MEMORANDUM

To:	Margaret Sheppard; U.S. EPA

CC:	Bella Maranion, Monica Shimamura; U.S. EPA

From:	Neha Mukhi, Kara Altshuler,  Reva Rubenstein, Mark Wagner; ICF
International

Date:	March 3, 2009

Re:	Recommendation for an Acceptable Exposure Limit for HFC-365 mfc (EPA
Contract EP-W-06-008, TO 026, Task 6)



This memorandum recommends Acceptable Exposure Limit for HFC-365 mfc and
summarizes toxicity information used to develop it. 

Please contact Mark Wagner (202)-862-1155 with questions or comments.

Recommendation for an Acceptable Exposure Limit for HFC-365mfc

The purpose of this report is to recommend an Acceptable Exposure Limit
(AEL) for occupational exposure to HFC- 365mfc.  The limited toxicity
studies reviewed for this chemical were a 28-day inhalation toxicity
study in rats (Kenny 1998a) and a cardiac sensitization study in dogs
(Kenny 1998b).

Recommended AEL: 	1000 ppm (8-hr Time Weighted Average) 

with a ceiling of 46,800 ppm.

Basis for recommendation:

Endpoint: 		Decreased body weight gains

Study: 	28-Day Repeat Dose Inhalation Toxicity Study in Rats (Kenny et
al. 1998a)

Protocol:	Nose-only inhalation, 6 hrs/day, 5 days/week for 4 consecutive
weeks (5 /sex/group)

Concentrations:	0 (air control), 9,685, 24,747 or 50,486 ppm

NOAEL:		24,747 ppm

LOAEL:		50,486 ppm

NOAEL [adj]:  	24,747 ppm x 6 hr / 8 hr = 18,560 ppm

NOAEL [HEC]: 	18,560 ppm

Uncertainty/Modifying Factors:

3  -	animal to human extrapolation and limited database

3  -	use of a less than sub-chronic study 

Total = 10

Resultant AEL is calculated to be 1856 ppm.

The AEL is limited to 1000 ppm based on Good Housekeeping Practices and
practical limits set by OSHA and other standards-setting bodies.

Ceiling:

Endpoint:		Cardiac sensitization

Study:	HFC- 365mfc-An inhalation Study to Investigate the Cardiac
Sensitization Potential in the Beagle Dog (Kenny 1998b)

Protocol:		Standard epinephrine challenge, 8 animals

Concentrations:	0.98, 2.49, 4.68, 7.51, or 9.63% (980, 24,900, 46, 800,
75,100 or 96,300 ppm)

NOAEL:		4.68% (46,800 ppm)

LOAEL:		7.51% (75,100 ppm)

NOAEL [adj]:  	46,800 ppm

NOAEL [HEC]: 	46,800 ppm

Uncertainty/Modifying Factors: none

Rationale

In a 28-day nose only inhalation toxicity study, male and female
Sprague-Dawley rats (5 sex/group) were exposed to 0 (air control),
9,685, 24,747 or 50,486 ppm HFC- 365mfc vapors 6 hours/day, 5 days/week
for 4 consecutive weeks (Kenny et al. 1998a).  The only
treatment-related clinical signs of toxicity were coldness to touch and
piloerection reported in the high-concentration group.  Body weight
gains exhibited a statistically significant decrease in the
high-concentration males and females, when compared with the controls. 
Over the 28-day exposure period, body weight gains in the
high-concentration females and males were 63% and 66%, respectively, of
the body weight gain in the controls.  At terminal sacrifice, the mean
body weights in the high-concentration males and females were
approximately 7.5% and 9% (not statistically significant) below the mean
body weights in the control males and females, respectively.  Food
consumption was approximately 10% less in the high-concentration males
and females over the 28-day study period, when compared with mean food
consumption in the controls; however, statistical significance was not
achieved. Other effects observed included changes in hematology,
clinical chemistry and urinalysis parameters.  Packed cell volume (PCV)
and hemoglobin (Hb) exhibited a statistically significant increase in
the low-, mid-, and high-concentration males, when compared with the
controls.  The percentage of reticulocytes (48%), total white blood cell
count (43%) and the percentage of lymphocytes (45%), eosinophils (71%),
basophils (66%), and large unstained cells (43%) were significantly
decreased in the high-concentration females, when compared with the
controls.  The percentage of eosinophils was also significantly
decreased in the low- (46%) and mid- (42%) concentration females.  

