During use of sodium hypochlorite bleach, gas-phase hypochlorous acid (HOCl) and chlorine (Cl2) are released, which can react with organic compounds present in indoor air. Reactivity between HOCl/Cl2 and limonene, a common constituent of indoor air, has been observed. The purpose of this study was to characterize the chemical species generated from gas-phase reactions between HOCl/Cl2 and limonene. Gas-phase reactions were prepared in Teflon chambers housing HOCl, Cl2, and limonene. The resulting chemical products were analyzed using gas-phase preconcentration, followed by gas chromatography and high-resolution mass spectrometry. Several chlorinated products were detected, including limonene species containing one, two, and three chlorines and limonene chlorohydrin. Product concentrations and yields were estimated for the most abundant products, and greater than 80% of transformed limonene was represented in the detected products. Temporal sampling of the reactions allowed time courses to be plotted for limonene decay and chlorinated limonene product generation under different conditions, including the treatments of HOCl/Cl2, Cl2 only, high vs low relative humidity, and +/- ozone. These experiments add product speciation, yield estimates, and an understanding of environmental factors affecting product formation to previous studies, further highlighting the chemical transformations initiated by sodium hypochlorite bleach in indoor air.

The literature on emissions during material extrusion additive manufacturing with 3-D printers is expanding; however, there is a paucity of data for large-format additive manufacturing (LFAM) machines that can extrude high-melt-temperature polymers. Emissions from two LFAM machines were monitored during extrusion of six polymers: acrylonitrile butadiene styrene (ABS), polycarbonate (PC), high-melt-temperature polysulfone (PSU), poly(ether sulfone) (PESU), polyphenylene sulfide (PPS), and Ultem (poly(ether imide)). Particle number, total volatile organic compound (TVOC), carbon monoxide (CO), and carbon dioxide (CO(2)) concentrations were monitored in real-time. Particle emission rate values (no./min) were as follows: ABS (1.7 × 10(11) to 7.7 × 10(13)), PC (5.2 × 10(11) to 3.6 × 10(13)), Ultem (5.7 × 10(12) to 3.1 × 10(13)), PPS (4.6 × 10(11) to 6.2 × 10(12)), PSU (1.5 × 10(12) to 3.4 × 10(13)), and PESU (2.0 to 5.0 × 10(13)). For print jobs where the mass of extruded polymer was known, particle yield values (g(-1) extruded) were as follows: ABS (4.5 × 10(8) to 2.9 × 10(11)), PC (1.0 × 10(9) to 1.7 × 10(11)), PSU (5.1 × 10(9) to 1.2 × 10(11)), and PESU (0.8 × 10(11) to 1.7 × 10(11)). TVOC emission yields ranged from 0.005 mg/g extruded (PESU) to 0.7 mg/g extruded (ABS). The use of wall-mounted exhaust ventilation fans was insufficient to completely remove airborne particulate and TVOC from the print room. Real-time CO monitoring was not a useful marker of particulate and TVOC emission profiles for Ultem, PPS, or PSU. Average CO(2) and particle concentrations were moderately correlated (r (s) = 0.76) for PC polymer. Extrusion of ABS, PC, and four high-melt-temperature polymers by LFAM machines released particulate and TVOC at levels that could warrant consideration of engineering controls. LFAM particle emission yields for some polymers were similar to those of common desktop-scale 3-D printers.

Extrusion of high-melt-temperature polymers on large-format additive manufacturing (LFAM) machines releases particles and gases, though there is no data describing their physical and chemical characteristics. Emissions from two LFAM machines were monitored during extrusion of acrylonitrile butadiene styrene (ABS) and polycarbonate (PC) polymers as well as high-melt-temperature Ultem (poly(ether imide)), polysulfone (PSU), poly(ether sulfone) (PESU), and polyphenylene sulfide (PPS) polymers. Filter samples of particles were collected for quantification of elements and bisphenol A and S (BPA, BPS) and visualization of morphology. Individual gases were quantified on substance-specific media. Aerosol sampling demonstrated that concentrations of elements were generally low for all polymers, with a maximum of 1.6 mg/m(3) for iron during extrusion of Ultem. BPA, an endocrine disruptor, was released into air during extrusion of PC (range: 0.4 ± 0.1 to 21.3 ± 5.3 μg/m(3)). BPA and BPS (also an endocrine disruptor) were released into air during extrusion of PESU (BPA, 2.0-8.7 μg/m(3); BPS, 0.03-0.07 μg/m(3)). Work surfaces and printed parts were contaminated with BPA (<8-587 ng/100 cm(2)) and BPS (<0.22-2.5 ng/100 cm(2)). Gas-phase sampling quantified low levels of respiratory irritants (phenol, SO(2), toluene, xylenes), possible or known asthmagens (caprolactam, methyl methacrylate, 4-oxopentanal, styrene), and possible occupational carcinogens (benzene, formaldehyde, acetaldehyde) in air. Characteristics of particles and gases released by high-melt-temperature polymers during LFAM varied, which indicated the need for polymer-specific exposure and risk assessments. The presence of BPA and BPS on surfaces revealed a previously unrecognized source of dermal exposure for additive manufacturing workers using PC and PESU polymers.

