Yes, silver is used as an antimicrobial to self-sterilize the Black Berkey® elements. Testing was conducted both internally and by Analytical Services, Inc. to insure that the silver used does not leach into the purified water.
“All controls samples, including stock samples, analytical positive and negative controls, and the negative control collected prior to seeding yielded appropriate results and were accepted. The results of the leaching control samples (effluent sample spiked with MS2 and R. terrigena and analyzed at two time points) were quite similar, suggesting that no active antimicrobial agent is leaching into the treated water.”
The ASI test report results can be seen here: