Sinan Sousan, Ph.D.

BACKGROUND
Ultra-low volume (ULV) space sprays aerosolize insecticide formulated products (FP) to contact flying mosquitoes, while barrier sprays expose mosquitoes to FP residue on vegetation and other surfaces. Centers for Disease Control and Prevention bottle bioassays used to assess insecticide resistance are based on residual active ingredient (AI) exposure and do not directly relate to FP efficacy. The current pilot study developed a novel compact wind tunnel for mosquito exposure to… Show more

BACKGROUND
Ultra-low volume (ULV) space sprays aerosolize insecticide formulated products (FP) to contact flying mosquitoes, while barrier sprays expose mosquitoes to FP residue on vegetation and other surfaces. Centers for Disease Control and Prevention bottle bioassays used to assess insecticide resistance are based on residual active ingredient (AI) exposure and do not directly relate to FP efficacy. The current pilot study developed a novel compact wind tunnel for mosquito exposure to FP. Caged Aedes albopictus and Culex pipiens/quinquefasciatus were exposed to undiluted Biomist®3 + 15 FP (permethrin AI) or air (control) within the wind tunnel, transferred to new cages, and held in a 28°C incubator. Separate mosquitoes were exposed to residual permethrin AI (8 μg/mL) in bottle bioassays. Mortality was monitored 15, 30, 60, and 120 min post-exposure.

RESULTS
Chi square tests (P < 0.05) showed significantly higher mortality in Aedes compared to Culex populations for most time points in both bioassay and wind tunnel exposure groups. As expected, mosquitoes exposed to Biomist®3 + 15 showed higher mortality rates than bottle bioassay exposure to permethrin. Two Culex colonies resistant to permethrin in bottle bioassays were susceptible to Biomist®3 + 15 in the wind tunnel.

CONCLUSION
The novel compact wind tunnel developed here may be an alternative to field trials for testing FP efficacy, avoiding factors such as weather, logistical planning, and extended personnel hours. The wind tunnel could allow programs to conveniently test efficacy of multiple FP. Comparisons of different insecticide exposure methods provide practical information to inform operational decisions. Show less

The Coronavirus disease 2019 (COVID-19) pandemic demonstrated the threat of airborne pathogenic respiratory viruses such as the airborne Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). The ability to detect circulating viruses in a workplace or dormitory setting allows an early warning system that can alert occupants to implement precautions (e.g. masking) and/or trigger individual testing to allow isolation and quarantine measures to halt contagion. This work extends and… Show more

The Coronavirus disease 2019 (COVID-19) pandemic demonstrated the threat of airborne pathogenic respiratory viruses such as the airborne Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). The ability to detect circulating viruses in a workplace or dormitory setting allows an early warning system that can alert occupants to implement precautions (e.g. masking) and/or trigger individual testing to allow isolation and quarantine measures to halt contagion. This work extends and validates the first successful detection of SARS-CoV-2 virus in dormitory Heating, Ventilation, and Air Conditioning (HVAC) systems and compares different air sampling methods and media types combined with optimized quantitative Reverse-Transcription PCR (qRT-PCR) analysis. The study was performed in two environments; large dormitories of students who underwent periodic testing for COVID-19 (unknown environment) and the HVAC air from a suite with a student who had tested positive for COVID-19 (known dorm). The air sampling methods were performed using Filter Cassettes, BioSampler, AerosolSense Sampler and Button Sampler (with four media types with different pore sizes of 5 μm, 3 μm, 3 μm (gelatin), and 1.2 μm). The SARS-CoV-2 positive air samples were compared with the positive samples collected by individual student campus track tracing methods using PCR testing on saliva and nasopharyngeal samples. The results show a detection rate of 73% in the unknown environment and a 78% detection rate in the known dorm. Our data show that the virus was detectable with all the sampling methods we employed. However, the AerosolSense sampler and BioSampler performed the best at 63% and 61% detection rates, compared to 25% for the Filter Cassettes and 23% for the Button Sampler. Despite the success rate, it is not possible to definitively conclude which method is most sensitive due to the limited number of samples. Show less

Outdoor workers perform tasks throughout the year that expose them to solar ultraviolet radiation (UVR) and increase their risk of UVR-related adverse health effects. Multiple studies on occupational solar UVR exposures during summer have been published but similar investigations during other seasons are limited. The purpose of this study was to assess solar UVR exposure in an eastern North Carolina university setting during all four seasons (fall, winter, spring, and summer) to assess risk for… Show more

Outdoor workers perform tasks throughout the year that expose them to solar ultraviolet radiation (UVR) and increase their risk of UVR-related adverse health effects. Multiple studies on occupational solar UVR exposures during summer have been published but similar investigations during other seasons are limited. The purpose of this study was to assess solar UVR exposure in an eastern North Carolina university setting during all four seasons (fall, winter, spring, and summer) to assess risk for outdoor workers, particularly groundskeepers, throughout the year. UVR effective irradiance (UVReff) was measured by area monitoring using a digital data-logging radiometer and a weatherproof UVR detector for 164 days from October 2020 to October 2021. Results showed that hourly and daily mean UVReff exceeded the 1-hr and 8-hr ACGIH Threshold Limit Values (TLVs), respectively, in all months and seasons at varying degrees. Winter had the lowest mean UVReff (3.4 × 10−3 ± 1.7 × 10−3 mW/cm2), but 91.1% and 100% of the hourly and daily UVReff measurements, respectively, still exceeded the TLVs. This study demonstrates the risk of overexposure to solar UVR among outdoor workers during cold months and seasons and the importance of implementing UVR protection throughout the year. Show less

Electronic cigarette (ECIG) use continues to be highly prevalent, especially among youth and young adults. Potential exposure from secondhand ECIG particulate matter (PM) places bystanders in danger of inhaling harmful substances, especially in confined spaces. This study was conducted to measure the potential exposure from secondhand ECIG PM exposure in vehicles, with participants completing a 30-min ECIG use session in their own vehicle with their preferred ECIG device. Sessions included a… Show more

Electronic cigarette (ECIG) use continues to be highly prevalent, especially among youth and young adults. Potential exposure from secondhand ECIG particulate matter (PM) places bystanders in danger of inhaling harmful substances, especially in confined spaces. This study was conducted to measure the potential exposure from secondhand ECIG PM exposure in vehicles, with participants completing a 30-min ECIG use session in their own vehicle with their preferred ECIG device. Sessions included a 5-min, 10-puff directed bout (30-s interpuff interval), followed by a 25-min ad libitum bout in which participants could take as many puffs as desired. Real-time PM1, PM2.5, and PM10 (the 50% efficiency mass cut-off of that passes through a size-selective inlet at 1 μm, 2.5 μm, and 10 μm aerodynamic diameters, respectively) measurements were captured during the sessions using portable PM monitors (MiniWRAS, pDR, SidePak, and GeoAir2 low-cost monitors). A total of 56 participants with valid measurements were included in the study, with a total of 13 unique ECIG device brands, including Vuse Alto, Box Air Bar, ElfBar, Esco Bar, Aegis Legend, Hyde Edge, JUUL, Kang Onee Stick, Kang Onee Stick Plus, Nord X, Nord 2, Nord 3, and Vaporesso. During the 5-min directed bout, the highest real-time PM2.5 mean concentrations were 175 μg/m3 for the MiniWRAS, 1050 μg/m3 for pDR and 3314 μg/m3 for SidePak. The filter measurements were not detectable in most experiments, except for two participants, with one taking 205 puffs and the other taking 285 puffs, approximately 10 times the mean (30) puffs of all participants. The evaluation of GeoAir2 with the MiniWRAS showed a wide range of Pearson correlation coefficient (r) values, ranging from −0.03 to 1.00, for the 13 ECIG brands. The mass median diameter (0.31 μm–3.42 μm) and geometric standard deviation (2.47–8.21) were different based on the participants for the same ECIG brand. Show less

Swine meat provides an essential global food source. Due to economies of scale, modern U.S. swine production primarily occurs indoors to maintain an optimal environment across the stages of swine production. Indoor concentrations of dust and contaminant gases in swine production buildings increase in the winter months due to reduced ventilation to optimal building temperature. In this study, an engineering control technology designed to recirculate the air in a swine farrowing room through a… Show more

