Information to 

US EPA Environmental Fate 

and Effects Division

November 30, 2010
Physical & chemical characteristics

The water solubility of technical grade 

chlorphacinone is 13 mg/L, much lower than the 

34 mg/L reported in the CED. The correct data, 

reflecting the low solubility reflecting the low solubility, is import is important for 

other issues addressed below.
Food Intake (FI) Values

The Sonoran tiger salamander, Piping plover, 

Black-capped vireo, and Golden-cheeked 

warbler have FI values that are 103%, 110%, 

188% and 181% of their body weight per day,

using generic con using generic conversion factors. 

This significantly over-estimates the Dose-based 

EEC values used in the risk calculations. The use 

of such “extreme” data is not appropriate when 

better estimates can be easily made.
Residues in prairie dog carcasses

The CED uses the maximum residue of 2.24 

mg/kg in calculations. The large number of 

samples analyzed (16) allows the mean residue 

number to be used in risk calculations. The 

average of residues found in the combined 

whole body and liver (1 carcass was missing the 

liver) is 1.13 mg/kg. 
Nontarget primary consumer residue 

The CED uses residue data taken from an 

"anonymous" laboratory study on "mouse," with 

an unknown sample size, from a citation in 

another s another study rather than ather than an original s an original study. This 

data does not meet EPA’s acceptability criteria. 

The highest residue level from a reliable study is 

3.2 mg/kg-bw in voles - still very conservative 

and much larger than the reported field-derived 

residues (0.264 – 1.58, median of 0.922 mg/kg).
Toxicity value selection

The “5-day repeated dose” LD50 value is an 

“extreme” number with significant uncertainty, 

derived from a single study never been validated 

or repeated. The ecot ed. The ecotox data summary summary 

(Appendix E) shows four LC50 dietary feeding 

studies with Rattus norvegicus, showing LC50 

from 1.14 mg/Kg to 1.26 mg/Kg feed. This 

dietary route of exposure would be more 

appropriate than the five-day oral gavage study.
“ ... exposure over a five day period is highly 

probable” justifies using this 5 day tox value. 

This statement is not supported by evidence, 

and fails to recognize the dynamics of bait 

consumption that occurs following application 

of Rozol Prairie Dog Bait. airie Dog Bait. Almost all of the all of the 

available bait is consumed by the prairie dogs 

within a few days, as clearly illustrated by the 

data collected in the efficacy study performed 

by Lee and Hygnstrom (MRID 47333602)
Weight adjustment factors

- Chlorophacinone (CPN) has not been studied for 

scaling , nor any structurally-related compound;

- Chlorophacinone interrupts a biochemical cascade of 

coagulation with extended time for mortality to occur;

- CPN is not similar t CPN is not similar to chemicals o chemicals studied for scaling r scaling 

factors (highly water soluble, refractory to metabolism;

- Scaling factors derived from single dose acute toxicity 

test are appropriately for repeat-dose toxicity values;

- Scaling factor is incorrectly calculated in the CED, by 

using 20 grams as the weight of a rat;
• Scaling factor calculations in the CED do not conform 

to calculations in scientific literature;

• Scaling factor calculations in the CED are not 

explained or justified, no citation of any scientific 

evidence to support their use as applied to CPN;

• Therefore, the weight-adjusted toxicity values 

calculated in the CED analysis by application of 

scaling factors cannot be considered to be 

valid unless and until detailed explanation and 

justification is made.
Sublethal effects on Birds

• Secondary hazard studies on birds show no 

mortality to any of the tested birds, and 

“sublethal effects” showed only with test bait 

containing 50% ining 50% - 100% mor 100% more activ e active ingredient;

• No science supports the CED statements that 

“sublethal affects” are “equivalent to 

lethality.”
Sublethal effects on Mammals

• Studies on mammals support the conclusion of some 

risk of secondary poisoning;

• Almost all of the studies shown involve very small 

numbers of test subjects, with only one has a large 

enough sample t enough sample to be statistically tically significan significant;

• Many represent extreme "worst case" scenarios:

– contaminated prey fed much more bait than would be 

available in real-world situations;

– predator/scavenger test subjects fed more contaminated 

prey than likely;

– test subjects fed for more than five days – more than 10 

times longer in several of the reported studies.
Exposure data availability

• Liphatech submits annual reports to EPA that 

specify the amount of Rozol Prairie Dog Bait 

that is manufactured and sold during the 

previous calendar year;

• This provides important information about the 

prevalence of use, unlike “anecdotal evidence 

and the breadth of the registrant's advertising 

campaign” cited in the CED.
Chlorophacinone incidents 

• The majority of the incidents reported in Appendix 1 

of the CED have no applicability to the prairie dog 

control use pattern;

