Showing papers by "United States Environmental Protection Agency published in 1983"
TL;DR: A synthesis of available literature on uncertainty (safety) factors which are used to estimate acceptable daily intakes (ADIs) for toxicants is presented, revealing reasonable qualitative biological premises, as well as specific biological data that support both the use and choice of these factors.
410 citations
TL;DR: Pulmonary effects of O3 were observed at levels much lower than that for which these effects have been previously described, and Stimulation of airway receptors is probably the mechanism responsible for the majority of observed changes.
Abstract: Because minimal data are available regarding the pulmonary effects of ozone (O3) at levels less than 0.27 ppm, six groups of healthy young males were exposed for 2.5 h to one of the following O3 concentrations: 0.0, 0.12, 0.18, 0.24, 0.30, or 0.40 ppm. Fifteen-minute periods of rest and exercise (65 l/min minute ventilation) were alternated during the first 2 h of exposure. Coughing was observed at all levels of O3 exposure. Small changes in forced-expiratory spirometric variables [forced vital capacity (FVC), forced expiratory volume in 1 s, and mean expiratory flow rate between 25 and 75% FVC] were observed at 0.12 and 0.18 ppm O3, and larger changes were found at O3 levels greater than or equal to 0.24 ppm. Changes in tidal volume and respiratory frequency during exercise, specific airway resistance, the presence of pain on deep inspiration, and shortness of breath occurred at O3 levels greater than or equal to 0.24 ppm. In conclusion, pulmonary effects of O3 were observed at levels much lower than that for which these effects have been previously described. Stimulation of airway receptors is probably the mechanism responsible for the majority of observed changes; however, the existence of a second mechanism of action is postulated.
316 citations
TL;DR: In this paper, the number of microbes was found to be surprisingly similar at all three depths (3 to 9 × 106/g dry material) at the margin of a small floodplain near Lula, Oklahoma.
Abstract: Regions of the earth below the root zone of soil have conventionally been considered void of life. However, widespread pollution of ground water in the U.S. by organic compounds has kindled interest in the numbers of microbes that might be found in aquifers and associated regions of the deeper unsaturated zone, and in their ability to degrade organic pollutants.
Newly developed techniques in microbial ecology allow the direct enumeration and examination of soil microbes without recourse to their cultivation on growth media. These techniques reduce many uncertainties associated with the use of culture media, such as the growth of contaminants or the failure of indigenous forms to grow on a particular medium. Samples were recovered aseptically from depths of 1·2, 3·0, and 5·0 meters (m) at the margin of a small floodplain near Lula, Oklahoma. Depth to the water table was 3·6 m; depth to bedrock was 6·0 m. Numbers of microbes were surprisingly similar at all three depths (3 to 9 × 106/g dry material). Although both Gram-positive and Gram-negative bacteria were encountered, small Gram-positive coccoid forms predominated. No protozoa, yeasts, or other fungi were seen. The indigenous bacteria could rapidly degrade toluene. Chlorobenzene was degraded in material from the vadose zone, while bromodichloromethane was degraded in material from the saturated zone. There was no detectable degradation of 1,2-dichloroethane, 1,1,2-trichloroethane, trichloroethylene, or tetrachloroethylene.
278 citations
TL;DR: Microbial communities in preexposed cores from a number of freshwater sampling sites adapted to degrade p-nitrophenol faster; communities from estuarine or marine sites did not show any increase in rates of degradation as a result of preexposure.
Abstract: Adaptation of microbial communities to faster degradation of xenobiotic compounds after exposure to the compound was studied in ecocores. Radiolabeled test compounds were added to cores that contained natural water and sediment. Adaptation was detected by comparing mineralization rates or disappearance of a parent compound in preexposed and unexposed cores. Microbial communities in preexposed cores from a number of freshwater sampling sites adapted to degrade p-nitrophenol faster; communities from estuarine or marine sites did not show any increase in rates of degradation as a result of preexposure. Adaptation was maximal after 2 weeks and was not detectable after 6 weeks. A threshold concentration of 10 ppb (10 ng/ml) was observed; below this concentration no adaptation was detected. With concentrations of 20 to 100 ppb (20 to 100 ng/ml), the biodegradation rates in preexposed cores were much higher than the rates in control cores and were proportional to the concentration of the test compound. In addition, trifluralin, 2,4-dichlorophenoxyacetic acid, and p-cresol were tested to determine whether preexposure affected subsequent biodegradation. Microbial communities did not adapt to trifluralin. Adaptation to 2,4-dichlorophenoxyacetic acid was similar to adaptation to nitrophenol. p-Cresol was mineralized rapidly in both preexposed and unexposed communities.
