A Study of Trace Metals in Myocardial Infarction

The chemistry of sulfite-bisulfite (the hydrate of sulfur dioxide in mammalian plasma and serum was investigated in vitro and in vivo. The longevity of sulfite in contact with mammalian plasma and known components of blood was determined by adaptation of a colorimetric method for sulfite analysis. Evidence from all experiments indicated that, under physiological conditions, sulfite reacts reversibly with disulfide bonds present in the plasma resulting in formation of S-sulfonates (sulfitolysis). Free sulfite was not detected in plasma of rabbits immediately following exposure to approximately 25 ppm SO₂, but there was good evidence for substantial elevation of plasma and serum S-sulfonate content. Reactivity of sulfite with plasma constituents may protect many body tissues from the insult of relatively high concentrations of sulfite and may facilitate prolonged exposure to very low levels of sulfite.     

Response of ciliated epithelium to ozone and sulfuric acid

The effects of ozone (O₃), sulfuric acid (H₂SO₄), and their interaction on ciliary activity were investigated. Following in vivo exposure to various concentrations of O₃ and H₂SO₄, ciliary activity of isolated tracheal ring cultures was microscopically determined under stroboscopic illumination. Assay of tracheal rings immediately after a 2-hr exposure to 880 μg H₂SO₄/m³ showed a significant decrease (P < 0.0001) in ciliary beating frequency from controls. Following 72 hr in vitro maintenance, there was still a significant depression (P < 0.01) in ciliary activity of treatment cultures. In vivo recovery studies indicated that ciliary activity had returned to the normal range 72 hr after exposure. Exposure to 196 μg O₃/m³ for 3 hr resulted in no significant difference from controls in ciliary activity. Experiments designed to investigate the effects of a sequential exposure to O₃ followed by H₂SO₄ indicated a significant decrease (P < 0.05) in the ciliary beating frequency of exposed animals which was less than that observed with H₂SO₄ alone. As indicated by the results of these studies, combined action experiments are extremely relevant in assessing the toxicity of environmental pollutants.     

Cytotoxic effects of sulfuric acid mist, carbon particulates, and their mixtures on hamster tracheal epithelium.

Hamster tracheal tissue was used to study the effects of H₂SO₄ mist, carbon particles, and mixtures of the two on cilia beating frequency and morphological alterations of respiratory epithelium. Hamsters were exposed for 3 hr to 1.1 mg/m³ H₂SO₄ (mean size, 0.12 μm) and 1.5 mg/m³ carbon (mean size, 0.3 μm) particle aerosols alone or in combination. Trachea of animals exposed in vivo to the mixture and held in vivo showed cytotoxic effects in the epithelium that were greater than those produced by either the acid mist or carbon alone. In tracheas of hamsters exposed in vivo and maintained in vitro the damage produced by acid mist—carbon mixture did not differ significantly from that produced by acid mist per se but was greater than that observed after exposure to carbon. Organ cultures of tracheal rings exposed for 3 hr to a 1:10⁶ dilution of concentrated H₂SO₄ and 100 μg/ml carbon produced epithelial damage in vitro similar to that seen in in vivo exposures. The extent of recovery over a period of 72 hr was also studied following different combinations of in vivo and in vitro exposure and/or maintenance.     

Sulphur-dioxide induced bronchial hyperreactivity against acetylcholine

Summary The effect of sulphur-dioxide (SO₂) on the bronchial reactivity against acetylcholine (ACH) is carried out on 25 dogs. The dogs were exposed initially to acetylcholine aerosol, then to SO₂ for 1 hr and again to ACH. 3 such cycles were repeated. The concentration of SO₂ used were 1, 2, 5 and 10 ppm and the controls were given room air in place of SO₂.The parameters studied were intrathoracic pressure as the indicator of bronchoconstriction, blood oxygen and carbon-dioxide, tidal volume, respiratory rates and arterial blood pressure. All the SO₂ exposed animals have shown a significant increase of bronchial sensitivity than those of the controls. Maximum sensitization was induced by 2 ppm. The reaction provoked by 1 and 5 ppm were almost of the same order and little smaller than 2 ppm but greater than those produced by 10 ppm. The peak reactions against ACH observed for 1, 2 and 5 ppm were 3, 2 and 1 hr of exposure, respectively. After attaining the peak points, the reactions declined in all the 3 groups. But no such trend was obtained for those animals exposed to 10 ppm of SO₂.The role of small concentration of SO₂ as bronchial sensitizing agent against ACH is discussed.Diese Forschung wurde mit Unterstützung des Vereins zur Untersuchung von Einwirkungen der Luftverschmutzung auf die Volksgesundheit e.V. durchgeführt.     

