Office of Water Office Science and Technology EPA 820 -D- 14

- 084 May 2014



# Draft Update of Human Health Ambient Water Quality Criteria:

2,4

- Dimethylphenol 105

- 67 -9EPA 820 -D- 14

- 08 4 May 2014



# Update of Human Health Ambient Water Quality Criteria:

2,4

- Dimethylphenol 105

- 67 -9

Draft

Office of Science and Technology Office of Water U.S. Environmental Protection Agency Washington, DC 2046 02,4

- Dimethylphenol 105

- 67 -9

1 Table of Contents

Introduction : Plan and Scope of Update
Problem Formulation
Criteria Formula s- Analysis Plan Exposure Factors Body Weight Drinking Water Intake Fish Consumption Rate
Bioaccumulation Factor Hazard Identification and Dose Response
Reference Dose
Relative Source Contribution
Criteria Derivatio n- Analysis
Criteria Characterizati on Chemical Name / Synonyms
References

Introduction: Plan and Scope of Update

Human health ambient water quality criteria (AWQC) are numeric values for pollutant concentrations in ambient waters that the U.S. Environmental Protection Agency (EPA) considers to be protective of human health. EPA periodically revises water quality criteria to ensure that they reflect the latest scientific knowledge. The current revisions of the criteria for 2,4

- dimethylphenol , contained in this document, incorporate updated information regarding relative source contribution, body weight, drinking water intake, fish consumption rate, and
bioaccumulation. Relative source contribution recommendations are identified in EPA’s

‘ Methodology for Deriving Ambient Water Quality Criteria for the Protection of Human Health (2000) ’ (USEPA, 2000). Updated body weight and drinking water intake data are identified in EPA’s ‘Exposure Factors Handbook: 2011 Edition’ (USEPA, 2011). The bioaccumulation factor data is updated using EPA’s Estimation Program Interface (EPI) Suite modeling program (USEPA, 2012a). The overall fis h consumption rate and trophic level breakdowns are updated using
EPA’s ‘Estimated Fish Consumption Rates for the U.S. Population and Selected Subpopulations (NHANES 2003

- 2010)’ (USEPA, 2014) . Unless otherwise specified, all sources of information
used in this update are from peer reviewed sources.

Note that the term "water quality criteria" can carry one of two possible meanings, depending on the section of the Clean Water Act ( CWA) associated with the particular criteria at issue. “Water quality criteria” may refer to national water quality criteria recommendations
issued under CWA § 304. “Water quality criteria” may also refer to water quality criteria components of water quali ty standards adopted by states, territories, or authorized tribes under CWA § 303.2,4

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2 National ambient water quality criteria recommendations for human health are issued by the EPA under CWA § 304. They are based on the latest scientific information on the

re lationship between the effects of a constituent concentration and human health. Protective assumptions are made regarding the potential human exposure intakes. These criteria do not
reflect consideration of non

- human health endpoints or economic impacts. N or do they reflect the technological feasibility of meeting the chemical concentrations in ambient water. National ambient water quality criteria recommendations for human health are not automatically incorporated into water quality standards adopted by st ates, territories, or authorized tribes. Rather, they provide scientific information to states, territories and authorized tribes to assist them in adopting ambient water quality criteria for human health in water quality standards that meet CWA requiremen ts. National ambient water quality criteria recommendations for human health are not regulations themselves and they do not impose legally binding requirements on EPA, states, territories, authorized tribes, or the public. States, territories, and
authoriz ed tribes have the discretion to adopt, where appropriate, other scientifically defensible water quality criteria that differ from EPA’s national ambient recommended criteria
for human health.

