Mirex birds

Mitex [2385-85-5] is l,2,3,4,5,5,6,7,8,9,10,10-dodecachloro-octahydro-l,3,4-metheno-2JT-cyclobuta-p,<7 -pentalene (37) (mp 485°C). The rat LD s are 306, 600 (oral) and >2000 (dermal) mg/kg. Mirex is extremely resistant to biodegradation and was once considered the perfect stomach poison iasecticide for use ia baits to control imported fire ants. However, even at doses of a few milligrams per 10 m it was found to bioaccumulate ia birds and fish and its registrations were canceled ia the United States ia 1976. 

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

Acute oral toxicity of mirex to warm-blooded organisms was low, except for rats and mice, which died 60 to 90 days after treatment with 6 to 10 mg mirex/kg body weight (Table 21.1). Birds were comparatively resistant. The red-winged blackbird (Agelaius phoeniceus) was unaffected at 100 mg mirex/kg body weight, although it was considered the most sensitive of 68 species of birds tested with 998 chemicals for acute oral toxicity, repellency, and hazard potential (Schafer et al. 1983). 

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

Baker, M.F. 1964. Studies on possible effects of mirex bait on the bobwhite quail and birds. Proc. Annu. Conf. Southeast. Assoc. Fish Game Comm. 18 153-159. 

Bird, D.M., P.H. Tucker, G.A. Fox, and PC. Lague. 1983. Synergistic effects of Aroclor 1254 and mirex on the semen characteristics of American kestrels. Arch. Environ. Contam. Toxicol. 12 633-640. 

Limited data are available on mirex worldwide except in the United States. The levels of mirex found in birds that were collected in the United States, except of those from the southeastern United States and the Great Lakes, were low and were considered nonhazardous in the 1970s (Cain Bunck, 1983). White (1979) investigated the wings of mallards and American black ducks (Anas rubripes) that were collected from four major flight pathways between 1976 and 1977 (Eisler, 1985 and the references therein). The results showed that Atlantic mallards had the highest detection frequencies of occurrence at 50% and the highest concentration of mirex (0.14 pg g-1 wet wt.). They were followed by Mississippi mallards at 29% and 0.03 pg g-1 wet wt., Central mallards at 14% and 0.06 pg g-1 wet wt., and Pacific mallards at 4% and 0.03 pg g-1 wet wt. (Eisler, 1985). 

Few studies were available to evaluate the temporal change of mirex in bird samples. The only studies of mirex in seabird eggs were conducted by Braune et al. (2001) on the temporal trends from 1975 to 1998 in the Canadian Arctic. A decreased trend of mirex levels was only observed in eggs of black-legged kittiwakes but not in northern fulmars and thickbilled murres. The levels of mirex that were measured in the eggs of the studied animals ranged from 0.003 to 0.013 pg g-1 wet wt. in 1998. There did not appear to be any consistent change in the proportions over the study period (Braune et al., 2001). No information is available on the level of mirex in waterbirds in China. 

Bird et al. (1983) found that when captive American kestrels Falco sparverius) were fed 8 mg kg-1 of mirex for 69 days, there was a decline in sperm concentration and a slight increase in semen volume. An overall net decrease of 70% in sperm number was observed. The investigators... 

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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