Peracetic acid is a disinfection agent used in medical and food processing facilities, and occupational exposures have been documented. To facilitate characterization of daily occupational exposures, the current work describes the development of a personal sampling technique to quantify the peracetic acid concentration in air samples. Peracetic acid atmospheres were generated in 100 L Teflon chambers, and samples were collected on 350 mg XAD-7 solid sorbent tubes for 4 h at a flow rate of 250 mL/min using a personal sampling pump. Indirect measurement of peracetic acid was achieved by desorption from the sorbent and subsequent treatment with cyclohexene to initiate an epoxidation reaction, formally known as the Prilezhaev reaction. The epoxidation product, cyclohexene oxide, was quantified by gas chromatography-mass spectrometry. The reaction enabled quantification of peracetic acid with high specificity over the common co-contaminants hydrogen peroxide and acetic acid, which were introduced in 10-fold and 100-fold excess to challenge the reaction. The technique also demonstrated an overall estimate of bias and precision of 11 and 8%, respectively, and a limit of detection of 60 ppbv was estimated. Preliminary storage experiments indicate that unreacted peracetic acid is stable on the sorbent tubes for 72 h when stored at -20 °C following collection. Overall, the specificity of the reaction and capability to sample for longer time periods than current methods, in addition to the use of safer personal sampling materials, demonstrate the utility of this technique for peracetic acid measurement in air. © 2022 Elsevier Inc.. All rights reserved.

Chemical reactions on indoor surfaces play an important role in air quality in indoor environments, where humans spend 90% of their time. We focus on the challenges of understanding the complex chemistry that takes place on indoor surfaces and identify crucial steps necessary to gain a molecular-level understanding of environmental indoor surface chemistry: (1) elucidate key surface reaction mechanisms and kinetics important to indoor air chemistry, (2) define a range of relevant and representative surfaces to probe, and (3) define the drivers of surface reactivity, particularly with respect to the surface composition, light, and temperature. Within the drivers of surface composition are the roles of adsorbed/absorbed water associated with indoor surfaces and the prevalence, inhomogeneity, and properties of secondary organic films that can impact surface reactivity. By combining laboratory studies, field measurements, and modeling we can gain insights into the molecular processes necessary to further our understanding of the indoor environment.

The formation of secondary organic aerosol (SOA) indoors is one of the many consequences of the rich and complex chemistry that occurs therein. Given particulate matter has well documented health effects, we need to understand the mechanism for SOA formation indoors and its resulting composition. This study evaluates some uncertainties that exist in quantifying gas-to-particle partitioning of SOA-forming compounds using an indoor detailed chemical model. In particular, we investigate the impacts of using different methods to estimate compound vapour pressures as well as simulating the formation of highly oxygenated organic molecules (HOM) via auto-oxidation on SOA formation indoors. Estimation of vapour pressures for 136 α-pinene oxidation species by six investigated methods led to standard deviations of 28–216%. Inclusion of HOM formation improved model performance across three of the six assessed vapour pressure estimation methods when comparing against experimental data, particularly when the NO2 concentration was relatively high. We also explored the predicted SOA composition using two product classification methods, the first assuming the molecule is dominated by one functionality according to its name, and the second accounting for the fractional weighting of each functional group within a molecule. The SOA composition was dominated by the HOM species when the NO2-to-α-terpineol ratio was high for both product classification methods, as these conditions promoted formation of the nitrate radical and hence formation of HOM monomers. As the NO2-to-α-terpineol ratio decreased, peroxides and acids dominated the simple classification, whereas for the fractional classification, carbonyl and alcohol groups became more important.

There is a paucity of data on additive manufacturing process emissions and personal exposures in real-world workplaces. Hence, we evaluated atmospheres in four workplaces utilizing desktop &quot;3-dimensional&quot; (3-d) printers [fused filament fabrication (FFF) and sheer] for production, prototyping, or research. Airborne particle diameter and number concentration and total volatile organic compound concentrations were measured using real-time instruments. Airborne particles and volatile organic compounds were collected using time-integrated sampling techniques for off-line analysis. Personal exposures for metals and volatile organic compounds were measured in the breathing zone of operators. All 3-d printers that were monitored released ultrafine and fine particles and organic vapors into workplace air. Particle number-based emission rates (#/min) ranged from 9.4 times 109 to 4.4 times 1011 (n = 9 samples) for FFF 3-d printers and from 1.9 to 3.8 times 109 (n = 2 samples) for a sheer 3-d printer. The large variability in emission rate values reflected variability from the printers as well as differences in printer design, operating conditions, and feedstock materials among printers. A custom-built ventilated enclosure evaluated at one facility was capable of reducing particle number and total organic chemical concentrations by 99.7% and 53.2%, respectively. Carbonyl compounds were detected in room air; however, none were specifically attributed to the 3-d printing process. Personal exposure to metals (aluminum, iron) and 12 different organic chemicals were all below applicable NIOSH Recommended Exposure Limit values, but results are not reflective of all possible exposure scenarios. More research is needed to understand 3- d printer emissions, exposures, and efficacy of engineering controls in occupational settings.