Ambient water quality criteria components of water quality standards are generally adopted by the states, territories, and authorized tribes themselves, under § 303(c)(2). (In certain circumstances EPA also may promulgate this type of criterion itself, pursuant to §303(c)(4)). State ambient water quality criteria for human health represent a quality of water that sufficiently protects human health to support a designated use of the state, territory, or authorized tribe. Such criteria may be expressed in terms of constituent concentrations, levels,

or narrative statemen ts. Once ambient water quality criteria for human health are adopted by a state, territory, or authorized tribe into their water quality standards, they provide a basis for controlling discharges or releases of pollutants, for developing permit limits, ass essing waters, and developing total maximum daily loads (TMDLs) for waters that do not meet the water quality standard. Ambient water quality criteria for human health have a regulatory impact once they have been adopted into water quality standards by the state, territory, or authorized tribe under § 303(c)(2) (or alternatively issued by EPA pursuant to § 303(c)(4)).

The water quality criteria at issue in this document are national ambient water quality
criteria recommendations for human health issued und er CWA § 304. Unless expressly indicated otherwise, all references to “criteria,” “water quality criteria,” “ambient water quality criteria (AWQC) recommendations,” or similar variants thereof, are references to national ambient water quality criteria reco mmendations for human health.

Problem Formulation

Problem formulation provides a strategic framework for water quality criteria development by focusing on the most relevant endpoints and increasing the transparency of the effects assessment process. The structure of this criteria document is consistent with U.S. EPA’s ‘Framework for Human Health Risk Assessment to Inform Decision Making’ (USEPA, 2012b).2,4

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3 In the development of AWQC, EPA currently follows the deterministic assessment methodology outlined in EPA’s ‘Methodology for Deriving Ambient Water Quality Criteria for the Protection of Human Health (2000)’ (USEPA, 2000), hereafter known as the 2000 Methodology. For pollutants that exhibit a threshold of exposure before deleterious effects occur, such as is the case for non

- carcinogens, the 2000 Methodology applies a relative source contribution (RSC) to determine the amount of the reference dose ( RfD ) apportioned to fish consumption (freshwater and estuarine species) and drinking water intake. The RSC value is applied to chemicals with a n RfD to ensure that exposure to these chemicals from drinking water and fish ingestion, when combined with all other sources, will not exceed the reference
dose. O ther exposures routes

, including but not limited to, dermal exposure, inhalation exposure, marine fish and shellfish consumption (when not included in the fish consumption rate), and non

- fish dietary exposures (fruits, vegetables, grains, meats or poultry) are accounted for in the percentage of the RfD that remains, after accounting for the RSC.

Criteria Formulas - Analysis Plan

The following formulas are used to develop the human health ambient water quality

criteria. EPA develops criteria for ambient waters typically considering two routes of exposure

. The f irst formula is for a criterion that assumes exposure through both the consumption of water and the consumption of aquatic organisms. The second formula is for a criterion that assumes exposure through the consumption of aquatic organisms, but not water. The use of

one criteri on over the other depends on the designated use of the water bodies in question (i.e. drinking water source and/or fishable waters)

.

EPA recommends inclusion of the drinking water exposure pathway for ambient surface
waters where drinking water is a designated use for the following reasons: (1) Drinking water is a designated use for surface waters under the CWA and, therefore, criteria are needed to assure that this designated use can be protected and maintained. (2) Although rare, there are some public water supplies that provide drinking water from surface water sources without treatment. (3) Even among the majority of water supplies that do treat surface waters, existing treatments may not necessarily be effective for reducing levels of particular contaminants. (4) In consideration of the Agency’s goals of pollution prevention, ambient waters should not be contaminated to a level where the burden of achieving health objectives is shifted away from those responsible for pollutant discharges and placed on downstream users to bear the costs of upgraded or supplemental water treatment (USEPA, 2000).