Influence of pH on inhibition of bacteria, fungi, and coliphages by bisulfite and sulfite.

Studies were performed to determine the effects of bisulfite (HSO₃^?) and sulfite (SO₃^2?), the anionic solubility products of sulfur dioxide (SO₂), on the growth of bacteria and fungi and on the survival of a coliphage. Although differential sensitivities to these anions were noted among the test microorganisms, HSO₃ was always more inhibitory than SO₃^2?. The inhibitory effects of HSO₃^? and SO₃^2? were pH dependent: The lower the pH, the greater their toxicity. Consequently, when evaluating the overall effects of pollution by SO₂ and the resultant acid rain on the biosphere, attention must be focused on the anionic solubility products of SO₂ and on the impact of the pH of the receiver environment on their toxicity to microbes.     

Detoxication of zinc and cadmium by the freshwater protozoan Tetrahymena pyriformis: I. The effect of water hardness

Estimated 8-hr LC₅₀ values of zinc and cadmium were less than 1 ppm in the absence of soluble calcium and magnesium, but were raised, for example, to 24 ppm of zinc and 19 ppm of cadmium by the addition of calcium plus magnesium at a concentration (500 ppm) equivalent to that of very hard water. Experiments with ⁶⁵Zn showed that uptake of this element from sublethal concentrations over 8 hr was reduced from approximately 50 × 10^?2 μg liter^?1 to 10 × 10^?2 μg liter^?1 per 10⁶ cells by the addition of 500 ppm of calcium and magnesium. Diminished uptake may partly explain the antagonism observed in the toxicity tests.     

Spatio-temporal variations of sulfur dioxide concentrations in industrial and urban area via a new statistical approach

Sulfur dioxide (SO₂) is considered the most widespread pollutant that threatens environmental and human health. The purpose of this study is to propose a new method for evaluating the spatial variation of SO₂ levels in the Metropolitan Area of Porto Alegre (MAPA). This method included use of Chi-square test to better identify the origin of SO₂ sources. Additionally, results of the different methods applied allowed to analyze the temporal SO₂ levels and their association with meteorological parameters. SO₂ at five sampling sites (Esteio, Canoas, Charqueadas, Triunfo, and Gravataí) were measured during 2010–2015; using fluorescence SO₂ automated analyzers. Results showed that Charqueadas had the highest average concentration (~?15 μg m^?3), followed by Triunfo (13 μg m^?3), Esteio (6 μg m^?3), Canoas (3 μg m^?3), and Gravataí (2 μg m^?3). Chi-square test applied to SO_2, and wind direction quadrants showed significant contribution of local emission sources. Seasonal variation revealed higher SO₂ levels on cold days for most of the studied sites, except for Esteio site. Day-wise variations revealed higher SO₂ concentration on weekdays than weekends for Esteio and Canoas sites, indicating traffic influence especially during the rush-hours. Annual averages analysis identified an increasing trend in SO₂ concentrations, implying that applied emission control systems and technological improvement of engines and fuels were not sufficient and thus points out a need for better subsidies mechanisms to pollutant control and effective emission reduction strategies that decision makers, including environmental agencies, must make priority by considering the local realities.     

(Bi)sulfite Oxidation by Copper,Zinc-Superoxide Dismutase: Sulfite-Derived,Radical-Initiated Protein Radical Formation

Background

Sulfur dioxide, formed during the combustion of fossil fuels, is a major air pollutant near large cities. Its two ionized forms in aqueous solution, sulfite and (bi)sulfite, are widely used as preservatives and antioxidants to prevent food and beverage spoilage. (Bi)sulfite can be oxidized by peroxidases to form the very reactive sulfur trioxide anion radical (^•SO₃⁻). This free radical further reacts with oxygen to form the peroxymonosulfate anion radical (⁻O₃SOO^•) and sulfate anion radical (SO₄^{• −}).

Objective

To explore the critical role of these radical intermediates in further oxidizing biomolecules, we examined the ability of copper,zinc-superoxide dismutase (Cu,Zn-SOD) to initiate this radical chain reaction, using human serum albumin (HSA) as a model target.

Methods

We used electron paramagnetic resonance, optical spectroscopy, oxygen uptake, and immuno-spin trapping to study the protein oxidations driven by sulfite-derived radicals.

