Abstract
BackgroundNanoparticle emission assessment technique was developed to semi-quantitatively evaluate nanomaterial exposures and employs a combination of filter based samples and portable real-time particle monitors, including a condensation particle counter (CPC) and an optical particle counter (OPC), to detect nanomaterial releases. This laboratory study evaluated the results from CPC and OPC simultaneously measuring a polydisperse aerosol to assess their variability and accuracy.Methods and ResultsTwo CPCs and two OPCs were used to evaluate a polydisperse sodium chloride aerosol within an enclosed chamber. The measurement results for number concentration versus time were compared between paired particle monitors of the same type, and to results from the Scanning Mobility Particle Spectrometer (SMPS) which was widely used to measure concentration of size-specific particles. According to analyses by using the Bland-Altman method, the CPCs displayed a constant mean percent difference of −3.8% (95% agreement limits: −9.1 to 1.6%; range of 95% agreement limit: 10.7%) with the chamber particle concentration below its dynamic upper limit (100,000 particles per cubic centimeter). The mean percent difference increased from −3.4% to −12.0% (range of 95% agreement limits: 7.1%) with increasing particle concentrations that were above the dynamic upper limit. The OPC results showed the percent difference within 15% for measurements in particles with size ranges of 300 to 500 and 500 to 1000 regardless of the particle concentration. Compared with SMPS measurements, the CPC gave a mean percent difference of 22.9% (95% agreement limits: 10.5% to 35.2%); whereas the measurements from OPC were not comparable.ConclusionsThis study demonstrated that CPC and OPC are useful for measuring nanoparticle exposures but the results from an individual monitor should be interpreted based upon the instrument's technical parameters. Future research should challenge these monitors with particles of different sizes, shapes, or composition, to determine measurement comparability and accuracy across various workplace nanomaterials.
Highlights
A nanoparticle is defined as a nano-object with at least one dimension that is less than 100 nanometers [1]
This study demonstrated that condensation particle counter (CPC) and optical particle counter (OPC) are useful for measuring nanoparticle exposures but the results from an individual monitor should be interpreted based upon the instrument’s technical parameters
The direct-reading instruments described in the nanoparticle emission assessment technique (NEAT) include two portable real-time aerosol monitors, a condensation particle counter (CPC) which measures in particles per cubic centimeter of air (#/cc) and an optical particle counter (OPC) which measures in particles per liter of air (#/L) [10]
Summary
A nanoparticle is defined as a nano-object with at least one dimension that is less than 100 nanometers (nm) [1]. In 2008, the National Institute for Occupational Safety and Health (NIOSH) nanotechnology field study team developed a nanoparticle emission assessment technique (NEAT), which employed a combination of direct-reading, portable instruments to detect releases of airborne nanomaterial coupled with filter-based air sampling and subsequent chemical and microscopic analyses for particle identification and chemical speciation [4,10] This technique has been used to assess potential nanomaterial exposure and the effectiveness of engineering controls in occupational settings [11,12]. The direct-reading instruments described in the NEAT include two portable real-time aerosol monitors, a condensation particle counter (CPC) which measures in particles per cubic centimeter of air (#/cc) and an optical particle counter (OPC) which measures in particles per liter of air (#/L) [10] These instruments are used to supplement the filter based sampling, and aid the investigator in determining potential emissions or recommending exposure controls. This laboratory study evaluated the results from CPC and OPC simultaneously measuring a polydisperse aerosol to assess their variability and accuracy
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