First we identify paraquat as a toxicant but not a carcingen

from examining the EPA-IRIS data. It has an "oral RfD"

(reference dose) displayed but no CPF (carc. potency factor).

We enter the values, using for the averaging time,

the actual number of days exposed - here a lifetime

(70 yrs x 365 d = 25,550d).  Pay close attention to the

correct units. 

In the next slide we have calculated the intake (I) as 0.00714 mg/Kg.d,

and need to divide the intake by the RfD from the EPA-IRIS data (online):

Another example:

REVIEW on Carcinogenesis and measurements:

The slope factor (SF) in the slide below

is called CPF in the EPA material

REVIEW OF LOAEL/NOAEL/ADI/RfD

RISK CHARACTERIZATION FOR CARCINOGENS

HERE'S AN EXAMPLE OF THE CALCULATION

This type of calculation is done for a lifetime assuming

worst-possible 2 litres/day for a 70 kg adult. We can

therefore cancel the ED, EF, and AT.  

Risk is calculated as the intake (I) x CPF

So 2 L/d of concentration 0.12 mg/L is 1852 times too high

Here is a analysis table showing water containing several

chemicals, and the risks are shown as the right-hand

column (for lifetime exposure of 2L/d.

 In some examples, we can ask the people not to eat

as much of the food (e.g. certain fish) to lower their

intake, but with water, we would have to give them

alternate supply of water.