Maximum Acceptable Concentration Research Articles

Tile Effluent Quality and Chemical Losses Under Conven-tional and No Tillage — Part 2: Atrazine and Metolachlor

The long-term effect of no-tillage (NT) and conventional tillage (CT) on the concentration and loss of the atrazine, deethylatrazine and metolachlor in tile effluent was studied over a 40-month period in four loam soil, corn (Zea mays L.) fields of approximately 3 ha each. Atrazine and deethylatrazine were detected at low concentrations in most of the 773 samples collected between January 1991 and early May 1994. Under both tillage treatments, atrazine concentrations were mostly below the USEPA advisory of 3 mg/L while concentrations of atrazine plus deethylatrazine were generally below 5 mg/L, the Canadian Interim Maximum Acceptable Concentration (IMAC) for the sum of atrazine and its metabolites. Concentrations exceeding these limits were mainly observed during rainfall-induced flow events within a few days or weeks following herbicide application. The flow-weighted average concentrations of atrazine during flow events were significantly (p < 0.05) higher under NT than CT. Metolachlor was also detected at low concentrations, and in relatively few flow events. Concentrations were always well below the USEPA advisory of 100 mg/L or the Canadian IMAC of 50 mg/L. Annual loss of herbicides in tile effluent ranged from 0.02% to 0.34% of the amount applied. Most loss occurred during spring flow events when tile flow was the highest. Atrazine and deethylatrazine losses under the NT treatment were significantly (p < 0.05) higher than those under the CT treatment.

Removal of selenium from water and wastewater

It is well established that the presence of selenium in drinking water in higher concentrations has toxic effects on both humans and aquatic life. A maximum acceptable concentration of 10 μg/L has been specified for selenium in drinking water by the federal and provincial regulatory agencies. Selenium finds extensive application in the manufacture of photocells, rectifiers, xerography equipment, paint, glass and insecticides. Selenium concentration in industrial effluents may vary from 1 to 7000 μg/L. This paper reviews various treatment technologies for the removal of selenium from water and wastewater such as sedimentation, filtration, activated carbon adsorption, ion exchange, reverse osmosis and biological treatment.

Chronic toxicity of 14 phthalate esters to Daphnia magna and rainbow trout (Oncorhynchus mykiss)

AbstractChronic toxicity studies were performed with commercial phthalate esters and Daphnia magna (14 phthalates) and rainbow trout (Oncorhynchus mykiss) (six phthalates). For the lower‐molecular‐weight phthalate esters–dimethyl phthalate (DMP), diethyl phthalate (DEP), di‐n‐butyl phthalate (DBP), and butylbenzyl phthalate (BBP)–the results of the studies indicated a general trend in which toxicity for both species increased as water solubility decreased. The geometric mean maximum acceptable toxicant concentration (GM‐MATC) for D. magna ranged from 0.63 to 34.8 mg/L. For the higher‐molecular‐weight phthalate esters–dihexyl phthalate (DHP), butyl 2‐ethylhexyl phthalate (BOP), di‐(n‐hexyl, n‐octyl, n‐decyl) phthalate (610P), di‐(2‐ethylhexyl) phthalate (DEHP), diisooctyl phthalate (DIOP), diisononyl phthalate (DINP), di‐(heptyl, nonyl, undecyl) phthalate (711P), diisodecyl phthalate (DIDP), diundecyl phthalate (DUP), and ditridecyl phthalate (DTDP)‐the GM‐MATC values ranged from 0.042 to 0.15 mg/L. Survival was equally sensitive and sometimes more sensitive than reproduction. The observed toxicity to daphnids with most of the higher‐molecular‐weight phthalate esters appeared to be due to surface entrapment or a mode of toxicity that is not due to exposure to dissolved aqueous‐phase chemical. Early life‐stage toxicity studies with rainbow trout indicated that survival (DMP) and growth (DBP) were affected at 24 and 0.19 mg/L, respectively. This pattern of observed toxicity with the lower‐molecular‐weight phthalate esters and not the higher‐molecular‐weight phthalate esters is consistent with previously reported acute toxicity studies for several aquatic species.

