Airborne Levels Research Articles

Detection of 6-PPD and 6-PPDQ in airborne particulates and assessment of their toxicity in lung cells

The extensive use of synthetic antioxidants, notably N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6-PPD), in rubber-related products, particularly in tire manufacturing, has induced concerns regarding their environmental impact and potential health hazards. Despite the identification of 6-PPD and its derivative, 6-PPD quinone (6-PPDQ), in various water samples and their lethal effects on certain aquatic species (e.g., coho salmon, rainbow trout and brook trout), the levels of airborne 6-PPD/6-PPDQ and their respiratory toxicity remain relatively unexplored. In this study, we aimed to evaluate the respiratory toxicity potential of 6-PPD and its derivatives, with a specific focus on detecting these compounds in airborne particulates and assessing their toxic effects on lung cells. Characterization of four airborne fine particulate (FP) samples revealed spherical morphologies with diameters ranging from 17.7 to 225.7 nm, displaying slight agglomeration and negative surface charge. methanol/acetonitrile extraction followed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) analysis confirmed the presence of both 6-PPD and 6-PPDQ on the surfaces of FPs, with significant variations (0.26–1.05 μg g−1) in loading capacity observed among the samples. Subsequent exposure of lung cells (THP-1, BEAS-2B, and A549) to 6-PPD and 6-PPDQ revealed dose-dependent declines in mitochondrial metabolic activity induced by 6-PPD, along with severe membrane damage, ATP depletion, and pro-inflammatory cytokine release. Conversely, 6-PPDQ exhibited negligible toxicity in all tested parameters. These findings underscore the potential health risks associated with airborne 6-PPD exposure and emphasize the importance of further research into the respiratory toxicity of 6-PPD derivatives.

Mechanistic links between physiology and spectral reflectance enable previsual detection of oak wilt and drought stress

Tree mortality due to global change-including range expansion of invasive pests and pathogens-is a paramount threat to forest ecosystems. Oak forests are among the most prevalent and valuable ecosystems both ecologically and economically in the United States. There is increasing interest in monitoring oak decline and death due to both drought and the oak wilt pathogen (Bretziella fagacearum). We combined anatomical and ecophysiological measurements with spectroscopy at leaf, canopy, and airborne levels to enable differentiation of oak wilt and drought, and detection prior to visible symptom appearance. We performed an outdoor potted experiment with Quercus rubra saplings subjected to drought stress and/or artificially inoculated with the pathogen. Models developed from spectral reflectance accurately predicted ecophysiological indicators of oak wilt and drought decline in both potted and field experiments with naturally grown saplings. Both oak wilt and drought resulted in blocked water transport through xylem conduits. However, oak wilt impaired conduits in localized regions of the xylem due to formation of tyloses instead of emboli. The localized tylose formation resulted in more variable canopy photosynthesis and water content in diseased trees than drought-stressed ones. Reflectance signatures of plant photosynthesis, water content, and cellular damage detected oak wilt and drought 12 d before visual symptoms appeared. Our results show that leaf spectral reflectance models predict ecophysiological processes relevant to detection and differentiation of disease and drought. Coupling spectral models that detect physiological change with spatial information enhances capacity to differentiate plant stress types such as oak wilt and drought.

The clinical and environmental effects of an advanced air purification technology in multiple healthcare settings

Many facility acquired infection (FAI) causing pathogens are airborne and controlling them is critical to preventing illness. An advanced air purification technology (AAPT) was designed to inactivate the genetic material of pathogens and remediate volatile organic compounds (VOCs). This study explores the effect of the AAPT on critical metrics in multiple healthcare settings. The AAPT was installed in the heating, ventilation, and air conditioning (HVAC) ductwork of a hospital’s medical surgical floor (ACH-MSF), a second hospital’s post-anesthesia care unit (PACU), intensive care unit (ICU), and medical surgical (MS) unit, and in a senior living facility’s (SLF) memory support unit. In all installations, the control area(s) were protected only by high efficiency particulate air (HEPA) filtration. The measured airborne fungal levels, airborne and surface bacterial levels, and VOC levels decreased with the installation of AAPT. The AAPT removed infectious airborne pathogens and reduced surface pathogens and VOCs. The ACH-MSF and SLF protected by the AAPT documented improved clinical and economic metrics including a 39.5% decrease in patient length of stay, 23% in cost savings improvement, and a 39.6% decrease in FAIs. The current findings support the hypothesis that indoor environmental quality impacts wellness and has potential applications in diverse indoor environments.

