UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

OFFICE OF 

PREVENTION, PESTICIDES AND 

TOXIC SUBSTANCES 

PC Code: 056502 

DP Barcode: 291271 

Date: March 22,2010 

MEMORANDUM 

Subject: 2008 Science Advisory Panel Meeting Follow Up: Assessment of the 

Bioaccumulation and Long-Range Transport Potential (LRTP) and of 

Pentachloronitrobenzene (PCNB) and Associated Ecological Risks 

To: Jill Bloom, Risk Manager Reviewer 

Pesticide Reregistration Division 

From: Kristina Garber, M.S., Biologist 

Environmental Risk Branch N 

Environmental Fate and Effects Division (7507P) 

Reviewed 

by: Thomas Steeger, Ph.D., Senior Biologist 

Cheryl Sutton, Ph.D., Environmental Sci 

R. David Jones, Ph.D. Senior Agronomist (f 

Environmental Risk Branch N 

Keith Sappington, M.S., Senior Biologist hdk sPfi .y4n (Tmr fi 33 . ?/, 

Environmental Risk Branch V 

Environmental Fate and Effects Division (7507P) 

Approved 

by: Elizabeth Behl, M.S., Branch Chief 

Environmental Risk Branch IV bM ~4 JCN) 7-23 -la 

Environmental Fate and Effects Division (7507P) 

Attached please find an assessment of the bioaccumulation potential of PCNB and its degradates, 

and contaminants and their associated ecological risks. Also included is an assessment of the 

long-range transport potential of PCNB and its degradates. PCNB and its degradates and 

contaminants are considered sufficiently persistent and likely to bioaccumulate in aquatic food 

chains to represent a chronic risk to mammals that consume aquatic organisms. In addition, 

PCNB is expected to move through long-range atmospheric transport to considerable distances 

from its site of application. Technical PCNB contains several contaminants, including 

hexachlorobenzene, polychlorinated dibenzodioxins and polychlorinated dibenzofurans, which 

are listed under the Stockholm Convention as Persistent Organic Pollutants (POPS). The weight 

of evidence suggests that PCNB, when considered with its residues and contaminants of concern, 

is a persistent, bioaccumulative, toxic chemical (PBT). 

Page 1 of 70 

TEXT SEARCHABLE DOCUMENT - 2010
Assessment of the Bioaccumulation and Long Range 

Transport Potential of Pentachloronitrobenzene 

(PCNB) 

and Associated Ecological Risks 

Prepared by: 

Kristina Garber, M.S., Biologist 

Contribution by: 

Faruque Khan, Ph.D., Senior Physical Scientist 

Reviewed by: 

Thomas Steeger, Ph.D., Senior Biologist 

Cheryl Sutton, Ph.D., Environmental Scientist 

R. David Jones, Ph.D. Senior Agronomist 

Keith Sappington, M.S., Senior Biologist 

Elizabeth Behl, M.S., Branch Chief 

U. S, Environmental Protection Agency 

Office of Pesticide Programs 

Environmental Fate and Effects Division 

Environmental Risk Branch IV 

1200 Pennsylvania Ave., NW 

Mail Code 7507P 

Washington, DC 20460 

March 22,2010 

Page 2 of 70 
Executive Summary 

The enviranmental fate and ecological risk assessment written in support of the Reregistration 

Eligibility Decision (RED) for PCNB (finalized in 2005) provided evidence that PCNB has the 

characteristics of a Persistent, Bioaccumulative and Toxic (PBT) chemical. The risk assessment 

also concluded that PCNB has the potential for long-range transport to non-target sites. In 

October 2008, the Environmental Fate and Ecological Effects Division (EFED) met with the 

Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) Scientific Advisory Panel (SAP) to 

discuss approaches for evaluating pesticides with attributes characterized as PBT (EPA, 2008). 

This assessment integrates available data on PCNB and its degradates in the context of 

recommendations from the SAP. 

The current assessment refines the previous conclusions relevant to the PBT characteristics of 

PCNB and its degradates. This is accomplished using the methods discussed during the 2008 

SAP meeting. Specifically, this assessment has 4 main objectives: 1) to investigate the impact of 

assumptions of the aquatic exposure model used by EPA (EXAMS) for persistent chemicals and 

the influence of those assumptions on estimated exposure and risk of PCNB; 2) to characterize 

the bioaccumulation potential of PCNB, its degradates, and its contaminants in aquatic systems 

and subsequent risks associated with each of these compounds; 3) to characterize the 

bioaccumulation potential of PCNB and its degradates in terrestrial systems and subsequent 

effects on risks; and 4) to investigate the long-range transport potential of PCNB and its 

degradates. 

The results of this assessment indicate that inclusion of pesticide burial, alteration of equilibrium 

partitioning of PCNB between aqueous and sorbed phases (on entering soil particles) and mass 

transfer between the water column and the benthic compartment using the EXAMS model do not 

alter the risk conclusions of EPAYs previous ecological risk assessment for PCNB. Therefore, 

consistent with the 2005 assessment, current uses of PCNB poses acute and chronic risk to 

freshwater fish and invertebrates, acute risk to estuarinelmarine invertebrates, and chronic risk to 

estuarinelmarine fish and invertebrates. 

This assessment investigated in greater detail the propensity for PCNB and its degradates to 

bioaccumulate in aquatic organisms. Using available bioconcentration data for PCNB and 

modeling results (KABAM), results indicate that PCNB and its degradates are likely to 

accumulate in tissues of aquatic organisms. Modeling further demonstrates that mammals 

consuming aquatic organisms have the potential to experience adverse effects due to chronic 

exposures to PCNB and its degradates in aquatic forage items from registered uses of PCNB on 

turf, cabbage, peanuts, cotton and potatoes. Use of PCNB on turf poses a risk of chronic effects 

to birds, amphibians and reptiles consuming aquatic organisms. 

Technical PCNB contains several contaminants, including hexachlorobenzene (HCB), 

polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzohrans (PCDFs), which are 

listed under the Stockholm Convention as Persistent Organic Pollutants (POPS). HCB, PCDDs 

and PCDFs are expected to bioaccumulate in aquatic systems to levels that pose risk of chronic 

effects to mammals consuming aquatic organisms. 

Page 3 of 70 
In previous ecological risk assessments of PCNB, bioaccumulation of PCNB and its degradates 

in terrestrial organisms was not considered. Based on the estimated octanol-air and ocjtanol-water 

partition coefficients for PCNB and its degradates, PCNB and its degradates have the potential to 

bioaccumulate in terrestrial ecosystems. Estimated concentrations of PCNB and its degradates in 

earthworms are two orders of magnitude higher than concentrations in soil, indicating that PCNB 

and its degradates can accumulate in soil-dwelling organisms inhabiting fields tfeated with 

PCNB. Available studies with terrestrial plants (i.e., crops) and animals indicate that PCNB is 

metabolized by terrestrial organisms; however, all metabolites that were identified were polychlorinated phenyl compounds, which are of toxicological concern. At this time, OPP has no tool 

available to assess bioaccumulation in terrestrial food webs (beyond earthworms). Thbrefore, the 

extent of bioaccumulation of PCNB in terrestrial ecosystems cannot be quantified by EFED at 

this time, and risks to terrestrial animals resulting from terrestrial bioaccumulation cannot be 

precluded. 

In addition to bioaccumulation, this assessment considers the ability of PCNB and its degradates 

to move to non-target sites via long-range transport. The volatility of PCNB coupled with its 

likely persistence in the atmosphere allow for potential long-range atmospheric transport of 

PCNB. Detections of PCNB in the atmosphere over areas in which the pesticide was not used 

provide evidence of the possibility for long-range transport. Modeling indicates that PCNB has 

comparable or higher long-range transport potential compared to chemicals that are known to 

move via this route of transport. 

Page 4 of 70 
Table of Contents 

1 . Introduction ................................................................................................................................. 3 

1 . 1. Purpose of Assessment ........................................................................................................ 3 

1.2. PCNB Use Characterization ............................................................................................... 3 

1.3. PCNB Residues of Concern ................................................................................................. 3 

1.4. Characterization of Environmental Persistence ................................................................... 3 

1.5. Characterization of Effects to Non-target Animals ............................................................. 3 

1.5.1. Aquatic Animals ........................................................................................................... 3 

1.5.2. Terrestrial Animals ...................................................................................................... 3 

1.6. Risk Conclusions from Ecological Risk Assessment Supporting RED ............................ 3 

2 . Accumulation of PCNB and its Degradates in Aquatic Systems ............................................... 3 

2.1. Consideration of Pesticide Burial in Aquatic Exposure Modeling ...................................... 3 

2.2. Equilibrium between Sediment and Water Column Concentrations ................................... 3 

2.3. Mass Transfer of Pesticide fiom Water into Sediment ........................................................ 3 

3 . Bioaccumulation of PCNB and its Degradates and Contaminants in Aquatic Organisms and 

Associated Ecological Risks ........................................................................................................... 3 

3.1. Bioconcentration Factors (BCFs) of PCNB and its Degradates .......................................... 3 

3.1 . 1. Estimated BCFs Using Modeling ................................................................................. 3 

3.1 .2 . Empirical BCFs ............................................................................................................. 3 

3.2. Metabolism of PCNB in Aquatic Organisms ....................................................................... 3 

3.3. PCNB Residues in Fish Tissues ........................................................................................... 3 

3.3.1. Monitoring Data ............................................................................................................ 3 

3.3.2. Estimated Concentrations of PCNB and its Degradates in Tissues of Aquatic 

Organisms ............................................................................................................................... 3 

3.3.3. Comparison of Field Measured and Estimated Concentrations of PCNB and its 

degradates in Fish Tissues ...................................................................................................... 3 

3.3.4. Estimated Concentrations of Contaminants in Tissues of Aquatic Organisms ............ 3 

3.4. Risks to Mammals, Birds, Terrestrial-phase Amphibians and Reptiles Consuming Aquatic 

Organisms ................................................................................................................................... 3 

3.4.1. Chronic Risks to Mammals fiom PCNB and its Degradates ........................................ 3 

3.4.2. Chronic Risks to Mammals from Contaminants ........................................................... 3 

3.4.3. Chronic Risks to Birds, Terrestrial-phase Amphibians and Reptiles from PCNB and 

its Degradates .......................................................................................................................... 3 

3.4.4. Chronic Risks to Birds, Terrestrial-phase Amphibians and Reptiles from 

Contaminants .......................................................................................................................... 3 

4 . Bioaccumulation of PCNB and its Degradates in Terrestrial Organisms and Associated Risks 3 

4.1. Accumulation of PCNB and its Degradates in Soil ............................................................. 3 

4.2. Bioaccumulation Potential ................................................................................................... 3 

4.3. Metabolism of PCNB in Terrestrial Organisms .................................................................. 3 

4.4. Risks to Mammals, Birds, Terrestrial-phase Amphibians and Reptiles Consumidg 

Earthworms ............................................................................................................................... 3 

5 . Long Range Transport Potential (LRTP) of PCNB and its Degradates ..................................... 3 

5.1 . Volatilization Data ............................................................................................................... 3 

5.2. Monitoring Studies ............................................................................................................... 3 

5.3. Modeling Long-Range Transport Potential ......................................................................... 3 

Page 5 of 70 
6 . Summary and Conclusions ......................................................................................................... 3 

7 . References Cited ......................................................................................................................... 3 

Appendix A . Octanol-water Partitioning Coefficients of PCNB and its Degradates ..................... 3 

Appendix B . Open literature review summaries for bioconcentration studies involving PCNB ... 3 

Appendix C . Use of fugacity approach to estimate pesticide concentrations in earthworms 

located on treated fields .............................................................................................................. . 3 

Page 6 of 70 
1. Introduction 

1.1, Purpose of Assessment 

The environmental fate and ecological risk assessment written in support of the Reregistration 

Eligibility Decision (RED) for PCNB (finalized in 2005; DP Barcode D291276), provided 

evidence that PCNB has the characteristics of a Persistent, Bioaccumulative and Toxic (PBT) 

chemical. The risk assessment also concluded that PCNB has the potential for long-range 

transport to non-target sites. 

In October 2008, the Environmental Fate and Ecological Effects Division (EFED) of the U.S. 

Environmental Protection Agency's Office of Pesticide Programs (OPP) met with the Federal 

Insecticide, Fungicide and Rodenticide Act (FIFRA) Scientific Advisory Panel (SAP) to discuss 

current and proposed approaches for evaluating pesticides with attributes characterized as PBT. 

The background document provided to the SAP entitled "Methods for Assessing Ecological Risks 

of Pesticides with Persistent, Bioaccumulative and Toxic Characteristics" (USEPA 2008a), 

described current approaches and recent improvements to the tools, methods and data which 

have been used to evaluate the ecological risks of pesticides with PBT-like characteristics. EPA 

requested that the SAP provide input on whether the EPA's approaches to addressing PBT issues 

and its use of additional methods are consistent with the available science and are appropriate for 

further development and integration into the EPA's risk assessment process. Overall, the SAP 

agreed that the EPA identified many of the challenging issues related to ecological risk 

assessments of pesticides with PBT characteristics and long-range transport potential (LRTP). 

The SAP indicated that the refinements proposed in the White Paper represented "a leap 

forward" for the EPA and that EPA's proposed refinements are rooted in science. 

The purpose of this assessment is to further refine EPA's conclusions on the PBT characteristics 

of PCNB and its degradates that were made in the original ecological risk assessment written in 

support of the reregistration decision (DP Barcode D291276). This assessment uses the methods 

described in the EPA's white paper (USEPA 2008a), with consideration of the comments 

provided by the SAP and has 4 main objectivesl) to investigate the impact of assumptions of the 

aquatic exposure model used by EPA (EXAMS) for persistent chemicals and the influence of 

those assumptions on estimated exposure and risk of PCNB; 2) to characterize the 

bioaccumulation potential of PCNB, its degradates and its contaminants in aquatic ecosystems 

and subsequent risks associated with each of these components; 3) to characterize the 

bioaccumulation potential of PCNB and its degradates in terrestrial ecosystems and subsequent 

risks; and 4) to investigate the long range-transport potential of PCNB and its degradates. 

1.2. PCNB Use Characterization 

PCNB is a contact fungicide that provides preventative and residual protection against soil-borne 

diseases. The environmental fate and ecological risk assessment chapter written in support of the 

RED (DP Barcode D291276) for PCNB focused on the five major uses, i.e., turf, peanuts, cole 

crops (e.g. cabbage, broccoli), potatoes and cotton. At the time the assessment was written, these 

uses accounted for over 86% of the national usage of PCNB. 

Page 7 of 70 
The current assessment was developed based on maximum label application rates for PCNB use 

on turf, peanuts, cotton, potatoes and cabbage that were defined in the ecological risk assessment 

chapter for PCNB (DP Barcode D291276). Since the ecological risk assessment chapter was 

completed, the EPA determined that the majority of these uses were ineligible for reregistration. 

According to the RED, the only uses of PCNB that are eligible for reregistration include: cole 

crops (for control of clubroot), commercial production of flowering bulbs and seed treatments 

(USEPA 2006). 

1.3. PCNB Residues of Concern 

PCNB has several environmental degradates and contaminants ('present in technical PCNB) that 

are of toxicological concern. Degradates and contaminants are of toxicological concern when 

their structure includes a polychlorinated phenyl ring. 

Environmental degradates of PCNB that were identified in the environmental fate and ecological 

risk assessment chapter for the RED (DP Barcode D291276) include: 

pentachloroaniline (PCA), 

pentachlorothioanisole (PCTA), 

pentachlorobenzene (PCB; also present as a contaminant), 

pentachlorophenol (PCP), 

pentachlorothioanisole sulfoxide (PCTASO), and 

pentachlorothioanisole sulfone (PCTAS02). 

This assessment considers exposures and risks of PCNB and all of its environmental degradates 

that contain a polychlorinated phenyl ring; in other words, all of the degradates listed above. 

Available toxicity data for PCNB and its degradates are provided below. Based on environmental 

fate studies available at the time the environmental fate and ecological risk assessment chapter 

was written, three major degradates of PCNB were identified: PCA, PCTA and PCB (Figure 1). 

PCNB PCA PCTA PCB 

Figure 1. Structures of PCNB and its major environmental degradates. 

Technical PCNB contains several manufacturing impurities, which are termed "contaminants" in 

this assessment. These include hexachlorobenzene (HCB), PCB, polychlorinated dibebodioxins 

(PCDDs) and polychlorinated dibenzofurans (PCDFs). HCB, PCDDs and PCDFs ark currently 

listed under the Stockholm Convention as Persistent Organic Pollutants (POPS). In August 

2010, PCB, which is a degradate and a contaminant of PCNB, will also be listed as a POP. 

Page 8 of 70 
In EFEDYs environmental fate and ecological risk assessment chapter for PCNB, HCB and PCB 

were identified as contaminants. For HCB and PCB, the EPA allows a maximum of 500 ppm and 

100 ppm, respectively, in technical PCNB'. 

According to samples recently (2010) analyzed by the OPP Biological and Economic 

Assessment Division and historical data reported in the Canadian Reevaluation Decision for 

Quintozene (i.e., PCNB; Health Canada 2009), polychlorinated dibenzodioxins (PCDDs) and 

polychlorinated dibenzofurans (PCDFs) are present in technical grade PCNB (Table 1). An 

assessment of data previously submitted to the EPA had indicated that dioxins were expected to 

be below the EPA-specified Limits of Quantitation (USEPA 2004~). The reasons for the 

differences in residues measured by EPA in 2010 and Canada in 2009 are currently being 

explored by EPA. 

To roughly estimate potential environmental loading of PCDDs and PCDFs, the EPA estimate of 

national usage of PCNB from 1990-2000 is 1.825 million Ibs per year (DP Barcode D291276). 

Using the reported levels of contaminants in Table 1, this translates to an annual application of 

approximately between 0.5 and 4 Ibs of PCDDs and PCDFs. 

The contaminants PCDDs and PCDFs were not considered in the 2005 ecological risk 

assessment chapter for PCNB; however, in light of the occurrence in recent reports they are 

included in this assessment. Chemicals such as PCDD and PCDF are considered to be 

persistent, bioaccumulative and are not metabolized by mammals (Van Den Berg et al. 2006). In 

general, considering the Log &, values of PCDDs and PCDFs (Log &, range: 7.9-9.5) relative 

to those of PCNB and its degradates (5.0, see Appendix A for details on how this value was 

derived), these contaminants would be expected to bioaccumulate to a greater extent than PCNB 

and its degradates. Therefore, this assessment considers the bioaccurnulation of these 

contaminants in aquatic systems separately from PCNB and its degradates. 

1.4. Characterization of PCNB Environmental Persistence 

PCNB is characterized as stable to hydrolysis (MRIDs 40865301, 40972601) and 

photodegradation on soil (MRIDs 4 100480 1,4 17 1320 1). Available aqueous photolysis half-lives 

for PCNB were 1.1 (MRID 42336201) and 2.5 days (MRIDs 42606210, 42606202). Available 

' Personal communication with Jill Bloom. 

Page 9 of 70 
aerobic soil metabolism half-lives for PCNB combined with its degradates were 983 and 1052 

days (MRIDs 429 1 1902, 41 384501, 4173202, 421 12801). Anaerobic soil metabolism data yield 

a half-life of 334 days for PCNB combined with its degradates (MRIDs 41203602, 42094401, 

41 38430 1, 4 168600 1, 41 7 13202, 421 12802). Aquatic metabolism data for PCNB are not 

available. 

Based on available data, PCNB and its degradates, considered together, are considered likely to 

be persistent in the environment. Although the primary route of degradation for PCNB is 

through aqueous photolysis, the ideal conditions for this route of degradation (i.e., clear, shallow 

water) is limited under natural conditions because runoff water tends to be turbid and incident 

light in surface water bodies is attenuated with increasing depth of water. 

PCNB is a moderately volatile compound that can be expected to dissipate through volatilization. 

Volatilization was observed in the laboratory metabolism studies cited above; however the rate 

of volatilization in these studies would be expected to be different than that in the field. 

Therefore, volatilization was factored out of the metabolism studies by adding the volatilized 

residues back into the estimates of total residues. Volatilization of PCNB and its deigradates is 

expected to represent a relevant route of dissipation; however, the overall persistence of PCNB 

and its degradates in the air is unknown. 

1.5. Characterization of Effects to Non-target Animals 

1.5.1. Aquatic Animals 

On an acute exposure basis, PCNB and several of its degradates are considered highly toxic 

(defined as 100 5 LCs0 <lo00 pg1L) to freshwater fish and invertebrates and very highly toxic 

(defined as LC50 400 pglL) to estuarinelmarine invertebrates. 

Available acute toxicity data for fish and aquatic invertebrates exposed to PCNB and its 

degradates indicate that some of the degradates are of similar or greater toxicity to aquatic 

animals. Available 96-h LCSo values for 3 species of fish exposed to PCNB range 100-7900 

pg/L. LC50 values for PCA, PCB and PCP range 56-800 pg/L for seven species of fish (Table 

2). For aquatic invertebrates, ECso values range 12-770 pg/L for acute exposures to PCNB. 

Acute LCso values for aquatic invertebrates exposed to PCA, PCB and PCB are similar to PCNB, 

with LCso values ranging from 50 to 450 pg/L for these degradates (Table 2). 

Toxicity data were not available for acute exposures of aquatic animals to PCNB degradates 

PCTA, PCTASO, and PCTAS02. In order to characterize the relative toxicity of PCTA, 

PCTASO, PCTAS02 to PCNB and PCA, PCB and PCP, the predictive tool ECOSAR v. 0.99h 

was run to estimate 96-h LCs0 values for fish and aquatic invertebrates. ECOSAR estimates of 

acute toxicity indicate that PCTA may be of similar or greater toxicity compared to PCNB. 

ECOSAR estimates indicate that PCTASO and PCTASOz may be of lesser toxicity compared to 

PCNB. 

Page 10 of 70 
Table 2. Summary of 96-h LC50 (units in pg/L) estimates for fish as calculated by ECOSAR 

and measured in toxicitv tests. 

