Office of Water Office Science and Technology EPA 820-D- 14 -0 58 May 2014



# Draft Update of Human Health Ambient Water Quality Criteria:

Pentachlorobenzene
608

- 93 -5Office of Science and Technology
Office of Water U.S. Environmental Protection Agency Washington, DC 20460 

# Update of Human Health Ambient Water Quality Criteri

Pentachlorobenzene
608

- 93 -5

Draft EPA 820 -D- 14

- 058 May 2014



# a:Pentachlorobenzene 608

- 93 -5

Table of Contents

Introduction: Plan and Scope of Update

Problem Formulation Criteria Formulas- 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 Derivation- Analysis

Criteria Characterization 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 pentachlorobenzene, contained in this document, incorporate updated information regarding relative source contribution, body weight, drinking water intake, fish consumption rate, and

bioaccumulation. ·͋Μ̯χΊϭ͋ νΪϢι̽͋ ̽ΪΣχιΊ̼ϢχΊΪΣ ι͋̽Ϊ΢΢͋Σ͇̯χΊΪΣν ̯ι͋ Ί͇͋ΣχΊ͕Ί͇͋ ΊΣ E ́!͛ν

· Methodology for Deriving Ambient Water Quality Criteria for the Protection of Human Health (2000) ͛ (Ε΋E ́!΂ 2000) ̈́ Εζ͇̯χ͇͋ ̼Ϊ͇Θ Ϯ͋Ίͽ·χ and drinking water intake data are identified in E ́!͛ν ·EϳζΪνϢι͋ F̯̽χΪιν H̯Σ͇̼ΪΪΙ ́ 2011 E͇ΊχΊΪΣ͛ (Ε΋E ́!΂ 2011) ̈́ Α·͋ ̼ΊΪ̯̽̽Ϣ΢ϢΜ̯χΊΪΣ ͕̯̽χΪι ͇̯χ̯ Ίν Ϣζ͇̯χ͇͋ ϢνΊΣͽ E ́!͛ν EνχΊ΢̯χΊΪΣ  ́ιΪͽι̯΢ ͜Σχ͋ι͕̯̽͋ (E ́͜) ΋ϢΊχ͋ ΢Ϊ͇͋ΜΊΣͽ ζιΪͽι̯΢ (Ε΋E ́!΂ 2012a). The overall fish consumption rate and trophic level breakdowns are updated using E ́!͛ν ·EνχΊ΢̯χ͇͋ FΊν· ΪΣνϢ΢ζχΊΪΣ ·̯χ͋ν ͕Ϊι χ·͋ Ε ̈́΋ ̈́  ́ΪζϢΜ̯χΊΪΣ ̯Σ͇ ΋͋Μ͋̽χ͇͋ ΋Ϣ̼ζΪζϢΜ̯χΊΪΣν (NHANES 2003- 2010)͛ (Ε΋E ́!΂ 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 ̯χ ΊννϢ͋ ̈́ ͞Ρ̯χ͋ι θϢ̯ΜΊχΘ ̽ιΊχ͋ιΊ̯͟ ΢̯Θ ι͕͋͋ι χΪ Σ̯χΊΪΣ̯Μ Ϯ̯χ͋ι θϢ̯ΜΊχΘ ̽ιΊχ͋ιΊ̯ ι͋̽Ϊ΢΢͋Σ͇̯χΊΪΣν

issued under CWA § 304 ̈́ ͞Ρ̯χ͋ι θϢ̯ΜΊχΘ ̽ιΊχ͋ιΊ̯͟ ΢̯Θ ̯ΜνΪ ι͕͋͋ι χΪ Ϯ̯χ͋ι θϢ̯ΜΊχΘ ̽ιΊχ͋ιΊ̯ components of water quality standards adopted by states, territories, or authorized tribes
under CWA § 303.

