Meinertz, J.R., G.R. Stehly, S.L. Greseth, and W.H. Gingerich. 2001. Depletion of para-
toluenesulfonamide from the edible fillet tissue of rainbow trout after exposure to 
chloramine-T. Final report submitted to the UMESC archives October 19, 2001 and 
submitted to the Center for Veterinary Medicine, U.S. Food and Drug Administration, 
October 19, 2001. 1539 pages.

Summary
Waterborne exposure to chloramine-T is an effective treatment for controlling fish 
mortalities caused by bacterial gill disease. Currently, data are being generated to gain 
U.S. Food and Drug Administration (FDA) approval for the use of chloramine-T in 
aquaculture. As part of the data required for an approval, depletion of the chloramine-T 
marker residue (para-toluenesulfonamide; p-TSA) from the edible fillet tissue of exposed 
fish must be determined. Rainbow trout (Oncorhynchus mykiss; mean weight 457 g) 
were exposed to 20 mg/L of chloramine-T for 60 min on four consecutive days in water 
at 8 °C (the most aggressive treatment expected for the label). Groups of 18 fish were 
sampled immediately after the last treatment, then at 1, 3, 6, 12, 24, and 48 hours (19 fish 
taken for the 48-hour sample group) after the last treatment. Duplicate subsamples of 
skin-on fillet tissue from each fish were analyzed with a proposed determinative high 
performance liquid chromatography method for p-TSA in fish fillet tissue. The mean 
concentration of p-TSA in fillet tissue from fish sampled immediately after the last 
treatment was 97.3 ng/g, less than 10 % of the proposed tolerance limit of 1000 ng/g for 
p-TSA in fish fillet tissue (p-TSA concentrations in fillet tissue from individual fish 
ranged from 59.9 to 144 ng/g). Forty eight hours after the last treatment, the mean 
concentration of p-TSA was 73.7 ng/g (p-TSA concentrations in fillet tissue from 
individual fish ranged from 55.3 to 83.7 ng/g).