Enhancing Solar-Induced Fluorescence Interpretation: Quantifying Fractional Sunlit Vegetation Cover Using Linear Spectral Unmixing

Solar-induced chlorophyll fluorescence (SIF) is closely related to plant photosynthetic activity and has been used in different studies as a proxy for vegetation health status. However, in order to use SIF as a relevant indicator of plant physiological stress, it is necessary to accurately quantify the amount of light absorbed by the photosynthetic plant pigments, called the absorbed photosynthetically active radiation (APAR). The ratio between fluorescence emission and light absorption (i.e., SIF and APAR) is known as the fluorescence quantum efficiency (FQE). In this work, simultaneous measurements of SIF and reflected radiance were performed both at the leaf and canopy levels for Salvia farinacea and Datura stramonium plants. With the aim of disentangling the proportion of sunlit and shaded absorbed PAR, an ad hoc experimental setup was designed to provide a wide range of fraction vegetation cover (FVC) canopy settings. A linear spectral unmixing method was proposed to estimate the contribution of soil, sunlit, and shaded vegetation from the total reflectance spectrum measured at the canopy level. Later, the retrieved sunlit FVC (FVCsunlit) was used to estimate the (dominant) green APAR flux, and this was combined with the integral of the spectrally resolved fluorescence to calculate the FQE. The results of this study demonstrated that under no-stress conditions and independently of the FVC, similar FQE values were observed when SIF was properly normalised by the green APAR flux. The results obtained showed that the reflectance spectra retrieved using a linear unmixing method had a maximum RMSE of less than 0.03 along the spectrum. The FVCsunlit evaluation showed an RMSE of 14% with an R2 of 0.84. Moreover, the FQE values obtained at the top of the canopy (TOC) were found statistically comparable to the reference values at the leaf level. These results support further efforts to improve the interpretation of fluorescence based on field spectroscopy and the further upscaling to imaging spectroscopy at airborne and satellite levels.

The contribution of aphids (Aphidoidea) to atmospheric concentrations of Alternaria and Cladosporium spores

Honeydew extracted by aphids serves as nutrient for the development of sooty moulds. Hypothetically, population dynamics of aphids should therefore have an effect on the airborne levels of the spores of fungi colonizing honeydew. In this study, the effects of seven aphid taxa on Alternaria and Cladosporium spore seasons (both pathogenic and allergenic fungi) were analysed on a total of 20-year-long dataset in Kecskemét (Hungary), Leicester (UK) and Poznań (Poland). Meteorological factors strongly effected both aphid and fungal populations. In most cases, a direct effect of weather on fungal levels were found. Direct effect of two aphid species, Acyrthosiphon pisum and Euceraphis punctipennis, on the atmospheric concentration of Alternaria spores was identified in Leicester and Poznań in June and July respectively. Other aphid species had secondary, but significant effects during other time periods. This suggests aphid population data can be informative in predicting airborne concentrations of Alternaria and Cladosporium spores.Graphical abstract

Update of Ambient Air Pollution Monitoring Programs within Regional-Level Implementation of National Projects

Introduction: The Federal Clean Air Project has been developed and is now implemented with the purpose of improving both ambient air quality and the quality of life of the population in 12 pilot cities, including Bratsk. An adequate air pollution control program, priority pollutant monitoring, and health risk management can facilitate improvement of the quality of human life and achievement of the targets of government projects. Objective: To update and streamline the ambient air quality monitoring program in Bratsk within implementation of national and federal projects at the regional level. Materials and methods: The updated air quality control program in Bratsk was based on the results of dispersion modeling verified by instrumental measurements of 34 pollutants at five monitoring stations of the Federal Service for Hydrometeorology and Environmental Monitoring (Roshydromet) and three stations of the Federal Service for Surveillance on Consumer Rights Protection and Human Wellbeing (Rospotrebnadzor). The consolidated database included 2,202 sources emitting 112 chemicals, with total emissions approaching 127,207 tons per year. Hygienic analysis and health risk assessment were performed according to conventional procedures. Results: We established that airborne levels of 29 pollutants exceeded their maximum allowable concentrations (MAC), i.e. were up to 7.0 times higher than short-term MAC, 13.8 and 60 times higher than the average daily and annual MAC, respectively. We also found that 19 air contaminants posed unacceptable health risks for the local population (CR up to 1.82×10–3, HQac up to 113.2, HQcr up to 211.1). Cluster analysis of the results of health risk assessment allowed us to distinguish three clusters within the urban area. We substantiated cutting down the number of monitoring stations to one and its optimal location in Cluster 1, the expediency of moving the station in Cluster 2 and adding a station in Cluster 3 at the point of concern. Optimization of the air quality control program involves reducing the number of monitored pollutants to 8–15 chemicals that are not covered by Roshydromet air monitoring plan. Conclusions: Given the changing sanitary and epidemiological situation, streamlining of air quality monitoring programs will provide relevant and timely information, thus contributing to elaboration of effective health risk management activities.