Results

We found that when Cu,Zn-SOD reacted with (bi)sulfite, ^•SO₃⁻ was produced, with the concomitant reduction of SOD-Cu(II) to SOD-Cu(I). Further, we demonstrated that sulfite oxidation mediated by Cu,Zn-SOD induced the formation of radical-derived 5,5-dimethyl-1-pyrroline N-oxide (DMPO) spin-trapped HSA radicals.

Conclusions

The present study suggests that protein oxidative damage resulting from (bi)sulfite oxidation promoted by Cu,Zn-SOD could be involved in oxidative damage and tissue injury in (bi)sulfite-exacerbated allergic reactions.     

Time course of exercise-induced bronchoconstriction in asthmatics exposed to sulfur dioxide

Young adult asthmatic volunteers (N = 17) were exposed to 0.75 ppm sulfur dioxide (SO₂) for 3-hr periods, exercising vigorously for the first 10 min and resting thereafter. Specific airway resistance (SR_aw) and symptoms were recorded preexposure, immediately postexercise, and after 1, 2, and 3 hr of exposure. Symptoms and SR_aw were significantly increased after exercise, relative to preexposure measurements. Group mean SR_aw and symptom increases were no longer significant at 1 hr. In a few individuals, effects may have persisted for 2 hr or more. On separate occasions, comparable exposures were conducted, and forced expiratory spirometry was performed preexposure and postexercise, in addition to the other tests. Inclusion of spirometry did not significantly affect the other results. Spirometry and SR_aw showed nearly equal significance in changes postexercise. Thus, in general, asthmatics' bronchoconstriction induced by exercise in SO₂ seems to reverse quickly with rest, even if SO₂ exposure continues. Spirometry may be useful for studying pollution-induced bronchoconstriction when SR_aw measurements are impractical.     

Pollen mitosis and pollen tube growth inhibition by SO2 in cultured pollen tubes of Tradescantia

Mature pollen of Tradescantia paludosa Anders. Sax clone-3 was collected from greenhouse grown plants and desiccated in the dark for 4–5 hours. The pollen was sown on microslides coated with lactose agar medium (supplemented with 0.02% colchicine). Five minutes after sowing, pollen cultures were treated with various concentrations (0.075–2000 ppm) of SO₂ obtained from the chemical reaction between K₂S₂O₅ and HCl. Treatments were carried out in an airtight Plexiglas chamber throughout the full incubation period of 19 hours. Treated and control pollen cultures were fixed and stained in aceto-carmine or Feulgen reaction to determine the tube lengths and mitotic indices. Results of repeated experiments indicated that the values of mitotic indices dropped from the normal 38.7% in the control to the range of 24.3-3.8% when treated with 0.075–50.00 ppm of SO₂. Pollen tube growth was inhibited from the normal length of 1.5 mm in the control to the range of 800-100 μm when treated with 10–2000 ppm of SO₂. The inhibitory effect of SO₂ rpresumably resulted from physiological disturbance of the cell and severe damage to chromosomes of both generative and tube nuclei of the pollen tubes.     

Respiratory effects of mixed nitrogen dioxide and sulfur dioxide in human volunteers under simulated ambient exposure conditions

Normal and asthmatic volunteers (N = 24 and 19, respectively) were exposed to mixed nitrogen dioxide (NO₂) and sulfur dioxide (SO₂) in purified background air in an environmental chamber under conditions simulating an ambient pollution episode. The NO₂ concentration was 0.5 ppm; the SO₂ concentration was 0.5 ppm for normals and 0.3 ppm for asthmatics. Exposures lasted 2 hr and included intermittent exercise and heat stress. Control studies consisted of similar exposures to purified air alone. The mixed pollutant gases may have reacted chemically in the exposure chamber, but no appreciable amounts of sulfate or nitrate aerosol were detected there. Group mean lung function changes during exposure generally were not significantly different from control for normals or for asthmatics. Symptoms reported by the normal group showed a small significant overall increase during pollutant exposure and later the same day relative to the corresponding control periods; the asthmatics showed a small significant increase later in the day but not during exposure. The increased symptom reporting showed little consistency from subject to subject: there were small increases for most individual symptom categories evaluated, none of them statistically significant. The results are not sufficient to establish whether this slight and nonspecific clinical response should be attributed to the pollutant mixture or to some other aspect of the exposure protocol.     