Atrazine and nitrates in the drinking ground water of the Chamusca agricultural area (Portugal)

An evaluation of the potential to reach the ground water compartment of the main applied pesticides in maize fields of the Chamusca agricultural area have indicated atrazine as the most probable contaminant. The use of nitrogen fertilizers in the aforementioned irrigated area also suggested a possible presence of nitrates in ground water. Results of atrazine and nitrate levels in drinking ground water of four locations in the studied area are reported. Residues were detected in three locations and in one of them levels were found above the maximum acceptable concentrations defined by the European Community. The simultaneous presence of atrazine and nitrates in the most affected site suggests a potential health risk.

Predicting chronic lethality of chemicals to fishes from acute toxicity test data: Theory of accelerated life testing

AbstractA method for modeling aquatic toxicity data based on the theory of accelerated life testing is presented, and a procedure for maximum likelihood fitting the proposed model is developed. The procedure is computerized as software, which can predict chronic lethality of chemicals using data from acute toxicity tests. A database of various chemicals and fish species was analyzed. When the calculated values of prediction were compared to the maximum acceptable toxicant concentrations obtained from actual chronic toxicity experiments, the new technique provided accurate predictions. Problems in using the “maximum acceptable toxicant concentration” and applications of the proposed method are discussed.

Pesticide Leaching Associated with Conventional Potato and Corn Production in Atlantic Canada

Abstract We employed field-scale tile drainage systems, private wells in farming areas, and research piezometers installed al field edge to evaluate nonpoint source impacts of four pesticides on groundwater quality. Nitrale-N was known to be teaching at all study sites. Herbicides dinoseb and metribuzin and the fungicide chlorothalonil were common to potato production; the herbicide atrazine was common to com production. Based on chemical properties, chlorothalonil is unlikely to leach, while atrazine, dinoseb and metribuzin are identified as potential leachers. In this study, chlorothalonil leaching was indeed very limited; only 4 of 66 tile drainage samples were positive, and al concentrations close to the detection limit (0.005 µg L−1). Chlorothalonil was not detected in any of the farm wells or research piezometers located in areas of intense potato production. Conversely, atrazine, dinoseb and metribuzin were confirmed as nonpoint source leachers. They were often detected in tile drainage water and have been detected in wells, but at mean annual concentrations less than current maximum acceptable concentrations for drinking water as established by Health and Welfare Canada.

Pesticides, Nitrate-N and Bacteria in Farm Wells of Kings County, Nova Scotia

Abstract Water samples collected from 102 farm wells in the most intensively farmed region in Nova Scotia were analyzed for pesticides, nitrate-N and coliform bacteria. An additional 135 wells were sampled for nitrate-N only. None of the study wells contained pesticide concentrations above maximum acceptable concentrations for Canadian drinking water; however, very low pesticide levels were found in 41% of the wells. Atrazine was the most prevalent pesticide, occurring in 79% of the wells with detections. Nitrate-N and coliform bacteria exceeded the guidelines in 13 and 9% of the study wells, respectively. Statistical analysis of the data indicated that pesticide contamination was generally not related to well construction and surficial material parameters, but some correlations were found for nitrate-N and bacterial contamination. Case studies indicated that the majority of pesticide occurrences were attributable to nonpoint sources. Atrazine contamination may be the result of historic use rather than current agricultural practices.

CART Decision-Tree Statistical Analysis and Prediction of Summer Season Maximum Surface Ozone for the Vancouver, Montreal, and Atlantic Regions of Canada

