Suppose drinking water contains 0.14 mg/L Carbon tetrachloride. A 70 kg adult dr
ID: 1711074 • Letter: S
Question
Suppose drinking water contains 0.14 mg/L Carbon tetrachloride. A 70 kg adult drinks 2 L of water per day for 10 years. Carbon tetrachloride is a Category B2 carcinogen with a oral potency factor of 0.13 mg/L. The reference dose for Carbon tetrachloride is 0.01 mg/kg-day. a) What does reference dose mean? How is it calculated? b) Explain the potency factor and how it is calculated c) How can the risk become zero for a person drinking this water? d) What is the hazard index for this person? e) What is the CDI? f) What is the risk? g) Does this meet the goal of lifetime risk assessment? Explain...Explanation / Answer
a) Reference Dose (Rdf) : It is a benchmark dose operationally derived from the NOAEL ( NO-Observed-Adverse-Effect-Level) by consistent application of generally order-of-magnitude uncertainity factors that reflect various types of data sets used to estimate Rfd's.
The Rdf is determined by use of the following equation:
RfD = NOAEL / (UF x MF); MF = Modification Factor
b) Potency Factor: Cancer Slope Factor (CSF) is used to drive the Risk Specific Dose (RSD)(mg/kg-day) for direct-acting carcinogenic agents, those that cause chemical changes in DNA.
CSF = 0.000001 / RSD
c) RIsk = Intake rate x Potency factor
the risk can be zero by making the intake rate zero.
e) Combined Drug Intoxication: It is an unnatural cause of human health. CDI is often confused with drug overdose, which is actually not the case. It is mainly due to simultaneous use of multiple drugs.
f) Intake Dosage (I) = C (CR x EF x ED ) / (BW x AT)
C = average concentration of contaminant at exposure (in mg/L if in water, or mg/mg if in soil, or mg/m3 if in air)
CR = contact rate (in L/day, mg/day or m3/day) ;EF = exposure frequency (in days per year) ;
ED = exposure duration (in years) ;BW = body weight (in kg); AT = period over which exposure is averaged (in days)
I = 0.14 ( 0.01 x 365 x 10) / ( 70x 1) = 0.073
risk = I x Potency factor = 0.073 x0.13 = 9.49 x 10-3