Final—July 2, 2015

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Significant New Alternatives Policy Program 

Solvent Cleaning Sector

Risk Screen on Substitutes in Metals Cleaning, Electronics Cleaning, and Precision 

Cleaning

Substitute: Methoxytridecafluoroheptene Isomers

This risk screen does not contain Clean Air Act (CAA) Confidential Business Information (CBI) 

and, therefore, may be disclosed to the public.

1. INTRODUCTION

Ozone-depleting substances (ODS) are being phased out of production in response to a series of 

diplomatic and legislative efforts that have taken place over the past two decades, including the Montreal 

Protocol and the Clean Air Act Amendments of 1990 (CAAA). The U.S. Environmental Protection 

Agency (EPA), as authorized by Section 612 of the CAAA, administers the Significant New Alternatives 

Policy (SNAP) Program, which identifies acceptable and unacceptable substitutes for ODS in specific 

end-uses based on assessment of their health and environmental impacts. 

EPA’s decision on the acceptability of a substitute is based on the findings of a screening assessment of 

potential human health and environmental risks posed by the substitute in specific applications. EPA has 

already screened a large number of substitutes in many end-uses within all of the major ODS-using 

sectors, including refrigeration and air conditioning, solvent cleaning, foam blowing, aerosols, fire 

suppression, adhesives, coatings and inks, and sterilization. The results of these risk screens are presented 

in a series of Background Documents that are available in EPA's docket.

The purpose of this risk screen is to supplement EPA’s Background Document on the solvent cleaning

sector (EPA 1994) (hereinafter referred to as the Background Document). This risk screen evaluates the 

potential use of [ ]. Methoxytridecafluoroheptene isomers is a mixture of structural and stereo isomers, 

represented as [ ]. The exact structures of the remaining one percent of isomers are unknown. This 

substitute is hereinafter referred to as methoxytridecafluoroheptene isomers (MPHE) and is proposed as a 

substitute in metals cleaning, electronics cleaning, and precision cleaning end-uses in industrial 

applications. Table 1 presents information on the composition of the proposed substitute.

Table 1. Composition of MPHE

Constituent Chemical 

Formula

CAS 

Number a

Range of 

Concentration

(Weight Percent)

Typical

Concentration

(Weight Percent)

Potential Impurities

a CAS Registry Numbers for MPHE are not available.

The potential risks associated with the use of substitutes as solvents have been examined at length in the 

Background Document. The reader is referred to this reference for a detailed discussion of the 

methodologies used to conduct this risk screen. This risk screen addresses flammability risk and assesses 
Final—July 2, 2015

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the impact of potential releases of MPHE to the atmosphere. Additionally, occupational exposure and 

end-use exposure assessments were performed to ensure that manufacture and application of the proposed 

substitute in the proposed end-uses do not pose unacceptable risks to workers. Lastly, general population 

exposure was assessed to ensure that the proposed substitute does not pose an unacceptable risk to the 

population at large.

Section 2 of this report summarizes the results of the risk screen for the proposed substitute listed in Table 

1. The remainder of the report is organized into the following sections:

• Section 3: Atmospheric Assessment

• Section 4: Volatile Organic Compound Assessment

• Section 5: Potential Health Effects

• Section 6: Flammability Assessment

• Section 7: Occupational Exposure Assessment

• Section 8: End-Use Exposure Assessment

• Section 9: General Population Exposure Assessment

• Section 10: References

2. SUMMARY OF RESULTS

MPHE is recommended for SNAP approval as a solvent for metals, electronics, and precision cleaning. 

EPA's risk screen indicates that the use of the proposed substitute will be less harmful to the atmosphere 

than the continued use of ODS and other commonly used solvents, as it is less harmful to the ozone layer, 

has lower climate impact, and a shorter atmospheric lifetime. Given the expected composition of solvent 

formulations containing MPHE, minimal anticipated exposures to the proposed substitute are expected 

during end-use. 

