The New York State Department of Environmental Conservation (NYS DEC) requires permittees to obtain authorization for use of Water Treatment Chemicals (WTC) prior to their use to minimize the potential for unacceptable toxicity in a facility’s wastewater discharge. Aquatox Research, Inc. (ARI) offers freshwater chemical toxicity testing services with larval fathead minnows (Pimephales promelas) and the invertebrate Ceriodaphnia dubia. ARI routinely conducts both acute and chronic tests with these species in support of testing requirements imposed by the NYS DEC on facilities that utilize chemical products to treat their wastewater prior to discharge to a surface water.

A standardized approach to aquatic toxicity testing of chemicals begins with a preliminary screening test to define the toxic range using an order of magnitude dilution series (e.g. 1, 10, 100 and 1,000 mg/L or ppm). The subsequent definitive test employs a narrower range of treatment concentrations (typically 50% or greater) in order to generate a median lethal concentration (LC50) in acute, short-term (48-hr durations) tests. Both acute screening and definitive tests are required in the event chronic toxicity data are requested. Each test in sequence provides valuable information to best design subsequent chronic tests. The goal of chronic tests are to generate product concentrations at which there are no effects whatsoever (no-observed-effect-concentration; NOEC) and sublethal effects (lowest-observed-effect-concentration; LOEC). A third endpoint of chronic tests is the 25% Inhibition Concentration (IC25). The NYS DEC compares the recommended application rates for the products of interest against the chronic test data endpoints in order to judge the environmental acceptability of the products of interest.

An alternate approach to toxicity testing of chemicals and chemical products employed by the NYS DEC involves granting conditional approval for use of WTC followed by a minimum of three months of chronic WET testing to demonstrate the environmental acceptability of the treatment program. The selection of the approach approved by the DEC often involve site-specific criteria.