EPA recommends the organism only criterion in those cases where the designated uses of a water body include only supporting fishable uses under Section 101(a) of the CWA and, thus, fish or shellfish for human consumption, but not as a drinking water supply source (e.g.,

non

- potable estuarine waters) (USEPA, 2000).2,4

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4 The formulas for deriving the criteria values are as follows (USEPA, 2000 ):

For consumption of water and organisms:

AWQC (μg/L) = RfD (mg/kg·d) × RSC × B W (kg) × 1000 μg/mg * DI (L/d) + (FCR i (kg/d) × BAF i (L/kg)) 4 i=2 (Eq. 1) ∑

For consumption of organisms only:

AWQC (μg/L) = RfD (mg/kg·d) × RSC × BW (kg) × 1000 (μg/mg) * (FCR i (kg/d) × BAF i (L/kg)) 4 i=2 (Eq. 2) ∑

Where:
AWQC = ambient water quality criteria
RfD = reference dose
RSC = relative source contribution BW = body weight DI = drinking water intake ∑ 4

i=2 = summation of values for aquatic trophic levels (TL) where the letter “i” stands for the trophic levels to be considered, starting with TL 2 and proceeding to TL 4

FCR i = fish consumption rate for aquatic trophic levels 2, 3, and 4

BAF i = bioaccumulation factor for aquatic trophic levels 2, 3, and 4

The following sections identify each of the components of the formulas for the human health ambient water quality criteria and provide reference sources, previously used values when available, and the values to be used in the updated criteria.

Exposure Factors:

Body Weight

The updated recommended body weight (BW) is 80 kg which represents the mean weight for adults 21 years of age and older. This recommendation is found in EPA’s ‘Exposure Factors Handbook: 2011 Edition’ in Chapter 8. It was based on data derived from the National
Health and Nutri tion Examination Survey (NHANES) 1999

− 2006 (USEPA, 2011). This body weight replaces the recommended standard weight for adults of 70 kg that was described in the 2000 Methodology which was approximated from the mean body weight of adults from the
National Health and Nutrition Examination Survey (NHANES) III database (1988

- 1994) and a 1989 study by the National Cancer Institute (USEPA, 2000).

* 1000 μg/mg is used to convert the units of mass into micrograms from milligrams.2,4

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5 Drinking Water Intake

The updated drinking water intake (DI) is 3 L/day, rounded from 3.091 L/day for

consumer

- only estimates of direct and indirect water ingestion based on NHANES 2003

- 2006
data for all sources of water at the 90 th percentile for adults (≥21 years o f age) (USEPA, 2011)

. Direct water is defined as water ingested directly as a beverage (fro m all sources) ; indirect water is defined as water added in the preparation of food or beverages, not including indirect consumption of bottled water. This recommend ed value is found in EPA’s ‘Exposure Factors
Handbook: 2011 Edition’ in Table 3

- 36. It repl aces the drinking water intake standard of 2 L/day described in the 2000 Methodology which represented the 86 th percentile for adults 20 years and older in the US Department of Agriculture’s 1994

- 96 Continuing Survey of Food Intake by Individuals (CSFII) a nalysis or the 88 th percentile of adults in the National Cancer Institute study
of the 1977

- 78 Nationwide Food Consumption Survey (USEPA, 2000).

Fish Consumption Rate

The updated fish consumption rate (FCR) for the general adult population is 22 grams/day (0.022 kg/day) (USEPA, 2014: see Table 9a ). It represents the 90 th percentile per capita consumption rate of freshwater and estuarine fish for the U.S. adult populatio n 21 years of age and older based on the Centers for Disease Control and Prevention (CDC) National Health and Nutrition Examination Surveys (NHANES) conducted from 2003

- 2010. It replaces the FCR default of 17.5 grams/day, which represented an estimate of the 90th percentile per capita consumption rate of freshwater and estuarine fish for the U.S. adult population based on the U.S. Department of Agriculture’s (USDA’s) Continuing Survey of Food Intake by Individuals (CSFII) 1994

- 96 data (USEPA, 2002a).

