What are the safe levels of contaminants in drinking water for horses?

Water samples should be taken to an lab to determine contaminant amounts.
Following are the recommended safe upper levels of water contaminants:
UPPER SAFE LEVEL
CONTAMINANT

    Arsenic – 0.2 parts per million (ppm)
    Cadmium – 0.05 (ppm)
    Calcium – 500.0 (ppm)
    Chloride – 3,000.0 (ppm)
    Chromium – 1.0 (ppm)
    Copper – 1.0 (ppm)
    Fluoride – 6.0 (ppm)
    Hardness – 200.0 (ppm)
    Iron – 0.3 (ppm)
    Lead – 0.1 (ppm)
    Magnesium – 125.0 (ppm)
    Mercury – 0.01 (ppm)
    Nitrate – 200.0 (ppm)
    pH – 6.0 – 8.5 (ppm)
    Potassium – 1,400.0 (ppm)
    Selenium – 10.0 parts per billion (ppb)
    Sodium – 2,500.0 (ppm)
    Sulfate – 250.0 (ppm)
    TDS(total digestible solids) – 6,500.0 (ppm)
    Zinc – 15.0 (ppm)