as grams per 1,000 liters, which may be converted to mil- ligrams per liter (mg/L). Therefore, 1 g/m3 = 1 mg/L = 1 ppm. Likewise, one milligram per cubic meter (mg/m3) is the same concentration in water as one microgram per liter (ug/L), which is about 1 ppb.read more >>