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A survey of the evidence obtained in recent decades for a wide range of pollutant effects on plants permits a distinction between four types of damage which differ in the character and intensity of metabolic disorders: acute, drop-like burns, cumulative and insidious (invisible, latent). It is impossible to clearly distinguish between the groups.

A great many works have been published in the last 15 years on the role of phytophagous insects in forests polluted with industrial emissions. Nevertheless, our knowledge of the conditions of development, adaptation and performance of phyllophagous and xylophagous insects (referred to as phyllophages and xylophages) in forests polluted with fluorine-containing emissions is limited. The role of insects in decline of such stands is sometimes undoubtedly overestimated, especially for coniferous forests, and should be distinguished from the capacity of needles to accumulate fluorine during the whole growing period and over many years. Trees can decline in vast areas without any contribution from insects.

The lower resistance of conifers to acid pollutants as compared to the resistance of deciduous trees is best illustrated by fluorine. Fluorine phytotoxicity is determined by the effect of burning and the toxic effects of fluorine accumulation in organs and tissues. The enhanced sensitivity of conifers to hydrogen fluoride is related to long needle life. Accumulation of hydrogen fluoride in the needles over many years results in extensive damage of the crown, reduction of the area of assimilation and finally plant death because of carbon starvation. Moreover, the high sensitivity of evergreen conifers arises from a relatively poor development of storage tissues and, consequently, insufficient accumulation of storage substances as well as a low regenerative capacity.

It has not been easy to accept the evident fact that our environment is more sensitive to industrial impact than are human beings and that this environment, with which man is constantly interacting, is a necessary requesite for existence. We have still not become aware of the importance of studying the impact of industrial pollution on ecosystems and the necessity to assess maximum permissible concentrations in the atmosphere of agents that are harmful to plants and plant communities. We also understimate the ability of protection zones around industrial plants to protect against local atmospheric pollution. Such zones are aimed not only at assuring safety to people but also at reducing the adverse impact of pollutants on local vegetation and animals.

The assumptions of the limits of acceptable atmospheric pollution proposed by Ryazanov in 1949 have formed the basis for development of public health standards of the content of toxic compounds in the air. MPCs of pollutants in the air for humans is defined as such a level which fails to directly or indirectly affect them. Two standards have been established in the USSR for each pollutant: a single MPC and a daily mean MPC. The single MPC is introduced to prevent reflex responses in humans exposed to a pollutant for a short time (5–20min) and the daily mean MPC to prevent a repeated absorption effect (toxic, carcinogenic, mutagenic, etc.) of a toxic compound without exact determination of the duration of its impact. Public health standards have been determined for more than 600 substances and for 33 complexes of air pollutants (Nikitin and Novikov 1986).

The effect of fluorine-containing emissions on vegetation have much in common with other acid pollutants. However, there are some specific aspects attributed to the ready distribution of this pollutant in the atmosphere, its high phytotoxicity and its prevailing cumulative effect on woody plants.

The present-day expansion of utilization of natural resources makes it necessary to coordinate the increase in industry with its effects on ecosystems. In connection with this, the principal tasks are, first, to heal the wounds suffered by nature by means of forest culture and natural reafforestation processes and, second, to enhance the ability of woody plants and forest communities to accumulate pollutants and detoxify the atmosphere (Kulagin 1980; Liebold and Ranft 1981). This can be done by selecting individual gasresistant trees, establishing plantations of gas-resistant clones and choosing relatively gas- and smoke-resistant ecological populations. The latter method is the most popular as it saves time and reduces the expense of producing plant material that is resistant to industrial pollution.