MPHE is regulated as a volatile organic compound (VOC) under CAA regulations (40 CFR 51.100(s)). 

Based on analysis of potential MPHE emissions, VOCs from the use of MPHE in solvent cleaning are not

anticipated to result in greater impacts on local air quality in the United States than other available 

options. Releases of the proposed substitute should be controlled using absorbent material, and vapor inair detection systems should be used to further minimize potential exposures, as MPHE is highly volatile.

Based on the characteristics of the proposed substitute and the proper precautions listed in the

manufacturer’s safety data sheet (SDS) for MPHE, the proposed substitute is not expected to pose a 

flammability risk during manufacture or end-use (see Section 6). Given that personnel will receive proper 

training, appropriate personal protective equipment (PPE) (e.g., respiratory protection, goggles, 

impervious gloves, chemical-resistant clothing and boots) will be available, and proper procedures 

according to the SDS will be used during manufacturing, end-use, and disposal, no significant toxicity 

risk to workers, end-users, or the general population is anticipated.

3. ATMOSPHERIC ASSESSMENT

This section presents an assessment of the potential risks to atmospheric integrity posed by the use of 

MPHE as a solvent. The ozone depletion potential (ODP), global warming potential (GWP), and 

atmospheric lifetime (ALT) of the proposed substitute are presented in Table 2.

The proposed substitute is substantially less harmful to the ozone layer, has less climate impact, and a 

shorter ALT when compared to CFC-113, methyl chloroform, HCFC-225ca, and HCFC-225cb. In 

addition, MPHE also has lower climate impact and a shorter ALT than those predicted for other 

substitutes examined in the Background Document, as well as commonly utilized substitutes, such as 

HFC-43-10mee and HFC-365mfc. Thus, EPA believes that use of MPHE would result in substantially 

less harm to the climate and ozone layer than the continued use of ODS and other commonly used ODS 

substitutes.
Final—July 2, 2015

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Table 2. Atmospheric Impacts of MPHE Compared to Other Cleaning Solvents

Solvent Ozone Depleting Potential

(ODP)a

Global Warming Potential 

(GWP)b

Atmospheric Lifetime in 

Years (ALT)b

MPHE

CFC-113 0.85 6,130 85

Methyl chloroform 0.16 146 5

HCFC-225ca 0.02 122 1.9

HCFC-225cb 0.03 595 5.8

HFC-43-10mee 0 1,640 15.9

HFC-365mfc 0 794 8.6 aWMO (2011)

b IPCC 4th Assessment Report (Forster et al. 2007)

4. VOLATILE ORGANIC COMPOUND ASSESSMENT

MPHE is regulated as a VOC under CAA regulations (40 CFR 51.100(s)). Through regulations and 

standard industry practices, emissions of MPHE should be controlled. 

The submitter intends to manufacture MPHE as a cleaning solvent for metal, electronics, and precision 

cleaning. IPCC estimates that 50 percent of initial solvent charge is emitted per year (IPCC/TEAP 2007); 

however, this emission factor encompasses all solvent cleaning processes including cold cleaning, which 

has very high emissions, and more controlled, less emissive equipment, such as vapor degreasing.

MPHE is intended to be used indoors within a controlled environment for the metals, electronics, and 

precision cleaning end-uses, in which spent solvent is captured and recovered or disposed as sludge 

throughout its use within a completely contained unit. Only a portion of the solvent, assumed to be on the 

order of 10 percent annually,

1 is expected to escape from the control technologies (freeboard and 

condensing coils) employed in a typical vapor degreaser, and subsequently be released to the atmosphere. 

Many larger end-use facilities may employ additional control technologies to reduce and remove solvent 

from workplace air before it is vented from the facility. 

