Which of the following is a measurement unit for endotoxin levels?

Endotoxin levels are specifically measured in Endotoxin Units per milliliter, commonly abbreviated as EU/ml. This unit quantifies the presence of endotoxins, which are toxic substances released from the outer membrane of certain bacteria upon their destruction. The measurement in EU is significant because it directly correlates to the potency of the endotoxin, which can have important implications in medical contexts, particularly in pharmaceuticals and medical devices where endotoxin contamination is a critical concern.

Other units mentioned, such as CFU/ml, are used specifically for determining the concentration of colony-forming units of viable bacteria, not for measuring endotoxins. Similarly, mg/ml commonly denotes concentrations of a substance in milligrams per milliliter and does not apply specifically to endotoxins. Parts per million (ppm) is a general concentration measurement that can be used for various substances, but it lacks the specificity needed for quantifying endotoxin levels. Thus, EU/ml is the most appropriate and accurate unit for measuring endotoxin levels.