Biomedical subjects

Z Bardodĕj

Publications and source records attributed to Z Bardodĕj.

13 recordsLinked to original sources

PubMed1991

Exposure limits for occupational and environmental chemical pollutants in various media.

Exposure limits for occupational and environmental chemical contaminants are based on animal experimentation and observation in humans. Usually, the final recommendations are "predictions" which can hardly guarantee the absolute safety for all. Late effects were discovered to lately in the past. The impact of the biotransformation of pollutants on their biological activity is demonstrated with trichloroethylene, styrene and N,N-dimethylformamide, which are suspected of having carcinogenic potential. In addition, trichloroethylene and N,N-dimethylformamide cause intolerance of alcohol with hyperacetaldehydemia; acetaldehyde is claimed to be carcinogenic as well. The biotransformation of these three widely used substances differs among various species. Different fate of chemicals in human and animal organisms results in the necessity to consider kinetic and metabolic studies in setting limits; in microorganisms also metabolites supposed to be formed in humans should be tested. Limits for some pollutants in various media are given.

Animals↗

PubMed1988

Long-term study on workers occupationally exposed to ethylbenzene.

Ethylbenzene is synthesized from benzene; subject to catalytic dehydrogenation it yields styrene, a raw material for the production of synthetic rubber and plastics. Long-term biomonitoring of occupational ethylbenzene exposures, carried out in the past 20 years in some 200 ethylbenzene-production workers, revealed this substance to pose little hazard to human health. As it turned out, mandelic acid concentrations in these workers' urine never exceeded 3.25 mmol.l-1 and none of the exposed showed damage to hematopoiesis and/or liver tissue. Over the last 10 years no case of malignancy has been recorded in this industrial facility belonging to a larger chemical complex where the overall incidence of cancer is about 3 times the national average. Today's low-level ethylbenzene exposures would make it fully justifiable if the present-day MAC limits, both whole-shift (200 mg.m-3) and peak (1,000 mg.m-3), were to be halved, i.e. to be lowered to 100 mg.m3 and 500 mg.m3 respectively. These newly recommended limit values are no more exceeded nowadays.

Air Pollutants, Occupational↗

PubMed1985

Mercapturates in the urine of persons exposed to N,N-dimethylformamide.

N,N-dimethylformamide, a nucleophilic aprotic dipolar solvent, has multipurpose uses, especially in the manufacture of plastics. Its acute toxicity for mammals is low; it is hepatotoxic. Vapors are absorbed by the lungs, in the liquid form it causes cutaneous maceration and is rapidly absorbed through the skin. In the organism it is primarily metabolized to N-monomethylformamide, to a lesser extent to formamide. Urine of individuals exposed to N,N-dimethylformamide was newly found to have higher levels of thioethers, most likely mercapturates, as yet of unknown chemical structure. The correlation between the urinary concentrations of mercapturates (y) and N-monomethylformamide (x) can be expressed by equation y = 4.93 + 0.58 x, with the coefficient of correlation r = 0.90. Part of N,N-dimethylformamide metabolites is likely to react with biopolymers, part of it is excreted as metabolic end products, i.e. carbon dioxide, water and urea. Breakdown to mercapturates may implicate N,N-dimethylformamide as being a potential carcinogen.

Acetylcysteine↗

PubMed1984

The measurement of mercury excretion in urine.

The determination of mercury in urine using cold atomic absorption spectrometry according to Gage and Warren is used after slight modification as standard method for the exposure test in persons exposed to its vapours in industry in Czechoslovakia. Within the concentration range between 100 and 600 nmol X l-1 of urine the relative standard deviation was lower than 4%. In workers exposed to mercury in the production of thermometers, fluctuation of urinary mercury concentration due to variations in diuresis could be greatly reduced by adjustment for endogenous creatinine. After the intake of 2.2 or 2.5 l of liquids the concentration of mercury in urine dropped considerably, but returned again to its initial value within 4 hours after fluid intake. The mercury half-life in the organism is estimated at about 30 days, but may be longer at mercury concentrations of 1 mumol X l-1. Contradictory to the original expectation, the Araki's coefficient b that is recommended for suppressing the effect of the volume of excreted urine on the concentration of urinary substances was found to be concentration-dependent: at 500 nmol X l-1 its value shifted towards 1 (0.85), at 100 nmol X l-1 towards zero (0.2-0.3). It is believed that mercury urinalysis data adjusted for endogenous creatinine are sufficiently reliable to be used for assessing the risk of human exposure to mercury.

Air Pollutants, Occupational↗

PubMed1983

Urinary excretion of mercapturates as a biological indicator of exposure to electrophilic agents.

The urinary excretion of mercapturates was followed photometrically in individuals exposed to styrene, a mixture of aromatic hydrocarbons, butadiene, vinyl chloride, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethylene, 1,1,1-trifluoro-2-bromo-2-chloroethane (Halothane), ethylene oxide, epichlorhydrin, bis(chloromethyl)-ether, N-methylacrylamide, dimethylformamide, nitrosamines or cis-platinum and in groups of controls, smokers and nonsmokers, males and females, the residents of city P, industrial town V.M. and mountain village S. The increase in the urinary excretion of mercapturates was found in individuals exposed to styrene, aromatic hydrocarbons, dimethylformamide, 1,1,1-trichloroethane, and in smokers. In groups of controls, the lowest mercapturate concentrations were detected in the urine samples of nonsmokers from the mountain village S. where the degree of air pollution due to motor vehicle emissions was lowest at the time of investigation.

Air Pollutants↗

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↗

PubMed1976

Metabolic studies and the evaluation of genetic risk from the viewpoint of industrial toxicology.

In recent years some important industrial chemicals, e.g. solvents, and monomers used in the production of plastics, have been found to be more dangerous than had been suspected. Some of them are mutagens and carcinogens. The active substance may be the compound itself, but more frequently it is a reactive intermediate, an alkylating agent, formed from the parent compound by oxidation under the influence of liver-microsome mixed-function oxidases. Trichloroethylene, vinyl chloride, 1,1-dichloroethylene and 2-chloro-1,3-butadiene can be mentioned as examples, where mutagenic or carcinogenic activity has been demonstrated; similar activity of some others is to be suspected. Metabolic studies may explain unexpected effects or they may allow one to predict such effects. Tests on microorganisms with a metabolic activation in vitro seem to be extremely valuable for fast and efficient screening of man-made chemicals to be introduced into the environment, because such tests combine the use of liver microsomes and bacteria for detection and classification of the effect. Mutagenicity tests in mammals do not lose their usefulness, since thay take into account the distribution of the compound in the body, its transport to the target organ, species-specific differences etc. As exposures of workers to chemicals mentioned above have been quantitatively measured regularly, epidemiological studies should be performed with regard to mutagenic and carcinogenic effects in relation to the degree of exposure. Here is a chance for better understanding of how to extrapolate experimental results to human populations and how to establish safe levels of chemicals in the environment if at all possible and acceptable.

Alkenes↗

PubMed1975