4.0 NOMENCLATURE SUMMARY
    This section contains information useful to understanding the mathematical notation used for parameters of the exposure pathway and health impact models. The symbols used are presented alphabetically in Table 2 with a brief definition of the parameter and detailed usage of subscripts (if any). For example, the table entry for "C" indicates that C_gwi represents the concentration of pollutant i in groundwater at some defined location. The first subscript has 2 letters ("gw" for groundwater) and the second subscript has one letter ("i" for pollutant).

TABLE 4.1 Summary of Nomenclature Used in Exposure Assessment Models

Parameter	Number of Subscripts	Order of Subscripts	Description
A	1		area of skin exposed for specific pathways (cm2)
		1	exposure activity index (2 letters)
			dd - soil dermal contact
			hd - sediment dermal contact
			sd - showering dermal contact
			wd - swimming dermal contact
ABdi	skin absorption fraction for soil or sediment dermal contact exposure for pollutant i
AD	adhesion factor for contact with soil or sediment with skin (mg/cm2 skin)
AT	2		averaging time for exposure to pollutant i for each pathway (yr)
		1	exposure pathway index (2 letters)
			ae - air submersion external exposure
			ai - air inhalation
			be - boating external exposure
			dd - soil dermal contact
			de - soil external exposure
			di - soil resuspension inhalation
			dr - direct radiation dose (no pollutant subscript is used when the direct radiation dose is considered)
			ds - soil inadvertent ingestion
			dw - drinking water ingestion
			fd - special food ingestion
			ff - finfish ingestion
			sf - shellfish ingestion
			he - shoreline external exposure
			hs- shoreline soil inadvertent ingestion ia - indoor air inhalation
			lv - leafy vegetable ingestion
			kk - general pathway index
			mk - milk ingestion
			mt - meat ingestion
			ov - other vegetable ingestion
			sd - showering dermal contact
			sf - shellfish ingestion
			si - showering inhalation
			sw - shower water inadvertent ingestion
			wd - swimming dermal contact
			we - swimming external exposure
			ww - swimming water inadvertent ingestion
		2	i - pollutant index
b	intermediate parameter in the USEPA dermal absorption model (dimensionless)
B	intermediate parameter in the USEPA dermal absorption model (dimensionless)
B	2		bioaccumulation factors (dimensionless)
		1	foodindex
			f - water-to-fin fish
			s - water-to-shellfish
			v - soil-to-plant uptake via roots
		2	i - pollutant index
BW	1		body weight of individuals exposed to each exposure pathway (kg)
		1	exposure pathway index (see parameter AT for a complete list of subscript usage for exposure pathways)
c	intermediate parameter in the USEPA dermal absorption model (dimensionless)
C	2		concentration of a pollutant in a medium
		1	medium index (2 letters)
			ar - air (mg/m3 or pCi/m3)
			as - surface soil from atmospheric deposition (mg/m2 or pCi/m2)
			dw - domestic water (mg/L or pCi/L)
			ff - finfish (mg/kg or pCi/kg)
			gw - ground water (mg/L or pCi/L)
			lv - leafy vegetables (mg/kg or pCi/kg)
			mf - measured food (mg/kg or pCi/kg)
			ms - measured soil (mg/kg or pCi/kg)
			ov - other vegetables (mg/kg or pCi/kg)
			sa - shower air (mg/m3 or pCi/m3)
			sf - shellfish (mg/kg or pCi/kg)
			ss - shoreline sediment (mg/kg or pCi/kg)
			sw - surface water (mg/L or pCi/L)
		2	i - pollutant index
CAD	2		plant concentration at time of harvest from airborne deposition onto plants (mg/kg or pCi/kg)
		1	plant type index (2 letters)
			lv - leafy vegetables
			ov - other vegetables
			ft - meat animal feed crops
			fk - milk animal feed crops
		2	i - pollutant index
CAR	2		plant concentration at time of harvest from root uptake from soil (mg/kg or pCi/kg)
		1	planttype index
			lv- leafy vegetables
			ov - other vegetables
			ft - meat animal feed crops
			fk - milk animal feed crops
		2	i - pollutant index
CWD	2		plant concentration at time of harvest from water deposition onto plants (mg/kg or pCi/kg)
		1	plant type index
			lv - leafy vegetables
			ov - other vegetables
			ft - meat animal feed crops
			fk - milk animal feed crops
		2	i - pollutant index
CWR	2		plant concentration at time of harvest from root uptake from soil (mg/kg or pCi/kg)
		1	plant type index
			lv - leafy vegetables
			ov - other vegetables
			ft - meat animal feed crops
			fk - milk animal feed crops
		2	i - pollutant index