Toxicity data are available in the open literature involving exposures of aquatic animals to HCB 

and to PCDDs and PCDFs (identified using ECOTOX). These data are not discussed fhther in 

this assessment since effects of direct exposures of fish and aquatic invertebrates to HCB and 

PCDDs and PCDFs are not considered. 

1.5.2. Terrestrial Animals 

Mortality from acute exposures is not considered to be of concern in this risk assessment, since 

PCNB is practically non-toxic (defined as LD5~>2000 mag bw) to birds and mammals on an 

acute oral exposure basis (MRIDs 406 1800 1,40652602,40652603,4 1443 101). 

For chronic effects, the toxicity endpoint is the no observed adverse effect level (NOAEL) or the 

no observed adverse effect concentration (NOAEC). The most sensitive toxicity endpoints 

available from surrogate test species are used to estimate treatment-related effects on chronic 

assessment endpoints of impaired growth, survival and/or reproduction. Chronic toxicity data are 

available only for the parent compound; no data are available to define the chronic toxicity of 

PCNBYs degradates to birds and mammals. Therefore, it is assumed that the toxicity of the 

degradates to birds and mammals is equivalent to that of the parent PCNB based on the similarity 

in parentldegradate chemical structures and toxicity to aquatic vertebrates and invertebrates. 

Chronic toxicity data are available for Northern bobwhite quail (Colinus virgindanus) and 

mallard duck (Anas platyrhynchos) exposed to PCNB. In an avian reproduction study, adult 

mallard ducks exposed to dietary concentrations of PCNB as low as 1200 mag-diet (LOAEC) 

exhibited significantly lower body weights compared to controls. The resulting NOAEC for 

mallard ducks was 600 mag-diet (MRID 41332802). In an avian reproduction study with 

northern bobwhite quail, the LOAEC was also 1200 mglkg-diet, based on a decreased Survival of 

offspring (specifically, a reduction in the number of 14-d survivors as a perGentage of 

hatchlings). The resulting NOAEC for northern bobwhite quail was also 600 mglkg-dfet (MRID 

41332801). These data are used as a surrogate for non-target birds as well as terrespial-phase 

amphibians and reptiles; in the absence of data to the contrary, PCNB degradates are presumed 

to have similar toxicity to that of the parent compound. 

Page 1 1 of 70 
Chronic toxicity data are available for laboratory rats (Rattus norvegicus) exposed to PCNB. In a 

2-generation study with rats (MRID 4191 8701), decreased body weight was observed in parents 

and in offspring exposed to PCNB levels as low as 169 mgkg-bwlday (LOAEL). Decreased 

body weight gain was also observed at the LOAEL in parents. The resulting NOAEL for this 

study was 1.2 mglkg-bwlday (equivalent to a NOAEC of 24 mglkg-dietlday using standard FDA 

lab rat conversion); because of a lack of data to the contrary, PCNB degradates are presumed to 

have similar toxicity to that of the parent compound. 

Because PCNB has been demonstrated to contain residues of PCDDs and PCDFs, this 

assessment uses available data on the toxicity of these compounds to assess potential risks to 

birds and mammals. A great deal of research has been conducted to characterize the toxicities of 

PCDDs and PCDFs especially relative to each other, since these compounds are o$en present 

together in the environment. The EPA (USEPA 2008b) and the World Health Organi$ation (Van 

Den Berg et al. 1998 and 2006) have established toxicity equivalency factors (TEFs) for dioxins 

and dioxin-like compounds (including PCDFs and polychlorinatedbiphenyls) as they relate to 

mammals and to birds. The TEFs of the PCDDs and PCDFs that represent contaminants of 

technical PCNB are provided in Table 3. These TEFs are used to estimatepotential risks to 

mammals and birds exposed to PCDDs and PCDFs present in technical grade PCNB. 

Table 3. Toxicity equivalency factors (TEFs) for mammals and birds for dioxins and 

dioxin-like contaminants of technical PCNB (USEPA 2008b). 

I HxCDF 1 0.1 1 0.1 1 

I OCDF I 0.0003 1 0.0001 1 

'compared to 2,3,7,8-TCDD 

In the TEF approach, the toxicities of these chemicals are related to 2,3,7,8-tetrachlorodibenzo-pdioxin (TCDD). Chronic toxicity endpoints for mammals exposed to 2,3,7,8-TCDD have been 

identified by the USEPA Office of Water (OW) for the Great Lakes Water Quality Initiative 

Criteria for the Protection of Wildlife (USEPA 1995). OW defined a NOAEL of 0.001 ygkgbwlday (1x10-~ mgkg-bwlday) for reproductive effects to mammals exposed to 2,3,7,8-TCDD in 

food. This NOAEL was based on reduced fertility in first (fi) and second generation (fi) rats 

exposed to a LOAEL of 0.01 pglkg-bwlday (Murray et al. 1979). OW also identified several 

studies reporting toxicity data involving chronic exposures of birds to 2,3,7,8-~~~~i however, 

these data were not considered in this assessment because, in all of the studies, the birds were 

dosed via intraperitoneal injection, not through their diet. 

Page 12 of 70 
1.6. Risk Conclusions from OPP's previous PCNB Ecological Risk Assessment, 

supporting the RED 

The following risk conclusions are fiom the environmental fate and ecological risk assessment 

written in support of the PCNB RED in 2005(DP Barcode D291276). These conclusions are also 

summarized in Table 4. The ecological risk conclusions discussed in the RED did not consider 

risks from the contaminants associated with PCNB. 

Acute risk levels of concern (LOCs) were exceeded for freshwater aquatic animals. 

Chronic risk LOCs were exceeded for freshwater fish and invertebrates; chronic effects 

included reduced number of eggs produced and reductions in the number of young 

surviving. 

Based on acute-to-chronic ratios derived from freshwater studies, estimated NQAECs for 

estuarinelmarine invertebrates suggested that chronic risk was possible fiom the uses of 

PCNB modeled in the assessment. 

No data were available to characterize the effects of PCNB on aquatic or terrestrial 

plants; therefore, it was not possible to assess the risks of PCNB to plants. 

Screening-level models indicated that exposure of terrestrial animals to PCNB was likely 

through consumption of treated seed and foliar residues. However, the likelihood of 

acute mortality to birds and mammals was considered low given that PCNB is practically 

nontoxic to both birds and mammals on an acute exposure basis. 

Chronic LOCs were exceeded for birds and mammals following consumption of PCNBtreated seed and PCNB residues on forage items (on treated fields). 

Although OPP does not typically estimate risks to terrestrial invertebrates, available data 

suggested that PCNB is practically nontoxic to adult bees. 

Table 4. Summary of risk conclusions from ecological risk assessment for PCNB 

supporting the OPP RED (DP Barcode ~291276). 

I marine) 

Habitat 

Aquatic 

(freshwater, 

estuarine and 

I I Sediment -dwelling invertebrates 

Taxa 

Fish, amphibians 

Water column invertebrates 

Plants 

I Terrestrial 1 I no I Yes I 

Exceeds Acute 

Risk LOC'? 

Yes 

Yes 

unknown3 

Exceeds Chronic 

RisK LOC~? 

Yes 

Yes 

unknown3 

I Acute risk to listed species LOC exceeded if risk quotient (RQ)>0.05 for aquatic animals and >0.1 for terrestrial 

animals. 

2 Chronic risk LOC exceeded if RQ>l .O. 

3~nknown because no toxicity data are available with which to evaluate risk. 4 Animals feeding on foliage, insects and seeds located on the treated field. 

Birds, amphibians, reptiles4 

Plants 

Page 13 of 70 

no 

unknown3 

Yes 

unknown3 
2. Accumulation of PCNB and its Degradates in Aquatic Systems 

Based on available data, PCNB and its degradates, considered together, are considered likely to 

be persistent in the aquatic environment. Although the primary route of degradation for PCNB is 

through aqueous photolysis, the ideal conditions for this route of degradation (clear, shallow 

water) are limited under natural conditions as runoff water tends to be turbid and incident light in 

surface water bodies is attenuated with increasing depth of water. 

EFED uses the Pesticide Root Zone Model coupled with the Exposure Analysis Model System 

(PRZMIEXAMS) to estimate pesticide concentrations in aquatic ecosystems. PRZM simulates 

pesticide application, movement and transformation on an agricultural field and the resultant 

pesticide loadings to a receiving water body via runoff, erosion and spray drift. EXAMS 

simulates the fate of the pesticide and resulting concentrations in the water body. The standard 

scenario used for ecological pesticide assessments assumes application to a 10-hectare 

agricultural field that drains into an adjacent 1-hectare water body, 2-meters deep (20,000 m3 

volume) with no outlet. 

At the 2008 SAP meeting, the EPA discussed the OPP's standard pond scenario and its use in the 

EXAMS for modeling surface and pore (benthic) water concentrations of persistent pesticides. 

The SAP expressed concerns over EXAMS' lack of inclusion of sediment burial in its conceptual 

model, current model assumptions regarding pesticide dissociation from incoming sediments and 

model assumptions regarding pesticide mass transfer between the water column and benthic 

compartments of the standard pond. The following sections explore these three concerns and the 

influences of model assumptions on estimated concentrations and associated risks of PCNB and 

its degradates in aquatic systems. 

2.1. Consideration of Pesticide Burial in Aquatic Exposure Modeling 

OPP's standard pond scenario used with EXAMS does not include burial of pesticide mass 

within the benthic compartment. It is assumed that although sediment burial of sorbed chemicals 

may occur in some natural water bodies, sediment deposits may be re-exposed in natural systems 

as a result of hydrodynamic processes and by bioturbation caused by animals in the benthic 

compartment. Therefore, pesticide loss from an aquatic system due to sediment burial is not 

conservative because temporarily buried pesticide mass is expected to be re-exposed in many 

natural systems. 

The SAP commented that burial of PBT chemicals in sediment deposits could represent a major 

removal mechanism and must be taken into account, either explicitly or implicitly in risk 

estimation for these types of pesticides. EXAMS can be used to model loss of pesticide mass 

from the benthic compartment by using a first-order rate constant (USEPA 2004b). 

In the background document develop for the SAP (USEPA 2008a), EPA explored the( impact of 

the burial of pesticide-laden sediment on estimates of pesticide exposures in the water column 

and benthic area of a farm pond. EPA estimated a value for a first-order rate coefficient, based 

Page 14 of 70 
on the assumption that sediment burial is equal to the sediment residence timd. Sediment 

residence time in this case was estimated by dividing the average daily sediment inflow rate 

[mass per day] by the mass of the sediment in the benthic compartment. The daily sediment 

inflow rate was based on the Mississippi cotton modeling scenario because it represents a PRZM 

scenario with a high soil erosion rate and a high burial rate. The resulting half-life due to burial 

was 222 days. This half-life is expected to represent a higher benthic sediment burial rate than 

would be derived using other PRZM scenarios. 

To evaluate the impact of burial on PCNB estimates, OPP used the sediment residence time 

calculated above to estimate concentrations of PCNB and its degradates in water column and 

benthic zones of the OPP standard pond. Table 5 and Table 6 provide the original peak, 21-d and 

60-d EECs for PCNB in the water column and benthic compartments of the OPP standard pond 

as reported in the original Ecological Risk Assessment for PCNB (DP 291276), which used 

earlier versions of PRZM and EXAMS. These tables also include EECs calculated using the 

most current versions of PRZM (~3.12.2)~ EXAMS (v2.98.4.6) and the Pe shell (Pe5) with and 

without burial. In general, EECs generated for the original ecological risk assessment for PCNB 

are somewhat different compared to those generated using the most current versions of PRZM 

and EXAMS. This can be attributed to changes in the model versions (e.g., different method of 

applying curve number, incorporation of irrigation) as well as changes in the parameterization of 

the PRZM scenarios themselves (e.g., change in meteorological files, change in curve number, 

change in emergence date). Importantly, the impact of burial on concentrations estimated in the 

water column and the benthic layer (using the burial half-life, 222 d, in place of the benthic halflife of 2004) is relatively small, i.e., <lo%. 

Resulting RQs from EECs that incorporate sediment burial are provided in Table 7 - 

Table 9. None of the changes (revision of PRZM and EXAMS and consideration of burial) alter 

the risk conclusions of the previous ecological risk assessment for PCNB (DP 291276), i.e., that 

use of PCNB poses acute and chronic risk to freshwater fish and invertebrates, acute risk to 

estuarine/marine invertebrates, and chronic risk to estuarine/marine fish and invertebrates. 

Page 15 of 70 
Table 5. Surface water EECs for PCNB and its degradates. Values generated wit33 and 

without consideration of burial. 

Use I Pe4 shell* No burial ( Pe5 shell No burial 1 Pe5 shell with burial 

Peak EECs (pg/L) 

*From Table 9 of original ecological risk assessment for PCNB. 

Turf 

Cabbage 

Peanuts 

Cotton 

Potatoes 

Potatoes 

Table 6. Benthic EECs for PCNB and its degradates. Values generated with and without 

consideration of burial. 

259 

84 

97 

28 

22 

11 

- - 

1 Cabbage I 2 1 I 2 1 I 

21- d EECs (pg/L) 

60- d EECs (pg/L) 

Use 

1 Peanuts 1 34 I 28 1 27 1 

128 

98 

64 

25 

23 

Turf 

Cabbage 

Peanuts 

Cotton 

11 

Turf 

Cabbage 

Peanuts 

Cotton 

Potatoes 

Pe4 shell* No burial I Pe5 shell No burial I Pe5 shell with burial 

I Cotton I 12 I 14 I 13 I 

128 

98 

64 

25 

23 

11 

187 

5 6 

46 

20 

139 

3 6 

25 

14 

5.1 

Peak EECs (pg/L) 

Turf 

Potatoes 

Page 16 of 70 

110 

55 

3 7 

16 

79 

35 

22 

10 

5.7 

Turf 

Cabbage 

Peanuts 

Cotton 

Potatoes 

110 

55 

3 7 

15 

79 

35 

22 

10 

5.7 

108 

4.2 

21- d EECS (pg/L) 

*From Table 9 of original ecological risk assessment for PCNB. 

101 

20 

3 0 

12 

3.6 

57 

4.7 

Turf 

Cabbage 

Peanuts 

Cotton 

Potatoes 

55 

4.5 

53 

20 

26 

13 

4.2 

106 

21 

3 3 

12 

4.1 

5 1 

18 

25 

12 

4.0 

56 

2 1 

28 

13 

4.6 

54 

19 

27 

13 

4.4 
**From Table 9 of originalecological risk assessment for PCNB. 

Table 7. Acute RQs for freshwater fish and invertebrates based on peak EECs generated 

with and without consideration of sediment burial. 

Table 8. Acute RQs for estuarinelmarine fish and invertebrates based on peak EECs 

Use 

Turf 

Cabbage 

Peanuts 

Cotton 

Potatoes 

generated with and without consideration of sediment burial. 

*RQ exceeds acute listed-species LOC (0.05) 

1 No burial 1 No burial 1 wl burial 1 No burial I No burial 1 wl burial 

- 

I Turf I 0.03 I 0.02 1 0.02 1 21.6" 1 10.7" 1 10.7" 1 

Pe5 shell 

wl burial 

1.28" 

0.98" 

0.64' 

0.25" 

0.23" 

Fish (LCs0 = 100 pgL) (Invertebrates (ECS0 = $70 vg/L) 

Use 

I I I I 

Cabbane 0.01 0.01 0.01 7.00" 1 8-17" 1 8.17" 1 

Pe4 shell*" 

No burial 

2.59" 

0.84" 

0.97" 

0.28" 

0.22" 

Pe4 shell** 

No burial 

0.34" 

0.11" 

0.13" 

0.04 

0.03 

Fish (LCs0 = 7900 pglL) 

Pe4 shell** I Pe5 shell ( Pe5 shell 

Pe5 shell 

No burial 

1.28" 

0.98" 

0.64" 

0.25" 

0.23" 

I Potatoes 1 <0.01 1 c0.01 1 c0.01 1 1.83" 1 1.92" 1 1.92" 1 

Pe5 shell ' 

No burial , 

0.17" 

0.13" 

0.08" 

0.03 

0.03 

Peanuts 

I I 

*RQ exceeds acute listed-species LOC (0.05) 

**From Table 9 of original ecological risk assessment for PCNB. 

Pe5 shell 

wl burial 

0.17" 

0.13" 

0.08" 

0.03 

0.03 

0.01 

2~~s generated using 2 1 -d surface water EECs £kom Table 5. 

*RQ exceeds chronic LOC (1 .O) 

**From Table 9 of original ecological risk assessment for PCNB. 

Cotton 

Table 9. Chronic RQs for freshwater fish and invertebrates based on EECs generated with 

and without consideration of sediment burial. 

2.2. Equilibrium between Sediment and Water Column Concentrations 

0.01 

Use 

Turf 

Cabbage 

Peanuts 

Cotton 

Potatoes 

EXAMS takes into consideration the sorption and desorption of sediment-bound pesticide that 

enters the pond from the PRZM field. In EXAMS, desorption of pesticide mass is acqounted for 

on the simulation day of the runoff event that brings the sediment-bound pesticide mass into the 

pond. This is accomplished using the parameter called PRBEN, which distributes a fraction of 

the sediment-bound pesticide directly to the benthic compartment of the pond. The remaining 

<0.01 

Page 17 of 70 

0.0 1 

'RQS generated using 60-d surface water EECs from Table 5. 

8.08* ( 5.33" 1 5.33" 

<0.01 

Fish (NOAEC = 13 pg/L)' 

Pe4 shell** 

No burial 

10.7" 

2.8" 

1.9" 

1.1" 

0.4 

Invertebrates (NOAEC = 18 pg/L) 

<0.01 

Pe4 shell** 

No burial 

10.4" 

3.1" 

2.6" 

1.1" 

0.6 

2.33" 1 2.08" 1 2.08" 

Pe5 shell 

No burial 

6.1" 

2.7" 

1.7" 

0.8 

0.4 

Pe5 shell 

W/ burial 

6.1" 

2.7" 

1.7" 

0.8 

0.4 

Pe5 shell 

No burial 

6.1" 

3.1" 

2.1" 

0.9 

0.6 

Pe5 shell 

w/ burial 

6.1" 

3.1" 

2.1" 

0.8 

0.6 
fraction of the sediment-bound pesticide mass remains in the water column of $e pond to 

equilibrate. In the OPP standard pond, PRBEN is set to 0.5, "based on the observation that, in 

general, about 50% of sorbed chemical is usually labile and about 50% recalcitrant to rapid reequilibration in water" (USEPA 2004b). 

The organic carbon partition coefficient (Koc) of a chemical can be used to explore reasonable 

proportions of pesticide mass that would be expected to desorb from sediment to reach 

equilibrium within the water column (USEPA 2008a). The fraction of pesticide expected to be 

sorbed to 30 mg/L of suspended sediments in the water column (this is the assumed 

concentration of suspended sediments in the standard pond) will vary based on a compound's 

Koc. Using a Koc of 6470 Llkg-oc to represent of PCNB and its degradates, the fraction on solid 

would be less than 0.1 (see Figure 4.1 1 of USEPA 2008a). This indicates that an appropriate 

PRBEN value for PCNB and its degradates would be less than the default value of 0.5. Use of a 

PRBEN value <0.5 would result in an increase in peak EECs in the water column. Since the 

EECs from the standard pond (without alteration of PRBEN) are already sufficient to result in 

RQs that exceed acute risk LOCs for aquatic animals, use of a different PRBEN value would not 

change the conclusion that PCNB and its degradates pose risks to aquatic animals residing in the 

water column. 

2.3. Mass Transfer of Pesticide from Water into Sediment 

In EXAMS, the mass transfer coefficient (MTC) controls the rate of pesticide movement from 

the water column compartment into the sediment compartment of the OPP standard pond. The 

pesticide concentration in the water column should increase as MTC values decrease. 

Conversely, the sediment pore water and sediment concentrations should decrease as MTC 

values decrease. 

A sensitivity analysis was conducted to assess the impact of changes in the value of MTC on 

concentrations of PCNB and its degradates in the water column and sediment pore water. This 

sensitivity analysis was performed using MTC values ranging 3.0x10-~ to 3.0x10-~ m2/hr; the 

default value of the MTC in the OPP standard pond is 3x10-~ m2/hr. Results were generated 

using the most current versions of PRZM/EXAMS and the pe5 shell. Results indicate that the 

peak water column concentration is not particularly sensitive to orders of magnitude changes in 

the value of the MTC (Table 10). 

Table 10. Concentrations of PCNB and its degradates in the water column and pore water 

of the OPP standard pond with different mass transfer coefficient values. Results are based 

on PCNB use on turf. 

MTC Value (m2/hr) 

3x10~ 

3x10-~ * 

3x10-~ 

3x1 o-~ 

3x10-' 

*Default value 

Page 18 of 70 

Water Column EECs (@L) Benthic EECs (pore water? pg/L) 

60-d 

68 

5 3 

l9 - 

, 8.8 

5.3 

Peak 

80 

57 

19 

8.9 

5.3 

60-d 

68 

79 

98 

101 

102 

21-d 

79 

56 

19 

8.8 

5.3 

Peak 

118 

128 

129 

129 

129 

21-d 

86 

110 

119 1 

120 

120 
Acute RQs based on these concentrations are provided in Table 11. Regardless of the value of 

the MTC, acute RQs for freshwater fish and estuarinelmarine invertebrates exceed LOCs for 

acute risk to non-listed and listed species. Also, RQs for freshwater invertebrates exceed the 

acute risk to listed species LOC for all values of MTC. Therefore, changes in the value of the 

MTC do not alter the risk conclusions of the previous ecological risk assessment for PCNB (DP 

291276), i.e., that use of PCNB poses acute risk to freshwater fish and invertebrates, as well as 

estuarinelmarine invertebrates. 

Table 11. Acute RQs generated for different MTC values. RQs generated using Peak water 

column EECs from Table 10 (udL). v r 

When the MTC value increases, chronic EECs and associated RQs for fi-eshwater fish and 

invertebrates increase. When the MTC is decreased by an order of magnitude below the default 

value (from 3x1 oq5 t03x10-~ m2/hr), chronic water column EECs decrease by 22% for the 21-d 

EEC and 14% for the 60-d EEC (Table 10). Despite this decrease in exposure, RQs for 

freshwater fish and invertebrates exceed the chronic risk LOC of 1.0 (Table 12). Therefore, use 

of a different MTC value would not change the conclusion that chronic exposures to PCNB and 

its degradates pose a risk to aquatic animals residing in the water column. 