BTEX and PAH contributions to Lake Kinneret water: a seasonal-based study of volatile and semi-volatile anthropogenic pollutants in freshwater sources.

Benzene , toluene, ethylbenzene, and xylenes (BTEX) BTEX molecules are toxic components, ubiquitous in the environment, often found in concentrations- a few orders of magnitude higher than the well-studied PAHs levels. This fact is demonstrated in either crude oil, fuels, water, and air samples. BTEX studies focus mainly on the airborne levels of these molecules, while their waterborne presence is understudied. In this study, BTEX levels were assessed at Lake Kinneret, Israel. As a result, 0-1.5ppb of BTEX was recorded in five stations (2021-2022). Elevated BTEX levels (3-10ppb) were recorded at the northern rivers nourishing this lake, implying the existence of remote polluting sources. Transect air samplings of BTEX conducted at the lake next to the bathing season of 2021 revealed airborne BTEX levels between 0.8 and 10µg/m3, peaking up close to the bathing season, yet inconsistent with the BTEX water level trend. Lake water samples collected next to Tiberias city outfalls following the "Carmel" rainstorm showed elevated concentrations of BTEX up to 35ppb and PAHs up to 0.47ppb with an urban isotopic signal. The remote station's PAHs levels were less than one order of magnitude, with a distinct rural isotopic signal. Additionally, a human-specific microbial marker revealed increased sewer contributions at some of theurbansites. The results of this study show that a wide area dispersion of low atmospheric BTEX levels exists in the lake's perimeter. The dispersion rate is most likely influenced by season-based factors, e.g., motors and biomass fires. The unstudied waterborneBTEX levels in this lake are influenced by rivers, city runoff, and other yet unknown factors that may contribute to the sedimentation of these components. This process may result in a chronic pollution state. Despite the BTEX's medium-low solubility and high volatility, its under-evaluated waterborne transportation may lead to high toxic levels following bioaccumulation.

Airborne levels of cadmium are correlated with urinary cadmium concentrations among young children living in the New York state city of Syracuse, USA

Air pollution is a serious public health issue with early childhood exposure being of high concern because of the greater risk that children might experience negative health outcomes. Industrial sources in and near communities are one potential path of exposure that children might face with greater levels of air pollution correlating with higher levels of toxicants detected in children. We compare estimated ambient air concentrations of Cadmium (Cd) to a cohort (n = 281) of 9 to 11-year old children during their early childhood years (0–5 years of age) in a mid-size city in Upstate New York. Levels of Cd air pollution are compared to children's urine-Cd levels. Urine has been shown to be a superior biomarker to blood for Cd exposure particularly for longer-term exposures. We find that participants who reside in households that faced greater Cd air pollution during the child's early years have higher urine-Cd levels. This association is stable and stronger than previously presented associations for blood-Cd. Findings support expanded use of air modelling data for risk screening to reduce the potential health burden that industrial pollution can have.

Traffic-Related Air Pollution and Ground-Level Ozone Associated Global DNA Hypomethylation and Bulky DNA Adduct Formation.