An assessment was performed to compare the annual VOC emissions from the use of MPHE in the 

solvent cleaning end-uses to other anthropogenic sources of VOC emissions. Assuming the submitter’s 

maximum anticipated annual production of MPHE for all proposed end-uses is entirely released (in the 

absence of controls), approximately [ ] MT of VOCs would be emitted. This is approximately equal to [ ]

percent of all anthropogenic VOC emissions in the United States in 2014;

2 however, the release of total 

production for all proposed end-uses of MPHE is extremely unlikely to occur. Thus, an additional 

analysis was performed to determine more realistic annual VOC emissions from the use of MPHE in 

metal, electronics, and precision cleaning applications. 

An emissions estimate of 10 percent was assumed for use of MPHE in highly controlled equipment (i.e.,

vapor degreasers), which is the maximum annual amount of solvent released during end-use for facilities 

without additional engineering controls on their ventilation systems, such as carbon absorption units.

Assuming the average annual release rate for metals, electronics, and precision cleaning, and that use of 

MPHE is distributed according to existing market share for each proposed end-use provided by the 

submitter, approximately [ ] MT of VOCs is expected to be released into the atmosphere annually. This 

amount is approximately [ ] percent of all anthropogenic VOC emissions in the United States. As the 

 1 The IPCC estimates that 50 percent of initial solvent charge is emitted per year (IPCC/TEAP 2007), including all solvent 

cleaning procedures and equipment. Replacing old degreasing equipment with new equipment providing better containment of 

solvents can reduce emissions in this sector up to 80 percent, so vapor degreasing units have an approximated emission rate of 10 

percent (IPCC/TEAP 1999). 2 Based on the 2014 annual total VOC emissions for the United States. (i.e., approximately 17.1 x 106 MT) as reported in the 

National Emissions Inventory (EPA 2015).
Final—July 2, 2015

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calculated annual releases of MPHE from this analysis are several orders of magnitude lower than other 

anthropogenic sources of VOC emissions, EPA believes that through the use of regulations and standard 

industry practices, the environmental impact of MPHE from VOC emissions is not considered a 

significant concern.

Although these VOC emissions for highly controlled solvent cleaning applications are several orders of 

magnitude lower than other anthropogenic emissions, it is likely that the VOC emissions estimated here 

can be further reduced, and in some facilities may already be so reduced. For example, capture and 

destruction technologies for fugitive emissions are employed in larger facilities, and hence emissions

during use of MPHE may be even less than estimated here. Vapor degreasers would also likely utilize 

control measures to reduce solvent emissions such as high freeboard height (i.e., the distance from the 

solvent vapor-air interface to the top of the degreaser) or refrigerated freeboard chillers, which provides a 

chilled air blanket above the solvent vapor (EPA 2009). In addition, the majority of the solvent sector 

utilizing ODS substitutes (approximately 74%) is made up of solvents that are considered to be VOCs, 

such as trichloroethylene and organic solvents, and thus, use of MPHE is not expected to increase VOC 

emissions relative to these other acceptable substitutes (ICF 2012).

Because MPHE is intended for smaller, niche markets (e.g., metals, electronics cleaning, and precision 

cleaning) and is projected to have lower production levels in comparison to the entire solvent sector, use 

of MPHE would not result in greater impacts on local air quality than other available options.

5. POTENTIAL HEALTH EFFECTS

To assess potential health risks from exposure to this proposed substitute, EPA identified the relevant 

toxicity threshold values for comparison to modeled exposure concentrations for different scenarios. The 

submitter indicates MPHE has an acceptable exposure limit (AEL) of [ ] ppm. The AEL represents the 

maximum 8-hour time weighted average (TWA) at which a worker can be exposed regularly without 

adverse effects. An AEL of 625 ppm was independently developed for MPHE based on a review of 

available toxicity studies. EPA’s determination of a 625 ppm AEL and summary of available toxicity 

studies can be found in Appendix A. Because it is the more conservative value, the submitter’s AEL of [ ] 

ppm was used in exposure assessments in this risk screen.

