Table 2.

Irradiance calculation factors for Escheria coli, MS2, and Cryptosporidium parvum

Organism Type and Identification	UV254 * Absorbance/1 cm	Petri Factor
E. coli 1	0.204	0.991
E. coli 2	0.305	0.981
E. coli 3	0.180	0.997
E. coli 4	0.316	0.975
MS2 1	0.012	0.991
MS2 2	0.026	0.981
MS2 3	0.215	0.971
MS2 4	0.212	0.975
C. parvum Iowa	0.091	0.976
C. parvum Moredun	0.175	0.971
C. parvum TAMU†	0.386	0.981
C. parvum Maine	0.211	0.991
C. parvum Glasgow	0.154	0.982

^*UV₂₅₄—ultraviolet light at 254 nm

^†TAMU—Texas A&M University