1Pentachlorobenzene 608

- 93 -5

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. Nor 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 states, 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 requirements. 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 authorized tribes have the discretion to adopt, where appropriate, other scientifically ͇͕͋͋ΣνΊ̼Μ͋ Ϯ̯χ͋ι θϢ̯ΜΊχΘ ̽ιΊχ͋ιΊ̯ χ·̯χ ͇Ί͕͕͋ι ͕ιΪ΢ E ́!͛ν Σ̯χΊΪΣ̯Μ ̯΢̼Ί͋Σχ ι͋̽Ϊ΢΢͋Σ͇͇͋ ̽ιΊχ͋ιΊ̯

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 statements. 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, assessing 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 under CWA § 304. Unless expressly ΊΣ͇Ί̯̽χ͇͋ Ϊχ·͋ιϮΊν͋΂ ̯ΜΜ ι͕͋͋ι͋Σ̽͋ν χΪ ̽͞ιΊχ͋ιΊ̯΂͟ ͞Ϯ̯χ͋ι θϢ̯ΜΊχΘ ̽ιΊχ͋ιΊ̯΂͟ ̯͞΢̼Ί͋Σχ Ϯ̯χ͋ι θϢ̯ΜΊχΘ ̽ιΊχ͋ιΊ̯ (!ΡΆ) ι͋̽Ϊ΢΢͋Σ͇̯χΊΪΣν΂͟ Ϊι νΊ΢ΊΜ̯ι ϭ̯ιΊ̯Σχν χ·͋ι͋Ϊ͕΂ ̯ι͋ ι͕͋͋ι͋Σ̽͋ν χΪ Σ̯χΊΪΣ̯Μ ambient water quality criteria recommendations for human health.

Problem Fo rmulation

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. E ́!͛ν ·Fι̯΢͋ϮΪιΙ ͕Ϊι HϢ΢̯Σ H̯͋Μχ· ·ΊνΙ !νν͋νν΢͋Σχ χΪ ͜Σ͕Ϊι΢ D͋̽ΊνΊΪΣ ͱ̯ΙΊΣͽ͛ (Ε΋E ́!΂ 2012b).

2Pentachlorobenzene 608

- 93 -5

In the development of AWQC, EPA currently follows the deterministic assessment methodology outlined in E ́!͛ν · Methodology for Deriving Ambient Water Quality Criteria for the Protection of Human Health (2000) ͛ (Ε΋E ́!΂ 2000)΂ ·͋ι̯͕͋χ͋ι ΙΣΪϮΣ ̯ν χ·͋ 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 an 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. Other 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 first 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) ͜Σ ̽ΪΣνΊ͇͋ι̯χΊΪΣ Ϊ͕ χ·͋ !ͽ͋Σ̽Θ͛ν ͽΪ̯Μν Ϊ͕ ζΪΜΜϢχΊΪΣ ζι͋ϭ͋ΣχΊΪΣ΂ ̯΢̼Ί͋Σχ Ϯ̯χ͋ιν ν·ΪϢΜ͇ ΣΪχ ̼͋ 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).

3(Eq.1)

(Eq.2)

4 Where: AWQC = ambient water quality criteria

RfD = reference dose

RSC = relative source contribution BW = body weight DI = drinking water intake ∑

i=2 = summation of ϭ̯ΜϢ͋ν ͕Ϊι ̯θϢ̯χΊ̽ χιΪζ·Ί̽ Μ͋ϭ͋Μν (Αͫ) Ϯ·͋ι͋ χ·͋ Μ͋χχ͋ι ͞Ί͟ νχ̯Σ͇ν ͕Ϊι χ·͋
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

* 1000 μg/mg is used to convert the units of mass into micrograms from milligrams. Pentachlorobenzene 608

- 93 -5

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 × BW (kg) × 1000 μg/mg *

4 DI (L/d) + ∑ (F · Ί (Ιͽ / ͇) ∓ !F Ί (ͫ Ιͽ)) Ί 2

For consumption of organisms only:

AWQC (μg/L) = RfD (mg/kg·d) × RSC × BW (kg) × 1000 (μg/mg)*

∑ Ί 2 ( FC · Ί (Ιͽ / ͇) ∓ !F Ί (ͫ Ιͽ))

