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Results for “Maximum Allowable Concentration”

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At least 19 recordsLinked to original sources
PubMed1979

[Modular way of sampling for determination of the degree of occupational exposure at industrial plants with periodically changing dust concentration].

A work station with dustiness changing periodically during a workshift is one of the most common types of work stations, as regards exposure dynamics. Cyclic significant concentrations of dust occurring from time to time result from a specific technological treatment used. The measuring module will be the time of measurement, starting with the beginning of the cycle of working out a given detail or--the technological process through the whole treating and technological process as well as breaks--due to various reasons--until starting another, analogous operation. What was found is that average dust concentrations obtained from modular measurements correspond to average concentration to which an employee is exposed during the whole workshift. Modular measurements allow to reconstruct work conditions inducing silicosis, and may be helpful in settling the maximum allowable concentration.

Air Pollutants↗
PubMed1976

Subchronic inhalation toxicity of azinphos-methyl in rats.

Azinphos-methyl was evaluated for its subchronic inhalation toxicity. The exposure of rats to concentrations of 0.195, 1.24, and 4.72 mg/m3, respectively, for 12 weeks, 6 hrs daily, 5 times weekly, resulted in effects only in those animals which inhaled aerosols of the highest concentration. This group showed a significant depression of the cholinesterase activity in plasma and erythrocytes. The males of this group had a lower body weight gain. The results are in agreement with the established maximum allowable concentration of 0.2 mg/m3.

Aerosols↗
PubMed1977

[Experimental substantiation of the maximum permissible concentration of Reglone in the air of a work environment].

Reglon (20 per cent dikwad dibromide) is an extensively used herbioide and desiccant. During acute and chronic inhalatory experiments on white rats, using 4--hour exposure to water aerosols, determination is made of the acute LC50 -- 83 mg/m3, of the acute threshold concentration - 9.9 mg/m3 acute substance, as well as of the chronic threshold concentration - 0.32 mg/m3. In all instances the clinical picture of intoxication is characterized by pulmonary lesion, and partial involvement of liver and kidneys. The computed zones of acute and chronic inhalatory toxicity warrant the assumption that no sequelae dueto herbicide cumulation in the organism should be expected. At safety coefficient 3, the authors propose 0.1 mg/m3 dikwad dibromide as a temporary limit of the maximum allowable concentration of reglon in the working environment air.

Air Pollutants↗
PubMed1979

[Health effects of trichloroethylene in human subjects (author's transl)].

Trichloroethylene has been widely used for the removal of grease in dry cleaning, plate and painting industries, in which approximately 280 thousand workers contact trichloroethylene, for example, in the United States, resulting in acute and chronic poisonings. Based on 203 papers mainly on trichloroethylene toxicity on human beings, the present review covers acute toxicity, chronic toxicity, carcinogenicity, factors modifying toxicity, metabolism, dose-response relationships and maximum allowable concentration of this chemical. 1 figure and 12 tables.

Acute Disease↗
PubMed1978

Styrene, its metabolism and the evaluation of hazards in industry.

The main products of styrene biotransformation excreted in human urine are mandelic and phenylglyoxylic acids. Phenylethylene oxide seems to be the first metabolite; this compound has been reported to be mutagenic and carcinogenic. The polarographic determination of mandelic acid has been used for about 20 years in Czechoslovakia as an exposure test for persons occupationally exposed to styrene. Only single cases of health damage have been reported to be due to styrene exposure during this time. Recently, however, elevated frequencies of chromosomal aberrations in peripheral lymphocytes have been observed in persons exposed to styrene in Czechoslovakia. The amount of phenylethylene oxide that can be formed in the human body during exposure to 50 ppm of styrene in air during a workshift is about 0.7 g. It would be hardly justifiable now to believe that styrene is not carcinogenic and mutagenic in man. The present Czechoslovakian maximum allowable concentration of styrene (200 mg/m3) should be reduced, and the concentration of 50 mg/m3 may be recommended as reasonable at this time. The corresponding biological limit value of mandelic acid might be 300 mg/l of urine from the last 2 h of the workshift.

Air Pollutants↗
PubMed1979

Toxicological studies of shale oils, some of their components, and commercial products.

Estonian shale oil contains about 25--30% phenols, and their action determines the toxicity of shale oils. The clinical symptoms of intoxication are rather similar, regardless of route of administration. Due to neurotropic action, the coordination of movements is impaired, and clonic and tetanic convulsions, paresis and paralysis of extremities, and narcosis are observed. In subacute and chronic toxicity tests, dysfunction of the central nervous system was found. In long-term (4--6 month) experiments, changes in liver and kidney function were found. Shale oil has gonadotropic activity and causes changes in the sexual cycle as well as diminution of the number of primordial folicles in the ovaries or a decrease in the quantity of normal spermatogonia in testicular germinal epithelium. Shale oils produce local irritation of skin and mucous membranes. Shale oil can induce sensitization of the organism after repeated administration. The results of acute intoxication tests have proved that volatile and nonvolatile phenol fractions, isomeric dimethylphenols, and 5-methylresorcinol, must be characterized as moderately toxic substances; the LD50 ranges from 501 to 1500 mg/kg. The clinical symptoms of acute toxication are similar for all studied phenols (restlessness, unsteadiness, clonic tremor, paresis and paralysis of extremities, and death). In spite of the moderate toxicity of phenols in acute experiments, repeated administration of small doses can cause different changes in the nervous system and internal organs of experimental animals. For all the phenols studied, the maximum allowable concentration in water was limited by their effect on the organoleptic properties of water. The nonactive dose for warm-blooded animals is from 100 to 3000 times the threshold limit value of phenols on the basis of their organoleptic properties. The effect of commercial products of oil shale industry is generally determined by the toxicity of the main components: water-soluble oil shale phenols.