Studies have indicated that air pollution, including surface-level ozone (O3), can significantly influence the risk of chronic diseases. To better understand the carcinogenic mechanisms of air pollutants and identify predictive disease biomarkers, we examined the association between traffic-related pollutants with DNA methylation alterations and bulky DNA adducts, two biomarkers of carcinogen exposure and cancer risk, in the peripheral blood of 140 volunteers-95 traffic police officers, and 45 unexposed subjects. The DNA methylation and adduct measurements were performed by bisulfite-PCR and pyrosequencing and 32P-postlabeling assay. Airborne levels of benzo(a)pyrene [B(a)P], carbon monoxide, and tropospheric O3 were determined by personal exposure biomonitoring or by fixed monitoring stations. Overall, air pollution exposure was associated with a significant reduction (1.41 units) in global DNA methylation (95% C.I. -2.65-0.04, p = 0.026). The decrement in ALU repetitive elements was greatest in the policemen working downtown (95% C.I. -3.23--0.49, p = 0.008). The DNA adducts were found to be significantly increased (0.45 units) in the municipal officers with respect to unexposed subjects (95% C.I. 0.02-0.88, p = 0.039), mainly in those who were controlling traffic in downtown areas (95% C.I. 0.39-1.29, p < 0.001). Regression models indicated an increment of ALU methylation at higher B(a)P concentrations (95% C.I. 0.03-0.60, p = 0.032). Moreover, statistical models showed a decrement in ALU methylation and an increment of DNA damage only above the cut-off value of 30 µg/m3 O3. A significant increment of 0.73 units of IL-6 gene methylation was also found in smokers with respect to non-smokers. Our results highlighted the role of air pollution on epigenetic alterations and genotoxic effects, especially above the target value of 30 µg/m3 surface-level O3, supporting the necessity for developing public health strategies aimed to reduce traffic-related air pollution molecular alterations.

Proven Impact of an Advanced Air Purification System in the Reduction of Infectious Airborne and Surface Pathogens, Concomitant Reduction of Hospital-acquired Infections and Length of Stay, and Improvement in Health-care Economics.

Proven Impact of an Advanced Air Purification System in the Reduction of Infectious Airborne and Surface Pathogens, Concomitant Reduction of Hospital-acquired Infections and Length of Stay, and Improvement in Health-care Economics.

Particulate-Bound Polycyclic Aromatic Hydrocarbons (PAHs) and their Nitro- and Oxy-Derivative Compounds Collected Inside and Outside Occupied Homes in Southern Sweden

This study presents indoor and outdoor levels of airborne fine particles (PM2.5), particle bound polycyclic aromatic compounds (PACs) including parent-, alkylated-, nitro-, and oxy-PAHs. Week-long simultaneous measurements were conducted inside and outside 15 occupied homes in southern Sweden during wintertime. The homes were single-family houses or apartments located in urban, semi-urban, and rural areas. The PM2.5 and PACs levels were low compared to studies worldwide. There was great variation in concentrations between sites, which likely is due to proximity to road and traffic intensity. The lower concentrations of nitro and oxy-PAHs compared to parent PAHs in this study, compared to other studies, could possibly be due to lower atmospheric photochemical formation outdoors because the cold climate. This assumption could not be confirmed and need to be further tested. The results point to that particle PAC levels found inside arise primarily from outdoor. This correlation was not as clear for PM2.5. The results of a comparison between residences before and after energy renovation did not indicate an improvement in indoor air regarding PACs. To understand exposure and assess risks it is important to measure wide range of PACs both in gas and particle phase.

Assessment of the Effectiveness of Ventilation Controls in Managing Airborne and Surface Lead Levels at a Newly Commissioned Indoor Shooting Range.

Lead levels at a new indoor target shooting range were assessed using both personal and environmental air monitoring methods. Surface swabs were collected from representative locations throughout the range prior to, and at the conclusion of, shooting. Personal samples were compared against the current Australian Workplace Exposure Standards with all results exceeding statutory limits. Static environmental samples exceeded the Air National Environmental Protection Measures (NEPM) air quality standard. Surface swabs showed significant increases from pre- to post-shooting with levels exceeding recommended limits. The performance of the mechanical ventilation system was also assessed and airflow levels were below the required rate at all test locations when compared against the values recommended by the National Institute for Occupational Safety and Health (NIOSH). Users of the indoor shooting range are at risk of potential exposure to hazardous levels of lead. It was recommended the ventilation system be reviewed by a suitably qualified ventilation engineer to ensure it is operating within the required parameters and able to transport generated lead contaminant away from the shooters breathing zone. A thorough cleaning regime should be implemented by the club to minimise surface lead loadings throughout the facility.