The follo wing 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 Ϯ͋Ίͽ·χ ͕Ϊι ̯͇ϢΜχν 21 Θ̯͋ιν Ϊ͕ ̯ͽ͋ ̯Σ͇ ΪΜ͇͋ι ̈́ Α·Ίν ι͋̽Ϊ΢΢͋Σ͇̯χΊΪΣ Ίν ͕ΪϢΣ͇ ΊΣ E ́!͛ν ·EϳζΪνϢι͋ F̯̽χΪιν H̯Σ͇̼ΪΪΙ ́ 2011 E͇ΊχΊΪΣ͛ ΊΣ ·̯ζχ͋ι 8 ̈́ ͜χ Ϯ̯ν ̼̯ν͇͋ ΪΣ data derived from the National Health and Nutrition 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).

4 4Pentachlorobenzene 608

- 93 -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 ζ͋ι̽͋ΣχΊΜ͋ ͕Ϊι ̯͇ϢΜχν (≥21 Θ̯͋ιν of age) (USEPA, 2011). Direct water is defined as water ingested directly as a beverage (from all sources); indirect water is defined as water added in the preparation of food or beverages, not including indirect consumption of bottled water. This recommended value Ίν ͕ΪϢΣ͇ ΊΣ E ́!͛ν ·EϳζΪνϢι͋ F̯̽χΪιν

H̯Σ͇̼ΪΪΙ ́ 2011 E͇ΊχΊΪΣ͛ in Table 3- 36. It replaces the drinking water intake standard of 2 L/day described in the 2000 Methodology which represented the 86 th percentile for adults 20 years ̯Σ͇ ΪΜ͇͋ι ΊΣ χ·͋ Ε΋ D͋ζ̯ιχ΢͋Σχ Ϊ͕ !ͽιΊ̽ϢΜχϢι͋͛ν 1994 -96 Continuing Survey of Food Intake b y Individuals (CSFII) analysis 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 population 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 Ε ̈́΋ ̈́ D͋ζ̯ιχ΢͋Σχ Ϊ͕ !ͽιΊ̽ϢΜχϢι͋͛ν (Ε΋D!͛ν) ΪΣχΊΣϢΊΣͽ ΋Ϣιϭ͋Θ Ϊ͕ FΪΪ͇ ͜Σχ̯Ι͋ ̼Θ ͜Σ͇ΊϭΊ͇Ϣ̯Μν (CSFII) 1994-96 data (USEPA, 2002a).

As recommended 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 ͇Ί͋χ̯ιΘ ͋ϳζΪνϢι͋ χΪ ͕Ίν· ̯χ ΢ϢΜχΊζΜ͋ χιΪζ·Ί̽ Μ͋ϭ͋Μν ̈́ !Σ Ϊιͽ̯ΣΊν΢͛ν χιΪζ·Ί̽ ζΪνΊχΊΪΣ ΊΣ χ·͋ ̯θϢ̯χΊ̽ 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 freshwater 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 χιΪζ·Ί̽ Μ͋ϭ͋Μ νζ͋̽Ί͕Ί̽ ͇̯χ̯ ν͋χ΂ χ·͋ ι̯χΊΪ Ϊ͕ χ·̯χ χιΪζ·Ί̽ Μ͋ϭ͋Μ͛ν 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 divided 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 (0.008 kg/day); TL3 = 9 grams/day (0.009 kg/day); and TL4 = 5

5Pentachlorobenzene 608

- 93 -5

gr ams/day (0.005 kg/day). These resulting trophic level FCRs are well within the confidence ΊΣχ͋ιϭ̯Μν ͕Ϊι ̯͋̽· Ϊ͕ χ·͋ χιΪζ·Ί̽ Μ͋ϭ͋Μ νζ͋̽Ί͕Ί̽ ͇ΊνχιΊ̼ϢχΊΪΣν͛ 90 th percentiles and add to the total of 22 grams/day (USEPA, 2014).

