5.2 EXPOSURE PATHWAY PARAMETERS

    The parameters for each exposure pathway are described in the following subsections. Default parameter values are provided for those parameters that are not pollutant specific. For pollutant-specific parameters, see the MEPAS chemical database report (Strenge and Peterson 1989).

    For each primary medium of usage, parameters must be defined for the exposed population or individuals. These parameters are exposure duration, body weight, and averaging time. The default values for these parameters are set as used in the original MEPAS formulations (Whelan et al. 1987; Droppo et al. 1989). The values are as defined in Table 5.2.

    The exposure duration may be set by the user for each of the usage media (locations) defined. The body weight may also be set; however, a value of 70 kg is always used for radionuclides because the radiation dose conversion factors are base on the standard man parameters (70 kg). The averaging time is not set by the user. For carcinogenic chemicals the averaging time is fixed at 70 years. For noncarcinogenic chemicals, the averaging time is set equal to the exposure duration.

TABLE 5.2 General Exposure Parameter Default Values
 

Parameter		Definition		Default Value
				Individual		Population
ED		Exposure Duration (yr)		70		70
BW		Body Weight (kg)		70		70
AT		Averaging Time (yr)		70		70