The mutagenicity of bleached pulp mill effluents was compared to the mutagenicity of unbleached waste waters. Mutagenicity was assessed with the Ames test, using metabolic activation systems isolated from the liver of rats and fish. Liver extracts from fish caught in polluted areas, and from fish experimentally exposed to waste water, were also investigated. Pulp mill effluents taken after chlorination showed mutagenic activity. The activity diminished during the waste water treatment. Tissue extracts from fish exposed to various concentrations of treated bleached and unbleached pulp mill effluents showed only slight mutagenic activity in a few samples. In the case of bleached pulp mill effluents monooxygenase activities were elevated in those samples where slight mutagenicity was observed. In the case of unbleached effluents no such correlation was found.

The quality and biological effects of the waste waters released by Baikalsk Pulp and Paper Mill were monitored chemically and biologically. In 1:5 dilution, the treated waste water induced monooxygenase activity in the liver of grayling and bullhead in standardised laboratory conditions. The Ames test was used to monitor mutagenicity of waste waters of the mill and tissue extracts of fish, sponge, mollusc and plankton collected near the mill and of seals collected from the middle part of the lake. Mutagens were found in waste water produced during pulp chlorination before treatment and in a few samples of fully treated waste water during 10 years (1982–1993). Bottom sediments near the mill showed some mutagenicity. Mutagens were not found in tissues of most aquatic animals studied with the exception of zooplankton, roach and seals collected in Lake Baikal close to the discharge outlet of the mill.

Use of various high molecular weight synthetic compounds as flocculants allows considerably increase the efficiency of physical-chemical methods for industrial wastewater treatment. Doing this, potential severe effects of residual amounts of these compounds on water organisms are not taken into consideration. Ecological-toxicological assessment of six flocculants: Magnafloc E1O, Zetag 64 (Germany); Sanfloc N520P, Sanfloc CH009P (Japan); Catfloc (U.S.A.); Polyacrylamide-PAA (Russia) was done in the course of our study. Flocculant toxic effects on water organisms of various systematic groups were found using international biotesting parameters. The flocculants affected all water ecosystem components and, especially, protococcal algae, invertebrates and adult fish. Acute and long-term experimental results showed the necessity of establishing maximum vital concentrations of flocculants. Comparative biological activity studies for different types of flocculants (cationic, anionic and nonionic) showed that cationic ones had the most expressed acute and long-term toxicity. According to the whole complex of pathological effects flocculants seem to possess the membranotropic mode of action. The results indicate flocculants as a new micropollutant class with high toxicity for water organisms. The control of their residual amounts in effluents discharged into receiving waterbodies is needed.

The use of the Ames test for the analysis of industrial effluents from cellulose production and sewage waters varying in the degree of purification with the aid of a metabolic activation system from rat and fish liver with Salmonella strains TA 98 and TA 100 revealed a strong direct mutagenic effect of strain TA 100 in samples after cellulose chlorination. The multistage procedure of sewage water purification allows to remove practically completely the mutagenic substances. A simultaneous study of cytotoxic effects of industrial effluents on mammalian cells shows that the mutagenic activity is exhibited in not toxic concentrations. The urgency of a regular biological control over the genotoxicity of industrial effluents from the sulfate production of cellulose is under discussion.

Monooxygenase activity changes in the liver and in other tissues of certain fish species were studied after injection of methylcholanthrene and aminoanthracene to fish. Determinations of the benz(a)pyrene hydroxylase activity and activity of 7-ethoxycoumarine 0-dealkylation in the monooxygenase system were proposed as test-systems for the control of polycyclic hydrocarbon contents in natural and waste waters. The metabolic activation (Aim's test) performed by the liver microsomal fractions of different fish species was used for the analysis of sulfate cellulose industry waste waters.

The study of mutagenic effect of 2-aminoantracene and benz(alpha)pyrene on Salmonella triphimurium TA 100 in the Ames test-system in the presence of postmitochondrial fractions S-9 from carp liver with 3-methylcholantrene induced by microsomal oxidation system has been carried out. The metabolic activity and cytochrome P450 contence in carp liver microsomes have been shown to concede considerably those in rats liver. But these characteristics are sufficient for the use of fraction S-9 from carp liver for the study of genotoxic effect of these xenobiotics in the Ames test-system. Several regimes of storage of S-9 preparations from carp liver have been compared. S-9 preparations frozen immediately after isolation preserve their metabolic activity with respect to 2-aminoantracene and benz(alpha)pyrene well.

Using the Ames mutation test system II samples of the Baikal pulp and paper effluents selected at different dates have been investigated. In 9 cases the effluent samples possessed no mutagenic activity; some samples revealed frame shift mutations, i.e. a medium mutagenic effect. In the presence of a metabolic activation system from the livers of phenobarbital-induced rats the mutagenic activity was considerably reduced.