FIG. 1.

Inactivation of Cryptosporidium spp. by UV light. Infectivity of C. hominis oocysts was measured in HCT-8 cells with detection by RT-PCR (MP UV, TU502 isolate, •) and in MDBK cells with immunofluorescence detection of infection (LP UV, TU502, ⧫; TU71, +). Infectivity of the C. parvum MD isolate was measured by HCT-8 cell culture/RT-PCR (MP UV, ○) and MDBK/immunofluorescence (LP UV, ◊). The solid diagonal lines represent the 90% prediction limits for UV inactivation of the Iowa isolate (n = 29) assessed in HCT-8 cells followed by RT-PCR (14). Disinfection credits provided to water treatment plants by the draft long term 2 enhanced surface water treatment rule are represented by the dashed line (20).