According to the SDS, exposure to MPHE through ocular or dermal absorption, inhalation, or ingestion

may be harmful. If MPHE is inhaled, ingested, or absorbed through skin or eyes in large amounts, the 

affected person(s) should adhere to the first aid measures provided in the SDS. In the case of ocular 

exposure, the SDS for MPHE recommends that person(s) should immediately flush their eyes, including 

under their eyelids, with water for 15 minutes. Medical attention should be sought if irritation persists

(DuPont 2012). In the case of dermal exposure to MPHE, the SDS for MPHE recommends that person(s) 

should immediately remove all contaminated clothing to avoid irritation and wash the affected area with 

warm water. 

If high concentrations of MPHE are inhaled, the SDS recommends person(s) should be immediately 

removed from the contaminated space and exposed to fresh air. The SDS recommends that if breathing is 

difficult, artificial respiration and/or oxygen may be necessary, and medical attention should be sought. In

case of ingestion, the SDS recommends person(s) consult a physician immediately, and refrain from

inducing vomiting without medical advice, as there is a greater hazard associated with aspirating MPHE

into the lungs if vomiting is induced. 

EPA’s review of the human health impacts of this proposed substitute is contained in the public docket 

for this decision. These risks and procedures after exposure are similar for other common solvents. The 

potential health effects of MPHE can be minimized by following the exposure guidelines and ventilation 

and PPE recommendations outlined in the SDS for MPHE and this risk screen. 
Final—July 2, 2015

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6. FLAMMABILITY ASSESSMENT

MPHE is considered to be non-flammable (DuPont 2012). Based on this classification, manufacture, 

servicing, and use of MPHE is not expected to present a flammability risk in solvent cleaning

applications. 

7. OCCUPATIONAL EXPOSURE ASSESSMENT

[ ]. MPHE is proposed for use neat and in blends with an average composition of [ ] percent MPHE by 

weight. The blend formulations vary according to the cleaning application (DuPont 2012).

Using EPA’s Chemical Screening Tool for Exposures and Environmental Releases (ChemSTEER),

3 the 

submitter provided estimated exposures during [ ]. Neither the American Conference of Industrial 

Hygienists (ACGIH) nor the American Industrial Hygiene Association (AIHA) recommended short-term 

exposure limits (STELs) for MPHE. As a result, a STEL for MPHE was developed by EPA based on the 

submitter’s AEL of [ ] ppm. The STEL was estimated as three to five times the AEL, which is an 

established method of estimating a short-term exposure limit by ACGIH. The results of the submitter’s 

exposure assessment are presented in Table 3.

Table 3. Modeled Occupational Exposure during [ ]

Activity

Duration of Potential 

Exposure 

(hours/day)

Measured Exposure 

Concentration (ppm)

Exposure Limit

(ppm)

a EPA-derived STEL b 8-hour AEL

As shown in Table 3, exposures during [ ] activities are significantly less than the STEL. Furthermore, 

worker exposure during [ ] is expected to be significantly less than the 8-hour AEL. The combined daily 

exposure is also significantly less than the AEL. If one worker were to perform all activities listed in 

Table 3 in an 8-hour workday, exposure would be [ ] ppm per day (DuPont 2012). This estimate is lower 

than the AEL and does not pose a concern for occupational exposure during all activities over an 8-hour 

workday.

Because ChemSTEER does not consider engineering controls such as local exhaust ventilation, exposure 

levels are expected to be lower than the results presented in Table 3. MPHE is not expected to pose a risk 

to workers during [ ] when the engineering controls and PPE guidelines consistent with the Occupational 

Safety and Health Administration (OSHA) are followed.

In the case of large releases of MPHE, the proposed substitute should be collected on absorbent material 

(e.g., rags, saw dust, vermiculite, spill pillows, cellulose products) and transferred to steel drums for 

recovery or disposal to prevent leakage into sewers, waterways, or low lying areas, as recommended by 

the SDS. Once the proposed substitute is adequately removed and clean-up residues are disposed of in

accordance with the SDS, normal ventilation for standard manufacturing procedures and vapor in-air 

detection systems should be used to further minimize potential exposures. 

