The ppm ppb, ppt, dioxin dilemma By Norman E. Skelly April 30, 2005 The contaminant "dioxin", chemically known as 2,3,7.8-tetrachlorodibenzo-p-dioxin or abbreviated as 2,3, 7,8 TCDD is of concern ...

It is also equivalent to one part per billion (ppb). One ppb is 1,000 times a part per million. Concentrations measured in ppm and ppb are so small that they can be difficult to conceptualize.