248 citations
TL;DR: In this paper, the authors focus on the development of quantitative risk assessment approaches by Federal regulatory agencies in the United States, and identify the mathematical models currently being used for risk extrapolation, including their inherent uncertainties.
Abstract: Scientists have long used conventional toxicological methods to establish “safe levels of exposure” for chemicals presumed to have threshold health effects or doses below which significant effects are unlikely to occur. These same methods cannot be used to establish safe levels of exposure for non-threshold pollutants, such as carcinogens. Therefore, Federal regulatory agencies in the United States are using risk assessment methods to provide information for public health policy decisions concerning increases in risk associated with increases in exposure to carcinogenic and other non-threshold pollutants. Acceptable exposure/risk levels are decided by policymakers who consider descriptions and estimates of risks together with social and economic benefits from the uses of the chemical. This paper focuses on the development of quantitative risk assessment approaches by Federal regulatory agencies in the United States, and identifies the mathematical models currently being used for risk extrapolation, including their inherent uncertainties. The uncertainties and limitations of these methods have led some scientists to question the utility of quantitative risk extrapolation. The experience of the U.S. Environmental Protection Agency (EPA), as summarized in this paper, can provide a realistic basis for evaluating the pros and cons. Finally, shortcomings in current risk assessment methods and their use in policy decisions are explored, and areas for possible improvement, given current scientific knowledge, are identified.
243 citations
TL;DR: The study supports the hypothesis that the toxicant-population-dose-response system can lead to multiple stable equilibria where, in the absence of the Toxicant, the population has only a single stable equilibrium.
214 citations
TL;DR: In this paper, the effectiveness of natural hydrocarbons in contributing to ozone formation and aerosol formation in ambient air is discussed, and it is concluded that NOCs do not contribute substantially to the formation of either ozone or aerosols in the ambient air.
180 citations
TL;DR: Production of mutagens is greatly dependent on the chlorination pH, with a pattern of decreasing mutagenic activity with increasing pH, which can be at least partially explained by the alkali liability of the compounds.
Abstract: Aqueous chlorination of humic acids results in the formation of compounds with direct-acting mutagenic activity in the Ames/Salmonella plate assay for tester strains TA98, TA100, TA1535, TA1537 and TA1538. The addition of a rat-liver microsomal fraction (S9) plus cofactors causes a substantial decrease of activity, the extent of which is tester strain dependent. The non-chlorinated humic acids are not mutagenic either in the presence or absence of S9. Formation of mutagenic activity and of total organic halogen (TOX) is linearly related to humic concentration in the range of 0.2–1.6 mg/ml total organic carbon (TOC), and to chlorine concentration in the range of 0.1–1.0 chlorine equivalents per mole of carbon. The mutagenic activity is due predominantly to non-volatile compounds. Mutagenic activity is also detectable, after sample concentration by lyophilization, upon chlorination at a humic acid level of 0.02 mg/ml TOC. The specific mutagenic activities (per mg TOX), and also the degree of chlorine incorporation into humic acid, at 0.02 mg/ml TOC are similar to those present after chlorination at 1 mg/ml TOC. Production of mutagens is greatly dependent on the chlorination pH, with a pattern of decreasing mutagenic activity with increasing pH. This order of activity can be at least partially explained by the alkali lability of the compounds. Chlorination of commercial humic acids is proposed as a model for examination of mutagen formation during water chlorination.