Swine meat provides an essential global food source. Due to economies of scale, modern U.S. swine production primarily occurs indoors to maintain an optimal environment across the stages of swine production. Indoor concentrations of dust and contaminant gases in swine production buildings increase in the winter months due to reduced ventilation to optimal building temperature. In this study, an engineering control technology designed to recirculate the air in a swine farrowing room through a mobile Air Handling Unit containing high-efficiency particulate filters was presented. A mobile solution could be easily deployed as an intervention method if an infectious disease outbreak occurs at a swine operation. The performance of this control technology was evaluated following deployment in a production farrowing barn for a period of six weeks during the winter in the Midwestern U.S. Contaminant concentrations of inhalable dust, respirable dust, and carbon dioxide were measured in the room treated by the prototype system and compared to contaminant concentrations measured in an untreated “control” room. Over six weeks, the mean inhalable and respirable dust concentrations observed during the study period for the “treatment” room were 2.61 and 0.14 mg/m3, respectively, compared to 3.51 and 0.25 mg/m3, respectively, for the control room. The mobile recirculating ventilation system, operating at a flow rate of 45 m3/min (5 room air exchanges per hour), reduced the inhalable dust by 25% and a reduction of 48% as measured with a real-time aerosol monitor, when compared to the control room. In addition, no concentration differences in carbon dioxide and relative humidity between the treatment and the control rooms were observed. Inhalable and respirable concentrations of dust were significantly reduced (p = 0.001), which demonstrates an essential improvement of the air quality which may prove beneficial to reduce the burden of disease among both workers and animals. Show less

Electronic cigarettes (ECIGs) generate high concentrations of particulate matter (PM), impacting the air quality inhaled by humans through secondhand exposure. ECIG liquids are available commercially and some users create their own “do-it-yourself” liquids, and these liquids often vary in the amounts of their chemical ingredients, including propylene glycol (PG) and vegetable glycerin (VG). Previous studies have quantified PM concentrations in ECIG aerosol generated from liquids containing… Show more

Electronic cigarettes (ECIGs) generate high concentrations of particulate matter (PM), impacting the air quality inhaled by humans through secondhand exposure. ECIG liquids are available commercially and some users create their own “do-it-yourself” liquids, and these liquids often vary in the amounts of their chemical ingredients, including propylene glycol (PG) and vegetable glycerin (VG). Previous studies have quantified PM concentrations in ECIG aerosol generated from liquids containing different PG/VG ratios. However, the effects of these ratios on aerosol instrument filter correction factors needed to measure PM concentrations accurately have not been assessed. Thus, ECIG aerosol filter correction factors for multiple aerosol instruments (SMPS + APS, MiniWRAS, pDR, and SidePak) were determined for five different PG/VG ratios 1) 0PG/100VG, 2) 15PG/85VG, 3) 50PG/50VG, 4) 72PG/28VG, and 5) 90PG/10VG and two different PM sizes, PM1 (1 µm and smaller) and PM2.5 (2.5 µm and smaller). ECIG aerosols were generated inside a controlled exposure chamber using a diaphragm pump and a refillable ECIG device for all the ratios. In addition, the aerosol size distribution and mass median diameter were measured for all five ECIG ratios. PM2.5 correction factors (5–7.6) for ratios 1, 2, 3, and 4 were similar for the SMPS + APS combined data, and ratios 1, 2, 3 were similar for the MiniWRAS (~2), pDR (~0.5), and SidePak (~0.24). These data suggest different correction factors may need to be developed for aerosol generated from ECIGs with high PG content. The higher correction factor values for the 90PG/10VG ratio may have resulted from greater PG volatility relative to VG and sensor losses. The correction factors (ratios 1–4) for PM2.5 were SMPS + APS data (4.96–7.62), MiniWRAS (2.02–3.64), pDR (0.50–1.07), and SidePak (0.22–0.40). These data can help improve ECIG aerosol measurement accuracy for different ECIG mixture ratios. Show less

Background
Electronic cigarette (ECIG) use in vehicles represents a public health concern due to the potential for exposure to high concentrations of particulate matter (PM) and other toxicants. This study examined the impact of ECIG use on air quality in vehicles.

Methods
People who reported current ECIG use (n=60; mean age=20.5, SD=2.3) completed a brief survey and a 30-min ECIG use session in their own vehicle. Using a protocol similar to clinical laboratory studies involving… Show more

Background
Electronic cigarette (ECIG) use in vehicles represents a public health concern due to the potential for exposure to high concentrations of particulate matter (PM) and other toxicants. This study examined the impact of ECIG use on air quality in vehicles.

Methods
People who reported current ECIG use (n=60; mean age=20.5, SD=2.3) completed a brief survey and a 30-min ECIG use session in their own vehicle. Using a protocol similar to clinical laboratory studies involving tobacco use, participants took 10 directed puffs (i.e., a directed bout with one puff every 30 s for 5 min) followed by a 25-min ad libitum period in which participants took as many puffs as desired. PM 2.5 µm in diameter or smaller (PM2.5) were measured using aerosol monitors set up to sample air from the breathing zone of the passenger seat and total puffs were recorded. The association between peak PM2.5 concentration and puff count was examined.

Results
Participants took a median 18 total puffs during the sessions. Median PM2.5 concentrations increased from 4.78 µg/m3 at baseline to 107.40 µg/m3 after the directed bout. Median peak PM2.5 concentration was 464.48 µg/m3 and ranged from 9.56 µg/m3 to 143,503.91 µg/m3 (IQR=132.72–1604.68). After removing two extreme outliers for puff count and PM2.5 concentrations, puff count was significantly correlated with peak PM2.5 concentration during the ad libitum bout (r=0.32, p=0.015).

Conclusions
ECIG use in vehicles impacts air quality negatively and may pose health risks to those present in vehicles when ECIG use is occurring. Show less

WHAT IS ALREADY KNOWN ON THIS TOPIC
Some people who use e-cigarettesf report using e-cigarettes indoors, including in vehicles, as a benefit of e-cigarettes because the aerosol does leave an unpleasant smell and they perceive that e-cigarette use will not harm bystanders, including children.

WHAT THIS STUDY ADDS
E-cigarette use in vehicles is common, almost all people who use e-cigarettes report some e-cigarette use in their vehicles, and e-cigarette use in vehicles is more common… Show more

WHAT IS ALREADY KNOWN ON THIS TOPIC
Some people who use e-cigarettesf report using e-cigarettes indoors, including in vehicles, as a benefit of e-cigarettes because the aerosol does leave an unpleasant smell and they perceive that e-cigarette use will not harm bystanders, including children.

WHAT THIS STUDY ADDS
E-cigarette use in vehicles is common, almost all people who use e-cigarettes report some e-cigarette use in their vehicles, and e-cigarette use in vehicles is more common among those who exclusively use e-cigarettes compared to cigarette smoking in vehicles among those who use both e-cigarettes and cigarettes.

E-cigarette use in vehicles when others are present may be viewed as more permissible than cigarette smoking, and while e-cigarette use was less common when children or adults were present in vehicles, the current study suggests that many who do not use tobacco may be exposed to e-cigarette aerosol when riding in vehicles with people who use e-cigarettes.

HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY
Research is needed to examine the health impacts of secondhand e-cigarette aerosol exposure in vehicles on those who do not use e-cigarettes or other tobacco products.

