Aerosol Measurement Degradation in Low-Cost Particle Sensors Using Laboratory Calibration and Field Validation.

Increasing concern over air pollution has led to the development of low-cost sensors suitable for wide-scale deployment and use by citizen scientists. This project investigated the AirU low-cost particle sensor using two methods: (1) a comparison of pre- and post-deployment calibration equations for 24 devices following use in a field study, and (2) an in-home comparison between 3 AirUs and a reference instrument, the GRIMM 1.109. While differences (and therefore some sensor degradation) were found in the pre- and post-calibration equation comparison, absolute value changes were small and unlikely to affect the quality of results. Comparison tests found that while the AirU did tend to underestimate minimum and overestimate maximum concentrations of particulate matter, ~88% of results fell within ±1 µg/m3 of the GRIMM. While these tests confirm that low-cost sensors such as the AirU do experience some sensor degradation over multiple months of use, they remain a valuable tool for exposure assessment studies. Further work is needed to examine AirU performance in different environments for a comprehensive survey of capability, as well as to determine the source of sensor degradation.

Incidence of Workers' Compensation Claims in Opioid-Using Truck Drivers.

OBJECTIVE: This study examines the relationship between opioid use prevalence and subsequent filing of workers' compensation claims. METHODS: A retrospective cohort study design was utilized to examine data from drivers' initial commercial driver medical exam, employment data, and workers' compensation claims data. RESULTS: Data from 57,733 over 7 years were analyzed. Drivers who reported opioid use at their initial medical exam visit filed subsequent workers' compensation claims 1.81 times sooner (P = 0.0001; 95% CI 1.34, 2.44) than drivers who did not report opioid use at their CDME when controlling for age, gender, BMI, and diastolic blood pressure. CONCLUSIONS: These findings provide information that may aid in improving regulations to control for incidents, training programs to inform professional drivers of factors that increase accident risk and educating prescribers about increased risks of injury among opioid-using drivers.

Development of an Empirical Formula for Describing Human Inhalability of Airborne Particles at Low Wind Speeds and Calm Air.

Based on experiments conducted in low wind speed and calm air environments, the current International Organization for Standardization (ISO) and European Committee for Standardization (CEN) convention modeling human aerosol inhalability (i.e. aspiration efficiency) may not be valid when wind speeds are less than 0.5 ms-1. Additionally, the convention is based primarily on mouth breathing data and aerosols with aerodynamic diameters smaller than 100 µm. Since the convention's development, experimental inhalation data at wind speeds lower than 0.5 ms-1 for nose, mouth, and oronasal breathing have been generated for aerosols in a wider range of sizes (1.5-135 µm). These data were gathered and modeled with the intention of providing a simple convention recommendation for inhalability in low wind speed (>0 to <0.5 ms-1) and calm air (~0 ms-1) conditions to the ISO Technical Committee (TC) 146, Subcommittee 2, Working Group (WG) 1 ('Particle Size-Selective Sampling and Analysis'), as it relates to standard ISO 7708, and to CEN TC 137/WG 3, as it relates to standard EN 481. This paper presents several equations as possibilities, all relating aspiration efficiency to aerodynamic diameter. The equation AE=1+0.000019dae2-0.009788dae stands out as a possible new convention. This polynomial model balances simplicity and fit while addressing the weakness of the current convention.

Relationships Between Poor Health and Calories From Fat Among Commercial Truck Drivers.

OBJECTIVE: Commercial motor vehicle (CMV) drivers face many challenges to their health, including poor diet, disease, and crash risk. This study quantifies relationships between the percentage of calories from fat (PCF) and markers of poor health, many of which are associated with increased crash risk. METHODS: Cross-sectional data from 790 CMV drivers were analyzed. PCF were estimated using the National Cancer Institute Percentage Energy from Fat Screener. Adjusted odds ratios (ORs) were calculated. RESULTS: The highest category of PCF (>38.2%) was statistically significantly more likely to not exercise (OR = 2.08), have sleep apnea (OR = 2.31), snore (OR = 1.90), smoke (OR = 2.28), and use alcohol (OR = 1.87) after adjustments. CONCLUSION: Meaningful relationships between PCF and poor health indicators exist. These indicators may provide an intervention to improve the health and safety of CMV drivers.

