Section 302.663  Determination of Bioconcentration Factors

A Bioconcentration Factor equals the concentration of a substance in all or part of an aquatic organism in milligrams per kilogram of wet tissue weight (mg/kg), divided by the concentration of the substance in the water to which the organism is exposed in milligrams of the substance per liter of water (mg/L).

a)         The Bioconcentration Factor is calculated from a field study if the following conditions are met:  

1)         Data are available to show that the concentration of the substance in the water to which the organism was exposed remained constant over the range of territory inhabited by the organism and for a period of time exceeding 28 days;

2)         Competing mechanisms for removal of the substance from solution did not affect the bioavailability of the substance; and

3)         The concentration of the substance to which the organism was exposed is less than the lowest concentration causing any adverse effects on the organism.

b)         In the absence of a field-derived Bioconcentration Factor, the Bioconcentration Factor is calculated from a laboratory test if the following conditions are met:

1)         The Bioconcentration Factor was calculated from measured concentrations of the toxic substance in the test solution;

2)         The laboratory test was of sufficient duration to have reached steady state, which is defined as a less than 10 percent change in the calculated Bioconcentration Factor over a 2-day period or 16 percent of the test duration, whichever is longer.  In the absence of a laboratory test that has reached steady state, the Bioconcentration Factor may be calculated from a laboratory test with a duration greater than 28 days if more than one test is available for the same species of organism;

3)         The concentration of the toxic substance to which the test organism was exposed is less than the lowest concentration causing any adverse effects on the organism;

4)         If more than one Bioconcentration Factor for the same species is available, the geometric mean of the Bioconcentration Factors is used; and

5)         The Bioconcentration Factor is calculated on a wet tissue weight basis.  A Bioconcentration Factor calculated using dry tissue weight must be converted to a wet tissue weight basis by multiplying the dry weight bioconcentration value by 0.1 for plankton and by 0.2 for individual species of fish and invertebrates.

c)         In the absence of any Bioconcentration Factors measured from field studies as specified in subsection (a) or laboratory studies that have reached steady state as specified in subsection (b), the Bioconcentration Factor is calculated according to the equation:

log BCF = A + B log Kow

Where:

BCF = Bioconcentration Factor;

Kow = The octanol/water partition coefficient measured as specified in ASTM E 1147, incorporated by reference in 35 Ill. Adm. Code 301.106 (If the Kow is not available from laboratory testing, it must be calculated from structure-activity relationships or available regression equations.); and

The constants A = -0.23 and B = 0.76 must be used unless a change in the value of the constants is requested (The Agency must honor requests for changes only if the changes are accompanied by scientifically valid supporting data.).

(Source:  Amended at 47 Ill. Reg. 4437, effective March 23, 2023)