Policy makers may consider extending policies that prohibit smoking in vehicles to also prohibit e-cigarette use in vehicles when children are present. Show less

The popularity and widespread of electronic cigarettes (ECIGs) have warranted a necessity for monitoring different populations directly or indirectly exposed to particulate matter (PM) from ECIGs. To accurately estimate exposure to aerosols from ECIGs, it is important to correctly measure the concentration of aerosols. Real-time aerosol monitors are usually based on optics that provides biased measurements that are adjusted using filter correction factors. In addition, low-cost aerosol sensors… Show more

The popularity and widespread of electronic cigarettes (ECIGs) have warranted a necessity for monitoring different populations directly or indirectly exposed to particulate matter (PM) from ECIGs. To accurately estimate exposure to aerosols from ECIGs, it is important to correctly measure the concentration of aerosols. Real-time aerosol monitors are usually based on optics that provides biased measurements that are adjusted using filter correction factors. In addition, low-cost aerosol sensors have become popular that allow widespread of these sensors and can estimate ECIG aerosol exposure after calibration. Therefore, this study determined the filter correction factors for three aerosol monitors (MiniWRAS, pDR, and SidePak) based on exposure to six ECIG brands and two particle sizes (PM1 and PM2.5). In addition, the GeoAir2 low-cost monitor was evaluated compared to filter corrected MiniWRAS measurements for these exposures. The study also evaluated the real-time measurements and mass median diameter (MMD) for each ECIG brand. The correction factors varied between aerosol monitors, ECIG brands and particle sizes, with ranges for PM2.5 that span between 1.85 and 2.42 (MiniWRAS), 0.50 and 0.58 (pDR), and 0.24 and 0.28 (SidePak). The GeoAir2 underestimated the reference measurements but had a high correlation (r = 0.90 − 0.94), showing that the monitor can be effectively calibrated to provide good estimates. The real-time average PM2.5 measurements differed between aerosol instruments with concentrations that ranged between 1398 and 3706 μg/m3 (MiniWRAS), 5479 and 16,825 μg/m3 (pDR), and 9783 and 29,808 μg/m3 (SidePak). Finally, the MMD values spanned between 0.45 and 0.80 μm based on the MiniWRAS measurements. The differences between the raw real-time measurements for the aerosol monitors show the necessity for developing filter correction factors to accurately measure ECIG exposure. Show less

Background
Little is known about how individuals are exposed to air pollution in various daily activity spaces due to a lack of data collected in the full range of spatial contexts in which they spend their time. The limited understanding makes it difficult for people to act in informed ways to reduce their exposure both indoors and outdoors.

Objective
This study aimed to (1) assess whether personalized air quality data collected using GPS-enabled portable monitors (GeoAir2)… Show more

Background
Little is known about how individuals are exposed to air pollution in various daily activity spaces due to a lack of data collected in the full range of spatial contexts in which they spend their time. The limited understanding makes it difficult for people to act in informed ways to reduce their exposure both indoors and outdoors.

Objective
This study aimed to (1) assess whether personalized air quality data collected using GPS-enabled portable monitors (GeoAir2), coupled with travel-activity diaries, promote people’s awareness and behavioral changes regarding indoor and outdoor air pollution and (2) demonstrate the effect of places and activities on personal exposure by analyzing individual exposure profiles.

Methods
44 participants carried GeoAir2 to collect geo-referenced air pollution data and completed travel-activity diaries for three days. These data were then combined for spatial data analysis and visualization. Participants also completed pre- and post-session surveys about awareness and behaviors regarding air pollution. Paired-sample t-tests were performed to evaluate changes in knowledge, attitudes/perceptions, and behavioral intentions/practices, respectively. Lastly, follow-up interviews were conducted with a subset of participants.

Results
Most participants experienced PM2.5 peaks indoors, especially when cooking at home, and had the lowest exposure in transit. Participants reported becoming more aware of air quality in their surroundings and more concerned about its health effects (t = 3.92, p = 0.000) and took more action or were more motivated to alter their behaviors to mitigate their exposure (t = 3.40, p = 0.000) after the intervention than before. However, there was no significant improvement in knowledge (t = 0.897; p = 0.187). Show less

Indoor electronic cigarette (e-cigarettes) use exposes bystanders to airborne PM2.5 (particulate matter 2.5 µm and smaller) and volatile organic compounds (VOCs). To understand potential risks for bystanders, measuring real-time e-cigarette exposure is important. However, no study evaluates the performance of low-cost sensors for real-time measurements of indoor e-cigarette aerosol concentrations. Thirty-two low-cost GeoAir2 monitors were used to detect e-cigarette-generated PM2.5 and VOCs… Show more

Indoor electronic cigarette (e-cigarettes) use exposes bystanders to airborne PM2.5 (particulate matter 2.5 µm and smaller) and volatile organic compounds (VOCs). To understand potential risks for bystanders, measuring real-time e-cigarette exposure is important. However, no study evaluates the performance of low-cost sensors for real-time measurements of indoor e-cigarette aerosol concentrations. Thirty-two low-cost GeoAir2 monitors were used to detect e-cigarette-generated PM2.5 and VOCs inside a controlled laboratory exposure chamber. The GeoAir2 was compared to an OPC-N3 low-cost monitor and the MiniWRAS and MiniRae reference instruments. Three e-cigarette devices (JUUL, NJOY Daily, and VOOPOO DRAG 2) were used to generate emissions using a diaphragm pump programmed to puff based on e-cigarette-user puffing behaviors. The GeoAir2 PM2.5 concentrations were similar to the raw MiniWRAS PM2.5 concentrations for different e-cigarettes. For the JUUL, PM2.5 measurements were close or on the 1-1 line, for the NJOY Daily measurements were on the 1-1 line for concentrations lower than 200 µg/m3, and PM2.5 measurements were overestimated for the VOOPOO DRAG 2 (mean correlation ≥ 0.97). The OPC-N3 significantly underestimated concentrations compared to the raw and filter-corrected MiniWRAS concentrations (mean correlation ≥ 0.98). The GeoAir2 VOC concentrations compared to the MiniRAE were on the 1-1 line for the VOOPOO DRAG 2, overestimated for the JUUL and NJOY Daily (mean correlation ≥ 0.98). These results show that GeoAir2 is an effective tool for examining e-cigarette use in indoor settings, such as homes, vehicles, workplaces, vape shops, or other locations, to better understand bystander exposures to e-cigarette aerosols. Show less

Background
COVID-19 pandemic caused a high demand for respiratory protection, caused a scarcity of approved respirators and the production of alternative respiratory protection. To raise public awareness through the scientific community, bestselling respirators and masks in the United States leading online retailer, Amazon.com, were evaluated.

Methods
Ten respirators and masks, 5 Face Protective Equipment (FPE) and 5 Cloth Face Masks (CFMs), were evaluated compared to the N95… Show more

Background
COVID-19 pandemic caused a high demand for respiratory protection, caused a scarcity of approved respirators and the production of alternative respiratory protection. To raise public awareness through the scientific community, bestselling respirators and masks in the United States leading online retailer, Amazon.com, were evaluated.

Methods
Ten respirators and masks, 5 Face Protective Equipment (FPE) and 5 Cloth Face Masks (CFMs), were evaluated compared to the N95 standard. Two groups were established with the intention of comparing all masks together. The fractional efficiency and pressure drop were measured and compared to the National Institute for Occupational Safety and Health (NIOSH) standards. In addition, grading factors for protection, comfort, and affordability were developed that can be used by the scientific community to readily disseminate to consumers for the selection of the appropriate respiratory protection.

Results
Two FPE provided acceptable efficiency (>95%) similar to the N95, while the remaining products were below or extremely below NIOSH standards. All products provided pressure drops within NIOSH standards (≤35 mmH20) ranging from 2.3-10.3 mmH20. The grading factors show that the CFMs have minimal protection, and the N95 has average comfort and affordability compared to all the products.

Conclusion
The N95 remains the best respiratory protection, and in the event of the next airborne pandemic, FPEs could serve as adequate alternative protection against the viral spread. Show less

Low-cost aerosol sensors open routes to exposure assessment and air monitoring in various indoor and outdoor environments. This study evaluated the accuracy of GeoAir2––a recently developed low-cost particulate matter (PM) monitor––using two types of aerosols (salt and dust), and the effect of changes in relative humidity on its measurements in laboratory settings. For the accuracy experiments, 32 units of GeoAir2 were used, and for the humidity experiments, 3 units of GeoAir2 were used… Show more

