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Archives of Environmental Contamination and Toxicology (v.37, #4)
Oxidation of 2,4-Dinitrophenol by Hydrogen Peroxide in the Presence of Basic Oxygen Furnace Slag by Y.-S. Li; Y.-H. You; E.-T. Lien (pp. 427-433).
A treatment process was developed when basic oxygen furnace slag (BOF slag) and hydrogen peroxide were used to oxidize 2,4-dinitrophenol from an aqueous solution. BOF slag, final waste slurry from steel making plants, contains about 12.5% by weight of ferrous oxide. In an acid solution, BOF slag can be dissociated to produce ferrous ions and react with hydrogen peroxide to produce hydroxyl radicals and oxidize 2,4-dinitrophenol. The results of the research demonstrated that the process had a significant capacity for oxidation of 2,4-dinitrophenol from the aqueous phase. Various factors critical to the oxidation of 2,4-dinitrophenol were studied, including hydrogen peroxide concentration, concentration of BOF slag, initial concentration of 2,4-dinitrophenol, and pH value of solution. Experimental results proved that 100 mg/L 2,4-dinitrophenol and its oxidation intermediate could be totally decomposed within 60 min by 10 g/L BOF slag, 0.18 g/L hydrogen peroxide and pH 2.8 ± 0.2. The optimum hydrogen peroxide concentration for degradation of 100 mg/L of 2,4-dinitrophenol is between 0.09 g/L and 0.18 g/L as 10 g/L BOF slag in the solution of pH 2.8 ± 0.2. A hydrogen peroxide concentration higher than 0.18 g/L is disadvantageous to the oxidation process. The oxidation efficiency increased with the increase of BOF slag concentration at 0.18 g/L hydrogen peroxide dose. The best pH value of the solution is in the vicinity of 2.8. An oxidation reaction mechanism was proposed for predicting the concentration changes of 2,4-dinitrophenol, ferrous ion, and hydrogen peroxide.
Comparison of Pure Nicotine- and Smokeless Tobacco Extract-Induced Toxicities and Oxidative Stress by D. Yildiz; Y.-S. Liu; N. Ercal; D. W. Armstrong (pp. 434-439).
The toxicities and oxidative stress-inducing actions of (−)-nicotine and smokeless tobacco extract (STE), containing equivalent amounts of nicotine, were studied. Toxicities were determined by colony formation assays using Chinese hamster ovary (CHO) cells. Results indicated that nicotine is less toxic than smokeless tobacco extract that contained the same amount of nicotine. The generation of reactive oxygen species, following treatment with smokeless tobacco extract and nicotine, was assessed by measurement of changes in glutathione (GSH) and malondialdehyde (MDA) levels. CHO cells (5 × 105 cells/5 ml media) were incubated with 4, 0.8, and 0.08 mg of nicotine and STE containing the same amounts of nicotine. All preparations of smokeless tobacco extract significantly decreased GSH levels and increased MDA generation. However, 0.08 mg of nicotine treatment did not result in a significant change in GSH level, and only 4 mg of nicotine were sufficient to increase MDA generation. Addition of free radical scavenging enzymes, superoxide dismutase (SOD) and catalase (CAT), and an intracellular GSH precursor, N-acetyl-L-cysteine (NAC), replenished the GSH levels in nicotine-treated cells. GSH levels in cells exposed to smokeless tobacco extract containing 4 and 0.8 mg nicotine remained significantly lower than the control with the addition of SOD and CAT. However, co-addition of NAC with smokeless tobacco extract preparations returned the GSH levels to the control level. Lactate dehydrogenase (LDH) activities were measured in the media to establish the membrane damage following exposure to smokeless tobacco extract and nicotine. Treatment of cells with 4 mg nicotine caused a significant increase in LDH activity, which was returned to control level in the presence of the antioxidant enzymes and NAC. Smokeless tobacco extract did not change the LDH activity.
Supercritical Fluid Extraction and Solid-Phase Extraction of AC 263,222 and Imazethapyr from Three Texas Soils by P. F. Pace; S. A. Senseman; M. L. Ketchersid; H. T. Cralle (pp. 440-444).
