Spatial and temporal variability of incidental nanoparticles in indoor workplaces: impact on the characterization of point source exposures
- DOI
- Language of the publication
- English
- Date
- 2014-10-29
- Type
- Article
- Author(s)
- Niu, Jianjun
- Rasmussen, Pat E.
- Magee, Robert
- Nilsson, Gregory
- Publisher
- Royal Society of Chemistry
Abstract
This study deployed a suite of direct-reading instruments in six locations inside one building to characterize variability of the background aerosol, including incidental nanoparticles (NP), over a six month period. The instrument suite consisted of a portable Condensation Particle Counter (CPC) and a Scanning Mobility Particle Sizer (SMPS) for assessing particle number concentrations and size distributions in the nano-scale range; an Aerodynamic Particle Sizer (APS) for assessing micron-scale particle number concentrations and size distributions; plus a desktop Aerosol Monitor (DustTrak DRX) and a Diffusion Charger (DC2000CE) for assessing total particle mass and surface area concentrations respectively. In terms of number concentration, NPs (<100 nm) were the dominant particles observed in the background aerosol, contributing up to 53–93% of the total particle number concentrations. The particle size distributions were bimodal with maxima around 19–79 nm and 50–136 nm, respectively, depending on workplace locations. The average detected background particle number, surface area and total mass concentrations were below 7.1 × 103 # cm−3, 22.9 μm2 cm−3 and 33.5 μg m−3, respectively in spring samples and below 1.8 × 103 # cm−3, 10.1 μm2 cm−3 and 12.0 μg m−3, respectively in winter samples. A point source study using an older model laser printer as the emission source indicated that NPs emitted from the investigated printer were distinguishable from background. However, more recent low emitting printers are likely to be indistinguishable from background, and chemical characterization (e.g. VOCs, metals) would be required to help identify emission sources.
Plain language summary
Under the Clean Air Regulatory Agenda (CARA), Health Canada has been given the mandate to acquire the foundational knowledge necessary to assess indoor air pollutants and to develop and implement guidelines and other tools to better manage indoor air quality. In this study, Health Canada collaborated with the National Research Council to characterize ultrafine particles (less than 100 nanometers in diameter) originating in the indoor workplace. A suite of direct-reading instruments was used to assess particle number, surface area and mass concentrations as well as particle size distributions in six different locations in one example building. The results show that the behaviour of ultrafine particles varies widely from room to room, depending on the characteristics of the room, the type of human activity and whether the measurements are taken in the winter or summer season. Ultrafine particle concentrations generally decrease at night. Most of the particles fall into two size ranges: from 19-79 nm and from 50-136 nm, depending on workplace locations. The study also included an evaluation of instrument performance in a room-sized experimental chamber, with the goal of recommending a suite of instruments for monitoring ultrafine particles. The performance of newly available portable instruments compared well with large stationary instruments that are currently the scientific standard. It was concluded that a combination of instruments is required to fully characterize exposures to ultrafine particles, because no one instrument can provide all the required information. The study results will be used to assess and improve upon techniques to characterize indoor air pollutant exposures.
Subject
- Health,
- Health and safety