Low-cost aerosol sensors open routes to exposure assessment and air monitoring in various indoor and outdoor environments. This study evaluated the accuracy of GeoAir2––a recently developed low-cost particulate matter (PM) monitor––using two types of aerosols (salt and dust), and the effect of changes in relative humidity on its measurements in laboratory settings. For the accuracy experiments, 32 units of GeoAir2 were used, and for the humidity experiments, 3 units of GeoAir2 were used, alongside the OPC-N3 low-cost sensor and MiniWRAS reference instrument. The normal distribution of slopes between the salt and dust aerosols was compared for the accuracy experiments. In addition, the performance of GeoAir2 in indoor environments was evaluated compared to the pDR-1500 reference instrument by collocating GeoAir2 and pDR-1500 at three different homes for five days. For salt and dust aerosols smaller than 2.5 µm (PM2.5), both GeoAir2 (r = 0.96–0.99) and OPC-N3 (r = 0.98–0.99) were highly correlated with the MiniWRAS reference instrument. However, GeoAir2 was less influenced by changes in humidity than OPC-N3. While GeoAir2 reported an increase in mass concentrations ranging from 100% to 137% for low and high concentrations, an increase between 181% and 425% was observed for OPC-N3. The normal distribution of the slopes for the salt aerosols was narrower than dust aerosol, which shows closer slope similarities for salt aerosols. This study also found that GeoAir2 was highly correlated with the pDR-1500 reference instrument in indoor environments (r = 0.80–0.99). These results demonstrate potential for GeoAir2 for indoor air monitoring and exposure assessments. Show less

Standard laboratory electronic cigarette (ECIG) puffing protocols that do not consider user behaviors, such as removing and resinserting a pod, may underestimate emissions. This study compared JUUL emissions from four 10-puff bout procedures. We generated ECIG aerosol in a chamber using a JUUL device and measured concentrations of particulate matter ≤2.5 μm in diameter (PM2.5). The JUUL pod was removed and reinserted 0 times, 1 time, 4 times, and 9 times in experiments 1–4, respectively. Mean… Show more

Standard laboratory electronic cigarette (ECIG) puffing protocols that do not consider user behaviors, such as removing and resinserting a pod, may underestimate emissions. This study compared JUUL emissions from four 10-puff bout procedures. We generated ECIG aerosol in a chamber using a JUUL device and measured concentrations of particulate matter ≤2.5 μm in diameter (PM2.5). The JUUL pod was removed and reinserted 0 times, 1 time, 4 times, and 9 times in experiments 1–4, respectively. Mean real-time PM2.5 concentration was 65.06 μg/m3 (SD = 99.53) for experiment 1, 375.50 μg/m3 (SD = 346.45) for experiment 2, 501.94 μg/m3 (SD = 450.00) for experiment 3, and 834.69 μg/m3 (SD = 578.34) for experiment 4. In this study, removing and reinserting a JUUL pod resulted in greater PM2.5 concentrations compared to puffing protocols in which the JUUL pod was not removed and reinserted. ECIGs should be examined and evaluated based on ECIG users’ real-world behaviors. Show less

Research on secondhand electronic cigarette (ECIG) aerosol exposure using aerosol monitors has demonstrated that ECIG use can generate high concentrations of particulate matter (PM) and impact indoor air quality. However, quantifying indoor air PM concentrations using real-time optical monitors with on-site calibration specifically for different PM exposures has not been established. Therefore, the ECIG aerosol filter correction factors were calculated for different PM sizes (PM1, PM2.5, and… Show more

Research on secondhand electronic cigarette (ECIG) aerosol exposure using aerosol monitors has demonstrated that ECIG use can generate high concentrations of particulate matter (PM) and impact indoor air quality. However, quantifying indoor air PM concentrations using real-time optical monitors with on-site calibration specifically for different PM exposures has not been established. Therefore, the ECIG aerosol filter correction factors were calculated for different PM sizes (PM1, PM2.5, and PM10) and different aerosol optical monitors, the MiniWRAS, pDR, and SidePak. ECIG aerosol generation was achieved using five ECIGs representing three ECIG types, disposable, pod-mod, and box mod. The aerosol size distribution by mass was measured for the five ECIGs during PM generation. Compared to the discrete filter measurements, the MiniWRAS performed the best when the concentrations were low, followed by the pDR and SidePak. The average PM concentrations and correction factor ranges for the different ECIGs were 323-1,775 µg/m3 and 0.64-6.01 for the MiniWRAS, 1,388-13,365 µg/m3 and 0.41-0.80 for the pDR, and 4,632-55,339 µg/m3 and 0.13-0.20 for the SidePak, respectively. The mass median diameter ranged from 0.41 and 0.62 µm, and most particles generated from the ECIGs were smaller than 1 µm. This study demonstrates that aerosol size distribution varies between ECIGs. Likewise, the correction factors developed for the real-time aerosol monitors are specific to the ECIG used. Thus, these data can help improve ECIG aerosol exposure measurement accuracy. Show less

Background
The COVID-19 pandemic affected universities and institutions and caused campus shutdowns with a transition to online teaching models. To detect infections that might spread on campus, we pursued research towards detecting SARS-CoV-2 in air samples inside student dorms.

Methods
We sampled air in two large dormitories for 3.5 months and a separate isolation suite containing a student who had tested positive for COVID-19. We developed novel techniques employing four methods… Show more

Background
The COVID-19 pandemic affected universities and institutions and caused campus shutdowns with a transition to online teaching models. To detect infections that might spread on campus, we pursued research towards detecting SARS-CoV-2 in air samples inside student dorms.

Methods
We sampled air in two large dormitories for 3.5 months and a separate isolation suite containing a student who had tested positive for COVID-19. We developed novel techniques employing four methods to collect air samples: Filter Cassettes, Button Sampler, BioSampler, and AerosolSense sampler combined with direct qRT-PCR SARS-CoV-2 analysis.

Results
For the two large dorms with the normal student population, we detected SARS-CoV-2 in 11 samples. When compared with student nasal swab qRT-PCR testing, we detected SARS-CoV-2 in air samples when a PCR positive COVID-19 student was living on the same floor of the sampling location with a detection rate of 75%. For the isolation dorm, we had a 100% SARS-CoV-2 detection rate with Aerosol Sense sampler.

Conclusion
Our data suggest air sampling may be an important SARS-CoV-2 surveillance technique, especially for buildings with congregant living settings (dorms, correctional facilities, barracks). Future building designs and public health policies should consider implementation of HVAC surveillance. Show less

Air and water quality at a concentrated animal feeding operation (CAFO) in Eastern North Carolina that uses a covered lagoon and anaerobic digester was evaluated for 2 weeks in August 2020. Real-time PM2.5 mass concentrations were determined using a reference ADR-1500 nephelometer and high-frequency measurements of dissolved inorganic nitrogen (DIN) were evaluated using autonomously logging sensors. Air and water quality parameters were assessed before, during and after wastewater from the… Show more

Air and water quality at a concentrated animal feeding operation (CAFO) in Eastern North Carolina that uses a covered lagoon and anaerobic digester was evaluated for 2 weeks in August 2020. Real-time PM2.5 mass concentrations were determined using a reference ADR-1500 nephelometer and high-frequency measurements of dissolved inorganic nitrogen (DIN) were evaluated using autonomously logging sensors. Air and water quality parameters were assessed before, during and after wastewater from the lagoon was irrigated onto adjacent spray fields. Reference measurements were conducted alongside a HOBO weather station to collect real-time wind speed and direction, temperature, and humidity measurements. PM2.5 concentrations varied between 0 and 159 μg/m3 with an average concentration of 11 μg/m3, below EPA standard for secondary aerosols of 15 μg/m3. Higher PM2.5 concentrations were observed when wind originated from swine barns but not from covered lagoons. Water quality data showed that DIN concentrations downgradient from the CAFO were elevated relative to upstream concentrations. A groundwater seep that drains a spray field contained the highest average DIN concentration (31.0 ± 12.8 mg L−1), which was 25 times greater than upstream DIN concentrations (1.2 ± 0.8 mg L−1). Average DIN concentration at the downstream station was lower than the seep concentration (8.6 ± 16.2 mg L−1), but approximately 8 times greater than upstream. Air quality data show that the lagoon cover was effective at mitigating air quality degradation, whereas DIN concentrations in water were similar to previous studies on CAFOs using open lagoons. In addition, air and water quality parameters were significantly (p < 0.001) higher after irrigation, indicating possible influence due to ammonia and nitrate elevation. Show less

Low-cost optical particle counters effectively measure particulate matter (PM) mass concentrations once calibrated. Sensor calibration can be established by deriving a linear regression model by performing side-by-side measurements with a reference instrument. However, calibration differences between environmental and occupational settings have not been demonstrated. This study evaluated four commercially available, low-cost PM sensors (OPC-N3, SPS30, AirBeam2, and PMS A003) in both settings… Show more