MTC value 

3x10" 

Table 12. Chronic RQs generated for different MTC values. RQs generated using, water 

Freshwater fish (LCs0 

= 100 pg/L) 

I 

*Default value 

1 RQ exceeds acute risk to non-listed species LOC (0.5) 2 RQ exceeds acute risk to listed species LOC (0.05) 

1.29"' 

column EECs from Table 11 (&I,). 

Page 19 of 70 

Freshwater invertebrate 

(ECso = 770 pg/L) 

0.17' 

MTC value 

3x10'~ 

3x10-* 

Estuarinelmarine invertebrate 

(ECSo = 12 pg/L) 

10.7S1>' 

Freshwater fish 

*Default value 

'RQS generated using 60-d surface water EECs. 

2~~s generated using 2 1 -d surface water EECs. 3 RQ exceeds chronic risk LOC (1.0) 

7.g3 

7.g3 

Freshwater invertebrate 

6.73 

6.73 

C)
3. Bioaccumulation of PCNB and its Degradates and Contaminants in Aquatic Oirganisms 

and Associated Ecological Risks 

The environmental fate and ecological risk assessment written in support of the Raregistration 

Eligibility Decision (RED) for PCNB provided evidence that PCNB and its degradates have 

potential to bioaccumulate in aquatic ecosystems and would therefore have the potential to pose 

risk to mammals and birds that consume aquatic animals. At the time the assessment was written, 

no tool was available to quantifl the risks to mammals and birds consuming aquatic aimals that 

have accumulated pesticide residues. 

Since the ecological risk assessment chapter was finalized, the KO, (Based) Aquatic 

Bioaccumulation Model (KABAM; version 1.0; USEPA 2009) was developed and has been 

implemented for risk assessment by OPP. KABAM estimates bioaccumulation of pesticides in 

aquatic ecosystems and subsequent exposure and risk to mammals and birds consuming aquatic 

organisms contaminated with the pesticide. Figure 2 depicts the food web of KABAM. 

At the October 2008 meeting with the FIFRA SAP, the OPP presented an approach of using 

multiple methods for assessing aquatic bioaccumulation (i.e., lab studies, field studies, 

mathematical models). The SAP suggested that such an approach should be based on modeling 

and rely upon lab or field data to verify model assumptions and/or make adjustments to model 

parameters. The SAP generally supported the use of food web bioaccumulation models for 

assessing bioaccumulation. 

This assessment follows the suggestion of the SAP to rely upon model estimates of 

bioaccurnulation and to supplement model estimates using available empirical data. This 

assessment use's KABAM to build upon previous conclusions that PCNB and its degradates may 

bioaccumulate in aquatic systems. Risks of PCNB and its degradates to mammals and birds that 

consume aquatic organisms are also assessed using KABAM. Available information from 

laboratory bioconcentration studies are used to validate estimated biocorrcentration. 

Bioaccumulation estimates of contaminants of technical PCNB are also assessed, along with 

their associated risks. 

Page 20 of 70 
Water column 

Medium fish 

Filter feeders 

Benthic invertebrates 

I Sediment I 

Figure 2. Conceptual model depicting movement (see arrows) of PCNB and its degradates 

from sediment and water to various trophic levels in an aquatic food chain (e.g., 

phytoplankton, zooplankton, fish) and to birds and mammals consuming aquatic 

organisms. Organisms also take up PCNB and its degradates from the water column. 

3.1. Bioconcentration Factors (BCFs) of PCNB and its Degradates 

3.1.1. Estimated BCFs Using Modeling 

KABAM was run to estimate BCFs for aquatic organisms accumulating PCNB and its 

degradates. The model used a logarithmic transformation of the octanol water partition 

coefficient (Log KO,) of 5.0 to represent the partitioning of PCNB and its degradates to aquatic 

organisms. The SAP recommended that KO, data are carefully reviewed before their use in 

bioaccumulation models and that a "best value" (not just an average value) be selected for use in 

modeling. They recommended that selection of the "best value" should consider uncefiainties in 

different measurement methods and chemical properties. Appendix A of this documelpt provides 

a characterization of available K,, data for PCNB and its degradates and describes haw the Log 

L, value of 5.0 was selected to represent PCNB and its degradates. 

Page 21 of 70 
In estimating BCFs, it is assumed that the concentration of dissolved oxygen in water is 5 mg/L 

and the water temperature is 15OC. The body characteristics of aquatic organisms in various 

trophic levels are consistent with the default values of KABAM ( 

Table 13). The resulting bioconcentration factors (BCFs) for the various aquatic trophic levels 

are depicted in Table 14. Estimated BCFs indicate that PCNB and its degradates are expected to 

bioconcentrate in aquatic organisms. 

Table 13. Characteristics of model aquatic organisms used to derive BCFs for PCNB and 

its degradates. Values are KABAM default assumptions for aquatic organisms in model 

ecosvstem. d 

Trophic Level 

phytoplankton 

benthic invertebrates 

filter feeders 

Wet Weight (kg) 

N/ A 

small fish 

medium fish 

Table 14. KABAM-estimated PCNB residue BCF values for aquatic organisms bised on 

total wei~ht. 

1 .OE-04 

[ large fish 

Lipid content 

2.0% 

zooplankton 

1 .OE-02 

1 .OE-01 

12.0% 

3.0% 

1 .OE+00 

. - . . . - . . - - - - - - 

Non-lipid organic 

matter content 

85.0% 

8.0% 

1 .OE-07 

4.0% 

4.0% 

Trophic Level 

Phytoplankton 

1 Filter Feeders 1 240 1 1 

Water content 

90.0% 

3 .O% 

2 1 .O% 

1 .OE-03 

4.0% 

BCF (ygtkg-NTV)/( yg/L) 

4801 

I 

76.0% 

2.0% 13.0% 

23.0% 

23.0% 

Benthic Invertebrates 

3.1.2. Empirical BCFs 

85.0% 

73.0% 

73 .O% 

23.0% 

Zoo~lankton 

36.53 

Small Fish 

Medium Fish 

Large Fish 

Registrants have submitted studies on bioconcentration involving bluegill sunfish (Lepomis 

macrochirus) exposed to PCNB (Guideline 850.1730). In addition, EFED used ECOTOX, a 

database of publically available scientific literature maintained by EPA's Office of Research and 

Development, to identify studies which are related to bioconcentration of PCNB in algae and in 

fish. These studies are described below, with reviews of the studies provided in Appendix B of 

this document. Reported BCFs of the laboratory studies along with values estimated using 

KABAM are available in Table 15. Modeled estimates of BCF were derived using KABAM and 

input values representing the study conditions (i.e., water temperature, fish body weights, 

dissolved oxygen, pesticide concentration in water). In cases where information was not 

provided in a study report to define relevant study conditions, default parameter vzllues were 

used. BCFs in Table 15 are different than values reported in Table 14, which are parameterized 

to represent the standard farm pond used by OPP for ecological risk assessments. 

73.0% 

342 1 

4699 

4699 

4806 

Page 22 of 70 
3.1.2.1. Registrant-Submitted Studies 

In a registrant-submitted bioconcentration study (MRIDs 4 120000 1 and 4 195 170 1 ), PCNB 

residues accumulated in bluegill sunfish exposed to 14c-pc~~, at a mean aqueous concentration 

of 0.88 pg/L (range of 0.47-1.2 pg/L) for 35 days. In this study, PCNB represented a small 

fraction (22% on average) of the total radioactive residues present in the treatment water, leading 

to uncertainty in the specific residues that the fish were exposed to during the study. The 

maximum BCF of the study, which was observed at day 35, was 1100 for total residues in whole 

fish tissues. The KABAM-predicted BCF (4806; Table 15) was 4.4X higher than the maximum 

BCF observed in this study. In this study, it appeared that PCNB residues in fish reached a 

plateau at day 28 (residues measured at days 28 and 35 were similar), indicating that steady state 

was likely reached in test organisms by day 28 of the study. Radioactive residues in fish tissues 

were predominantly composed of PCTA, indicating that PCNB was metabolized by fish to one 

of the PCNB's degradates of concern. At the end of the study's 21-day depuration period, 78- 

82% of the accumulated 14c residues were eliminated from the fish tissues, which corresponded 

to a total depuration rate constant of 0.0732 d". KABAM was used to estimate a total depuration 

constant of 0.125 d-I, which represents chemical loss through respiration, fecal elimination, and 

growth dilution, assuming that the loss through metabolism is 0. The similarity between the 

empirical and estimated total elimination rate constant supports the assumption that loss 

pathways of PCNB and its degradates can be represented by respiration, fecal elimination and 

growth dilution and that metabolism does not contribute significantly to the elimination of PCNB 

and its degradates from fish. 

In a second registrant-submitted bioconcentration study (MRIDs 40580202 and 43179301), 

PCNB residues accumulated in bluegill sunfish exposed to radiolabeled PCNB, at a mean 

aqueous concentration of 0.54 pg/L (range of 0.31-0.67 pg/L) for 28 days. The maximum BCF 

of the study, which was observed at Day 28, was 960X. The KABAM-predicted BCF (4806; 

Table 15) was 5.OX higher than the BCF observed in this study. At the end of the exposure 

period of the study, BCFs had not yet reached a plateau, suggesting that steady state was not 

reached in test organisms; however, given the results of the previously described registrantsubmitted study, it is likely that this study was close to reaching steady state. As with the 

previously described registrant-submitted study, PCNB residues in fish tissues were 

predominantly (in this case, >90% of residues in edible tissues) composed of PCTA. At the end 

of the 2 1 -day depuration period, 8 1-84% of the accumulated I4c residues were eliminated from 

the fish tissues, which corresponded to a total depuration rate constant of 0.0836 d". This 

depuration rate constant is similar to the one calculated for PCNB and its degradates (0.123 dm') 

using KABAM. This indicates that the KABAM estimation of depuration, without consideration 

of metabolism, is similar to what has been observed in the laboratory. 

3.1.2.2. Studies from the Public Literature (identified using 

ECOTOX) 

Several articles have reported the results of a bioconcentration study with green algae (Chlorella 

fusca) exposed to 50 pg/L radiolabeled PCNB (Geyer et al. 1984; Freitag et al. 1982 and 1984). 

After a 24-hour exposure period, I4c residues in algae and in water were measured, with 67% of 

total mass in algae and 38% in water. The resulting BCF was 3100, which is within a factor of 

Page 23 of 70 
1.5X of the KABAM-predicted BCF (4801 . Potential degradatiodmetabolism of PCNB is not h discussed in the articles; however, since ' C residues were measured, it was assumed that the 

reported BCFs are representative of total PCNB and its degradates. 

An additional study involving C, fusca reported by Korte (1978; one of the authors of Freitag et 

al. 1982 and 1984) included two BCFs resulting from I-d exposures of green algae to 49 pg/L 

14c-labeled PCNB. Values were reported on a dry weight basis as 14,000 and 22,000 (units: 

(pglkg-dw)/(pg/L)). Assuming that this species of green algae contains 1 g dry weight for every 

5 g wet weight (based on Geyer et al. 1984), these dry weight BCFs can be translated to wet 

weight BCF values of 2800 and 4400 (units: (&kg-ww)/(pg/L)), respectively. The BCF value 

estimated by KABAM for PCNB and its degradates in phytoplankton (4801) is within a factor of 

1.1-1.7 of the reported values (Table 15). Potential degradation/metabolism of PCNB is not 

discussed in the article; however, since 14c residues were measured, it was assumed that the 

reported BCFs are representative of total PCNB and its degradates. 

In a bioconcentration study with golden orfes (Leuciscus idus melanotus), five fish were exposed 

to 0.4 pg/L 14c-labeled PCNB for 3 days. The reported BCF was 1140 (Freitag et al. 1982 and 

1984). In a second study with golden orfes, conducted under similar conditions, the BCF was 

1 130 (Korte 1978). The KABAM-estimated BCF value for total PCNB and its degradates in fish 

(4806) is within a factor of 4.3X of the reported values for golden orfes (Table 15). Given that 

these studies were only conducted for 3 days, and given the observation of the studies with 

bluegill sunfish (MRIDs 41200001 and 4195 1701) that steady state was reached for bluegill 

sunfish in approximately 28 days, it is uncertain whether steady state was reached in the golden 

orfes. If steady state was not reached, the reported BCFs could underestiaate values 

representative of steady state conditions. Potential degradation of PCNB is not discussed in the 

articles; however, since 14c residues were measured, it was assumed that the reported BCFs are 

representative of PCNB and its degradates. 

In a bioconcentration study with rainbow trout (Oncorhynchus mykiss, formerly Salmo 

gairdneri), fish were exposed to 0.69 pg/L PCNB in a mixture that contained 17 other 

chloronitrobenzenes for 36 days. The BCF values for PCNB measured at 5, 12, 20, 28, and 36 

days ranged fiom 1 14 to 26 1, with an overall mean of 17 1 (standard deviation k89). The authors 

of this study reported that fish tissue concentrations of PCNB reached equilibrium within 5 days, 

but significant differences in BCFs were observed at different time periods (Niimi et al. 1989). 

The BCF value estimated by KABAM for PCNB and its degradates in fish (4806; Table 15) is 

within a factor of 6.3-14X of the reported values for rainbow trout. PCNB was not radiolabelled, 

but was quantified using gas chromatography. PCNB's degradates were not included as analytes, 

indicating that reported BCFs likely underestimate values representative of PCNB and its 

degradates. Additionally, there is considerable uncertainty regarding how other 

chloronitrobenzenes present in the study may have affected uptake and/or depuration of PCNB 

and its degradates. 

In another bioconcentration study with rainbow trout (Oliver and Niimi 1985), fish were exposed 

for different time intervals (7, 21, 35, 75 and 96 days) to a mixture of 18 chlorinated and 

brominated organic chemicals, including PCNB. Fish were exposed at either 0.0014 or 0.014 

pg/L PCNB. BCFs measured at the indicated time intervals ranged from 90 to 950 for PCNB. 

Page 24 of 70 
The KABAM estimated BCFs for total PCNB residues in fish were 8006 for the 0.0014 pg/L 

concentration and 7506 for the 0.014 pg/L concentration (Table 15; differences in BCF values 

can be attributed to different fish body weights and lipid contents). KABAM-estimated values 

deviated by factors of 8.4X to as much as 83X from the values reported in this study. As in the 

previously discussed study (Niimi et al. 1989), only PCNB parent was measured in this study, 

likely resulting in an underestimation of the BCF that would be representative of PCNB and its 

degradates. 

Several articles reported the results of a BCF study with wild-caught topmouth gudgeon 

(Pseudorasbora parva) (Kanazawa 1980; 1981a; 1981 b; 1983). In this study, 15-20 fish were 

exposed to 10-20 pg/L PCNB for 14 days, with a resulting BCF of 238 for PCNB. The 

KABAM-estimated BCF for PCNB and its degradates in fish (4565) is within a factor of 19X of 

the reported value for topmouth gudgeon. As with the studies with rainbow trout, only PCNB 

was measured in this study, likely resulting in an underestimation of the BCF that would be 

representative of PCNB and its degradates. 

3.1.2.3. Summary of comparison between empirical and estimated 

BCFs 

In cases where laboratory BCF studies included PCNB and its degradates, there is generally 

good agreement between empirical and estimated BCFs, where estimated values are within a 

factor of 1.1 to 5X of observed values. Differences between empirical and estimated BCFs may 

be attributed to several factors, including: 

1) A lack of steady-state in test organisms of laboratory studies, resulting in underestimated 

BCF values. 

2) A difference between the actual lipid content of test fish (which is generally not provided in 

BCF study reports) and the lipid content of the fish assumed for KABAM (4%). 

3) Inconsistency between the assigned Log &, value of PCNB and its degradate~ (5.0) and 

the actual partitioning of PCNB and its degradates in aquatic organisms, As noted in 

Appendix A, reported Log KO, values of PCNB range of 4.22-5.30 and estimated Log L, 

values of PCNBYs degradates are a broader range of 3.7-5.8. 

4) Several studies available in the scientific literature analyzed fish tissues for only PCNB. 

Thus the results likely underestimate BCFs associated with PCNB and its degradates. This 

is supported by observations associated with the two registrant-submitted BCF studies 

where the PCTA was identified as representing the majority of PCNB residues in fish. 

Page 25 of 70 
Table 15. Summary of reported and estimated (using KABAM) BCFs from studies submitted by registrants and available in 

Page 26 of 70 

the scientific literature. 

Korte 1978 

Freitag et al. 

1982 and 1984 

Kanazawa 

1980; 198 la; 

1981b; 1983 

Niimi et al. 

1989 

Oliver and 

Niimi 1985 

Oliver and 

Niimi 1985 

NA = not applicable 

1 Estimated using KARAM- Input parameters were as follows. Log KO, = 5.0 and study parameter values for weight, 11p1d content, dissolved 02, temperature and PCNB concentration in water. All 

other parameters were set to KABAM defaults. In cases where data were not prov~ded in the study report (e.g , lipid content), KABAM default values were used 

2 The study report did not provide information on the lipid content of the test organisms. Therefore, the KABAM default was used in estirnattng BCF and the total elimination rate constant. 

3 The study report did not prov~de information on the dissolved oxygen concentration. Therefore, it was assumed that the test solutlon was at saturation. 

4 Calculated as. Est~mated + Emp~r~cal 

Golden 

orfe 

Golden 

orfe 

Topmouth 

gudgeon 

Rainbow 

trout 

Rainbow 

trout 

Rainbow 

trout 

3 

3 

3 0 

5-36 

7-96 

7-96 

3.5 

1.5 

3.5 

178 

237 

245 

42 

42 

42 

0.84 

7.2 

6.7 

83 

83 

83 

83 

83 

23 

22.5 

20 

15 

15 

15 

0.4 

0.4 

10-20 

0.69 

0.0014 

0.014 I 

1130 

1140 

23 8 

1 14-26 1 

380-950 

90-4 10 I 

4806 

4806 

4806 

1646 

8006 

7506 

4.3 

4.2 

20 

6.3-14 

8.4-21 

18-83 

Yes 

Yes 

No 

NO 

No 

No 
3.2. Metabolism of PCNB in Aquatic Organisms 

The SAP recommended that when data are not available from which to estimate chemical 

metabolism by biota, a rate of zero could be assumed. However, they cautioned that this can 

produce highly conservative estimates and suggested that EPA employ a recent approach by 

John Arnot for estimating metabolism as a step forward. 

In using KABAM with its default settings, it is assumed that the elimination of a pesticide from 

aquatic organisms through metabolism does not occur, i.e., the metabolism rate constant (kM) 

equals 0. In the case of PCNB, there is evidence from registrant-submitted BCF studies with 

bluegill sunfish that PCNB is metabolized by fish; however, PCNB is metabolized to PCTA, 

which has similar bioaccumulative properties (based on KO,) as the parent compound. 

When KABAM is used to predict BCFs for comparison to empirical values (Table 151, estimated 

values were within a factor of 1.1 to 5 of empirical BCFs that were based on PCNB and its 

degradates. When empirical BCFs were based on PCNB parent compound alone, KABAM 

predictions were much higher than the empirical values for PCNB alone (by factors rahging from 

6.3X to 83X). This indicates that KABAM predictions of bioconcentration are consistent with 

empirical studies involving total residues of PCNB. 

Depuration rate constants for PCNB and its degradates fkom registrant-submitted BlCF studies 

with bluegill sunfish were within a factor of 2 of predicted total depuration rate constants for 

PCNB and its degradates. This indicates that additional depuration caused by metabolism was 

not a significant process. Therefore, in this assessment, it is assumed that metabolism does not 

increase depuration of PCNB and its degradates. 

3.3. PCNB Residues in Fish Tissues 

3.3.1. Monitoring Data 

OPP has identified two monitoring studies that include data for PCNB concentrations in fish. In 

the first study, USEPA collected fish samples at 362 sites. PCNB was detected in 4 samples of 

fish, with all detections 40 &kg (USEPA 1992). 

In the second study, data on PCNB concentrations in fish are available from the National Lake 

Fish Tissue Study (NLFTS), which was the first survey of fish contamination in lakes and 

reservoirs in the 48 contiguous states based on a probability survay design 

(http://www.epa.aov/waterscience/fish/studv/, Stahl et al. 2009, and Olsen et al. 2009). This 

study included 268 of the chemicals with PBT properties, including PCNB. The USEPA 

implemented the study in cooperation with states, tribal nations, and other federal age~cies, with 

field collection occurring at 500 lakes and reservoirs over a four-year period (2000-2003). The 

sampled lakes and reservoirs were selected using a spatially balanced unequal probability survey 

design from 270,761 lake objects in USEPAys River Reach File Version 3 (RF3). In tqe NLFTS, 

there were a total of 1003 composite fish samples in the U.S. that were evaluated for 

these samples, 90 (9%) contained detectable levels of PCNB, with a concentratio 

Page 27 of 70 
0.766-5.54 pg/kg. PCNB was detected in fish samples collected throughout the 4-yew sampling 

period and throughout the continental US (including locations in: AL, AZ, CA, CO,FL, IL, IN, 

KS, ME, MI, MN, MS, MI, MT, NE, NV, NH, NJ, NY, OH, OK, OR, RI, TX, UT, VA, WAY 

WI, WY). Detections occurred in both predator and bottom-dwelling fish. 

These monitoring data likely underestimate PCNB's residues of concern because the monitoring 

studies focused only on PCNB; fish tissues were not analyzed for PCNBYs degradates. This is 

especially a concern given that the PCNB degradate PCTA has been identified as representing 

the majority of PCNB residues in the two registrant-submitted BCF studies with bluegill sunfish. 

Additionally, these monitoring data likely underestimate concentrations of PCNB since the fish 

sampled during this monitoring program were not targeted to coincide with either PCNB 

application areas (spatially) or application periods (temporally). As such, the residues measured 

in the fish samples likely underestimate residues in fish collected in close proximity to PCNB 

use sites. 

