control water never changed color. This color change
was presumed to be related to degradation from tetracycline
exposure to light; however, a study by Wu and
Fassihi (2005) suggested that increased temperatures
and increased humidity cause degradation of tetracycline
and not light exposure. The HPLC assay continued
to detect the tetracycline present in the water even
after the color change began. Follow-up studies are being
performed to better characterize the antimicrobial effects of this color change, but the widely held assumption
that tetracycline is deactivated by light appears
incorrect.