: a) laboratory fume hood (with HEPA filtered exhaust when warranted), b) HEPA-filtered exhausted enclosure (glove box), or c) biological safety cabinet. Local exhaust ventilation (LEV) may be required when opening reactor and during harvesting.

B. Research laboratories Exposure Source: Handling (e.g., mixing, weighing, blending, transferring) small quantities (e.g., µg, mg) of CNT or CNF powder or during sonication of a CNT or CNF liquid suspension.

Exposure Controls: a) laboratory fume hood (with HEPA filtered exhaust when warranted), b) HEPA-filtered exhausted enclosure (glove box isolator), or c) biological safety cabinet.

C. CNT and CNF manufacturing

and synthesis Exposure Source: Synthesis of CNT and CNF by fluidized-bed, chemical vapor deposition, etc., including: a) collection/harvesting after synthesis, b) drum and bag filling, c) powder transfer, d) cleaning reactor, e) removal of CNT and CNF from a substrate, f) purification and/or functionalization of CNT or CNF [Note: potential exposures are generally to large quantities (e.g., kg) of CNT and CNF].

Exposure Controls: Dedicated ventilated room with HEPA filtered exhaust, and/or LEV at source of exposure with HEPA filtered exhaust. Examples:

ventilated bagging/weighing station and/or laminar down-flow booth or non-ventilation options such as continuous liner off-loading systems for bagging operations. Ventilated bag dumping stations for product transfer.

See footnotes at end of table. (Continued)

Process/activity Potential exposure source and recommended containment of exposure*

Production and use of CNT and CNF

enabled materials and composites Exposure Source: Mixing, weighing, and transferring of small quantities of CNT or CNF powder or liquid suspension, including the: a) incorporation of CNT or CNF into matrices (e.g., polymer composites) and into coatings (e.g., inks) and, b) spraying CNT or CNF on surfaces.

Exposure Controls: a) Laboratory fume hood (with HEPA filtered exhaust when warranted), b) HEPA-filtered exhausted enclosure (glove box isolator), or c) biological safety cabinet.

Exposure Source: Handling large quantities of CNT or CNF powder that involves pouring and blending into other matrices. In addition, spinning, twisting, weaving of CNT into making rope, cloth, etc.; spray coating of surfaces.

Exposure Controls: Isolation techniques such as a dedicated ventilated room or process enclosure with HEPA filtered exhaust. Process-based controls such as ventilated bagging/weighing station, laminar down-flow booth or non-ventilation options such as continuous liner off-loading systems for bagging operations. Ventilated bag dumping stations for product transfer.

Exposure Source: Grinding, sanding, cutting, drilling or other mechanical energy applied to enabled-materials/composites containing CNT or CNF.

Exposure Controls: For the handling of small pieces of CNT or CNF enabled materials/composites: a) laboratory fume hood (with HEPA filtered exhaust when warranted), b) HEPA filtered exhausted enclosure (glove box isolator), or c) biological safety cabinet.

Exposure Controls: For handling large CNT or CNF enabled materials/

composites and where use of isolation techniques such as large ventilated enclosures are not feasible: a) use LEV at exposure source with HEPA filtered exhaust (may include LEV built into a hand-held tool), b) ventilated down-flow booths with HEPA filtered exhaust, c) laboratory fume hood (with HEPA filtered exhaust) and/or d) wet dust suppression machining techniques such as wet saws (if applicable).

*Note: Factors that influence selection of appropriate engineering controls and other exposure control strategies include the physical form (e.g., dry dispersible powder, liquid slurry, in a matrix/composite), task duration, frequency, and quantity of CNT or CNF handled. Measurement of airborne exposure at the potential source of emission should be performed to confirm the effectiveness of the control measure.

Table 6–7 (Continued). Engineering controls to reduce CNT and CNF exposures

is management commitment and support for work-place safety [NIOSH 2010b]. The requirements for the education and training of workers as specified in the OSHA Hazard Communication Standard (29 CFR 1910.1200), the Hazardous Waste Opera-tion and Emergency Response Standard (29 CFR 1910.120), and as described by Kulinowski and Lippy [2011] for workers exposed to nanomateri-als, provide a minimum set of guidelines that can be used for establishing an education and training program. The establishment of a program should have written procedures (e.g., standard operating procedures [SOPs]) for: (a) ensuring management commitment to control exposures, (b) identifying and communicating potential hazards to work-ers, (c) assessing workplace exposures to CNT and CNF, (d) identifying and implementing engineer-ing and work practice controls, (e) establishengineer-ing documentation of risk management actions taken, and (f) periodically reviewing the adequacy of con-trols and other preventive practices. Management should systematically review and update these pro-cedures and convey to workers actions taken to re-solve and/or improve workplace conditions.

A program for educating workers should also in-clude both instruction and “hands-on” training that addresses the following:

• The potential health risks associated with ex-posure to CNT and CNF.

• The safe handling of CNT, CNF, and CNT- and CNF-containing materials to minimize the likelihood of inhalation exposure and skin contact, including the proper use of engineering controls, PPE (e.g., respirators, gloves), and good work practices.