Prediction of daily maximum surface ozone (O3) concentration was begun by Environment Canada in the spring of 1993 for the Vancouver, Montreal, and Atlantic regions in order to advise the public of expected air quality. Forecasts have been issued for southern Ontario for many years by the province of Ontario, but this is a new undertaking in other parts of the country, where air quality has become a concern in recent years. There is a need for guidance to prepare the forecasts, particularly for prediction of surface O3 concentration levels near or exceeding the Canadian 1-h maximum acceptable concentration of 82 ppb. Such occurrences are episodic and relatively rare in southern Canada. Probability of occurrence is in the range 0.00–0.08 at the sites in the regions studied here, thus, reliable prediction is difficult without guidance. Mesoscale numerical meteorological–photochemical models are not currently available for routine use in operations, but the capability exists for development and use of sophisticated multivariate statistical techniques for prediction of daily maximum O3 concentration. Most statistical ozone forecast procedures to date in Canada have been based on multiple linear regression with a limited number of predictors mainly drawn from surface meteorology and subjective classification of the synoptic meteorological flow pattern. Since the relationship between surface O3 and meteorology is nonlinear, tree-based statistical models with several predictors are appropriate for developing objective forecast guidance. Surface and upper-air meteorological predictors and other predictors were matched with several years of observed daily maximum O3 concentrations for the months of May–September at air-monitoring sites in the three regions. A recent nonparametric data-driven tree-based analysis method known as CART (classification and regression trees) was used to analyze the data at each site. The decision trees built by CART were found to fit the data reasonably well, and the rules for node splitting were found to be physically realistic. Some of the important aspects of the analyses are noted. One interesting result was that moisture content of the air plays a limiting role on the maximum surface O3 concentration that can be achieved when other factors point to occurrence of high values. The decision trees can be used to predict maximum surface O3 concentrations if the predictor variables are forecast, thus providing an inexpensive site-specific model for forecasts and climate impact analysis. An estimation of performance with independent data was conducted for the Vancouver–lower Fraser River valley and Montreal regions for each of the five years 1988–92. Verification of the ensemble of forecasts in the two regions shows the technique would have reasonably good skill in forecasting surface O3 concentrations near or exceeding acceptable 1-h limits. A computer version of the technique has been provided for use in the regional forecast offices.

The toxicity of cyromazine to Chironomus zealandicus (chironomidae) and Deleatidium sp. (leptophlebiidae)

AbstractThe toxicity of cyromazine and a commercial formulation, ‘Vetrazin’®, to Chironomus zealandicus (thummi) Hudson and Deleatidium sp. was investigated. Under acute test conditions, the LC50 values for each species were quite comparable. For C. zealandicus, the value varied according to instar, 100–400 mg litre−1 for second‐ and third‐instar to 1000–10000 mg litre−1 for older fourth‐instars. For the one size class of Deleatidium tested (c.10 mm long), the value was 300–400 mg litre−1. High control mortalities of C. zealandicus limit that species' usefulness as an acute bioassay candidate. Under chronic test conditions, cyromazine showed a high toxicity to eggs or early‐instar larvae of C. zealandicus. The maximum acceptable toxicant concentration for cyromazine against C. zealandicus was approximately 17.5 μg litre−1. The possibility of water contamination at this level is discussed. Whole‐of‐life chronic tests with C. zealandicus indicated that the most susceptible stage was in the egg or soon after larval emergence. These results highlight the dangers of using short‐term acute toxicity results to formulate environmental exposure limits for modern pesticides that do not have dysfunction of the nervous system as their mode of action.

Effects of heavy metals on the survival ofDiacypris compacta (Herbst) (Ostracoda) from the Coorong, South Australia

The hypermarine southern Coorong is threatened by proposals to drain relatively fresh surface water and groundwater from adjacent agricultural areas into the Coorong. These influent waters carry moderate loads of heavy metals. Acute toxicity of heavy metals toDiacypris compacta, an abundant ostracod in the Coorong, was measured in the laboratory at 18°C in a static system using Coorong water (pH 7.8 salinity 50 ppt). At 4 days (96 h) the mean values of LC50 for copper, zinc, lead and, cadmium respectively were 0.8, 2.1, 3.1 and 4.3 mg L−1, and at 8 days the respective mean LC50s were 0.4, 0.7, 2.2 and 1.1 mgL−1. The effect of two or three metals on mortality was additive in some cases and synergistic in other cases, but generally less than additive. However, in all cases mortality was greater in the presence of two or three metals than in the presence of a single metal. According to ANZECC (1992) guidelines, maximum acceptable concentrations of heavy metals should be no higher than 0.01 x the lowest LC50 value. Using the lowest LC50 values forDiacypris compacta obtained at 8 days, maximum acceptable concentrations in the Coorong would be 4, 5, 9 and 22 μgL−1 for copper, zinc, cadmium and lead respectively, the values for zinc and copper failling below those recommended by ANZECC (1992) for marine waters. Reported concentrations of copper and zinc in surface water and groundwater in areas adjacent to the Coorong sometimes exceed these values, hence drainage of these waters into the Coorong represents a significant hazard to the Coorong biota.

