the mirror image of the precautionary principle, said Wendy Wagner, associate law professor at Case Western Reserve University in Cleveland, Ohio. Despite TSCA's goals, many of which are precautionary in nature, actual implementation does not follow a precautionary approach. "The precautionary principle calls for regulatory intervention when we know nothing, but TSCA doesn't begin [to take effect] until we have some knowledge" of harm, Wagner said. For
example, although chemical manufacturers are required to turn in results of any product testing, they are not required to conduct tests in the first place. "EPA has the authority to require additional testing from manufacturers, but an observable threshold effect is the prerequisite before testing can be required of any chemicals not produced in large quantities. To ban, the burden on EPA is higher still," Wagner said. Yet, despite roadblocks, some new initiatives seem to be consis-
tent with application of the precautionary principle in chemical regulations. As an example, Wagner cited EPA's high production volume chemical testing program, which encourages companies to voluntarily conduct toxicity testing on chemicals produced in volumes greater than 1 million pounds per year (ES&T 1999, 33(1), 15A). Another objective being pushed by environmental organizations is to require warning labels on products that have not been tested. —KRIS CHRISTEN
Predicted summer water shortages attributed to climate change Global climate change will reduce the amount of western water stored as snow, leading to increased risk of winter flooding and summer water shortages, announced scientists at a May conference on climate change, sponsored by the American Water Resources Association. Some experts attending the meeting contended that local water managers are unwilling and ill-prepared to reduce the vulnerability of their water supply systems to extreme events triggered by global warming. Global change modelers agree that average winter temperatures in the Pacific Northwest will increase by about 2.7-3.4 °C over the next 50 years, according to Dennis Lettenmaier, civil and environmental engineering professor at the University of Washington-Seattle. This temperature rise will drive the snow line further up the mountains: By 2055, the area covered by snow could drop by nearly half, predicted Lettenmaier and his colleagues. In theory, said Peter Gleick, director of the Pacific Institute in Oakland, Calif., local water managers could adapt to the changes by increasing winter storage capacity and conserving water. For instance, last year water managers at the Folsom Dam on the American River upstream from Sacramento responded to predictions of increased runoff from El Nino by creating extra reservoir storage space, thus preventing enormous damages. But the problem is that modelers are not providing managers with predic-
If climate change modelers' predictions come true, water managers in the West will no longer be able to rely on winter snow to provide summer water.
tions of extreme events, and managers are uninterested in planning for events that are uncertain and more than five years in the future, Gleick said. In the West, snowmelt currently accounts for 70% of stream flow, and storage of water in the snow pack is a reservoir that water managers do not have to build, Lettenmaier explained. The higher winter temperatures mean more precipitation will fall as rain and result in larger stream flows earlier in the spring and smaller flows in summer. "More rain and less snow will increase the risk of flooding in winter and supply shortages in the summer," Gleick concluded. This will complicate the management of reservoirs already stressed by rapid population growth, demands from agriculture, and reduced storage capacity due to sedimentation. Gerald Hansler, retired executive
director of the Delaware River Basin Commission, countered that "natural climate aberrations will outweigh effects caused by global climate change." Nevertheless, managers' planning assumptions based on past climate records need to be reworked, he noted. For instance, he said, water management in the Colorado River basin has been based on the climate record of the last 50 years, but new research using tree rings has shown those years to be the wettest of the last few hundred. "The fact that the modelers brought up the issue of reduced snow pack and extreme events was a good wake-up call" for water managers, Hansler concluded. The conference proceedings will become part of the "U.S. National Assessment: The Potential Consequences of Climate Variability and Change," to be presented to Congress in lanuary 2000. —JANET PELLEY
AUGUST 1, 1999 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS • 3 0 5 A
