Particles formed from the squalene-ozone (SqOz) reaction have potential health concerns. Squalene, a component of skin oil, is ubiquitously found indoors on skin, surfaces, and clothing. Since people spend the majority of their time indoors, it is important to understand how indoor relative humidity (RH), ozone concentrations, and squalene loadings affect SqOz particle formation. Particle formation from the SqOz reaction within a reaction chamber was monitored using a condensation particle counter (CPC) while varying environmental conditions. The particle production curves over time were similar as RH was varied from 15% to 45%, but particles were not formed at RH 55% and 65%, probably due to a shift in primary formation pathway towards volatile products and/or potential losses of volatile compounds from particles produced as secondary reaction products. As ozone concentrations were increased from 25 ppb to 200 ppb, the time to maximum particle number concentration decreased, and the maximum particle number concentration and initial rate of particle generation increased non-linearly. This suggests that particle formation was dependent upon the ozone concentration but was limited by the amount of squalene remaining on the surface. As surface loadings were raised from 1.28 mu g/cm(2) to 270 mu g/cm(2) the maximum particle number concentration increased linearly. Further increases in squalene loading did not cause higher levels of particle production. This pattern is consistent with a shift from a monolayer to bi-layer formation or non-reactive products coating the squalene at the higher loadings. Our results indicate that SqOz particle formation is a function of environmental conditions.

This critical review describes the squalene-ozone (SqOz) reaction, or squalene ozonolysis. Ambient ozone penetrates indoors and drives indoor air chemistry. Squalene, a component of human skin oil, contains six carbon-carbon double bonds and is very reactive with ozone. Bioeffluents from people contribute to indoor air chemistry and affect the indoor air quality, resulting in exposures because people spend the majority of their time indoors. The SqOz reaction proceeds through various formation pathways and produces compounds that include aldehydes, ketones, carboxylic acids, and dicarbonyl species, which have a range of volatilities. In this critical review of SqOz chemistry, information on the mechanism of reaction, reaction probability, rate constants, and reaction kinetics are compiled. Characterizations of SqOz reaction products have been done in laboratory experiments and real-world settings. The effect of multiple environmental parameters (ozone concentration, air exchange rate (AER), temperature, and relative humidity (RH)) in indoor settings are summarized. This critical review concludes by identifying the paucity of available exposure, health, and toxicological data for known reaction products. Key knowledge gaps about SqOz reactions leading to indoor exposures and adverse health outcomes are provided as well as an outlook on where the field is headed.

In this work, we studied several important parameters regarding the standardization of a portable sensor of nitrite, a key biomarker of inflammation in the respiratory tract in untreated EBC samples. The storage of the EBC samples and electrical properties of both EBC samples and the sensor as main standardization parameters were investigated. The sensor performance was performed using differential pulse voltammetry (DPV) in a standard nitrite solution and untreated EBC samples. The storage effect was monitored by comparing sensor data of fresh and stored samples for one month at -80 °C. Results show, on average, a 20 percent reduction of peak current for stored solutions. The sensor's performance was compared with a previous EBC nitrite sensor and chemiluminescence method. The results demonstrate a good correlation between the present sensor and chemiluminescence for low nitrite concentrations in untreated EBC samples. The electrical behavior of the sensor and electrical variation between EBC samples were characterized using methods such as noise analysis, electrochemical impedance spectroscopy (EIS), electrical impedance (EI), and voltage shift. Data show that reduced graphene oxide (rGO) has lower electrical noise and a higher electron transfer rate regarding nitrite detection. Also, a voltage shift can be applied to calibrate the data based on the electrical variation between different EBC samples. This result makes it easy to calibrate the electrical difference between EBC samples and have a more reproducible portable chip design without using bulky EI instruments. This work helps detect nitrite in untreated and pure EBC samples and evaluates critical analytical EBC properties essential for developing portable and on-site point-of-care sensors.

Exposure to indoor air contaminants occurs not just through inhalation but also via dermal absorption of vapors or when touching surfaces that air contaminants deposit on, and by inadvertent ingestion of contaminated settled dust from hand to mouth behaviors, especially for children. Sources of indoor pollutants include penetration of outdoor air, emissions from indoor use of consumer and personal products, furnishing and building materials, resuspension of house dust, and indoor air chemistry. Multiple sources, limited ventilation, and finite volume of buildings results in higher air concentrations of many volatile and semi-volatile organic compounds within homes than outdoors. When personal products are used near the breathing zone, the concentration of the air breathed, and therefore the resulting inhalation exposure, can be higher than estimated from the indoor air concentrations. Semi-volatile organic compounds (SVOCs) partition between indoor air and surfaces, particularly into house dust which serves as a reservoir for many compounds. The partitioning of SVOCs between indoor air and surface/dust results in their having multiple exposure routes. This chapter presents examples of exposures that occur to various chemicals representative of broad categories of compounds, thereby providing general concepts that should be considered when evaluating potential exposures to indoor air pollutants. Since people spend, on average, more than 90% of their time indoors, indoor air is often the largest contributor to total exposures for volatile, semi-volatile, and particulate air contaminants.