Acute and long-term effects of nine chemicals on the Japanese medaka (Oryzias latipes).

Ninety-six-hour acute and 28-day larval survival and growth tests were conducted with nine organic chemicals, using the Japanese medaka (Oryzias latipes) as the test organism. The nine tested chemicals were allyl isothiocyanate, aniline, benzyl acetate, 4-chloroaniline, 2-chloroethanol, 2,4-diaminotoluene, 1,2-dibromoethane, 2,4-dichlorophenoxyacetic acid (2,4-D), and phenol. The derived 96-h LC50 values for medaka for all chemicals ranged from 0.077 mg/L for allyl isothiocyanate to 2,780 mg/L for 2,4-D. The chronic values for six of the nine chemicals tested ranged from 0.013 mg/L for allyl isothiocyanate to 42.5 mg/L for 2,4-D. Acute-to-chronic ratios for these six chemicals ranged from 1.4 for 2-chloroethanol to 70.9 for 2,4-D. Growth of medaka was significantly reduced in the lowest exposure concentration during 28-dy larval tests with aniline, 4-chloroaniline, and 2,4-diaminotoluene. The estimated maximum acceptable toxicant concentration was reported as less than the lowest exposure concentration of 4.6, 2.2 and 40.3 mg/L for tests with aniline, 4-chloroaniline and 2,4-diaminotoluene, respectively. Chronic values for 2-chloroethanol and medaka were 12.6 mg/L during an embryo-larval test and 22.1 mg/L during the 28-day larval test.

Health-Related Evaluation of Building Products based on Climate Chamber Tests

A procedure is developed for assessing the health effects of the emissions from building products. The procedure is based on: • emission rates measured in environment test chambers • a fixed standard room with fixed standard conditions • a maximum acceptable concentration in the indoor air of each of the chemical compounds emitted, Iv a maximum permissible contribution to Iv from building products. The procedure has two elements: evaluation of the emitted compound alone and evaluation of the compound together with other compounds and indoor air factors. The evaluation includes odour and health effects of the compounds. The procedure has been applied to the emission test results for two building products: a rubber floor covering, and a water-borne acrylic watt paint. Maximum acceptable indoor air concentrations are listed fin-selected chemical compounds emitted by these two materials.

Sublethal responses to pesticides of several species of australian freshwater fish and crustaceans and rainbow trout

AbstractSublethal responses of the fish Oncorhynchus mykiss, Galaxias maculatus, Pseudaphritis urvillii, and the crustacean Paratya australiensis to short‐term exposures to low concentrations of seven pesticides were compared under identical conditions. Parameters examined were hematocrit, leucocrit, plasma glucose, plasma protein, plasma chloride, muscle RNA and DNA, brain and muscle acetylcholinesterase activity, hepatic glutathione‐S‐transferase activity, hepatic glutathione, and somatic growth. The organisms were exposed to the following materials–the organophosphate insecticides acephate and fenitrothion; the phenoxyacetate herbicide MCPA‐Na; the triazine herbicides atrazine and cyanazine; the fungicide chlorothalonil, and the pyrethroid insecticide cypermethrin–as purified active ingredients in continuous flow through at constant temperature (12–15°C) for 10 or 20 d, with feeding, at five concentrations. Oncorhynchus mykiss was marginally the most sensitive fish species studied in terms of the number of responses to pesticide exposure, but not in terms of the LOECs. Interspecies comparisons indicated that water quality criteria based on juvenile Oncorhynchus mykiss toxicity data alone would not be suitable for the protection of juvenile and adult Galaxias maculatus and Pseudaphritis urvillii from physiological stress in at least three of seven cases. Four of seven maximum acceptable toxicant concentrations (MATCs) derived from physiological responses of fish species resulted from data on Galaxias maculatus and Pseudaphritis urvillii alone. In the case of organophosphates, the decapod crustaceans Paratya australiensis and Astacopsis gouldi were by far the most sensitive. Tentative water quality criteria for the protection of study species from short‐term stress are proposed.