Bioaccumulation 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 ̼͞ΊΪ̯̽̽Ϣ΢ϢΜ̯χΊΪΣ͟ ι͕͋͋ιν χΪ χ·͋ Ϣζχ̯Ι͋ ̯Σ͇ ι͋χ͋ΣχΊΪΣ Ϊ͕ ̯ ̽·͋΢Ί̯̽Μ ̼Θ ̯Σ ̯θϢ̯χΊ̽ Ϊιͽ̯ΣΊν΢

from al Μ νϢιιΪϢΣ͇ΊΣͽ ΢͇͋Ί̯ (͋ ̈́ͽ ̈́΂ Ϯ̯χ͋ι΂ ͕ΪΪ͇΂ ν͇͋Ί΢͋Σχ) ̈́ Α·͋ χ͋ι΢ ̼͞ΊΪ̽ΪΣ̽͋Σχι̯χΊΪΣ͟ ι͕͋͋ιν χΪ the uptake and retention of a chemical by an aquatic organism from water only. For some 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 underestimate the extent of accumulation in aquatic biota for these chemicals. Accordin ͽΜΘ΂ E ́!͛ν ͽϢΊ͇͋ΜΊΣ͋ν presented in the 2000 Methodology emphasize the measurement or estimation of chemical bioaccumulation by aquatic organisms (USEPA, 2000).

Α·͋ ̼ΊΪ̯̽̽Ϣ΢ϢΜ̯χΊΪΣ ͕̯̽χΪιν (!F) ·̯ϭ͋ ̼͋͋Σ ͋νχΊ΢̯χ͇͋ ϢνΊΣͽ E ́!͛ν EνχΊ΢̯χΊΪΣ  ́ιΪͽι̯΢

Interface (E ́͜) ΋ϢΊχ͋ (Ε΋E ́!΂ 2012̯) ̈́ Α·͋ F!FTM ζιΪͽι̯΢ ϮΊχ·ΊΣ E ́͜ ΋ϢΊχ͋ estimates fish bioaccumulation factors using octanol-water partition coefficients (K OW ) and biotransformation 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 egestion, 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 pentachlorobenzene, BAFs have been estimated 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 pentachlorobenzene (log K OW = 5.17) are 19,630 L/kg, 28,470 L/kg, and 61,860 L/kg wet-weight, respectively. These estimated BAFs replace the bioconcentration factor (BCF) of 2,125 L/kg used in the 2002 criteria derivations, which was calculated from a measured steady-state bioconcentration study of bluegills and represented all trophic levels (USEPA, 1980).

6Pentachlorobenzene 608

- 93 -5

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 pentachlorobenzene is 8 × 10 – 4 mg/kg·day (0.0008 mg/kg·day) (USEPA, 1988).

The principle study by Linder et al. (1980) chosen to calculate the reference dose for pentachlorobenzene was based on liver and kidney toxicity as the critical effects in rats orally exposed to pentachlorobenzene. The study was a subchronic study with a LOAEL of 8.3 mg/kg·day. An uncertainty factor of 10000× was applied to account for interspecies extrapolation (10×), intraspecies variation (10×), subchronic to chronic study variation (10×), and extrapolation of the NOAEL based from the LOAEL (10×) (USEPA, 1988).

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 ̯ΜΜΪϮν ̯ ζ͋ι̽͋Σχ̯ͽ͋ Ϊ͕ χ·͋ ι͕͋͋ι͋Σ̽͋ ͇Ϊν͋͛ν ͋ϳζΪνϢι͋ χΪ ̼͋ ̯χχιΊ̼Ϣχ͇͋ χΪ ̯΢̼Ί͋Σχ Ϯ̯χ͋ι ̯Σ͇ 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 remainder 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 ͋ΣνϢι͋ χ·̯χ ̯Σ ΊΣ͇ΊϭΊ͇Ϣ̯Μ͛ν χΪχ̯Μ ͋ϳζΪνϢι͋ ͕ιΪ΢ ̯ΜΜ sources does not exceed 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.