Elevated perfluorononanoic acid (PFNA) levels, one of many manmade per- and polyfluoroalkyl substances (PFAS), were detected in public water systems/private wells in New Jersey communities. Interventions to end exposure through drinking water were carried out from 2014 to 2016. To evaluate the effectiveness of interventions, a community biomonitoring study was conducted for the communities between 2017 and 2020. A convenience sampling design was used with 120 participants in Year 1 between ages of 20-74 who consumed PFNA-contaminated water. Three blood samples, one year apart, were drawn from each participant and completed for 99 participants. Separated serum samples were measured for 12 PFAS including PFNA. Questionnaires were administered to collect information on demographics and potential sources. Drinking water and house dust collected at the first visit were analyzed for 14 PFAS including PFNA. The PFNA sera levels (Year 1) found 84 out of 120 (70%) participants were higher than the 95th percentile of a nationally representative sample of US adults (NHANES2015-16). Current drinking water and house dust were not significant contributing sources for the study participants. On average, PFNA sera levels were 12 ± 16% (Year 2) and 27 ± 16% (Year 3) lower than the level measured in Year 1 (p < 0.01). The PFNA half-life was estimated around 3.52 years, using a mixed model from 68 high-exposed participants (>95th percentile of NHANES2015-16) with controlling for physiological covariates. The decline in adult serum PFNA levels seen in the years following a community drinking water intervention suggests the intervention effectively reduced PFNA exposure via drinking water.

COVID-19 created an unprecedented global public health crisis during 2020–2021. The severity of the fast-spreading infection, combined with uncertainties regarding the physical and biological processes affecting transmission of SARS-CoV-2, posed enormous challenges to healthcare systems. Pandemic dynamics exhibited complex spatial heterogeneities across multiple scales, as local demographic, socioeconomic, behavioral and environmental factors were modulating population exposures and susceptibilities. Before effective pharmacological interventions became available, controlling exposures to SARS-CoV-2 was the only public health option for mitigating the disease; therefore, models quantifying the impacts of heterogeneities and alternative exposure interventions on COVID-19 outcomes became essential tools informing policy development. This study used a stochastic SEIR framework, modeling each of the 21 New Jersey counties, to capture important heterogeneities of COVID-19 outcomes across the State. The models were calibrated using confirmed daily deaths and SQMC optimization and subsequently applied in predictive and exploratory modes. The predictions achieved good agreement between modeled and reported death data; counterfactual analysis was performed to assess the effectiveness of layered interventions on reducing exposures to SARS-CoV-2 and thereby fatality of COVID-19. The modeling analysis of the reduction in exposures to SARS-CoV-2 achieved through concurrent social distancing and face-mask wearing estimated that 357 [IQR (290, 429)] deaths per 100,000 people were averted.

Health impacts of electronic cigarette (e-cigarette) vaping are associated with the harmful chemicals emitted from e-cigarettes such as carbonyls. However, the levels of various carbonyl compounds under real-world vaping conditions have been understudied. This study evaluated the levels of carbonyl compounds (e.g., formaldehyde, acetaldehyde, glyoxal, and diacetyl, etc.) under various device settings (i.e., power output), vaping topographies, and e-liquid compositions (i.e., base liquid, flavor types). The results showed that e-vapor carbonyl levels were the highest under higher power outputs. The propylene glycol (PG)-based e-liquids generated higher formaldehyde and acetaldehyde than vegetable glycerin (VG)-based e-liquids. In addition, fruit flavored e-liquids (i.e., strawberry and dragon fruit) generated higher formaldehyde emissions than mint/menthol and creamy/sweet flavored e-liquids. While single-top coils formed 3.5-fold more formaldehyde per puff than conventional cigarette smoking, bottom coils generated 10–10,000 times less formaldehyde per puff. In general, increases in puff volume and longer puff durations generated significantly higher amounts of formaldehyde. While e-cigarettes emitted much lower levels of carbonyl compounds compared to conventional cigarettes, the presence of several toxic carbonyl compounds in e-cigarette vapor may still pose potential health risks for users without smoking history, including youth. Therefore, the public health administrations need to consider the vaping conditions which generated higher carbonyls, such as higher power output with PG e-liquid, when developing e-cigarette product standards.

