Reaction Products Of Ozone Research Articles

Indoor ozone reaction products: Contributors to the respiratory health effects associated with low-level outdoor ozone

Low-level outdoor ozone (O3) exposure has been associated with adverse respiratory health effects, whereas substantially higher O3 concentrations have been required to exert measurable effects in controlled studies. This discrepancy remains poorly understood. After entering indoors, a substantial portion of O3 reacts with indoor chemicals to generate ozone reaction products that are potentially more toxic than O3 itself. We hypothesize that ozone reaction product exposures contribute to the adverse respiratory effects associated with low-level outdoor O3 exposure. In a panel study of 70 healthy adults, each was measured four times during a low-ozone season (maximum 8-h average: 29 ± 13 ppb). We found that higher average outdoor O3 concentrations, irrespective of whether participants were outdoors or indoors, were significantly associated with worsened spirometric lung function (i.e., FVC, FEV1, FEF25-75) and airway mechanics (i.e., R5, R20) indicators. Per interquartile range (IQR) increase in average outdoor O3 exposure when participants were indoors with windows closed (exposure proxy for ozone reaction products + indoor O3) was significantly associated with worsening of multiple respiratory function indicators including FVC, FEV1, FEF25-75, Z5, R5, and R20 by 0.56–3.08%. In contrast, per IQR increase in average outdoor O3 exposure when participants were outdoors or indoors with windows open (exposure proxy for O3 without ozone reaction products) was only significantly and adversely associated with worsening of one respiratory function indicator X5 by 1.4%. These findings support our hypothesis and suggest further evaluation of indoor ozone reaction products' contribution to adverse health effects induced by outdoor O3 exposure.

Synergistic Effects of Ozone Reaction Products and Fine Particulate Matter on Respiratory Pathophysiology in Children with Asthma

Synergistic Effects of Ozone Reaction Products and Fine Particulate Matter on Respiratory Pathophysiology in Children with Asthma

The features of haloacetic acid oxidation that contribute to stratospheric ozone depletion

Environmental context Due to The Montreal Protocol, stratospheric ozone concentration is slowly regenerating, however, the recovery rate is slower than predicted by photochemical models. FTIR spectroscopy together with quantum chemical calculations confirmed that ozone reacts with halogenated acids adsorbed at a model aerosol surface. Reactions occur at low temperatures without photochemical activation with formation of halogen oxides that are known to promote catalytic cycles of ozone depletion. Abstract The present work addresses the problem of stratospheric ozone depletion. While gas phase and photochemically induced reactions of ozone are well studied, the mechanisms of heterogeneous O3 interactions with different halogenated species still remain uncertain. An in situ FTIR investigation of low-temperature heterogeneous reactions of ozone and haloacetic acids in conditions close to stratospheric was performed and supported by ab initio quantum chemical calculations. Products of ozone reaction with differently chlorine and bromine-substituted acetic acids were identified and possible reactions pathways were suggested. Ozone can attach to a carbon atom to release a halogen atom that forms a halogen oxide. Halogen oxide in its turn can take part in the catalytic cycles of ozone depletion. Suggested reaction pathways leading to the additional release of the chlorine oxides can enhance the atmospheric models that calculate ozone concentration.

Yields and Variability of Ozone Reaction Products from Human Skin.

The skin of 20 human participants was exposed to ∼110 ppb O3 and volatile products of the resulting chemistry were quantified in real time. Yields (ppb product emitted/ppb ozone consumed) for 40 products were quantified. Major products of the primary reaction of ozone-squalene included 6-methyl 5-hepten-2-one (6-MHO) and geranyl acetone (GA) with average yields of 0.22 and 0.16, respectively. Other major products included decanal, methacrolein (or methyl vinyl ketone), nonanal, and butanal. Yields varied widely among participants; summed yields ranged from 0.33 to 0.93. The dynamic increase in emission rates during ozone exposure also varied among participants, possibly indicative of differences in the thickness of the skin lipid layer. Factor analysis indicates that much of the variability among participants is due to factors associated with the relative abundance of (1) "fresh" skin lipid constituents (such as squalene and fatty acids), (2) oxidized skin lipids, and (3) exogenous compounds. This last factor appears to be associated with the presence of oleic and linoleic acids and could be accounted for by uptake of cooking oils or personal care products to skin lipids.