Acid precipitation effect on anion transport of the Atkins Reservoir,Massachusetts

The anion concentration of the water in the precipitation reservoir and its watershed of Atkins Reservoir, Massachusetts was studied. In the precipitation study, the NO₃ ^– and SO₄ ^2– levels increased with a pH drop andvice versa, but the Cl^– was interfered with by regional marine air masses. The average pH of precipitation and the reservoir were 3.85 (SD=±0.89) and 6.08 (SD= ±0.18), respectively. The average alkalinity of the reservoir was very low; 0.88 mg/L CaCO₃ (SD= ±0.68). The precipitation and reservoir concentrations of anions were: F^– (0.5 and 0.2 ppm), Cl^– (2 and 4 ppm), and SO₄ ^2– (7 and 7.8 ppm), respectively. The NO₃ ^– level in the precipitation (4 to 6 ppm) was at least an order higher than the reservoir (0.2 to 0.4 ppm) and this was due to selective NO₃ ^– uptake by terrestrial plants. About 50% of the samples collected at the bottom of the reservoir were high in NO₃ ^– where organic decomposition would be expected. The response of the SO₄ ^2– and and Cl^– levels to pH drop in the reservoir inlet study followed a SO₄ ^2– retention-Cl^– release mechanism. The F^– concentration in the precipitation and reservoir was not dependent on pH changes. The lack of F^– in soil samples adjacent to the reservoir indicated that the F^– in the reservoir came primarily from precipitation.     

Experimental human exposure to carbon disulfide

Summary Six human volunteers were exposed to 10 and 20 ppm carbon disulfide at rest and to 3 and 10 ppm carbon disulfide under a 50 W level of physical exercise during four consecutive periods of 50 min. At the start of the experiments, at the end of the exposure periods and during the post-exposure period, urine was sampled and the concentration of 2-thiothiazolidine-4-carboxylic acid (TTCA) was determined. It was established that only a small percentage, ranging from 0.7 to 2.2% of the absorbed carbon sulfide was transformed into TTCA. The excretion rate of TTCA (mol TTCA h^–1) was found to be the best parameter in evaluating the respiratory uptake of carbon disulfide over a range of 37.9 to 163.3 mg CS₂ compared to the urinary concentration of TTCA (mole TTCA ml^–1) or the creatinine corrected concentration of TTCA (mmol TTCA mol^–1 creatinine). The total amount of TTCA (mol TTCA) excreted proved to be independent of the urinary flow (ml h^–1), the estimates of the individual fatty tissue content and the urinary pH. No correlation was found between the respiratory uptake of carbon disulfide (mg CS₂) and the excretion rate of TTCA within each exposure condition of 3, 10 or 20 ppm carbon disulfide, respectively.     

Toxicity of heavy metals and salts to eurasian watermilfoil (Myriophyllum spicatum L.)

The toxicity of various heavy metals and salts to Eurasian watermilfoil (Myriophyllum spicatum L.) was determined under controlled growth conditions. Toxicants were added to water or to soil in systems with and without woods earth in the substrate.Fifty precent inhibition of root weight occurred with concentrations of 0.25 ppm Cu⁺², 1.9 ppm Cr₂O₇ ^–2, 3.4 ppm Hg⁺², 2.9 ppm AsO₂ ^–1, 7.4 ppm Cd⁺², 2.5 ppm Al⁺³, 9.9 ppm Cr⁺³, 41.2 ppm Ba⁺², 21.6 ppm Zn⁺², 13.3 ppm NH₄ ⁺¹, 22.4 ppm CN^–1, 143 ppm B₄O₇ ^–2, 363 ppm Pb⁺², 10,228 ppm Na₂SO₄, and 8,183 ppm NaCl. Soil increased toxicity of Cr⁺² and Ba⁺² but decreased toxicity of Cr₂O₇ ^–2, Cu⁺², Cd⁺², Al⁺³, and Hg⁺². In distilled water, CaCl₂ increased toxicity of Cr⁺³ but not Cr₂O₇ ^–2.For most toxicants there was a consistent relationship between inhibition of length and inhibition of weight and between inhibition of roots and inhibition of shoots. However, Cr₂O₇ ^–2 disproportionately decreased dry weight, and Hg⁺² and Na₂SO₄ disproportionately decreased stem length growth. With Cd⁺² and Cu⁺² stem length was greater relative to other measures of growth. Toxicity of Na₂SO₄ and NaCl was the same when concentrations were calculated as osmotic pressure but not when calculated as Na atoms or as total molecules/L.     