 3 EPA’s Chemical Screening Tool for Exposures and Environmental Releases (ChemSTEER) is a computer-based software 

program used to estimate workplace exposures and environmental releases for chemicals manufactured and used in 

industrial/commercial settings.
Final—July 2, 2015

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EPA believes that because proper handling and disposal guidelines are followed in accordance with good 

industrial hygiene and manufacturing practices, and the substitute’s SDS, there is no significant risk to 

workers during the manufacture of MPHE. See the following section, “End-Use Exposure Assessment” 

for a discussion of exposure to workers using MPHE during cleaning of equipment.

8. END-USE EXPOSURE ASSESSMENT

MPHE is proposed for use as a solvent for metals, electronic, and precision cleaning end-uses in industrial 

applications. MPHE is not intended for direct consumer use (DuPont 2012). 

Exposure to MPHE when used as a solvent in vapor degreasing units will be limited to during [ ]. The 

submitter estimated reasonable worst-case exposures to MPHE during end-use using ChemSTEER. The 

exposures were estimated for a [ ] L vapor degreaser, which is approximately the maximum size for 

manually operated vapor degreasers. In addition, MPHE is proposed for use in a blend with an average 

concentration of [ ] percent MPHE. As such, the exposure modeling is based on a [ ] percent MPHE

formulation. The estimated exposure concentrations during [ ] are presented in Table 4.

Table 4. Modeled End-Use Exposure for MPHE in Solvent Cleaning (ppm)

Activity Duration of Potential

Exposure (hours/day)

Measured Exposure 

Concentration (ppm)

Exposure Limit

(ppm)

a EPA derived STEL b 8-hour AEL

The average anticipated exposure concentrations for MPHE during [ ] are significantly below the STEL.

Furthermore, significant exposure to the proposed substitute is especially not expected during [ ], as the 

fluid is contaminated and contains approximately [ ] percent less MPHE. 

The combined daily exposure (i.e., if a worker were to perform all the activities in an 8-hour workday)

would be approximately [ ] ppm per day (DuPont 2012). This estimate is also lower than the AEL, and 

does not pose a concern for exposure during all end-use activities listed in Table 4 over an 8-hour 

workday.

Given that MPHE in metal, electronic, and precision cleaning end-uses is not expected to result in 

significant exposure, and because end-users of MPHE will follow appropriate cleaning equipment 

guidelines and environmental measures, such as employment of capture and destruction technologies, 

EPA does not believe that MPHE presents a significant risk to workers at end-use. 

9. GENERAL POPULATION EXPOSURE ASSESSMENT

This section screens potential risks to the general population from exposure to releases of MPHE to 

ambient air, surface water, and solid waste. Because the proper safety and disposal precautions, as listed 

in the remainder of this section, are followed, MPHE is not expected to cause a significant risk to the 

environment and human health in the general population when manufactured or used for metals, 

electronics, and precision cleaning end-uses. 

9.1 Ambient Air

MPHE is highly volatile [ ]. Accidental release measures, handling and storage, engineering controls, and 

waste disposal must be followed per the proposed substitute’s SDS to avoid significant releases to air. 

Given that metal, electronics, and precision cleaning end-uses will take place indoors with good 
Final—July 2, 2015

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manufacturing practices, such as employment of capture and destruction technologies, releases are not 

expected to result in significant exposure to the general population.

9.2 Surface Water

Due to the near-insolubility of MPHE in water [ ], MPHE is not likely to accumulate in surface water 

(DuPont 2012). For the proposed solvent cleaning end-uses, the product will be handled indoors with 

waste or accidental spills collected in steel drums or taken up with an absorbent material. Water 

contaminated with MPHE should not be dumped into sewers, on the ground, or into any body of water, in 

accordance with the SDS.