Little is known about emissions and exposure potential from vat polymerization additive manufacturing, a process that uses light-activated polymerization of a resin to build an object. Five vat polymerization printers (three stereolithography (SLA) and two digital light processing (DLP) were evaluated individually in a 12.85 m(3) chamber. Aerosols (number, size) and total volatile organic compounds (TVOC) were measured using real-time monitors. Carbonyl vapors and particulate matter were collected for offline analysis using impingers and filters, respectively. During printing, particle emission yields (#/g printed) ranged from 1.3 +/- 0.3 to 2.8 +/- 2.6 x 10(8) (SLA printers) and from 3.3 +/- 1.5 to 9.2 +/- 3.0 x 10(8) (DLP printers). Yields for number of particles with sizes 5.6 to 560 nm (#/g printed) were 0.8 +/- 0.1 to 2.1 +/- 0.9 x 10(10) and from 1.1 +/- 0.3 to 4.0 +/- 1.2 x 10(10) for SLA and DLP printers, respectively. TVOC yield values (microg/g printed) ranged from 161 +/- 47 to 322 +/- 229 (SLA printers) and from 1281 +/- 313 to 1931 +/- 234 (DLP printers). Geometric mean mobility particle sizes were 41.1-45.1 nm for SLA printers and 15.3-28.8 nm for DLP printers. Mean particle and TVOC yields were statistically significantly higher and mean particle sizes were significantly smaller for DLP printers compared with SLA printers (p < 0.05). Energy dispersive X-ray analysis of individual particles qualitatively identified potential occupational carcinogens (chromium, nickel) as well as reactive metals implicated in generation of reactive oxygen species (iron, zinc). Lung deposition modeling indicates that about 15-37% of emitted particles would deposit in the pulmonary region (alveoli). Benzaldehyde (1.0-2.3 ppb) and acetone (0.7-18.0 ppb) were quantified in emissions from four of the printers and 4-oxopentanal (0.07 ppb) was detectable in the emissions from one printer. Vat polymerization printers emitted nanoscale particles that contained potential carcinogens, sensitizers, and reactive metals as well as carbonyl compound vapors. Differences in emissions between SLA and DLP printers indicate that the underlying technology is an important factor when considering exposure reduction strategies such as engineering controls.

Background Emerging reports suggest the potential for adverse health effects from exposure to emissions from some additive manufacturing (AM) processes. There is a paucity of real-world data on emissions from AM machines in industrial workplaces and personal exposures among AM operators. Methods Airborne particle and organic chemical emissions and personal exposures were characterized using real-time and time-integrated sampling techniques in four manufacturing facilities using industrial-scale material extrusion and material jetting AM processes. Results Using a condensation nuclei counter, number-based particle emission rates (ERs) (number/min) from material extrusion AM machines ranged from 4.1 x 1010 (Ultem filament) to 2.2 x 1011 [acrylonitrile butadiene styrene and polycarbonate filaments). For these same machines, total volatile organic compound ERs (microg/min) ranged from 1.9 x 104 (acrylonitrile butadiene styrene and polycarbonate) to 9.4 x 104 (Ultem). For the material jetting machines, the number-based particle ER was higher when the lid was open (2.3 x 1010 number/min) than when the lid was closed (1.5-5.5 x 109 number/min); total volatile organic compound ERs were similar regardless of the lid position. Low levels of acetone, benzene, toluene, and m,p-xylene were common to both AM processes. Carbonyl compounds were detected; however, none were specifically attributed to the AM processes. Personal exposures to metals (aluminum and iron) and eight volatile organic compounds were all below National Institute for Occupational Safety and Health (NIOSH)-recommended exposure levels. Conclusion Industrial-scale AM machines using thermoplastics and resins released particles and organic vapors into workplace air. More research is needed to understand factors influencing real-world industrial-scale AM process emissions and exposures.

Seventy-one percent of US households purchase air care products. Air care products span a diverse range of forms, including scented aerosol sprays, pump sprays, diffusers, gels, candles, and plug-ins. These products are used to eliminate indoor malodors and to provide pleasant scent experiences. The use of air care products can lead to significant benefits as studies have shown that indoor malodor can cause adverse effects, negatively impacting quality of life, hygiene, and the monetary value of homes and cars, while disproportionately affecting lower income populations. Additionally, studies have also shown that scent can have positive benefits related to mood, stress reduction, and memory enhancement among others. Despite the positive benefits associated with air care products, negative consumer perceptions regarding the safety of air care products can be a barrier to their use. During the inaugural Air Care Summit, held on 18 May 2018 in the Washington, DC, metropolitan area, multidisciplinary experts including industry stakeholders, academics, and scientific and medical experts were invited to share and assess the existing data related to air care products, focusing on ingredient and product safety and the benefits of malodor removal and scent. At the Summit's completion, a panel of independent experts representing the fields of pulmonary medicine, medical and clinical toxicology, pediatric toxicology, basic science toxicology, occupational dermatology and experimental psychology convened to review the data presented, identify potential knowledge gaps, and suggest future research directions to further assess the safety and benefits of air care products.