Modeling the Time-Dependent Concentrations of Primary and Secondary Reaction Products of Ozone with Squalene in a University Classroom.

Volatile organic chemicals are produced from reactions of ozone with squalene in human skin oil. Both primary and secondary reaction products, i.e., 6-methyl-5-hepten-2-one (6-MHO) and 4-oxopentanal (4-OPA), have been reported in indoor occupied spaces. However, the abundance of these products indoors is a function of many variables, including the amount of ozone and occupants present as well as indoor removal processes. In this study, we develop a time-dependent kinetic model describing the behavior of ozone/squalene reaction products indoors, including the reaction process and physical adsorption process of products on indoor surfaces. The key parameters in the model were obtained by fitting time-resolved concentrations of 6-MHO, 4-OPA, and ozone in a university classroom on 1 day with multiple class sessions. The model predictions were subsequently tested against observations from four additional measurement days in the same classroom. Model predictions and experimental data agreed well (R2 = 0.87-0.92) for all test days, including ∼7 class sessions covering a range of occupants (10-70) and ozone concentrations (0.09-32 ppb), demonstrating the effectiveness of the model. Accounting for surface uptake of 6-MHO and 4-OPA significantly improved model predictions (R2 = 0.52-0.76 without surface uptake), reflecting the importance of including surface interactions to quantitatively represent product behavior in indoor environments.

Chemical reaction rates of ozone in water infusions of wheat, beech, oak and pine leaves of different ages

In this study we present results from a laboratory experiment designed to evaluate the first-order chemical reaction rate (k) of ozone in water films on plant leaves occurring during dew or rain events. Ozone deposition to wet cuticles is indeed known to be a significant pathway of ozone deposition, but the underlying processes are not yet well understood. Leaf infusions obtained by infusing plant leaves with water at room temperature were introduced into a wet effluent denuder fed with a flux of ozone-rich air. Ozone, water vapour concentrations and temperature were measured in both inlet and outlet airflows in order to compute ozone reaction rates kr using an ozone reaction-diffusion model in the water film. Ascorbate solutions were used to validate the set up and led to kr = 3.6 107 M−1 s−1 consistent with the literature. Ozone reaction rates were determined for wheat, beech, oak and pine leaves infusions at several developmental stages, as well as for rain samples. Leaf infusions reaction rates were between 240 s−1 and 3.4 105 s−1 depending on species and developmental stage, while k for rain water ranged from 130 to 830 s−1. Wheat leaves solutions showed significantly (P < 0.001) higher kr (median 73800 s−1) compared to the other tree species (median 4560 s−1). Senescing or dead leaves also showed significantly (P < 0.001) larger k (median 21100 s−1) compared to non-senescent leaves (median 3200 s−1). In wheat, k also increased with increasing yellow leaf fraction. Our results are in the range of previously reported ozone deposition on wet leaves in field or chamber studies. Composition of leaves infusions and previous studies on throughfall and dew composition shows that reaction of ozone with inorganic compounds may only explain the smallest measured k. The largest k observed during senescent are most likely due to reaction with organic material. This is confirmed by LC-MS measurements which showed detection of ascorbate and VOCs as well as the reaction products of ozone with these compounds.

Analysis of the cost effectiveness of combined particle and activated carbon filters for indoor ozone removal in buildings

This study involved the development of a model for evaluating the potential costs and benefits of ozone control with combined particle/activated carbon filtration (referred to here as activated carbon filtration) in buildings. The modeling effort included the prediction of indoor ozone and ozone reaction products with and without activated carbon filtration in the HVAC system. Benefit-to-cost ratios were estimated for various types of buildings in 12 American cities in 5 different climate zones. Health benefits were evaluated using disability-adjusted life-years attributed to the difference in indoor ozone concentration with and without activated carbon filtration, and included city-specific age demographics for each simulation. Costs of activated-carbon filters included capital cost differences when compared against conventional HVAC filters of similar minimum efficiency reporting value rating (e.g., minimum efficiency reporting value 6–8), energy penalties due to additional pressure drop, and regional utility rates. When assuming a single-pass ozone removal efficiency of 60%, carbon filtration during the ozone season was beneficial and economically viable in commercial office buildings, long-term health-care facilities, and K–12 schools. Residential activated carbon filtration could be economically viable for conditions of higher ozone removal efficiencies, lower filter costs, and lower pressure drop across the filter.