• Only one of five incidents “highly probable” for 

certainty are applicable e applicable to the prairie dog use airie dog use pattern;

• No listing of the alleged incidents reported by US FWS;

• no information on the method, conduct or results of 

reviews of these ecological incident data, which “... are 

considered to further refine the characterization of 

potential ecological effects of with exposure to

chlorophacinone”
Species-specific information

A significant number of the threatened or 

endangered species listed as LAA (Likely to 

Adversely Affect) could clearly have been 

excluded based on the background biological 

data presented in the CED itself.
Discussion of “risk” & “uncertainty”

• This “Chlorophacinone Effects Determination” 

assessment fails to assess “risk”, as it does not 

take into account any potential variation in 

exposure.

• The RQ values are only as certain as the least 

certain element, and these RQ calculations 

based on simplistic exposure estimates must 

be recognized as just that – simplistic 

estimates with extremely high uncertainty.
Revised calculations making only 3 changes – still very conservative, but:

- excludes data that clearly fails to meet EPA’s minimum standard for quality; 

- uses mean value of prairie dog carcass residues from a data set sufficiently large 

to be statistically analyzed, from a GLP data set of known source & quality;

- excludes weight-adjustment factors that have no scientific justification.

Parameter Original Value used in CED Revised Value

Exposure maximum value for 

direct bait consumption

100% of diet from bait Same as original

Exposure maximum value for 

secondary exposure to toxin

100% of diet from contaminated 

carcasses

Same as original 

Exposure Exposure maximum use maximum use Max. application rate and frequency Same as original

scenario

Max. application rate and frequency 

shortest interval between 

applications

Same as original

Food intake estimate Maximum FI calculated with 

generic equations

Same as original

Max nontarget carcass residue 5.8 mg/kg CHANGE: 3.2 mg/kg

Max prairie dog carcass 

residue

2.24 mg/kg CHANGE: 1.13 mg/kg

Toxicity value max - mammals 5-day repeat dose of 0.16 mg/kg Same as original

Toxicity value max - birds 5-day LC50 of 56 mg/kg Same as original

Weight adjustment to tox value Applied to each species CHANGE: Not applied
Species Original 

RQ Bait

Revised RQ 

Bait

Original RQ 

BTPD

Revised 

RQ BTPD

Original 

RQ Mouse

Revised

RQ Vole

California condor

* * 0.04 0.02 0.104 0.058

Whooping crane 0.89 0.89 0.04 0.02 0.104 0.058

Eskimo curlew * * ** 0.104 0.058

Northern Aplomado 

falcon * * 0.04 0.02 0.104 0.058

Chirichaua leopard frog 

* * ** 0.104 0.058

Mexican spotted owl 

Revised Table 5.1 Summary of RQ Values for Avian Species

Mexican spotted owl 

* * 0.04 0.02 0.104 0.058

Piping Plover 

* * ** 0.104 0.058

New Mexican ridgenosed rattlesnake 

* * ** 0.104 0.058

Sonora tiger salamander 

* * ** 0.104 0.058

Black-capped vireo 

* * ** 0.104 0.058

Golden-cheeked warbler

* * ** 0.104 0.058
Species 

Ingestion Rate 

(wet weight) 

(g/day)

Original 

RQ Bait

Revised 

RQ Bait

Original 

RQ BTPD

Revised 

RQ BTPD

Original 

RQ Mouse

Revised 

RQ vole

Grizzly Bear 3077.07

(dry wt for bait)

9615.85 

(carcass)

75.42 0.309

3.38 0.569 8.75 1.60

Black-footed 

ferret 147.84 * * 7.45 1.64 19.29 4.56

Jaguar 4118.89 * * 12.69 0.800 32.85 2.26

Revised Table 5.3 Summary of RQ values for Mammalian Species

Jaguar 4118.89 * * 12.69 0.800 32.85 2.26

Gulf Coast 

jaguarundi 739.36 * * 9.20 1.16 23.82 3.30

Canada lynx

819.48 * * 9.00 1.14 23.30 3.21

Preble’s 

meadow

jumping 

mouse

1.94 41.35 6.432 **   ** 

Ocelot 1575.97 * * 10.41 0.988 26.96 2.79

Gray wolf 2310.74 * * 9.49 0.906 24.82 2.57

*does not eat bait ** does not eat prairie dogs or non-target animals
Note again:

These revised RQ values still reflect 

the most protective and most 

conservative data that can be 

considered scientifically valid, 

including the “extreme” exposure and 

“extreme” toxicity data and its 

accompanying uncertainty.