  To mitigate the significant biases/errors in research studying the
associations between PM and health, which are introduced by the
coarse/inadequate assessments of PM exposure from conventional PM monitoring
paradigm, a personalized monitoring system consisting of a low-cost wearable PM
device is proposed. However, due to the absence of a unifying evaluation
protocol for low-cost PM sensors, the evaluation results/performance
specifications from existing studies/datasheets are of limited reference values
when attempting to determine the best candidate for the proposed system. In
this regard, the authors appeal to the research community to develop a
standardized evaluation protocol for low-cost PM sensors/devices, and a
unifying attempt is established in this manuscript by adopting the definitive
terminology from international documents and the evaluation metrics regarded as
best practices. Collocated on the rooftop of the HKUST Supersite, four
empirically selected PM sensors were compared against each other and calibrated
against two reference monitors. They were then evaluated against the reference
following the protocol. The PlanTower PMS-A003 sensor was selected for the
wearable device as it outperformed the others in terms of affordability,
portability, detection capability, data quality, as well as humidity and
condensation insusceptibility. An automated approach was proposed to identify
and remove the condensation associated abnormal measurements. The proposed
device has better affordability and portability as well as similar usability
and data accessibility compared to those existing devices recognized. The first
10 devices were also evaluated and calibrated at the Supersite. Additional 120
units were manufactured and delivered to the subjects to acquire their daily
PM2.5 exposures for investigating the association with subclinical
atherosclerosis.