As r ecommended in the 2000 Methodology, this update to the criteria distinguishes a trophic level (TL) breakdown of the fish consumption rate to provide a better representation of dietary exposure to fish at multiple trophic levels. An organism’s trophic posit ion in the aquatic food web can have an important effect on the magnitude of bioaccumulation of certain chemicals. The trophic levels are numbered 2, 3, and 4 and account for different categories of fish and shellfish species based on their position in the aquatic food web. TL2 accounts for benthic filter feeders, TL3 accounts for forage fish, and TL4 accounts for predatory fish.

In order to derive the trophic level breakdown of the 22 grams/day freshwater and estuarine FCR, the trophic level specific fre shwater and estuarine FCR data sets for adults 21 years of age and older were identified (USEPA, 2014: see Tables 16a, 17a, and 18a ). In each trophic level specific data set, the ratio of that trophic level’s 90 th percentile FCR compared to the summation of all three trophic level specific 90 th percentile FCRs was applied to the 22 grams/day FCR used in this update. The trophic level ratios were calculated as follows: TL ratio

= 90 th percentile FCR for the TL divid ed by the sum of the 90 th percentile FCRs for all TLs. TL2 = 7.6/21.3 = 0.3568 (35.68%), TL3 = 8.6/21.3 = 0.4038 (40.38%), and TL4 = 5.1/21.3 = 0.2394 (23.94%). Applying these ratios to the updated FCR of 22 grams/day result in trophic level
breakdowns of TL2 = 8 grams/day (0.00 8 kg/day); TL3 = 9 grams/day (0.00 9 kg/day); and TL4 = 52,4

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6 grams/day (0.00 5 kg/day). These resulting trophic level FCRs are well within the confidence intervals for each of the trophic level specific distributions’ 90 th percentiles and add to the total of 22 grams/day (USEPA, 2014).

Bio accumul ation Factor

Several attributes of the bioaccumulation process are important to understand when deriving national BAFs for use in setting national 304(a) criteria. First, the term
“bioaccumulatio n” refers to the uptake and retention of a chemical by an aquatic organism
from all surrounding media (e.g., water, food, sediment). The term “bioconcentration” refers to
the uptake and retention of a chemical by an aquatic organism from water only. For so me chemicals (particularly those that are highly persistent and hydrophobic), the magnitude of
bioaccumulation by aquatic organisms can be substantially greater than the magnitude of bioconcentration. Thus, an assessment of bioconcentration alone may under estimate the
extent of accumulation in aquatic biota for these chemicals. Accordingly, EPA’s guidelines presented in the 2000 Methodology emphasize the measurement or estimation of chemical bioaccumulation by aquatic organisms (USEPA, 2000).

The bioaccumulation factors (BAF) have been estimated using EPA’s Estimation Program Interface (EPI) Suite (USEPA, 2012a). The BCFBAFTM program within EPI Suite estimates fish bioaccumulation factors using octanol

- water partition coefficients (K OW ) and biot ransformation data from a model designed by Arnot and Gobas (2003)

. The model includes mechanistic processes for bioaccumulation such as chemical uptake from the water at the gill surface and from the diet, chemical elimination at the gill surface, fecal e gestion, growth dilution and metabolic biotransformation. Other processes included in the calculations are bioavailability in the water column (only the freely dissolved fraction can bioconcentrate) and absorption efficiencies at the gill and in the gastrointestinal tract. The model requires the octanol

- water partition coefficient (K OW ) of the chemical and the normalized whole

- body metabolic biotransformation rate constant as input parameters to predict BAF values. Model predictions may be highly uncertain for chemicals that have estimated log K OW values > 9. The model is not recommended at this time for chemicals that appreciably ionize, for pigments and dyes, or for perfluorinated substances (USEPA, 2012a).

