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[Setting a maximum allowable concentration for urea in reclaimed potable water and evaluating the nature of its biological action].

The purpose of the study was to identify maxim allowable concentrations of urea in reclaimed potable water. The urea concentration equal to 80 mg/l is the threshold dose influencing the taste and flavor of water. Urea is a low toxicity substance (LD50 = 14,300 mg/kg), the effect of which is not cumulative. However, when used in high doses it affects bioenergetic and cholinergic processes and causes changes in ECG, higher nervous activity and visceral structure. It has been shown that when applied to warm-blooded animals the acting dose of urea is 14.3 and 1.43 mg/kg (1/1000 and 1/10000 LD50), the threshold dose is 0.72 mg/kg (1/20000 LD50), and the ineffective dose is 0.36 mg/kg (1/40000 LD50) which amounts to the concentration of 10 mg/l. In terms of toxic effects the dose equal to 10 mg/l is taken to be the maximally allowable concentration of urea. It is recommended to use the Laham biotest for measuring urea in water.

Animals↗
PubMed1991

[Experimental substantiation of maximum allowable concentration of phosphoric acid in the water of reservoirs].

It has been found out on the basis of experimental studies, that the threshold concentration of phosphorous acid is 85.7 mg/l according to the influence on organoleptic water properties, I mg/l--according to the influence on the sanitary regimen of water reservoirs. The preparation is of low toxicity when administered perorally to laboratory animals, cumulation degree is medium. Embryotoxic and gonadotoxic effects, mutagenic and allergic properties have not been detected. The maximum no-effect dose in the chronic experiment is 1.4 mg/kg. MAC is recommended on the level of I mg/l according to the general sanitary indicator of harmfulness (the 3-d class of danger).

Animals↗
PubMed1990

[Substantiation of the mean working day maximum allowable concentrations of dusts with differing degrees of fibrogenesis].

On the basis of developed by the author mathematical models of pneumoconiosis morbidity and of methodological techniques of dusts dividing according to the degree of fibrogenesis under exposure to various concentrations of dusts differing in fibrogenesis. In the author's opinion, working conditions can be considered safe if the probability of pneumoconiosis does not exceed 0.1% for the 40 years length of working. On this basis mean working day concentrations, at which the probability of the development of the mentioned disease does not exceed 0.1%, are proposed as mean working day MACs. Average working day MACs for the whole range of dusts fibrogenesis have been calculated. The obtained in this way average working day MACs for the least fibrogenic dusts equal 6 mg/m3, and for the most fibrogenic dusts - 0.2 mg/m3.

Air Pollutants, Occupational↗
PubMed1991

[Data for the establishment of maximum allowable concentration of chlorophenoxypinacoline in the working zone air].

Chlorophenoxypinacoline with its acute intragastric toxicity LD50 can be attributed to the 3rd class compounds of hazardousness (moderate hazardous substances). Local irritation and skin resorption effects were not revealed. Irritation of the mucous in the eyes in rabbits was moderate and functional cumulation was insignificant. Average lethal concentration (LC50) was not attained. The threshold of acute inhalation and irritation action (Limac, Limir) was at 1093 mg/m3, the threshold of chronic inhalation action (Limch) was at 165.2 mg/m3. No signs of specific mutagenic and embryotropic action were found. The accepted MAC for chlorophenoxypinacoline in the working zone air is 10 mg/m3. The aggregate condition aerosol, 3rd degree of hazardousness.

Air Pollutants, Occupational↗
PubMed1993

Impact of organochlorine pesticide residues and PCBs on otters (Lutra lutra): a study from western Britain.

A study of otter (Lutra lutra) populations and levels of organochlorine (OC) pesticide residues and PCBs in otter droppings (spraints) was made on eight stretches of river in three catchments in Wales and West Midland England. Population and contaminant levels were compared against target values. The otter populations (as measured by an index) remained stable on one stretch over 11 years, while they increased rapidly to equilibrium on four other stretches. The three lower stretches of rivers showed more erratic trends and on only one stretch did the index exceed, occasionally, the target value. Marking intensity at spraint sites was also lower at the three lowland sites. Concentrations of dieldrin, DDE and PCBs were significantly greater in spraint samples from the three lowland stretches. Over 50% of samples from the three lowland stretches had OC concentrations above the maximum allowable concentration, whereas most samples from the upland stretches had concentrations below the 'no effects level'. It is suggested that the colonization, by otters, of their former lowland range is inhibited by OC contamination of their food chain but, if contaminant levels can be reduced, spread will occur rapidly.

Animals↗
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↗
PubMed1991

[Effect of simultaneous exposure to fluorine and manganese on health status of workers].

The effect of fluorine and manganese on the health of workers continually exposed to these elements was studied. The concentration of the chemicals did not significantly exceed maximum allowable concentrations only during three hours of work daily. Thirty-six workers directly exposed to fluorine and manganese were examined and compared with the controls. The authors demonstrated that exceeding permissible norms did not cause evident intoxication symptoms even though working in exposure had lasted for many years. However, some changes in the activity of liver indicatory enzymes may be one of the first symptoms of this organ's damage. Frequently occurring ++periodontosis and leukoplakia of the mucous membrane needed careful stomatological prophylaxis .

Adult↗
PubMed1994

Volatile organic contaminants found in the habitable environment of the Space Shuttle: STS-26 to STS-55.

The health and performance of spacecraft crews can be adversely affected by contaminants present in the respirable air. Contaminants originate from hardware offgassing, crew and microbial metabolism, use of utility chemicals, leakage from fluid systems and payload experiments, and from electrical overheating. The quality of Shuttle air is measured by collecting contaminants in evacuated cylinders or on sorbent resin for later ground-based analysis by gas chromatography (GC) and GC mass spectrometry (MS). The results of those analyses are presented for 28 missions, including 5 Spacelabs which were flown in the payload bay of the Shuttle. The major contaminants were relatively nontoxic alcohols (ethanol, isopropanol), ketones (acetone, diacetone alcohol), alkanes, halocarbons (Halon 1301, Freon 113), and siloxanes. Occasionally, more toxic contaminants, such as methanol, acetaldehyde, and tetrachloroethene, were present at low concentrations (below 1 mg/m3). The contaminant concentrations measured in spacecraft air were compared to spacecraft maximum allowable concentrations (SMAC's) which are set to protect the crew from adverse health effects or performance decrements. Aggregate toxicity assessments (T values) of the contaminants present during each mission, calculated by summing the ratios of measured concentrations to each contaminant's SMAC, showed that air quality consistent met the criterion that the T value be less than 1.

Air Pollution, Indoor↗