A graph showing the Giardia-related burden of illness in DALYs per person per year as a function of the CT level in milligram minutes per litre. The x-axis of the graph is the CT values in milligram minutes per litre. It is presented on a linear scale and the axis values range from 0 to 70. The y-axis of the graph is the DALYs per person per year. It is presented on a linear scale and the axis values range from 1 x 10-10 to 8 x 10-10 with the x-intercept at zero. The graph includes two vertical dotted lines. The first line indicates the minimum CT requirement for a 0.5 log inactivation for Giardia. This line is at 13 milligram minutes per litre. The second vertical dotted line indicates the actual CT applied in the example. This line is at 30 milligram minutes per litre. There are two lines plotted on the graph. The first plotted line shows the burden of illness from Giardia as the CT level increases for water treated using filtration and chlorine. This line is shaped like an exponential decay curve. The curve begins at a burden of illness from Giardia of 8 x 10-10 DALYs per person to year at 1 milligram minute per litre and decays to approximately 0 DALYs per person per year at 60 milligram minutes per litre. The curve intercepts the two vertical dotted lines at approximately 2.5 x 10-10 (at 13 milligram minutes per litre) and at approximately 0.5 x 10-10 (at 30 milligram minutes per litre). The second line shows the burden of illness from Giardia as the CT level increases for water treated using filtration, chlorine and ultraviolet light. This line is horizontal, intercepting both vertical dotted lines at approximately 0.