Aquatic Monitoring: A Rationale for Obtaining and Interpreting Aquatic Ecosystem Chemical Exposure Data

Abstract

Aquatic hazard evaluation of chemicals requires sound data on both exposure and toxicity so that judgment can be made on the adequacy of the margin of environmental safety. Experience obtained through three years of national aquatic monitoring indicates that chemical monitoring programs need to include the following basic components if the data are to be credible, useful, and consistent with the state-of-the-art results: (1) a rationale for site selection; (2) a logical set of criteria for selection of sample types—that is, water, sediment or biota—based upon the physical-chemical and toxicological properties of the chemical of interest; (3) an appropriate cost-effective statistical design; (4) a team with a demonstrated capability for obtaining noncontaminated samples; (5) a top-notch analytical laboratory with experienced personnel, appropriate instrumentation, and fully validated and tested methods; (6) exacting quality-assurance and quality-control measures in all aspects of the program, including sample collection, sample storage, and analyte determination; (7) an analytical limit of detection for environmental samples low enough to provide meaningful comparisons of biological effects and environmental exposure data; and (8) the capability to assess the monitoring data consistent with state-of-the-art aquatic hazard assessment techniques. Using the above-mentioned components of an aquatic monitoring program, cumylphenyl diphenyl phosphate (CPDPP), a component of an industrial hydraulic fluid, was monitored in 1982 at 24 sites located across the continental United States. Assessment of the hazard of CPDPP for sites where detectable levels were observed was performed by calculating the margin of safety between environmental water concentration and acute and chronic toxicological effects for aquatic organisms inhabiting the water column and sediments. A new approach for assessing chemical concentrations on sediment is proposed. The technique consists of calculating sediment interstitial water concentration of CPDPP and comparing these values with toxicological effect concentrations observed in the laboratory for sediment-dwelling organisms. Concentrations of CPDPP in the environment ranged from < 0.1 to 0.2 μg/L in surface water and from < 100 to 200 μg/kg in sediment. Positive identification of CPDPP occurred in only 12 out of 85 surface water samples and 3 out of 53 sediment samples. CPDPP safety margins were determined to be typically a factor of 10 or greater for the most sensitive water column organism (lake trout) and 390 or greater for a typical sediment dwelling organism. These margins of safety provide evidence that CPDPP at its current use level has a low potential to affect aquatic organisms.