120 citations
TL;DR: This communication established a list of 47 compounds or conditions which demonstrate a wide range of teratogenicity in vivo, intended to serve as a base for in vitro teratogenesis test validation and should prove useful in developing and identifying those systems which will contribute to a more effective testing program.
Abstract: The Consensus Workshop on In Vitro Teratogenesis Testing recommended that test validation be facilitated by a listing of agents with defined teratogenicity; subsequently, a panel was convened to review and select such agents. This communication established a list of 47 compounds or conditions which demonstrate a wide range of teratogenicity in vivo. The agents were chosen primarily on the strength of the literature base denoting their in vivo effects. The tables note a number of general biological and toxicological characteristics for each agent, and the details of representative in vivo teratology studies are summarized and referenced. This list is intended to serve as a base for in vitro teratogenesis test validation and should prove useful in developing and identifying those systems which will contribute to a more effective testing program.
112 citations
111 citations
TL;DR: Stable carbon isotope compositions were analyzed for estuarine fauna collected in tidal creeks draining salt marshes dominated by either Spartina alterniflora Loisel or Juncus roemerianus Scheele, and suggested that the subtidal food web is structured such that individual invertebrate and fish species show varying degrees of dependence on the detritus/benthic algae-based food web of the marsh vs. the phytoplankton- based food web
TL;DR: The mouse skin initiation bioassay was used to determine the unit lung cancer risk for the most potent of the diesel emissions, and there was a high correlation between the in vitro and in vivo bioassays in their responses to the engine exhaust particulate extracts.
Abstract: An estimation of the human lung cancer “unit risk” from diesel engine particulate emissions has been made using a comparative potency approach. This approach involves evaluating the tumorigenic and mutagenic potencies of the particulates from four diesel and one gasoline engine in relation to other combustion and pyrolysis products (coke oven, roofing tar, and cigarette smoke) that cause lung cancer in humans. The unit cancer risk is predicated on the linear nonthreshold extrapolation model and is the individual lifetime excess lung cancer risk from continuous exposure to 1 μg carcinogen per m3 inhaled air. The human lung cancer unit risks obtained from the epidemiologic data for coke oven workers, roofing tar applicators, and cigarette smokers were, respectively, 9.3 × 10−4, 3.6 × 10−4, and 2.2 × 10−6 per μg particulate organics per m3 air. The comparative potencies of these three materials and the diesel and gasoline engine exhaust particulates (as organic extracts) were evaluated by in vivo tumorigenicity bioassays involving skin initiation and skin carcinogenicity in SENCAR mice and by the in vitro bioassays that proved suitable for this analysis: Ames Salmonella microsome bioassay, L5178Y mouse lymphoma cell mutagenesis bioassay, and sister chromatid exchange bioassay in Chinese hamster ovary cells. The relative potencies of the coke oven, roofing tar, and cigarette smoke emissions, as determined by the mouse skin initiation assay, were within a factor of 2 of those determined using the epidemiologic data. The relative potencies, from the in vitro bioassays as compared to the human data, were similar for coke oven and roofing tar, but for the cigarette smoke condensate the in vitro tests predicted a higher relative potency. The mouse skin initiation bioassay was used to determine the unit lung cancer risk for the most potent of the diesel emissions. Based on comparisons with coke oven, roofing tar, and cigarette smoke, the unit cancer risk averaged 4.4 × 10−4. The unit lung cancer risks for the other, less potent motor-vehicle emissions were determined from their comparative potencies relative to the most potent diesel using three in vitro bioassays. There was a high correlation between the in vitro and in vivo bioassays in their responses to the engine exhaust particulate extracts. The unit lung cancer risk per μg particulates per m3 for the automotive diesel and gasoline exhaust particulates ranged from 0.20 × 10−4 to 0.60 × 10−4; that for the heavy-duty diesel engine was 0.02 × 10−4. These unit risks provide the basis for a future assessment of human lung cancer risks when combined with human population exposure to automotive emissions.
TL;DR: Rainbow trout, fathead minnows and Daphnia magna were exposed to silver for 96 h in replicated flow-through tests in replicated static acute tests as mentioned in this paper.
