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<br />Environmental <br /> <br />There has been a concern about the toxicity of the most cornmon cloud seeding material, <br />silver iodide (AgI) on the environment. The typical concentration of silver in rainwater <br />or snow from a seeded cloud is less than 0.1 micrograms per liter. The Environmental <br />Protection Agency recommends that the concentration of silver in drinking water not <br />exceed 0.10 milligrams per liter of water. Many regions have much higher <br />concentrations of silver in the soil than are found in seeded clouds. Industry emits 100 <br />times as much silver into the atmosphere in many parts of the country, and silver from <br />seeding is far exceeded by individual exposure from tooth fillings. The concentration of <br />iodine in iodized salt used on food is far above the concentration found in rainwater from <br />a seeded storm. No significant environmental effects have been noted around operational <br />projects, many of which have been in operation for 30 to 40 years (WMA, 1996). <br /> <br />Although several NEP A documents have been prepared for WxMod programs, the only <br />three that have been located are: <br /> <br />"Sierra Cooperative Pilot Project. Envirorunental Assessment and Finding of No Significant Impact". Edward R. Harris, <br />Office of Atmospheric Resources Research, US Bureau ofReclamalion. August 19&1. <br /> <br />"Final Supplement to the Environmental Impact Statement Environmental Impact Report, Prototype Project to Augment <br />Snowpack by Cloudseeding using Ground Based Dispensers in Plumas and Siena Counties", Forest Service. U.S. <br />Department of Agriculture and California Department of Water Resources. October 1991 and Joint Environmental Impact <br />Statement Envirorunentallmpact Report, Prototype Project to Augment Snowpack by Cfoudseeding using Ground Based <br />Dispensers in Plumas and Sierra Counties, September 1990. <br /> <br />"Environmental Assessment for the Pacific Gas and Elctbic Company Mokelumne Weather ModirlCation Program". <br />Parsons Engineering Science, Inc.. October 1995. (prepared for Pacific Gas and Electric Company and the U.S. Forest <br />Service. Stanislaus National Forest) <br /> <br />The Wyoming Water Development Commission has begun planning a process for <br />compliance with the National Environmental Policy Act for their proposed Weather <br />Modification Five-Year Pilot Program. Wyoming and its partners are currently deciding <br />on the lead federal agency and what type of environmental document would be <br />appropriate. <br /> <br />Anthropogenic Effects <br /> <br />There have been recent articles describing studies at the Desert Research Institute in <br />Nevada (Borys et aI. 2003), and Hebrew University of Jerusalem (Rosenfeld 2000) about <br />the role of air pollution in reducing precipitation. In sum, researchers are demonstrating <br />that human-induced air pollution is reducing precipitation from clouds. Long-term <br />studies have also linked polluted air from increased urbanization to drought conditions <br />(Rotstayn and Lohmann, 2002). Air pollution generated in urban areas generates very <br />small (less th.an 1 micron in size) particles. The microphysical cloud process involves <br />more numerous smaller moisture-attracting particles, which results in fewer cloud <br />droplets that grow heavy enough to fall as rain; i.e., there are fewer large particles of an <br />optimal nucleating size. It has been estimated that pollution-contaminated clouds can <br />produce half as much snow as pristine clouds. A recent study by Hindman et aI. (2005) <br /> <br />-20- <br />