Assume that Peoria\'s drinking water supply contains polychlorinated biphenyls (

Question

Assume that Peoria's drinking water supply contains polychlorinated biphenyls (PCBs) which are chemicals that can disrupt the endocrine system of humans, cause liver damage, and are carcinogenic. Based on exposure assessment and using properly cited values of population, potency (or slope) factor, and the maximum contaminant level, MCL, (mg/L) for PCBs established by the US Environmental Protection Agency (EPA), estimate the: (a) chronic daily intake (mg/kg-day) of PCB by an adult male who consumes one gallon of city water each day and is away from the city a total of two months each year. (b) upper-bound cancer risk per person (c) number of additional cancer cases per year to expect in the entire population

Explanation / Answer

The total population of Peoria as per 2016 is 114265. The maximum contaminant level for PCBs as described by EPA is 0.0005 (mg/l)2. If a person consumes 1gallon of water i.e.3.78 lts . Then chronic daily intake will be

3.78 × .0005 =0.00189mg/day.

In an year of he is 2 months away therefore his yearly intake will be

(365-61) × 0.00189 = 0.574 mg

(b). For each age interval "i", the cancer risk for exposure by a specified pathway is computed as:

Riski = (C x IRi × EFi × EDi × SF × ADAFi)/ (BWi × AT )

Where:

C = Concentration of the chemical in the contaminated environmental medium (soil or water) to which the person is exposed. The units are mg/kg for soil and mg/l for water.

IRi = Intake rate of the contaminated environmental medium for age bin "i". The units are mg/day for soil and l/day for water.

BWi = Body weight of the exposed person for age bin "i".( Let us consider it as 70kg )

EFi = Exposure frequency for age bin "i" (days/year). This describes how often a person is exposed to the contaminated medium over the course of a typical year.(365-61) days

EDi = Exposure duration for age bin "i" (years). This describes how long a person is exposed to the contaminated medium over the course of their lifetime. (Let us consider person is exposed to it from 30 years)

AT = Average days. This term specifies the length of time over which the average dose is calculated. For quantifying cancer risk a "lifetime" of 70 years is used (ie, 70 years times 365 days/year).

SF = Cancer slope factor (mg/kg-day)1

ADAF = Age-dependant adjustment factor for age bin "i" (unitless)

Risk = (0.0005 × 0.00189 × 304 x 30 × 0.00189)/ (70 × 70)

= 3.324 × 10^-9

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