(a) Standards and guidance values for protection of the best usage as a source of potable water supply shall protect human health and drinking water sources and are referred to as Health (Water Source) values.

(b) The standard or guidance value shall be the most stringent of the values derived using the procedures found in sections 702.3 through 702.7 of this Part.

(c) Standards or guidance values based on oncogenic effects that are based on the 95 percent lower confidence limit on the human dose corresponding to an excess lifetime cancer risk of one-in-one million or on chemical correlation to such effects shall be derived using age-specific water consumption rates and points-of-departure for a lifetime exposure period of 70 years if scientific evidence is sufficient to show that children may be more sensitive than adults to such oncogenic effects. If such scientific evidence is not available, a consumption rate of two liters of water per day for a lifetime exposure period of 70 years shall be used.

(d) Standards or guidance values based on oncogenic effects that are based on the human equivalent dose at the point-of-departure divided by an uncertainty factor, chronic nononcogenic effects, or chemical correlation to such effects shall be derived using age-specific water consumption rates for a childhood exposure period (18 years or less) if scientific evidence is sufficient to show that children may be more sensitive than adults to such effects. If such scientific evidence is not available, a consumption rate of two liters of water per day shall be used.

(e) Standards or guidance values based on acute nononcogenic effects or chemical correlation to acute nononcogenic effects shall be derived using a consumption rate of one liter of water per day or a different water consumption rate if deemed more appropriate based on scientific evidence.