PESTICIDES Off-target drift Aerial applications of pesticide to agricultural land often drift elsewhere, causing concern about effects on people, livestock, and the environment. S. L. Bird and co-workers describe formation of the Spray Drift Task Force to develop a comprehensive database of off-target drift information. The task force, composed of 32 pesticide registrants, made an extended field study to identify variables associated with off-target drift. Findings are consistent with previous studies. Atmospheric stability and wind speed were the meteorological parameters that had the greatest effect on drift. The task force concludes that restricting applications during low inversions and controlling droplet size are probably the most cost-effective way to reduce off-site pesticide drift. (J- Environ. Qual. 1996, 25, 1095-1104)
POLICY "Green products" views Consumers have definite perceptions about the biodegradability and environmental friendliness of packaging materials. Y. K. van Dam compared the results of a life-cycle analysis of beverage packages with a survey of consumers' beliefs about the "environmental friendliness" of the packages. Consumers judge environmental acceptability from the material used and the returnability of the package, but they ignore environmental effects of production, which are considered in life-cycle analysis. (Environ. Manage. 1996, 20, 607-14)
REMEDIATION Zero-valent iron barrier Chemical barriers placed below the surface perpendicular to groundwater flow are an emerging technology for in situ remediation of groundwater. They selectively remove targeted contaminants while allowing water and other compounds to pass freely. D. I. Kaplan and colleagues studied the factors influencing the formation
of a zero-valent iron colloid barrier by direct injection. They used sandpacked laboratory columns to simulate field conditions. Colloid retention was influenced by the injection rate and influent colloid concentration. Once retained, colloid removal required flow rates greater than typically observed in groundwater, leading the authors to suggest that an injected iron colloid barrier is not likely to disperse because of groundwater flow. (J- Environ. Qual. 1996, 25, 1086-94)
RISK Best available science Risk assessment is now considered a valid scientific discipline, although it continues to be criticized for failing to incorporate the most recent or best available science into its methodology. J. A. Foran and co-workers point out that identifying and incorporating the best available science can be extraordinarily difficult. Pivotal issues in the discussion of best available science include selection of doses for chronic rodent bioassays, mechanistic considerations in cancer risk assessment, as well as individual human variability. The scientific community is slowly adopting best available science as evidenced by EPA's proposed cancer risk assessment guidelines. (Risk Policy Report 1996, 3(9), 26-29)
Environmental fate Managing new and existing chemical compounds in a sound scientific fashion requires an understanding of a substance's fate after it has been discharged to the environment. D. Mackay and co-workers propose a five-stage process to evaluate the fate of chemicals and the concentrations to which organisms will be exposed. They first assign each chemical to a particular class based on its volatility and solubility. Then, data on use and discharge are compiled. A generic fate assessment follows. The next two phases consider specific environmental conditions of interest to the assessor. Stage four considers global or far-field distribution and fate of the chemical; the last stage is the evaluation of the fate of the chemical in specific local environments. {Environ. Toxicol. Chem. 1996, 15, 1618-26)
1 O A • VOL. 31, NO. 1, 1997 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS
Population-wide risks Traditional models to quantify risk of human infection with waterborne pathogens use endpoint estimates. J. N. Eisenberg and co-workers report a new approach that shifts the risk determination process from point estimate to distributional estimate, and from individual to population. The authors used the model to estimate human risk of giardiasis via ingestion of reclaimed water in a recreational swimming area. Monte Carlo simulations were run using 12 parameter distributions including biological, community, and water treatment parameters. These simulations predicted sources of uncertainty and variability in risk and conditions in which outbreaks were likely. (Risk Anal. 1996, 16, 549-63)
SEDIMENTS Uranium remobilization Major concerns have arisen over environmental contamination near nuclear weapons processing facilities. V. L. Baston and co-workers studied the remobilization of sediment-associated uranium from contaminated floodplain sediments during rainstorms at the U.S. Department of Energy's Savannah River Site. During storms, 1500-2800% more uranium was released to surface water from sediments than was released during stream base flow measurements. Most of the uranium was in a chemically labile form that may make it more available for uptake by aquatic organisms than previously suspected. (J. Environ. Qual. 1996, 25, 1129-37)
Contributors: Michael Brauer, University of British Columbia, Vancouver; Brian Eitzer, Connecticut Agricultural Experiment Station, New Haven; Stephen Geiger, Remediation Technologies, King of Prussia, Pa.; Vincent Hand, Miami University, Institute of Environmental Sciences, Oxford, Ohio; Richard Hurst, CHEMPET Research Corp., Moorpark, Calif; Louis Kovach, Ecolife Associates, Wilmington, Del; Geoffrey Nobes, McGill University, Montreal; Raewyn Town, Queen's University of Belfast, Northern Ireland; and Margaret Whittaker, NSF International, Ann Arbor, Mich.