Abstract: Rainbow (Salmo gairdneri) and steelhead (Salmogairdneri) trout and fathead minnows (Pimephales promelas) were exposed to silver for 96 h in replicated flow-through tests. Rainbow trout, fathead minnows and Daphnia magna were exposed to silver in replicated static acute tests. Steelhead trout embryo-larval stages were tested in a flow-through system for 60 d, and D. magna were exposed through complete life cycles in replicated static-renewal tests. All silver concentrations were measured values. No differences were seen between flow-through and static LC50 values. Rainbow trout 96-h flow-through LC50 values were 8.6 and 9.7 μg/L silver; static values were 10.9 and 8.5 μg/L. The 96-h LC50 for steelhead trout in the flow-through test was 9.2 μg/L. Fathead minnow 96-h flow-through LC50 values were 5.6 and 7.4 μg/L silver; static values were 9.4 and 9.7 μg/L. The absence of food in static tests with D. magna caused silver to be about 10 times more toxic; the 48-h static mean EC50 value for D. magna without food was 0.9 μg/L, compared to 12.5 μg/L in the test with food. The early-life-stage test with steelhead trout, from newly fertilized eggs to post-swimup juveniles, showed complete mortality at 1.3 μg/L and significant reduction in fish survival at 0.5 μg/L silver. Mean weight and length at end of test were greatly reduced at 1.1 μg/L, and were significantly different from controls at 0.1 μg/L. The mean 21-d EC50 value for the D. magna test with food was 3.5 μg/L. The 21-d lowest significant (α = 0.05) effect on survival occurred at 4.1 μg/L. The mean silver concentration at which there was a significant decrease in total Daphnia young/female/day after 21 d, compared to the control was 10.5 μg/L silver.
TL;DR: A 1978 Denver aerosol data set has been analyzed by a variety of methods for determining light scattering and extinction coefficients per unit mass concentration for specific chemical species in fine particles as mentioned in this paper.
TL;DR: The use of behavioral endpoints in environmental hazard and impact assessment has become a major field of study in recent years as discussed by the authors, however, although behavior has always been accepted as an important aspect of animal survival and ecology, toxicological research over the past two decades has concentrated primarily on lethality, growth, and reproductive success.
Abstract: The use of behavioral endpoints in environmental hazard and impact assessment has become a major field of study in recent years. Although behavior has always been accepted as an important aspect of animal survival and ecology, toxicological research over the past two decades has concentrated primarily on lethality, growth, and reproductive success. Behavioral toxicology has lagged in areas of impact assessment for several reasons: (1) difficulties in objectively quantifying behavioral endpoints, (2) variability associated with the endpoint, (3) lack of standardized testing procedures which would provide more comparable data, and (4) difficulties in extrapolating to field situations the ecological significance of effects observed in the laboratory. These problems certainly are not unique to ethological testing but have proven to be obstacles to its success as an impact assessment tool.
TL;DR: Assessing in the field acidification effects on macroinvertebrate communities and populations of fathead minnows foundFathead minnow spawning and embryo production were similar in the ambient and pH 6 channels with little spawning and no eyed-embryos found in the pH 5 channel.
TL;DR: Fathead minnows (Pimephales promelas) were exposed to Dursban during a chronic toxicity test for 200 days including a reproductive period of their life cycle, and brain acetylcholinesterase activity was significantly inhibited.
TL;DR: Bioluminescent dinoflagellates increased the number of high-speed swimming bursts by the copepods and thus decreased the amount of slow- speed swimming characteristic of their grazing behavior, which should result in reduced grazing by theCopepods on bioluminellates.
Abstract: The horizontal swimming patterns of groups of Acartia hudsonica were tracked and described using a video-computer system. The patterns were compared in the presence of clones of bioluminescent and nonbioluminescent Protogonyaulax tamarensis. Bioluminescent dinoflagellates increased the number of high-speed swimming bursts by the copepods and thus decreased the amount of slow-speed swimming characteristic of their grazing behavior. With bioluminescent dinoflagellates, swimming paths were less circuitous and swimming speeds higher. This behavior may tend to move copepods away from bioluminescent dinoflagellates in nature. Both changes in swimming behavior should result in reduced grazing by the copepods on bioluminescent dinoflagellates.
