Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Ozone”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14Linked to original sources
PubMed2004

Study on the formation and transport of ozone in relation to the air quality management and vegetation protection in Tenerife (Canary Islands).

An experimental study on the formation and transport of ozone in ambient air was performed in Tenerife (Canary Islands) in order to investigate the processes affecting ozone levels and air quality. The special features of Tenerife (prevalence of the trade wind pattern (NE), orography and the specific location of the local ozone sources) permit to quantify the role of the 'long-range transport from northern latitudes' versus the 'formation and transport of ozone downwind of the main urban areas' of Tenerife. Levels of O(3), NO(2) and O(X) were monitored in different types of environments to achieve this purpose. The results showed that: (1) upwind of the urban areas ozone is mainly transported from the ocean by trade winds, (2) local ozone titration (by NO) and ozone replenishment from the ocean are the main causes of ozone variations in urban and suburban areas, and (3) photochemical ozone production occurs downwind of the urban areas. Photochemical production causes daylight O(3) and O(X) levels downwind of urban areas to be frequently (60% and 35% days/year, respectively) higher than upwind of the urban sites (O(3) and O(X) excess frequently in the range 5-20 ppbv). Due to the above processes, different daily ozone cycles occur in short distances (<30 km), with maximum O(3) levels during daylight or night depending on the site. Ozone phytotoxicity was assessed by calculating the AOT40 index upwind and downwind of the main urban areas. The critical value for the 5-day-AOT40 index was simultaneously exceeded at the two sites (few times/year) during long-range transport events. During the additional exceedances of the critical value downwind of the urban area, relatively high 5-day-AOT40 values were recorded upwind of the urban site. Thus, long-range transport from northern latitudes may produce relatively high 5-days-AOT40 levels in the oceanic boundary layer. These results are important for the protection of the large number of endemic plants in the Canaries. The conceptual model discussed in this study may be qualitatively applied to other islands which possess features similar to those of Tenerife.

Air Movements↗
PubMed2004

Air sampling of aromatic hydrocarbons in the presence of ozone by solid-phase microextraction.

Effects of ozone on air sampling of standard gas mixtures of aromatic hydrocarbons were tested using solid-phase microextraction (SPME). Standard concentrations of ozone ranging from 10 ppb (v/v) to 6400 ppm (v/v) were generated using an in-house built ozone generator based on corona discharge. Effects of temperature, discharge voltage, and oxygen flow on the ozone generation were tested. The working dc voltage had the greatest effect on generated ozone concentration and was proportional to the ozone concentration. Generation temperature and oxygen flow rate were inversely proportional to ozone concentrations. Produced ozone was mixed with standard benzene, toluene, ethylbenzene, and xylenes (BTEX) gas at less than 100 ppb (v/v). Air samples were collected with poly(dimethylsiloxane) (PDMS) 100 microm SPME fibers and analyzed by gas chromatography (GC)-flame ionization detection (FID) and GC-MS. Significant reductions of BTEX concentrations were observed. In addition, some products of BTEX-ozone-oxygen reactions were identified. SPME worked well as a rapid sampler for BTEX and BTEX-ozone-oxygen reaction products. No significant deterioration of the PDMS coating and no significant reduction of absorption capacity were observed after repeated exposure to ozone.

Air↗
PubMed2006

Activated sludge ozonation to reduce sludge production in membrane bioreactor (MBR).

Total experimental period was divided into two stages. At first stage, a series of batch studies were carried out to get an understanding of the effect of ozonation on sludge properties. At the following stages, three membrane bioreactors (MBRs) with different amounts of activated sludge to be ozonated were run in parallel for a long period to evaluate the influence of sludge ozonation on sludge yield and permeate quality. Through batch study, it was found that ozone could disrupt the cell walls and cause the release of plasm from the cells, then the amounts of soluble organics in the solution increased with ozonation time. With the rise of soluble organics, the amount of soluble organics to be mineralized increased as well, which would reduce the soluble organics content. For the counteraction between these two aspects, a pseudo-balance could be achieved, and soluble organics would vary in a limited range. Sludge ozonation also increased the contents of soluble nitrogen and phosphorus in the solution. On the basis of batch study, a suitable ozone dosage of 0.16 kg O(3)/kg MLSS was determined. Three systems were run in parallel for a total period of 120 days; it was demonstrated that a part of activated sludge ozonation could reduce sludge production significantly, and biological performance of mineralization and nitrification would not be inhibited due to sludge ozonation. Experimental results proved that the combination of ozonation unit with MBR unit could achieve an excellent quality of permeate as well as a small quantity of sludge production, and economic analysis indicated that an additional ozonation operating cost for treatment of both wastewater and sludge was only 0.096 Yuan (US$ 0.0115)/m(3) wastewater.

