ACUTE TOXICITY OF PERACETIC ACID TO FISH

Peracetic acid (PAA; also called peroxyacetic acid) is a stabilized mixture of acetic acid, hydrogen peroxide and water that does not leave dangerous residues in the environment when it breaks down as most compounds do.  PAA is a promising disinfectant in the US aquaculture industry to control parasites and fungus.  The US Environmental Protection Agency (EPA) first registered PAA as an antimicrobial in 1985 for indoor use on hard surfaces (hospitals).  EPA registrations now include: sanitation in food/beverage plants, agricultural premises, wineries/breweries, greenhouse equipment, and animal housing.  PAA is also used to prevent bio-film formation in paper/pulp industries and as a disinfectant for wastewater treatment.  PAA is used extensively in Europe, and our international collaborations have studied its effectiveness to many pathogens.  However, there is a lack of data on its toxicity to fish.

This study determined the acute toxicity of PAA to 12 fish species in well water.  The experiments were designed to provide the 24 h LC50 (median lethal concentration), LOEC (lowest observed effect concentration) and NOEC (no observed effect concentration) values for each species at ~ 23°C.  Ten fish were placed in static aquaria containing 10 L of well water.  Each experiment consisted of 6 PAA concentrations and an untreated control (n=3).  Water chemistry for the well water was: pH = 7.5, total alkalinity = 200 mg/L, total hardness = 125 mg/L.  The mean LC50 value for all species tested was 5.3 mg/L PAA with the range of 2.8 mg/L to 9.3 mg/L.  Black fathead minnows and blue tilapia were most and least sensitive, respectively.  The mean NOEC value for all species tested was 3.7 mg/L PAA with the range of 1.9 mg/L to 5.8 mg/L.  The immediate impact of this research is to understand the toxicity variance among species and ultimately to determine safe and effective therapeutic treatments.