Illinois Administrative Code › Title 35 - ENVIRONMENTAL PROTECTION › Part 620 - GROUNDWATER QUALITY › Subpart F - HEALTH ADVISORIES › Appendix A - Procedures for Determining Human Threshold Toxicant Advisory Concentration for Class I: Potable Resource Groundwater

Current through Register Vol. 48, No. 28, July 12, 2024
a) Calculating the Human Threshold Toxicant Advisory
				  Concentration
For those substances for which USEPA has not
				  adopted a Maximum Contaminant Level Goal (MCLG), the Human Threshold Toxicant
				  Advisory Concentration is calculated as follows:
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b) Procedures for Determining Acceptable Daily Exposures for
				  Class I: Potable Resource Groundwater
1) The Acceptable Daily Exposure (ADE) represents
				  the maximum amount of a threshold toxicant in milligrams per day (mg/d), which
				  if ingested daily for a lifetime results in no adverse effects to humans.
				  Subsections (b)(2) through (b)(6) list, in prescribed order, methods for
				  determining the ADE in Class I: Potable Resource Groundwater.
2) For those substances for which the USEPA has
				  derived a Verified Oral Reference Dose for humans, USEPA's Reference Dose given
				  in milligrams per kilogram per day (mg/kg/d), as determined in accordance with
				  methods provided in National Primary and Secondary Drinking Water Regulations,
				  40 CFR 136, appendix B, 40 CFR 141.80, 40 CFR 141.61, and 40 CFR 141.62,
				  incorporated by reference at Section 620.125, must be used. The ADE equals the
				  product of multiplying the Reference Dose by 70 kilograms (kg), which is the
				  assumed average weight of an adult human.
3) For those substances for which a no observed
				  adverse effect level for humans (NOAEL-H) exposed to the substance has been
				  derived, the ADE equals the product of multiplying one-tenth of the NOAEL-H
				  given in milligrams of toxicant per kilogram of body weight per day (mg/kg/d)
				  by the average weight of an adult human of 70 kilograms (kg). If two or more
				  studies are available, the lowest NOAEL-H must be used in the calculation of
				  the ADE.
4) For those substances for which only a lowest
				  observed adverse effect level for humans (LOAEL-H) exposed to the substance has
				  been derived, one-tenth the LOAEL-H must be substituted for the NOAEL-H in
				  subsection (b)(3).
5) For those substances for which a no observed
				  adverse effect level has been derived from studies of mammalian test species
				  (NOAEL-A) exposed to the substance, the ADE equals the product of multiplying
				  1/100 of the NOAEL-A given in milligrams toxicant per kilogram of test species
				  weight per day (mg/kg/d) by the average weight of an adult human of 70
				  kilograms (kg). Preference will be given to animal studies having High
				  Validity, as defined in subsection (c), in the order listed in that subsection.
				  Studies having a Medium Validity must be considered if no studies having High
				  Validity are available. If studies of Low Validity must be used, the ADE must
				  be calculated using 1/1000 of the NOAEL-A having Low Validity instead of 1/100
				  of the NOAEL-A of High or Medium Validity, except as described in subsection
				  (b)(6). If two or more studies among different animal species are equally
				  valid, the lowest NOAEL-A among animal species must be used in the calculation
				  of the ADE. Additional considerations in selecting the NOAEL-A include:
A) If the NOAEL-A is given in milligrams of
				  toxicant per liter of water consumed (mg/L), prior to calculating the ADE the
				  NOAEL-A must be multiplied by the average daily volume of water consumed by the
				  mammalian test species in liters per day (L/d) and divided by the average
				  weight of the mammalian test species in kilograms (kg).
B) If the NOAEL-A is given in milligrams of
				  toxicant per kilogram of food consumed (mg/kg), prior to calculating the ADE,
				  the NOAEL-A must be multiplied by the average amount in kilograms of food
				  consumed daily by the mammalian test species (kg/d) and divided by the average
				  weight of the mammalian test species in kilograms (kg).
C) If the mammalian test species was not exposed
				  to the toxicant each day of the test period, the NOAEL-A must be multiplied by
				  the ratio of days of exposure to the total days of the test period.
D) If more than one equally valid NOAEL-A is
				  available for the same mammalian test species, the best available data must be
				  used.
6) For those substances for which a NOAEL-A is not
				  available but the lowest observed adverse effect level (LOAEL-A) has been
				  derived from studies of mammalian test species exposed to the substance,
				  one-tenth of the LOAEL-A may be substituted for the NOAEL-A in subsection
				  (b)(5). The LOAEL-A must be selected in the same manner as that specified in
				  subsection (b)(5). One-tenth the LOAEL-A from a study determined to have Medium
				  Validity may be substituted for a NOAEL-A in subsection (b)(3) if the NOAEL-A
				  is from a study determined to have Low Validity, or if the toxicity endpoint
				  measured in the study having the LOAEL-A of Medium Validity is determined to be
				  more biologically relevant than the toxicity endpoint measured in the study
				  having the NOAEL-A of Low Validity.
c) Procedures for Establishing Validity of Data from Animal
				  Studies
1) High Validity Studies
A) High validity studies use a route of exposure
				  by ingestion or gavage, and are based upon:
i) Data from animal carcinogenicity studies with a
				  minimum of 2 dose levels and a control group, 2 species, both sexes, with 50
				  animals per dose per sex, and at least 50 percent survival at 15 months in mice
				  and 18 months in rats and at least 25 percent survival at 18 months in mice and
				  24 months in rats;
ii) Data from animal chronic studies with a
				  minimum of 3 dose levels and a control group, 2 species, both sexes, with 40
				  animals per dose per sex, and at least 50 percent survival at 15 months in mice
				  and 18 months in rats and at least 25 percent survival at 18 months in mice and
				  24 months in rats, and a well-defined NOAEL; or
iii) Data from animal subchronic studies with a
				  minimum of 3 dose levels and control, 2 species, both sexes, 4 animals per dose
				  per sex for non-rodent species or 10 animals per dose per sex for rodent
				  species, a duration of at least 5% of the test species' lifespan, and a
				  well-defined NOAEL.
B) Supporting studies which reinforce the
				  conclusions of a study of Medium Validity may be considered to raise such a
				  study to High Validity.
2) Medium Validity Studies
Medium validity studies are based upon:
A) Data from animal carcinogenicity, chronic, or
				  subchronic studies in which minor deviations from the study design elements
				  required for a High Validity Study are found, but which otherwise satisfy the
				  standards for a High Validity Study;
B) Data from animal carcinogenicity and chronic
				  studies in which at least 25 percent survival is reported at 15 months in mice
				  and 18 months in rats (a lesser survival is permitted at the conclusion of a
				  longer duration study, but the number of surviving animals should not fall
				  below 20 percent per dose per sex at 18 months for mice and 24 months for
				  rats), but which otherwise satisfy the standards for a High Validity
				  Study;
C) Data from animal subchronic or chronic studies
				  in which a Lowest Observable Adverse Effect Level (LOAEL) is determined, but
				  which otherwise satisfy the standards for a High Validity Study; or
D) Data from animal subchronic or chronic studies
				  which have an inappropriate route of exposure (for example, intraperitoneal
				  injection or inhalation) but which otherwise satisfy the standards for a High
				  Validity Study, with correction factors for conversion to the oral
				  route.
3) Low Validity Studies
Low validity studies are studies not meeting the
				  standards set forth in subsection (c)(1) or (c)(2).