Low-cost optical particle counters effectively measure particulate matter (PM) mass concentrations once calibrated. Sensor calibration can be established by deriving a linear regression model by performing side-by-side measurements with a reference instrument. However, calibration differences between environmental and occupational settings have not been demonstrated. This study evaluated four commercially available, low-cost PM sensors (OPC-N3, SPS30, AirBeam2, and PMS A003) in both settings. The mass concentrations of three aerosols (salt, Arizona road dust, and Poly-alpha-olefin-4 oil) were measured and compared with a reference instrument. OPC-N3 and SPS30 were highly correlated (r = 0.99) with the reference instrument for all aerosol types in environmental settings. In occupational settings, SPS30, AirBeam2, and PMS A003 exhibited high correlation (>0.96), but the OPC-N3 correlation varied (r = 0.88–1.00). Response significantly (p < 0.001) varied between environmental and occupational settings for most particle sizes and aerosol types. Biases varied by particle size and aerosol type. SPS30 and OPC-N3 exhibited low bias for environmental settings, but all of the sensors showed a high bias for occupational settings. For intra-instrumental precision, SPS30 exhibited high precision for salt for both settings compared to the other low-cost sensors and aerosol types. These findings suggest that SPS30 and OPC-N3 can provide a reasonable estimate of PM mass concentrations if calibrated differently for environmental and occupational settings using site-specific calibration factors. Show less

The rapid evolution of air sensor technologies has offered enormous opportunities for community-engaged research by enabling citizens to monitor the air quality at any time and location. However, many low-cost portable sensors do not provide sufficient accuracy or are designed only for technically capable individuals by requiring pairing with smartphone applications or other devices to view/store air quality data and collect location data. This paper describes important design considerations… Show more

The rapid evolution of air sensor technologies has offered enormous opportunities for community-engaged research by enabling citizens to monitor the air quality at any time and location. However, many low-cost portable sensors do not provide sufficient accuracy or are designed only for technically capable individuals by requiring pairing with smartphone applications or other devices to view/store air quality data and collect location data. This paper describes important design considerations for portable devices to ensure effective citizen engagement and reliable data collection for the geospatial analysis of personal exposure. It proposes a new, standalone, portable air monitor, GeoAir, which integrates a particulate matter (PM) sensor, volatile organic compound (VOC) sensor, humidity and temperature sensor, LTE-M and GPS module, Wi-Fi, long-lasting battery, and display screen. The preliminary laboratory test results demonstrate that the PM sensor shows strong performance when compared to a reference instrument. The VOC sensor presents reasonable accuracy, while further assessments with other types of VOC are needed. The field deployment and geo-visualization of the field data illustrate that GeoAir collects fine-grained, georeferenced air pollution data. GeoAir can be used by all citizens regardless of their technical proficiency and is widely applicable in many fields, including environmental justice and health disparity research. Show less

Prolonged exposure to dust has been shown to have adverse health effects in agricultural workers, primarily with the development of respiratory diseases. Low-cost sensors may be cost-effective tools for farmers to determine when they are exposed to harmful levels of dust during their workday. The purpose of this study was to identify low-cost sensors that may be reliably used in occupational settings to help workers and employers identify respirable particle matter exposure. The study utilized… Show more

Prolonged exposure to dust has been shown to have adverse health effects in agricultural workers, primarily with the development of respiratory diseases. Low-cost sensors may be cost-effective tools for farmers to determine when they are exposed to harmful levels of dust during their workday. The purpose of this study was to identify low-cost sensors that may be reliably used in occupational settings to help workers and employers identify respirable particle matter exposure. The study utilized two different low-cost optical particle counters (OPCs) to collect data on dust exposure, which were worn on a belt by the participant: the OPC-N3 developed by Alphasense and the AirBeam2 developed by HabitatMap. Additionally, an AirChek TOUCH air sampling pump fit with a respirable dust aluminum cyclone allowed for the collection of respirable particulate matter (PM4) to determine the true concentration of exposure. Results show that the PM4 measurements made by the OPC-N3 are similar to the gravimetrical filter measurement at concentrations of < 50 μg/m3. In addition, the data analysis suggests that the AirBeam2 may be significantly underestimating the amount of particulate matter that farmworkers are exposed to and therefore may not be suitable for occupational exposure measurements compared to the OPC-N3. Show less

•A customized exposure chamber was used to measure the particulate respirator efficiency of NIOSH-certified respirators and home-made respirators.
•The chamber was validated using P100 and N95 respirators.
•Custom-made respirators fabricated from Halyard® H600 sterilization fabric material were claimed as N95 alternative with superior efficiency.
•The results indicated that the Halyard® H600 sterilization fabric has lower filter efficiency compared to P100 and N95, and is not… Show more

•A customized exposure chamber was used to measure the particulate respirator efficiency of NIOSH-certified respirators and home-made respirators.
•The chamber was validated using P100 and N95 respirators.
•Custom-made respirators fabricated from Halyard® H600 sterilization fabric material were claimed as N95 alternative with superior efficiency.
•The results indicated that the Halyard® H600 sterilization fabric has lower filter efficiency compared to P100 and N95, and is not recommended for use as an alternative for the N95 respirator. Show less

The quality of mass concentration estimates from increasingly popular networks of low-cost particulate matter sensors depends on accurate conversion of sensor output (e.g., voltage) into gravimetric-equivalent mass concentration, typically using a calibration procedure. This study evaluates two important sources of variability that lead to error in estimating gravimetric-equivalent mass concentration: the temporal changes in sensor calibration and the spatial and temporal variability in… Show more

The quality of mass concentration estimates from increasingly popular networks of low-cost particulate matter sensors depends on accurate conversion of sensor output (e.g., voltage) into gravimetric-equivalent mass concentration, typically using a calibration procedure. This study evaluates two important sources of variability that lead to error in estimating gravimetric-equivalent mass concentration: the temporal changes in sensor calibration and the spatial and temporal variability in gravimetric correction factors. A 40-node sensor network was deployed in a heavy vehicle manufacturing facility for 8 months. At a central location in the facility, particulate matter was continuously measured with three sensors of the network and a traditional, higher-cost photometer, determining the calibration slope and intercept needed to translate sensor output to photometric-equivalent mass concentration. Throughout the facility, during three intensive sampling campaigns, respirable mass concentrations were measured with gravimetric samplers and photometers to determine correction factors needed to adjust photometric-equivalent to gravimetric-equivalent mass concentration. Both field-determined sensor calibration slopes and intercepts were statistically different than those estimated in the laboratory (α = 0.05), emphasizing the importance of aerosol properties when converting voltage to photometric-equivalent mass concentration and the need for field calibration to determine slope. Evidence suggested the sensors’ weekly field calibration slope decreased and intercept increased, indicating the sensors were deteriorating over time. The mean correction factor in the cutting and shot blasting area (2.9) was substantially and statistically lower than that in the machining and welding area (4.6; p = 0.01). Therefore, different correction factors should be determined near different occupational processes to accurately estimate particle mass concentrations. Show less

Occupational exposure assessment is almost exclusively accomplished with personal sampling. However, personal sampling can be burdensome and suffers from low sample sizes, resulting in inadequately characterized workplace exposures. Sensor networks offer the opportunity to measure occupational hazards with a high degree of spatiotemporal resolution. Here, we demonstrate an approach to estimate personal exposure to respirable particulate matter (PM), carbon monoxide (CO), ozone (O3), and noise… Show more

Occupational exposure assessment is almost exclusively accomplished with personal sampling. However, personal sampling can be burdensome and suffers from low sample sizes, resulting in inadequately characterized workplace exposures. Sensor networks offer the opportunity to measure occupational hazards with a high degree of spatiotemporal resolution. Here, we demonstrate an approach to estimate personal exposure to respirable particulate matter (PM), carbon monoxide (CO), ozone (O3), and noise using hazard data from a sensor network. We simulated stationary and mobile employees that work at the study site, a heavy-vehicle manufacturing facility. Network-derived exposure estimates compared favorably to measurements taken with a suite of personal direct-reading instruments (DRIs) deployed to mimic personal sampling but varied by hazard and type of employee. The root mean square error (RMSE) between network-derived exposure estimates and personal DRI measurements for mobile employees was 0.15 mg/m3, 1 ppm, 82 ppb, and 3 dBA for PM, CO, O3, and noise, respectively. Pearson correlation between network-derived exposure estimates and DRI measurements ranged from 0.39 (noise for mobile employees) to 0.75 (noise for stationary employees). Despite the error observed estimating personal exposure to occupational hazards it holds promise as an additional tool to be used with traditional personal sampling due to the ability to frequently and easily collect exposure information on many employees. Show less