Bioreactors↗
PubMed2005

Mechanism of site-specific DNA damage induced by ozone.

Ozone has been shown to induce lung tumors in mice. The reactivity of ozone with DNA in an aqueous solution was investigated by a DNA sequencing technique using 32P-labeled DNA fragments. Ozone induced cleavages in the deoxyribose-phosphate backbone of double-stranded DNA, which were reduced by hydroxyl radical scavengers, suggesting the participation of hydroxyl radicals in the cleavages. The ozone-induced DNA cleavages were enhanced with piperidine treatment, which induces cleavages at sites of base modification, but the inhibitory effect of hydroxyl radical scavengers on the piperidine-induced cleavages was limited. Main piperidine-labile sites were guanine and thymine residues. Cleavages at some guanine and thymine residues after piperidine treatment became more predominant with denatured single-stranded DNA. Exposure of calf thymus DNA to ozone resulted in a dose-dependent increase of the 8-oxo-7,8-dihydro-2'-deoxyguanosine formation, which was partially inhibited by hydroxyl radical scavengers. ESR studies using 5,5-dimethylpyrroline-N-oxide (DMPO) showed that aqueous ozone produced the hydroxyl radical adduct of DMPO. In addition, the fluorescein-dependent chemiluminescence was detected during the decomposition of ozone in a buffer solution and the enhancing effect of D2O was observed, suggesting the formation of singlet oxygen. However, no or little enhancing effect of D2O on the ozone-induced DNA damage was observed. These results suggest that DNA backbone cleavages were caused by ozone via the production of hydroxyl radicals, while DNA base modifications were mainly caused by ozone itself and the participation of hydroxyl radicals and/or singlet oxygen in base modifications is small, if any. A possible link of ozone-induced DNA damage to inflammation-associated carcinogenesis as well as air pollution-related carcinogenesis is discussed.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2004

Impact of a magnetic ion exchange resin on ozone demand and bromate formation during drinking water treatment.

The objective of this research was to examine the impact of a magnetic ion exchange resin (MIEX) on ozone demand and bromate formation in two different ozonated waters at bench scale. The first raw water had a high bromide ion concentration, a high ozone demand, and was highly colored. Based on experimental findings from the first water, the second water was selected as a model water in which more controlled experiments were performed. The waters were treated with the MIEX resin using jar test procedures to find the optimal MIEX dosage based upon the removal of ultraviolet (UV)-absorbing substances, dissolved organic carbon (DOC), and bromide. The optimal resin dosage was chosen for bulk MIEX treatment and subsequent ozonation in a semi-batch reactor. The ozone demand and formation of bromate were analyzed as a function of ozone dosage and dissolved ozone concentration for the MIEX pre-treated water, and compared to the results obtained by ozonating the water without MIEX pre-treatment. The results indicate that pre-treatment of the water with the MIEX resin significantly reduces total organic carbon, DOC, UV absorbance, color, and to some extent, bromide. MIEX pre-treatment of the water prior to ozonation substantially lowered the ozone demand and formation of bromate during subsequent ozonation.

Bromates↗
PubMed2005

Adsorptive ozonation of 2-methylisoborneol in natural water with preventing bromate formation.