Animals↗
PubMedDate not supplied

Chromosome aberrations induced by occupational exposure to mercury.

The incidence of chromosome aberrations was studied by peripheral blood incubation (52 hr, the last 4 hr in the presence of Colcemid) using a modification of the Evans' technique in twenty-two men exposed to either vapors of metallic mercury (Group I) or organic mercury (Group II). Mercury concentrations of the work areas frequently exceeded the Maximum Allowable Concentrations in the past. During the year proceding the investigation, mercury values ranged between 0.15 and 0.44 mg/m3. None of the investigated men were poisoned, but all had had repeated increased mercury absorption with urinary eliminations reaching 890 microgram/l and 896 microgram/l for subjects in Groups I and II, respectively. The incidence of chromosome aberrations was significantly higher (P less than .001) in subjects exposed to mercury as compared with a control group (ten subjects) of a similar mean age. There was no statistical difference in the incidence of chromosome aberrations between men belonging to Groups I and II. Although an increase of both chromatid gaps and breaks was noticed in exposed men, the incidence did not significantly differ from controls. No chromatid interchanges were recorded and no difference between exposed and control subjects was noticed concerning the frequency of aneuploid or polyploid cells.

Adult↗
PubMed2026

A quantitative microbial risk assessment of activated carbon point-of-use filters and the risk of Legionella pneumophila.

Activated carbon point-of-use (POU) filters have become increasingly popular. Often certified to remove lead and improve water taste, these filters are not certified to remove bacteria. In this study, we examined the effects of using POU filters on the risk posed by Legionella pneumophila (L. pneumophila) in a quantitative microbial risk assessment model. Release rates of L. pneumophila were measured for new and artificially aged (ripened) POU filters. Additionally, we measured aerosol concentrations produced by water fixtures that might have a POU filter (e.g., drinking fountain bubbler, faucet). We modeled scenarios without filters (with and without residual chlorine) and with filters (new and ripe filters), four water usage activities (drinking from a drinking fountain, handwashing, dishwashing, and showering), and three age groups (children, adults, and elderly). Systems with the highest to lowest risk were those without filters and without chlorine, those with ripe filters, those without filters and with chlorine, and finally, those with new filters. The risk of illness decreased for activities with shorter exposure times, such as drinking and handwashing. The L. pneumophila concentrations, aerosol concentrations, and exposure time had the largest impacts on the risk of illness. The maximum allowable concentration of L. pneumophila needed to achieve a 10-4 target annual risk of illness was 0.02 copies/mL. This study showed that POU filters may reduce L. pneumophila risk but only if the filter is new (≤ 1 week old before the filter ripens significantly), and other strategies for reducing L. pneumophila concentrations or decreasing exposure time may be needed to further decrease the risk of illness.

Legionella pneumophila↗
PubMed1979

[The levels of heavy metals (Cd, Cu, Hg, Ni, Pb, Zn) in brook trouts from the River Leine in the area of Göttingen (West Germany) (author's transl)].

In order to evaluate the load of heavy metals (Cd, Cu, Hg, Ni, Pb, Zn) imposed on the River Leine by the city of Göttingen (medium-sized town) the content of heavy metals in fish samples (which had been collected at two points on the River Leine, upstream, respectively downstream of Göttingen--Fig. 1) were determined by Atomic Absorption Spectroscopy. Analysis of heavy metals in brook trout (total fish, flesh, and liver) showed a statistically significant definite increase in some heavy metals, caused by the sewage from the city of Göttingen. In the flesh only Cd in the liver Cd, Hg and Zn and in the total fish Cd, Cu and Zn had been increased significantly. All the values of heavy metals in the flesh were lower than the suggested maximum allowable concentrations.

Animals↗
PubMed1978

Methodology of the study of carcinogens in human populations.

Epidemiology, including occupational tumors and other groups at risk; experimental studies; and physiochemical methods of evaluation of environmental carcinogens form the basis of cancer prevention. Hygienic measures of limitation (maximum allowable concentrations) are also discussed.

Air Pollutants↗
PubMed1979

A critique of the U.S. standard for industrial exposure to sodium hydroxide aerosols.

Published studies of the toxicity of sodium hydroxide aerosols are few. These studies were generally marred by inadequate characterization of particle size and chemical compositon and of the ambient humidity. Because NaOH aerosols can readily undergo reaction with carbon dioxide to form sodium carbonate, a much less alkaline (and less hygroscopic) compound, these shortcomings may warrant a reconsideration of the NaOH standard and the consideration of a Na2CO3 standard.

Aerosols↗