3.3.2. Estimated Concentrations of PCNB and its Degradates in Tissues of 

Aquatic Organisms 

The bioaccumulation of PCNB and its degradates in a freshwater aquatic ecosystem was 

estimated using KABAM in default mode (see user's guide for full description), with a Log KO, 

= 5.0 (see Appendix A) and a &, = 6470 L/kg-oc (DP Barcode D291276). Surface water 

column and benthic compartment (pore water) estimated environmental concentrations (EECs) 

were determined for PCNB use on turf, cabbage, peanuts, cotton and potatoes. Since KABAM 

assumes that aquatic organisms at steady state, it is necessary to enter surface water and benthic 

EECs that are representative of a steady state concentration of the chemical being modeled. The 

estimated time to steady state for PCNB (based on the Log Ed, of 5.0) is 30 days. This is 

supported by the observation that steady state was likely achieved within 28 days during a 

laboratory BCF studies with fish (MRIDs 4 120000 1 and 4 195 170 1). Therefore, the 1 -in- 10 year 

EEC averaging period used to represent the concentration of the pesticide in the sediment pore 

and surface waters of the aquatic habitat was selected as 21 days, which is the closest averaging 

period used by the PRZM/EXAMS to calculate aquatic EECs. For these different uses, sediment 

pore water, 21-d EECs were between 4.6 and 56 yg/L and surface water, 21-d EECs ranged 

between 1 1 and 1 10 pg/L (Table 16). 

Table 16.21-day pore water and surface water EECs (pg/L; 21-d values) of PCNB and its 

degradates generated by current version of PRZMIEXAMS. 

Use 1 Surface Water (pg/L) ) Sediment Pore Water (pg/L) 

I potatoes 1 11 I 4.6 I 

Turf 

Cabbage 

Peanuts 

Cnttnn 

Estimated concentrations of PCNB and its degradates in tissues of aquatic orgqnisms are 

provided in Table 17. Predicted concentrations of PCNB and its degradates in aquatic lorganisms 

range 28 to 1020 mgkg (wet weight), with values differing between trophic levels and for 

Page 28 of 70 

110 

55 

3 7 

16 

56 

2 1 

28 

13 
different PCNB uses. Concentrations of PCNB and its degradates in tissues of aquatic organisms 

(Table 17) are used to derive RQs based on dose-based and dietary-based exposures of 

mammals, birds, terrestrial-phase amphibians and reptiles consuming contaminated aquatic prey. 

Table 17. Estimated concentrations (mgkg-ww) of PCNB and its degradates in aquatic 

organism at different trophic levels based on different uses of PCNB. Values calculated 

using KABAM and 21-d EECs from PRZMIEXAMS. 

I Phytoplankton 1 500 1 250 1 168 1 73 1 50 1 

- 

Trophic Level 

According to the user's guide for KABAM, KO, is the input parameter that has the most 

influence on the predictions associated with bioaccumulation. As noted previously, a Log KO, of 

5.0 was used to represent PCNB and its degradates. A weight of evidence approach was used to 

determine the appropriate Log KO, to represent PCNB and its degradates (Appendix A); 

however, there is some uncertainty associated with the selected Log K,,, value. The first source 

of uncertainty is related to the available Log KO, values for PCNB, which range fiom 4.22 to 

5.30. Consideration of the range of Log KO, values available for PCNB indicates that predicted 

concentrations of PCNB and its degradates in aquatic organisms can vary by an order of 

magnitude (Table 18 and Table 19), with tissue concentrations increasing with KO,. The second 

source of uncertainty is associated with the assigned Log KO, value (5.0) used to represent 

PCNB and its degradates is the differences in partitioning of PCNB's degradates to each other 

and to PCNB. The major degradates of PCNB are PCA, PCTA and PCB; estimated Log KO, 

values are 4.30, 5.2 and 5.8, respectively (estimated using EPISuite v.4.0 (USEPA 2008~)). 

Although the estimated Log &, value for PCA is lower than 5.0, suggesting that predicted 

concentrations of PCNB and its degradates would be lower than predicted (Table 18 and Table 

19), the predicted value for PCA still falls within the range of empirical values available for 

PCNB. As described above, available BCF studies with fish indicate that PCNB is metabolized 

by fish to PCTA. Given that PCTA has a higher estimated Log KO, value than 5.0, it is possible 

that PCTA will depurate to a lesser extent than PCNB, once PCTA is formed. Therefore, PCNB 

and its degradates may be more likely to accumulate in aquatic organisms than predicted by the 

methods used in this assessment. 

Zooplankton 

Benthic Invertebrates 

Filter Feeders 

Small Fish 

Medium Fish 

Large Fish 

Page 29 of 70 

Turf 

(mglkg-ww) 

3 86 

425 

279 

627 

740 

1020 

Cabbage 

(mg/kg-ww) 

193 

21 1 

139 

3 12 

368 

510 

Peanuts 

(mglkg-ww) 

130 

145 

95 

213 

252 

346 

Cotton 

(mglkg-ww) 

Potatoes 

(mglkg-ww) 

56 

63 

4 1 

92 

109 

150 

3 9 

42 

28 

62 

74 

102 
Table 18. Predicted concentrations of PCNB and its degradates in aquatic organisms using 

different Log &, values to represent PCNB and its degradates. Values are based on PCNB 

"Values are used to generate RQs (Table 35 - Table 41). 

Phytoplankton 

Zooplankton 

Benthic Invertebrates 

Filter Feeders 

Small Fish 

Medium Fish 

Large Fish 

A major assumption associated with KABAM is that the model assumes that the chemical has 

reached steady state within aquatic organisms. Given the episodic nature of pesticide 

applications, sporadic peak exposures to aquatic organisms would be expected. The EEC used to 

represent the concentration of the pesticide in the pore and surface waters of the aquatic habitat is 

selected so that the averaging period (i.e., 4-d, 21-d, 60-d, 90-d, 1 year), is consistent with the 

time to steady state estimated for that chemical. Generally, the time to reach steady state can be 

related to the Log KO, of a chemical, with increasing time required as the Log &, increases. In 

the case of PCNB and its degradates, the estimated time to steady state is 30 days. This time to 

steady state is supported by a registrant-submitted BCF study with bluegill sunfish (MRIDs 

41200001 and 41 95 1701) where steady state was reached at approximately 28 days! Since the 

standard output file fiom PRZMIEXAMS does not include a 30-d average, the nCxt closest 

averaging period was selected (i.e., 21 days). The use of the 21-d average (1-in-10 yew) EEC to 

represent concentrations of PCNB and its degradates potentially results in overestimbtes of the 

steady state concentrations of PCNB and its degradates in tissues of aquatic organism . In order 

to account for uncertainty associated with the use of the 21-d average EEC to re resent the 

steady state concentration of PCNB residues in water, KABAM was run using 4 0-d EECs 

generated using the current versions of PRZWEXAMS (Table 20). The resulting eqtimates of 

85 

63 

67 

44 

89 

9 1 

99 

Table 19. Predicted concentrations of PCNB and its degradates in aquatic organisms using 

different Log Kow values to represent PCNB and its degradates. Values are based on 

PCNB use on potatoes (low end of EECs) and calculated using KABAM. 

Page 30 of 70 

Trophic Level 

Phytoplankton 

Zooplankton 

Benthic Invertebrates 

Filter Feeders 

Small Fish 

Medium Fish 

Large Fish 

500 

386 

425 

279 

627 

740 

1020 

972 

788 

89 1 

585 

1467 

1969 

3455 

*Values are used to generate RQs (Table 35 - Table 4 1). 

Log Km 

4.22 

(mg/kg-ww) 

9 

6 

7 

4 

9 

9 

10 

5.0" 

(mglkg-ww) 

50 

3 9 

42 

28 

62 

74 

102 

5.30 

(mglkg-ww) 

97 

79 

89 

58 

146 

196 

344 
PCNB and its degradates in aquatic organisms were lower (Table 21), but still on the same order 

of magnitude compared with tissue concentrations generated from the 2 1 -d EECs (Table 17). 

Table 20.60-day average sediment pore water and water column of PCNB and its 

degradates (generated by PRZMIEXAMS). 

Use 

Turf 

Cabbage 

Peanuts 

Cotton 

Potatoes 

The ecological risk assessment chapter developed in 2005 by OPP supporting the reregistration 

decision (DP Barcode D291276) described the potential for PCNB and its degradates to 

volatilize. The version of the PRZMIEXAMS model used to generate EECs for this lassessment 

is unable to account for volatilization; however, volatilization could be a significapt route of 

dissipation PCNB and its degradates when PCNB is not incorporated into the soil at the time of 

application. A provisional version of PRZMIEXAMS (PRZM9; dated November 10, 2004) 

which accounts for volatilization was used to evaluate the impact of this process oq estimated 

exposure. Results indicated that 21-day and 60-day EECs decrease due to volatilization by 

approximately 22% and 28%, respectively, for the turf use. If the 21-d EECs in both the surface 

water and sediment compartments (Table 16) are decreased by 22%, estimated conce~trations of 

PCNB and its degradates in aquatic organisms are lower (Table 22), but still approximately the 

same order of magnitude compared with pesticide residues generated from the 2 1 -d EECs where 

volatilization was not considered (Table 17). 

Table 21. 60-d average estimated concentrations of PCNB and its degradates in aquatic 

NB, 

Page 3 1 of 70 

Surface Water 

(PgW 

79 

35 

22 

10 

5.7 

Filter Feeders 

Small Fish 

Medium Fish 

Large Fish 

Sediment Pore Water 

(PdJ-4 

5 3 

20 

26 

13 

4.2 

202 

453 

536 

73 8 

89 

200 

236 

326 

5 8 

129 

153 

208 

26 

59 

70 

95 

15 

3 3 

39 

53 
Table 22. Estimated concentrations of PCNB and its degradates in aquatic organisms 

when considering surface water concentrations that account for vola~lization~ 

3.3.3. Comparison of Field Measured and Estimated Concentrations of 

PCNB and its degradates in Fish Tissues 

Estimated concentrations of PCNB and its degradates in fish range from 6.2 x lo4 pgkg to 1.0 x 

lo7 pglkg (Table 17). These estimates differ by several orders of magnitude when compared to 

measured concentrations of PCNB (only) in field-collected fish tissues (range of 0.766-5.54 

pgkg; see Section 3.3.1). These differences can be attributed to several factors, including: 

1) Monitoring studies analyzed fish tissues for PCNB only. Given that PCTA has been 

identified as representing the majority of PCNB residues (as much as 90%), it is likely that 

reported values for PCNB parent compound alone underestimate total PCNB residues of 

concern, which include PCNB and its degradates. 

2) Estimated concentrations of PCNB and its degradates are based on maximum use rates of 

PCNB as allowed by labels (considered current at the time the ecological risk assessment 

chapter for PCNB was written). Measured concentrations of PCNB in field collected fish 

may be representative of use rates that were lower than maximum rates defined by labels. 

3) Fish were not collected relative to temporal or spatial PCNB use. As such, residues in fish 

reported through this monitoring effort likely under-represent peak residues where fish 

habitat are adjacent to PCNB use sites. 

4) Surface water column and benthic sediment pore water EECs generated by PRZMIEXAMS 

are based on the assumption that 100% of the watershed, associated with the water body 

that represents the habitat of the aquatic food web (of KABAM), is treated with PCNB at 

the same time. Larger watersheds often are not represented by a homogenous land cover, 

but rather are represented by a mixture of different land covers. Not all of the land covers 

of a watershed are likely to be use sites of PCNB. Therefore, it is highly unlikely that 100% 

of the watersheds associated with the water bodies where fish were collected were treated 

at the same time with PCNB. Furthermore, locations within the watershed that are treated 

are probably not treated every year, as is assumed for the PRZMEXAMS simulations. 

5) Surface water column and benthic sediment pore water EECs generated by PRZMEXAMS 

are based on the assumption that the receiving water body is a pond with a static volume no 

outflow. This could lead to higher estimated concentrations of PCNB and its degradates 

compared to water bodies with outflows. 

Page 32 of 70 
3.3.4. Estimated Concentrations of Contaminants in Tissues of Aquatic 

Organisms 

The two contaminants HCB and PCB have estimated Log Lw values (5.86 and 5.22, 

respectively) that are similar to each other and to those of PCNB and its degradates. In contrast, 

the hw values of the PCDD and PCDF contaminants of technical PCNB are several orders of 

magnitude above PCNB and its degradates and its other contaminants(estimated Log L, values 

range 7.92 - 9.50) . Therefore, the bioaccumulation potentials of HCB and PCB are considered 

separately from the PCDD and PCDF contaminants. 

3.3.4.1. HCB and PCB 

The bioaccumulation of HCB and PCB (as contaminants of technical grade PCNB); in a 

freshwater aquatic ecosystem was estimated using KABAM run in default mode (see user's 

guide for hll description). This analysis does not account for bioaccumulation of PCB formed as 

a degradate of PCNB. The KO, and LC values for HCB and PCB were estimated using EPISuite 

v.4.0 (USEPA 2008c) (Table 23). These values were used in KABAM to estimate the 

bioaccumulation of each chemical in aquatic food webs. 

Table 23. Estimated Knw. -.., Kno -- and time to steadv state values for HCB and PCB. 

hexachlorobenzene 

'~stimated using Kow method from EPISuite v.4.0 (USEPA 2008c) 3 Estimated using KABAM. 

Contaminant 

pentachlorobenzene 

The time to steady state for HCB and PCB is determined based on KO,. This parameter is used 

to determine the appropriate averaging period of EECs in surface water and the benthic 

compartment. Based on the estimated time to steady state of HCB (48 d), the appropriate 

averaging period for the water column and benthic EECs is the annual 1-in-10 year value. For 

PCB, the estimated 48 d time to steady state falls between the 21-d and 60-d averaging periods 

used by the pe5 shell of PRZMfEXAMS. To be conservative, the 21-d EECs generated by 

PFUMJEXAMS are used for PCB. Water column and benthic EECs for HCB and PCB were 

determined based on the annual 1 -in- 10 year values generated for PCNB and its degradates ( 

Table 24 and Table 25, respectively). These EECs were multiplied by the maximum percent of 

each contaminant that is allowed by EPA in technical PCNB. As noted previously, the EPA 

allows a maximum of 500 ppm (0.05%) for HCB and 100 ppm (0.01%) for PCB~, in technical 

PCNB. In this approach, it is assumed that PCNB, its degradates, HCB and PCB (which is also a 

degradate) have similar transport and degradation properties. The resulting estimated 

concentrations of HCB and PCB are provided in Table 26 and 

Abbreviation 

HCB 

2 Personal communication with Jill Bloom. 

Log K,,' Time to steady state3 

'~stimated using EPISuite v.4.0 (USEPA 2008c) 

PCB 

Page 33 of 70 

KO: 

5.86 

5.22 

5495 200 d 

8492 48 d 
Table 27, respectively. 

Table 25.1-in-10 year 21-d mean EECs (pg/L) for PCNB and its degradates as well as PCB 

in the water column and benthic compartment of the standard pond. 

Table 24.1-in-10 year annual mean EECs (pg/L) for PCNB and its degradates as well as 

Table 26. Estimated concentrations of HCB in tissues of aquatic organisms (base4 on 

maximum allowed level of contamination in technical PCNB). 

potatoes 

Use 

turf 

cabbage 

peanuts 

cotton 

potatoes 

Page 34 of 70 

"Calculated as 0.05% of EEC for PCNB + degradates (values in adjacent column). 

1.56 0.00078 1.90 1 0.00095 

*Calculated as 0.05% of EEC for PCNB + degradates (values in adjacent column). 

Water column 

PCNB + 

degradates 

110 

3 7 

5 5 

11 

16 

Benthic 

PCB 

0.01 1 

0.0037 

0.0055 

0.0011 

0.0016 

PCNB + 

degradates 

56 

28 

2 1 

4.6 

13 

PCB 

0.0056 

0.0028 

0.0021 

0.00046 

0.00 13 
Table 27. Estimated concentrations of PCB in tissues of aquatic organisms (based on 

maximum allowed level of contamination in technical PCNB). 

3.3.4.2. PCDDs and PCDFs 

Small Fish 

Medium Fish 

Large Fish 

The bioaccumulation of PCDDs and PCDFs in a freshwater aquatic ecosystem was estimated 

using KABAM run in default mode (see user's guide for hll description). The KO, and KO, 

values for PCDDs and PCDFs were estimated using EPISuite v.4.0 (USEPA 2008c) (Table 28). 

These values were used to determine input parameter values for KABAM to estimate the 

bioaccurnulation of total PCDDs and PCDFs in aquatic food webs. 

There is greater uncertainty in the bioaccumulation estimates for these contaminants of technical 

PCNB because KABAM is generally appropriate for chemicals with Log &, values 24 to I 8. 

All of the dioxins and furans that are considered contaminants, with the exception of 

Hexachlorodibenzofuran (HxCDF) have estimated Log &, values >8. Uncertainty increases as 

the Log KO, value increases above 8 because the bioaccumulation model of KABAM (Arnot and 

Gobas 2004) has generally been validated using chemicals with Log KO, values within the range 

of 4 - 8. Although predictions for a chemical with a Log KO, > 8 are based upon extrapolations 

in KABAM's subroutines, the model is still expected to be useful for predicting bioaccumulation 

of PCDDs and PCDFs. 

0.116 

0.150 

0.244 

Table 28. Estimated K,, KO, and time to steady state values for PCDDs and PCDlFs that 

represent contaminants of technical PCNB. 

Page 35 of 70 

0.039 

0.051 

0.083 

0.058 

0.074 

0.122 

0.012 

0.015 

0.024 

0.017 

0.022 

0.036 
'~stimated using EPISuite v.4.0 (USEPA 2008c) 

'~stimated using Kow method from EPISuite v.4.0 (USEPA 2008c) 

3stimated using KABAM 

The time to steady state for each contaminant was determined based on KO,. This parameter is 

used to determine the appropriate averaging period of EECs in surface water and the benthic 

compartment. All of the contaminants, with the exception of PCB, require an annual I -in-1 0 year 

EEC to represent the appropriate averaging period (Table 28). Therefore, this averaging period 

(>1 yr) was selected to be representative of PCDDs and PCDFs that contaminate technical grade 

PCNB. 

The TEFs of the PCDDs and PCDFs that represent contaminants of technical PCNB are provided 

in Table 29. For each PCDD and PCDF, the concentration of the chemical is multiplied by its 

TEF. The sum of the product for each PCDD and PCDF represents the toxicity equivalence 

concentration (TEC; Equation 1 ; USEPA 2008a). 

Equation 1. TEC = on cent ration, * TEF, 

Table 29. Measured concentrations of PCDDs and PCDFs in technical PCNB and toxicity 

equivalency factors (TEFs) for mammals for PCDDs and PCDFs that represent 

contaminants of technical PCNB (TEFs from USEPA 2008b). 

I 

1 Compared to 2,3,7,8-TCDD 

OCDD 

1234678-HpCDF I. IYC+UI V.UI 3570 

Based on the concentration of contaminants in the sample analyzed by EPA, the mammalian 

TEC is 0.51 ppb. The congeners 1,2,3,4,6,7,8-HpCDD, 1,2,3,6,7,8-HxCDF and 1,2,3,4,6,7,8- 

HpCDF make up the majority (80%) of the TEC. Therefore, these three congeners are used to 

generate a representative &, (average = 4.4~10~) for PRZMIEXAMS and Log KO, (range 7.92- 

8.85) for KABAM. The TEC was multiplied by the use-specific maximum application rates on 

the label for PCNB to determine the amount of 2,3,7,8-TCDD equivalent PCDDs and PCDFs 

applied with PCNB. The PRZMIEXAMS input parameters for PCDDs and PCDFs used to derive 

surface water and pore water EECs are in Table 30 and Table 3 1. The resulting surface water 1 - 

2.16E+02 ( 0.0003 1 13% 

1234789-HpCDF 

OCDF 

Page 36 of 70 

1.09E-0 1 

2.28E+00 

0.01 

0.0003 

4% 

4% 
in-10 year yearly EECs (water and benthic) are in Table 32. The KABAM-estimated 

concentrations of PCDDs and PCDFs are provided in Table 33 and Table 34. 

Table 30. Use-specific input parameters used in PRZM for PCDDs and PCDFs. 

1.5 xlO*' ( 1 ( FL cabbage I Aug 15 

0.51 x10-' I 1 1 NC peanut I April 15 

0.10x10-~ I 1 I MS cotton 1 Auril 20 

nade via a ground spray with a spray drift fraction of 0.0 

App, Method 

foliar spray 

ground spray; incorp. to 10 cm ** 

ground spray 

ground spray 

ground spray; incorp. to 10 cm ** 

1 and an application efficiency of 0.99 - - - - . * 

cabbage is a surrogate for all COG crops. 3 Application rates represent maximum values allowed by product labels current at the time the ecological risk 

assessment chapter (DP Barcode 291276) was conducted. 

4 Based on USDA Crop Profiles information located at http://pestdata.ncsu.edu/cropprofiles 

V 1 -d application interval 

**CAM = 4 

Table 31. Chemical-specific input parameters used in PRZMIEXAMS for PCDDs and 

PCDFs. 

Table 32.1-in-10 year surface water and pore water EECs (pg/L) of PCDDs and E?CDFS 

generated by current version of PRZM/EXAMS. 