This paper presents an application of our newly developed adsorptive ozonation process using a high silica zeolite adsorbent (USY) for drinking water treatment. First, the adsorption of 2-methylisoborneol (2-MIB) on USY in a river water/pure water mixture was clarified by a batch-type adsorption experiment. The results showed that 2-MIB was adsorbed on USY; however, almost all of the adsorbed 2-MIB was desorbed over time. The desorption rate was increased with the ratio of river water to pure water, indicating that compounds dissolved in the river water, such as natural organic matter (NOM), prevent the adsorption of 2-MIB on USY. Second, the ability of the river water to consume ozone was confirmed in an experiment using a USY-packed column reactor. The ozone consumption was obviously increased by the presence of USY, indicating that USY-adsorbing compounds dissolved in the river water (probably small size NOM) consumed the ozone. However, the rapid ozone consumption was occurred by 6-8 s in the retention times when 3.14-4.38 mgL(-1) of water dissolved ozone was fed, this rapid ozone consumption lasted no more than these times. This result revealed that the rapid consumption of ozone by the adsorptive compounds in our process could be avoided within a certain retention time (6-8 s; especially for the river water used in this study) when enough concentration of ozone (3.14 mgL(-1) or more; same above) was supplied. We therefore performed a trial in which 2-MIB dissolved in river water was continuously decomposed using a USY-packed column with various ozone concentrations. In the process, the adsorptive compound dissolved in the river water adsorbed and reacted with ozone in the parts of the apparatus upstream of the column, while the adsorption and decomposition of 2-MIB took place in the parts of the apparatus downstream of the column. This resulted in a sufficient 2-MIB decomposition with minimizing bromate ion formation.

Adsorption↗
PubMed2005

Ozonation of the marine dinoflagellate alga Amphidinium sp.--implications for ballast water disinfection.

Ozone has been investigated for its potential to remove marine dinoflagellate algae from ships' ballast water. Dinoflagellate algae, Amphidinium sp. isolated from the Great Barrier Reef, Townsville, Australia were used as indicators since these produce a type of cyst that is difficult to inactivate, but are relatively easy to culture. The ozonation experiments have demonstrated a high ozone demand for inactivation of the algal cultures, which increases as the culture ages. The main ozone demand in seawater is due to its reaction with bromide to form bromine compounds. The non-bromide ozone demand has been estimated by measuring the residuals produced after various doses of ozone. The Amphidinium sp. show an unexpected response to both ozonation and bromination, with an instantaneous inactivation of the organisms for all doses that produced an oxidant residual in the seawater, followed by an effect of the disinfection residual. The standard design procedure of comparing Ct will not be effective for predicting the response of the organism to varying dose, C, and contact time, t, and a plot of ozone produced oxidant residual against organism inactivation for various contact times is proposed for design purposes. High doses of ozone (5-11 mg/L) and up to 6h of residual contact were required for a 4-log inactivation of the Amphidinium sp. Ozonation is likely to be a difficult technology to implement for organisms with this ozone requirement in combination with characteristics of ballast tanks, which contain areas of sediments high in detritus and areas of corrosion.

Animals↗
PubMed2006

Inactivation of Escherichia coli by ozone under bench-scale plug flow and full-scale hydraulic conditions.

To determine the disinfection efficacy of ozonation, water companies can apply several disinfection calculation methods. The goal of this study was to evaluate the use of the T10 and continuous stirred tank reactor (CSTR) method to extrapolate inactivation rates of ozone sensitive microorganisms observed in laboratory tests to full-scale ozonation in drinking water treatment. The inactivation efficacy of the ozonation at the Amsterdam water treatment works was assessed by determining Escherichia coli concentrations in large volume samples before and after ozonation over a period of 1 year. The inactivation of dosed E. coli WR1 was tested in a bench-scale dissolved ozone plug flow reactor (DOPFR) on the same feed water as the full-scale ozonation in which a concentrated ozone solution in Milli-Q water was dosed. Applying the T10 method on the inactivation rates observed in the DOPFR strongly overestimated the inactivation capacity of the full-scale ozonation. The expected inactivation based on the CSTR method (LT2ESWTR) approached the observed inactivation at full-scale. Therefore, the CSTR method should be preferred to calculate inactivation of ozone sensitive organisms such as E. coli, viruses, Giardia and Campylobacter by full-scale ozonation.

Disinfection↗
PubMed2003

Purification of cork processing wastewaters by ozone, by activated sludge, and by their two sequential applications.

