Question

One way to estimate maximum acceptable concentrations of toxicants in drinking water or air is to pick an acceptable lifetime risk and calculate the concentration that would give that risk assuming typical exposures, such as recommended by EPA (e.g. Mihelcic Tab. 6.14). Find the acceptable concentrations of the following substances:

a. Benzene in drinking water (mg L-1) at a lifetime acceptable risk of 1 × 10-5

b. Benzene in air (mg m-3) at a lifetime acceptable risk of 1 × 10-6

Answer 1

As per standards the maximum allowable contaminant level for benzene in drinking water as 0.005 mg/L

We will consider body weight = 78 Kg

Drinking rate 2.3 L /day

Life time acceptable risk = 10^-5

We also need cancer potency slope to calculate the same

Generally = 0.015 Kg day / mg

So acceptable limit = life time acceptable risk X body weight / intake of water X cancer potency slope / day

= 10^-5 X 78 / 2.3 X 0.015 = 2.260 X 10^-2 mg / L

b) The breathing rate = 15.2 m^3 /day (assumed)

So acceptable limit = life time acceptable risk X body weight / intake of air X cancer potency slope / day

= 10^-6 X 78 / 15.2 X 0.015 = 3.42 X 10^-4mg / m^3