Supercritical fluid extraction (SFE) using CO2 and solid-phase extraction (SPE) are two technologies recently discussed in the literature as alternatives to Soxhlet and liquid/liquid extraction (LLE). This research compared SFE and SPE extraction efficiency of two imidazolinone herbicides, AC263,222 and imazethapyr, from three soils. Recovery of the herbicides using SFE-CO2 with a 4.6:1 acetonitrile:acetic acid cosolvent was approximately 80% for Poth and Tremona soils and 60% when extracted from Ships soil with high clay content and high pH. SPE recovery of both herbicides averaged 78% and was not statistically different between soils. Combining SPE disks with a SPE cartridge cleanup procedure provided a faster filtration with cleaner filtrate compared with using SPE C-18 cartridges by themselves. Cleanup was needed after both SFE and SPE disk extraction due to interfering peaks in the chromatography.
Tidal Creek and Salt Marsh Sediments in South Carolina Coastal Estuaries: I. Distribution of Trace Metals by D. M. Sanger; A. F. Holland; G. I. Scott (pp. 445-457).
Twenty-eight tidal creeks were sampled along the South Carolina coast in the summer of 1995 to determine the levels of sediment trace metal contamination associated with different types and varying levels of human development in their watersheds. The particle size and total organic carbon (TOC) content of creek sediments in developed watersheds (i.e., industrial, urban, and suburban) were similar to that in watersheds with little or no development (i.e., forested or reference). Those trace metals commonly associated with urban and industrial sources, including Cu, Cr, Pb, Zn, Cd, and Hg, were in significantly higher concentrations in tidal creeks located in industrial/urban watersheds compared to the suburban and forested watersheds. Sediment trace metal concentrations were similar for creeks located in suburban and forested watersheds and 2 to 10 times lower than the creeks located in industrial/urban watersheds. Concentrations of trace metals primarily associated with the natural weathering of basement rock, including Al, Fe, As, Ni, and Mn, were not significantly different among watershed types. Four of the tidal creek–salt marsh systems were extensively sampled from the creek channel to the marsh-upland interface to characterize sediment trace metal spatial distributions within creek-marsh systems. Sediment particle size, TOC, and trace metal concentrations varied spatially within each creek-marsh system depending on the type of development in the watershed and the probable source of metals. The creek-marsh system selected to represent the industrial development had significantly higher “anthropogenic” trace metal concentrations compared to the other creek-marsh systems. This system also had trace metal distributional patterns that appeared to be associated with several localized sources of metals on the marsh surface. Both the “anthropogenic” and “natural” trace metal concentrations andspatial distributions were similar among and within the forested and suburban creek-marsh systems.
Tidal Creek and Salt Marsh Sediments in South Carolina Coastal Estuaries: II. Distribution of Organic Contaminants by D. M. Sanger; A. F. Holland; G. I. Scott (pp. 458-471).
Twenty-eight tidal creeks along the South Carolina coast were sampled during the summer of 1995 to determine the levels of sediment contamination including organic chemicals (i.e., polycyclic aromatic hydrocarbons [PAHs], polychlorinated biphenyls [PCBs], and DDT and its metabolites) associated with different types and varying levels of watershed development (i.e., industrial/urban, suburban, forested, and salt marsh). Organic analysis utilized high-performance liquid chromatography (HPLC) with fluorescence detection and capillary gas chromatography–ion trap mass spectrometry (GC-ITMS) for PAHs, and gas chromatography with electron capture detection (GC-ECD) for pesticides and PCBs. Results indicated that creeks with industrial/urban watersheds had significantly higher concentrations of PAHs, PCBs, and DDT compared with creeks with suburban and forested (reference) watersheds. The suburban watershed class of creeks had concentrations of half the PAH analytes and the total PCBs which exceeded the concentrations found in the forested watershed class of creeks. The spatial distribution of organic contaminants was evaluated in four of these tidal creek–salt marsh systems representing urban/industrial, suburban, and forested watersheds, from the creek channel to the adjacent uplands. The distribution of organic contaminants within each representative creek was not concordant with the total organic carbon or the clay content of the sediment. The representative industrial/urban creek-marsh system, Diesel Creek, had the highest concentration of PAHs in the creek channel and the highest concentration of PCBs and DDT on the marsh surface, primarily in the upper portion of the system. The representative suburban creek-marsh system, Shem Creek, had elevated levels of both PAHs and PCBs throughout the entire system. This system also had one site with a total PAH concentration of 324,000 ppb and a total DDT concentration that was 20–100 times higher than the other sites. One of the representative forested creek-marsh systems, Rathall Creek, had low levels of the three organic contaminants except for one sampling site that had PAH concentrations a factor of 10 higher than the other sites. The other representative forested creek-marsh system, Long Creek, had low levels of PAHs and PCBs, but elevated levels of DDT were observed, particularly in the upper portion on the marsh surface. The results of this study suggest that (1) anthropogenic alteration of the land cover in the watersheds of tidal creek–salt marsh systems may increase the organic contaminant loadings in the sediment, and (2) tidal creek–salt marsh sediments, particularly in the creek channel, are repositories and potentially conduits of organic contaminants from the upland environment to the deeper estuarine areas.
