By definition 1 PPM is 1 milligram of silver deposited in 1 liter of water (1,000 ml)(1,000,000 mg). (silvergen.com)
«There is no evidence that silver deposits significantly in hair or fingernails and, in fact, the data support the conclusion that after taking more than 2 mg of CS per day for several months, silver seems to be purged from the body (mostly through urine) at about the same rate at which it is consumed.» (clspress.com)
Then I calculate the parts per million (ppm) as a ratio of the mass of silver deposited to the mass of the DW into which it has been deposited. (silvermedicine.org)