Fused deposition modeling (FDM() ) 3-dimensional printing uses polymer filament to build objects. Some polymer filaments are formulated with additives, though it is unknown if they are released during printing. Three commercially-available filaments that contained carbon nanotubes (CNTs) were printed with a desktop FDM() 3-D printer in a chamber while monitoring total particle number concentration and size distribution. Airborne particles were collected on filters and analyzed using electron microscopy. Carbonyl compounds were identified by mass spectrometry. The elemental carbon content of the bulk CNT-containing filaments was 1.5 to 5.2 wt%. CNT-containing filaments released up to 10(10) ultrafine (d <100 nm) particles/g printed and 10(6) to 10(8) respirable (d ~0.5 to 2 mum) particles/g printed. From microscopy, 1% of the emitted respirable polymer particles contained visible CNTs. Carbonyl emissions were observed above the limit of detection (LOD) but were below the limit of quantitation (LOQ). Modeling indicated that for all filaments, the average proportional lung deposition of CNT-containing polymer particles was 6.5%, 5.7%, and 7.2% for the head airways, tracheobronchiolar, and pulmonary regions, respectively. If CNT-containing polymer particles are hazardous, it would be prudent to control emissions during use of these filaments. This article is protected by copyright. All rights reserved.

Organic nitrates are relatively long-lived species and have been shown to have a potential impact on atmospheric chemistry on local, regional, and even global scales. However, the significance of these compounds in the indoor environment remains to be seen. This work describes an impinger-based sampling and analysis technique for organic nitrate species, focusing on formation via terpene ozonolysis in the presence of nitric oxide (NO). Experiments were conducted in a Teflon film environmental chamber to measure the formation of alkyl nitrates produced from alpha-pinene ozonolysis in the presence of NO and alkanes using gas chromatography with an electron capture detector. For the different concentrations of NO and O3 analyzed, the concentration ratio of [O3]/[NO] around 1 was found to produce the highest organic nitrate concentration, with [O3] = 100 ppb & [NO] = 105 ppb resulting in the most organic nitrate formation, roughly 5 ppb. The experiments on alpha-pinene ozonolysis in the presence of NO suggest that organic nitrates have the potential to form in indoor air between infiltrated ozone/NO and terpenes from household and consumer products.

The chemical composition of indoor air changes due to the reactive nature of the indoor environment. Historically, only the stable parent compounds were investigated due to their ease of measurement by conventional methods. Today, however, scientists can better characterize oxidation products (gas and particulate-phase) formed by indoor chemistry. An understanding of occupant exposure can be developed through the investigation of indoor oxidants, the use of derivatization techniques, atmospheric pressure detection, the development of real-time technologies, and improved complex modeling techniques. Moreover, the connection between exposure and health effects is now receiving more attention from the research community. Nevertheless, a need still exists for improved understanding of the possible link between indoor air chemistry and observed acute or chronic health effects and long-term effects such as work-related asthma.

The yields of carbonyl-containing reaction products from the ozonolysis of alpha-pinene have been investigated using concentrations of ozone found in the indoor environment ([O3] ≤ 100 ppb). An impinger was used to collect gas-phase oxidation products in water, where the derivatization agent O-tert-butylhydroxylamine hydrochloride (TBOX) and gas chromatography-mass spectrometry were used to identify carbonyl-containing species. Seven carbonyl-containing products were observed. The yield of the primary product, pinonaldehyde was measured to be 76 %. Using cyclohexane as a hydroxyl radical (OH) scavenger, the yield of pinonaldehyde decreased to 46 %, indicating the influence secondary OH radicals have on alpha-pinene ozonolysis products. Furthermore, the use of TBOX, a small molecular weight derivatization agent, allowed for the acquisition of the first mass spectral data of oxopinonaldehyde, a tricarbonyl reaction product of alpha-pinene ozonolysis. The techniques described herein allow for an effective method for the collection and identification of terpene oxidation products in the indoor environment.

Printing devices are known to emit chemicals into the indoor atmosphere. Understanding factors that influence release of chemical contaminants from printers is necessary to develop effective exposure assessment and control strategies. In this study, a desktop fused deposition modeling (FDM) 3-D printer using acrylonitrile butadiene styrene (ABS) or polylactic acid (PLA) filaments and two monochrome laser printers were evaluated in a 0.5 m3 chamber. During printing, chamber air was monitored for vapors using a real-time photoionization detector (results expressed as isobutylene equivalents) to measure total volatile organic compound (TVOC) concentrations, evacuated canisters to identify specific VOCs by off-line gas chromatography-mass spectrometry (GC-MS) analysis, and liquid bubblers to identify carbonyl compounds by GC-MS. Airborne particles were collected on filters for off-line analysis using scanning electron microscopy with an energy dispersive x-ray detector to identify elemental constituents. For 3-D printing, TVOC emission rates were influenced by a printer malfunction, filament type, and to a lesser extent, by filament color; however, rates were not influenced by the number of printer nozzles used or the manufacturer's provided cover. TVOC emission rates were significantly lower for the 3-D printer (49 to 3552 microg h-1) compared to the laser printers (5782 to 7735 microg h-1). A total of 14 VOCs were identified during 3-D printing that were not present during laser printing. 3-D printed objects continued to off-gas styrene, indicating potential for continued exposure after the print job is completed. Carbonyl reaction products were likely formed from emissions of the 3-D printer, including 4-oxopentanal. Ultrafine particles generated by the 3-D printer using ABS and a laser printer contained chromium. Consideration of the factors that influenced the release of chemical contaminants (including known and suspected asthmagens such as styrene and 4-oxopentanal) from a FDM 3-D printer should be made when designing exposure assessment and control strategies.