Tolerance of Oscillatoria limnetica Lemmermann to Atrazine in Natural Phytoplankton Populations and in Pure Culture: Influence of Season and Temperature by A. Bérard; C. Leboulanger; T. Pelte (pp. 472-479).
The responses of algae to herbicides depend on the sensitivity of each species, but competition within algal communities may be an important regulator of the effects of herbicides on aquatic systems. The impact of herbicides on algae also depends on abiotic factors like nutrients, light, and temperature. We examined the tolerance of the alga Oscillatoria limnetica Lemmermann to the photosystem II inhibitor herbicide atrazine under different culture conditions to assess those interactions between herbicides and biotic and abiotic factors. The density of the cyanobacterium O. limnetica was determined in natural phytoplanktonic assemblages and in unialgal cultures in medium containing 10 μg/L atrazine. Experiments (total of 13) were conducted in spring and early and late summer, during which the effect of atrazine varied in nature and intensity. The growth of the cyanobacterium was always inhibited in cold experiments, whereas it was stimulated in warm experiments within the natural phytoplankton assemblage, but unaffected in pure culture. Laboratory experiments with unialgal culture showed that the sensitivity to atrazine increased as the temperature decreased. Phytoplankton community structure, interactions between species, and environmental parameters (e.g., temperature) are important factors controlling the responses of cyanobacteria to the herbicide. These interactions between sensitivity to herbicides and environmental factors may reduce or emphasize the effects of pollution in aquatic systems. Thus, the ecotoxicological relevance of herbicides in aquatic systems is quite complex and cannot be assessed by single-species short-term laboratory toxicological tests.
Changes in Growth and Physiology of Tobacco and Cotton Under Ag Exposure and Recovery: Are They of Direct or Indirect Nature? by G. Ouzounidou; H. A. Constantinidou (pp. 480-487).
Responses of tobacco and cotton seedlings to two chemical forms of Ag at various concentrations were studied. Cotton exhibited higher resistance than tobacco to Ag. The application of 1 μg L−1 Ag, as AgI or AgNO3, induced no toxicity symptoms in the growth and photosynthesis of cotton. However, the corresponding concentration negatively affected the growth and physiology of tobacco. On exposure to higher Ag concentrations (103 and 5 × 103μg L−1 as AgNO3), root growth and concentrations of Ca, Mg, K, and Fe were significantly depressed, whereas concomitant Ag accumulation, especially in roots, was increased in both species. The loss of nutrients and chlorophyll was associated with disturbances in photosynthetic function. Because there was no apparent change in Fv/Fm, there is a possibility that the faster rise time was due to an increase in LHC size to the PSII reaction centers. The decreased Fv/Fo reflects the inactivation of chlorophyll associated with the PSII reaction center. Stomatal conductance was decreased less than the CO2 assimilation, possibly due to the direct and/or indirect effects of Ag ions on stomatal guard cells. After the plants were transferred from the highest Ag concentration to a nutrient solution, recovery of tobacco, cotton morphology, and physiology were observed.
A Site-Specific Evaluation of Mercury Toxicity in Sediment by J. C. Sferra; P. C. Fuchsman; R. J. Wenning; T. R. Barber (pp. 488-495).
A site-specific evaluation of mercury toxicity was conducted for sediments of the Calcasieu River estuary (Louisiana, USA). Ten-day whole-sediment toxicity tests assessed survival and growth (dry weight) of the amphipods Hyalella azteca and Leptocheirus plumulosus under estuarine conditions (10 ppt salinity). A total of 32 sediment samples were tested for toxicity, including 14 undiluted site sediment samples and 6 sediment dilution series. All sediment samples were analyzed for total mercury and numerous other chemical parameters, including acid volatile sulfide (AVS) and simultaneously extracted metals (SEM). No toxicity attributable to mercury was observed, indicating that a site-specific threshold for total mercury toxicity to amphipods exceeds 4.1 mg/kg dry weight. Site-specific factors that may limit mercury bioavailability and toxicity include relatively high sulfide levels. Additionally, the chemical extractability of mercury in site sediments is low, as indicated by SEM mercury analyses for three sediment samples containing a range of total mercury concentrations.