Stoichiometry and products of ozone reaction with chloride ion in an acidic medium

It is shown by means of direct spectrophotometry in the UV and visible ranges that the only product of the O3 reaction with Cl−(aq) in an acidic medium is molecular chlorine Cl2; in solutions, it is in equilibrium with the complex ion Cl 3 − . It is found that the consumption of one ozone molecule corresponds to the formation of one chlorine molecule. The stoichiometric equation for the reaction is obtained.

Online investigations on ozonation products of pyrene and benz[ a]anthracene particles with a vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer

The reaction products of ozone with pyrene and benz[ a]anthracene absorbed on azelaic acid particles under the pseudo-first-order reaction conditions have been investigated with a vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS). The pyrene and benz[ a]anthracene particles with the initial concentrations of ∼1 mg m −3 are respectively exposed to ∼22 ppm ozone in a reaction chamber with a volume of ∼180 L. The time-of-flight mass spectra of the particulate ozonides are obtained. The assignments of the mass spectra reveal that 4-carboxy-5-phenanthrene-carboxyaldehyde (71%) and hydroxypyrene (23%) are the main solid state ozonides of pyrene, while 2-(2-formyl)phenyl-3-naphthoic acid (35%), hydroxybenz[ a]anthrone (30%), and benz[ a]anthracene-7,12-dione (18%) are the main solid state ozonides of benz[ a]anthracene. The pathways of the ozonations are proposed in the paper.

The influence of chemical interactions at the human surface on breathing zone levels of reactants and products

Using computational fluid dynamics simulations of an occupant in a ventilated room, we find that breathing zone ozone levels can be substantially lower and ozone reaction products associated with human surfaces (ORPHS) levels considerably higher than room levels. For air exchange rates <3/h, the ratio of the breathing zone to the ozone concentration 1 m from the body (bulk air), r(ozone), ranges from 0.59 to 0.75 for floor or ceiling air supply. ORPHS are enriched in the breathing zone, with concentrations for these conditions ranging from 1.2 to 2.5 greater than bulk air concentrations. At high air exchange rates (>8/h), the breathing zone concentrations approach bulk air concentrations (r(ozone) > 0.9) with a floor supply, whereas large concentration gradients occur between breathing zone and bulk air with a ceiling supply. At these high air exchange rates, ORPHS levels are 1.6-2.0 and 2.9-6.0 times the bulk air concentrations for floor and ceiling supply, respectively. The extent of depletion of ozone or enrichment of ORPHS is large enough that reliance on micro-environmental measurements alone, to assess the intake of ozone or ORPHS, is undesirable. Chemical reactions between ozone and human and clothing surfaces are predicted to significantly reduce ozone concentrations, and increase ozone reaction products associated with human surfaces (ORPHS) concentrations, in the breathing zone, relative to those concentrations in the larger microenvironment of a room. Existing measurements may overestimate ozone exposure and intake in typical indoor environments.

