You might know that it's not a good idea to drink bleach, but how do you quantify how lethal bleach is to an organism? The answer is the humble kill curve. Take a bunch of the organism you're testing and expose different individuals to different amounts of the possibly lethal factor. It could be milliliters of bleach, seconds exposed to ultraviolet light, or any other number of things.
When you have your results, it's time to plot the kill curve. On the y-axis is percentage of organisms left alive and on the x-axis is amount of potentially lethal factor. The curve should go from no exposure to factor (100% survival) to the amount of exposure that results in 0% survival. It's a bit grim, but there's a reason they don't call it a life curve.