Use ( Surface Water (pg/L) I Sediment Pore Water (pg/L) 

Page 37 of 70 

7 

Source 

Average of: 375 (HxCDF), 409 (HpCDF), 425 

(HpCDD), values calculated using EpiSuite 

v.4.0 

Average of: 1.1 e-7 (HxCDF), 2.9e-8 (HpCDF), 

2.7e-9 (HpCDD), values estimated using 

EpiSuite v.4.0 

Average of: 6.8e-6 (HxCDF), 5.0e-6 (HpCDF), 

1.4e-6 (HpCDD), values estimated using bond 

method of EpiSuite v.4.0 

Average of: 5.9e-5 (HxCDF), 1.0e-5 (HpCDF), 

1.6e-5 (HpCDD), values estimatad using 

EpiSuite v.4.0 

Assume stable 

Assume stable 

Assume stable 

Assume stable 

Assume stable 

Mean of EpiSuite v4.0 values for HpCDD, 

HxCDF and HpCDF 

Parameter (units) 

Molecular Weight (glmol) 

Vapor Pressure (torr) 

Henry's Law Constant (atm-m3-mol) 

Solubility in Water at 25'C (mg/L) 

Hydrolysis Half-life @pH 7 (days) 

Aquatic Photolysis Half-life @ pH 5 (days) 

Aerobic Soil Metabolism Half-life (days) 

Aerobic Aquatic Metabolism Half-life 

(days) 

Anaerobic Aquatic Metabolism Half-life 

(days) 

Soil Partition Coefficient (Kd; mL/g) 

Value 

403 

4.7 x10-~ 

4.5 x10-~ 

2.8 x~o-~ 

0 

0 

0 

0 

0 

4.4 XIO~ 
I Turf I Cabbage 0.84 ~10~' 0.23 x10-" 1 

Table 33. Estimated concentrations of PCDDs and PCDFs in aquatic organisms. Values 

generated using Log Kow = 7.92. 

Peanuts 

Cotton 

Potatoes 

I Phytoplankton 1 9.7 x10-~ 1 1.3 ~10.~ 1 2.4 x10*~ 1 5.8 XIO-~ 1 4.6 x10-~ I 

1.5 x~O-~ 

0.36 x10e8 

0.029 xl0-' 

- - - 

0.43 ~10~" 

0.097 x10-~ 

0.0079 x10-' 

Trophic Level 

Table 34. Estimated concentrations of PCDDs and PCDFs in aquatic organisms. Values 

generated using Log KO, = 8.85. 

- - 

Zooplankton 

Benthic Invertebrates 

Filter Feeders 

Small Fish 

Medium Fish 

Large Fish 

Turf 

3.4. Risks to Mammals, Birds, Terrestrial-phase Amphibians and Reptiles 

Consuming Aquatic Organisms 

8.9 x~o-~ 

9.0 X~O" 

6.1 XIO-~ 

2.2 x~o-~ 

3.7 XIO-~ 

9.4 x~o-~ 

Trophic Level 

Phytoplankton 

Zooplankton 

Benthic Invertebrates 

Filter Feeders 

Small Fish 

Medium Fish 

Large Fish 

OPP compared EECs of PCNB and its degradates in tissues of aquatic organisms (Table 17) to 

chronic toxicity data for mammals and birds using the risk quotient (RQ) method to evaluate the 

risks of adverse ecological effects from PCNB and its degradates to non-target species. As 

discussed previously, chronic RQs are calculated by dividing exposure concentrations by chronic 

toxicity endpoints (i.e., NOAEL or NOAEC). The RQs are then compared to the Agency's 

established level of concern (LOC) to evaluate risks to non-listed and listed animals. The 

chronic risk LOC for both non-listed and listed species is an RQ value of greater than or equal to 

1.0 OJSEPA 2004a). If RQ values exceed the LOC, then the assessed use of PCNB has the 

potential to cause adverse chronic effects to non-target mammals, birds, terrestrial-phase 

amphibians and reptiles that consume aquatic organisms. 

Cabbage 

Page 38 of 70 

1.2 x~o*~ 

1.2 x~o-~ 

8.4 x10-~ 

3.0 xlOW5 

5.1 xlo-' 

1.3 xlOV4 

Turf 

1.0 x~o-~ 

1.8 x10b4 

8.3 xlo" 

5.8 xlo" 

8.3 XIO-~ 

5.9 ~104 

4.5 XIO-~ 

Peanuts 

2.2 ~10'~ 

2.2 x~o-~ 

1.5 x~o-~ 

5.4 XIO-~ 

9.2 XIO-~ 

2.3 x10q4 

Cabbage 

1.4 x1u6 

2.4 XIO-~ 

1.1 ~10" 

8.1 x10-~ 

1.1 XIO-~ 

8.1 x10-~ 

6.1 x10-~ 

Cotton Potatoes 

5.2 x10-~ 

5.3 x10-~ 

3.6 x10-~ 

1.3 x~o-~ 

2.2 x~o-~ 

5.6 xlo" 

Peanuts 

2.5 x10-~ 

4.4 XIO-~ 

2.1 x~o-~ 

1.4 x~o-~ 

2.0 XIO-~ 

1.4 x~o-~ 

1.1 ~104 

4.2 x10'~ 

4.3 x~o-~ 

2.9 xlu7 

1.0 x10-~ 

1.8 x10-~ 

4.5 x10-~ 

Cotton 

6.0 x~o-~ 

1.0 X~O-~ 

4.9 x10m6 

3.4 ~10'~ 

4.9 x10-~ 

3.5 x10-~ 

2.6 x10-~ 

Potatoes 

4.8 x10-' 

8.4 XIO-~ 

4.0 x~o-~ 

2.8 XIO-~ 

3.9 x~o-~ 

2.8 XIO-~ 

2.1 x~o-~ 
RQs for mammals and birds exposed to PCNB and its degradates on a chronic exposure basis 

through consumption of aquatic organisms are provided in Table 35 to Table 41. As discussed 

previously, RQs for birds are used as surrogates for terrestrial-phase amphibians and reptiles that 

consume aquatic organisms. The exposure component of the RQ values was calculated using 

KABAM v1 .O. 

3.4.1. Chronic Risks to Mammals from PCNB and its Degradates 

For chronic, dose-based exposures of mammals to PCNB and its degradates, RQs exceed the 

chronic risk LOC (1.0) for all default mammals (i.e., fog shrew, water shrew, rice rat, star-nosed 

mole, mink and river otter) across all assessed uses of PCNB (Table 35). Dietary-based RQs 

also exceed chronic risk LOCs for all mammals modeled and for all uses of PCNB (Table 36). 

Although dietary-based RQ values are considerably lower than dose-based RQ values, the 

former do not take into account that different sized animals consume differing amounts of food. 

If dietary-based RQ values are adjusted to account for differential food consumption, the 

adjusted RQ value would likely approximate the dose-based RQ value. 

1 rice ratistar-nosed mole 1 126" 1 62.4" 1 42.7" 1 18.5" 1 12.5" 1 

Table 35. RQs for chronic, dose-based exposures to mammals consuming aquatic 

organisms which have accumulated PCNB and its degradates. Values calculated using 

KABAM v1.0. 

I small mink 1 193" 1 95.7" 1 65.6" 1 28.4" 1 19.2" 1 

1 large mink 1 213' 1 106" 1 72.5' 1 31.4" 1 21.2" 1 

Trophic Level 

fodwater shrew 

Peanuts 

33.6" 

Table 36. RQs for chronic, dietary-based exposures to mammals consuming aquatic 

Turf 

98.7" 

small river otter 

large river otter 

- - 

organisms which have accumulated total PCNB and its degradates. Values calculqted using 

KABAM v1.0. 

Cotton 

14.6" 

Cabbage 

49.0" 

Potatoes 

9.8" 

*RQ exceeds chronic LOC (RQ21) for listed and non-listed mammals. 

229" 

343" 

Trophic Level 

foglwater shrew 

I large river otter 1 42.6" / 21.2" 1 14.4" 1 6.3" 1 4.D" I 

114" 

171" 

rice ratistar-nosed mole 

small mink 

large mink 

small river otter 

*RQ exceeds chronic LOC for listed and non-listed mammals. 

Turf 

17.7" 

The chronic toxicity component of the RQs for mammals is based on the level where no effects 

(NOAEL) to rats exposed to PCNB were observed in a 2-generation reproduction study (i.e., 1.2 

mglkg-bwlday). At the LOAEL for the study (169 mglkg-bw), decreases were observkd in body 

weights of offspring and parents. Dose-based EECs calculated by KABAM for PCNB use on turf 

78.0" 

116" 

18.5" 

30.8" 

30.8" 

30.8" 

Page 39 of 70 

33.8" 1 22.8" 

50.3" 1 34.2" 

Cabbage 

8.8" 

9.2" 

15.3" 

15.3" 

15.3" 

Peanuts 

6.0" 

6.3" 

10.5" 

10.5" 

10.5" 

Cotton 

2.6" 

Potstoes 

1.8" 

2.7" 

4.6" 

4.6" 

4.6" 

1.8" 

3.1" 

3.1" 

3.1" 
and cabbage are sufficient to exceed the dose-based LOAEL for this study. This indicates that 

concentrations of PCNB residues in aquatic organisms are estimated to be above levels where 

effects to rats were actually observed in the laboratory. 

The concentration of PCNB and its degradates in fish that is sufficient to be of concern for mink 

and otters is >3 mglkg (i.e., would result in a RQ that exceeds the LOC). For all uses of PCNB, 

predicted concentrations of PCNB and its degradates in aquatic organisms based on the lowest 

Log KO, (4.22) value reported for PCNB are still sufficient to exceed the chronic risk level of 

concern for mink and otter (Table 18 and Table 19). 

If RQs were generated for mammals using the 60-d EECs in Table 21, these values would be 

sufficient to exceed the chronic risk LOC for mammals across all modeled uses of PCNB (i.e., 

predicted concentrations in aquatic organisms exceed 3 mglkg). Therefore, the use of surface 

water and sediment pore water EECs with 21-d and 60-d averaging periods (which represents a 

bound of the 30-d time to steady state that is representative of PCNB and its degradates) yield 

the same conclusions that for all assessed uses of PCNB, predicted concentrations of PCNB and 

its degradates in aquatic organisms are sufficient to pose a risk of chronic effects to mammals. 

The number of days where the water column concentration is sufficient to result in 

concentrations of PCNB and its degradates in aquatic organisms that are of concern can also be 

considered. According to the KABAM user's guide, for a chemical with a Log KO, of 5, 

estimates of pesticide concentrations in aquatic organisms are sensitive to changes in the water 

column EEC, but not to changes in the benthic EEC. Therefore, with the pore water EEC set to 0, 

the highest value was determined for the water column EEC that results in a chronic (dosebased) RQ that does not exceed the LOC. Based on the NOAEL of 1.2 mglkg-bw, this water 

column EEC is 0.32 pg/L. The number of simulated days (out of 10958) that result in water 

column EECs that exceed 0.32 pg/L for each use of PCNB are provided in Table 37. 

Using the exposure values in Table 22 that account for volatilization, concentrations of PCNB 

and its degradates in aquatic organisms would be sufficient to exceed the chronic risk LOC for 

all assessed uses of PCNB for mammals (i.e., predicted concentrations in aquatic organisms 

exceed 3 mglkg). Therefore, although accounting for loss (from the application site and aquatic 

water body) of PCNB and its degradates through volatilization results in decreased predictions of 

PCNB and its degradates in aquatic organisms, the conclusions associated with the cllronic RQs 

for mammals and birds (Table 35 and Table 36) do not change. 

Table 37. Number of simulated days in PRZMIEXAMS where water column EEC is at a 

level sufficient to exceed risk to mammals consuming aquatic organisms that have 

accumulated PCNB and its degradates. 

Page 40 of 70 

Use 

Turf 

Cabbage 

Peanuts 

Cotton 

Potatoes 

# days where water 

concentration is sufficient to 

exceed LOC 

8695 

9578 

9584 

8068 

6348 

% of total days where water 

column EEC that is sufficient to 

exceed LOC 

79% 

87% 

87% 

74% 

58% 
Based on this information, fog shrews, water shrews, rice rats, star-nosed moles, mi& and river 

otters consuming aquatic organisms that have accumulated residues of PCNB and its degradates 

have the potential to experience adverse chronic effects due to exposures to PCNB and its 

degradates in aquatic forage items. 

3.4.2. Chronic Risks to Mammals from Contaminants 

3.4.2.1. HCB and PCB 

For PCNB contaminants HCB and PCB, dose-based RQs were derived for a large river otter 

(assumed to eat 100% large fish) based on individual contaminant levels in those fish and 

toxicity data for PCNB. In this approach, it was assumed that HCB and PCB were equivalent in 

toxicity to PCNB. The large river otter was selected since it represents the highest (most 

conservative) RQ for mammals consuming aquatic organisms. 

The river otter RQ for HCB resulting from PCNB use on turf exceeds the chronic risk LOC, 

suggesting potential for effects from the HCB contaminant when PCNB is used on turf (assumes 

HCB is present at 0.05% of technical PCNB). All other modeled uses of PCNB result in RQs for 

HCB that are below the chronic risk LOC, indicating a low potential for adverse chronic effects 

to mammals consuming fish (Table 38). 

All modeled uses of PCNB result in RQs for PCB (as a contaminant) that are below the LOC. 

This indicates that the maximum level of PCB contamination allowed by the EPA (0.01% of 

technical PCNB) has a low potential for risk to mammals consuming fish (Table 38). Note that 

this conclusion does not consider exposure due to degradation of PCNB to PCB. 

Table 38. Chronic, dose-based RQs for large otter (most conservative RQs generated by 

KABAM) exposed to HCB and PCB. 

I Turf I 1.64* 1 0.082 / 

Use 

1 Cabbage 0.57 0.03 

HCB 

*Exceeds LOC (1 .O) 

PCB 

Peanuts 

Cotton 

Potatoes 

3.4.2.2. PCDDs and PCDFs 

Estimated concentrations of PCDDs and PCDFs in aquatic organisms (Table 33 and Table 34) 

were used to determine potential chronic risks to mammals. These EECs were compared to 

chronic mammalian toxicity endpoints for 2,3,7,8-TCDD that were identified by the USEPA 

Office of Water (OW) for the Great Lakes Water Quality Initiative Criteria for the ~rbtection of 

Wildlife (USEPA 1995). As discussed previously in this assessment, OW defined a NOAEL of 

0.75 

0.25 

0.13 

Page 41 of 70 

0.04 

<0.01 

0.0 1 
0.001 pglkg-bwlday (1x10-~ mglkg-bwlday) for reproductive effects to mammals exposed to 

2,3,7,8-TCDD in food. This NOAEL was based on reduced fertility in first (fi) and second 

generation (fi) rats exposed to a LOAEL of 0.01 &kg-bwlday reported by Murray et al. 1979. 

When this NOAEL is used in KABAM, chronic, dose-based mammalian RQs for PCDDs and 

PCDFs representing contaminants of PCNB are sufficient to exceed the chronic risk LOC (1.0) 

for all modeled mammals for PCNB uses on turf, cabbage, peanuts and cotton (Table 39 and 

Table 40). In addition, estimated levels of PCDDs and PCDFs resulting from PCNB use on turf, 

cabbage, peanuts and cotton are sufficient to exceed the LOAEL (i.e., 0.01 yglkg-bw/day) for 

reproductive effects for some mammals. Therefore, for PCNB use on turf, cabbage, peanuts and 

cotton, PCDDs and PCDFs residues in technical PCNB (based on the levels measured by EPA) 

pose a risk of reproductive effects to mammals that consume aquatic organisms. 

For PCNB use on potatoes, PCDD and PCDF levels in aquatic organisms are sufficient to exceed 

the chronic risk LOC only for the large river otter when considering the lower Log KO, value 

(7.92) within the range of KO, values representative of PCDDs and PCDFs that contaminate 

PCNB. 

Table 39. Chronic, dose-based RQs for mammals (that consume aquatic organisms) 

exposed to PCDDs and PCDFs. RQs based on use of Log K, = 7.92. 

Species 

Table 40. Chronic, dose-based RQs for mammals (that consume aquatic organisms) 

exposed to PCDDs and PCDFs. RQs based on use of Log &, = 8.85. 

fogiwater shrew 

rice ratlstar-nosed mole 

small mink 

large mink 

small river otter 

large river otter 

Turf 

*RQ exceeds LOC (1.0). 

25* 

42 * 

120" 

130" 

140X 

380" 

Species 

Cabbagc 

foglwater shrew 

rice ratlstar-nosed mole 

small mink 

3.4.3. Chronic Risks to Birds, Terrestrial-phase Amphibians and Reptiles 

from PCNB and its Degradates 

3.4" 

5.8" 

16" 

18" 

19" 

52" 

Turf 

large mink 

small river otter 

large river otter 

Page 42 of 70 

Peanuts 

23 * 

25" 

18* 

6.2" 

lo* 

29" 

32* 

34" 

93 * 

Cabbage 

*RQ exceeds LOC (1.0). 

20" 

Cotton 

3.2" 

3.5* 

2.5" 

2.8" 1 2.0" pp1 3.0" 

Potatoes 

1.5" 

2.5" 

6.9" 

7.6" 

8.2" 

22" 

Peanuts 

1.2" 

5.4" 1.3" 

0.12 

0.20 

0.56 

0.61 

0.66 

1.8" 

5.7" 

6.3" 

4.5" 

0.10 

22 * 0.10 

Cotton 

18" 

Potatoes 

1.4" 

1.5* 

1.1" 

0.1 1 

0.12 

0.09 

2.5" 4.4" 1.1" 0.09 
Dietary-based RQs for turf exceed the chronic risk LOC (1.0) for birds represented by small 

osprey and white pelicans (which have a diet comprised entirely of fish; Table 41). Chronic RQs 

are based on the level (NOAEC) where no effects to birds were observed in reproduction studies. 

Birds are assumed to be surrogates for terrestrial-phase amphibians and reptiles. Therefore, 

PCNB use on turf has the potential to result in chronic effects to birds, amphibians and reptiles 

that consume aquatic organisms that have accumulated PCNB and its degradates. 

Dietary-based RQs for birds from use of PCNB on cabbage, peanuts, cotton and potatoes do not 

exceed the LOC (Table 41). Therefore, for PCNB uses other than turf, effects on growth and 

reproduction are not expected in birds, amphibians and reptiles that consume aquatic organisms. 

Table 41. RQs for chronic, dietary-based exposures to birds consuming aquatic organisms 

which have accumulated PCNB and its degradates. RQs for birds sewe as surrogates for 

1 Cranes 1 0.8 1 0.4 1 0.3 1 0.1 1 0.1 1 

terrestrial-phase amphibians and reytiles. Exposure calculated using KABAM (v1.0). 

( Herons 1 .O 0.5 0.3 0.1 0.1 

Trophic Level 

sandpipers 

I Rails I I I I I 

Turf 

0.7 

Cabbage 

0.4 

0.9 

RQs for PCNB and its degradates are based on a Log KO, value of 5.0. This leads to uncertainty 

in bioaccumulation and associated risk estimates. This uncertainty can be explored by 

considering the lowest and highest reported Log KO, values for PCNB, which are 4.22 and 5.3, 

respectively. For all uses of PCNB, predicted concentrations of PCNB and its degradates in 

aquatic organisms based on the lowest Log KO, (4.22) value reported for PCNB are not sufficient 

to represent a chronic risk to birds for any assessed use of PCNB. For the highest Log KO, value 

for PCNB (5.3), concentrations of PCNB and its degradates in aquatic organisms are sufficient to 

be of concern for birds for use of PCNB on turf, peanuts and cabbage. 

If RQs were generated for birds using the 60-d EECs in Table 21, these values would be 

sufficient to exceed the chronic risk LOC for birds for the use of PCNB on turf. Therefore, the 

use of surface water and sediment pore water EECs with 2 1 -d and 60-d averaging periods (which 

represents a bound of the time to steady state of uptake of PCNB and its degradates) yield the 

same conclusion that for use of PCNB on turf, predicted concentrations of PCNB and its 

degradates in fish are sufficient to result in adverse chronic effects to birds and by extension to 

terrestrial-phase amphibians and reptiles. 

Peanuts 

0.3 

small osprey 

white pelican 

Using the exposure values in Table 22 that account for volatilization, PCNB and its degradates in 

aquatic organisms would be sufficient to exceed the avian chronic risk LOC from use of PCNB 

on turf . Therefore, although accounting for loss (from the application site and 

body) of PCNB and its degradates through volatilization results in decreased 

0.4 

*RQ exceeds chronic LOC for listed and non-listed birds. 

0.6 

0.8 

1.2* 

1.7* 

Page 43 of 70 

Cotton 

0.1 

0.3 0.1 

Potatoes 

0.1 

0.1 

0.4 

0.6 

0.2 

0.3 

0.1 

0.2 
PCNB and its degradates in aquatic organisms, the conclusions regarding potential risks to birds 

(Table 41) do not change. 

3.4.4. Chronic Risks to Birds, Terrestrial-phase Amphibians and Reptiles 

from Contaminants 

3.4.4.1. HCB and PCB 

Chronic, dietary-based RQs for all of the avian surrogate species used in the KABAM model 

exposed to the PCNB contaminants HCB and PCB fkom PCNB use on turf are at least 4 orders 

of magnitude below the chronic risk LOC (1.0). This indicates that for all uses of PCNB, the 

maximum levels of HCB and PCB are not expected to cause effects on growth and reproduction 

of birds, terrestrial-phase amphibians and reptiles. 

3.4.4.2. Polychlorinated-dibenzodioxins and -dibenzofurans 

Chronic avian toxicity data identified by OW for 2,3,7,8-TCDD were not considered in this 

assessment because the birds were dosed intraperitoneally and not through the diet. Therefore, 

potential risks to birds, terrestrial-phase amphibians and reptiles have not been assessed for 

PCDDs and PCDFs. 

4. Bioaccumulation of PCNB and its Degradates in Terrestrial Organisms and Associated 

Risks 

Pesticide bioaccumulation in terrestrial ecosystems has rarely been incorporated into past 

ecological risk assessments conducted by OPP. In previous ecological risk assessments of 

PCNB, bioaccumulation of PCNB and its degradates was not considered. At this time, OPP does 

not have specific data requirements or sufficiently vetted tools to estimate pesticide 

bioaccumulation in terrestrial ecosystems. Methods related to assessing bioaccumulation in 

terrestrial ecosystems are not as developed as those available for aquatic habitats. 

In regard to factors that EPA can consider when identifying terrestrial bioaccumulation potential 

of a pesticide, the SAP indicated that a chemical's octanol-water and octanol-air partition 

coefficients (KO, and KO,, respectively) are important. As discussed in USEPA 2008a, several 

authors, including: Kelly and Gobas (2003), Armitage and Gobas (2007) and Kelly et al. (2007) 

concluded that chemicals with Log I(OA >5 and Log I(Ow>2 may biomagnify in terrestrial food 

chains. The SAP also indicated that metabolism of pesticides by organisms should also be 

considered, since metabolism of a chemical may change the likelihood of a chemical to 

bioaccurnulate. Currently, OPP uses a simple fugacity approach (described below) for estimating 

concentrations of PCNB and its degradates in earthworms inhabiting fields treated with PCNB, 

as an initial indication of bioaccumulation potential. 