TL;DR: The relationship of swimming speed to predator — prey interactions of the nauplii using both real and simulated predators was investigated and Nauplii exposed to Cu for 24 h were observed to be generally hyperactive, a condition which could increase their encounter frequency with predators.
Abstract: In this study we demonstrate the sensitivity of swimming behavior and predator-escape responses of nauplii of the estuarine copepod Eurytemora affinis to sublethal doses of Cu and Cd. Behavior was generally altered at metal doses below those affecting growth rates or survival of the copepods. Swimming velocities of Cu-dosed nauplii were different from controls at all concentrations of Cu tested (10–50 μg l-1 total Cu) after 24- to 48-h exposure, whereas development rate of nauplii was significantly reduced only after 96 h at 25 μg l-1. The 96 h LC50 for Cu was approximately 30 μg l-1 Cu. Naupliar swimming velocity was also affected by Cd. Swimming speeds were reduced after 24 h at 130 μg l-1, and development was slowed after 48 h at 116 μg Cd l-1. The 96-h LC50 was >120 μg l-1. Little is known of the adaptive role of specific motile behaviors in the success of larval copepods. We investigated the relationship of swimming speed to predator — prey interactions of the nauplii using both real and simulated predators. Nauplii exposed to Cu for 24 h were observed to be generally hyperactive, a condition which could increase their encounter frequency with predators. Reduced numbers of escape responses of nauplii to a simulated predator, another indication of increased vulnerability to predation, were observed only after 48-h exposure to Cu. Nevertheless, feeding rates of non-dosed larval striped bass on dosed nauplii (24 h at 25 μg Cu l-1) were significantly higher than on control nauplii. Feeding rates of larval mysid shrimp, however, were not higher on similarly dosed nauplii; 24 h exposure of nauplii to >30 μg Cu l-1 did result in increased predation by mysids.
TL;DR: In this article, an experimental study of the stratified flow over triangular-shaped ridges of various aspect ratios is described, where flows were produced by towing inverted bodies through saline-water solutions with stable (linear) density gradients.
Abstract: An experimental study of the stratified flow over triangular-shaped ridges of various aspect ratios is described. The flows were produced by towing inverted bodies through saline-water solutions with stable (linear) density gradients. Flow-visualization techniques were used extensively to obtain measurements of the lee-wave structure and its interaction with the near-wake recirculating region and to determine the height of the upstream dividing streamline (below which all fluid moved around, rather than over the body). The Froude number F(= U/Nh) and Reynolds number (Uh/ν), where U is the towing speed, N is the Brunt–Vaisala frequency, h is the body height, and ν is the kinematic viscosity, were in the nominal ranges 0.2–1.6 (and ∞) and 2000–16000 respectively. The study demonstrates that the wave amplitude can be maximized by ‘tuning’ the body shape to the lee-wave field, that in certain circumstances steady wave breaking can occur or multiple recirculation regions (rotors) can exist downstream of the body, that vortex shedding in horizontal planes is possible even at F = 0.3, and that the ratio of the cross-stream width of the body to its height has a negligible effect on the dividing streamline height. The results of the study are compared with those of previous theoretical and experimental studies where appropriate.
01 Jan 1983
TL;DR: In this article, the authors assess the sunlight photoreactivity of new pesticides and their transformation products in various environmental compartments by considering both the kinetic and photoproduct distributions.
Abstract: Assessing the sunlight photoreactivity of new pesticides has become common- place in the last decade in recognition of the effects the sun has on the dissipation rate of organic chemicals and their transformation products in various environmental compartments. Several reviewers have summarized research dealing with both the kinetic aspects (Zepp and Cline 1977, Smith et al. 1977, Zepp 1979 and 1980, Zepp and Baughman 1978) and the photoproduct distributions (Sundstrom and Ruzo 1978, Crosby 1979. Moilanen et al. 1975).