Kinetics and Reaction Products of Ozone and Surface-Bound Squalene

Abstract Because of the high occupant density in aircraft, the surface chemistry of ozone and squalene, an important component of skin oil, was evaluated. A reaction probability of (45±14)×10−5 was determined for the reaction of squalene (2,6,10,15,19,23-hexamethyl-2,6,10,14,18,22-tetracosahexaene) with ozone (50 parts per billion (ppb)) on a glass plate surface using the Field and Laboratory Emission Cell (FLEC) Automation and Control System (FACS). To more clearly define part of squalene’s indoor environment degradation mechanism, gas-phase and surface-bound products of the squalene+O3 reaction were also investigated. Emitted products were captured in solution, derivatized with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA), and analyzed by gas chromatography and ion trap mass spectroscopy. The identified squalene+O3 reaction products were: 6-methyl-5-hepten-2-one (6MHO, ((CH3)2CCH(CH2)2 C(O)CH3)), glyoxal (ethanedial, HC(O)C(O)H), 4-oxopentanal (4OPA, CH3C(O)CH2CH2 CH(O)), and 6,10-dimethylundeca-5,9-dien-2-one (geranyl acetone). The compound 5,9,13-trimethyltetradeca-4,8,12-trienal is proposed as the other major squalene+O3 reaction product. This compound was determined from mass spectrometry coupled with plausible squalene+O3 reaction mechanisms based on previously published volatile organic compound+O3 gas-phase reaction mechanisms.

Interfacial Chemistry in Indoor Environments

Although many researchers have studied ozone chemistry on indoor surfaces, little is known about the consequences of higher levels of ozone reaction products in indoor air.

Pulmonary effects of inhaled limonene ozone reaction products in elderly rats

d-Limonene is an unsaturated volatile organic chemical found in cleaning products, air fresheners and soaps. It is oxidized by ozone to secondary organic aerosols consisting of aldehydes, acids, oxidants and fine and ultra fine particles. The lung irritant effects of these limonene ozone reaction products (LOP) were investigated. Female F344 rats (2- and 18-month-old) were exposed for 3 h to air or LOP formed by reacting 6 ppm d-limonene and 0.8 ppm ozone. BAL fluid, lung tissue and cells were analyzed 0 h and 20 h later. Inhalation of LOP increased TNF-α, cyclooxygenase-2, and superoxide dismutase in alveolar macrophages (AM) and Type II cells. Responses of older animals were attenuated when compared to younger animals. LOP also decreased p38 MAP kinase in AM from both younger and older animals. In contrast, while LOP increased p44/42 MAP kinase in AM from younger rats, expression decreased in AM and Type II cells from older animals. NF-κB and C/EBP activity also increased in AM from younger animals following LOP exposure but decreased or was unaffected in Type II cells. Whereas in younger animals LOP caused endothelial cell hypertrophy, perivascular and pleural edema and thickening of alveolar septal walls, in lungs from older animals, patchy accumulation of fluid within septal walls in alveolar sacs and subtle pleural edema were noted. LOP are pulmonary irritants inducing distinct inflammatory responses in younger and older animals. This may contribute to the differential sensitivity of these populations to pulmonary irritants.

Disturbance of the determination of aldehydes and ketones: Structural elucidation of degradation products derived from the reaction of 2,4-dinitrophenylhydrazine (DNPH) with ozone

None of the reaction products of ozone and DNPH immobilized on solid phase support have been identified yet. However, they can interfere with the determination of carbonyl compounds in ozone containing air when analysis is performed by sampling and derivatization with DNPH coated silica cartridges. To elucidate the structure of these compounds, DNPH silica cartridges were treated with synthetic air containing defined concentrations of ozone and eluted with acetonitrile. The products were characterized by HPLC-UV/Vis and nuclear magnetic resonance (NMR) spectroscopy. Three of the degradation products were identified as 2,4-dinitrophenol, 2,4-dinitroaniline and 1,3-dinitrobenzene. The identification was confirmed by comparison with commercially available standard compounds. The other elutable products were characterized as substituted aromatic compounds. The formation of all characterized products is consistent with a radical mechanism which has been previously discussed in the literature.