Exposure to contaminants in drinking water occurs not only via ingestion but also via inhalation, when the contaminants volatilize or are aerosolized, and via dermal absorption from direct contact with the water. Showering not only results in a direct inhalation exposure to the individual showering while in the shower stall and in the bathroom while the shower water is running, but it also increases the air concentration throughout the home, causing exposure to others within the residence. This chapter discusses the major processes leading to inhalational aerosol exposure and summarizes the little available information about showering and use of humidifiers. It considers droplet size distributions reported in the literature as a background for later sections on settling and evaporation. The chapter provides an overview of the modeling topics and concepts that should be considered when conducting a model-based exposure assessment.

Changes to human respiratory tract microbiome may contribute significantly to the progression of respiratory diseases. However, there are few studies examining the relative abundance of microbial communities at the species level along the human respiratory tract. Bronchoalveolar lavage, throat swab, mouth rinse, and nasal swab samples were collected from 5 participants. Bacterial ribosomal operons were sequenced using the Oxford Nanopore MinION to determine the relative abundance of bacterial species in 4 compartments along the respiratory tract. More than 1.8 million raw operon reads were obtained from the participants with similar to 600,000 rRNA reads passing quality assurance/quality control (70-95% identify; > 1,200 bp alignment) by Discontiguous MegaBLAST against the EZ BioCloud 16S rRNA gene database. Nearly 3,600 bacterial species were detected overall (> 750 bacterial species within the 5 dominant phyla: Firmicutes, Proteobacteria, Actinobacteria, Bacteroidetes, and Fusobacteria. The relative abundance of bacterial species along the respiratory tract indicated that most microbes (95%) were being passively transported from outside into the lung. However, a small percentage (< 5%) of bacterial species were at higher abundance within the lavage samples. The most abundant lung-enriched bacterial species were Veillonella dispar and Veillonella atypica while the most abundant mouth-associated bacterial species were Streptococcus infantis and Streptococcus mitis. Most bacteria detected in lower respiratory samples do not seem to colonize the lung. However, > 100 bacterial species were found to be enriched in bronchoalveolar lavage samples (compared to mouth/nose) and may play a substantial role in lung health.

Obtaining valid, reliable quantitative exposure data can be a significant challenge for industrial hygienists, exposure scientists, and other health science professionals. In this proof-of-concept study, a robotic platform was programmed to perform a simple task as a plausible alternative to human subjects in exposure studies for generating exposure data. The use of robots offers several advantages over the use of humans. Research can be completed more efficiently and there is no need to recruit, screen, or train volunteers. In addition, robots can perform tasks repeatedly without getting tired allowing for collection of an unlimited number of measurements using different chemicals to assess exposure impacts from formulation changes and new product development. The use of robots also eliminates concerns with intentional human exposures while removing health research ethics review requirements which are time consuming. In this study, a humanoid robot was programmed to paint drywall, while volatile organic compounds were measured in air for comparison to model estimates. The measured air concentrations generally agreed with more advanced exposure model estimates. These findings suggest that robots have potential as a methodology for generating exposure measurements relevant to human activities, but without using human subjects.

Inhalation exposure increases the body burden of airborne pollutants. People spend 90% of their time indoors, so indoor air levels often drive exposures. The concentrations of many air pollutants indoors and in enclosed settings are often higher than outdoors since even small emissions within a limited volume can lead to elevated concentrations. Activities that people engage in and consumer product use can result in emission sources being in very close proximity to people contributing to the overall inhalation exposure. It is necessary to understand the time spent and the air concentrations in each microenvironment people encounter over the course of a day to determine inhalation exposures, and to develop a risk management plan to reduce those exposures. Both measurement and modeling approaches have incorporated a variety of exposure science principles to calculated inhalation exposures. As new products are brought into use it is important to recognize how they will actually be used and the resulting emissions that can lead to exposures and adverse health outcomes. Accurate determination inhalation exposure on an individual and population basis is a key component of environmental and occupational epidemiology studies as well as risk assessment and risk management applications done to protect public health.

