The relation between the toxic action of chemicals on individual organisms and the performance of a population of these organisms is one of the central themes of ecotoxicology. To understand the environmental consequences of chemical pollution, the mechanisms that exist within a population to compensate or to magnify toxic effects on the members of that population must be known. How the populations respond depends on the priorities of the organism subject to toxicant stress. These priorities in a species-specific life history can be reproduction or growth and survival, which may be influenced in many different ways by toxicants exposure. In this sense, many studies in the field have reported effects of POPs directly related to survival of individuals and population level such as embryo lethality and developmental deformities.
The adverse effects of POPs on the organisms have been studied in two primary ways. First, by laboratory and controlled exposures of organisms to single congeners, mixtures, or matrice extracts; and second, by correlation of substance concentrations in the environment with abnormalities in birds, fish, and marine mammal populations, such as mortality during early development stages and modifications induced on the adrenal cortex in marine mammals. These two strategies have different application fields. Field research can integrate the knowledge of the impact of multiple environmental contamination on exposed organisms. Laboratory exposures, with both in vivo and in vitro studies, instead can identify the specific responses associated with exposure to a single toxicant, and determine the dose-response relationships for those
Table 1 Physicochemical properties of the most significant POPs
Molecular weight (Da)
Water solubility log Kow
Vapor pressure (mmHg) soil (years)
aData refer only to the seven toxic congeners. faData refer to TCDD.
cData refer only to the ten toxic congeners.
180 ng ml-1 3x10"4
0.0001-0.01 |ig l~1 /i o q oc 0.003-1.6 x 10"6 _
100 days to 12 years responses. Anyway, both field and laboratory research are vital to understand the toxicity of chemicals.
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