A liter of water weighs a kilogram so 15 mg/kg = 15 ppm on a mass over mass basis. If that is the flavor of ppm you want, done. But ppm can also be computed on a volume basis, molar ratio, etc. It is better tio use a clear form with units that identifies the basis such as mg/kg.
Serena Williams knocked off Lucie Safarova in the final of the women's draw at the French Open, and Bovada has her listed as the clear favorite on the odds to win Wimbledon this year; Williams sits as the 7/4 chalk on those betting lines.
World No 18 Johanna Konta will be seeded at Wimbledon next week. She will be the highest seeded British female since Jo Durie in the 1980s. Never before has the tale been told of her early development in Australia. Konta's parents once had a county court judgement taken out against them for non-payment of coaching fees.