Environmental Ozone Field Study on Pulmonary and Subjective Responses of Assumed Risk Groups

Lung function parameters (measured with a body plethysmograph) and subjective votes on irritations of eyes or airways were taken from subjects belonging to four assumed ozone risk groups and one control group (40 subjects each: senior citizens, juvenile asthmatics, forestry workers, athletes, and clerks). Every subject was examined on 8 days both in the morning and in the afternoon. The intention was to obtain an equal distribution of measuring days with elevated and low ozone concentrations, respectively, for each subject. On average the ozone concentrations reached 0.070 ppm on "ozone days" [maximum concentration 0.112 ppm for clerks (outdoors), 0.100 ppm for senior citizens, 0.091 for juvenile asthmatics, 0.086 ppm for athletes, and 0.077 ppm for forestry workers] and 0.028 ppm on "control days" (minimum 0.001 ppm). The results show no relevant ozone effect for the group with the lowest ventilation rate (senior citizens) and only marginal reductions of respiratory flows and volumes for athletes. Pulmonary decrements of juvenile asthmatics on ozone days were small but larger than those documented in the literature for healthy children. Forestry workers and clerks had significantly higher airway resistances on ozone days, although having been exposed to the lowest ozone concentrations of all groups. Thus, on days with moderately elevated levels of ozone in the environment it is assumed that ozone itself has a minor influence on pulmonary responses compared to that of other constituents of the air in certain locations like in forests or indoors on these days. These could be reaction products of ozone with motor tool exhausts in the case of forestry workers or substances originating from ozone deposition on the surfaces of the offices.

Reaction Products of Ozone: A Review

The reaction products of ozone that form during the oxidation of compounds found in aqueous media are reviewed. Reaction products of ozone are well documented only for a limited number of substrates, and mechanistic information is quite rare. Decomposition of ozone during its reactions, sometimes induced by matrix impurities or by the by-products of the reactions, will generate highly reactive hydroxyl radicals. Thus, even reactions occurring at pH less than 7 may have radical character. More complete destruction of organic substrates may be enhanced by using catalysts, such as ultraviolet radiation or hydrogen peroxide, to accelerate radical formation. However, complete mineralization is generally not practical economically, so partially oxidized by-products can be expected under typical treatment conditions. Ozone by-products tend to be oxygenated compounds that are usually, but not always, more biodegradable and less toxic than xenobiotic precursors. Of particular interest are hydroperoxide by-products, which may have escaped detection because of their lability, and unsaturated aldehydes. Inorganic by-products tend to be in high oxidation states, which in some cases (e.g., some metallic elements) may lead to enhanced removal by flocculation and sedimentation. In other cases oxidation may lead to formation of reactive species such as hypobromous acid from bromide ion or permanganate from manganous ion. In general, more research is required before a valid assessment of the risks of ozone by-products can be made.

Reaction products of ozone: a review.

The reaction products of ozone that form during the oxidation of compounds found in aqueous media are reviewed. Reaction products of ozone are well documented only for a limited number of substrates, and mechanistic information is quite rare. Decomposition of ozone during its reactions, sometimes induced by matrix impurities or by the by-products of the reactions, will generate highly reactive hydroxyl radicals. Thus, even reactions occurring at pH less than 7 may have radical character. More complete destruction of organic substrates may be enhanced by using catalysts, such as ultraviolet radiation or hydrogen peroxide, to accelerate radical formation. However, complete mineralization is generally not practical economically, so partially oxidized by-products can be expected under typical treatment conditions. Ozone by-products tend to be oxygenated compounds that are usually, but not always, more biodegradable and less toxic than xenobiotic precursors. Of particular interest are hydroperoxide by-products, which may have escaped detection because of their lability, and unsaturated aldehydes. Inorganic by-products tend to be in high oxidation states, which in some cases (e.g., some metallic elements) may lead to enhanced removal by flocculation and sedimentation. In other cases oxidation may lead to formation of reactive species such as hypobromous acid from bromide ion or permanganate from manganous ion. In general, more research is required before a valid assessment of the risks of ozone by-products can be made.

