# science calculation

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You have been asked to complete a screening-level risk assessment in order to compare routes of chemicals exposure and to determine whether the chemical exposure poses a potential health risk.

The receptor is a 70 kg man who has worked 8 hours per day as an auto mechanic for 25 years. The chemical of concerns is benzene that is a proven carcinogen and is a constituent of gasoline as well as automobile exhaust gas.

Calculate Estimated Daily Intake (EDI) for the two following routes of exposure given the information listed below (8 points):

Inhalation with an air concentration of 12.8g/m3 at all times of the day for 25 years (this is the highest mean concentration measured in the City of Toronto)

Skin transfer through the grease that covers his hands during work time (occupational exposure).

Discuss briefly: through which medium does the receptor receive his/her greatest exposure? Explain why? (2 points)

Calculate the Relative Margin of Safety (RMOS). (7 points)
Discuss your results (is the RMOS “OK” or not, provide references to support your findings)
(3 points).

Assume that the concentration of benzene in the grease layer on hands is in equilibrium with the air concentration.

DATA:
Equation for exposure due to inhalation, EDIair (g/kg body weight /day):

EDIair = (IR x C x B x EF x ED)/BW x AT

Where:
IR (inhalation intake rate): 0.96m3/h
C (concentration of benzene in air): 12.8g/m3
B (bioavailability factor): 1 (100% for all compartments)
EF (occupational exposure frequency): 8 hours per day, 5 days per week, 50 weeks per year
ED (exposure duration): 25 years
BW (body weight): 70 kg
AT (averaging time for a carcinogen): 70 years

• science calculation -

sorry this is the continuation:

quation for exposure due to skin transfer, EDIskin (g/kg body weight /day):

EDIskin = (C x P x SA x B x EF x ED)/BW x AT

Where :
C (chemical concentration): 12.8g/m3
P (permeability constant): 0.0011m/h
SA (skin surface area): 0.091m2 for hands only
B (bioavailability factor): 1 (100% for all compartments)
EF (occupational exposure frequency): 8 hours per day, 5 days per week, 50 weeks per year
ED (exposure duration): 25 years
BW (body weight): 70 kg
AT (averaging time for a carcinogen): 70 years

Equation for the RMOS (Calculate the Relative Margin of Safety):

RMOS= EDI total/RsD

Where:
EDI total (Total Estimated Daily Intake from all routes of exposure) = EDI skin + EDI air
RsD (Risk Specific Dose)

Equation for the RsD:

RsD=R /Sf
Where:
R (acceptable risk): 10 -5
Sf (Slope factor for benzene): 29 (g/kg body weight day) -1

• env.science -

is the answer for inhilation 125.28?

• science calculation -

tsk tsk tsk, the answer for this question is simple:

1.Refer to class lecture 9 slides posted online on the intranet.
2.attend lectures or watch them online if you cannot make it.
3.attend TA office hours which are held every day of the week.

Thank you

• science calculation -

AT (averaging time for a carcinogen): 70 years

AT SHOULD STAND FOR DAYS

SO AT = 70 X 365

• science calculation -

a= 1.g/kg/day

aii= 1.5g/kg/day +.0000273g/kg/day

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