The reaction products from limonene ozonolysis were investigated using the new carbonyl derivatization agent, O-tert-butylhydroxylamine hydrochloride (TBOX). With ozone (O3) as the limiting reagent, five carbonyl compounds were detected. The yields of the carbonyl compounds are discussed with and without the presence of a hydroxyl radical (OH) scavenger, giving insight into the influence secondary OH radicals have on limonene ozonolysis products. The observed reaction product yields for limonaketone (LimaKet), 7-hydroxyl-6-oxo-3-(prop-1-en-2-yl)heptanal (7H6O), and 2-acetyl-5-oxohexanal (2A5O) were unchanged suggesting OH generated by the limonene + O3reaction does not contribute to their formation. The molar yields of 3-isopropenyl-6-oxo-heptanal (IPOH) and 3-acetyl-6-oxoheptanal (3A6O) decreased by 68% and 95%; respectively, when OH was removed. This suggests that OH radicals significantly impact the formation of these products. Nitric oxide (NO) did not significantly affect the molar yields of limonaketone or IPOH. However, NO (20 ppb) considerably decreased the molar reaction product yields of 7H6O (62%), 2A5O (63%), and 3A6O (47%), suggesting NO reacted with peroxyl intermediates, generated during limonene ozonolysis, to form other carbonyls (not detected) or organic nitrates. These studies give insight into the transformation of limonene and its reaction products that can lead to indoor exposures.

The new derivatization agent, O-tert-butylhydroxylamine hydrochloride (TBOX) was used to investigate the carbonyl reaction products from terpinolene ozonolysis. With ozone (O3) as the limiting reagent, four carbonyl compounds were detected: methylglyoxal (MG), 4-methylcyclohex-3-en-1-one, (4MCH), 6-oxo-3-(propan-2-ylidene) heptanal (6OPH), and 3,6-dioxoheptanal (36DOH). The tricarbonyl 36DOH has not been previously observed. Using cyclohexane as a hydroxyl radical (OH) scavenger, the yields of 6OPH and 36DOH were reduced indicating the influence secondary OH radicals have on terpinolene ozonolysis products. However, the MG yield increased and the 4MCH yield was unchanged when OH radicals were scavenged suggesting they are only made by the terpinolene + O3reaction. The detection of 36DOH using TBOX highlights the advantages of a smaller molecular weight derivatization agent for the detection of multi-carbonyl compounds. The product yields from terpinolene ozonolysis experiments conducted in the presence of 20 ppb nitric oxide (NO) remained unchanged except for MG which decreased. However, in experiments where O3was kept constant at 50 ppb and NO was varied (20, 50, 100 ppb) MG, 6OPH, 36DOH decreased with increasing NO while 4MCH increased with increasing NO. The use of TBOX derivatization if combined with other derivatization agents may address a recurring need to simply and accurately detect multi-functional oxygenated species in air.

A new method for derivatizing carbonyl compounds is presented. The conversion of a series of dicarbonyls to oximes in aqueous solution and from gas-phase sampling was achieved using O-tert-butylhydroxylamine hydrochloride (TBOX). Some advantages of using this derivatization agent include: aqueous reactions, lower molecular weight oximes, and shortened oxime-formation reaction time. Additionally, the TBOX derivatization technique was used to investigate the carbonyl reaction products from limonene ozonolysis. With ozone (O3) as the limiting reagent, four carbonyl compounds were detected: 7-hydroxy-6-oxo-3-(prop-1-en-2-yl)heptanal; 3-Isopropenyl-6-oxoheptanal (IPOH), 3-acetyl-6-oxoheptanal (3A6O) and one carbonyl of unknown structure. Using cyclohexane as a hydroxyl (OH) radical scavenger, the relative yields (peak area) of the unknown carbonyl, IPOH, and 3A6O were reduced indicating the influence secondary OH radicals have on limonene ozonolysis products. The relative yield of the hydroxy-dicarbonyl based on the chromatogram was unchanged suggesting it is only made by the limonene+O3 reaction. The detection of 3A6O using TBOX highlights the advantages of a smaller molecular weight derivatization agent for the detection of multi-carbonyl compounds. The use of TBOX derivatization if combined with other derivatization agents may address a recurring need to simply and accurately detect multi-functional oxygenated species in air.