The mutagenic activity of the products of ozone reaction with propylene in the presence and absence of nitrogen dioxide

This study was performed to determine if propylene reaction with ozone could account for the large mutagenic activity we have observed in irradiated propylene/NO/sub x/ mixtures. In a 22.7-m/sup 3/ flow mode smog chamber, 5.4 ppm of propylene was allowed to react with 0.9 ppm of ozone either in the presence or in the absence of 0.2 ppm of nitrogen dioxide (at 25 /sup 0/C in the dark). The steady-state reactant and product distribution was then tested for total mutagenic activity by exposing Salmonella typhimurium strain TA100 to the gas-phase chamber effluent. The total product dosage in the test plates was varied by exposing them for 0, 5, 10, 15, and 20 h. Salmonella typhimurium survivor levels were obtained at each length of exposure. The number of revertants per plate increased at a rate of approx. 4-5 per hour, while the survivor level decreased throughout the exposure. Most of the total mutagenic activity can be accounted for by the presence of formaldehyde. The total mutagenic activity observed was, however, much smaller than that observed in the irradiated propylene/NO/sub x/ system, for comparable amounts of propylene consumed.

Toxicity of polycyclic aromatic hydrocarbons: I. Effect of phenanthrene, pyrene, and their ozonized products on blood chemistry in rats

Male Sprague-Dawley rats were treated with a single ip injection of physiological saline (3.0 ml/kg), dimethyl sulfoxide (DMSO, 3.0 ml/kg), phenanthrene (150 mg/kg), ozonized products of phenanthrene (150 mg/kg), pyrene (150 mg/kg), or ozonized products of pyrene (150 mg/kg). Phenanthrene, pyrene, and their ozonized products were dissolved in DMSO (50 mg/ml). Serum aspartate aminotransferase (AST) activity was increased significantly 24 hr after ip administration of DMSO when compared with physiological saline. Phenanthrene produced a significant elevation of serum AST and γ-glutamyl transpeptidase (GGTP) levels related to physiological saline and DMSO-injected rats 24 hr after injection. However, GGTP levels for groups treated with DMSO or phenanthrene were not significantly increased when compared with saline groups 72 hr after injection. Ozonized products of phenanthrene produced a significant elevation of serum AST, alanine aminotransferase (ALT), GGTP, and bilirubin levels when compared with groups treated with physiological saline, DMSO, and phenanthrene 24 or 72 hr after injections. The ozonized products of phenanthrene also produced significant elevation of serum creatinine levels compared with physiological saline, DMSO, and phenanthrene groups at 24 hr after treatment and of blood urea nitrogen (BUN) levels at 24 and 72 hr. Although pyrene caused a small but significant increase in the serum AST and bilirubin levels 24 hr after treatment, no significant change in the serum AST, ALT, GGTP, BUN, and creatinine levels were observed with the ozonized products of pyrene at 24 or 72 hr. This study demonstrates significant alterations in serum chemistry induced by reaction products of ozone with phenanthrene. No such effect was observed when the products of pyrene ozonation were administered. Although the ozonation products of pyrene were not toxic under the conditions of this study, phenanthrene products were more hepatotoxic than was phenanthrene itself. Nephrotoxicity was also an apparent effect of ozonized phenanthrene. Since ozone-polycyclic aromatic hydrocarbon (PAH) reactions may occur in the atmosphere, these reactions might produce compounds that are more toxic than either ozone or the PAH alone.

A Surface Study of Ozone Attack and Antiozonant Protection of Carbon Black Loaded Natural Rubber Compounds

Abstract This work reports a direct surface analysis of ozonization of carbon black loaded NR compounds by ATR and SEM. On ozonization of raw NR or NR containing carbon black, a thick layer builds up consisting of ozonides and carbonyl compounds. It is suggested that this layer is composed principally of the reaction products of ozone with unsaturated fatty acids and unsaturated fatty acid esters found in NR. On ozonization of cured and uncured carbon black loaded NR compounds containing curatives, the NR is attacked causing a decrease of rubber on the surface and a corresponding increase in the surface concentration of carbon black. The thick ozonide/carbonyl layer did not form, probably due to the coordination of the fatty acids and esters with ZnO, which was added with the curatives. On ozonization of carbon black-loaded NR compounds containing N,N′-dioctyl-p-phenylenediamine antiozonant, a continuous film is seen by SEM which has an ATR spectrum essentially identical to ozonized antiozonant. There is no evidence of ozonized NR products, or of complex reaction products between antiozonant and ozonized NR. These results are consistent with a dual scavenger and protective layer mechanism for antiozonant protection.