Duration Of Ozone Exposure Research Articles

Quality assessment of different ozone treatments to extend shelf-life of banana (Musa acuminata)

This study investigated the physicochemical parameters before and after ozone treatment of bananas (Musa acuminata) known as “Hom Thong” in Thailand. The effects of different durations of ozone exposure and storage temperatures were used to evaluate the effectiveness of ozone treatment in extending shelf life, as shown by the changes in surface morphology, peel color index, total titratable acidity, and weight loss of the Hom Thong sample. The duration of ozone exposure was 10 and 60 min every 4 h during an 18-day storage period at a flow rate of 15 L/min, while the storage temperatures were 18 and 30 °C (ambient temperature), respectively. The quality at the beginning of the storage period and after 3, 6, 9, 12, 15 and 18 days of storage was investigated using the physicochemical parameters. The result showed that the quality was better at 18 °C storage temperature, but the color index of the peel had changed rapidly. When the results were available on the 12 day of storage, mold growth started in the untreated sample but was absent in the Hom Thong sample treated with ozone. Therefore, it can be concluded that ozone treatment is an alternative process that can extend the shelf life of bananas (Hom Thong) with great potential.

Uncertainties Influencing Health-Based Prioritization of Ozone Abatement Options

The primary goal of air quality management is protection of human health. Therefore, formulation of ground-level ozone mitigation policies could be informed by considering not just attainment of regulatory standards but also how control measures benefit public health. However, evaluation of health impacts is complicated by uncertainties associated with photochemical modeling and epidemiological studies. This study demonstrates methods to characterize uncertainties influencing health-benefits estimation of ozone reduction (averted premature mortalities due to short-term exposure) in the Dallas-Fort Worth (DFW) region. Uncertainty in photochemical modeling and the selection of temporal metric (duration of ozone exposure) for concentration-response relationships can each affect the health-based prioritization of ozone control options. For example, deterministic results (neglecting uncertainties) based on 8-h daily maximum ozone reduction shows DFW anthropogenic NO(x) controls to yield 9.23 times as much benefit per ton as VOC controls. However, the rankings reverse under 5.7% of the cases (including 2.8% cases that exhibit incremental mortalities due to NO(X) control) when uncertainties in the photochemical model are considered. Evaluated ozone exposure on a 24-h rather than an 8-h basis also reverses the rankings.

Bone cell viability on collagen immobilized poly(3‐hydroxybutrate‐co‐3‐hydroxyvalerate) membrane: Effect of surface chemistry

AbstractThe effect of surface chemistry on proliferation and morphology of bone cells cultured on surface modified poly(3‐hydroxybutrate‐co‐3‐hydroxyvalerate) (PHBV) and untreated PHBV was evaluated. The surface of cast PHBV film was physically and chemically immobilized with collagen. For preparing chemically immobilized collagen surface, PHBV film was ozone treated followed by grafting of PMAA chains and the immobilization of collagen. The surface roughness and hydrophilicity of PHBV film were determined by atomic force microscopy (AFM) and contact angle measurements, respectively. It was found that the duration of ozone exposure and monomer concentration used for grafting PMMA chains influenced the amount of collagen immobilized. The cell proliferation on PHBV surfaces with chemically and physically immobilized collagen was compared with untreated PHBV using 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide (MTT) assay. The bone cell activity on chemically and physically immobilized collagen PHBV films was found to be 246 and 107% for UMR‐106 and 68 and 9% for MC3T3 cell lines, respectively. Although the results are very preliminary, the chemically grafted collagen on PHBV surface provided a favorable matrix for cell proliferation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2445–2453, 2004

