Question

Chronic dally irve. It can also be FIGURE 4.10 The potency factor is the slope of the dose-response curve. It thought of as the risk that corresponds to a chronic daily intake of 1 mg/kg-da Potency Factory Inhalation Row (mg/kg-dayi 50 2.9 x 10-2 6.11 6.1 8.1 x 10-2 - 41 TABLE 4.9 Toxicity Data for Selected Potential Carcinogens Potency Factor Oral Route Category (mg/kg-day) Chemical 1.75 Arsenic 2.9 X 10-2 Benzene 11.5 Benzol(a)pyrene Cadmium 0.13 Carbon tetrachloride 6.1 X 10- Chloroform Chromium VI 0.34 DDT 1,1-Dichloroethylene 0.58 Dieldrin 30 Heptachlor 3.4 Hexachloroethane 1.4 x 10-2 Methylene chloride 7.5 X 10-3 Nickel and compounds Polychlorinated biphenyls (PCBs) 2,3,7,8-TCDD (dioxin) Tetrachloroethylene 1.56 X 105 1,1,1-Trichloroethane (1,1,1-TCA) 5.1 x 10-2 Trichloroethylene (TCE) Vinyl chloride 1.1 x 10-2 2.3 1.16 1.4 x 10-2 1.19 7.7 1.0 - 3.3 X 100 1.3 X 10-2 0.295 Source: U.S. EPA, www.epa.gov/iris. rather extensive background information on each potential carcinogen in IRIN potency factor and the weight-of-evidence category (recall Table 4.8). A short i some of these chemicals, PFs (for both oral and inhalation exposure routes cancer categories is given in Table 4.9. The other factor we need to develop more fully in order to use the equation (4.12) is the concept of chronic daily intake. The CDI is, by definit CDI (mg/kg-day) = ? Average daily dose (mg/day) Body weight The other fas given in Table 4 oth oral and inhalal! Table 4.8). A short list of xposure routes), and use the basic risk 14.13

Answer 1

Ans a) We know,

I = C x CR x EF x ED / (BW x AT)

where, I = Intake rate (mg /kg-day)

C = concentration of chemical in mg/m³ = 0.0045 $\mu$ gm/m³ or 4.5 x 10^-6 mg/m³

CR = contact rate (m³/day) = 12 m³ /day average inhalation of air for children

EF = Exposure frequency (days/year) = 300 days/year

ED = Exposure duration (in years) = 10 years

BW = Body weight (kg) = 15 kg for children

AT = average period of exposure (days) = (365 days/year x 10 year) = 3650 days

Putting values,

=> I = 4.5 x 10^-6 x 12 x 300 x 10 / (15 x 3650)

=> I = 2.95 x 10^-6 mg/kg-day

Also, Risk = I x Potency factor

According to given table, Potency factor for Arsenic = 50 kg-day/mg

=> Risk = 2.95 x 10^-6 x 50 = 1.475 x 10^-4 > 10^-6

Since, Risk is more than 10^-6 , it is unacceptable

Ans b) acceptable risk = 10^-6

We know,

Risk = I x Potency factor

=> I x 50 = 10^-6

=> I = 2 x 10^-8 mg/kg-day

Also, I = C x CR x EF x ED / (BW x AT)

=> 2 x 10^-8 = C x 12 x 300 x 10 / (15 x 3650)

=> 2 x 10^-8 = 0.657 C

=> C = 3 x 10^-8 mg/m³ or 0.00003 $\mu$ gm/m³

Hence, must reduce its Arsenic concentration to 0.00003 $\mu$ gm/m³ to attain acceptable risk level