Iowa Administrative Code › Agency 567 - Environmental Protection Commission › Title IX - Spills and Hazardous Conditions › Chapter 137 - Iowa Land Recycling Program and Response Action Standards › Rule 567-137.5 - Statewide Standards

Current through Register Vol. 47, No. 3, July 24, 2024
(1)
Purpose.
This rule defines the basis and procedure for
				establishing statewide standards for contaminants in groundwater, soil, and
				surface water. Statewide standards for groundwater and soil represent
				concentrations of contaminants in these media at which normal exposure via
				ingestion and dermal contact with soil is considered unlikely to pose a threat
				to human health. Statewide standards for surface water are based on protection
				of aquatic life and protection of human health. This rule also describes how
				air standards are to be addressed.
(2)
Scope.
Statewide
				standards described herein address what are considered to be the most likely,
				normal exposure situations. Statewide standards for groundwater address direct
				exposure via ingestion to individual contaminants in the media of concern only.
				Statewide standards for soil address direct exposure to individual contaminants
				via ingestion and dermal contact. In the event exposure to multiple
				contaminants may occur or exposure from more than one medium may occur,
				statewide standards alone may not be protective of human health; therefore,
				cumulative risk standards must be met in accordance with subrule 137.10(7). In
				addition, the department may deny the use of the statewide standards prescribed
				herein and require the use of site-specific standards based on site-specific
				conditions pursuant to subrule 137.6(10).
Examples of exposure concerns not anticipated by the
				  statewide standards might include, but are not limited to:
* Significant plant uptake of contaminants from soil or
				  groundwater;
* Contaminants entering drinking water lines from contact
				  with soil or groundwater;
* Ecological concerns, other than for surface water;
* Groundwater in a nonprotected groundwater source that is
				  used or likely to be used for drinking water or other use.
(3)
Establishment of risk-based
				contaminant concentrations.
a.
Risk-based concentration formula.
Risk-based contaminant
				concentrations for soil and groundwater, except lead, shall be computed using
				the following formula, where appropriate:
(Formula I)
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NOTE: When a risk-based concentration is computed for two
				  routes of exposure to the same medium (e.g., soil oral exposure and soil dermal
				  exposure), the composite risk-based concentration equals the multiple of the
				  risk-based concentration for each route of exposure divided by the sum of the
				  risk-based concentration for each route of exposure.
Where: C = Concentration of contaminant (soil: mg/kg, water:
				  mg/1)
RF = Risk factor
For protection from cancer health risks:
RF = TR - SF
Where: TR = Target cancer risk (unitless)
SF = Slope factor
				  [(mg/kg)/day]-1for a route of exposure; see
				  paragraph
"c "
for source.
For protection from noncancer health risks:
RF = THQ x RfD
Where: THQ = Target hazard quotient (unitless)
RfD = Reference dose (mg/kg)/day for a route of exposure; see
				  paragraph
"c"
for source.
AT = Averaging time (years); time over which exposure is
				  averaged and potential adverse effects may occur
Abs = Absorption factor (unitless); portion of exposed
				  contaminant absorbed by the body
ERc = Exposure rate by a child (soil: mg/day, water:
				  1/day)
EFC= Exposure frequency by a child
				  (days/year)
EDC= Exposure duration by a child
				  (years)
BWC= Body weight of exposed child
				  (kg)
ERa= Exposure rate by an adult (soil:
				  mg/day, water: 1/day)
EFa= Exposure frequency by an adult
				  (days/year)
EDa= Exposure duration by an adult
				  (years)
BWa= Body weight of exposed adult
				  (kg)
CF = Conversion factor: 106kg/mg
				  for soils; 1 (unitless) for water
b.
Carcinogenic classification of
				chemicals.
The potential carcinogenicity of chemicals will be based on
				the weight-of-evidence classification system utilized by the U.S. Environmental
				Protection Agency (EPA). Risk-based concentrations will be based on cancer
				health effects for individual chemicals that are classified as Group A or Group
				B. The risk-based concentration for an individual chemical will be based on
				noncancer health effects for chemicals that are classified as Group C, Group D
				or Group E. In the absence of such classification for a chemical, the Group D
				classification will be assumed. Noncancer risks for a Group A or Group B
				chemical will be included in the determination of cumulative noncancer risk in
				accordance with subrule 137.10(7), if a reference dose exists for that
				chemical. Cancer risk associated with a Group C chemical shall be included in
				the determination of cumulative cancer risk in accordance with subrule
				137.10(7), if a cancer slope factor exists for that chemical.
c.
Source of toxicity
				values.
EPA's Integrated Risk Information System (IRIS) shall be the
				primary source of information on toxicity factors (e.g., oral reference doses
				and oral slope factors), carcinogenic classification for chemicals, and the
				target organs. Such information that is not available on IRIS shall be obtained
				from other sources consistent with current EPA guidelines. The Iowa department
				of public health shall be consulted regarding toxicity values not available on
				IRIS. Absorption factors for dermal soil exposure shall be based on best
				available information, which will usually be obtained from EPA guidance
				documents.