͜Σ χ·͋ ̯̼ν͋Σ̽͋ Ϊ͕ ν̽Ί͋ΣχΊ͕Ί̽ ͇̯χ̯΂ χ·͋ ̯ζζΜΊ̯̽χΊΪΣ Ϊ͕ χ·͋ E ́!͛ν 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 not

7Pentachlorobenzene 608

- 93 -5

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

Previously, the AWQC for pentachlorobenzene 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 pentachlorobenzene 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 pentachlorobenzene. Criteria calculations are presented below. These updated pentachlorobenzene 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 health ambient water quality criteria for pentachlorobenzene

Component Value Source Input Characterization

RfD 0.0008 mg/kg·day USEPA,

1988 uncertainty factor = 10

, 000 (10 for interspecies extrapolation; 10 for intraspecies variation; 10 for subchronic to chronic study extrapolation; 10 for LOAEL to NOAEL extrapolation)

RSC 0.20 USEPA,

2000 default value

BW 80 kg USEPA,

2011 ΢̯͋Σ Ϯ͋Ίͽ·χ ͕Ϊι ̯͇ϢΜχν (≥21 Θ̯͋ιν Ϊ͕ ̯ͽ͋)

DI 3 L/day USEPA,

2011 90 th ζ͋ι̽͋ΣχΊΜ͋ ͕Ϊι ̯͇ϢΜχν (≥21 Θ̯͋ιν of age)

FCR TL2 0.00 8 kg/day USEPA

, 2014 90th percentile consumption rate for the U.S. adult population (≥21 Θ̯͋ιν of age) TL3 0.00 9 kg/day

TL4 0.00 5 kg/day

BAF TL2 19,630 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 28,470 L/kg

TL4 61,860 L/kg

For consumption of water and organisms:

8 AWQC (μg/L) = RfD (mg/kg·d) × RSC × BW (kg) × 1000 μg/mg

DI (L/d) + ∑ i=2 (F· Ί (Ιͽ ͇) ∓ !F Ί (ͫ /k ͽ))

= 0.000 8 mg /kg· d × 0.2 0 × 8 0 k g × 100 0 μg/mg

3 L/d + ((0.008 kg/d × 19,630 L/kg) + (0.009 kg/d × 28,470 L/kg) + (0.005 kg/d × 61,860 L/kg))

= 0. 01 8 μg/L (rounded to 0.02 μg/L because of significant figures)

4Pentachlorobenzene 608

- 93 -5

For consumption of organisms only:

AWQC (μg/L) = RfD (mg/kg·d) × RSC × BW (kg) × 1000 (μg/mg)

∑ Ί =2 (F· Ί (Ιͽ / ͇) ∓ !F Ί (ͫ / Ιͽ))

= 0.000 8 mg/kg· d × 0.2 0 × 8 0 k g × 100 0 μg/mg

(0.008 kg/d × 19,630 L/kg) + (0.009 kg/d × 28,470 L/kg) + (0.005 kg/d × 61,860 L/kg)

= 0. 01 8 μg/L (rounded to 0.02 μg/L because of significant figures)

The updated human health ambient water quality criteria for pentachlorobenzene are

0.02 μg/L (water and organism) and 0.02 μg/L (organism only) (Table 2). These updated criteria replace the previously published values (USEPA, 2002b ).

Table 2. Su ΢΢̯ιΘ Ϊ͕ E ́!͛ν ζι͋̽ΊΪϢνΜΘ ι͋̽Ϊ΢΢͋Σ͇͇͋ (2002 ) and updated (2014) human health ambient water quality criteria for pentachlorobenzene

2002 Human Health AWQC 2014 Human Health AWQC Water and Organism 1.4 μg/L 0.02 μg/L Organism Only 1.5 μg/L 0.02 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 pentachlorobenzene.

Criteria Characterization

The updated 2014 human health AWQC for pentachlorobenzene take into account current data on health effects and exposure input parameters, consistent with the 2000 Methodology. The updated 2014 human health AWQC for pentachlorobenzene are about two orders of magnitude lower t ·̯Σ E ́!͛ν ζι͋ϭΊΪϢνΜΘ ι͋̽Ϊ΢΢͋Σ͇͇͋ 2002 criteria; i.e. the waterand-organism criterion decreased from 1.4 to 0.02 μg/L and the organism-only criterion decreased from 1.5 to 0.02 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

E ́!͛ν updated AWQC assume a higher body weight compared to the previously recommended 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 health effects are not anticipated from a lifetime of exposure also increases.