Wastewaters generated in the cork processing industry were treated in continuous reactors by means of single treatments separately-a chemical ozonation and an activated sludge system-and then by both sequential processes-ozonation followed by aerobic degradation, and aerobic degradation followed by ozonation. The removals obtained in the ozonation alone were 12-54%, 65-81%, and 55-89% for the COD, total phenolics, and absorbance at 254 nm, respectively, while the consumed ozone yield ranged from 40% to 61%, and the biodegradability (BOD(5)/COD) varied from an initial 0.60 to final values between 0.68 and 0.93. The optimum hydraulic retention time and ozone partial pressure were 3 h and 3 kPa, respectively. The stoichiometric ratio was 0.56 g of organic substrate degraded per g of ozone consumed, while the rate constants obtained for the ozone disappearance and for the organic matter degradation were 4490 L g COD(-1) h(-1) and 1970 L g O(3)(-1)h(-1) respectively. The presence of hydrogen peroxide or UV radiation in addition to ozone increased the values of organic matter removal as well as the stoichiometric ratio and the rate constants. The aerobic treatment by the activated sludge system yielded COD removals between 13% and 37% for hydraulic retention times between 24 and 96 h, and the Contois model gave values of q(max)=0.14 g COD g VSS(-1)h(-1) and K(1)=22.6 g COD g VSS(-1) for the main kinetic parameters. The sequential processes increased the substrate removal efficiencies in comparison with the individual processes. These enhancements were greater in the aerobic degradation-ozonation sequence than in the ozonation-aerobic degradation sequence.

Bioreactors↗
PubMed2002

An evaluation of ozone exposure metrics for a seasonally drought-stressed ponderosa pine ecosystem.

Ozone stress has become an increasingly significant factor in cases of forest decline reported throughout the world. Current metrics to estimate ozone exposure for forest trees are derived from atmospheric concentrations and assume that the forest is physiologically active at all times of the growing season. This may be inaccurate in regions with a Mediterranean climate, such as California and the Pacific Northwest, where peak physiological activity occurs early in the season to take advantage of high soil moisture and does not correspond to peak ozone concentrations. It may also misrepresent ecosystems experiencing non-average climate conditions such as drought years. We compared direct measurements of ozone flux into a ponderosa pine canopy with a suite of the most common ozone exposure metrics to determine which best correlated with actual ozone uptake by the forest. Of the metrics we assessed, SUM0 (the sum of all daytime ozone concentrations > 0) best corresponded to ozone uptake by ponderosa pine, however the correlation was only strong at times when the stomata were unconstrained by site moisture conditions. In the early growing season (May and June). SUM0 was an adequate metric for forest ozone exposure. Later in the season, when stomatal conductance was limited by drought. SUM0 overestimated ozone uptake. A better metric for seasonally drought-stressed forests would be one that incorporates forest physiological activity, either through mechanistic modeling, by weighting ozone concentrations by stomatal conductance, or by weighting concentrations by site moisture conditions.

California↗
PubMed2000

The revision of the air quality legislation in the european union related to ground-level ozone.

Complying with the obligation in the current ozone directive, the European Commission came forward in 1999 with a strategy to combat tropospheric ozone together with a proposed revision of the air quality legislation for this pollutant. As a daughter legislation under the 1996 Framework Directive on Air Quality, the proposed ozone daughter directive defines for the first time (interim) air quality targets for ozone to be attained by 2010, complemented by long-term objectives for ozone based on the guideline values of the World Health Organisation. It also sets out enhanced requirements for monitoring and assessment of ozone concentrations, as well as minimum criteria for appropriate information of the public about the measured air pollution. In the past, abatement strategies against air pollution consisted of concrete obligations for controlling emissions derived solely on the basis of technical and economic aspects, covering specific types of installations or activities, thus with no direct quantitative relationship to the level of air pollution let alone to its effects. In compensating this deficit, the Commission presented, as a complement to the existing sectoral legislation, a proposal for a directive on national emission ceilings (NEC) which quantifies emission targets for every Member State to bring its total precursor emissions by 2010 down to levels being considered as necessary to achieve everywhere on a regional scale the air quality targets set in the ozone daughter directive. As the core element of the ozone abatement strategy, the national ceilings for emissions of sulfur dioxide (SO(2)), nitrogen oxides (NO(x)), ammonia (NH(3)) and volatile organic compounds (VOC) were derived from a cost-effectiveness analysis integrating information on economic, technical, physical and biological aspects of ozone pollution and abatement. This integrated assessment considers the potential and costs for further emission control in the various economic sectors in the Member States and combines this with information on ozone formation and transport processes in the atmosphere and with indicators for the impact of ozone on human health and environmental. Reflecting the discussions with Member States and stakeholders, a number of decisive steps in the process of deriving the national emission ceilings are presented here: the way of framing interim objectives, how to choose an appropriate ambition level, aspects of how to cope with uncertainties in the model and the input data and how to treat extreme meteorological situations and resolve problems in the spatial distribution of the interim objectives given the different size of countries. Finally, the paper explains the scenario underpinning the proposed national emission ceilings, its environmental gains and the distribution of cost incurring for emission control measures in Member States.

