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18 <br />0 MINE EFFLUENT POLLUTION <br />Just what is pollution and what concentration levels <br />constitute a problem? Neither question has a unique answer. <br />An operational definition of pollution is something that is <br />harmful and unwanted at a certain time and place. Mine <br />effluents are unwanted in the particular operation that is <br />being employed. If an operation switched to solution mining <br />or added a mill, the water might be quite useful. The con- <br />centration levels that constitute a problem relate to the <br />harmfulness of the water. In this area, there are three <br />answers and all of them are subject to revision. <br />HEALTH STANDARDS <br />• The traditional approach to defining harmfulness is to <br />compare the concentration of the constituents in the water <br />against water that is fit to drink. Up to 1975, the U.S. <br />Public Health Service had defined recommended limits and <br />maximum permissible concentrations for drinking water. <br />These are listed in Table III. <br />In 1975, the EPA and the state governments took over <br />the establishment and enforcement of drinking water regula- <br />tions (31). They established maximum contaminant levels <br />(MCL) and these are also listed in Table III. Where there <br />is a discrepancy between the old and new drinking water <br />standards, research is being done to establish a maximum <br />concentration limit. The difference between the old and <br />• new standards is primarily philosophical. The old standards