Indoor chemistry may be initiated by reactions of ozone (O3), the hydroxyl radical (OH), or the nitrate radical (NO3) with volatile organic compounds (VOC). The principal indoor source of O3 is air exchange, while OH and NO3 formation are considered as primarily from O3 reactions with alkenes and nitrogen dioxide (NO2), respectively. Herein, we used time-averaged models for residences to predict O3, OH, and NO3 concentrations and their impacts on conversion of typical residential VOC profiles, within a Monte Carlo framework that varied inputs probabilistically. We accounted for established oxidant sources, as well as explored the importance of two newly realized indoor sources: (i) the photolysis of nitrous acid (HONO) indoors to generate OH and (ii) the reaction of stabilized Criegee intermediates (SCI) with NO2 to generate NO3. We found total VOC conversion to be dominated by reactions both with O3, which almost solely reacted with d-limonene, and also with OH, which reacted with d-limonene, other terpenes, alcohols, aldehydes, and aromatics. VOC oxidation rates increased with air exchange, outdoor O3, NO2 and d-limonene sources, and indoor photolysis rates; and they decreased with O3 deposition and nitric oxide (NO) sources. Photolysis was a strong OH formation mechanism for high NO, NO2, and HONO settings, but SCI/NO2 reactions weakly generated NO3 except for only a few cases.

Concern has been raised over the association of diacetyl with lung disease clinically resembling bronchiolitis obliterans in food manufacturing workers. This has resulted in the need for identification of alternative chemicals to be used in the manufacturing process. Structurally similar chemicals, 2,3-pentanedione, 2,3-hexanedione, 3,4-hexanedione and 2,3-heptanedione, used as constituents of synthetic flavoring agents have been suggested as potential alternatives for diacetyl, however, immunotoxicity data on these chemicals are limited. The present study evaluated the dermal irritation and sensitization potential of diacetyl alternatives using a murine model. None of the chemicals were identified as dermal irritants when tested at concentrations up to 50%. Similar to diacetyl (EC3=17.9%), concentration-dependent increases in lymphocyte proliferation were observed following exposure to all four chemicals, with calculated EC3 values of 15.4% (2,3-pentanedione), 18.2% (2,3-hexanedione), 15.5% (3,4-hexanedione) and 14.1% (2,3-heptanedione). No biologically significant elevations in local or total serum IgE were identified after exposure to 25-50% concentrations of these chemicals. These results demonstrate the potential for development of hypersensitivity responses to these proposed alternative butter flavorings and raise concern about the use of structurally similar replacement chemicals. Additionally, a contaminant with strong sensitization potential was found in varying concentrations in diacetyl obtained from different producers.

Terpinolene's (1-methyl-4-(propan-2-ylidene)cyclohexene) reaction with ozone or the nitrate radical was investigated using a denuder/filter apparatus in order to characterize gas-phase and particulate reaction products. Identification of the reaction products (i.e., aldehydes, ketones, dicarbonyls and carboxylic acids) was made using two derivatization methods; O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) to derivatize the carbonyl products or 3-Ethyl-1-[3-(dimethylamino)propyl]carbodiimide hydrochloride (EDC) and 2,2,2-trifluoroethylamine hydrochloride (TFEA) to derivatize the carboxylic acid products. Proposed carbonyl products for ozonolysis of terpinolene are: 4-methylcyclohex-3-en-1-one, 2-hydroxy-4-methylcyclohex-3-en-1-one, glyoxal, methyl glyoxal, 3-oxobutanal, and 6-oxo-3-(propan-2-ylidene)heptanal. Proposed carbonyl products for nitrate radical reaction of terpinolene are: 2-hydroxy-4-methylcyclohex-3-en-1-one, glyoxal, methyl glyoxal, and 4-oxopentanal. No carboxylic acid products were detected with either oxidizing reactant.

Epidemiological investigations suggest a link between exposure to indoor air chemicals and adverse health effects. Consumer products contain reactive chemicals which can form secondary pollutants which may contribute to these effects. The reaction of limonene and ozone is a well characterized example of this type of indoor air chemistry. The studies described here characterize an in vitro model using an epithelial cell line (A549) or differentiated epithelial tissue (MucilAir). The model is used to investigate adverse effects following exposure to combinations of limonene and ozone. In A549 cells, exposure to both the parent compounds and reaction products resulted in alterations in inflammatory cytokine production. A one hour exposure to limonene + ozone resulted in decreased proliferation when compared to cells exposed to limonene alone. Repeated dose exposures of limonene or limonene + ozone were conducted on MucilAir tissue. No change in proliferation was observed but increases in cytokine production were observed for both the parent compounds and reaction products. Factors such as exposure duration, chemical concentration, and sampling time point were identified to influence result outcome. These findings suggest that exposure to reaction products may produce more severe effects compared to the parent compound.

The bimolecular rate coefficients kNO∙3+2-butoxyethanol and kNO∙3+benzylalcohol were measured using the relative rate technique at (297 ± 3) K and 1 atmosphere total pressure. Values of (2.7 ± 0.7) and (4.0 ± 1.0) × 10−15 cm3 molecule−1 s−1 were observed for kNO∙3+2-butoxyethanol and kNO∙3+benzylalcohol, respectively. In addition, the products of 2-butoxyethanol+NO∙3 and benzylalcohol+NO∙3 gas-phase reactions were investigated. Derivatizing agents O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine and N, O-bis (trimethylsilyl)trifluoroacetamide and gas chromatography mass spectrometry (GC/MS) were used to identify the reaction products. For 2-butoxyethanol+NO∙3 reaction: hydroxyacetaldehyde, 3-hydroxypropanal, 4-hydroxybutanal, butoxyacetaldehyde, and 4-(2-oxoethoxy)butan-2-yl nitrate were the derivatized products observed. For the benzylalcohol+NO∙3 reaction: benzaldehyde ((C6H5)C(=O)H) was the only derivatized product observed. Negative chemical ionization was used to identify the following nitrate products: [(2-butoxyethoxy)(oxido)amino]oxidanide and benzyl nitrate, for 2-butoxyethanol+NO∙3 and benzylalcohol+NO∙3, respectively. The elucidation of these products was facilitated by mass spectrometry of the derivatized reaction products coupled with a plausible 2-butoxyethanol or benzylalcohol+NO∙3 reaction mechanisms based on previously published volatileorganiccompound+NO∙3 gas-phase mechanisms.

