[Methods in the assessment of combined effect of substances].

Russian and foreign approaches to estimating the combined effect of substances are considered depending on the problems to be solved Data are given on the relationship of the type of combined effect to the mechanism of the toxic action of components and acting doses (concentrations). Various mathematical models for calculating the combined efect of mixtures are discussed There is evidence that it is necessary to study the combined effects of the mixtures of constant composition, which are used in water supply upon chronic exposure of the substances that are constituents of the mixtures. Based on their studies and the data available in the literature, the authors inferred that the nature of the combined effect of such mixtures should be investigated under the conditions suiting those of application, as well as when used at low concentrations.

[Dependence of carcinogenic properties of benzene derivatives on structure of their substituents adjusted for biotransformation].

An oxenoid model of the effect of cytochrome P450 and quantum chemical calculations were used to study a relationship of the carcinogenic activity of the benzene derivatives C6H5-X and C6H4-XY to the nature of the substituents X and Y For mono- and disubstituted benzenes, the methods based on the neglect of diatomic differential overlap was used to calculate the minimal values of AE for this compound, which is the minimum difference in the complete energies of the arenoxide intermediate OC6-H5-X or OC6H4-XY with one tetraedrically coordinated carbon atom in the benzene ring in reference to the initiar molecule of substituted benzene. The boundary value of the parameter deltaE min' which separated cancerogenic compounds from noncancerogenous ones was determined. A classification for nitrosubstituted benzenes was clarified using the parameter characterizing bioactivation via nitro group reduction to form phenylhydroxylamines and then nitrenic ions.

[Classification of substances to predict the order of magnitude of their safe water levels in terms of carcinogenic effect].

A classification has been developed to predict the safe water levels of chemical compounds in terms of their carcinogenic effect, by using as the base the LTD@10 value that is a lower 95% confidence limits for the lowest dose that statistically significantly causes a 10% increase in the incidence of cancer in laboratory animals continuously receiving a daily dose of the compound throughout their life, which is given in the CPDB internet resource, and the carcinogenicity classification adopted by the International Agency or Research on Cancer Based on an analysis ofthe maximum allowable concentration (MAC) of the standardized water substances in terms of their carcinogenic effect, the authors determined MA4 C ranges corresponding to different classes in accordance with the proposed classification. They predicted the orders of magnitude of MAC of the standardized water substances without taking into account their carcinogenic effect and those of four substances unstandardized in Russia.

[Experimental study of proflavine acetate phototransformation processes].

Changes in proflavine acetate phototransformation processes upon exposure to visible-range irradiation were studied by high performance liquid chromatography. Proflavine acetate was offered as a photosensitizer during photodynamic water disinfection. Dye transformation products upon time-varying exposure to irradiation were identified.

[General and specific aspects of the toxic properties of nanoparticles and other chemical substances in the context of classical toxicology].

The properties of nanoparticles versus chemical compounds in other physical forms were evaluated in the context of classical toxicology. A relationship of the toxicity of nanomaterials to the structure of molecules and the size of nanoparticles is discussed. Summing up the data available in the literature leads to the conclusion that there are general and specific aspects in the study of the toxicity of nanoparticles and chemical substances in other physical forms.