Exposure Controls for Nanomaterials at Three Manufacturing Sites

Abstract

Because nanomaterials are thought to be more biologically active than their larger parent compounds, careful control of exposures to nanomaterials is recommended. Field studies were conducted at three sites to develop information about the effectiveness of control measures including process changes, a downflow room, a ventilated enclosure, and an enclosed reactor. Aerosol mass and number concentrations were measured during specific operations with a photometer and an electrical mobility particle sizer to provide concentration measurements across a broad range of sizes (from 5.6 nm to 30 μm). At site A, the dust exposure and during product harvesting was eliminated by implementing a wait time of 30 minutes following process completion. And, the dust exposure attributed to process tank cleaning was reduced from 0.7 to 0.2 mg/m3 by operating the available process ventilation during this task. At site B, a ventilated enclosure was used to control dust generated by the manual weigh-out and manipulation of powdered nanomaterials inside of a downflow room. Dust exposures were at room background (under 0.04 mg/m3 and 500 particles/cm3) during these tasks however, manipulations conducted outside of the enclosure were correlated with a transient increase in concentration measured at the source. At site C, a digitally controlled reactor was used to produce aligned carbon nanotubes. This reactor was a closed system and the ventilation functioned as a redundant control measure. Process emissions were well controlled by this system with the exception of increased concentrations measured during the unloading the product. However, this emission source could be easily controlled through increasing cabinet ventilation. The identification and adoption of effective control technologies is an important first step in reducing the risk associated with worker exposure to engineered nanoparticles. Properly designing and evaluating the effectiveness of these controls is a key component in a comprehensive health and safety program.

Performance study of portable devices for the real-time measurement of airborne particle number concentration and size (distribution)

“…Methodologies to assess occupational inhalation exposure to airborne particles during production, handling and use of manufactured nanomaterials have recently been proposed [6][7][8][9][10][11][12] and tested in various workplace environments [13][14][15][16][17][18]. In particular, these strategies emphasize the utility of real-time instruments.…”

Deposition of graphene nanomaterial aerosols in human upper airways

“…A field sampling study conducted at a graphene manufactory also indicated that graphene aerosols released in the workplaces was primarily graphene agglomerates. (14) Therefore, the use of size classified graphene nanoparticles in the form of agglomeration for airway deposition experiments in this study is considered realistic and also practical to a certain extent. It is widely accepted that graphene agglomerates, once deposited in the lung airways, will gradually disperse in the lung mucus where the onset of graphene platelets nanotoxicity effects found in those in vivo and in vitro studies can then be seen.…”

“…Due to the fact that graphene materials inevitably could become airborne during product harvesting, handling, and reactor cleaning processes in related workplaces, (14) workers and researchers in graphene associated manufactories and laboratories could involuntarily inhale graphene nanoparticles. The consequent deposition of graphene nanoparticles in workers’ respiratory tract could potentially pose adverse health effects to them.…”

The Effectiveness of Specific Risk Mitigation Techniques Used in the Production and Handling of Manufactured Nanomaterials: A Systematic Review

“…One paper on an international survey regarding occupational health and safety programs, engineering controls and PPE, did not contain data on the concentrations of airborne MNMs particles [13] and could not be used for the calculation of PFs. The remaining 14 papers reported on: enclosure systems (down flow clean rooms with ventilated enclosure hood); ventilation (LEV, enclosure type LEV with proper face velocity, process ventilation, biosafety cabinets); specialized ventilation systems (thermal displacement ventilation); and segregation sources (reactor cabinets) [7][8][9][10][11][12][14][15][16][17][18][19][20][21].…”