Introduction Per and polyfluoroalkyl substances (PFAS), including perfluorononanoic acid (PFNA) and perfluorooctanoic acid (PFOA), were detected in the community water supply of Paulsboro New Jersey in 2009. Methods A cross-sectional study enrolled 192 claimants from a class-action lawsuit, not affiliated with this study, who had been awarded a blood test for 13 PFAS. Study participants provided their blood test results and completed a survey about demographics; 105 participants also completed a health survey. Geometric means, 25th, 50th, 75th, and 95th percentiles of exposure of PFNA blood serum concentrations were compared to that of the 2013-2014 NHANES, adjusted for reporting level. Associations between PFNA, PFOA, PFOS, and PFHxS and self-reported health outcomes were assessed using logistic regression. Results PFNA serum levels were 285% higher in Paulsboro compared with U.S. residents. PFNA serum levels were higher among older compared with younger, and male compared to female, Paulsboro residents. After adjustment for potential confounding, there was a significant association between increased serum PFNA levels and self-reported high cholesterol (OR: 1.15, 95% CI: 1.02, 1.29). Discussion/Conclusion Further investigation into possible health effects of PFAS exposure in Paulsboro and other community settings is warranted. Since exposure has ceased, toxicokinetics of PFAS elimination should be explored.

Accurate measurements of personal exposure to atmospheric pollutants such as ozone are important for understanding health risks. We tested a new personal ozone monitor (POM; 2B Technologies) for accuracy, precision, and ease of use. The POM's measurements were compared to simultaneous ozone measurements from a 2B Model 205 monitor and a ThermoScientific 49i monitor, and multiple POMs were placed side-by-side to check precision. Tests were undertaken in a controlled environmental facility, outdoors, and in a private residence. Additionally, ten volunteers wore a POM for five days and answered a questionnaire about its ease of use. The POM measured ozone accurately compared to the 49i ozone monitor, with average relative differences of less than 8%. In the controlled environment tests, the POM's ozone measurements did not change in the presence of additional atmospheric constituents with similar absorption lines to ozone, though there may have been a small decrease in precision and accuracy. Precision between POMs varied by environment (r2 = 0.98 outdoors; r2 = 0.3 to 0.9 in controlled lab conditions). Volunteers reported that the POM was reasonably comfortable to wear, although all reported that they felt that it was too noisy. Overall, the POM is a viable option for personal ozone monitoring.

Introduction: Perfluoronated chemicals (PFCs) are used in manufacturing stain resistant and water repellent consumer products and in firefighting foams at airports and military sites. They have been released into the environment inadvertently and when sprayed during firefighting scenarios and simulations. Due to their slow environmental degradation they have contaminated water supplies in multiple counties in the US potentially exposing more that 5 million people nationwide. The ground water in several communities in Gloucester County, NJ, particularly the municipal water in Paulsboro, was contaminated with perfluoro-n-nonanoic acid (PFNA) and perfluorooctoanic acid (PFOA). Since 2014, the water supplies have been filtered with activated charcoal. To assess the effectiveness of the water intervention program on reducing exposure to these PFCs, a convenience sample of 120 adult residents in the area have been recruited and twelve PFCs were measured in serum, household tap water, and household dust and a questionnaire administered as part of a CDC Biomonitoring grant.Results: The first visits have been completed and two more visits to each subject are planned approximately a year apart. Nine of the PFCs were routinely above the detection limits in the serum. The analyses of approximately half of the subjects have been completed, with the serum PFNA levels of the residents (5.9±9.5, median 3.3, maximum 60 µg/L) often exceeded the 95th% reported in the 2009-2010 NHANES levels for adults over 20 (3.94 (CI: 2.38-8.36)). The distribution of other PFCs serum levels were similar to that reported in NHANES. Water levels were below detection for all PFCs, indicative that the water intervention has effectively reduced the PFCs exposure through that route. PFCs were found in dust reflecting their use in consumer products. It is expected that the serum levels of PFNA will decline over the next few years if the drinking water was the main exposure source.

Humans are continuously exposed to ozone and its by-products through ambient ozone penetration indoors. Both volatile and particulate phase by-products have been found inside homes due to the reaction of ozone with highly reactive squalene, a natural component of skin oil. Particulate phase by-products may cause respiratory and ocular irritation due to their common chemical makeup consisting of carbonyls and organic acids. This work investigates the effect of varying concentrations of ozone, squalene, reaction duration, and humidity levels on both particle number generation and particle size. Squalene was loaded onto a surface at varying concentrations of 0.25-0.76 mg/cm2 and ozone was passed over the surface at concentrations between 100-700 ppb to initiate the reaction. Produced particles were analyzed with a TSI Condensation Particle Counter, a Grimm mini-WRAS aerosol spectrometer, and collected on Teflon filters for extraction and derivatization with BSTFA. Subsequent analysis and identification by GC-MS were conducted where succinic acid and levulinic acid were identified as the likely unique squalene-ozone reaction products, as well as nine other alcohols and carboxylic acids. Particles produced from pure squalene are compared to that of total skin oil and those found in an air sample collected from inside a home. Particles were found to form approximately one hour after the introduction of ozone and found to be related to the relative humidity, which is consistent with nucleation and condensation mechanisms. Given the aforementioned squalene and ozone concentrations, particle counts ranged from 200-6000 #/cc The presented work aims to investigate a reaction taking place on the surface of the skin and identify compounds people may be exposed to inside their home.