Stable free radicals in ozone-damaged wheat leaves

Chlorophyll fluorescence measurements were performed on attached leaves of wheat plants (Triticum aestivum L. cv. Nandu) that were exposed to ambient air and to air supplemented with 80 and 120nmol mol-1 ozone. Decreases in the “current photochemical capacity” were observed that were dependent on both the ozone concentration and duration of exposure. Electron paramagnetic resonance (EPR) spectra on freeze-dried samples from the same batches of plants showed the presence of an unidentified stable free radical, whose spectra had similarities to that of the ubisemiquinone radical. The intensity of this radical signal increased with the duration of ozone exposure in leaves that received an additional 120nmol mol-1 ozone. In contrast, with exposure to air with 80nmol mol-1 added ozone, there was little if any change in free radical signal intensity over the 4 week period of the experiment. The increase in intensity of the EPR signal occurred later than the chlorophyll fluorescence changes, which suggests that it is associated with permanent leaf damage.

Method of measuring deposition of unlabeled monodisperse microspheres in rat lungs

A system to simultaneously measure the total deposition of four different sizes of monodisperse microspheres in normal and damaged lungs of rats was developed and tested. The system reproducibly measured the deposition of microspheres in control rats, and the procedure was shown to be sufficiently sensitive to measure ozone-induced changes in deposition rates. Rats exposed to 1.2 ppm ozone 6 h/d for 2 consecutive days showed greater deposition of the 1.09-micron-, 2.02-micron-, and 2.99-micron- but not of the 0.48-micron-diameter microspheres when compared to controls. After 8 consecutive days of exposure to the same concentration of ozone, there were no differences in deposition rates between control and ozone-exposed rats. Respiratory physiology and lung histopathology data provided evidence that subtle changes in the airway architecture and/or aerodynamics were likely to be responsible for the differential deposition rates as a function of the duration of ozone exposure.

Surface-tension measurements of pulmonary lavage from ozone-exposed rats.

Ozone, an important component of photochemical air pollution, has been shown to cause morphological and functional changes in the lung after acute, high-level exposure in controlled animal studies. Previous exposures of rats to 0.8 ppm ozone for 18 h showed trends toward decreased lung volumes, as well as modifications in phospholipid composition of lung lavage fluid. These results suggested that exposure to ozone may have diminished the ability of surfactant to reduce surface tension. The purpose of this pilot study was to determine if changes in the surface tension of lavaged pulmonary surfactant occur with ozone exposure. The lavage fluid from rats exposed to ozone at 0.8 ppm for 18 h had a 360% increase in protein and a 30% increase in lipid phosphorus content. Lung lavage samples from ozone-exposed rats were more potent in reducing surface tension as measured on a Wilhelmy plate balance. This difference was evident whether determined with half the total lavage or with equivalent microgram amounts of lipid phosphorus. It is concluded that at this dose and duration of ozone exposure, contrary to our hypothesis, surface-tension-lowering ability of surfactant increases and therefore does not appear to be a contributory factor in the previously observed changes in pulmonary function.

Salinity‐Ozone Interactions on Pinto Bean: Integrated Response to Ozone Concentration and Duration

AbstractThis investigation was conducted to determine the integrated effects of concentration and duration of ozone exposure on the injury, growth, and mineral composition of pinto bean (Phaseolus vulgaris L.) during rapid vegetative growth and to evaluate the interactive effects of salinity.Plants were grown in controlled environment chambers in non‐saline and two saline nutrients solution cultures having osmotic potentials of −0.4, −2.4, and −4.4 bars, respectively. Ozone‐free plants were compared with plants treated daily for 2 weeks with ozone doses of from 0.15 to 0.90 ppm‐hour.Plant injury and reduction in growth were sigmoidal functions of ozone dose. Plant tolerance thresholds were found for both concentration and duration of ozone exposure. Daily exposures above threshold levels produced cumulative injury that progressed from the primary leaves to subsequent trifoliate leaves. Although salinity suppressed plant growth, it extended the tolerance threshold for duration of ozone exposure and significantly reduced the injury by ozone. Ozone decreased Ca, Mg, K, and N contents of the leaves, increased stem contents of these elements, and had relatively little effect on root contents. However, no serious nutritional imbalances were observed.