Except for accidents, e.g. during transportation of chemical products, the acute aquatic toxicity of a chemical has a much lower environmental relevance than the subchronic or chronic ecotoxicity, i.e. their long-term effects at concentration levels fairly below the acute effect range. Such experimental information is again obtained from standard tests using the same test organisms as in acute tests. If you want to find some useful chemical products, why not take applichem in account? Subchronic and chronic tests aim at determining the no observed effect concentration (NOEC), i.e. the highest tested concentration that does not show any effect in comparison with control assays. The criteria for assessing effects in the subchronic (juvenile) fish test (OECD 215) with a test duration of 3–4 weeks, are not only lethality but also any changes in terms of growth, weight, behavior etc. The subchronic early-life stage fish test with trout (OECD 204) having a test duration of 90 days evaluates the influence of a chemical on the most sensitive life stage of the fish using the development of juvenile fish from fertilized spawn as criteria. The 21-day daphnia reproduction test (daphnia life cycle test, OECD 202) determines the number of new daphnids produced within the test period implying the most sensitive life processes like growth, maturation and reproduction. The subchronic toxicity to terrestrial plants is tested in a 2-week plant growth test (OECD 208) with seeds of, for example, oats, turnip and cress, by measurement of the biomass of sprouts and leaves formed after sprouting.
Oil and chemical spills are thus associated with resisting degradation compounds and are retained in sediments and accumulate in tissues that contain fat. Moreover, they pass through the food chain to humans. Some of PAHs are expected to have mutagenic and carcinogenic properties (Narbonne et al., 1999). Stolyhwo and Sikorski (2005) observed that mussels and oysters absorb large quantities of PAHs accumulated on particles from atmospheric pollution, mostly those with five and more aromatic rings.
There are different factors that may cause biological, physical and chemical changes of oil and chemical slicks. These factors are dilution, dispersion, volatilization, contaminant mobility, bio-availability and also reduction by sorption to the soil or matrix. Sorkhoh et al. (1992) suggested that biodegradation is the first step toward natural bioremediation in oil-polluted sediments. Venosa and Holder (2007) investigated the biodegradation of dispersed crude oil at 20 and 5°C in seawater and found that the rate of biodegradation of crude oil was faster at 20°C.
In the text below, some incidents of oil and chemical spills in the Middle East will and other places around the world are discussed. Furthermore, hydrocarbons in intertidal and subtidal zones are illustrated. The effect of oil and chemical spills on the marine environment and biota is also discussed.