Assessing the aquatic hazard of some branched and linear nonionic surfactants by biodegradation and toxicity

AbstractAn aquatic hazard assessment was conducted for branched and linear nonionic surfactants using toxicity and biodegradation measurements. Four nonionic alcohol ethoxylate surfactants with different degrees of branching (ranging from 0.1, essentially linear, to 4.0 internal methyl groups per hydrophobe) were evaluated for neat surfactant toxicity, degradation in laboratory sewage treatment units, and aquatic toxicity of treated effluents. Acute testing with neat surfactants showed ranges for EC50s of 1.3 to 11.6 mg/L for Daphnia, 1.6 to 6.1 mg/L for Pimephales promelas (fathead minnow), and 1.5 to 11.4 mg/L for Microtox®. Chronic testing of algae showed NOECs of 1 to 10 mg/L and maximum acceptable toxicant concentrations (MATCs) of 0.8 to 14.2 mg/L. Seven‐day chronic estimation tests showed MATCs of 0.6 to 41.4 mg/L for Pimephales promelas and 1 to 14 mg/L for Daphnia. Effluents collected from treatment units receiving a 50‐mg/L surfactant feed at 25°C showed no acute toxicity to either Daphnia or fathead minnows, with the exception of a unit containing nonylphenol ethoxylate. Chronic effluent toxicity was greatest in effluent from the nonyl‐phenol ethoxylate unit and least in the effluent from the linear alcohol ethoxylate unit. Chronic toxicity of the highly branched C13 alcohol ethoxylate effluent was greater than that for the linear alcohol ethoxylate unit effluent.

Immunologic monitoring during OKT3 therapy

The monoclonal antibody OKT3 is a potent immunosuppressant inducing both T‐cell depletion and antigenic modulation of the CD3/T‐cell receptor complex. CD3+ lymphocytes are cleared from the circulation within I hour of intravenous administration of OKT3. Periodic monitoring of remaining or reappearing CD3+ lymphocytes gauges the adequacy of OKT3 dosing and OKT3 consumption by anti‐OKT3 antibodies. The maximum acceptable concentration of CD3+ lymphocytes for maintaining the effectiveness of OKT3 therapy remains controversial due to variable sensitivity of the methods used. Intravenously administered OKT3 has a half‐life of approximately 18 hours and results in trough serum levels ranging from 500 to 1000 ng/ml in 3 to 4 days. The antibody response to OKT3 is oligoclonal, and both IgM and IgG antibodies to OKT3 may develop, showing restricted specificity; anti‐isotypic and/or anti‐idiotypic antibodies can be detected. The IgG anti‐idiotypic antibodies are the ones that neutralize the therapeutic activity of OKT3, and their specific detection involves the use of an immunofluorescence method that tests their ability to block the binding of OKT3 to normal T cells. The production of OKT3 antibodies has been shown to be affected by concomitantly administered immunosuppressive agents. Studies have demonstrated that OKT3 can be successfully reused in allograft recipients who do not present anti‐idiotypic blocking antibodies. The acute clinical syndrome regularly observed upon the first OKT3 injection is related to massive, although transient, release of several cytokines, which may be easily monitored with currently available radioimmunologic or immunoenzymatic tests.

Sorption of low levels of cyanide by granular activated carbon

ABSTRACT: The sorption of cyanide at levels ≤ 1 mg/L in solution by granular activated carbon (GAC) was investigated in order to define the conditions required to reduce residual levels to below the maximum acceptable concentration value specified in the Guidelines for Canadian Drinking Water Quality. The sorption process proceeded slowly with uptake continuing over a 30‐hour mixing period. The initial rate of adsorption increased with decreasing particle size of the activated carbon. In general, uptake was independent of pH except for a slight increase in the pH range of 8‐9, but increased linearly with increasing adsorbent density until the concentration of cyanide was lowered to approximately 0.3 mg/L; below 0.3 mg/L, the amount sorbed became proportional to a power‐law term of the adsorbent density. The effect of cyanide concentration on the uptake could be described by a Freundlich isotherm with the amount sorbed per unit weight of granular activated carbon being proportional to (Ce)0.13. Addition of up to 10 mg/L nitrilotriacetic acid had little effect on the amount of cyanide adsorbed; however, humic acid, Ca(II), Mg(II), Al(III), and Fe(III) reduced the cyanide uptake by 30‐50%. Possible mechanisms for cyanide sorption by GAC and their implications for water treatment have been considered. The mechanisms considered include CN− uptake by ion exchange, and sorption of cyanide as HCN molecules through formation of H‐bonds with oxygenated functional groups such as — COH.