Investigating Measurement Variation of Modified Low-Cost Particle Sensors.

Particulate matter (PM) has demonstrably increased rates of cardiovascular and respiratory related disease; thus, a low-cost sensor that accurately measures PM is desirable including for smaller and more private environments such as residential homes. The low-cost Dylos and the Utah Modified Dylos Sensor (UMDS) have been shown to be highly correlated with references instruments for measuring particle counts and aerosol concentrations, which makes them useful tools for air quality studies. An analytical calibration equation (calibration) is used to describe the linear relationship between the UMDS and a reference instrument, providing the best estimate of PM concentrations when the UMDS is operated. In this study, an investigation of measurement variation of a UMDS was performed using a low-cost calibration technique to determine differences between the brand new UMDS pre-calibration equation (Prec), a contaminated UMDS post-calibration equation (Postc), and a cleaned UMDS clean calibration equation (CC). The UMDS were calibrated against a high-grade aerosol spectrometer (Grimm model 1.109) as a reference instrument. Calibrations took place in a home or office environment. Counts per volume units from the UMDS were matched to the Grimm's for comparison. The investigation of the UMDS for measurement variation was performed for the approximate estimates of PM2.5 by using the small bin (i.e. ≥0.50µm) subtracted from the large bin (i.e. ≥2.5µm), and for total particulates by using the large bin. Linear regressions were performed between the UMDS and the Grimm per calibration event, which produced R2 values and slopes that were indicative of measurement variation. Data exceeding the upper limit of quantification (ULOQ) of 106,000 particles/liter and the lower limit of quantification (LLOQ) of 4 particles/liter were excluded from statistical comparison. R2 values greater or equal to 0.70 were used to assess measurement variation as a quality control standard for valid comparisons. A rank sum statistical test between calibration comparisons was performed. Prec/Postc and Prec/CC had significant differences indicating measurement variation. Postc/CC did not have any significant differences; cleaning the UMDS had no effect and did not demonstrate measurement variation. Reasons for measurement variation may include instrument contamination (dust/dirt), hardware degradation, altered fan flow rates, and potentially inadequate cleaning of the UMDS. Future work may investigate the rate of measurement variation in order to develop a recommended re-calibration schedule in order to maintain the most accurate estimates of PM for UMDS in long-term operation.

Characterization of CO and NO2 exposures of ice skating rink maintenance workers.

Air quality is a common concern among indoor ice rink facilities due to the use of gasoline/propane ice resurfacing equipment. Although previous studies have investigated spectator, guest, and skater exposures, a review of the literature revealed little published research regarding ice maintenance employees' exposures. Ice maintenance includes edging and resurfacing. The resurfacer is commonly referred to as a Zamboni®. Edging is almost always followed by resurfacing, but resurfacing frequently happens independently of edging. The purpose of this study was to characterize ice rink maintenance employees' exposures to CO and NO2. Employees from four ice rinks in Salt Lake County, Utah were sampled using direct reading instruments during routine ice maintenance activities. Maintenance was divided into four activities: 1) Edging only, 2) Resurfacing after edging (not including edging), 3) Edging and resurfacing (Activities 1 and 2 combined), and 4) Resurfacing only (independent of edging). Activities 1, 2 and 3 were sampled twenty-four (n = 24) times. Activity 4 was sampled eight times. Sampling results were graphed and summarized using descriptive statistics. The highest measured CO concentration was 202 ppm, which occurred during edging. Average CO concentrations for all activities ranged from 0 ppm to 60.4 ppm. Minimal CO exposure was observed when resurfacing occurred without edging, which implies that elevated CO exposure measured while using the resurfacer may be residual CO from prior edging activities. NO2 concentrations were negligible for all rinks and all activities. Results confirmed that gasoline edgers significantly contribute to indoor CO levels, with peak levels exceeding some recommended exposure levels. Indoor ice rink facilities should monitor employees' CO exposures and implement procedures to limit exposures. This may be achieved by limiting the number of laps taken with the edger or replacing gasoline powered edgers with electric edgers.

