2.11 SWIMMING DERMAL CONTACT
Individuals swimming will be exposed to contaminated
water via the dermal absorption pathway from contact with water. The following
considerations are given to estimate the dermal contact exposure to surface
water while swimming.
- Transport Medium:
- surface water concentration in the water body used for swimming, Cswi, pCi/L or mg/L, expressed
as a 70-year average value
- Special Process:
- loss of pollutants during transport in the surface water body by volatilization or decay absorption through the skin during a swimming event
- Exposure Factors:
- area of skin exposed, swimming frequency, swimming event time, and exposure duration.
The loss of pollutants during transport in the surface
water body is evaluated using Equation (3). The swimming frequency and
time period of each swimming event determine the average time spent swimming
per day. The swimming event time and absorption parameters for each pollutant
are used to estimate the amount of a pollutant absorbed through the skin
during each swimming event. This calculation is performed using the same
dermal absorption model described for the shower dermal absorption exposure
pathway in Subsection 2.2.
For inorganic chemicals and radionuclides, the intake per swimming event per unit area of skin contacted is evaluated as follows:
(72)
where
Iswi = amount of pollutant absorbed through the skin during one swimming event per unit area of skin contacted (mg/cm2/event or pCi/cm2/event)
10-3 = units conversion factor (L/cm3)
Cswi = concentration of pollutant i in surface water at the swimming location (mg/L or pCi/L)
Kpi = skin absorption permeability constant for pollutant i (cm/h)
TEw = duration of one swimming event (h).
For organic pollutants, the absorption per event is
evaluated using the six-step process described in Subsection 2.2 by Equations
(5) through (12). These equations give the amount of a pollutant absorbed
per unit area of skin contacted during one swimming event of duration TEw.
In performing the evaluation for swimming exposures, the swimming event
time is used in place of the showering event time, TEs.
The average daily dose from chemical pollutants for
the swimming dermal contact exposure pathway is evaluated as follows, with
correction for the gastrointestinal tract absorption fraction:
(73)
where
Dwdi = average daily dose from chemical pollutants via dermal absorption from water contact while swimming, equivalent to oral intake (mg/kg/d)
Iwdi = dose absorbed per unit area of skin contacted per swimming event (mg/cm2/event)
Awd = area of skin exposed to contaminated water while swimming (cm2)
FEsw = frequency of swimming events (events/day)
Fwd = fraction of days per year that swimming occurs (dimensionless)
EDwd = exposure duration for the swimming dermal contact exposure pathway (yr)
ATwdi = averaging time for swimming dermal contact for pollutant i (yr)
BWwd = body weight of exposed individual for the swimming dermal contact pathway (kg)
f1i = fraction of pollutant i absorbed in passing through the GI tract following ingestion (dimensionless).
The average daily dose as computed by Equation (73)
is equivalent to oral exposure because the GI absorption correction has
been applied. The averaging time for noncarcinogenic chemicals is set to
the exposure duration, and the averaging time for carcinogenic chemicals
is fixed at 70 years. The equation is used for all pollutants except radionuclides.
For radionuclides, the GI absorption fraction and body weight are not applied
because radionuclide specific dose conversion factors for dermal intake
are provided in the chemical database for the 70-kg reference man. The
equation for radionuclides is as follows:
(74)
where
Dwdi = total lifetime dose from radionuclide pollutants via dermal absorption from water contact while swimming (rem)
Iwdi = dose absorbed per unit area of skin contacted per swimming event (pCi/cm2/event)
DFdi = dose conversion factor for dermal absorption of radionuclide i (rem/pCi)
and other terms are as previously defined.