D	2		average daily dose (mg/kg/d) or lifetime dose (rem)
		1	exposure pathway index (see parameter AT for a complete list of subscript usage for exposure pathways)
		2	i - pollutant index
DE	2		external dose conversion factors for radionuclides
		1	radiation exposure route index
			a - submersion in air (rem/h per pCi/m3)
			g - ground plane (rem/h per pCi/m2)
			w - water immersion (rem/h per pCi/L)
		2	i - radionuclide index
DF	2		internal dose conversion factors for radionuclides
		1	intake route index
			d - dermal (rem/pCi absorbed via skin)
			g - ingestion (rem/pCi ingested)
			h - inhalation (rem/pCi inhaled)
		2	i - radionuclide index
DP	2		deposition rate to crops and ground (mg/m2/d or pCi/m2/d)
		1	medium
			a - atmospheric
			s - soil w - water
		2	i - pollutant index
DR	measured direct radiation dose rate (rem/h)
DSi	diffusion coefficient for skin for pollutant i (cm2/h)
ED	1		exposure duration for each exposure pathway (yr)
		1	k - general exposure pathway index
			(see parameter AT for a complete list of subscript usage for exposure pathways)
f1i	fraction of material absorbed in passing through the GI tract for pollutant i
F	1		fraction of days per year that each exposure pathway occurs
		1	exposure pathway index (see parameter AT for a complete list of subscript usage for exposure pathways)
FC	2		fraction of animal feed or water that is contaminated
		1	intake media
			f - feed
			w - water
		2	animal type
			k - milk animal
			t - meat animal
FE	1		event frequency (events/day)
		1	bt - boating
			dd - soil contact
			sh - showers (showers/day)
			sl - shoreline use
			sw - swimming
FI	1		irrigation time fraction
		1	agricultural product index (2 letters) lv - leafy vegetables mk - milk mt - meat ov - other vegetables
FM	2		feed-to-animal product transfer factors for each pollutant
		1	animal product index (2 letters)
			mk - milk
			mt - meat
		2	i - pollutant index

Hi	Henry's Law Constant for each pollutant, i (atm m3/mole)
HE	1	1	radiation health effects conversion factors (risk per rem) health impact endpoint type f - fatal cancer h - hereditary effects t - total cancer incidence
HQ	2		hazard quotient for exposure to noncarcinogenic chemicals (dimensionless)
		1	intake route index
			g - ingestion
			h - inhalation
		2	i - pollutant index
HT	2		environmental half times for each pollutant (d)
		1	media index
			a - air
			g - ground water (or confined water systems)
			s - surface water
			d - soil
		2	i - pollutant index
I	2		dose absorbed per unit area per water contact event (mg/cm2-event)
		1	water contact event type index
			sh - showering using domestic water
			sw - swimming in surface water
		2	i - pollutant index
Kai	Atmospheric deposition class index by pollutant, i (dimensionless)
Ki                 Volatilization factor for indoor inhalation for pollutant i (L/m3)
Koci	Carbon matter partition coefficient for each pollutant, i (ml/g)
Kowi	Octanol-water partition coefficient for each pollutant, i (ml/g)
Kpi	Skin permeability constant for aqueous solutions for each pollutant (cm/h)
lsc	Thickness of skin (stratum corneum), (cm)
MWi	Molecular weight (g/mole)
NT	Integer number of years in the exposure duration for an agricultural production usage location (yr)
Q	2		animal intake rate of feed or water
		1	intake media
			f - feed
			w - water
		2	animal type
			k - milk animal
			t - meat animal
r	1		fraction of deposition retained on plant surfaces
		1	plant type index
			lv - leafy vegetables
			ov - other vegetables
			ft - meat animal feed crops
			fk - milk animal feed crops
R	3		lifetime risk
		1	health impact endpoint type
			f - fatal cancer
			h - hereditary effects
			t - total cancer incidence
		2	exposure pathway index (2 letters)
			usage is as defined for parameter AT
		3	i - pollutant index
RF	Resuspension factor for inhalation of pollutants deposited onto soil from atmospheric transport (m-1)
RfD	2		chemical reference dose by intake route and pollutant (mg/kg/d)
		1	route index
			g - ingestion
			h - inhalation
		2	i - chemical pollutant index
Si	water solubility for each pollutant, i (mg/L)
SAFi	soil accumulation factor for prior years deposition for pollutant i (dimensionless)
SB	boating shielding factor relative to water immersion (dimensionless)
SF	2		carcinogen slope factor by intake route and pollutant: chemicals risk per (mg/kg/d) dose, radionuclides risk per pCi intake, external risk per ....
