Toxin combo common in fish appears capable of impairing mo...( s or just MeHg or to both chemicals be...)

At birth, the pups of mothers exposed to methylmercury alone did not differ in weight from the control group. The birth weight of pups whose mothers had been exposed to just PCBs or both chemicals was slightly, but significantly, less than the control animals.

At weaning, the weight of pups exposed to PCBs was as much as 11 percent below that of control animals, while the pups in the PCB-MeHg exposure group weighed as much as 15 percent less than controls.

Two months later, one male and female pup from each litter were tested for the next four weeks on their abilities to navigate vertical ropes, parallel bars and various speeds of rotating rods. At the end, female pups whose mothers had been exposed to MeHg were slightly impaired on the rope-climbing test, while their male counterparts actually had less hind-limb slips on the parallel bars. Overall, the results of the MeHg-exposed pups were not significantly different than that of the control animals.

However, on the rotating rods the impact of exposure to both PCBs and methylmercury became clear. As the speed of the rods exceeded 25 rpm, the pups, regardless of sex, that were exposed to both toxicants during their mothers' pregnancies slipped significantly more often than their control counterparts. Exposure to either of the chemicals alone did not significantly impact performance.

However, Schantz said, the tests showed that PCB exposure contributed more than did the methylmercury to the pups' deficits, although the low dosage of MeHg used in the study (1.20 milligrams compared with the 2 to 18 mg used in previous studies of motor skills) may explain why.
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Contact: Jim Barlow, Life Sciences Editor
jebarlow@uiuc.edu
217-333-5802
University of Illinois at Urbana-Champaign
1-Mar-2004