9 4Pentachlorobenzene 608

- 93 -5

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 parameters 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 below which negative health effects are not anticipated from a lifetime of exposure decreases.

Fish Consumption Rate

The updated fish consumption rate is 22 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.

Bioaccumulation Factor

The updated AWQC rely on EPI Suite model-estimated BAFs rather than the previously recommended BCF of 2,125 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 19,630, 28,470, and 61,860 L/kg wet-weight, respectively. Assuming all other input parameters remain constant, the higher ratios of fish tissue concentrations to water concentrations of pentachlorobenzene by aquatic organisms result in lower AWQC. That is, as bioaccumulation or bioconcentration of a contaminant in fish and shellfish increases, 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. The utilization of a bioaccumulation factor rather than a bioconcentration factor better represents the amount of a contaminant accumulating in an Ϊιͽ̯ΣΊν΢ ̼̯͋̽Ϣν͋ Ίχ ̯̽̽ΪϢΣχν ΣΪχ ΪΣΜΘ ͕Ϊι χ·͋ Ϊιͽ̯ΣΊν΢͛ν ͋ϳζΪνϢι͋ χΪ χ·͋ ζΪΜΜϢχ̯Σχ ΊΣ χ 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 trophic 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 chain.

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, a

10Pentachlorobenzene 608

- 93 -5

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 decreases.

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 one 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 sitespecific 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 authorized 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 exist 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

 Pentachlorobenzene (CAS Number 608- 93

- 5)

 Benzene, pentachloro­

 QCB

 RCRA waste number U183

References

Linder, R., T. Scotti, J. Goldstein, K. McElroy and D. Walsh. 1980. Acute and subchronic toxicity of pentachlorobenzene. J. Environ. Pathol. Toxicol. 4: 183- 196.

11Pentachlorobenzene 608

- 93 -5

USEPA (U.S. Environmental Protection Agency). 1980. Ambient Water Quality Criteria for Chlorinated Benzenes. Office of Water. Washington, DC. EPA- 44 0-5- 80 -028. http://water.epa.gov/scitech/swguidance/standards/upload/2001_10_12_criteria_ambi entwqc_chloribenz80.pdf

.

USEPA (U.S. Environmental Protection Agency). 1988. Pentachlorobenzene (CASRN 608- 93 -5). Integrated Risk Information System . Retrieved 18 July 2013. http://www.epa.gov/iris/subst/0085.htm

.

USEPA (U.S. Environmental Protection Agency). 2000. Methodology for Deriving Ambient Water Quality Criteria for the Protection of Human Health. Office of Water. Washington, 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. Washington, DC. EPA-600-R- 09 -052F. http://www.epa.gov/ncea/efh/pdfs/efh-complete.pdf

.

USEPA (U.S. Environmental Protection Agency). 2012̯ ̈́ EνχΊ΢̯χΊΪΣ  ́ιΪͽι̯΢ν ͜Σχ͋ι͕̯̽͋ ΋ϢΊχ͋TM for Microsoft® Windows, v 4.10. United States Environmental Protection Agency, Washington, DC, USA. http://www.epa.gov/oppt/exposure/pubs/episuite.htm

.

USEPA (U.S. Environmental Protection Agency). 2012b. Framework for Human Health Risk Assessment to Inform Decision Making. Office of the Science Advisor. Washington, DC.

EPA- 601 -D- 12 -001. http://www.epa.gov/raf/files/framework-document-7- 13 -12.pdf

.

USEPA (U.S. Environmental Protection Agency). 2014. Estimated Fish Consumption Rates for the U.S. Population and Selected Subpopulations (NHANES 2003-2010). Office of Water. Washington, DC. EPA- 820 -R- 14

- 002.

12