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18 Chapter 4-Causes and Impacts of Salinity estimates of economic damages from salinity in the Colorado River that had been described in earlier studies. Another objective was to provide a better means of estimating present and future salinity damages, basically through the development of a comprehensive and user-friendly personal computer program. A final objective addressed unresolved questions and issues about Colorado River salinity, including areas of damage not previously included in estimates. Damages for salinity above 500 mg/L were estimated to be $311 million in 1986. Studies are underway to update these impacts as salinity increases in the future. Health The Environmental Protection Agency, Drinking Water Office, Health Impacts Laboratory, sponsored a conference in May 1984 on Inorganics in Drinking Water and Cardiovascular Disease. The conference was directed by Dr. Edward Calabrese, one of the original United States researchers in the realm of the health impacts of sodium. It was the study by Drs. Calabrese and Tuthill concerning schoolchildren in two Massachusetts communities that sparked the initiation of many studies around the world. In the study by Drs. Calabrese and Tuthill, a difference of 2 to 5 millimeters (mm) mercury of blood pressure was found between third graders with a drinking water supply of about 10 mg/L sodium and those drinking water of about 102 mg/L sodium. Subsequent attempts by Drs. Calabrese and Tuthill to validate these results with other groups or by other methods (bottled water) have proven inconclusive. Studies reported from the Netherlands did support findings of slightly elevated blood pressure among schoolchildren consuming high sodium water, but most other studies were either inconclusive or showed that there was no effect. Two areas of concern mentioned during the discussions were the use of zeolite water softeners on the kitchen cold water faucet and the cooking of vegetables in high sodium water, as the vegetables can absorb large amounts of sodium during cooking. In most cases, avoidance of these two actions would be more significant than any reduction in raw water concentration. A significant correlation between higher blood pressure and increased cardiovascular disease mortality was presented at the conference. However, the link between sodium and high blood pressure was weak. Other conference discussions on hard versus soft water primarily concluded that soft water was not harmful, but hard water contained some beneficial property, possibly calcium, which reduced the ability of the body to absorb trace metals and thus lowered the overall exposure to such elements as cadmium and lead. Additionally, while water softeners help reduce pipe scaling and soap usage, several speakers stressed that a bypass should be placed on the kitchen cold water tap, the tap most used for drinking and cooking water, to maintain a certain level of hardness. Other papers focused primarily on the health effects of cadmium, barium, and lead in drinking water. Studies seem to indicate that barium has no effect on cardiovascular disease below a level of about 10 mg/L, while cadmium and lead do have a definite adverse impact. None of these elements are present in any significant concentrations in the main stem reaches of the Colorado River. It appears from discussions at the conference that no adverse health impacts related to present sodium or hardness levels occur from drinking water from the Lower Colorado River. Any health effect of a reduction in sodium and hardness expected from the Colorado River salinity control program would be negligible.