Due to their small size, low-power demands, and customizability, low-cost sensors can be deployed in collections that are spatially distributed in the environment, known as sensor networks. Network nodes communicated wirelessly with a central database in order to record hazard measurements at 5-min intervals. Here, we report on the temporal and spatial measurements from the network, precision of network measurements, and accuracy of network measurements with respect to field reference… Show more

Due to their small size, low-power demands, and customizability, low-cost sensors can be deployed in collections that are spatially distributed in the environment, known as sensor networks. Network nodes communicated wirelessly with a central database in order to record hazard measurements at 5-min intervals. Here, we report on the temporal and spatial measurements from the network, precision of network measurements, and accuracy of network measurements with respect to field reference instruments through 8 months of continuous deployment. During typical production periods, 1-h mean hazard levels ± standard deviation across all monitors for particulate matter (PM), carbon monoxide (CO), oxidizing gases (OX), and noise were 0.62 ± 0.2 mg m−3, 7 ± 2 ppm, 155 ± 58 ppb, and 82 ± 1 dBA, respectively. We observed clear diurnal and weekly temporal patterns for all hazards and daily, hazard-specific spatial patterns attributable to general manufacturing processes in the facility. Processes associated with the highest hazard levels were machining and welding (PM and noise), staging (CO), and manual and robotic welding (OX). Network sensors exhibited varying degrees of precision with 95% of measurements among three collocated nodes within 0.21 mg m−3 for PM, 0.4 ppm for CO, 9 ppb for OX, and 1 dBA for noise of each other. The median percent bias with reference to direct-reading instruments was 27%, 11%, 45%, and 1%, for PM, CO, OX, and noise, respectively. This study demonstrates the successful long-term deployment of a multi-hazard sensor network in an industrial manufacturing setting and illustrates the high temporal and spatial resolution of hazard data that sensor and monitor networks are capable of. We show that network-derived hazard measurements offer rich datasets to comprehensively assess occupational hazards. Our network sets the stage for the characterization of occupational exposures on the individual level with wireless sensor networks. Show less

Deployment of low-cost sensors in the field is increasingly popular. However, each sensor requires on-site calibration to increase the accuracy of the measurements. We established a laboratory method, the Average Slope Method, to select sensors with similar response so that a single, on-site calibration for one sensor can be used for all other sensors. The laboratory method was performed with aerosolized salt. Based on linear regression, we calculated slopes for 100 particulate matter (PM)… Show more

Deployment of low-cost sensors in the field is increasingly popular. However, each sensor requires on-site calibration to increase the accuracy of the measurements. We established a laboratory method, the Average Slope Method, to select sensors with similar response so that a single, on-site calibration for one sensor can be used for all other sensors. The laboratory method was performed with aerosolized salt. Based on linear regression, we calculated slopes for 100 particulate matter (PM) sensors, and 50% of the PM sensors fell within ±14% of the average slope. We then compared our Average Slope Method with an Individual Slope Method and concluded that our first method balanced convenience and precision for our application. Laboratory selection was tested in the field, where we deployed 40 PM sensors inside a heavy-manufacturing site at spatially optimal locations and performed a field calibration to calculate a slope for three PM sensors with a reference instrument at one location. The average slope was applied to all PM sensors for mass concentration calculations. The calculated percent differences in the field were similar to the laboratory results. Therefore, we established a method that reduces the time and cost associated with calibration of low-cost sensors in the field. Show less

An integrated network of environmental monitors was developed to continuously measure several airborne hazards in a manufacturing facility. The monitors integrated low-cost sensors to measure particulate matter, carbon monoxide, ozone and nitrogen dioxide, noise, temperature and humidity. The monitors were developed and tested in situ for three months in several overlapping deployments, before a full cohort of 40 was deployed in a heavy vehicle manufacturing facility for a year of data… Show more

An integrated network of environmental monitors was developed to continuously measure several airborne hazards in a manufacturing facility. The monitors integrated low-cost sensors to measure particulate matter, carbon monoxide, ozone and nitrogen dioxide, noise, temperature and humidity. The monitors were developed and tested in situ for three months in several overlapping deployments, before a full cohort of 40 was deployed in a heavy vehicle manufacturing facility for a year of data collection. The monitors collect data from each sensor and report them to a central database every 5 min. The work includes an experimental validation of the particle, gas and noise monitors. The R2 for the particle sensor ranges between 0.98 and 0.99 for particle mass densities up to 300 μg/m3. The R2 for the carbon monoxide sensor is 0.99 for concentrations up to 15 ppm. The R2 for the oxidizing gas sensor is 0.98 over the sensitive range from 20 to 180 ppb. The noise monitor is precise within 1% between 65 and 95 dBA. This work demonstrates the capability of distributed monitoring as a means to examine exposure variability in both space and time, building an important preliminary step towards a new approach for workplace hazard monitoring. Show less

Noise is a pervasive workplace hazard that varies spatially and temporally. The cost of direct-reading instruments for noise hampers their use in a network. The objectives for this work were to (1) develop an inexpensive noise sensor (<$100) that measures A-weighted sound pressure levels within ±2 dBA of a Type 2 sound level meter (SLM, ∼$1,800); and (2) evaluate 50 noise sensors for use in an inexpensive sensor network. The inexpensive noise sensor consists of an electret condenser… Show more

Noise is a pervasive workplace hazard that varies spatially and temporally. The cost of direct-reading instruments for noise hampers their use in a network. The objectives for this work were to (1) develop an inexpensive noise sensor (<$100) that measures A-weighted sound pressure levels within ±2 dBA of a Type 2 sound level meter (SLM, ∼$1,800); and (2) evaluate 50 noise sensors for use in an inexpensive sensor network. The inexpensive noise sensor consists of an electret condenser microphone, an amplifier circuit, and a microcontroller with a small form factor (28 mm by 47 mm by 9 mm) than can be operated as a stand-alone unit. Laboratory tests were conducted to evaluate 50 of the new sensors at 5 sound levels: (1) ambient sound in a quiet office; (2) a pink noise test signal from 65 to 85 dBA in 10 dBA increments; and (3) 94 dBA using a SLM calibrator. Ninety-four percent of the noise sensors (n = 46) were within ± 2 dBA of the SLM for sound levels from 65 dBA to 94 dBA. As sound level increased, bias decreased, ranging from 18.3% in the quiet office to 0.48% at 94 dBA. Overall bias of the sensors was 0.83% across the 75 dBA to 94 dBA range. These sensors are available for a variety of uses and can be customized for many applications, including incorporation into a stationary sensor network for continuous monitoring of noise in manufacturing environments. Show less

In 2016, the Mine Safety and Health Administration required the use of continuous monitors to measure respirable dust in mines and better protect miner health. The Personal Dust Monitor, PDM3700, has met stringent performance criteria for this purpose. In a laboratory study, respirable mass concentrations measured with the PDM3700 and a photometer (personal DataRam, pDR-1500) were compared to those measured gravimetrically for five aerosols of varying refractive index and density (diesel… Show more

In 2016, the Mine Safety and Health Administration required the use of continuous monitors to measure respirable dust in mines and better protect miner health. The Personal Dust Monitor, PDM3700, has met stringent performance criteria for this purpose. In a laboratory study, respirable mass concentrations measured with the PDM3700 and a photometer (personal DataRam, pDR-1500) were compared to those measured gravimetrically for five aerosols of varying refractive index and density (diesel exhaust fume, welding fume, coal dust, Arizona road dust (ARD), and salt [NaCl] aerosol) at target concentrations of 0.38, 0.75, and 1.5 mg m−3. For all aerosols except coal dust, strong, near-one-to-one, linear relationships were observed between mass concentrations measured with the PDM3700 and gravimetrically (diesel fume, slope = 0.99, R2 = 0.99; ARD, slope = 0.98, R2 = 0.99; and NaCl, slope = 0.95, R2 = 0.99). The slope deviated substantially from unity for coal dust (slope = 0.55; R2 = 0.99). Linear relationships were also observed between mass concentrations measured with the pDR-1500 and gravimetrically, but one-to-one behavior was not exhibited (diesel fume, slope = 0.23, R2 = 0.76; coal dust, slope = 0.54, R2 = 0.99; ARD, slope = 0.61, R2 = 0.99; NaCl, slope = 1.14, R2 = 0.98). Unlike the pDR-1500, mass concentrations measured with the PDM3700 appear independent of refractive index and density, suggesting that it could have applications in a variety of occupational settings. Show less

