fundamentals of engineering supplied-reference handbook - Ventech!

Exposure
Residential Exposure Equations for Various Pathways
Ingestion in drinking water
CDI = (CW)(IR)(EF)(ED)
(BW)(AT)
Ingestion while swimming
CDI = (CW)(CR)(ET)(EF)(ED)
(BW)(AT)
Dermal contact with water
AD = (CW)(SA)(PC)(ET)(EF)(ED)(CF)
(BW)(AT)
Ingestion of chemicals in soil
CDI = (CS)(IR)(CF)(FI)(EF)(ED)
(BW)(AT)
Dermal contact with soil
AD = (CS)(CF)(SA)(AF)(ABS)(EF)(ED)
(BW)(AT)
Inhalation of airborne (vapor phase) chemicals a
CDI = (CA)(IR)(ET)(EF)(ED)
(BW)(AT)
Ingestion of contaminated fruits, vegetables, fish and shellfish
CDI = (CF)(IR)(FI)(EF)(ED)
(BW)(AT)
156
ENVIRONMENTAL ENGINEERING (continued)
where ABS = absorption factor for soil contaminant (unitless)
AD = absorbed dose (mg/[kg•day])
AF = soil-to-skin adherence factor (mg/cm 2 )
AT = averaging time (days)
BW = body weight (kg)
CA = contaminant concentration in air (mg/m 3 )
CDI = chronic daily intake (mg/[kg•day])
CF = volumetric conversion factor for water
= 1 L/1,000 cm 3
= conversion factor for soil = 10 –6 kg/mg
CR = contact rate (L/hr)
CS = chemical concentration in soil (mg/kg)
CW = chemical concentration in water (mg/L)
ED = exposure duration (years)
EF = exposure frequency (days/yr or events/year)
ET = exposure time (hr/day or hr/event)
FI = fraction ingested (unitless)
IR = ingestion rate (L/day or mg soil/day or kg/meal)
= inhalation rate (m 3 /hr)
PC = chemical-specific dermal permeability constant
(cm/hr)
SA = skin surface area available for contact (cm 2 )
Risk Assessment Guidance for Superfund. Volume 1, Human Health Evaluation Manual (part A). U.S. Environmental Protection Agency, EPA/540/1-89/002, 1989.
a
For some workplace applications of inhalation exposure, the form of the equation becomes:
( α)( BR)( C)( t)
Dosage =
( BW )
where
Dosage = mg substance per kg body weight
α = percent of chemical absorbed by the lungs (assume 100% unless otherwise specified)
BR = breathing rate of the individual (1.47 m 3 /hr for 2 hr or 0.98 m 3 /hr for 6 hr; varies some with size of individual)
C = concentration of the substance in the air (mg/m 3 )
BW = body weight (kg), usually 70 kg for men and 60 kg for women
t = time (usually taken as 8 hr in these calculations)
Based on animal data, one may use the above relations to calculate the safe air concentration if the safe human dose (SHD) is known, using the following
relationship:
SHD
C =
( α)(
BR)( t)