Comparative Toxicity of Fluoranthene to Freshwater and Saltwater Species Under Fluorescent and Ultraviolet Light by R. L. Spehar; S. Poucher; L. T. Brooke; D. J. Hansen; D. Champlin; D. A. Cox (pp. 496-502).
The acute and chronic toxicity of fluoranthene was determined for a diverse group of freshwater and saltwater species under both standard laboratory fluorescent light and ultraviolet (UV) light test conditions. Acute tests with 21 species demonstrated that fluoranthene was not lethal within its water solubility limit to most species tested under fluorescent light, but was lethal well below this limit to nearly all of the species tested under UV light. In general, the acute sensitivity of freshwater and saltwater species from the same class was similar, although UV light exposure changed the relative sensitivity of some species. Crustaceans were the most sensitive to fluoranthene, but in the presence of UV light, an oligochaete and a fish were the most sensitive. Overall, UV light increased acute fluoranthene toxicity approximately one to three orders of magnitude. In chronic tests, sublethal concentrations of fluoranthene were toxic under both fluorescent and UV light, but as in most acute tests, UV light increased chronic toxicity approximately an order of magnitude. Comparison of data from tests conducted in the laboratory and outdoors demonstrated that acute toxicity increased with increased UV light intensity.
Effect of Single and Paired Metal Inputs in Soil on a Stress-Inducible Transgenic Nematode by R. S. Power; D. I. de Pomerai (pp. 503-511).
A toxicity test using a transgenic strain of the free-living soil nematode Caenorhabditis elegans carrying a stress-inducible β-galactosidase reporter has been adapted for use in soil biomonitoring. High concentrations (250 μg · g−1) of cadmium are required to induce the stress response in worms exposed to Lufa 2.2 soil. Even at relatively high concentrations, the response to copper and zinc additions alone is minimal, yet combinations of cadmium and copper in the test soil induce a larger response than with cadmium alone at the same concentration. In contrast, the addition of both zinc and cadmium induces a lower response than cadmium additions alone. Analysis of the interstitial water suggests that there is preferential occupation by copper of sorption sites in the soil, allowing more cadmium to remain in solution. Conversely, cadmium and zinc would appear to interact similarly with the soil constituents, resulting in an increase of both metals in solution with increased additions to the soil. Aquatic tests mimic the results of the soil test, so it is not increased cadmium availability alone that causes an increased stress response when both cadmium and copper are present. The presence of other metals could reduce the amount of cadmium available, which may be one factor in the zinc moderation of the stress response to cadmium. Intracellular mechanisms may also contribute to the copper enhancement of the stress response to cadmium.
Benthic Community Structure and Biomarker Induction in Grass Shrimp in an Estuarine System by E. Oberdörster; M. Martin; C. F. Ide; J. A. McLachlan (pp. 512-518).
The impact of polycyclic aromatic hydrocarbons (PAHs) and lead contamination on benthic community structure and grass shrimp (Palaeomonetes sp.) biochemical markers were investigated in a bayou that has been heavily contaminated by PAHs and heavy metals. The benthic community had decreased species richness as well as decreased numbers of individuals along a contamination gradient. Grass shrimp collected in the field showed a contaminant-gradient increase in heat shock protein 63 and cytochrome P450 1A (as measured by ECOD metabolism). Grass shrimp had elevated ECOD metabolism when exposed in the laboratory to sediments from the most contaminated site. However, individual variation was too great for statistically significant changes. In addition, heat shock protein levels were not significantly elevated in laboratory exposed shrimp. Benthic community structure and wild-caught grass shrimp are clearly impacted in this bayou.
The Effects of Reduced Agent-Area Insecticide Treatments for Rangeland Grasshopper (Orthoptera: Acrididae) Control on Bird Densities by E. E. Norelius; J. A. Lockwood (pp. 519-528).
