The given concentration units that are ppm and ppb are two parts per notations. They are the abbreviated forms corresponding to parts per million...
Food Safety: Aflatoxins, toxic compounds produced by certain molds, are regulated in foods, with limits often in the range of parts per billion (ppb), which is even smaller than ppm (1 ppm = 1000 ppb). For example, the FDA action level for aflatoxins in corn intended for human consumptio...