Mirex mammals

Acute oral toxicity of mirex to birds and mammals... 

Table 21.1 Acute Oral Toxicity of Mirex to Birds and Mammals...

Mirex has considerable potential for chronic toxicity because it is only partly metabolized, is eliminated very slowly, and is accumulated in the fat, liver, and brain. The most common effects observed in small laboratory mammals fed mirex included weight loss, enlarged livers, altered liver enzyme metabolism, and reproductive failure. Mirex reportedly crossed placental membranes and accumulated in fetal tissues. Among the progeny of mirex-treated mammals, developmental abnormalities included cataracts, heart defects, scoliosis, and cleft palates (NAS 1978 Blus 1995). 

Hill, E.P. and D.M. Dent. 1985. Mirex residues in seven groups of aquatic and terrestrial mammals. Arch. Environ. Contam. Toxicol. 14 7-12. 

Mirex was also detected in the muscle and liver tissues of seven species of aquatic and terrestrial mammals collected in areas of Alabama and Georgia that had been repeatedly treated with mirex to suppress fire ant populations from March 1973 through July 1976. At 6 months post-treatment, skunk and opossum muscle tissue contained the highest mean mirex concentrations of 3.50 and 1.51 pg/g (ppm), respectively (Hill and Dent 1985). Two years post-treatment, muscle residues declined in all species except the mink, which increased from 0.14 pg/g at 6 months post- treatment to a mean muscle residue of 0.28 pg/g at 1 year post-treatment and 0.53 pg/g at 2 years post-treatment. 

Environmental. The high lipophilicity of the cydodienes and the prolonged persistence of dieldrin and heptachlor epoxide (soil half-lives 2—10 yr) have resulted in severe environmental contamination. These compounds are bioaccumulated from water to fish up to 100,000- to 300,000-fold and are ubiquitous in human fat and milk. Oxychlordane [26880-48-8], mirex, and chlordecone are also bioaccumulative. The cydodienes are extremely toxic to fish with LC5Qs (ppm) to trout and bluegill of endrin, 0.001-0.002 endosulfan, 0.001-0.003 diddrin, 0.003-0.015 aldrin, 0.006-0.01 heptachlor, 0.03-0.026 and chlordane, 0.022—0.095. The LD5Qs to pheasant and mallard are aldrin 16.8 and 520, dieldrin 79 and 381, and endrin 1.6 and 5.6 mg/kg. As indicated by their rat oral LD - s, they are also extremdy toxic to small mammals in fact, endrin has been used as a rodenticide (see Pesticides). Compounds, eg, aldrin and heptachlor, which have unsubstituted double bonds, readily add oxygen to form epoxides in plant and animal tissues and are preferentially concentrated and stored in animal fats. Aldrin epoxide (dieldrin) and heptachlor epoxide are more stable (half-lives on alfalfa of seven to eight days) than aldrin and heptachlor (half-lives on alfalfa of less than one day). 

Levels of POPs in two local marine mammals, the Indo-Pacific humpback dolphin (Sousa chinensis) and Unless porpoise (Neophocaena phocaenoides), were measured in two ad hoc studies of stranded cetaceans in 1995-2000 and 2000-2001, respectively (Jefferson et al., 2002 Imanishi et al., 2004). Cetacean tissue samples were collected from stranded animals found in Hong Kong and analyzed for DDT, mirex, toxaphene and PCBs. High mean blubber concentrations of DDT (32.8 mg kg-1 ww) and PCBs (8.19 mg kg-1 ww) were reported. 

The polychlorinated cage compounds mirex and chlordecone were very poor inhibitors of GABA-dependent chloride uptake, producing little or no. .inhibition at 100 yM (j ). These compounds also failed to inhibit s]TBPS binding at concentrations up to 10 yM (4). Thus, despite the potent inhibition of [3H]DHPTX binding in cockroach CNS preparation by chlordecone (3), it appears that these compounds act at sites other than the GABA receptor-ionophore complex in mammals. 

Possibly the greatest attention, however, traditionally has been directed to the concentration of organic compounds from the aqueous phase into biota. This effort has been motivated by the consistent recovery of many compounds of industrial interest such as PCBs and the more persistent agrochemicals such as DDT (and its metabolite DDE), mirex, and aldrin from samples of fish, birds, and marine mammals such as seals, whales, and polar bears. In a few cases, a plausible correlation has been established between injury to biota and exposure to a toxicant, and this is discussed in a wider perspective in Chapter 7, Section 7.7.2. Only two examples of such correlations will therefore be given here as illustration ... 

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

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. 

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