Air Pollution↗
PubMed2003

Ozone and its current and future application in the food industry.

The food industry is interested considerably in using ozone to enhance the shelf-life and safety of food products and in exploring new applications of the sanitizer. This interest was recently accompanied by a US governmental approval of ozone for the safe use, in gaseous and aqueous phases, as an antimicrobial agent on food, including meat and poultry. Ozone has a strong microbicidal action against bacteria, fungi, parasites and viruses when these microorganisms are present in low ozone-demand media. Readily available organic constituents in food, however, compete with microorganisms for applied ozone and thus efficacy of the treatment is minimized. Ozone is suitable for washing and sanitizing solid food with intact and smooth surfaces (e.g., fruits and vegetables) and ozone-sanitized fresh produce has recently been introduced in the US market. Use of ozone to sanitize equipment, packaging materials, and processing environment is currently investigated. Efforts to decontaminate bean sprouts and remove biofilm with ozone have not been successful. The antimicrobial efficacy can be enhanced considerably when ozonation is combined with other chemical (e.g., hydrogen peroxide) or physical (e.g., ultraviolet radiation) treatments. Mechanical action is also needed as a means to dislodge microorganisms from the surface of food and expose them to the action of the sanitizer. The food industry also is interested in using ozone to decontaminate processing water and decrease its chemical and biological oxygen demand. This application improves the reusability of processing water and allows for environment-friendly processing operations.

Bacteria↗
PubMed2002

Comparison of source apportionment and source sensitivity of ozone in a three-dimensional air quality model.

The ozone source apportionment technology (OSAT) estimates the contributions of different sources to ozone concentrations using a set of tracers for NOx, total VOCs, and ozone and an indicator that ascribes instantaneous ozone production to NOx or VOCs. These source contributions were compared to first-order sensitivities obtained by the decoupled direct method (DDM) for a three-dimensional simulation of an ozone episode in the Lake Michigan region. The cut-point for the OSAT indicator between VOC- and NOx-sensitive ozone production agrees well with the DDM sensitivities to VOC and NOx. In a ranking of the most important contributors to ozone concentrations >80 ppb, the OSAT and DDM results agreed on four of the top five contributors on average. The spatial distributions of the sensitivities and source contributions are similar, and the OSAT and DDM results for ozone >80 ppb correlate well. However, the source contributions ascribe substantially less relative importance to anthropogenic emissions and greater relative importance to the boundary concentrations than do the sensitivities. In regions where NOx inhibits ozone formation and the sensitivity is negative, the source contribution is small and positive. For the same subdivision of the emissions, the OSAT is 14 times faster than the DDM, but the DDM has greater flexibility in defining which emissions to include and generates results for species other than ozone. The first-order sensitivities explain, on average, 70% of the ozone concentrations.

Air Pollutants↗
PubMed2005

Analysis of atmospheric sesquiterpenes: sampling losses and mitigation of ozone interferences.