For 2,4

- dimethylphenol , BAFs have been estimate d using the EPI Suite model (USEPA, 2012a) as described above for trophic levels 2, 3, and 4. The estimated lower (TL2), mid (TL3), and upper (TL4) trophic level BAFs for 2,4

- dimethylphenol (log K OW = 2.30 ) are 9.984 L/kg, 10.67 L/kg, and 12.33 L/kg wet

- we ight, respectively. These estimated BAFs replace the bioconcentration factor (BCF) of 93.8 L/kg used in the 2002 criteria derivations, which was calculated from a steady

- state bioconcentration study of bluegills and represented all trophic levels (USEPA, 1 980).2,4

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7 Hazard Identification and Dose Response:

Reference Dose

The reference dose (RfD) is an estimate (with uncertainty spanning approximately an order of magnitude) of a daily oral exposure for a chronic duration (up to a lifetime) to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime. It can be derived from laboratory animal dosing studies
in which a no observed adverse effect level (NOAEL), lowest observed adverse effect level (LOAEL), or benchmark dose (with uncertainty factors generally applied to reflect limitations of the data used) can be obtained

. The RfD for 2,4

- dimethylphenol is 2 × 10 –2 mg/kg·day ( 0.02 mg/kg·day) ( USEPA, 1990 ).

The principle study by the EPA (USEPA, 1989) chosen to calculate the reference dose for 2,4

- dimethylphenol was based on lethargy, prostration, ataxia, and hematological changes as the critical effects in mice orally exposed to 2,4

- dimethylphenol . The study was a subchronic study with a NOAEL of 5.0 × 10 1 mg/kg·day. An uncertainty factor of 3000× was applied to account for interspecies extrapolation (10×), intraspecies variation (10×), and subchronic to chronic study extrapolation and database insufficiencies (30×) (USEPA, 1990).

Relative Source Contribution

The relative source contribution (RSC) component of the human health ambient water quality criteria (AWQC) calculation for threshold non

- carcinogens and non

- linear carcinogens allows a percentage of the reference dose’s exposure to be attributed to ambient water and freshwater and estuarine fish consumption (including estuarine species harvested in near coastal waters) when there are other potential exposure sources. The RSC describes the portion of the RfD available for AWQC

- related sources (often a 20% default is utilized ) (USEPA, 2000)

. The rem ainder of the RfD is allocated for other sources of the pollutant. The rationale for this approach is that for pollutants exhibiting threshold effects, the objective of the AWQC is to ensure that an individual’s total exposure from all sources does not exc eed that threshold level. Exposures outside of the RSC include, but are not limited to, exposure to a particular pollutant from marine fish consumption (not included in the fish consumption rate), non

- fish food consumption (fruits, vegetables, and grains), dermal exposure, and respiratory exposure. The percentage of exposure of the reference dose that these other exposures account for is equal to 100 percent minus the RSC.

In the absence of scientific data, the application of the EPA’s default value of 20 percent RSC in calculating 304(a) criteria or establishing State or Tribal water quality standards under Section 303(c) will ensure that the designated use for a water body is protected. This 20 percent default for RSC can only be replaced where sufficient data are available to develop a scientifically defensible alternative value. If appropriate

, scientific data demonstrating that other sources and routes of exposure besides water and freshwater/estuarine fish are not2,4

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8 anticipated for the pollutant in quest ion, then the RSC may be raised to the appropriate level,
based on the data ( USEPA, 2000)

.

Previously, the AWQC for 2,4

- dimethylphenol were calculated using a default RSC of 100 percent that does not comply with the 2000 Methodology. EPA recommends a RSC of 20 percent ( 0.20 ) for 2,4

- dimethylphenol as the default value.

Criteria Derivation - Analysis

Table 1 summarizes model inputs used to derive the 2014 updated human health ambient water quality criteria for 2,4

- dimethylphenol . Criteria calculations are presented below. These updated 2,4

- dimethylphenol criteria recommendations are based on the 2000 Methodology and updated exposure assumptions as described above (Exposure Factors).