Development of an air quality monitoring network with high spatio-temporal resolution requires installation of a large number of air pollutant monitors. However, state-of-the-art monitors are costly and may not be compatible with wireless data logging systems. In this study, low-cost electro-chemical sensors manufactured by Alphasense Ltd. for detection of CO and oxidative gases (predominantly O3 and NO2) were evaluated. The voltages from three oxidative gas sensors and three CO sensors were… Show more

Development of an air quality monitoring network with high spatio-temporal resolution requires installation of a large number of air pollutant monitors. However, state-of-the-art monitors are costly and may not be compatible with wireless data logging systems. In this study, low-cost electro-chemical sensors manufactured by Alphasense Ltd. for detection of CO and oxidative gases (predominantly O3 and NO2) were evaluated. The voltages from three oxidative gas sensors and three CO sensors were recorded every 2.5 s when exposed to controlled gas concentrations in a 0.125-m3 acrylic glass chamber. Electro-chemical sensors for detection of oxidative gases demonstrated sensitivity to both NO2 and O3 with similar voltages recorded when exposed to equivalent environmental concentrations of NO2 or O3 gases, when evaluated separately. There was a strong linear relationship between the recorded voltages and target concentrations of oxidative gases (R2 > 0.98) over a wide range of concentrations. Although a strong linear relationship was also observed for CO concentrations below 12 ppm, a saturation effect was observed wherein the voltage only changes minimally for higher CO concentrations (12 to 50 ppm). The non-linear behavior of the CO sensors implied their unsuitability for environments where high CO concentrations are expected. Using a manufacturer-supplied shroud, sensors were tested at 2 different flow rates (0.25 and 0.5 Lpm) to mimic field calibration of the sensors with zero air and a span gas concentration. As with all electrochemical sensors, the tested devices were subject to drift with a bias up to 20% after 9 months of continuous operation. Alphasense CO sensors were found to be a proper choice for occupational and environmental CO monitoring with maximum concentration of 12 ppm, especially due to the field-ready calibration capability. Alphasense oxidative gas sensors are usable only if it is valuable to know the sum of the NO2 and O3 concentrations. Show less

• Carbon storage and fluxes were examined for terrestrial
ecosystems on the seven main Hawaiian Islands:
Hawaiʻi, Maui, Molokaʻi, Lanaʻi, Kahoʻolawe, Oʻahu,
and Kauaʻi. Total carbon stored in terrestrial ecosystems
across these islands was estimated to be 258 TgC, of
which 71 percent was soil organic carbon to 1 m depth,
24 percent was live biomass (above and below ground),
and 5 percent was dead biomass (a combination of litter
and downed woody debris).

Recently, inexpensive (<$300) consumer aerosol monitors (CAMs) targeted for use in homes have become available. We evaluated the accuracy, bias, and precision of three CAMs (Foobot from Airoxlab, Speck from Carnegie Mellon University, and AirBeam from HabitatMap) for measuring mass concentrations in occupational settings. In a laboratory study, PM2.5 measured with the CAMs and a medium-cost aerosol photometer (personal DataRAM 1500, Thermo Scientific) were compared to that from reference… Show more

Recently, inexpensive (<$300) consumer aerosol monitors (CAMs) targeted for use in homes have become available. We evaluated the accuracy, bias, and precision of three CAMs (Foobot from Airoxlab, Speck from Carnegie Mellon University, and AirBeam from HabitatMap) for measuring mass concentrations in occupational settings. In a laboratory study, PM2.5 measured with the CAMs and a medium-cost aerosol photometer (personal DataRAM 1500, Thermo Scientific) were compared to that from reference instruments for three aerosols (salt, welding fume, and Arizona road dust, ARD) at concentrations up to 8500 µg/m3. Three of each type of CAM were included to estimate precision. Compared to reference instruments, mass concentrations measured with the Foobot (r-value = 0.99) and medium-cost photometer (r-value=0.99) show strong correlation, whereas those from the Speck (r-value range 0.91-0.99) and AirBeam (0.7–0.96) were less correlated. The Foobot bias was (−12%) for ARD and measurements were similar to the medium-cost instrument. Foobot bias was (<−46%) for salt and welding fume aerosols. Speck bias was at 18% for ARD and −86% for welding fume. AirBeam bias was (−36%) for salt and (−83%) for welding fume. All three photometers had a bias (<−82%) for welding fume. Precision was excellent for the Foobot (coefficient of variation range: 5–8%) and AirBeam (2–9%), but poorer for the Speck (8–25%). These findings suggest that the Foobot, with a linear response to different aerosol types and good precision, can provide reasonable estimates of PM2.5 in the workplace after site-specific calibration to account for particle size and composition. Show less

We compared the performance of a low-cost (∼$500), compact optical particle counter (OPC, OPC-N2, Alphasense) to another OPC (PAS-1.108, Grimm Technologies) and reference instruments. We measured the detection efficiency of the OPCs by size from 0.5 to 5 µm for monodispersed, polystyrene latex (PSL) spheres. We then compared number and mass concentrations measured with the OPCs to those measured with reference instruments for three aerosols: salt, welding fume, and Arizona road dust. The OPC-N2… Show more

We compared the performance of a low-cost (∼$500), compact optical particle counter (OPC, OPC-N2, Alphasense) to another OPC (PAS-1.108, Grimm Technologies) and reference instruments. We measured the detection efficiency of the OPCs by size from 0.5 to 5 µm for monodispersed, polystyrene latex (PSL) spheres. We then compared number and mass concentrations measured with the OPCs to those measured with reference instruments for three aerosols: salt, welding fume, and Arizona road dust. The OPC-N2 detection efficiency was similar to the PAS-1.108 for particles larger than 0.8 µm (minimum of 79% at 1 µm and maximum of 101% at 3 µm). For 0.5-µm particles, the detection efficiency of the OPC-N2 was underestimated at 78%, whereas PAS-1.108 overestimated concentrations by 183%. The mass concentrations from the OPCs were linear (r ≥ 0.97) with those from the reference instruments for all aerosols, although the slope and intercept were different. The mass concentrations were overestimated for dust (OPC-N2, slope = 1.6; PAS-1.108, slope = 2.7) and underestimated for welding fume (OPC-N2, slope = 0.05; PAS-1.108, slope = 0.4). The coefficient of variation (CV, precision) for OPC-N2 for all experiments was between 4.2% and 16%. These findings suggest that, given site-specific calibrations, the OPC-N2 can provide number and mass concentrations similar to the PAS-1.108 for particles larger than 1 µm. Show less

Exposure to dust is a known occupational hazard in the swine industry, although efforts to measure exposures are labor intensive and costly. In this study, we evaluated a Dylos DC1100 as a low-cost (~$200) alternative to assess respirable dust concentrations in a swine building in winter. Dust concentrations were measured with collocated monitors (Dylos DC1100; an aerosol photometer, the pDR-1200; and a respirable sampler analyzed gravimetrically) placed in two locations within a swine… Show more

Exposure to dust is a known occupational hazard in the swine industry, although efforts to measure exposures are labor intensive and costly. In this study, we evaluated a Dylos DC1100 as a low-cost (~$200) alternative to assess respirable dust concentrations in a swine building in winter. Dust concentrations were measured with collocated monitors (Dylos DC1100; an aerosol photometer, the pDR-1200; and a respirable sampler analyzed gravimetrically) placed in two locations within a swine farrowing building in winter for 18-24-h periods. The particle number concentrations measured with the DC1100 were converted to mass concentration using two methods: Physical Property Method and Regression Method. Raw number concentrations from the DC1100 were highly correlated to mass concentrations measured with the pDR-1200 with a coefficient of determination (R (2)) of 0.85, indicating that the two monitors respond similarly to respirable dust in this environment. Both methods of converting DC1100 number concentrations to mass concentrations yielded strong linear relationships relative to that measured with the pDR-1200 (Physical Property Method: slope = 1.03, R (2) = 0.72; Regression Method: slope = 0.72, R (2) = 0.73) and relative to that measured gravimetrically (Physical Property Method: slope = 1.08, R (2) = 0.64; Regression Method: slope = 0.75, R (2) = 0.62). The DC1100 can be used as a reasonable indicator of respirable mass concentrations within a CAFO and may have broader applicability to other agricultural and industrial settings. Show less