Over the last two decades, there has been an increasing awareness regarding the potential impact of indoor air pollution on human health. People working in an indoor environment often experience symptoms such as eye, nose and throat irritation. Investigations into these complaints have ascribed the effects, in part, to compounds emitted from building materials, cleaning/consumer products, and indoor chemistry. One suspect indoor air contaminant that has been identified is the dicarbonyl 4-oxopentanal (4-OPA). 4-OPA is generated through the ozonolysis of squalene and several high volume production compounds that are commonly found indoors. Following preliminary workplace sampling that identified the presence of 4-OPA, these studies examined the inflamatory and allergic responses to 4-OPA following both dermal and pulmonary exposure using a murine model. 4-OPA was tested in a combined local lymph node assay (LLNA) and identified to be an irritant and sensitizer. A Th1-mediated hypersensitivity response was supported by a positive response in the mouse ear swelling test (MEST). Pulmonary exposure to 4-OPA caused a significant elevation in nonspecific airway hyperreactivity, increased numbers of lung associated lymphocytes and neutrophils and increased interferon-gamma production by lung associated lymph nodes. These results suggest that both dermal and pulmonary exposure to 4-OPA may elicit irritant and allergic responses and may help to explain some of the adverse health effects associated with poor indoor air quality.

A denuder/filter apparatus was used to collect the gaseous and particulate reaction products from ozonlysis of alpha-pinene, limonene and alpha-terpineol in an effort to develop sampling techniques for characterizing indoor environment chemistry. Carboxylic acids found in the particulate phase were derivatized to 2,2,2-trifuoroethylamides by reaction with 3-ethyl-1-[3-(dimethylamino)propyl]carbodiimide hydrochloride (EDC) and 2,2,2-trifluoroethylamine hydrochloride (TFEA). Carbonyl compounds collected in both gas phase and particulate phase were derivatized to their respective oximes by reaction with O-(2,3,4,5,6-pentafluoro-benzyl)hydroxylamine hydrochloride (PFBHA). The ozonolysis of alpha-pinene yielded the carboxylic acids: cis-pinonic acid and pinic acid and the proposed carboxylic acids methanetricarboxylic acid and terpenylic acid; the carbonyls: 4-oxopentanal, norpinonaldehyde, pinon aldehyde and the proposed carbonyl methylidenepropanedial. The ozonolysis of limonene yielded the carboxylic acids: limonic acid and pinic acid and the carbonyls: 1-(4-methylcyclohex-3-en-1-yl)ethanone (4AMCH), glyoxal, methyl glyoxal, 4-oxopentanal and 6-oxo-3-(prop-1-en-2-yl)heptanal (IPOH). The ozonolysis of alpha-terpineol yielded the proposed carboxylic acids: terpenylic acid and homoterpenylic acid and the carbonyls: (5E)-6-hydroxyhept-5-en-2-one, methyl glyoxal and 4-oxopentanal.

Ozone reacts with indoor-emitted terpenoids to form secondary organic aerosol (SOA). Most SOA research has focused on ozone reactions with single terpenoids or with consumer products, and this paper reports the results from an investigation of SOA formation from ozone reactions with both single terpenoids and mixtures of D-limonene, alpha-pinene, and alpha-terpineol. Transient experiments were conducted at low (25 ppb) and high (100 ppb) initial concentrations of ozone. The three terpenoids were tested singly and in combinations in a manner that controlled for their different reaction rates with ozone. The SOA formation was assessed by examining the evolution in time of the resulting number size-distributions and estimates of the mass concentrations. The results suggest that at higher ozone and terpenoid concentrations. SOA number formation follows a linear trend as a function of the initial rate of reaction. This finding was valid for both single terpenoids and mixtures. Generally speaking, higher ozone and terpenoid concentrations also led to larger geometric mean diameters and smaller geometric standard deviations of fitted lognormal distributions of the formed SOA. By assuming a density, mass concentrations were also assessed and did not follow as consistent of a trend. At low ozone concentration conditions, reactions with only D-limonene yielded the largest number concentrations of any experiment, even more than experiments with mixtures containing D-limonene and much higher overall terpenoid concentrations. This finding was not seen for high ozone concentrations. These experiments demonstrate quantifiable trends for SOA forming reactions of ozone and mixtures, and this work provides a framework for expanding these results to more complex mixtures and consumer products. (C) 2011 Elsevier Ltd. All rights reserved.