Table 1. Summary of input parameters for 2014 human h ealth ambient water quality criteria for 2,4

- dimethylphenol

Component Value Source Input Characterization

RfD 0.02 mg/kg·day USEPA,

1990 uncertainty factor = 3000 (10 for interspecies extrapolation; 10 for intraspecies variation; 30 for subchronic to chronic study extrapolation and database insufficiencies)

RSC 0.20 USEPA,

2000 default value

BW 80 kg U SEPA,

2011 mean weight for adults (≥21 years o f age)

DI 3 L /day USEPA,

2011 90 th percentile for adults (≥21 years of age)

FCR TL2 0.00 8 kg/day USEPA

, 2014 90th percentile consumption rate for the U.S. adult population (≥21 years of age) TL3 0.009 k g/day

TL4 0.00 5 kg/day

BAF TL2 9.984 L/kg USEPA,

2012a EPI Suite K OW model estimated steady

- state BAF
values for non

- ionic organic chemicals in 3 general trophic levels of fish in temperate environments (10°C) TL3 10.67 L/kg

TL4 12.33 L /kg

For consumption of water and organisms:

AWQC (μg/L) = RfD (mg/kg·d) × RSC × B W (kg) × 1000 μg/mg DI (L/d) + (FCR i (kg/d) × BAF i (L/kg)) 4 i=2

= 0.02 mg/kg·d × 0.20 × 80 kg × 1000 μg/mg

3 L/d + ((0.00 8 kg/d × 9.984 L/kg) + ( 0.00 9 kg/d × 10.67 L/kg) + ( 0.00 5 kg/d × 12.33 L/kg))

= 98

. 840 μg/L (rounded to 100 μg/L because of significant figures) ∑2,4

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9 For consumption of organisms only:

AWQC (μg/L) = RfD (mg/kg·d) × RSC × BW (kg) × 1000 (μg/mg) (FCR i (kg/d) × BAF i (L/kg)) 4 i=2

= 0.02 mg/kg·d × 0.20 × 80 kg × 1000 μg/mg

( 0.00 8 kg/d × 9.984 L/kg) + ( 0.00 9 kg/d × 10.67 L/kg) + ( 0.00 5 kg/d × 12.33 L/kg)

= 1,347

. 073 μg/L (rounded to 1,000 μg/L because of significant figures) ∑

The updated human health ambient water quality criteria for 2,4

- dimethylphenol are

100 μg/L (water and organism) and 1,000 μg/L (organism only ) (Table 2). These updated criteria replace the previously published values ( USEPA, 2002b ).

Table 2. Summary of EPA’s preciously recommended (2002 ) and updated ( 2014 ) human health ambient water qu ality criteria for 2,4

- dimethylphenol

2002 Human Health AWQC 2014 Human Health AWQC Water and Organism 380 μg/L 100 μg/L Organism Only 850 μg/L 1,000 μg/L

These AWQC are meant to be protective of human health for the general adult population for a set percentage (RSC) of the total allowed daily oral exposure for a chronic duration (up to a lifetime ) of 2,4

- dimethylphenol

.

Criteria Characterization

The updated 2014 human health AWQC for 2,4

- dimethylphenol take into account current data on health effects and exposure input parameters, consistent with the 2000 Methodology. The updated 2014 human health AWQC for 2,4

- dimethylphenol are within an order of magnitude of EPA’s previously recommended 2002 criteria; i.e. the water

- and

organism criterion decreased from 380 to 100 μg/L and the organism

- only criterion increased
from 850 to 1,000 μg/L (Table 2). The following paragraphs describe the individual influence of each of the revised model inputs and exposure assumptions on the overall change in value.