Release of VOCs, Gasses, and Bacteria from Contaminated Landings and Creeks of Ogeechee River Basin.

River landings are common public grounds, visited by many people every day. The aftermath of visiting these places may be unsettling since much trash is left behind and scattered throughout. The litter collects and with each rain or high wind, it has a better chance of ending up in our streams, rivers, creeks, and eventually our oceans. The main purpose of this study was to measure both air and water quality throughout the Ogeechee River basin in South Georgia to determine how each was impacted by trash. Ammonia, methane, and volatile organic compounds (VOCs) along with temperature and humidity were also measured for air quality. Water quality parameters for this study were derived from the Georgia Adopt-A-Stream method. Conductivity, dissolved oxygen, pH, water temperature, and Escherichia coli counts were taken every two weeks at three locations: Rocky Ford Landing along the Ogeechee River, Rocks River Landing on the Canoochee River, and Little Lotts Creek located in the center of Statesboro, Georgia. Each Monday, from 17 January 2022 to 17 May 2022, selected air pollutants were sampled ten times at each location. The data show higher trends in air and water pollution where trash is found—the highest with Rocks River Landing and Little Lotts Creek showing trends supporting the hypothesis that trash may impact air and water quality in these areas. The potential contamination of river landings and creeks may contribute to increased levels of airborne and waterborne gas levels and microbial loads near the river water surfaces.

Exposure to organophosphorus compounds of Japanese children and the indoor air quality in their residences

Several organophosphorus compounds such as organophosphate pesticides (OPPs) and trialkylphosphates (TAPs) are suspected to inhibit cholinesterase activities, to affect endocrine systems or to possibly be carcinogenic. To evaluate their adverse effects on health with chronic exposure in the general population, especially in children, we measured the household exposure to OPPs and TAPs by Japanese children via all exposure pathways and the contribution of indoor air quality. First-morning void urine was collected from subjects aged 6 to 15 years (n = 132), and airborne organophosphorus compounds were sampled in the subject's bedroom for 24 h. Airborne levels of nine OPPs and three TAPs and their urinary metabolites were determined.No significant correlations were detected for any compounds between their airborne concentrations and the urinary excretion amounts of their corresponding metabolites. The estimated daily intakes were as follows (median, μg/kg b.w./d): chlorpyrifos, 0.042; diazinon, 0.067; tri-n-butylphosphate, 0.094. The 95th percentiles of the intakes for fenthion, fenitrothion and the above three compounds did not exceed their reference limit values, although one subject had a daily intake of tri-n-butylphosphate that was about twice its reference limit value. The concentration levels of the urinary metabolite of tri-n-butylphosphate in our subjects tended to be higher than those for children in many other countries. The fractions of the amounts absorbed by inhalation to the amounts absorbed via all of the exposure pathways was only 2.3 % (median) for tri-n-butylphosphate.Inhalation did not seem to contribute very much as an absorption pathway of the organophosphorus compounds in these Japanese children while they were at home. The exposure amounts of OPPs were not suggested to be high enough to adversely affect the health of these children at present on the basis of their daily intakes compared to their reference limit values.

Assessment of personal inhalation and skin exposures to polymeric methylene diphenyl diisocyanate during polyurethane fabric coating.

Methylene diphenyl diisocyanate (MDI) monomers and polymeric MDI (pMDI) are aromatic isocyanates widely used in the production of polyurethanes. These isocyanates can cause occupational asthma, hypersensitivity pneumonitis, as well as contact dermatitis. Skin exposure likely contributes toward initial sensitization but is challenging to monitor and quantitate. In this work, we characterized workers' personal inhalation and skin exposures to pMDI in a polyurethane fabric coating factory for subsequent health effect studies. Full-shift personal and area air samples were collected from eleven workers in representative job areas daily for 1-2weeks. Skin exposure to hands was evaluated concomitantly with a newly developed reagent-impregnated cotton glove dosimeter. Samples were analyzed for pMDI by liquid chromatography-tandem mass spectrometry. In personal airborne samples, the concentration of 4,4'-MDI isomer, expressed as total NCO, had a geometric mean (GM) and geometric standard deviation (GSD) of 5.1 and 3.3ng NCO/m3, respectively (range: 0.5-1862ng NCO/m3). Other MDI isomers were found at much lower concentrations. Analysis of 4,4'-MDI in the glove dosimeters exhibited much greater exposures (GM: 10ng/cm2) and substantial variability (GSD: 20ng NCO/cm2; range: 0-295ng NCO/cm2). MDI inhalation exposure was well below occupational limits for MDI for all the job areas. However, MDI skin exposure to hands was substantial. These findings demonstrated the potential for substantial isocyanate skin exposure in work settings with very low airborne levels. This exposure characterization should inform future studies that aim to assess the health effects of work exposures to MDI and the effectiveness of protective measures.