In the high-concentration males, urea nitrogen and glutamic-pyruvic
transaminase (GPT) exhibited a statistically significant increase by 20%
and 30%, respectively, when compared with the controls.  Sodium was
significantly increased (1-3%) in low-, mid- and high-concentration
males.  In the high-concentration females, GPT was significantly
increased (40%), while total protein and albumin were significantly
decreased (5-6%), when compared with controls.  Urine pH was
significantly decreased (6-7%) in the mid- and high-concentration males.
 In the high-concentration females, urine volume was significantly
increased (57%) and urine protein was significantly decreased (27%). 
The total urinary fluoride output was significantly increased in the
high-concentration males (43%) and in the mid- and high-concentration
females (85% and 44%, respectively); however, the concentration of
fluoride in the urine was not significantly different in the treated
groups, when compared with the controls.

At necropsy, the relative kidney weights were significantly increased in
the low-, mid-, and high-concentration males, by 17%, 5%, and 7%,
respectively.  Statistical analyses were not conducted on the incidence
data from the microscopic examinations.  However, the only microscopic
lesion that appeared to be related to treatment was the incidence of
ameloblastic dysplasia, in the high-concentration males and females. 
Ameloblastic dysplasia was reported in 100% and 60% of the
high-concentration males and females, respectively, compared to 40% in
the control males and 20% in the control females.  The severity of this
lesion was also greater in the high-concentration groups than in the
controls.

Decreased body weight gains, alterations in hematological, clinical
chemistry and urinalysis parameters and microscopic dental lesions were
observed in rats exposed to HFC- 365mfc.  The increases in PCV and Hb
were observed only in male rats and the magnitude of these changes was
small (<10%).  The magnitude of the decreased total protein and albumin
was small (<10%) and was observed only in females, and the increases in
BUN and SGPT were not associated with microscopic changes of the kidney
or liver.  Therefore, these changes were likely biological variation and
were not considered toxicologically significant.  The changes in
urinalysis parameters included increased volume and decreased protein in
the high-concentration females.  Although relative kidney weights were
increased, in the absence of microscopic changes in the kidney the
increased kidney weights were not considered toxicologically
significant.		

Despite the slight decreases in food consumption, the decreases in body
weight gain were considered related to treatment.  Although the
decreases in the total WBC count and differential WBC count was observed
only in females, the magnitude of these changes was large (from 40-70%).
 Therefore, the changes in WBC counts observed in the high-concentration
females were considered related to treatment.  The total output of
fluoride in the urine was increased in the high-concentration males and
females and in the mid-concentration males, although the concentration
of fluoride in the urine was not increased.  The increases in urine
fluoride likely reflected an increase in the excretion of fluoride from
the metabolism of the test compound.  Increases in urine fluoride are
not indicative of toxicity; however, excessive fluoride has been
associated with skeletal and dental toxicity.  Therefore, the dental
lesions observed in this study were considered related to treatment. 
Because the decreases in body weight gain were observed in both sexes,
this was considered the critical effect. Thus, the NOAEL for this study
was 24,747 ppm.

Dosimetric Adjustments

The human equivalent concentration (HEC) was calculated using the
default value of 1 for the ratio of the rat and human blood:air
partition coefficient.  The exposure duration of 6 hours/day was
adjusted for the normal 8-hour occupational exposure.  Because the
exposure of interest (occupational) is 5 days/week, no additional
adjustments were made for days/week.

Uncertainty Factors

As the RfC dosimetry guidelines were used, an uncertainty factor of 3,
rather than 10, was used for animal to human extrapolation.  An
additional uncertainty factor of 3 was applied for the use of a less
than sub-chronic study.  

Acceptable Exposure Limit (8-hr Time-Weighted Average)

Based solely on toxicological concerns, the AEL for HFC-365mfc would be
1856 ppm.  However, under industrial good housekeeping practices, it is
considered inappropriate to allow regular workplace exposure to an
inhaled chemical of greater than 1000 ppm on an 8-hour time-weighted
average.  For this chemical, following good housekeeping practices in an
occupational environment results in an AEL of 1000 ppm, lower than if
the AEL were based only on toxicological concerns.  

Ceiling

The results of the cardiac sensitization test (Kenny 1998) indicated
that exposures to HFC- 365mfc at levels below 46,800 ppm had no apparent
effects on the heart.  Thus the recommended ceiling for HFC- 365mfc is
46,800 ppm.

References

EPA.  1994.  Methods for Derivation of Inhalation Reference
Concentrations and Application of Inhalation Dosimetry. 
EPA/600/8-90/066F.  Office of Research and Development, Washington, DC. 
October 1994.

Kenny, TJ.  1998.  An inhalation study to investigate the cardiac
sensitisation potential in the beagle dog.  Huntingdon Study Number PDR
688/982163.  Huntingdon Life Sciences.  Huntingdon, Cambridgeshire,
England.  July 1998.

 HEC: Human Equivalent Concentration

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