Atmospheric standards containing parts-per-billion levels of 14 semivolatile hydrocarbon compounds, including eight sesquiterpenes (SQTs) (longipinene, alpha-copaene, isolongifolene, alpha-cedrene, trans-caryophyllene, aromadendrene, alpha-humulene, delta-cadinene), two oxidized sesquiterpenoids (cisnerolidol, trans-nerolidol), one biogenic ketone (geranylacetone) and three aromatic compounds (1,3,5-triisopropylbenzene, diphenylmethane, nonylbenzene), were collected onto four solid adsorbent materials at increasing ozone mixing ratios (0-100 ppbv 03) for analysis by thermodesorption-gas chromatography. Substantial sampling losses of up to >90% were found for the most reactive SQT, even at the lowest ozone level investigated of 20 ppbv. Loss rates from the ozone-SQT reaction were used to derive estimates of gas-phase ozone reaction rate constants for longipinene, alpha-copaene, isolongifolene, geranylacetone, aromadendrene, delta-cadinene, cis-nerolidol, and transnerolidol. Three different ozone mitigation techniques were investigated to prevent these sampling losses. These strategies included (a) placing glass fiber filters impregnated with sodium thiosulfate (Na2S2O3) into the sampling line, (b) titration of ozone in the sampling stream with nitric oxide (NO), and (c) catalytically removing ozone with a commercially available manganese dioxide (MnO2) catalyst. All three techniques reduced ozone-mixing ratios from 100 ppbv to <0.6 ppbv at sampling flow rates of 1 L min(-1). When the Na2S2O3 filters and the NO-titration techniques were applied, SQT loss rates decreased from 25-60% to 0-5% for most SQT compounds and from >90% to approximately 10-50% for the two most reactive compounds at ozone mixing ratios of up to 100 ppbv. The commercial manganese dioxide scrubber, however, caused complete analyte losses (>98%) even at 0 ppbv ozone. These results underline the need and present applicable techniques for removal of ozone in air samples for SQT analysis by solid adsorption techniques.

Adsorption↗
PubMed2002

Skin cancer and ultraviolet-B radiation under the Antarctic ozone hole: southern Chile, 1987-2000.

BACKGROUND: Punta Arenas, Chile, the southernmost city in the world (53 degrees S), with a population of 154,000, is located near the Antarctic ozone hole (AOH) and has been regularly affected by high levels of ultraviolet-B (UV-B) radiation each spring for the last 20 years. Large increases in UV-B associated with the AOH have been measured with increases in UV-B at 297 nm of up to 38 times those of similar days with normal ozone. Recently we reported significant increases in sunburns during the spring of 1999 on days with low ozone because of the AOH. METHODS: A surveillance of skin cancers occurring from 1987 to 2000 was performed. Age, sex, location, type of skin cancer and skin phototype were recorded. A Brewer Spectrophotometer was used in order to obtain in situ measurements of ozone and UV-B. Total Ozone Mapping Spectrometer (TOMS) data from National Aeronautics and Space Administration (NASA) was used in order to establish pre-ozone hole climatology. RESULTS: Ozone levels as low as 145 DU (Dobson Units) were recorded, a 56% decrease in ozone, and UV-B levels up to 4.947 J/m2. These levels are close to summertime levels at mid latitudes. For the 14-year period--from 1987 to 2000--173 cases of skin cancer were diagnosed, 65 during the first 7 years, 108 during the second, an increase of 66%. Cutaneous malignant melanoma (CMM), 19% of the cases, increased by 56%, raising the rate from 1.22 to 1.91 per 100,000. Non-melanoma skin cancer (NMSC), 81% of the total, increased the rate from 5.43 to 7.94 per 100 000 (P < 0.05), a 46% increase. Patients with CMM and NMSC had skin phototypes I-II in 59% and 54% of cases, respectively. Days with more than 25% ozone loss occurred in 143 days during the last 20 springs. Significant increases of UV-B were observed under ozone hole conditions, especially around 300 nm, the most carcinogenic wavelengths. CONCLUSIONS: Highly unusual ozone loss and UV-B increases have occurred in the Punta Arenas area over the past two decades resulting in the non-photoadapted population being repeatedly exposed to an altered solar UV spectrum with a greater effectiveness for erythema and photocarcinogenesis. This phenomenon has not previously been reported over other populated areas and an additional increase in the skin cancer rate attributable to the AOH may be occurring. Research on the clinical and subclinical impact of these abnormalities is urgently needed.

Aged↗
PubMed2006

The search for signs of recovery of the ozone layer.