The Positive Impact of a Novel Air Purification Technology on Environmental and Clinical Outcomes

Reducing sources of illness improves resident care. An advanced air purification technology (AAPT) was designed to destroy the DNA and RNA of all bacteria, fungi and viruses, rendering them non-infectious and to remediate volatile organic compounds (VOCs). This study compares the biological, fungal and VOC loading using the AAPT to standard high efficiency particulate air (HEPA) filtration. It was hypothesized that the AAPT would be associated with reductions in airborne and surface pathogens, VOCs and improved clinical metrics. A control floor with HEPA filtration and study floor with AAPT remediation were studied. Measurements of total VOCs and airborne and surface bacteria and fungi were measured in five locations on each floor. The facility acquired infection (FAI) rate, the number of infections divided by total patient days, showed a 57% difference between the control floor (2.33 FAIs/month) and the study floor (1.00 FAIs/month) and a decrease of 39.75% pre-installation (1.66 FAIs/month) to post-installation (1.00 FAIs/month). The viable pathogen loading measured on the study floor was reduced from an average of 483.8 colony forming units (CFU)/m3 pre-installation to an average of 56 CFU/m3 post-installation. VOCs were reduced from an average of 641.66 parts per billion (PPB) to 64.96 PPB and viable surface bacteria from an average of 110.6 CFU/m3 to 97.2 CFU/m3. The AAPT significantly reduced levels of infectious airborne and surface pathogens and VOC levels. As a result, residents on the AAPT floor demonstrated significant improvements in FAI rates. The findings support the hypothesis that environmental factors impact resident wellness.

Consistency between air and biological monitoring for assessing polycyclic aromatic hydrocarbon exposure and cancer risk of workers

BackgroundAtmospheric levels of polycyclic aromatic hydrocarbons (PAHs) have been monitored in many companies since 1940. Because of the use of respiratory protective equipment (RPE) and cutaneous absorption, the measurement of urinary 1-hydroxypyrene (1-OHP), metabolite of pyrene (Pyr), and, more recently, 3-hydroxybenzo[a]pyrene (3-OHBaP), metabolite of benzo[a]pyrene (BaP), has been carried out to assess PAH exposure and estimate health risks. ObjectivesThis study aimed to investigate the agreement between 523 air and biological levels recorded in the Exporisq-HAP database by taking into account the effectiveness of RPE. MethodsThe agreement/consistency between 523 air and biological exposure levels was assessed by estimating and comparing the probability of exceeding French limit values (LVs) for both BaP and 3-OHBaP and ACGIH LV for 1-OHP, respectively. PAH airborne levels (wPAHs) were weighted by an assigned protection factor (APF) depending on the type of mask worn by workers, while urinary 1-OHP concentrations were adjusted with the wBaP/wPyr ratio of each industrial sector (wadj1-OHP). ResultsWithin occupational groups, there was an overall agreement between airborne PAH levels and urinary biomarker concentrations. A clear dichotomy was found between “petroleum-derived” and “coal-derived” groups, with much higher exposures in the latest group despite the use of RPEs by two-thirds of the workers. The type of RPE varied from one plant to another, which underlines the importance of taking into account their effectiveness. The analysis of urinary 3-OHBaP was not relevant for low PAH exposure levels. In addition, this biomarker underdiagnosed the exceedance of LV relative to BaP levels for 6% of “coal-derived” groups. ConclusionsThe use of urinary wadj1-OHP seemed to be more protective to assess the exceedance of LVs than those of urinary 3-OHBaP and air wBaP, but adjustment of the 1-OHP concentration by the BaP/Pyr ratio requires air sampling due to highly variable ratios observed in the studied occupational groups.

