5. Bioindicators of Toxic Metals

Growing social concern about environmental quality has been observed in recent years, on global and local scales. As the world’s population continues to grow, it becomes imperative to understand the dynamic interactions between human activities and the environment. With the growth of all aspects of the activities of modern man, warning signs appeared that the sources of the basic environmental components, air, water, and land are not unlimited. The advent of an increasing number of contaminants reduces the power of self-purification of these media, and degradation of nature and biosphere continues infinitely, consequently acting on the man.

Toxic heavy metals in air, soil, and water are global problems that are a growing threat to the environment. There are hundreds of sources of heavy metals pollution. Metals in the environment arise from natural sources directly or indirectly from human activities such as rapid industrialization, urbanization, and other anthropogenic sources. They are potential hazards to aquatic, animal, and human life because of their toxicity and bioaccumulative and nonbiodegradable nature. Non essential metals such as Hg, Cd, Cr, Pb, and As are toxic in their chemically combined forms as well as the elemental form. The major impacts of pollution can be stated as health problems with exposed human populations and ecosystems contamination. Those problems have been a cause of increasing public concern throughout the world.

During the last two decades the interest in using bioindicators as monitoring tools to assess environmental pollution by toxic metals has steadily increased. Bioindicators are flora and fauna members or groups of them which are used indirectly to measure the levels of metal contaminants in their environment, systematically collected and analyzed to identify potential health hazards to biota and humans. In practice, microbial systems, fungi, animal and plants are used as bioindicators to formulate conclusions regarding the environmental conditions. Similarly, different kind of living organisms, plants and animals, and even humans, can be used as bioindicators for environmental pollution by toxic metals because of their ability to absorb them from air, water, sediment, soil, and food chain.

Problems concerning toxic metals are very wide and encompass all parts of the nature. In this review the recent studies of organisms used as a toxic metals bioindicators in air, water, and soil ecosystems are presented. Also, the related toxicity, storage or defense mechanisms of living organisms and ecological effects of heavy metals pollution will be considered.