Body Weight

EPA’s updated AWQC assume a higher body weight compared to the previously
recommende d 2002 criteria, reflecting a recent rise in average adult body weight among the U.S. population. The updated body weight assumption of 80 kg based on recent survey data
from the 1999

− 2006 NHANES data is 10 kg greater than the previous recommendation of 70 kg. Assuming all other input parameters remain constant, a higher average body weight in the AWQC calculations (Eq. 1 and 2 above) results in higher AWQC. That is, as body weight increases, the level of a contaminant in water at or below which negative he alth effects are not anticipated from a lifetime of exposure also increases.2,4

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10 Drinking Water Intake

The updated drinking water intake assumption is 3 L/day, which is higher than the previously recommended rate of 2 L/day. Assuming all other input paramet ers remain constant, a higher drinking water intake assumption in the AWQC calculations (Eq. 1 and 2 above) results in lower AWQC. That is, as drinking water intake increases, and thus overall exposure increases,
the level of a contaminant in water at or b elow which negative health effects are not anticipated from a lifetime of exposure decreases.

Fish Consumption Rate

The updated fish consumption rate is 2 2 g/day, divided into trophic level rates of 8 g/day, 9 g/day, and 5 g/day for trophic levels 2, 3, and 4, respectively, which is higher than the previously recommended rate of 17.5 g/day. Assuming all other input parameters remain constant, a higher fish consumption rate assumption in the AWQC calculations (Eq. 1 and 2
ab ove) results in lower AWQC. That is, as fish consumption increase, and thus overall exposure increases, the level of a contaminant in water at or below which negative health effects are not anticipated from a lifetime of exposure decreases.

Bioaccumulatio n Factor

The updated AWQC rely on EPI Suite model

- estimated BAFs rather than the previously
recommended BCF of 93.8 L/kg. The lower (TL2), mid (TL3), and upper (TL4) trophic level BAFs assumed in the updated criteria equations (Eq. 1 and 2 above) are 9.98 4, 10.67, and 12.33 L/kg

wet

- weight, respectively. Assuming all other input parameters remain constant, t he lower
ratios of fish tissue concentrations to water concentrations of 2,4

- dimethylphenol by aquatic organisms result in higher AWQC. That is, as bio accumulation or bioconcentration of a
contaminant in fish and shellfish decreases , and thus overall exposure decreases , the level of a contaminant in water at or below which negative health effects are not anticipated from a lifetime of exposure increases

. The utilization of a bioaccumulation factor rather than a bioconcentration factor better represents the amount of a contaminant accumulating in an organism because it accounts not only for the organism’s exposure to the pollutant in t he water column, but also from the food chain and surrounding environment as well as biotransformation of the pollutant in the organism due to metabolic processes. The utilization of the three trophic levels of fish and shellfish consumed, as opposed to representing all trophi c levels of fish and shellfish consumed by a single value, allows for better exposure representation, especially when pollutants bioaccumulate in significantly different amounts for organisms in different trophic levels at different positions in the food c hain.

Relative Source Contribution

The adoption of the recommended default RSC of 20 percent will be replacing the previous default of 100 percent. Assuming all other input parameters remain constant, a2,4

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11 smaller relative source contribution assumption in the AWQC calculations (Eq. 1 and 2 above) results in lower AWQC. That is, as the relative source contribution decreases, the level of a contaminant in water at or below which negative health effects are not anticipated from a lifetime of exposure decrease s.

Additional routes of exposure to a particular pollutant besides exposure from water intake and fish consumption are possible and may be considered when setting criteria for a state or tribe. Possible additional routes include, but are not limited to, dermal exposure, inhalation exposure, marine fish and shellfish consumption (when not included in the fish consumption rate), and non

- fish dietary exposures (fruits, vegetables, grains, meats or poultry).
If scientific evidence exists which indicate that on e or more of these routes pose a significant risk of exposure, states and authorized tribes are encouraged to ensure that subpopulations are adequately protected.

