Section 302.585  Procedures for Determining the Lake Michigan Basin Human Health Threshold Criterion (LMHHTC) and the Lake Michigan Basin Human Health Threshold Value (LMHHTV)

The LMHHTC or LMHHTV  is derived for all toxic substances from the most sensitive end point for which there exists a dosage or concentration below which no adverse effect or response is likely to occur.

a)         Minimum data requirements:

1)         Tier I.  The minimum data set sufficient to derive a Tier I LMHHTC shall include at least one epidemiological study or one animal study of greater than 90 days duration; or

2)         Tier II.  When the minimum data for deriving Tier I criteria are not available, a more limited database consisting of an animal study of greater than 28 days duration shall be used.

b)         Principles for development of Tier I criteria and Tier II values:

1)         The experimental exposure level representing the highest level tested at which no adverse effects were demonstrated (NOAEL) shall be used for calculation of a criterion or value.  In the absence of a NOAEL, a LOAEL shall be used if it is based on relatively mild and reversible effects;

2)         Uncertainty factors (UFs) shall be used to account for the uncertainties in predicting acceptable dose levels for the general human population based upon experimental animal data or limited human data:

A)        A UF of 10 shall be used when extrapolating from experimental results of studies on prolonged exposure to average healthy humans;

B)        A UF of 100 shall be used when extrapolating from results of long-term studies on experimental animals;

C)        A UF of up to 1000 shall be used when extrapolating from animal studies for which the exposure duration is less than chronic, but greater than subchronic;

D)        A UF of up to 3000 shall be used when extrapolating from animal studies for which the exposure duration is less than subchronic;

E)         An additional UF of between one and ten shall be used when deriving a criterion from a LOAEL.  The level of additional uncertainty applied shall depend upon the severity and the incidence of the observed adverse effect;

F)         An additional UF of between one and ten shall be applied when there are limited effects data or incomplete sub-acute or chronic toxicity data;

3)         The total uncertainty (SUM of the uncertainty factors) shall not exceed 10,000 for Tier I criterion and 30,000 for Tier II value; and

4)         All study results shall be converted to the standard unit for acceptable daily exposure of milligrams of toxicant per kilogram of body weight per day (mg/kg/day).  Doses shall be adjusted for continuous exposure.

c)         Tier I criteria and Tier II value derivation.

1)         Determining the Acceptable Daily Exposure (ADE)

ADE = test value / SUM of the  UFs from subsection (b)(2) of this Section

Where:

acceptable daily exposure is in milligrams toxicant per kilogram body weight per day (mg/kg/day)

2)         Determining the Lake Michigan Basin Human Health Threshold Criterion (LMHHTC) or the Lake Michigan Basin Human Health Threshold Value (LMHHTV)

LMHHTC or LMHHTV = ADE x BW x RSC  /  WC + [(FC_TL3 x  BAF_HHTL3) + (FC_TL4 x BAF_HHTL4)] 

Where:

(Source:  Added at 22 Ill. Reg. 1356, effective December 24, 1997)