Dew water chemical composition and source characterization in the IGP outflow location (coastal Bhola,Bangladesh)

Dew water samples were collected during the winter season (December, 2014 to January, 2015) at an outflow location from the Indo-Gangetic Plain (IGP) to the Bay of Bengal (Coastal Bhola, Bangladesh). Physical properties of the dew water, including pH and electrical conductivity (EC), were measured. The concentrations of water soluble ions (Cl^?, SO₄ ^2?, NO₃ ^?, HCO₃ ^?, Na⁺, K⁺, Ca²⁺, and Mg²⁺) and trace metals (Zn, Fe, Mn, Cu, Cr, Pd, and Ni) were also measured. Source characterization of the chemical species was done by correlation analysis, enrichment factor analysis, percent source contribution calculation, and air mass trajectory analysis. The average pH and EC of the collected dew water were 6.81 and 154.80 μS cm^?1, respectively. The average concentration of SO₄ ^2? and NO₃ ^? was 264.10 and 222.20 μeq L^?1, respectively. The concentrations of water soluble ions followed the sequence: Ca²⁺ > Cl^?> SO₄ ² > Na⁺ > NO₃ ^?> Mg²⁺ > K⁺ > HCO₃ ^?. The concentrations of trace metals ranged in order with Zn > Fe > Mn > Cu, while the concentrations of Cr, Pb, and Ni were below detection limit in dew water. Regression analysis showed significant correlations among sea, soil, and anthropogenic species. High enrichment factors of SO₄ ^2?, NO₃ ^?, Zn, Mn, and Cu indicates anthropogenic sources. Percent source contribution of different species showed significant anthropogenic contribution for Cl^?(1.80%), SO₄ ^2?(83.5%), and NO₃ ^?(99.3%). Air mass trajectory analysis supported that the regional urban pollutions have significant influence on the dew water chemistry at the coastal Bhola, Bangladesh.     

Chemical characteristics and possible causes of acid rain at a regional atmospheric background site in eastern China

A total of 43 rainwater samples were collected from March 2014 to February 2015 at a regional atmospheric background station, in Lin’an, Zhejiang province, eastern China. We analyzed all rainwater samples for pH, electrical conductivity, and concentration of SO₄ ^2?, NO₃ ^?, Cl^?, F, NH₄ ⁺, Ca²⁺, Na⁺, Mg²⁺, and K⁺. The pH of the 43 analyzed rainfall events ranged from 3.39–6.37, with a volume-weighted mean (VWM) of 4.74; 72% of the precipitation events qualified as acid rainfall (those where the rain pH was <5.6), indicating that acid rain pollution was severe in Lin’an area. Although the ionic concentrations in the Lin’an rainwater were lower than those found in most urban areas in China and in rural areas in India, they were still higher than those in Waliguan (a global atmospheric background station in northwestern China) and in Newark, NJ, USA. We found that SO₄ ^2? and NO₃ ^? were the major anions in the precipitation, accounting for an average of 88% of the total inorganic anions. The SO₄ ^2? concentration was between 3.8–303.9 μeq L^?1 with a VWM value of 49.8 μeq L^?1, while the NO₃ ^? concentration was between 3.0–206.5 μeq L^?1 with a VWM value of 32.6 μeq L^?1. The ratios of SO₄ ^2? to NO₃ ^? ranged from 0.71 to 2.56 with an average of 1.53, indicating that SO₄ ^2? was the most significant anion causing rainfall acidification in Lin’an area. This is similar to observations made in 2008. Compared to observations in Lin’an area in 2008, the contribution of SO₄ ^2? to rainwater acidity had decreased due to sharp reduction in SO₂ emissions, while the contribution of NO₃ ^? had increased due to a rapid growth in the use of motor vehicles in eastern China. We observed that the alkaline component NH₄ ⁺ made the largest contribution toward neutralizing rainwater acidity. The neutralization factor (NF) for NH₄ ⁺ was between 0.26 and 1.03 with an average of 0.63, and the NF for Ca²⁺ was between 0.09 and 1.21 with an average of 0.30. The ratio of Ca²⁺ to NH₄ ⁺ was between 0.15 and 4.70 with an average of 0.48, lower than that observed in Chinese urban areas and close to that observed in non-urban Chinese sites. These results indicated that Ca²⁺ was still a major factor in buffering rainwater acidity in most urban areas in China, while NH₄ ⁺ seemed to be the most important basic ion for neutralizing rainwater acidity in non-urban areas. In the Lin’an area, the Cl^? and K⁺ in rainwater were mostly of marine origin; however, SO₄ ^2?, Ca²⁺ and Mg²⁺ were generated mainly from the earth’s crust and anthropogenic emissions.     

