RELATIVE EFFICACY OF UV WAVELENGTHS FOR THE INACTIVATION OF CRYPTOSPORIDIUM PARVUM

CRYPTOSPORIDIUM PARVUM oocysts were exposed to narrow bands of radiation across the germicidal UV wavelength range. The dose of UV radiation transmitted though each narrow bandpass filter was measured utilizing potassium ferrioxalate actinometry. Infectivity of the oocysts was determined utilizing a cell culture assay and MPN quantification method. The log10 inactivation for each band of radiation was determined for a dose of 2 mJ/cm2. Doses from all wavelengths within the 250 to 275 nm range resulted in approximately 2-log10 inactivation of CRYPTOSPORIDIUM PARVUM. Doses from the higher and lower wavelengths resulted in lower log10 inactivation. The results suggest that between wavelengths of 250 and 275 nm, UV radiation is equally germicidal. Therefore, polychromatic radiation emitted from UV sources such as medium pressure lamps may not have any appreciable advantage over monochromatic radiation at 254 nm emitted from low-pressure UV lamps for inactivation of CRYPTOSPORIDIUM PARVUM.