Page 44 of 70 
4.1. Accumulation of PCNB and its Degradates in Soil 

Because PCNB and its degradates are persistent in soil (with an upper 90% confidence bound on 

the mean aerobic soil metabolism half-life of 1052 days) and do not have a tendency to leach 

from soil (non-sand Kd values range 15.5 - 210 mL/g, MRID 41648201), an analysis was 

conducted to characterize the levels of PCNB and its degradates in the soil of a treated site after 

30 years of applications. In order to accomplish this, PRZM was run using the input parameters 

for PCNB and its degradates as defined in Table 42 and Table 43. The studies and analysis that 

form the basis for these values are more thoroughly described in the environmental fate and 

ecological risk assessment chapter written in support of the RED for PCNB (DP Barcode 

291276). 

0.99 

2 Cabbage is a surrogate for all cole crops. 3 Application rates represent maximum values allowed by product labels current at the time the ecological risk 

assessment chapter (DP Barcode 291276) was conducted. 

4 Based on USDA Crop Profiles information located at http://pestdata.ncsu.edu/cropprofiles 

Table 43. Chemical-specific input parameters for PCNB and its degradates used in PRZM. 

Parameter (units) 

Molecular Weight - (dmol) .- I Vapor Pressure (Tori-) , I 

421 12801 

Aerobic Aquatic Metabolism Half-life (days) I 2248 I MRIDs42911902,41384501,41713202, 

1.13 x lo4 

Henry's Law Constant (atm-m5-mol) 

Solubility in Water at 25OC (ppm) 

Hydrolysis Half-life @ pH 7 (days) 

Aquatic Photolysis Half-life @ pH 5 (days) 

Aerobic Soil Metabolism Half-life (days) 

Value 

295.3 

Product chemistry data 

input value is 2X the aerobic soil metabolism half-life input value for total residues as per input parameter 

guidance 

input value is two times the anaerobic soil metabolism half-life value Of 1002 days, calculated for total residues as 

per input parameter guidance 4 lowest non-sand Kd 

Source 

Product chemistrv data 

4.42 x 10" 

0.44 

stable 

1.83 

1124 ' 

Anaerobic Aquatic Metabolism Half-life (days) 

Soil Partition Coefficient (Kd; mL/g) 

Page 45 of 70 

Product chemistry data 

Product chemistry data 

MRIDs 40865301,40972601 

MRIDs 42606201,42606202,42336201 

MRIDs 42911902,41384501,41713202, 

represents the 90' percentile of the upper confidence bound on the mean of 2 half-life values; for total residues 

2004 

15.5 

421 12801 

MRID 41384301 

MRlD 41648201 
The resulting estimates of PCNB and its degradates in soil based on PCNB use on cabbage, 

cotton, peanuts, potatoes and turf are depicted in Figure 3, which indicates that PCNB and its 

degradates are expected to increase over time in soils where PCNB is applied. It is assumed that 

the annual average soil concentration is representative of the steady state concentration of PCNB 

and its degradates in soil (Table 44). 

simulation day 

-Cabbage - Cotton Peanut Potatoes ---Turf 

Figure 3. Estimated concentrations of PCNB and its degradates in soil of cabbage, cotton, 

peanut, potato and turf fields treated with of PCNB. 

I Cabbage 55 

Table 44. Average of annual averages (30 years) of estimated concentrations of PCNB and 

its degradates in soil for different uses of PCNB. 

Use 

4.2. Bioaccumulation Potential 

Average of annual averages (mg/m3) 

Peanuts 

Cotton 

Potatoes 

As discussed above, Kelly and Gobas (2003), Armitage and Gobas (2007) and Kelly et al. 

(2007), concluded that chemicals which do not undergo substantial metabolism within organisms 

and have >lo5 and KO, >lo2 have the potential to bioaccumulate and biomagnify in 

terrestrial food chains. For example, Kelly and Gobas (2003) estimated biomagnifications factors 

for HCB (Log KOA = 7.1, Log KO, = 5.5) ranging 5.4-41.1 for male wolves. Based on the 

27 

5.3 

14 

Page 46 of 70 

Turf 10 
estimated (log) KOA and I?, values for PCNB and its individual degradates, which are provided 

in Table 45, PCNB and its degradates have the potential to biomagnify in terrestrial ecosystems. 

A simple fugacity approach is used in this assessment to estimate concentrations of PCNB and 

its degradates in earthworms inhabiting fields treated with PCNB as an initial indication of 

bioaccumulation potential. This approach is explained in detail in Appendix C. Using PRZMestimated concentrations of PCNB and its degradates that are representative of steady state 

(average of annual averages), concentrations of PCNB and its degradates in earthworms range 

from 0.21 to 2.2 mglkg (Table 46). These concentrations are two orders of magnitude higher 

than estimated concentrations in the soil in which the earthworms live, indicating that PCNB and 

its degradates can accumulate in soil-dwelling organisms inhabiting fields treated with PCNB. 

Table 45. Estimated Log KOA and Kow values for PCNB and its degradates. 

Residue 

pentachloronitrobenzene 

pentachloroanilinel 

pentachlorothioanisolel 

pentachlorobenzenel 

pentachlorophenol 

pentachlorothioanisole sulfoxide 

pentachlorothioanisole sulfone 

Table 46. Estimated concentrations of PCNB and its degradates in soil and in earthworms. 

I Cotton 1 0.0032 1 0.21 1 

'~ajor environmental degradate 

Estimated using EPISUITE v. 4.0 (USEPA 2008c) 

Abbreviation 

PCNB 

PCA 

PCTA 

PCB 

PCP 

PCTASO 

PCTAS02 

Use 

Turf 

Cabbage .d I - - I 

Potatoes 0.0085 0.55 I 

*Calculated using average of annual averages reported in Table 44 and converting them using th8 soil bulk 

density (1650 kg soil/m3). 

Peanuts 

4.3. Metabolism of PCNB in Terrestrial Organisms 

Log ~0.4~ 

7.4 

9.6 

8.7 

6.7 

11 

11 

8.7 

Concentration in soil (mg/kg)* 

0.0061 

0.033 

The HED Metabolism Assessment Review Committee (MARC) met on April 16'~~ 2003 to 

determine the residues of concern and the PCNB tolerance expression for plants and livestock, as 

well as degradates of concern in water. The following text, from the MARC memo3, summarizes 

the findings of the review: 

Log KO$ 

5 .O 

4.3 

5.8 

5.2 

4.7 

3.7 

3.8 

Concentration in earthworms (mg/kg) 

0.39 

2 2 

0.016 

3 Pentachloronitrobenzene (PCNB). (List A, Case No.0128) The Outcome of the HED Metabolism Assessment 

Review Committee Held on April 16th, 2003 to discuss residues of concern in risk assessment and tolerance 

expression of PCNB. Chemical 056502. Mohsen Sahafeyan & Laurence Chitlik. May 27th, 2003 

1.1 

Page 47 of 70 
The MARC reviewed the major and minor metabolites of pentachloronitrobenzene 

(PCNB) identified in three plant metabolism studies (peanuts, potatoes, and cabbage), 

livestock (ruminant and poultry) metabolism study, rotational crop studies (lettuce, turn* 

roots and tops, and wheat), available field trial data, and information on environmental 

persistence and degradation of PCNB. The URC also reviewed the available rat 

metabolism studies. 

For the primary crops, plant metabolism studies on peanuts, potato, and cabbage [study 

deemed unacceptable] indicated that the major ident@ed radioactive residues (i. e. 21 0% 

total radioactive residue or TRR) were PCNB, S- (pentach1orophenyl)malonycysteine 

(PCP-MalCys), N-malonyl-S-(tetrach1oroaminophenyl)- cysteine, tetrachlorophenyl 

methyl sulfoxide (TCPM sulfoxide), and tetrachlorophenyl methyl sulfone (TCPM 

sulfone). Other residues comprising 210% of the TRR were not identzfied or 

characterized in the cabbage study. However, for peanut five metabolites and for potato 

thirty-six metabolite residues were identified. As all of the identifiedplant metabolites of 

PCNB in primary crops are poly-chlorinatedphenyl compounds, all of these compounds 

(including minor metabolites) are of concern. 

For rotational crops, numerous metabolites were identijied in just about all crop parts 

studied in the confined rotational crop study. The crop parts studied included: turnip root 

and tops from 365 days after soil treatment (DAT), lettuce (30, 120, and 365 DAT), wheat 

forage (30 and 120 DAT), wheat grain (30, 120, and 365 DAT), and wheat straw (120 

DAT). As all of the identified metabolites in rotational crops are poly-chlorinated phenyl 

compounds, all of these compounds (including minor metabolites) are of concern. 

Studies concerning the metabolism of PCNB in lactating goats and poultry were 

submitted. The major identged metabolites in ruminant tissues included PCA, 

pentachlorothiophenol (PCTP), tetrachlorothioanisole (TCTA), N-(pentachloroaniline) 

glucuronide (PCA-Gluc), and glucuronide of N-hydroxypentachloroaniline (2vOHPCAGluc). The major identified metabolites in poultry tissues included PCNB, PCA, 

pentachlorothiophenol (PCTA), pentachlorothioanisole sulfoxide (PCTA sulfoxide), TCA 

sulfoxide, tetrachlorophenyl methyl sulfone (TCP methyl sulfone) and tetrachloroaniline 

methyl sulfoxide (TCA sulfaxide isomers). As all of the identified metabolites are polychlorinated phenyl compounds, all of these compounds (including minor metabolites) are 

of concern. 

In summary, available studies with terrestrial plants (i.e., crops) and animals indicate that PCNB 

is metabolized by terrestrial organisms; however, all metabolites that were identified were polychlorinated phenyl compounds and deemed by HED to be of concern. The effect of PCNB 

metabolism on the overall bioaccumulation in terrestrial organisms is unknown; however, 

metabolism of PCNB does not necessarily render the degradates less toxic than the parent. 

4.4. Risks to Mammals, Birds, Terrestrial-phase Amphibians and Reptiles 

Consuming Earthworms 

Page 48 of 70 
PCNB is classified as practically non-toxic to mammals and birds on an acute exposure basis. By 

assuming equivalent toxicity of PCNB and its degradates, the likelihood of mortality in these 

animals from acute exposures to PCNB and its degradates is considered low. 

Longer-term concentrations of PCNB and its degradates in earthworms (0.2 1-2.2 mglkg; Table 

46) are below the chronic toxicity endpoints for mammals (i.e., NOAEC = 24 mglkg) and for 

birds, terrestrial-phase amphibians and reptiles (i.e., NOAEC = 600 mglkg). Therefore, it is 

unlikely that these animals will be subject to risk fkom chronic exposures to PCNB and its 

degradates as a result of consuming earthworms on fields treated with PCNB. 

This assessment only considers accumulation of PCNB and its degradates in one trophic level 

and the subsequent risks to animals consuming earthworms (i.e., vermivores). If PCNB and its 

degradates subsequently accumulate in vermivores, such as voles and robins, predators of these 

vermivores (e.g., foxes, hawks) may be exposed to even higher levels of PCNB and its 

degradates than are predicted in earthworms. Since OPP has no tool available to assess 

bioaccumulation in terrestrial food webs (beyond earthworms), the extent of this accumulation 

cannot be quantified at this time. Therefore, risks to higher trophic level animals consuming 

terrestrial animals cannot be precluded. 

5. Long Range Transport Potential (LRTP) of PCNB and its Degradates 

The SAP advised the Agency to consider a holistic approach utilizing all available lines of 

evidence to evaluate the LRTP of persistent pesticides. In addition to using travel distance to 

characterize LRTP of a pesticide, they also suggested that EPA include the evidence of sources 

and sinks of persistent pesticides in the ecosystem. This requires going beyond simple ranking of 

the long range transport potential of chemicals and providing a more quantitative analysis of 

pesticide transport to air from a use site and transport away from source regions. As a short-term 

solution to assessing the LRTP of a chemical, the SAP suggested that EPA employ a tiered 

approach: 

o Tier 1 : Determine if the estimated (EPISUITE: AOPWIN) or measured atmospheric 

degradation half-life is great& than 2 days 

o Tier 2: Use the OECD Screening Tool to calculate overall persistence, travel distance 

and transfer efficiency for the compounds of interest and compare outputs to those of 

known persistent organic pollutants (POPS). 

o Tier 3: Use more sophisticated models (e.g., GloboPOP) to assess LRTP. 

In this assessment, the LRTP of PCNB and its degradates is assessed by considering available 

data on PCNB volatilization, by evaluating available monitoring data, and by using the Tier 2 

methodology recommended by the SAP. 

5.1. Volatilization Data 

PCNB is a moderately volatile compound that can be expected to dissipate through volatilization. 

Volatilization is a more significant route of dissipation of the parent and the PCA degradate 

when PCNB is not incorporated into the soil at application. This will occur when PCNB is 

Page 49 of 70 
applied as a foliar spray (e.g., to turf) or is applied by chemigation through overhead sprinkler 

irrigation (e.g., to potatoes). Based on its vapor pressure (1.13 x 1 o4 tow @25OC), PCNB is 

expected to exist primarily in the vapor phase while in the atmosphere. 

Submitted data from a laboratory volatility study (MRID 41178001) showed that maximum 

volatilization of PCNB residues occurred within 24 hours of treatment. In a field volatility study 

(MRID 4375 1101), volatilized PCNB and PCA were both at their observed maximums on Day 0 

and declined throughout the rest of the 13-day study. It should be noted that large amounts of 

rain fell during study days 3 to 9 may have altered the volatilization rate relative to that which 

might otherwise have occurred. 

Casely (1968) observed that PCNB may volatilize more from moist or saturated soils relative to 

dry ones due to decreased adsorption in the wetter soils. In this study, greater than two thirds of 

the approximately 80% of applied PCNB was lost due to volatilization from soil during 10 

months of incubation, with the remaining losses attributed to microbial degradation. 

Large Henry's Law constants for the degradates PCA, PCTA, PCB and PCP (on the order of 

to atm/m3-mol) indicate that volatilization may also be an important environmental fate 

process for these compounds as well. 

5.2. Monitoring Studies 

Monitoring studies reported in the literature that involved PCNB included studies conducted in 

Canada where PCNB was detected in air over Saskatchewan (SK). PCNB was detected in 10 of 

1 1 samples (at 0.0 1 - 1.60 ng/m3) collected during a 3-month period in the summer of 1994 over 

Regina, SKY and in 2 of 5 samples collected during that time over Waskesiu, SK (Table 47). The 

compound was not detected in any of 7 samples collected over Yellowknife, SK. The authors 

indicated that the registered uses of PCNB in Canada at that time (i. e., ornamentals, ginseng and 

turf) were not "major crops" grown in that part of SK (Thompson et al., 1997). 

Table 47. Measured concentrations of PCNB in air samples collected at areas removed 

from anr~lication sites. 

Waskesiu, Saskatchewan 

Mount Revelstoke national Park, British 

Columbia 

In another study that was conducted in Canada, PCNB was detected in air samples collected 

from 3 national parks in 2003 and 2004. At Mount Revelstoke National park, measured 

concentrations ranged 6-17 pg/m3. At Yoho National park, measured concentrations ranged 2-5 

pg/m3. At Observation Peak in Banff National Park, measured concentrations of PCNB ranged 

0.4-1.3 pg/m3 (Daly et al. 2007; Table 47). 

Yoho National park, British Columbia 

Banff National Park, Alberta 

Page 50 of 70 

Summer 1994 

2003-2004 

2003-2004 

2003-2004 

30-380 

6-17 

Thompson et al., 1997 

Daly et al. 2007 

2-5 

0.4-1.3 

Daly et al. 2007 

Daly et al. 2007 
The detection of PCNB in the atmosphere over areas in which the pesticide was ,not used is 

evidence of the possibility for long-range transport of the compound. 

Available monitoring data for the major degradate PCB are not presented here as PCNB is not 

the single source for these compounds in the environment and the available monitoring data 

could not be linked to the use of PCNB. Air monitoring data could not be located for PCTA and 

PCA. 

Measured concentrations of PCNB, PCTA and PCA in soil, sediment and biota located in areas 

removed from treatment sites have not been identified. 

5.3. Modeling Long-Range Transport Potential 

The "OECD Pov and LRTP Screening Tool" (version 2.0~) was used in evaluating the overall 

persistence (Pov), and LRTP of PCNB and its major degradates. The OECD Tool requires 

estimated degradation half lives in soil, water and air, and partition coefficients between air and 

water and between octanol and water as chemical-specific input parameters to calculate 

persistence and the metrics of LRTP. 

In the OECD tool, overall persistence is estimated based on a chemical's degradation rate 

constants in soil, water and air. The resulting value represents the combined effect of degradation 

in every medium (soil, water, air) and represents the overall degradation of the chemical in the 

environment; it is determined by the slowest responding medium (Scheringer et al., 2006). 

The LRTP of a chemical is based on two metrics: the characteristic travel distance (CTD) and 

the transfer efficiency (TE). CTD represents the potential of a chemical to be transported over 

long distances in air or water. In the OECD Tool, CTD is the distance at which the concentration 

of chemical decrease to 37% due to transport of chemical by a constant flow of air (wind speed 

of 0.02 mls) or water (ocean water circulation speed of 0.02mIs (Scheringer et al., 2006). For 

example, volatile chemicals that are highly persistent in air have high CTD values. TE is a 

dimensionless metric of the potential for atmospheric transport and deposition of parent 

compound in terrestrial and aquatic environments of a remote region (Wegmann et al., 2007). It 

is a ratio between the depositional flux (mollday) in remote region and emission fldx from the 

source area. TE values greater than 100% are possible since some chemicals may undergo 

several cycles of deposition and revolatilization during their residence time in the environment 

(i. e., the "grasshopper effecty'; Wagmann et a1 ., 2007). 

Results fiom the OECD Tool do not indicate absolute loading of pesticides in the environment 

but help to compare the inherent characteristics with reference pesticides identified by the 

Stoclcholm Convention as Persistent Organic Pollutants (POPS) according to their overall 

persistence, CTD and TE. In this case, Aldrin and HCB are used as reference chemicals. 

Modeling results for PCNB and its (major) degradates are compared to those of aldriq and HCB. 

HCB was selected as a reference POP since it has a similar structure compared to PCNB and it is 

4 Available online at: http://www.oecd.org/documentl17/0,3343,en~2649~34373~40754961~1~1~1~1,00.html 

Page 5 1 of 70 
a contaminant of technical PCNB. Input parameters for aldrin, HCB, PCNB and its major 

degradates are provided in Table 48. 

2 Calculated using EPISUITE v.4.0. 

3~stimated using Aopwin of EPISUITE 4 Input parameter to PRZWEXAMS for aerobic aquatic metabolism half-life (Table 43) 

5 PRZMJEXAMS input parameter for aerobic soil metabolism half-life (Table 43) 

Table 48. Physicochemical and environmental fate properties used as input for estimating 

overall persistence and long-range transport potential for selected POPS and PCNB and its 

major degradates using the OECD Tool. 

By comparison, PCNB and its degradates have similar overall persistence compared to HCB, and 

longer overall persistence compared to aldrin (Table 49). 

Name of 

Chemical 

The CTD of PCNB (1 o4 km) and PCB (1 o4 krn) are on a similar order of magnitude compared to 

HCB (10~-10' km). CTD values for PCA and PCTA an order of magnitude lower than that of 

PCNB; however, the CTD of PCNB and its major degradates exceed that of aldrin by at least 2 

orders of magnitude (Table 49). Based on these model results, PCNB and PCA have similar 

LRTP compared to HCB. PCNB and its major degradates have greater LRTP than aldrin. 

The TE of PCNB (235%) is on a similar order of magnitude compared to HCB (229-1 1,300%). 

TE values for PCNB's major degradates are 1-3 orders of magnitude lower PCNB. Compared to 

aldrin, PCNB has an estimated TE that is 3 orders of magnitude greater. PCA and PCTA have 

estimated TE values that are 1 order of magnitude greater than aldrin. PCB has a TE that is 2 

orders of magnitude greater than aldrin (Table 49). Based on these model results, PCNB has a 

similar LRTP compared to HCB. PCNB and its major degradates have similar or greater LRTP 

than aldrin. 

Table 49. Overall persistence and characteristic travel distances generated using the OECD 

Tool. 

Molecular 

Weight Log KO, 

P 

Log KAw 

6.38-6.86 -1.57-(-1.10) 

Page 52 of 70 

'parameter values based on reference chemical data in OECD tool. 

Olrs) 

0.905-9.05 

7134-71340 

147g3 

96.g3 

106~ 

2220~ 

HCB 

PCNB 

PC A 

PCTA 

PCB 

Chemical 

Half life 

in Air 

( hrs) 

846-8460 

10800-108000 

540004 

540004 

540004 

540004 

284.8 

295.3 

265.4 

296.4 

250.3 

Overall Persistence 

(Days) 

(hrs) - 1210-12100 

10800-108000 

,27000~ 

270005 

270005 

27000' 

Half life 

in Water 

Half life 

in Soil 

5.49-5.97 

5.03~ 

4.~2~ 

5.~2~ 

5 .222 

Characteristic Travel 

Distance (km) 

-1.62-(-1.14) 

-2. 742 

-4.762 

-2.84' 

-1.54~ 

Transfer 

Efficiency (%) 
6. Summary and Conclusions 

Aldrin 

HCB 

PCNB 

PC A 

PCTA 

PCB 

This assessment investigated influences on previous risk conclusions attributed to assumptions of 

PRZMIEXAMS as these assumptions relate to persistent chemicals. The results of this 

assessment indicate that inclusion of pesticide burial, alteration of equilibrium partitioning of 

PCNB between aqueous and sorbed phases (on entering soil particles) and mass transfer between 

the water column and the benthic compartment do not alter the risk conclusions of the previous 

ecological risk assessment for PCNB that was conducted for the RED. Therefore, use of PCNB 

poses acute and chronic risk to freshwater fish and invertebrates, acute risk to estuarinelmarine 

invertebrates, and chronic risk to estuarinelmarine fish and invertebrates. 