Simulating Distribution of Trihalomethane in Tap Water in the Area Receiving a Combination of Advanced Treated Water and Conventionally Treated Different Source Water: 1998, 1999 and 2002 Data on Osaka Prefecture and Its Surrounding Cities,Japan

Empirical equations for explaining trihalomethane (THM) distribution were established based on data on tap water in Osaka City before and after starting the advanced treatment and were represented by the following equations for bromodichloromethane (S₁), dibromochloromethane (S₂) and bromoform distribution factors (S₃) as a function of chloroform distribution factor (S₀), respectively: S₁ = ?0.97S ₀ ²  + 0.75S₀ + 0.19 (regression coefficient: r = 0.71), S₂ = 0.13S ₀ ² ?0.76S₀ + 0.51 (r = 0.98) and S₃ = 0.83S ₀ ² ?0.99S₀ + 0.30 (r = 0.97). Further, the derived equations were verified by THMs data of Osaka Prefecture and its surrounding cities (except for Osaka City), receiving a combination of advanced treated water and conventionally treated different source water.     

Effect of sulfur dioxide on mucociliary activity and ciliary beat frequency in guinea pig trachea

Summary The effects of 30 min exposure to sulfur dioxide on mucociliary activity (MCA) and ciliary beat frequency (CBF) were studied in 31 guinea pig tracheas. MCA was measured by recording the light reflected from ciliated mucous membranes using an infrared bar code reader. CBF of single ciliated cells obtained by brushing was measured with phase-contrast microscopy. Each tracheal sample was exposed to SO₂ at concentrations ranging from 2.5 to 12.5 ppm, or to air for control purposes. MCA and CBF were measured before and immediately after gas exposure. A reduction in mean MCA of 63% (P = 0.0007) and statistically insignificant changes in CBF (P > 0.05) were recorded at concentrations of 2.5 PPM SO₂. Higher SO₂ concentrations caused a further impairment of MCA as well as a dose-dependent decrease in CBF (P = 0.002). A concentration of 12.5 PPM SO₂ induced a decrease from baseline values of approximately 80% in mean MCA and of roughly 70% in mean CBE This study demonstrates a dose-dependent SO₂-induced decrease in MCA of guinea pig tracheas. The decrease in MCA was associated with an impairment of CBF only at SO₂ concentrations higher than 5.0 ppm.     

Effects of 0.75ppm Sulfur Dioxide on Pulmonary Function Parameters of Normal Human Subjects

Of 31 young, healthy male volunteers who participated in this study, 15 were exposed to air (control) and 16 to 0.75 ppm (2.15 mg/m³) SO₂ for 2 hr at 21°C and 60% relative humidity. At the end of the first hour, the subjects exercised for 15 min on a treadmill at 6.4 kmph, with a 10% grade. Methods employed in evaluation of pulmonary function included body plethysmography, spirometry, and multigas rebreathing test. From the battery of 15 pulmonary function parameters, only the pattern of airway resistance changes was significantly altered by SO₂ exposure, although spirometric parameters followed a similar pattern. Eight of the SO₂-exposed subjects, with one or more positive allergen skin tests, appeared to be significantly more reactive to SO₂ than skin test-negative subjects. All subjects remained asymptomatic. The small number of changes observed appeared to be reversible and do not suggest a significant health hazard to normal human subjects exposed to SO₂ under these conditions.     

Effect of ethyl acetate on carbohydrate metabolism of common Indian catfish

Median lethal concentration (LC₅₀), LC₀, and LC₁₀₀ values of ethyl acetate for common Indian catfish, Heteropneustes fossilis, were estimated at 24, 48, 72, and 96 hr with 95% confidence limits. The 96-hr LC₅₀ value and harmless (safe) concentration were 212.5 and 63.89 ppm, respectively. Exposure of the fish to 170 ppm of ethyl acetate for 3, 6, 12, 48, and 96 hr induced marked changes in carbohydrate metabolism. Hepatic glycogen values declined significantly at 3, 48, and 96 hr, but there was no marked alteration in muscle glycogen content at any of the exposure periods. Hyperglycemia occurred at all time intervals. Blood pyruvate levels were elevated at 3, 6, 48, and 96 hr. Hyperlacticemia resulted at 3 and 96 hr but hypolacticemia occurred at 6 and 12 hr. Impairment of carbohydrate metabolism might be responsible for the toxic action of ethyl acetate.