Relating air quality and other factors to comfort and health related symptoms reported by passengers and crew on commercial transport aircraft (ASHRAE RP-1262)

Passenger and flight crew concerns over the negative impact of the aircraft cabin environment on health and comfort have lingered for years. During flight, passengers and crew can experience reduced atmospheric pressure, low relative humidity, and potential air quality degradation, which could lead to adverse health complaints. The goal of this project was to investigate the potential link between perceived health symptoms and discomfort and aircraft cabin environmental conditions and human factors. Passengers and crew completed validated health and comfort surveys on 130 domestic and international flights across varied aircraft, durations, and seasons. Environmental conditions and airborne levels of contaminants were measured during 80 of these flights. Extremes in cabin temperature or degraded air quality parameters led to higher rates of passenger discomfort. Odds ratios were higher for several adverse health symptoms for certain aircraft types and durations, while ventilation rates were positively correlated with discomfort and adverse health symptoms. Median levels of CO, CO2, and ozone were below established exposure limits. Results from this study help further our knowledge of aircraft comfort and can help airlines and industry agencies determine the most critical impacts on health and comfort to better inform standards to improve passenger and crew experiences.

Estimating the impact of indoor relative humidity on SARS-CoV-2 airborne transmission risk using a new modification of the Wells-Riley model

A novel modified version of the Wells-Riley model was used to estimate the impact of relative humidity (RH) on the removal of respiratory droplets containing the SARS-CoV-2 virus by deposition through gravitational settling and its inactivation by biological decay; the effect of RH on susceptibility to SARS-CoV-2 was not considered. These effects were compared with the removal achieved by increased ventilation rate with outdoor air. Modeling was performed assuming that the infected person talked continuously for 60 and 120 min. The results of modeling showed that the relative impact of RH on the infection risk depended on the ventilation rate and the size range of virus-laden droplets. A ventilation rate of 0.5 ACH, the change of RH between 20% and 53% was predicted to have a small effect on the infection risk, while at a ventilation rate of 6 ACH this change had nearly no effect. On the contrary, increasing the ventilation rate from 0.5 ACH to 6 ACH was predicted to decrease the infection risk by half which is remarkably larger effect compared with that predicted for RH. It is thus concluded that increasing the ventilation rate is more beneficial for reducing the airborne levels of SARS-CoV-2 than changing indoor RH. Practical implicationsThe present results show that humidification to moderate levels of 40%–60% RH should not be expected to provide a significant reduction in infection risk caused by SARS-CoV-2, hence installing and running humidifiers may not be an efficient solution to reduce the risk of COVID-19 disease in indoor spaces. The results do however confirm that ventilation has a key role in controlling SARS-CoV-2 virus concentration in the air providing considerably higher benefits. The modified model developed in the present work can be used by public health experts, engineers, and epidemiologists when selecting different measures to reduce the infection risk from SARS-CoV-2 indoors allowing informed decisions concerning indoor environmental control.

Hemoglobin adducts as an important marker of chronic exposure to low concentration of 1, 3-butadiene.

1, 3-Butadiene is a famous industrial compound which occurs in gasoline and diesel exhaust and in cigarette smoke. Based on little evidence of carcinogenicity in laboratory animals and humans, it was classified as a probable carcinogen. The potential of exposure to gasoline and diesel exhaust containing these chemical compounds is very considerable in urban areas. According to studies, in estimation of workers' chronic exposure with biological samples, analysis of the concentration of related hemoglobin adducts seems to give the most valid estimation of exposure. This study designed to determine the level of chronic exposure in gas station workers and traffic policemen during routine work shift, by an appropriate biological marker. In this regards, 25 gas station workers, 25 policemen engaged in traffic control, and 25 occupationally non-exposed persons were studied. Blood samples were obtained after the work shift from each person. The level of selected hemoglobin adduct, 1- and 2-hydroxy-3-butenyl valine (MHBVal) was determined by using GC-MS after a modified Edman degradation and a further acetylation. There were significant differences among the mean concentrations of MHBVal in blood samples of gas station workers, policemen and occupationally non-exposed persons. The mean airborne levels of 1, 3-Butadiene over 60days, differed significantly among different studied groups (ANOVA: p< 0.05 and Kruskal-Wallis test: p < 0.05). There was a significant difference in MHBVal concentrations between job categories (p< 0.05 by ANOVA and Kruskal-Wallis test), and gas station workers and policemen were found to be probably the most exposed groups in this research.