Application of pyrethroid insecticides in residential settings may result in children’s exposures to these chemicals and possible adverse health effects. Household dust is a recognized reservoir for pyrethroids and a potential medium for multi-route pyrethroid exposure. Young children move and play in a manner that resuspends dust, and since their breathing zone is close to the floor, they will have higher inhalation exposure to pesticide-laden dust than other age groups. Directly measuring a toddler’s exposure to household dust presents many logistic challenges. We simulated the dust resuspension induced by a toddler using a robot, which also served as a platform to collect air samples at the toddler’s breathing zone height. We performed simulated pyrethroid residential spray and dust resuspension experiments on vinyl and carpeted floors. The mean pyrethroid airborne concentrations in the stationary and mobile samples were 0.065 μg/m 3 and 0.143 μg/m 3 for the vinyl floor with 1 g/m 2 dust loading, and 0.034 μg/m 3 and 0.061 μg/m 3 for the carpeted floor with 10 g/m 2 dust loading, respectively. Pyrethroids concentrations in the settled dust samples were significantly lower than that measured in the stationary and mobile samples in the carpeted floor experiments. Thus, the use of stationary samples and settled dust samples may underestimate a toddler’s personal inhalation exposure to pyrethroids in residential houses.

Objective: The aim of this study was to assess the neurobehavioral effects of lifetime solvent exposure by comparing the performance of painters and demographically comparable controls. Methods: Performance of exposed painters (N = 133) was compared with unexposed tapers, glaziers, or carpenters (N = 78) on the following domains: motor/perceptual speed, visual contrast, attention, working memory/planning, and visual and verbal memory. Lifetime exposure was estimated with questionnaires, field measurements, and paint composition. Results: After controlling for confounders, lifetime solvent exposure did not predict reduction in performance for overall domains of function. Lifetime solvent exposures predicted subtle alterations for individual tests of verbal learning, motor coordination, and visuospatial accuracy. Conclusion: Concentrations of solvents in paints have steadily declined during the working lifetime of subjects in this study. Although reduced performance was observed on individual tests, these alterations were not consistent across tests and unlikely to be of clinical significance.

OBJECTIVE:The aim of this study was to assess the neurobehavioral effects of lifetime solvent exposure by comparing the performance of painters and demographically comparable controls.METHODS:Performance of exposed painters (N = 133) was compared with unexposed tapers, glaziers, or carpenters (N = 78) on the following domains: motor/perceptual speed, visual contrast, attention, working memory/planning, and visual and verbal memory. Lifetime exposure was estimated with questionnaires, field measurements, and paint composition.RESULTS:After controlling for confounders, lifetime solvent exposure did not predict reduction in performance for overall domains of function. Lifetime solvent exposures predicted subtle alterations for individual tests of verbal learning, motor coordination, and visuospatial accuracy.CONCLUSION:Concentrations of solvents in paints have steadily declined during the working lifetime of subjects in this study. Although reduced performance was observed on individual tests, these alterations were not consistent across tests and unlikely to be of clinical significance.

Nicotine is one of the major components of electronic cigarette (e-cigarette) emissions. Nicotyrine is a product of nicotine dehydrogenation in e-vapor and is a known inhibitor of human cytochrome P450 enzyme, which mediates nicotine metabolism. However, the emission of nicotine and especially nicotyrine from e-cigarettes has not been studied under real-world vaping patterns. This study examined the impact of e-liquid composition, e-cigarette device power output, and vaping topography on nicotine and nicotyrine concentrations under real-world vaping patterns. The amount of nicotine emitted from e-cigarettes vaped at high e-liquid nicotine levels, high device power, and large puff volumes ranged from 0.365 μg/puff to 236 μg/puff and was comparable to the amount of nicotine emitted from regular cigarettes. E-cigarette coil temperatures (200-300 °C) favored the formation of nicotyrine: E-cigarette vaping generated 2- to 63-fold more nicotyrine per unit nicotine emission than conventional cigarette smoking. High nicotyrine emission from e-cigarettes indicates that nicotine metabolism could be potentially interrupted, which could lead to reduced e-cigarette usage, and result in lower exposures to toxic chemicals (e.g., formaldehyde and acetaldehyde). However, higher serum nicotine levels might increase cancer risks by stimulating nicotinic acetylcholine receptors (nAchRs).