TL;DR: In this paper, a map illustrates the regional patterns of mean annual alkalinity of surface water in the conterminous United States, and affords a qualitative graphic overview to the sensitivity of surface waters to acidification.
Abstract: This map illustrates the regional patterns of mean annual alkalinity of surface water in the conterminous United States. As such, it affords a qualitative graphic overview to the sensitivity of surface waters to acidification. The map is based on data from approximately 2500 streams and lakes and apparent spatial correlations between these data and macro-watershed characteristics, especially land-use.
01 Oct 1983
TL;DR: In this article, the bioaccumulation of polychlorinated biphenyls (PCBs), mercury, and cadmium by sandworms (Nereis virens), hard clams (Mercenaria mercenaria ), and grass shrimp (Palaemonetes pugio ) exposed to contaminated sediments from four sites in New York Harbor was studied for a 100-day period.
Abstract: Accumulation of polychlorinated biphenyls (PCBs), mercury, and cadmium by sandworms ( Nereis virens ), hard clams ( Mercenaria mercenaria ) and grass shrimp ( Palaemonetes pugio ) exposed to contaminated sediments from four sites in New York Harbor was studied for a 100-day period. Of the three contaminants monitored, only PCBs were found to bioaccumulate above background (control) concentrations. Small increases in PCB body burden were detected in M. mercenaria and P. pugio , whereas higher concentrations were measured in N. virens . Uptake was affected by the organic content of the sediment. Bioaccumulation factors (concentration in tissue/concentration in sediment) for N. virens ranged from 1.59 in a low organic sediment to 0.15 in a high organic sediment. Results from this study support the contention that sediment concentration alone does not reflect bioavailability and that toxicity tests (bioassays) and field monitoring remain the most direct method for estimating bioaccumulation potential of sediment-bound contaminants.
TL;DR: Toxicity tests were conducted with selected compounds listed by the United States Environmental Protection Agency as priority pollutants to estimate chronic toxicity and the estimated maximum acceptable toxicant concentration for silver nitrate lies between 0.37 and 0.65 micrograms/liter.
TL;DR: The results indicate that isolated hepatocyte suspensions are useful for the identification of cytotoxins in general and hepatotoxin in particular, but that their capability for yielding a quantitative index of cytOToxic potential for diverse chemical species remains to be demonstrated.
Abstract: Thirty‐four chemicals‐diverse in structure, postulated mechanisms of action, and primary target organs‐were tested for cytotoxic response in isolated hepatocyte suspensions from young male Sprague‐Dawley rats. Hepatocytes were incubated in the presence and absence of the test chemicals in closed vessels fitted with side arms for serial sampling for up to 5 h at 37°C with gentle shaking under an O2:CO2 (95:5) atmosphere. The parameters evaluated were glutamate‐oxaloacetate transaminase and lactate dehydrogenase release from the cells, Trypan blue exclusion, cell count, urea synthesis capability, and steady‐state ATP levels. All chemicals cytotoxic in animals following single or short‐term repeated exposures caused statistically significant changes in one or more of these parameters in the 0.01–70‐mM concentration range. Dimethylnitrosamine and thioacetamide were not as potent in the isolated cell system as expected from their in vivo hepatotoxicity, and the quantitative changes produced with thioacetamide ...
TL;DR: In this article, it was shown that these microorganisms may, under certain circumstances, transform many of the organic pollutants that enter the subsurface environment, which can lead to total destruction of the pollutant or to the production of new organic pollutants.
Abstract: Recent investigations have discovered surprisingly high numbers of microorganisms in shallow water-table aquifers. Evidence is accumulating that these microorganisms may, under certain circumstances, transform many of the organic pollutants that enter the subsurface environment. These transformations can lead to total destruction of the pollutant or to the production of new organic pollutants.
TL;DR: The ability to accurately calculate a water dose in micrograms per kilogram per hour for individual fish that could be directly compared to other fish species or to mammals is demonstrated.
TL;DR: In this paper, the types of products identified, relationships of products to reactants from smog chamber studies, and ambient air concentrations and distributions are considered in a review. But none of the other products are present individually at concentrations approaching that of O3.