This assessment expands upon previous conclusions that PCNB and its degradates 

bioaccumulate in aquatic organisms. This is accomplished using available bioconcentration data 

for PCNB and modeling results from KABAM. The results of this assessment indicate that 

PCNB and its degradates and contaminants accumulate in tissues of aquatic organisms. 

Mammals consuming aquatic organisms have the potential to experience chronic effects due to 

exposures to PCNB and its degradates in aquatic forage items from uses of PCNB on turf, 

cabbage, peanuts, cotton and potatoes. Use of PCNB on turf poses a risk of chronic effects to 

birds, terrestrial-phase amphibians and reptiles consuming aquatic organisms. Contaminants of 

technical PCNB, including hexachlorobenzene and polychlorinateddibenzodioxins and 

polychlorinated dibenzofurans are also expected to bioaccumulate in aquatic systems. These 

contaminants pose risk of chronic effects to mammals consuming aquatic organisms. 

7 1.7-689 

607-6040 

1400 

2600 

1490 

1073 

In previous ecological risk assessments of PCNB, bioaccumulation of PCNB and its degradates 

in terrestrial organisms was not considered. Based on the estimated octanol-air and octanol-water 

partition coefficients for PCNB and its degradates, PCNB and its degradates have the potential to 

bioaccumulate in terrestrial ecosystems. Estimated concentrations of PCNB and its degradates in 

earthworms are two orders of magnitude higher than concentrations in soil, indicating that PCNB 

and its degradates can accumulate in soil-dwelling organisms inhabiting fields treated with 

PCNB. Available studies with terrestrial plants (i.e., crops) and animals indicate that PCNB is 

metabolized by terrestrial organisms; however, all metabolites that were identified were polychlorinated phenyl compounds, which are of toxicological concern. At this time, OPP has no tool 

available to assess bioaccumulation in terrestrial food webs (beyond earthworms). Therefore, the 

extent of bioaccumulation of PCNB in terrestrial ecosystems cannot be quantified bv EFED at 

this time and risks to terrestrial animals cannot be precluded. 

Page 53 of 70 

62.7-188 

94900-6 16000 

24400 

3900 

2131 

43400 

0.001-0.19 

229-1 1300 

235 

2.65 

2.11 

71.5 
In addition to bioaccumulation, this assessment considers the ability of PCNB and its degradates 

to move to non-target sites via long range transport. The volatility of PCNB coupled with its 

likely persistence in the atmosphere allow for potential long-range atmospheric transport of 

PCNB. Detections of PCNB in the atmosphere over areas in which the pesticide was not used 

provide evidence of the possibility for long-range transport. Modeling indicates that PCNB has 

comparable or higher long range transport potential compared to chemicals that are known to 

move via long range transport. 

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MRID 40618001. Grimes, J.; Jaber, M. (1988) PCNB: An Acute Oral Toxicity Study with the Bobwhite: Final 

Report: Project No. 117-157. Unpublished study prepared by Wildlife International Ltd. 39 p. 

MRID 4061 8004. Surprenant, D. (1988) Acute Toxicity of Pentachloronitrobenzene Technical to Bluegill (Lepomis 

macrochirus) Under Flow-through Conditions: Report No. 88-4-2697; Study No. 4 1.1 187.6 108.105. Unpublished 

study prepared by Springborn Life Sciences, Inc. 37 p. 

MRID 40652602. Fletcher, D. (1988) Technical Grade PCNB: 9-day Acute Dietary LC50 Study in Bobwhite Quail: 

Rept. No. 88 QC 108. Unpublished study prepared by Bio-Life Associates, Ltd. 29 p. 

Page 56 of 70 
MRID 40652603. Fletcher, D. (1988) Technical Grade PCNB: 9-day Acute Dietary LC50 Study in Mallard 

Ducklings: Rept. No. 88 DC 107. Unpublished study prepared by Bio-Life Associates, Ltd. 29 p. 

MRID 40832301. Suprenant, D. (1988) Acute Toxicity of Pentachloronitrobenzene Tec- hnical to Mysid Shrimp 

(Mysidopsis bahia) Under Flow-through Co- nditions: SLS Report #88-6-2748: SLS Study #41.1187.6109.5 15. 

Unpublished study prepared by Springborn Life Sciences, Inc. 38 p. 

MRID 40865301. Bowman, B. (1988) Determination of the Hydrolysis Rate of ?Carbonl- PCNB: Project ID. 36821. 

Unpublished study prepared by Analyti- cal Bio-Chemistry Laboratories, Inc. 304 p. 

MRID 40882902. Surprenant, D. (1988) Acute Toxicity of Pentachloronitobenzene (PCNB) to Eastern Oysters 

(Crassostrea virginica) Under Flow- through Conditions: Project ID: SLS Report No. 88-6-2760; SLS Study No. 

11857.0488.6101.504. Unpublished study prepared by Springborn Life Sciences, Inc. 43 p. 

MRID 40882903. Surprenant, D. (1988) Acute Toxicity of Pentachloronitrobenzene to Sheepshead Minnow 

(Cyprinodon variegatus) Under Flow-through Conditions: Project ID: Report No. 88-7-2764; SLS Study No. 

1 1857.0488.6 100.505. Unpublished study prepared by Springborn Life Sciences, Inc. 39 p. 

MRID 40972601. Bowman, B.; Fennessey, M. (1988) Determination of the Hydrolysis Rate of ?Carbon 141-PCNB: 

ABC Final Rept. #36005. Unpublished study prepared by Analytical Bio-Chemistry Laboratories, Inc. 50 p. 

MRID 40992701. Swigert, J. (1988) Acute Flow-through Toxicity of PCNB to Rainbow Trout (Salmo gairdneri): 

Final Report #36829. Unpublished study prepared by Analytical Bio-Chemistry Laboratories, Inc. 279 p. 

MRID 41004801. Carpenter, M.; Bowman, B. (1988) Photodegradation Study of ?carbon 141-PCNB on Soil 

Surface: ABC Final Report No. 36823. Unpu- blished study prepared by Analytical Bio-Chemistry Laboratories, 

Inc. 3 13 p. 

MRID 41178001. Bowman, B. (1989) Laboratory Volatility from Soil of PCNB: ABC Final Report #37090. 

Unpublished study prepared by Analytical Bio-Chemistry Laboratories, Inc. 3 11 p. 

MRID 41200001. Burgess, D. (1989) Uptake, Depuration and Bioconcentration of Carbon 14-PCNB by Bluegill 

Sunfish (Lepomis rnacrochirus): Rept. # 36872. Unpublished study prepared by Analytical Bio-Chemistry 

Laboratories, Inc. 346 p. 

MRID 41203602. Daly, D. (1989) Anaerobic Soil Metabolism of ?Carbon - 141-Penta- chloronitrobenzene: Final 

Report No. 35905. Unpublished study prepared by Analytical Bio-Chemistry Laboratories, Inc. 49 p. 

MRID 41332801. Beavers, J.; Foster, J.; Lattin, A.; et al. (1989) Pentachloronitrobenzene (PCNB): A Onegeneration Reproduction Study with the Bobwhite (Colinus virginianus): Lab Project Number: 1171161. 

Unpublished study prepared by Wildlife International Ltd. 1 13 p. 

MRID 41332802. Beavers, J.; Foster, J.; Lattin, A.; et al. (1989) Pentachloronitrobenzene (PCNB): A Onegeneration Reproduction Study with the Mallard (Anas platyrhynchos): Lab Project Number: 1171162. Unpublished 

study prepared by Wildlife International Ltd. 115 p. 

MRID 41384301. Cranor, W.; Patterson, C. (1989) Anaerobic Soil Metabolism of ?Car- bon 141- 

pentachloronitrobenzene: ABC Final Report #36825. Un- published study prepared by Analytical Bio-Chemistry 

Labora- tories, Inc. 759 p. 

MRID 4 138450 1. Cranor, W. (1 989) Aerobic Soil Metabolism of ?Carbon 141-penta- chloronitrobpzene: ABC 

Final Report # 36824. Unpublished study prepared by Analytical Bio-Chemistry Laboratories, Inc. 1088 p. 

Page 57 of 70 
MRID 41443101. Kuhn, J. (1989) Acute Oral Toxicity Study in Rats: Technical Grade PCNB 95%: Lab Study 

Number: 6085-89. Unpublished study prepared by Stillmeadow, Inc. 11 p. 

MRID 41648201. Dykes, J. (1990) Soil Adsorption/Desorption with ?Carbon 141-PCNB: Lab Project Number: 

38405. Unpublished study prepared by Analytical Bio-Chemistry Laboratories, Inc. 509 p. 

MRID 41686001. Cranor, W.; Patterson, C. (1990) Amended Final Report to: Anaerobic Soil Metabolism of 

?carbon 141-Pentachloronitrobenzene, MRID 41- 384301: Lab Project Number: #36825. Unpublished study 

prepared by Analytical Bio-Chemistry Laboratories, Inc. 49 p. 

MRID 4 17 1320 1. Kabler, K. (1990) Photodegradation Study of ?C 141-PCNB on Soil Surface: Supplement to 

MRID 4 100480 1 : Lab Project Number: 36823 1. Unpublished study prepared by Analytical Bio-Chemistry Labs, 

Inc. 129 p. 

MRID 4 17 13202. Cranor, W. (1 990) Aerobic Soil Metabolism of ?C 141-Pentachloro- nitrobenzene: Supplement to 

MRID 41384501: Lab Project Number: 368241. Unpublished study prepared by Analytical Bio-Chemistry Labs, 

Inc. 1 17 p. 

MRID 41795702. Feiler, W. (1991) PCNB: Physical And Chemical Characteristics: Unpublished study prepared by 

Amvac Chemical Co. 76 p. 

MRID 4 19 1870 1. Schardein, J. (1 99 1) PCNB: Two-Generation Reproduction Study in Rats: Lab Project Number: 

399-086. Unpublished study prepared by International Research and Development Corp. 633 p. 

MRID 41951701. Halls, T. (1991) Characterization of carbon 14 -PCNB Residues in Water and Bluegill (Lepomis 

macrochirus) Tissues: Lab Project Number: 37024. Unpublished study prepared by ABC Labs, Inc. 58 p. 

MRID 42094401. White, C. (1991) Reply to EPA Rejection of PCNB Anaerobic Soil Metabolism Study MRID 

#41203602. Unpublished study prepared by Uniroyal Chemical Co., Inc. 18 p. 

MRID 42112801. Cady, C.; Cranor, W. (1991) Supplement to: Aerobic Soil Metabolism of Carbon 14- 

Pentachloronitrobenzene on Sandy Loam Soil: Lab Project Number: 368242. Unpublished study prepared by ABC 

Labo- ratories, Inc. 270 p. 

MRID 42112802. Cady, C.; Cranor, W. (1991) Supplement to: Anaerobic Soil Metabol- ism of Carbon 14- 

Pentachloronitrobenzene on Sandy Loam Soil: Lab Project Number: 368251. Unpublished study prep&ed by ABC 

Laboratories, Inc. 264 p. 

MRID 42336201. Horree, D. (1992) Aqueous Photolysis of PCNB: Lab Project Number: 9127. Unpublished study 

prepared by Uniroyal Chemical Co., Inc. 5 1 p. 

MRID 4260620 1. Bashir, M. (1992) Aqueous Photolysis of (carbon 14)-Pentachloronitrobenzene: Lab Project 

Number: 368223. Unpublished study prepared by ABC Labs, Inc. 9 18 p. 

MRID 42606202. Bashir, M. (1992) Aqueous Photolysis of (carbon 14)-Pentachloronitrobenzene: Lab Project 

Number: 368223A. Unpublished study prepared by ABC Labs, Inc. 105 p. 

MRID 4291 1902. Misra, B. (1993) Aerobic Soil Metabolism of Pentachloronitrobenzene (PCNB): Lab Project 

Number: ME 9100 13 1. Unpublished study prepared by Pittsburgh Environmental Research Lab., Inc. 89 p. 

MRID 43 17930 1. Vithala, R. (1 994) PCNB Metabolite Characterization in Fish and Water Samples from a FlowThrough Bluegill Bioconcentration Study: Review in Conjunction with MRID 40580202: Lab Project Number: 

92 13 1: 40366. Unpublished study prepared by ABC Labs., Inc. and Uniroyal Chemical Co., Inc. 13 1 p. 

Page 58 of 70 
MRID 43751 101. Merricks, D.; Jensen, M. (1995) PCNB Field Volatility Study: Lab Project Number: 1919: 9234: 

92-109. Unpublished study prepared by Agrisearch Inc. 143 p. 

Page 59 of 70 
Appendix A. Octanol-water Partitioning Coefficients of PCNB and its Degradates 

The predictions of the bioaccumulation portion of KABAM are most sensitive to the octanolwater partition coefficient (Kow) value selected to represent a chemical. Therefore the accuracy 

of this parameter influences the uncertainties and certainties associated with model predictions of 

concentrations of PCNB in tissues of aquatic organisms resulting from bioaccumulation. 

In a registrant-submitted study (MRID 41795702), the Kow of PCNB was calculated using the 

HPLC retention time correlation method. Following this method, retention times were calculated 

for 6 reference chemicals with known Kow values (specifically: benzene, bromobenzene, 

biphenyl, bibenzyl, DDE and hexachlorobenzene). Note that several of the reference chemicals 

were organochlorines. A log linear relationship (R~ = 0.98) was then derived where retention 

time was related to Kow. The log linear relationship was then used to translate the experimental 

retention time of PCNB into an estimate of Kow. The resulting Log Kow of PCNB was 5.0. 

The registrant-submitted Kow estimate for PCNB is consistent with literature values that were 

experimentally derived using the HPLC retention time correlation method (Log Kow range: 5.01- 

5.30; Table Al). Note that the other studies using the HPLC retention time correlation method 

used different sets of reference chemicals to derive log linear relationships between retention 

time and Kow. The registrant-submitted value is also consistent with the EPISuite (USEPA 

2008) estimate of 5.03, which was determined using the atomlfiagment contribution method. 

Several studies are available in the literature that report Kow values for PCNB that were 

calculated using the shake flask method. These values are lower than the registrant submitted 

Log KO, value of 5.0 (range: 4.22-4.77; Table Al). In general, the shake flask method is useful 

for chemicals with Log KO, values below 5, but becomes less accurate for chemicals with Log 

KO, values above 5 (USEPA 2003). Despite this, the Kow values calculated using the shake 

flask method are still within an order of magnitude of the registrant submitted value. 

Table Al. Available Kow data for PCNB. 

I Kanazawa 198 1 I Shake flask 1 16.552 1 4.22 1 

Source 

I Gever et al. 1984 I I I I Shake flask (OECD Guideline 107. 1981) 1 43.652 1 4.64 1 I Niimi et al. 1989 I I I I Shake flask WSEPA 60014-79-032) 1 58.884 1 4.77 1 

Method 

I - - 1 Kawamoto and Urano 1989 1 HPLC retention time correlation I I 

1 151.000 1 5.18 1 

Kow Log Kow 

I 

The mean of all of the experimentally derived Kow values provided in Table A1 (including the 

shake flask and HPLC retention time correlation methods) is 104,000, which is equivalent to a 

Log KO, of 5.0. 

100,000 

102,329 

107.152 

MRID 4 1795702 

Nakamura et al. 200 1 

USEPA 2007 

McDuffie 198 1 

Donovan and Pescatore 2002 

Page 60 of 70 

5.00 

5.01 

5.03 

HPLC retention time correlation (EPA TSCA 

guideline) 

HPLC retention time correlation 

QSAR (atomlfiament contribution method) 

HPLC retention time correlation 

HPLC retention time correlation 

162,18 1 

199,526 

5.21 

5.30 
Based on the above information, a Log KO, of 5.0 was selected as a representative value for 

PCNB. This value is used in this assessment to estimate the bioaccumulation potential of PCNB. 

Since this assessment is also relevant to PCNB's degradates, it is necessary to understand the 

partitioning of the residues. Log KO, values for PCNB's degradates were estimated using 

EPISuite (USEPA 2008) and are provided in Table A2. PCA, the major environmental 

degradate of PCNB, has a lower estimated Log KO, value compared to PCNB. This indicates that 

PCA would accumulate in aquatic organisms less than PCNB. However; PCTA, which has been 

identified as a major degradate in fish BCF studies, has a higher estimated Log KO,, indicating 

that PCTA may accumulate more in aquatic organisms compared to PCNB. 

Table A2. Estimated Log Kow values for PCNB and its degradates. 

Residue I Abbreviation I Estimated Log K~~~ 1 

I pentachloronitrobenzene I PCNB' I 5.0 I 

pentachloroaniline 

pentachlorothioanisole 

~entachlorobenzene 

Estimated using EPISUITE v. 4.0 (USEPA 2008). 

pentachlorothioanisole sulfoxide 

pentachlorothioanisole sulfone 

References 

Donovan, S.F. and M.C. Pescatore. 2002. Method for measuring the logarithm of the octanol-water partition 

coefficient", J. Chromatogr. A 952,47-61. 

PCA' 

PCTA' 

PCB 

Geyer, H., G. Politzki, and D. Freitag. 1984. Prediction of Ecotoxicological Behaviour of Chemicals: Relationship 

Between N-OctanolIWater Partition Coefficient and Bioaccumulation of Organic Chemicals by Alga Chlorella. 

Chemosphere 13(2):269-284 

4.3 

5.8 

5.2 

'~dentified in fish tissue. 

PCTASO' 

PCTASOz 

Kanazawa, J. 198 1 a. Measurement of the Bioconcentration Factors of Pesticides by Freshwater Fish and Their 

Correlation with Physicochemical Properties or Acute Toxicities. Pestic.Sci. 12(4):417-424. 

3.7 

3.8 

Kawamoto, K. and K. Urano. 1989. Parameters for predicting fate of organochlorine pesticides in the environment. 

I. Octanolwater and air-water partition coefficients,Chemosphere 18(9-lo), 1987-1996. 

McDuffie, B. 198 1. Estimation of octanollwater partition coefficients for organic pollutants using reverse-phase 

HPLC, Chemosphere 10(1), 73-83. 

MRID 4 1795702. Feiler, W. (1 99 1) PCNB: Physical And Chemical Characteristics: Unpublished study prepared by 

Amvac Chemical Co. 76 p. 

Nakamura, M., Suzuki, T. Ammo, K. and S. Yamada. 2001. Relation of sorption behavior of agricultural chemicals 

in solid phase extraction with their octanol-water partition coefficients evaluated by HPLC, Anal. Chim. Acta 

428(2), 219-226 (2001). 

Niimi, A.J, Lee, H.B., and G.P. Kissoon. 1989. Octanollwater partition coefficients and biococnetration factors of 

chloronitrobenzenes in rainbow trout (Salmo gairdneri). Environmental Toxicology and Chemistry; 8: 8 17-823. 

USEPA. 2008. EPI SuiteTM v4.0. United States Environmental Protection Agency. 

Page 61 of 70 
Appendix B. Open literature review summaries for bioconcentration studies involving 

PCNB 

On 9/16/09, ECOTOX (htt~:/lcfpub.e~a.~ovlecotox/) was searched for aquatic "accumulation" 

studies relevant to PCNB. The following list of studies were returned by ECOTOX: 

ECOTOX # Citation: 

378 Freitag, D., H. Geyer, A. Kraus, R. Viswanathan, D. Kotzias, A. Attar, W. Klein, and F. Korte. 

1982. Ecotoxicological Profile Analysis VII. Screening Chemicals for Their Environmental 

Behavior by Comparative Evaluation. Ecotoxicol.Environ.Saf. 6:60-81. 

5113 Niimi, A.J, Lee, H.B., and G.P. Kissoon. 1989. Octanol/water partition coefficients and 

biococnetration factors of chloronitrobenzenes in rainbow trout (Salmo gairdneri). Environmental 

Toxicology and Chemistry; 8: 8 17-823. 

7079 Korte, F., D. Freitag, H. Geyer, W. Klein, A.G. Kraus, and E. Lahaniatis. 1978. A Concept for 

Establishing Ecotoxicologic Priority Lists for Chemicals. Chemosphere 7(1):79-102. 

9146 Schauerte, W., J.P. Lay, W. Klein, and F. Korte. 1982. Long-Tern Fate of Organochlorine 

Xenobiotics in Aquatic Ecosystems. Distribution, Residual Behavior, and Metabolism of 

Hexachlorobenzene. Ecotoxicol.Environ.Saf. 6:560-569. 

10750 Kanazawa, J. 1983. A method of predicting the bioconcentration potential of pesticides using fish. 

JARQ, 17(3), 173-179. 

11297 Geyer, H., G. Politzki, and D. Freitag. 1984. Prediction of Ecotoxicological Behaviour of 

Chemicals: Relationship Between N-OctanoVWater Partition Coefficient and Bioaccumulation of 

Organic Chemicals by Alga Chlorella. Chemosphere 13(2):269-284 

12534 Kanazawa, J. 198 1b. Bioconcentration potential of pesticides by aquatic organisms. Japan pesticide 

information; 39, 12-16. 

14353 Oliver, B.G., and A.J. Niimi. 1985. Bioconcentration Factors of Some Halogenated Organics for 

Rainbow Trout: Limitations in Their Use for Prediction of Environmental Residues. 

Environ.Sci.Techno1. 19(9):842-849. 

15599 Kanazawa, J. 1981a. Measurement of the Bioconcentration Factors of Pesticides by Freshwater 

Fish and Their Correlation with Physicochemical Properties or Acute Toxicities. Pestic.Sci. 

12(4):417-424. 

17318 Freitag, D., J.P. Lay, and F. Korte. 1984. Environmental Hazard Profile - Test Results as Related to 

Structures and Translation into the Environment. In: K.L.E.Kaiser (Ed.), QSAR in Environmental 

Toxicology, Proc.of the Workshop held at McMaster University, Hamilton, Ont., Aug.16-18, 1983, 

D.Reide1 Publ.Co., Dordrecht, Netherlands : 1 1 1-13 1 

59925 Kanazawa, J. 1980. Prediction of biological concentration potential of pesticides in aquatic 

organisms. Rev. Plant Protec. Res. 13,27-36. 

