Mirex aquatic organisms

Mirex has been detected in air, surface water, soil and sediment, aquatic organisms, and foodstuffs. Historically, mirex was released to the environment primarily during its production or formulation for use as a fire retardant and as a pesticide. There are no known natural sources of mirex and production of the compound was terminated in 1976. Currently, hazardous waste disposal sites and contaminated sediment sinks in Lake Ontario are the major sources for mirex releases to the environment (Brower and Ramkrishnadas 1982 Comba et al. 1993). 

Biomagnification of mirex is supported by a study of various aquatic organisms that comprise an aquatic food chain in Lake Ontario (Oliver and Niimi 1988). The following concentrations (istandard deviation) of mirex were found ... 

Mirex is highly toxic to a number of aquatic organisms with crustaceans including commercially important species of shrimps and crabs being particularly sensitive. 

Biocidal properties of mirex to aquatic organisms, birds, and mammals are listed below. 

Aquatic organisms are comparatively resistant to mirex in short-term toxicity tests. Among various species of freshwater biota, LC50 (96 h) values were not obtained at the highest nominal concentrations tested of 1000.0 p,g/L... 

A variety of adverse sublethal effects of mirex to aquatic organisms, birds, and mammals are documented, including effects on growth, reproduction, embryonic development, behavior, and metabolism. 

Application of radiolabeled mirex to plants grown in a terrestrial/aquatic laboratory model ecosystem indicated that when the plant leaves were eaten by caterpillars, the aquatic system became contaminated. Mirex was detected in all segments of two aquatic food chains (alga > snail and plankton > daphnia > mosquito > fish) within 33 days. Undegraded mirex contributed to over 98.6, 99.4, 99.6, and 97.9% of the radiolabel in fish, snails, mosquitoes, and algae, respectively. No metabolites of mirex were found in any of the organisms (Francis and Metcalf 1984 Metcalf et al. 1973). 

Typical enrichment of organic chemicals in the aquatic food chain of Lake Ontario has been observed for DDT and PCBs, which exhibit concentrations up to 8 ug/g and 17 tg/g, respectively, in fish on a lower concentration level - mainly due to the higher solubility of these compounds - similar effects can be seen for mirex and lindane (Table 2-8). Chlorobenzenes, in relation to sediment data, do not exhibit food chain enrichment, except for hexachlorobenzene, which is significantly concentrated in planktonic and benthic organisms. However, there is a distinct accumulation of all chlorobenzene isomers by organisms from the water phase, and it has been Stressed by Oliver Nicol (1982) as a typical feature that Lake Ontario fish contains much higher concentrations of CB s than fish from the other Great Lakes. 

Mirex is rapidly adsorbed onto various organic particles in the water column, including algae, and eventually is removed to the sediments. Not surprisingly, mirex has a long half-life in terrestrial and aquatic sediments large fractional residues were detected at... 

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