Low-cost sensors are effective for measuring the mass concentration of ambient aerosols and second-hand smoke in homes, but their use at concentrations relevant to occupational settings has not been demonstrated. We measured the concentrations of four aerosols (salt, Arizona road dust, welding fume, and diesel exhaust) with three types of low-cost sensors (a DC1700 from Dylos and two commodity sensors from Sharp), an aerosol photometer, and reference instruments at concentrations up to 6500… Show more

Low-cost sensors are effective for measuring the mass concentration of ambient aerosols and second-hand smoke in homes, but their use at concentrations relevant to occupational settings has not been demonstrated. We measured the concentrations of four aerosols (salt, Arizona road dust, welding fume, and diesel exhaust) with three types of low-cost sensors (a DC1700 from Dylos and two commodity sensors from Sharp), an aerosol photometer, and reference instruments at concentrations up to 6500 µg/m3. Raw output was used to assess sensor precision and develop equations to compute mass concentrations. EPA and NIOSH protocols were used to assess the mass concentrations estimated with low-cost sensors compared to reference instruments. The detection efficiency of the DC1700 ranged from 0.04% at 0.1 µm to 108% at 5 µm, as expected, although misclassification of fine and coarse particles was observed. The raw output of the DC1700 had higher precision (lower coefficient of variation, CV = 7.4%) than that of the two sharp devices (CV = 25% and 17%), a finding attributed to differences in manufacturer calibration. Aerosol type strongly influenced sensor response, indicating the need for on-site calibration to convert sensor output to mass concentration. Once calibrated, however, the mass concentration estimated with low-cost sensors was highly correlated with that of reference instruments (R2= 0.99). These results suggest that the DC1700 and Sharp sensors are useful in estimating aerosol mass concentration for aerosols at concentrations relevant to the workplace. Show less

Spatially explicit forest carbon (C) monitoring aids conservation and climate change mitigation efforts, yet few approaches have been developed specifically for the highly heterogeneous landscapes of oceanic island chains that continue to undergo rapid and extensive forest C change. We developed an approach for rapid mapping of aboveground C density (ACD; units = Mg or metric tons C ha−1) on islands at a spatial resolution of 30 m (0.09 ha) using a combination of cost-effective airborne LiDAR… Show more

Spatially explicit forest carbon (C) monitoring aids conservation and climate change mitigation efforts, yet few approaches have been developed specifically for the highly heterogeneous landscapes of oceanic island chains that continue to undergo rapid and extensive forest C change. We developed an approach for rapid mapping of aboveground C density (ACD; units = Mg or metric tons C ha−1) on islands at a spatial resolution of 30 m (0.09 ha) using a combination of cost-effective airborne LiDAR data and full-coverage satellite data. We used the approach to map forest ACD across the main Hawaiian Islands, comparing C stocks within and among islands, in protected and unprotected areas, and among forests dominated by native and invasive species. Show less

An overview of the LADCO (Lake Michigan Air Directors Consortium) Winter Nitrate Study (WNS) is presented. Sampling was conducted at ground level at an urban-rural pair of sites during January–March 2009 in eastern Wisconsin, toward the western edge of the US Great Lakes region. Areas surrounding these sites experience multiday episodes of wintertime PM2.5 pollution characterized by high fractions of ammonium nitrate in PM, low wind speeds, and air mass stagnation. Hourly surface monitoring of… Show more

An overview of the LADCO (Lake Michigan Air Directors Consortium) Winter Nitrate Study (WNS) is presented. Sampling was conducted at ground level at an urban-rural pair of sites during January–March 2009 in eastern Wisconsin, toward the western edge of the US Great Lakes region. Areas surrounding these sites experience multiday episodes of wintertime PM2.5 pollution characterized by high fractions of ammonium nitrate in PM, low wind speeds, and air mass stagnation. Hourly surface monitoring of inorganic gases and aerosols supplemented long-term 24-h aerosol chemistry monitoring at these locations. The urban site (Milwaukee, WI) experienced 13 PM2.5 episodes, defined as periods where the seven-hour moving average PM2.5 concentration exceeded 27 μg m−3 for at least four consecutive hours. The rural site experienced seven episodes by the same metric, and all rural episodes coincided with urban episodes. Episodes were characterized by low pressure systems, shallow/stable boundary layer, light winds, and increased temperature and relative humidity relative to climatological mean conditions. Show less

Noise is a pervasive workplace hazard that varies spatially and temporally. The cost of direct-reading instruments for noise hampers their use in a network. The objectives for this work were to (1) develop an inexpensive noise sensor (<$100) that measures A-weighted sound pressure levels within ±2 dBA of a Type 2 sound level meter (SLM, ∼$1,800); and (2) evaluate 50 noise sensors for use in an inexpensive sensor network. The inexpensive noise sensor consists of an electret condenser… Show more

Noise is a pervasive workplace hazard that varies spatially and temporally. The cost of direct-reading instruments for noise hampers their use in a network. The objectives for this work were to (1) develop an inexpensive noise sensor (<$100) that measures A-weighted sound pressure levels within ±2 dBA of a Type 2 sound level meter (SLM, ∼$1,800); and (2) evaluate 50 noise sensors for use in an inexpensive sensor network. The inexpensive noise sensor consists of an electret condenser microphone, an amplifier circuit, and a microcontroller with a small form factor (28 mm by 47 mm by 9 mm) than can be operated as a stand-alone unit. Laboratory tests were conducted to evaluate 50 of the new sensors at 5 sound levels: (1) ambient sound in a quiet office; (2) a pink noise test signal from 65 to 85 dBA in 10 dBA increments; and (3) 94 dBA using a SLM calibrator. Ninety-four percent of the noise sensors (n = 46) were within ± 2 dBA of the SLM for sound levels from 65 dBA to 94 dBA. As sound level increased, bias decreased, ranging from 18.3% in the quiet office to 0.48% at 94 dBA. Overall bias of the sensors was 0.83% across the 75 dBA to 94 dBA range. These sensors are available for a variety of uses and can be customized for many applications, including incorporation into a stationary sensor network for continuous monitoring of noise in manufacturing environments. Show less

Field and laboratory studies were conducted to evaluate the impact of proppant sand mining and processing activities on community particulate matter (PM) concentrations. In field studies outside 17 homes within 800 m of sand mining activities (mining, processing, and transport), respirable (PM4) crystalline silica concentrations were low (< 0.4 μg/m3) with crystalline silica detected on 7 samples (2% to 4% of mass). In long-term monitoring at 6 homes within 800 m of sand mining activities… Show more

Field and laboratory studies were conducted to evaluate the impact of proppant sand mining and processing activities on community particulate matter (PM) concentrations. In field studies outside 17 homes within 800 m of sand mining activities (mining, processing, and transport), respirable (PM4) crystalline silica concentrations were low (< 0.4 μg/m3) with crystalline silica detected on 7 samples (2% to 4% of mass). In long-term monitoring at 6 homes within 800 m of sand mining activities, the highest daily mean PM concentrations observed were 14.5 μg/m3 for PM2.5 and 37.3 μg/m3 for PM10, although infrequent (< 3% of time), short-term elevated PM concentrations occurred when wind blew over the facility. In laboratory studies, aerosolized sand was shown to produce respirable-sized particles, containing 6% to 19% crystalline silica. Dispersion modeling of a mine and processing facility indicated that PM10 can exceed standards short distances (< 40 m) beyond property lines. Lastly, fence-line PM and crystalline silica concentrations reported to state agencies were substantially below regulatory or guideline values, although several excursions were observed for PM10 when winds blew over the facility. Taken together, community exposures to airborne particulate matter from proppant sand mining activities at sites similar to these appear to be unlikely to cause chronic adverse health conditions. Show less