Abstract
(1) Background: Small, lightweight, low-cost optical particulate matter (PM) monitors are becoming popular in the field of occupational exposure monitoring, because these devices allow for real-time static measurements to be collected at multiple locations throughout a work site as well as being used as wearables providing personal exposure estimates. Prior to deployment, devices should be evaluated to optimize and quantify measurement accuracy. However, this can turn out to be difficult, as no standardized methods are yet available and different deployments may require different evaluation procedures. To gain insight in the relevance of different variables that may affect the monitor readings, six PM monitors were selected based on current availability and evaluated in the laboratory; (2) Methods: Existing strategies that were judged appropriate for the evaluation of PM monitors were reviewed and seven evaluation variables were selected, namely the type of dust, within- and between-device variations, nature of the power supply, temperature, relative humidity, and exposure pattern (peak and constant). Each variable was tested and analyzed individually and, if found to affect the readings significantly, included in a final correction model specific to each monitor. Finally, the accuracy for each monitor after correction was calculated; (3) Results: The reference materials and exposure patterns were found to be main factors needing correction for most monitors. One PM monitor was found to be sufficiently accurate at concentrations up to 2000 µg/m3 PM2.5, with other monitors appropriate at lower concentrations. The average accuracy increased by up to three-fold compared to when the correction model did not include evaluation variables; (4) Conclusions: Laboratory evaluation and readings correction can greatly increase the accuracy of PM monitors and set boundaries for appropriate use. However, this requires identifying the relevant evaluation variables, which are heavily reliant on how the monitors are used in the workplace. This, together with the lack of current consensus on standardized procedures, shows the need for harmonized PM monitor evaluation methods for occupational exposure monitoring.
Highlights
Low-cost lightweight optical monitors for measuring airborne particulate matter (PM)concentrations in near real-time are becoming available and may be applied to a multitude of purposes, including occupational exposure monitoring [1,2]
Transient exposure patterns were performed for each reference material with combinations of high, average or low temperature and relative humidity to investigate if these three parameters affected the corrected APS readings (Figure 1c)
Six low-cost PM monitors to be used for occupational exposure monitoring were evaluated in laboratory conditions
Summary
Low-cost lightweight optical monitors for measuring airborne particulate matter (PM)concentrations in near real-time are becoming available and may be applied to a multitude of purposes, including occupational exposure monitoring [1,2]. Low-cost optical PM monitors (hereafter referred to as “PM monitors”) could potentially provide substantial benefits to the monitoring of PM in occupational settings compared to traditional gravimetric PM exposure assessment methods, which rely on sampling pumps and filters. These methods are based on collecting PM on a filter followed by gravimetrical analysis. Most monitors can report and process the data as soon as it is collected and while the instrument is still deployed This allows direct feedback and intervention systems that can immediately prevent further exposure. The reduced cost, ease of deployment, direct reading capabilities together with the wireless network ability of this technology mean that new ways of collecting and sharing occupational hygiene information between employers, employees and regulators become possible
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