		1	route index
			g - ingestion
			h - inhalation
			s - external exposure to surface contamination (radionuclides only)
		2	i - pollutant index
SMFi   SW	measured soil average concentrations over the exposure duration for pollutant i(mg/kg or pCi/kg) shore width factor for external exposure to radionuclides in shoreline sediment (dimensionless)
t	1		thickness of soil or sediment layer (m)
		1	media index (2 letters)
			dd - atmospheric deposition onto soil
			ms - measured soil
			ss - shoreline
			sl - soil
t*	time to reach steady state in the USEPA dermal absorption model (h)
Tsw	transit time in a surface water system between the point of entry and a pumping station (d)
TC	1		crop growing period (d)
		1	plant type index
			lv - leafy vegetables
			ov - other vegetables
			ft - meat animal feed crops
			fk - milk animal feed crops
TE	1		event duration, hours
		1	exposure activities
			b - boating
			d - soil (dirt) dermal contact
			l - shoreline
			s - showering
			w - swimming
TFi	water treatment purification factor giving the fraction of pollutant, i, remaining after treatment (dimensionless)
TH	1		holdupperiod in an exposure pathway (d)
		1	dw - domestic water holdup between the pumping station and the consumer
			ff - harvest to consumer holdup period for the fin fish ingestion pathway
			fs - harvest to consumer holdup period for the shellfish ingestion pathway
			lv - harvest to consumer holdup period for the leafy vegetable ingestion pathway
			ov - harvest to consumer holdup period for the other vegetable ingestion pathway
			mk - harvest to consumer holdup period for the milk ingestion pathway
			mt - harvest to consumer holdup period for the meat ingestion pathway
TV	1		translocation factor from plant surfaces to edible parts of the plant (dimensionless)
		1	plant type index (2 letters)
			lv - leafy vegetables
			ov - other vegetables
			ft - meat animal feed crops
			fk - milk animal feed crops
U	1		intake parameters for each inhalation, ingestion, and some external exposure pathways
		1	ai - air inhalation rate (m3/d)
			de - soil external exposure (h/d)
			di - soil resuspension inhalation rate (m3/d)
			dr - direct radiation (h/d)
			ds - soil inadvertent ingestion rate (g/d)
			dw - drinking water ingestion rate (L/d)
			fd - special food ingestion rate (kg/d)
			ff - finfish ingestion rate (kg/d)
			fs - shellfish ingestion rate (kg/d)
			hs - shoreline soil inadvertent ingestion rate (kg/d)
			k - general pathway index
			lv - leafy vegetable ingestion rate (kg/d)
			mk - milk ingestion rate (L/d)
			mt - meat ingestion rate (kg/d)
			ov - other vegetable ingestion rate (kg/d)
			si - showering inhalation rate (m3/d)
			sw - shower water inadvertent ingestion rate (L/shower)
			ww - swimming water inadvertent ingestion rate (L/h)
Vdi	Deposition velocity (m/sec)
VPi	Vapor pressure (mm Hg)
Y	1		production yield of plants
		1	plant type index
			lv - leafy vegetables
			ov - other vegetables
			ft - meat animal feed crops
			fk - milk animal feed crops
l	2		loss rate constant for a pollutant from a medium (d-1)
		1	medium index
			a - air
			d - soil exposed to air
			e - effective loss from plant surfaces
			g - groundwater or confined water systems
			s - surface water
		2	i - pollutant index
lw	weathering rate constant from plant surfaces (d-1)
r	1		soil or sediment density
		1	media index
			dd - atmospheric deposition onto soil
			ms - measured soil
			ss - shoreline sediment
			sl - soil
t	delay time parameter in the USEPA dermal absorption model (h)