The reviews of these studies are provided below 

Page 62 of 70 
Open Literature Review Summary 

Chemical Name: pentachloronitrobenzene (PCNB) (CAS # 82-68-8) 

ECOTOX Record Numbers and Citations: 

ECOTOX # 3781. Freitag, D., H. Geyer, A. Kraus, R. Viswanathan, D. Kotzias, A. Attar, W. Klein, and F. Korte. 

1982. Ecotoxicological Profile Analysis VII. Screening Chemicals for Their Environmental Behavior by 

Comparative Evaluation. Ecotoxicol.Environ.Saf. 6:60-8 1. 

ECOTOX # 11297. Geyer, H., G. Politzki, and D. Freitag. 1984. Prediction of Ecotoxicological Behaviour of 

Chemicals: Relationship Between N-OctanolIWater Partition Coefficient and Bioaccumulation of Organic 

Chemicals by Alga Chlorella. Chemosphere 13(2):269-284 

ECOTOX # 17318. Freitag, D., J.P. Lay, and F. Korte. 1984. Environmental Hazard Profile - Test Results as 

Related to Structures and Translation into the Environment. In: K.L.E.Kaiser (Ed.), QSAR in Environmental 

Toxicology, Proc.of the Workshop held at McMaster University, Hamilton, Ont., Aug.16-18, 1983, D.Reide1 

Publ.Co., Dordrecht, Netherlands : 1 1 1-1 3 1 

Purpose of Review: RED follow up 

Date of Review: September 16,2009 

Summary of Study Findings: 

One of the purposes of this study was to develop Bioconcentration Factors (BCFs) for algae and for fish. All three 

ECOTOX references reported the results of a study where green algae (Chlorella fusca) were exposed to 50 yglL 14 C-labeled PCNB and maintained at room temperature (20-25°C). Algae were tested in 500 mL Erlenmeyer flasks, 

with glass stoppers. After a 24 hour exposure period, 14c residues in algae and in water were measured, with 67% in 

algae and 38% in water. The resulting BCF was 3,100 based on wet-weight (units: (pglg-ww)l(pglmL)). 

In addition, Greitag et al. 1982 and 1984 reported results of a study involving the bioconcentration of PCNB in 

golden orfs (Leuciscus idus melanotus). In the study, 5 fish were exposed to 0.4 pglL 14c-labeled PCNB for 3 days 

at room temperature (20-25OC). Fish were approximately 1.5 g and were maintained in a 12.5 L flask containing 10 

L of test solution. Fish were not fed during the exposure period and the test solutions were not aerated. The 

resulting BCF value was 1140 (Freitag et al. 1982 and 1984) (units: (pglg-ww)l(pglmL)). 

Description of Use in Document: Qualitative 

Rationale for Use: For characterization of bioaccumulation potential of PCNB in aquatic ecosystems 

Limitations of Study: 

Potential degradation of PCNB in algae and in fish is not discussed in the articles, however; since 14c residues were 

measured, residues of PCNB are included in the reported BCF values. In addition, lipid compositions of the test 

organisms, which can affect bioconcentration results, were not reported by the study authors. 

Reviewer comments: 

1) Comparison of study design and results reported in the 3 studies cited here indicates that these publications report 

the results (relevant to algae and fish) of the same study. 

2) This study also included data for 34 other chemicals. Only information relevant to PCNB was reviewed. 

3) This study included information where chemical degradation by activated sludge was examined. This part of the 

study was not reviewed. 

4) This study included information where laboratory rats were dosed with PCNB and retention and elimination of 

PCNB was examined. This part of the study was not reviewed. 

5) ECOTOX # 11297 also included results of an octanol-water partition coefficient (Kow) study conducted using the 

shake flask method (according to OECD guideline 107, dated 1981). The resulting Log Kow was 4.64. 

Reviewer: Kristina Garber, Biologist, ERB4 

Page 63 of 70 
Open Literature Review Summary 

Chemical Name: pentachloronitrobenzene (PCNB) (CAS # 82-68-8) 

ECOTOX Record Number and Citation: 

ECOTOX#7079. Korte, F., D. Freitag, H. Geyer, W. Klein, A.G. Kraus, and E. Lahaniatis. 1978. A Concept for 

Establishing Ecotoxicologic Priority Lists for Chemicals. Chemosphere 7(1):79-102. 

Purpose of Review: RED follow up 

Date of Review: September 16,2009 

Summary of Study Findings: 

One of the purposes of this study was to develop Bioconcentration Factors (BCFs) for algae and for fish. 

This article reported the results of a study where green algae (Chlorella fusca) were exposed to 49 pgL 14c-labeled 

PCNB and maintained at room temperature (20-25°C). Algae were tested in 250 mL round-bottom flasks, with glass 

stoppers. After a 24 hour exposure period, 14c residues in algae and in water were measured. Two BCFs were 

reported: 14,000 and 22,000 based on dry-weight (units: (pg/g-dw)/(pg/mL)). Geyer et al. 1984 (ECOTOX #11297) 

report that C. fusca is approximately 1 g dry weight to 5 g wet weight. Using this conversion, the BCF values 

reported in this study correspond to 2800 and 4400, respectively, on a wet-weight basis (units: (pglg-ww)/(pg/mL)). 

This article also reported results of a study involving the bioconcentration of PCNB in golden orfs (Leuciscus idus 

melanotus). In the study, 5 fish were exposed to 14c-labeled PCNB for 3 days at room temperature (23~t3'C). Fish 

weighed approximately 2-5 g and were maintained in a 12 L flask (capped) containing 10 L of test solution. Fish 

were not fed during the exposure period and the test solutions were not aerated. Three test concentrations were used: 

33, 6 and 0.4 pgL. Toxicity was observed in the 33 and 6 pg/L levels and therefore, the BCF values from these 

exposure concentrations are not considered useful. The BCF value for the 0.4 pg/L exposure level was 1130 (units: 

(~g/g-ww)/(pg/mL)). 

Description of Use in Document: Qualitative 

Rationale for Use: For characterization of bioaccumulation potential of PCNB in aquatic ecosystems 

Limitations of Study: 

Potential degradation of PCNB in algae and in fish is not discussed in the article, however; since 14c residues were 

measured, residues of PCNB are included in the reported BCF values. In addition, lipid compositions of the test 

organisms, which can affect bioconcentration results, were not reported by the study authors. 

Reviewer comments: 

1) The study design is similar to that of ECOTOX#s 3781,11297 and 173 18. 

2) This study also included data for 3 several other chemicals. Only information relevant to PCNB was reviewed. 

3) This study included information where chemical degradation by activated sludge was examined. This part of the 

study was not reviewed. 

4) This study included information where laboratory rats were dosed with PCNB and retention and elimination of 

PCNB was examined. This part of the study was not reviewed. 

Reviewer: Kristina Garber, Biologist, ERB4 

Citation: 

ECOTOX # 11297. Geyer, H., G. Politzki, and D. Freitag. 1984. Prediction of Ecotoxicological Behaviour of 

Chemicals: Relationship Between N-OctanolIWater Partition Coefficient and Bioaccumulation of Organic 

Chemicals by Alga Chlorella. Chemosphere 13(2):269-284 

Page 64 of 70 
Open Literature Review Summary 

Chemical Name: pentachloronitrobenzene (PCNB) (CAS # 82-68-8) (also called Qunintozene) 

ECOTOX Record Numbers and Citations: 

#59925. Kanazawa, J. 1980. Prediction of biological concentration potential of pesticides in aquatic organisms. Rev. 

Plant Protec. Res. 13,27-36. 

#15599. Kanazawa, J. 1981a. Measurement of the Bioconcentration Factors of Pesticides by Freshwater Fish and 

Their Correlation with Physicochemical Properties or Acute Toxicities. Pestic.Sci. 12(4):417-424. 

# 12534. Kanazawa, J. 198 1 b. Bioconcentration potential of pesticides by aquatic organisms. Japan pesticide 

information; 39, 12-1 6. 

#10750. Kanazawa, J. 1983. A method of predicting the bioconcentration potential of pesticides using fish. JARQ, 

17(3), 173-179. 

Purpose of Review: RED follow up 

Date of Review: September 16,2009 

Summary of Study Findings: 

One of the purposes of this study was to develop Bioconcentration Factors (BCFs) for fish. 

All four ECOTOX references reported the results of a bioconcentration study where wild-caught topmouth gudgeon 

(Pseudorasbora pawa) were exposed to PCNB. Fish weighing 2-5 g were caught from the Inari River (Japan) and 

acclimated for approximately 1 month prior to exposure. Fish were maintained in aerated 20 L tanks with flow 

through systems (300 mllmin) and maintained at a temperature of 20h2"C. Technical grade PCNB was added to 

purified water with acetone as a solvent. Fish (15-20) were exposed to 10-20 pglL PCNB for 14 d, then transferred 

to "clean" water for 30 d. Fish were fed once per day. PCNB concentrations were measured using gas 

chromatography.The resulting BCF for PCNB was 238 based on wet-weight. 

Description of Use in Document: Qualitative 

Rationale for Use: For characterization of bioaccumulation potential of PCNB in aquatic ecosystems 

Limitations of Study: 

Potential degradation of PCNB in fish is not discussed in the articles. Since residues of PCNB were not included as 

analytes, the reported BCF is likely an underestimate of the expected value relevant to total residues of concern. In 

addition, lipid compositions of the test organisms, which can affect bioconcentration results, were not reported by 

the study author. 

Reviewer comments: 

1) Comparison of study design and results reported in the 4 studies cited here indicates that these publications report 

the results of the same study. 

2) This study also included data for several other chemicals. Only information relevant to PCNB was reviewed. 

3) This study also included results of an octanol-water partition coefficient (Kow) study conducted using the shake 

flask method. The resulting Kow was 16,552 (Log Kow = 4.22). 

Reviewer: Kristina Garber, Biologist, ERB4 

Page 65 of 70 
Open Literature Review Summary 

Chemical Name: pentachloronitrobenzene (PCNB) (CAS # 82-68-8) 

ECOTOX Record Numbers and Citations: 

#5113. Niimi, A.J, Lee, H.B., and G.P. Kissoon. 1989. Octanollwater partition coefficients and biococnetration 

factors of chloronitrobenzenes in rainbow trout (Salmo gairdneri). Environmental Toxicology and Chemistry; 8: 

8 17-823. 

Purpose of Review: RED follow up 

Date of Review: September 16,2009 

Summary of Study Findings: 

One of the purposes of this study was to develop Bioconcentration Factors (BCFs) for fish. 

In a bioconcentration study, rainbow trout (Salmo gairdneri) were exposed to 0.69 pg/L PCNB, as well as 17 other 

chloronitrobenzenes for 36 days. Fish weighed 153(*29) g at test initiation and 178(%30) g at test completion. Mean 

lipid content of fish averaged 8.4(&1.4) mglg wet weight (equivalent to 0.84%).BCF values taken at 5, 12, 20, 28, 

and 36 day time periods ranged 114-261 (see Table below), with an overall mean of 171 (339). The authors of this 

study observed that fish concentrations of PCNB reached equilibrium within 5 days, but significant differences in 

BCF values were observed at different time periods. 

BCF values for PCNB at different days of the study. 

Description of Use in Document: Qualitative 

Rationale for Use: For characterization of bioaccumulation potential of PCNB in aquatic ecosystems 

Mean BCF 

Limitations of Study: 

This study design involved exposing fish to 18 chemicals. It is unknown whether or not the mixture of chemicals 

would influence the bioconcentration of PCNB. 

Standard 

deviation 

In addition, potential degradation of PCNB in fish is not discussed in the articles. Since residues of PCNB were not 

included as analytes, the reported BCF is likely an underestimate of the expected value relevant to total residues of 

concern. 

Reviewer comments: 

1) As noted above, this study also included data for several other chemicals. Only information relevant to PCNB 

was reviewed. 

2) This study also included results of an octanol-water partition coefficient (Kow) study conducted using the shake 

flask method. The resulting Log Kow was 4.77. 

Reviewer: Kristina Garber, Biologist, ERB4 

Page 66 of 70 
Open Literature Review Summary 

Chemical Name: pentachloronitrobenzene (PCNB) (CAS # 82-68-8) 

ECOTOX Record Numbers and Citations: 

ECOTOX #14353. Oliver, B.G., and A.J. Niirni. 1985. Bioconcentration Factors of Some Halogenated Organics for 

Rainbow Trout: Limitations in Their Use for Prediction of Environmental Residues. Environ.Sci.Techno1. 

19(9):842-849. 

Purpose of Review: RED follow up 

Date of Review: September 17,2009 

Summary of Study Findings:One of the purposes of this study was to develop Bioconcentration Factors (BCFs) for 

fish. In this bioconcentration study, rainbow trout (Salmo gairdneri) were exposed for different time intervals (7,2 1, 

35, 75 and 96 days) to a mixture of 18 chlorinated and brominated organic chemicals, including PCNB. Fish were 

exposed at either 1.4 or 14 ngIL PCNB. Fish were maintained in "self-cleaning" tanks with a flow rate of 6LImin). 

The temperature was 15OC. At test initiation, 32 fish were placed in the tanks (1 per test concentration). At each time 

interval, 6 fish were removed and analyzed for chemical concentrations. BCF values relevant to each time step are 

provided in the table below. 

Description of Use in Document: Qualitative 

Rationale for Use: For characterization of bioaccumulation potential of PCNB in aquatic ecosystems 

Limitations of Study: This study design involved exposing fish to 18 chemicals. It is unknown whether or not the 

mixture of chemicals would influence the bioconcentration of PCNB. In addition, potential degradation of PCNB in 

fish is not discussed in the articles. Since residues of PCNB were not included as analytes, the reported BCF is likely 

an underestimate of the expected value relevant to total residues of concern. 

50 

75 

96 

Mean 

Reviewer comments: 

1) As noted above, this study also included data for several other chemicals. Only information relevant to PCNB 

was reviewed. 

2) In the publication, the authors indicate that predicted bioconcentration of PCNB is greater than observed 

bioconcentration since the chemical is metabolized rapidly by fish. 

3) There is some confusion regarding the notation associated with the BCF values. The article indicates that all BCF 

values should be x10". However, in Figure 1 of the article, the BCFs are displayed as lo3. Based on the; properties of 

the chemicals tested, and other BCF values for PCNB, it appears that the notation is incorrect. Therefore, the 

results displayed in the table above are reflective of the reviewer's assumption that all BCF values given in the study 

report should be lo3. 

ND = not detected SD = standard deviation *Reviewer calculated 

0.65 (0.47) 

ND 

0.95 (0.53) 

0.59 (0.27) 

Reviewer: Kristina Garber, Biologist, ERB4 

202 (35) 

258 (57) 

3 12 (49) 

237" 

Page 67 of 70 

0.35 (0.08) 

0.09 (0.04) 

0.41 (0.12) 

0.26 (0.15) 

6.9 (2.5) 

6.9 (1.7) 

7.3 (1.5) 

6.7* 

284 (54) 

262 (63) 

288 (57) 

245* 

8.0 (1.3) 

6.7 (1 .O) 

8.0 (1.8) 

7.2" 
Open Literature Review Summary 

Chemical Name: pentachloronitrobenzene (PCNB) (CAS # 82-68-8) 

ECOTOX Record Numbers and Citations: 

ECOTOX # 9146. Schauerte, W., J.P. Lay, W. Klein, and F. Korte. 1982. Long-Term Fate of Organochlorine 

Xenobiotics in Aquatic Ecosystems. Distribution, Residual Behavior, and Metabolism of Hexachlorobenzene. 

Ecotoxicol.Environ.Saf. 6560-569. 

Purpose of Review: RED follow up 

Date of Review: September 21,2009 

Summary of Study Findings:PCNB was applied to a small pond (2-3 m diameter, 0.85 m deep). Five applications 

of 50 pg/L (ppb) 14c PCNB were made during approximately 1 month. Residue concentrations of the 3 chemicals 

were measured in water, sediment, aquatic plants (Lemna minor, Ranunculus aquatilis) and animals (Notonecta 

glauca, Libella quadrimaculata) present in the ponds for up to 166 weeks after the application. The study authors 

observed that the PCNB concentration in the water column decreased by 50% by 1.8 days after the last application. 

They attributed this to adsorption to sediment and biota present in the pond. Measured concentrations of PCNB in 

aquatic organisms were provided in Figure 3 of the article (provided below). Based on this information, it appeared 

that PCNB residue concentrations in aquatic organisms and in sediment were above 1 mglkg (ppm) for several 

months after the last application of PCNB to the pond. PCNB was not detected (detection limit 0.002 mgtkg) in 

aquatic plants at 24 weeks after the last application. 

I1 

1 I 

1 1977 1979 

last 

application 

FIG. 3. PCNB-derived residues in an experimentally polluted smail pond. A, ~otonecfa glauca; B, 

Libella quadrimaculata (larvae); C, Lemna minor; D, Ranunculus aqualiiis; and E, sediment. 

Description of Use in DocumentlLimitations of study: This value has limited use for the PCN~ aquatic 

bioaccumulation assessment because it does not provide measured values of PCNB residues in aquatic organisms in 

a tabular form. Values are only displayed in Figure 3. Because tabular concentrations of PCNB in aquatic 

organisms, the water column and the sediment were not provided, the reviewer could not calculate bioaccumulation 

factors. In addition, the study authors indicated that PCNB was converted to pentachloroaniline and 

pentachlorthioanisole at 30 weeks after application; however, the article did not provide reports assoc$ated with the 

measured concentrations of these degradates. 

Reviewer: Kristina Garber, Biologist, ERE34 

Page 68 of 70 
Appendix C. Use of fugacity approach to estimate pesticide concentrations in earthworms 

located on treated fields 

In order to explore the potential exposures of mammals and birds to pesticides in the soil and 

earthworms on the treatment site, a simple fugacity approach can be employed to estimate 

concentrations of the pesticide of interest earthworms. Fugacity is most often regarded as the 

"escaping tendency" of a chemical from a particular phase. Fugacity (F) has units of pressure, 

generally pascals (Pa), and can be related to phase concentrations. For any particular 

environmental phase (e.g., water, soil, air, or biota) there is a corresponding "fugacity capacity" 

with units of mol/m3-pa and is denoted by Z. The relationship between fugacity, fugacity 

capacity and chemical concentration (C) is defined by Equation 1. 

Equation 1. C = Z * F 

Fugacity capacities for a given chemical are calculated for the phases of interest as part of the 

exposure point estimation methodology (Mackay and Paterson 1981). The following 

calculations of fugacity capacities for soil (Zs) and earthworms (ZE) (Equations 2 and 3, 

respectively) require several chemical-specific parameters and assumptions of system 

temperature (25OC) and steady state equilibrium. Parameter values relevant to Equations 2 and 3 

are defined in Table C 1. 

Equation 2. Zs = Kd * PS 

H 

Equation 3. Z, = L*Kow 

H 

Fugacity capacities for a given chemical are calculated for the phases of interest as part of the 

exposure point concentration estimation methodology. By definition, the ratio between Z values 

of different phases (compartments) equals the partitioning coefficient (e.g., Equation 4). 

Zoc tan ol Equation 4. - - Kow 

'water 

In this approach, it is assumed that a pesticide partitions between the soil, the (pore) water and 

the air contained within the soil of the treatment site. It is assumed that earthworms dwelling 

within the soil are exposed to a pesticide via ingestion of contaminated soil. The concentration 

of a pesticide in earthworm tissues can be calculated according to Equation 5 (see Table Cl for 

parameter definitions). 

Equation 5. C, = C, * -& ES I 

Page 69 of 70 
I CE 1 Chemical concentration in earthworm tissue I 

Table C1. Summary of parameters relevant to earthworm fugacity model. 

I H I Henry's Law constant I m3-palm01 I 

Symbol Units 

CE' 

cs 

I Kd I Soil partitioning coefficient I cm3/g 

Definition 

I Kow I Octanol to water partition coefficient I none I 

Chemical concentration in earthworm tissue 

Chemical concentration in soil 

\ L I Lipid fkaction of earthworm I none I 

g/kg 

mol/m3 

I MW I molecular weight of chemical / glmol I 

I ZF I Fuaacity capacity of pesticide in earthworms I mol/m3-pa I 

zs I Fugacity capacity of pesticide in soil I mol/m3-pa 

Equation 5 can be redefined using equations 2 and 3 as follows in Equation 6. Equation 6 is used 

to calculate the concentration of a pesticide in earthworms inhabiting the soil of treatment sites. 

PE 

PS 

C, *L*K,, Equation 6. C, = 

Kd * Ps 

Cs is intended to be representative of the steady-state concentrations of the pesticide of interest in 

soil. This value is calculated using PRZM. Kd and Kow are chemical-specific parameters. Kd 

was chosen to be consistent with the value input into PRZM (15.5 cm31g). ps is dependant upon 

the soil properties of the selected PRZM scenario used to derive Cs. A value of 1.65 g/cm3 was 

selected to represent ps. L is based on the lipid content of earthworms, which was assumed to be 

0.01 (Cobb et al. 1995). The resulting CE value is in units of mol/m3. This value is converted to 

units of gikg using equation 7. The density of the earthworm (pE) is assumed to be 1000 kg/m3 

(equivalent to density of water). 

density of earthworm 

Bulk density of soil 

Equation 7. C; = C, *m 

PE 

kg/m3 

g/cm3 

References 

Cobb, G.P., E.H. Hol, P.W. Allen, J.A Gagne, R.J. Kendall. 1995. Uptake, metabolism, and toxicity of terbufos in 

the earthworm (Lumbricus terrestris) exposed to COUNTER-15G in artificial soils. Environ. Toxicol. Chem. 

14(2):279-285. 

Mackay, D. and S. Paterson. I98 1. Calculating fugacity. Environ. Sci. Technol. 15: 1006- 10 14. 

USEPA. 2008. User's Guide: T-REX Version 1.4.1 (Terrestrial Residue Exposure model). United States 

Environmental Protection Agency. Environmental Fate and Effects Division. 

Page 70 of 70