The effects of insecticidal control programs for grasshoppers on the population density of birds were assessed under operational conditions in two rangeland sites in Wyoming during an outbreak (19 to 56 grasshoppers m−2 on >1,500 ha). Malathion, carbaryl, and fipronil were evaluated using large-scale (≥260 ha) reduced agent-area treatments (RAAT), in which these chemicals were applied at 50% of the standard rate (except fipronil, for which there is no standard in North America) to 80, 50, and 33% of the areas (alternating treated and untreated swaths), respectively. Grasshopper population densities were reduced by 73 to 99%, at 14 and 28 days after treatment. Significant differences among treatments within the sites were apparent, and despite disparities in the vegetation, topography, and grasshopper populations between sites, some consistent patterns of response by bird populations were found. Relative to pretreatment densities and untreated plots, at 14 days after treatment, bird densities were enhanced at one site and suppressed at the other; at 28 days after treatment bird populations were generally suppressed at both sites. However, absolute densities increased in some plots, indicating that birds still had adequate food. There appeared to be no relationship between posttreatment grasshopper and bird densities, perhaps due to the large initial insect populations. Fipronil plots generally had higher avian population densities (nongregarious insectivores and total birds) than carbaryl plots, which had bird densities greater than or equal to malathion plots. These differences were probably a function of both the toxicological properties of the compounds and the proportion of the infested land that was treated. Based on these findings, we must consider the possibility that compounds with relatively high toxicity to birds and long residual effects applied to widely spaced swaths may cause no more (or perhaps less) environmental impact than less toxic and persistent insecticides that must be applied to large proportions of infested rangeland.
The Effect of Insecticides on Learning in the Africanized Honey Bee (Apis mellifera L.) by C. I. Abramson; I. S. Aquino; F. S. Ramalho; J. M. Price (pp. 529-535).
The present study was designed to examine the effects of endosulfan, decis, baytroid, and sevin on the learning ability of Africanized honey bees (Apis mellifera L.). Although these insecticides were recommended by the government of Brazil to control the cotton boll weevil, the effects on bees have been unknown. Results of the present research show that: (1) bees readily consume each of the pesticides when placed in a sucrose solution; (2) the odors of the pesticides are not repellent to bees, and such odors can serve as conditioned stimuli; (3) learning occurs to various degrees when the insecticides are combined with the sucrose solution and used as an unconditioned stimulus; and (4) feeding the insecticides to the bees 1 h prior to conditioning leads to differing mortality. Because of the importance of bees for honey production, as well as pollination of cotton and other crops, recommendations are made for the use of decis and other measures for boll weevil control.
Effects of a Homologous Series of Linear Alcohol Ethoxylate Surfactants on Fathead Minnow Early Life Stages by R. E. Lizotte Jr.; D. C. L. Wong; P. B. Dorn; J. H. Rodgers Jr. (pp. 536-541).
Effects of a homologous series of three primarily linear alcohol ethoxylate surfactants were studied in laboratory flow-through 28-day early-life-stage tests with fathead minnow (Pimephales promelas Rafinesque). Surfactants were a C9–11, C12–13, and C14–15 with an average of 6, 6.5, and 7 ethylene oxide units per mole of alcohol, respectively. Average measured surfactant recoveries were 103%, 81%, and 79% of nominal concentrations for the C9–11 EO 6, C12–13 EO 6.5, and C14–15 EO 7 studies, respectively. Embryo survival at 48 h was not adversely affected at any of the concentrations tested. Impaired hatching and deformed fry were observed only in the C12–13 EO 6.5 study. The 28-day LC50 values were 4.87, 2.39, and 1.02 mg/L for the C9–11 EO 6, C12–13 EO 6.5, and C14–15 EO 7 surfactants, respectively. The corresponding NOECs for survival were 1.01, 1.76, and 0.74 mg/L. Posthatch fry growth was more sensitive than survival for the C12–13 EO 6.5 and C14–15 EO 7 surfactants. Survival of posthatch fry decreased with increasing surfactant alkyl chain length. Twenty-eight-day laboratory data were compared to 96-h laboratory, 10-day laboratory and 30-day stream mesocosm data for fathead minnow previously determined for these surfactants. Survival endpoints from the different exposures were comparable and only varied within a factor of two. Similarity of results suggests that it is possible to effectively use 96-h, 10-day, or 28-day laboratory data to predict environmental effects concentrations of these surfactants for fish.
Effects of Temperature on the Toxicity of M-Parathion, Chlorpyrifos, and Pentachlorobenzene to Chironomus tentans by M. J. Lydy; J. B. Belden; M. A. Ternes (pp. 542-547).
