Cadmium is the silver-white metal used to manufacture rechargeable batteries, produce alloys with other metals and electroplate chrome on auto parts and appliances. It has been mined in the Colorado Rockies for more than a century. Cadmium finds its way into the environment when rainwater washes through the piles of ore tailings at abandoned mine sites.
Most trees and other plants readily take up cadmium from the soil, but willows in particular act as biological pumps to biomagnify, or concentrate, the toxic metal in willow leaves and leaf buds to as much as 100 times the levels found in soil. Those same levels of cadmium were found by the researchers in the crop contents of birds that ate willows.
Once ingested, cadmium can become concentrated in kidney tissue. All the adult birds tested in the central and southwestern mountains of Colorado had elevated kidney-cadmium levels. Toxic levels of cadmium were documented in 44 percent of adult birds, whereas birds living outside the ore belt region of Colorado had near-normal cadmium levels in their bodies. High concentrations of cadmium damage kidney tissue and reduce the birds' ability to process calcium. Among adult birds tested in Colorado, 57 percent had damaged kidneys.
To make matters worse, the mining areas that are rich in cadmium also tend to be calcium poor -- in part because of the high acidity of the water and soils --- so birds have little chance of accumulating the mineral they need for strong bones and robust eggshells. According to Larison, birds with insufficient cal
Contact: Roger Segelken
Cornell University News Service