Chamber studies were conducted to quantify hydroxyl radical (OH.) yields and to determine if water vapor affected OH. formation in reactions of ozone (O(3) ) with a single terpene, two-component terpene mixtures and a commercial pine oil cleaning product. Solid-phase micro-extraction fibers (SPME) were used for sampling the terpenes and the 2-butanone formation from the hydroxyl reaction with 2-butanol as a measure of OH. yields. Analyses were performed using gas chromatography with flame ionization detection. The individual terpenes' OH. yields of alpha-terpineol, limonene and alpha-pinene were 64 +/- 8%, 64 +/- 6%, and 76 +/- 6%, respectively. OH. yields were also measured from two-component mixtures of these terpenes. In each mixture that contained alpha-terpineol, the overall OH. yield was lower than the modeled OH. yields of the individual components that comprised the reaction mixture. Reactions of a commercial pine oil cleaning product (POC) with O(3) were also studied to determine how the individual terpenes react in a complex mixture system and an OH. formation yield of 51 +/- 6% was measured. Relative humidity did not have a significant effect on the OH. formation in the mixtures studied here.

Indoor environments are dynamic reactors where consumer products (such as cleaning agents, deodorants, and air fresheners) emit volatile organic compounds (VOCs) that can subsequently interact with indoor oxidants such as ozone (O(3)), hydroxyl radicals, and nitrate radicals. Typically, consumer products consist of mixtures of VOCs and semi-VOCs which can react in the gas-phase or on surfaces with these oxidants to generate a variety of oxygenated products. In this study, the reaction of a pine-oil cleaner (POC) with O(3) (100ppb) on a urethane-coated vinyl flooring tile was investigated at 5% and 50% relative humidity. These results were compared to previous alpha-terpineol+O(3) reactions on glass and vinyl surfaces. Additionally, other terpene and terpene alcohol mixtures were formulated to understand the emission profiles as seen in the POC data. Results showed that the alpha-terpineol+O(3) reaction products were the prominent species that were also observed in the POC/O(3) surface experiments. Furthermore, alpha-terpineol+O(3) reactions generate the largest fraction of oxygenated products even in equal mixtures of other terpene alcohols. This finding suggests that the judicial choice of terpene alcohols for inclusion in product formulations may be useful in reducing oxidation product emissions.

Reaction rates and reaction probabilities have been quantified on model indoor surfaces for the reaction of ozone with two monoterpenes (Delta(3) -carene and d-limonene). Molar surface loadings were obtained by performing breakthrough experiments in a plug-flow reactor (PFR) packed with beads of glass, polyvinylchloride or zirconium silicate. Reaction rates and probabilities were determined by equilibrating the PFR with both the terpene and ozone and measuring the ozone consumption rate. To mimic typical indoor conditions, temperatures of 20 degrees C, 25 degrees C, and 30 degrees C were used in both types of experiments along with a relative humidity ranging from 10% to 80%. The molar surface loading decreased with increased relative humidity, especially on glass, suggesting that water competed with the terpenes for adsorption sites. The ozone reactivity experiments indicate that higher surface loadings correspond with higher ozone uptake. The reaction probability for Delta(3) -carene with ozone ranged from 2.9x10(-6) to 3.0x10(-5) while probabilities for d-limonene ranged from 2.8x10(-5) to 3.0x10(-4) . These surface reaction probabilities are roughly 10 to 100 times greater than the corresponding gas-phase values. Extrapolation of these results to typical indoor conditions suggests that surface conversion rates may be substantial relative to gas-phase rates, especially for lower volatility terpenoids.

Over the last two decades, there has been increasing awareness regarding the potential impact of indoor air pollution on health. Exposure to volatile organic compounds (VOCs) or oxygenated organic compounds formed from indoor chemistry has been suggested to contribute to adverse health effects. These studies use an in vitro monitoring system called VitroCell, to assess chemicals found in the indoor air environment. The structurally similar dicarbonyls diacetyl, 4-oxopentanal (4-OPA), glyoxal, glutaraldehyde, and methyl glyoxal were selected for use in this system. The VitroCell module was used to determine whether these dicarbonyls were capable of inducing inflammatory cytokine expression by exposed pulmonary epithelial cells (A549). Increases in the relative fold change in mRNA expression of the inflammatory mediators, interleukin (IL)-6, interleukin (IL)-8, granulocyte-macrophage colony-stimulating factor (GM-CSF), and tumor necrosis factor alpha (TNF-alpha) were identified following exposure to diacetyl, 4-OPA, glyoxal, glutaraldehyde, and methyl glyoxal when compared to a clean air control. Consistent results were observed when the protein levels of these cytokines were analyzed. Exposure to 4-OPA significantly elevated IL-8, IL-6, GM-CSF and TNF-alpha while glutaraldehyde caused significant elevations in IL-6, IL-8 and TNF-alpha. IL-6 and IL-8 were also significantly elevated after exposure to diacetyl, glyoxal and methyl glyoxal. These studies suggest that exposure to structurally similar oxygenated reaction products may be contributing to some of the health effects associated with indoor environments and may provide an in vitro method for identification and characterization of these potential hazards.