Evidence of mid-latitude ozone depletion and proof that the Antarctic ozone hole was caused by humans spurred policy makers from the late 1980s onwards to ratify the Montreal Protocol and subsequent treaties, legislating for reduced production of ozone-depleting substances. The case of anthropogenic ozone loss has often been cited since as a success story of international agreements in the regulation of environmental pollution. Although recent data suggest that total column ozone abundances have at least not decreased over the past eight years for most of the world, it is still uncertain whether this improvement is actually attributable to the observed decline in the amount of ozone-depleting substances in the Earth's atmosphere. The high natural variability in ozone abundances, due in part to the solar cycle as well as changes in transport and temperature, could override the relatively small changes expected from the recent decrease in ozone-depleting substances. Whatever the benefits of the Montreal agreement, recovery of ozone is likely to occur in a different atmospheric environment, with changes expected in atmospheric transport, temperature and important trace gases. It is therefore unlikely that ozone will stabilize at levels observed before 1980, when a decline in ozone concentrations was first observed.

Atmosphere↗
PubMed2002

Interaction of ozone and negative air ions to control micro-organisms.

AIMS: The aims of this study were to investigate the effect of ozone and/or negative air ions (NAI) on the viability of bacteria. METHODS AND RESULTS: Dilute cell suspensions of Pseudomonas fluorescens, Erwinia carotovora pv. carotovora and Escherichia coli were inoculated onto agar and subsequently exposed to ozone and/or NAI. Ozone concentration was maintained at 100 +/- 5 nl l-1 and NAI at 106 ml-1. When exposed to a combination of ozone and NAI, viability among all three bacterial species decreased more rapidly when they were inoculated onto potato dextrose agar (PDA) than onto nutrient agar (NA). A subsequent test examined the effect of ozone and NAI alone or in combination on the bacteria inoculated onto PDA only. Treatment with NAI alone had no killing effect on any of the bacterial species. However, a strong interaction between ozone and NAI was observed. Pseudomonas fluorescens was most susceptible to the combined treatment. Cell viability was reduced to 0.7% after 6 h, while 76% of the cells remained viable when exposed to ozone alone. Viability of Erwinia carotovora pv. carotovora was reduced to 4% after 6 h in the combined treatment compared with 69% when exposed to ozone alone. Escherichia coli was relatively more resistant to the combined treatment; viability was reduced to 40% after 11 h compared with 70% in the ozone alone treatment. CONCLUSIONS: A strong synergism between ozone and NAI on bacterial cell death was found, but the degree of this effect varied depending on bacterial species. SIGNIFICANCE AND IMPACT OF THE STUDY: The synergism of ozone with NAI may provide an effective method of reducing food-borne disease and decay of fresh produce.

Air Microbiology↗
PubMedDate not supplied

The pathobiology of ozone-induced damage.

Ozone remains one of the three most important air pollutants worldwide, yet little direct documented evidence of its genotoxicity exists. The interest in the pathology of ozone exposure and the molecular events that underlie its course stems from DNA damage caused by oxygen stress including hydroxyl radicals, superoxide, singlet oxygen, and hydrogen peroxide. Although the tissue damage associated with ozone inhalation occurs at both the conducting airway and the alveolus, the cellular and mechanistic processes underlying these events are less well understood. Ozone leads to the oxidative decomposition of polyunsaturated fatty acids. Ozone also depresses DNA replication in V79 Chinese hamster lung fibroblasts in a dose-dependent fashion (concentration, 1-10 ppm), which indicates that ozone or its reaction products may interact directly with DNA and inhibit replication. Ozone also linearizes circular DNA and induces ozone-sensitive mutant and pneumocytes to repair its DNA. DNA adducts have been implicated in aging, cellular transformation, mutagenesis, carcinogenesis, and cell death; DNA adducts are products of free radical damage. These events are all common in ozone exposure. Finally, DNA-binding proteins are potent positive and negative regulators, enhancers, or silencers of gene expression. Part of their action may be related to their ability to initiate the binding sequence of DNA transcription proteins and thus form complexes. Alteration of DNA-binding sites by ozone adducts may effect mRNA transcription due to altered binding by DNA-binding proteins. This altered transcription has been shown to effect growth factors involved in collagen and matrix regulation. The present review will address some of the complexities involved in ozone exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