Chronic toxicity of ammonia to juvenile gilthead seabream Sparus aurata and related histopathological effects

Effect of 20 days exposure of juvenile gilthead seabream (Sparus aurata) to elevated levels of ammonia on growth and survival was examined in a continuous flow system. Suppressed growth and reduced survival were observed at concentrations of 8.2 and 13 mg l−1 total ammonia‐N (0.5 and 0.7 mg l−1 un‐ionized ammonia‐N, respectively) and higher. The maximum acceptable toxic concentration (MATC) for growth was between 4.8 to 8.2 mg l−1 total ammonia‐N (0.3 and 0.5 mg l−1 un‐ionized ammonia‐N, respectively). Fish exposed to high ammonia levels (13 mg l−1 total ammonia‐N, 0.7 mg l−1 un‐ionized ammonia‐N) displayed clear signs of liver pathology. Existing evidence suggests that S. aurata is less sensitive to ammonia than other reported marine and freshwater fish.Under certain conditions ammonia concentration in the intensive fish ponds in Eilat may exceed the no observed effect concentration for S. aurata.

Removal of trace cadmium(II) by EDTA‐coated granular activated carbon

Abstract The factors influencing the uptake of trace cadmium by an ethylenediaminetetraacetate‐coated granular activated carbon (ECGAC) have been examined and optimum conditions determined. Variables investigated include agitation time, adsorbent dose (or suspension density), Cd(II) concentration and pH. At a substrate suspension density of 200 mg/L, pH of 5.4 and an agitation time of 18 h, uptake was approximately 90% from a solution of 25 μg Cd(II)/L. In comparison, the amount sorbed by uncoated granular activated carbon of 1.0–1.4 mm size fraction under the same conditions was only 5%. The maximum sorption capacity of ECGAC was about 0.4 mg Cd(II)/g (i.e., 3.6 μM/g). Under optimum conditions, it is possible to lower the Cd(II) level to below the maximum acceptable concentration of 5 μg/L specified in the Guidelines for Canadian Drinking Water Quality.

Toxic Chemical Survey of Municipal Drinking Water Sources in Atlantic Canada 1985-1988

Abstract During the period of 1985 to 1988, municipal water supply sources in Atlantic Canada were sampled and analyzed for various compounds including major ions, nutrients, heavy metals, pesticides and synthetic organic chemicals. Both surface and ground water sources were sampled. Ninety-eight percent of supply sources were within the health-related maximum acceptable concentrations of the Guidelines for Canadian Drinking Water Quality (Health and Welfare Canada 1987), and eighty-five percent within the aesthetic guidelines. A geographic information system was used to classify the municipal sources by surrounding land-use and comparisons made to nitrate-N. All samples reported as 1.0 mg.L−1 or greater were from ground water supplies in areas classed as high agricultural use. Though a direct input from agriculture was established for two wells, the source of nitrate-N at the remaining sites was attributed to soil-N and/or fertilizer-N.

Removal of trace mercury(II) from drinking water: Sorption by granular activated carbon

Abstract Optimum conditions were established for abstracting μg/L levels of Hg(II) species from aqueous solution and drinking water using the FS‐400 granular activated carbon (GAC) as adsorbent. The conditions were: system pH around 7, GAC suspension density of ≥100 mg/L, and a mixing or contact time of 1 h. Uptake of Hg(II) increased in the presence of 1–10 mg/L of humic acid, nitrilotriacetic acid (NTA) or Fe(III) salts; was little affected by Al(III) salts; and decreased when Ca(II) and Mg(II) levels exceeded 50 mg/L. The amount of Hg(II) adsorbed per unit weight of GAC varied with the initial concentration of Hg(II) until saturation was achieved. Under optimum conditions, the residual Hg(II) levels were below the maximum acceptable concentration (MAC) values given in the Guidelines for Canadian Drinking Quality.