What is the average amount of cfDNA present in 1 ml plasma?

According to an interview with Professor Dennis Lo published in QIAGEN News Molecular Diagnostics, Issue No. 5, 2002, healthy individuals have about 500–1000 genome equivalents (DNA) per milliliter of serum/plasma.
For cell-free-circulating DNA in plasma, the concentration can range from 1–100 ng/ml in healthy individuals.