Laboratory evaluation of a low-cost, real-time, aerosol multi-sensor.

Exposure to occupational aerosols are a known hazard in many industry sectors and can be a risk factor for several respiratory diseases. In this study, a laboratory evaluation of low-cost aerosol sensors, the Dylos DC1700 and a modified Dylos known as the Utah Modified Dylos Sensor (UMDS), was performed to assess the sensors' efficiency in sampling respirable and inhalable dust at high concentrations, which are most common in occupational settings. Dust concentrations were measured in a low-speed wind tunnel with 3 UMDSs, collocated with an aerosol spectrometer (Grimm 1.109) and gravimetric respirable and inhalable samplers. A total of 10 tests consisting of 5 different concentrations and 2 test aerosols, Arizona road dust and aluminum oxide, were conducted. For the Arizona road dust, total particle count was strongly related between the spectrometer and the UMDS with a coefficient of determination (R2) between 0.86-0.92. Particle count concentrations measured with the UMDS were converted to mass and also were related with gravimetrically collected inhalable and respirable dust. The UMDS small bin (i.e., all particles) compared to the inhalable sampler yielded an R2 of 0.86-0.92, and the large bin subtracted from the small bin (i.e., only the smallest particles) compared to the respirable sampler yielded an R2 of 0.93-0.997. Tests with the aluminum oxide demonstrated a substantially lower relationship across all comparisons. Furthermore, assessment of intra-instrument variability was consistent for all instruments, but inter-instrument variability indicated that each instrument requires its own calibration equation to yield accurate exposure estimates. Overall, it appears that the UMDS can be used as a low-cost tool to estimate respirable and inhalable concentrations found in many workplaces. Future studies will focus on deployment of a UMDS network in an occupational setting.

Evaluation of physiological strain in hot work areas using thermal imagery.

BACKGROUND: Monitoring core body temperature to identify heat strain in workers engaged in hot work in heat stress environments is intrusive and expensive. Nonintrusive, inexpensive methods are needed to calculate individual Physiological Strain Index (PSI). OBJECTIVE: Thermal imaging and heart rate monitoring were used in this study to calculate Physiological Strain Index (PSI) from thermal imaging temperatures of human subjects wearing thermal protective garments during recovery from hot work. METHODS: Ten male subjects were evaluated for physiological strain while participating in hot work. Thermal images of the head and neck were captured with a high-resolution thermal imaging camera concomitant with measures of gastrointestinal and skin temperature. Lin's concordance correlation coefficient (rho_c), Pearson's coefficient (r) and bias correction factor (C-b) were calculated to compare thermal imaging based temperatures to gastrointestinal temperatures. Calculations of PSI based thermal imaging recorded temperatures were compared to gastrointestinal based PSI. RESULTS: Participants reached a peak PSI of 5.2, indicating moderate heat strain. Sagittal measurements showed low correlation (rho_c=0.133), moderate precision (r=0.496) and low accuracy (C_b=0.269) with gastrointestinal temperature. Bland-Altman plots of imaging measurements showed increasing agreement as gastrointestinal temperature rose; however, the Limits of Agreement (LoA) fell outside the ±0.25C range of clinical significance. Bland-Altman plots of PSI calculated from imaging measurements showed increasing agreement as gastrointestinal temperature rose; however, the LoA fell outside the ±0.5 range of clinical significance. CONCLUSION: Results of this study confirmed previous research showing thermal imagery is not highly correlated to body core temperature during recovery from moderate heat strain in mild ambient conditions. Measurements display a trend toward increasing correlation at higher body core temperatures. Accuracy was not sufficient at mild to moderate heat strain to allow calculation of individual physiological stress.