Reviews of Environmental Contamination and Toxicology Volume 211

Marine pollution refers to direct or indirect contamination of the marine environment (including estuaries) by humans. Such marine pollution may result from substances or from energy and may produce harm to living organisms, hazards to human health, hindrances to marine activities such as fishing, impairment of seawater quality, and reduction of amenities. Contaminants are transported from land to sea by streams and rivers, direct runoff, or point discharges. Contaminants are partly retained in the water and in the sediments of estuaries, bays, beaches, or open coastal waters and are partly transported through these boundary areas to the open ocean. Moreover, coastal waters are not only more polluted than is the open ocean but also offer a significantly higher probability of exposure to the world’s most important fisheries and recreational areas (Magos 1990).

Complex factors have contributed to the decline of aquatic populations worldwide. Among these factors are intensification of agriculture, including the application of fertilizers and agents of crop protection, and loss of habitat. Various developmental abnormalities in natural populations of aquatic vertebrates have been documented, and agricultural pesticides are considered by many to be one of the important factors that cause such abnormalities. Amphibians may potentially be a target of environmental stressors and toxicants as a result of their biphasic life cycles and skin permeability. In this chapter, the role of oxidative stress in the teratogenic action of pesticides is reviewed and addressed, with special attention given to non-target aquatic organisms such as amphibians, fish, and invertebrates. The review of available literature indicates that many pesticides enhance oxidative stress in aquatic organisms, and such stress may be linked to developmental alterations, including reproductive effects, embryotoxicity, and/or teratogenicity.

The presence of unwanted substances in the environment becomes “pollution” when damage or deleterious effects caused by those substances are detected. Pollution is essentially a process by which a natural or a man-made resource becomes unfit for beneficial use (Enger and Smith 2006). Many man-made substances, in addition to certain naturally occurring organic and inorganic compounds, different forms of energy (e.g., heat, light and noise), and other things, add to the diversity of pollutants. Pollutants, which can occur at the local or the global level, render varying influences on soil and water that depend on the nature and spreading rate of the pollutants themselves, and produce short- or long-term effects on elements of an ecosystem. Undesirable changes in air, water, and soil may induce diverse responses from living organisms that are similar to those induced by the presence of pollutants. The effects on organisms caused by pollutants may range from innocuous to toxic. Toxicity, which has been defined as an inherent property of a substance to cause an adverse biological effect, is the result of a chemical disturbance that affects complex and interrelated systems involving cells, tissues, organs, or metabolic processes (ECETOC 1985).

Fluorine is widely dispersed in nature and is estimated to be the 13th most abundant element on our planet (Mason and Moore 1982). It is the most electronegative of all chemical elements, and as a result, it never exists in elemental form, but rather combines with other elements; fluoride compounds represent about 0.06–0.09% of the content of the earth’s crust (Wedephol 1974). Fluoride is distributed universally throughout soils, plants, and animals, and is assumed to be an essential element in animals, including humans. Fluoride has an important role in bone mineralization and formation of dental enamels. Fluoride, when consumed in inadequate quantities (less than 0.5 ppm), causes health problems such as dental caries, lack of formation of dental enamel, and reduced bone mineralization, especially among children (WHO 1996). In contrast, when fluoride is consumed in excess (more than 1 ppm), health problems may result, which equally affect the young and old (WHO 1996). At higher fluoride concentrations, metabolic processes are affected in humans, and overexposed individuals may suffer from skeletal or dental fluorosis, non-skeletal manifestations, or combinations of these maladies (Susheela et al. 1993). The incidence and severity of fluorosis depends upon the fluoride concentration in air, soil or water, and the degree of exposure to these levels.