States, territories, and authorized tribes have the flexibility to develop criteria, on a si te

specific basis, that provide additional protection appropriate for highly exposed populations. EPA is aware that exposure patterns in general, and fish consumption in particular, vary substantially. EPA understands that highly exposed populations may be widely distributed geographically throughout a given state, territory, or authorized tribal area. EPA recommends that priority be given to identifying and adequately protecting the most highly exposed populations. Thus, if a state, territory, or authorize d tribe determines that a highly exposed population is at greater risk and would not be adequately protected by criteria based on the general population, and by the national 304(a) criteria in particular, the state, territory, or authorized tribe may adopt more stringent criteria using alternative exposure assumptions (USEPA, 2000). Subpopulations that may be considered include, but are not limited to, recreational fishers, subsistence fishers, women of childbearing age, and children. When
scientific data e xist showing one of these subpopulations is at risk of greater exposure to the pollutant or are biologically more sensitive, then the relevant inputs should be considered in setting criteria. This could entail raising the fish consumption rate to a level more reflective of the subpopulation based on collected data or adjusting the body weight and drinking water
intake.

Chemical Name / Synonyms

• 2,4

- dimethylphenol (CAS Number 105

- 67

- 9)

• Phenol, 2,4

- dimethyl -

• Caswell No. 907A

• EPA Pesticide Chemical Code 086804

• HSDB 4253

• m- xylenol

• NSC 3829

• RCRA waste number U101

• 1- hydroxy

- 2,4

- dimethylbenzene2,4

- Dimethylphenol 105

- 67 -9

12 • 2,4

- xylenol

• 4- hydroxy

- 1,3

- dimethylbenzene

• 4,6

- dimethylphenol

References

U SEPA (U.S. Environmental Protection Agency). 1980. Ambie nt Water Quality Criteria for 2,4

- dimethylphenol. Office of Water. Washington, DC. EPA

- 440 -5- 80

- 044. http://water.epa.gov/scitech /swguidance/standards/upload/2001_10_12_criteria_ambi entwqc_24dimethylphenol80.pdf

.

USEPA (U.S. Environmental Protection Agency). 1989. Ninety

- day gavage study in Albino mice using 2,4 - dimethylphenol. Study No. 410

- 2831, prepared by Dynamac Corporation, Rockville, MD, for the Office of Solid Waste and Emergency Response, Washington, DC.

USEPA (U.S. Environmental Protection Agency). 1990. 2,4

- Dimethylphenol (CASRN 105

- 67

- 9). Integrated Risk Information System . Retrieved 31 July 2013. http://www.epa.gov/iris/subst/0466.htm

.

USEPA (U.S. Environmental Protection Agency). 2000. Methodology for Deriving Ambient Water Quality Criteria for the Protection of Human Health. Office of Water. Washi ngton, DC.

EPA

- 822 -B- 00

- 004. http://water.epa.gov/scitech/swguidance/standards/upload/2005_05_06_criteria_hum anhealth_method_complete.pdf

.

USEPA (U.S. Environmental Protection Agency). 2002a. Estimated Per Capita Fish Consumption in the United States. Washington, DC. EPA

- 821 -C- 02

- 003. http://water.epa.gov/scitech/swguidance/standards/criteria/health/upload/consumpti on_report.pdf

.

USEPA (U.S. Environmental Protection Agency). 2002b. National Recommended Water Quality Criteria: 2002. Office of Water. Washington, DC. EPA

- 822 -R- 02

- 047. http://water.epa.gov/scitech/swguidance/standards/upload/2008_04_29_criteria_wqct able_nrwqc

- 2002.pdf

.

USEPA (U.S. Environmental Protection Agency). 2011. Exposure Factors Handbook: 2011 Edition. Office of Research and Development. Washing ton, DC. EPA

- 600 -R- 09

- 052F. http://www.epa.gov/ncea/efh/pdfs/efh

- complete.pdf

.

USEPA (U.S. Environmental Protection Agency). 2012a. Estimation Programs Interface SuiteTM for Microsoft® Windows, v 4.10. United States Environmental Protection Agency, Washington, DC, USA. http://www.epa.gov/oppt/exposure/pubs/episuite.htm

.2,4

- Dimethylphenol 105

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