This study examined the influence of temperature (10, 20, and 30°C) on the acute toxicity and accumulation of two organophosphate (OP) insecticides and a narcotic chemical to the midge (Chironomus tentans). OP insecticides used in this study included chlorpyrifos and m-parathion, and pentachlorobenzene was the chosen narcotic. Chlorpyrifos was the most toxic chemical tested, followed by m-parathion and then pentachlorobenzene. A positive correlation was found between temperature and toxicity for each of the chemicals tested. A reverse trend was noted for total OP insecticide body residues with decreased concentrations found at the higher temperatures. Pentachlorobenzene body residues remained constant at all temperatures. All three chemicals showed increased uptake rates at 20 and 30°C in comparison to 10°C. The noted decrease in midge body residues at the higher temperatures for the OP insecticides was contributed to increased biotransformation and elimination rates at the higher temperatures. Overall, temperature had a greater influence on OP toxicity than for pentachlorobenzene, and this may be due to accelerated biotransformation of the OPs to more toxic o-analog metabolites at the higher temperatures.
Predicting Starling Chick Carcass PCB Concentrations from PCB Concentrations in Ingested Animal Matter by S. M. Arena; R. S. Halbrook; C. A. Arenal (pp. 548-553).
Preremediation studies at Crab Orchard National Wildlife Refuge (CONWR) revealed statistically significant accumulations of polychlorinated biphenyls (PCBs) and effects in starling chicks (Sturnus vulgaris) from contaminated sites, including decreased nest attentiveness, decreased fledging success, and an increase in chick mortality. Although the expected route of exposure for starling chicks is thought to be via diet, this has not previously been documented at CONWR. The purpose of this study was to develop an equation to predict starling chick carcass PCB concentrations from PCB concentrations in ingested animal matter. During 1995 and 1996, stomach contents from 14 and 22 starling chicks collected from contaminated and reference sites, respectively, were evaluated. Animal, plant, and mineral matter in the stomach contents were separated and animal matter from stomachs of individuals from the same nest were combined, dried, and percent dry weight calculated. Composite samples of animal matter were then analyzed for the presence of PCBs (Aroclor 1254). Stomach contents were primarily composed of animal matter (76%), and the percent animal matter in the stomachs did not differ significantly among locations (range = 38.4% to 100%). The mean PCB concentration in composite samples of animal matter from stomachs of chicks collected from contaminated sites (1.82 ± 1.17 mg/kg) was significantly greater than the concentrations in composite samples from two reference locations (<0.24 mg/kg). PCB concentrations in stomach contents were correlated (Pearson correlation coefficient = 0.91, p < 0.005) with concentrations in carcasses of chicks from which the stomachs had been collected. The regression Y = 6.19 × X1,398, where Y = starling chick carcass PCB concentration and X = starling stomach animal matter PCB concentration, indicated that PCB concentrations in consumed animal matter accounted for 82% of the variability in starling carcass concentrations.
Age-Related Alterations in Antioxidant Enzymes, Lipid Peroxide Levels, and Somatosensory-Evoked Potentials: Effect of Sulfur Dioxide by P. Yargiçoğlu; A. Ağar; S. Gümüşlü; S. Bilmen; Y. Oğuz (pp. 554-560).
The effect of sulfur dioxide (SO2) on somatosensory-evoked potentials (SEPs), thiobarbituric acid reactive substances (TBARS), and the activities of Cu,Zn-superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) were investigated in young (3 months), middle-age (12 months), and old (24 months) Swiss male albino rats. Ten ppm SO2 was administrated to the animals of SO2 groups in an exposure chamber for 1 h/day × 7 days/week × 6 while control groups were exposed to filtered air in the same condition. SO2 exposure caused increased levels of brain Cu,Zn-SOD activity and decreased levels of brain GSH-Px activity in all experimental groups with respect to their corresponding control groups. Brain CAT activities were unaltered. Brain TBARS levels of all SO2-exposed groups were significantly increased in comparison with their respective control groups. The mean latencies of P1, P2, and N2 components in the older group were either significantly different from the young or from the middle-age groups. The mean latency of the N1 component in the older group and that of P1 and N1 in the middle-age group were significantly increased compared with the young group. SO2 exposure caused the prolongation of all components in the young group, whereas it affected only the P2 component in the middle-age group, but it did not result in any latency change in the older group in comparison with their corresponding control groups.