9.3 Solid Waste

Although the constituents of MPHE are not listed as Resource Conservation and Recovery Act (RCRA)

hazardous wastes, solvents used for metal, electronics, and precision cleaning applications generally 

collect metals and other chemical compounds during the cleaning process, which may cause the spent 

solvent to display characteristics of hazardous waste (e.g., ignitability, corrosivity, reactivity, toxicity). 

Any solid waste displaying these characteristics or having a specific waste code (e.g., F001) is considered 

to be a hazardous waste (40 CFR Part 261). Waste regulated as RCRA hazardous waste is subject to the 

requirements of the Subtitle C program (including storage, treatment, and disposal requirements), which 

EPA believes are sufficient to control human health and environmental risks. In addition, because solid 

materials used during end-use or clean-up procedures that may be absorbed with MPHE (e.g., rags, 

vermiculite, and spill pillows) are disposed of in accordance with the MPHE SDS, EPA does not expect 

general population exposure to MPHE through solid waste to occur. 
Final—July 2, 2015

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10. REFERENCES

Campbell, N., J. Hu, P. Lapin, A. McCulloch, A. Merchant, K. Mizuno, J. Owens, P. Rollet. 2007. 

IPCC/TEAP Special Report: Safeguarding the Ozone Layer and the Global Climate System, Chapter 10: 

Non-Medical Aerosols, Solvents, and HFC-23.

DuPont Chemicals & Fluoroproducts (now The Chemours Company). 2012. Premanufacture Notice and 

Significant New Alternatives Policy Program Submission to the Environmental Protection Agency for 

Methoxytridecafluoroheptene Isomers to the United States Environmental Protection Agency. June 22, 

2012. 

EPA 2015. National Emissions Inventory Air Pollutant Emissions Trends Data. Accessed 13 March 2015. 

Updated March 2015. Available at: http://www.epa.gov/ttnchie1/trends/.

EPA 2009. Compilation of Air Pollutant Emission Factors, Volume I: Chapter 4: Evaporation Loss 

Sources, Section 4.6: Solvent Degreasing. AP 42, Fifth Edition. Available at: 

http://www.epa.gov/ttnchie1/ap42/ch04/final/c4s06.pdf.

EPA 1994. Significant New Alternatives Policy Technical Background Document: Risk Screen on the 

Use of Substitutes for Class I Ozone-depleting Substances: Solvent Cleaning. Stratospheric Protection 

Division. March, 1994.

Forster, P., V. Ramaswamy, P. Artaxo, T. Berntsen, R. Betts, D.W. Fahey, J. Haywood, J. Lean, D.C. 

Lowe, G. Myhre, J. Nganga, R. Prinn, G. Raga, M. Schulz and R. Van Dorland. 2007. Changes in 

Atmospheric Constituents and in Radiative Forcing. In: Climate Change 2007: The Physical Science 

Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel 

on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and 

H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

ICF International. 2012. Solvent Sector VOC Analysis for ODS Substitutes. Prepared for EPA’s 

Stratospheric Ozone Protection Division. February 12, 2012.

IPCC. 1999. Meeting Report of the Joint IPCC/TEAP Expert Meeting on Options for the Limitation of 

Emissions of HFCs and PFCs. Intergovernmental Panel on climate Change Technology and Economic 

Assessment Panel. 26-28 May 1999.

WMO (World Meteorological Organization), 2011. Scientific Assessment of Ozone Depletion: 2010, 

Global Ozone Research and Monitoring Project—Report No. 52, 516 pp., Geneva, Switzerland.
Final—July 2, 2015

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Appendix A

Determination of an Acceptable Exposure Limit (AEL) for MPHE

Recommended AEL: 625 ppm (8-hour time-weighted average)

Basis and Endpoints: NOAEC4: 2,500 ppm (dehydration; clinical chemistry; microscopic 

changes in the teeth)

Critical Study: 28-day inhalation (whole body) study (DeLorme 2014)

Doses: 0; 1,000; 2,500; 5,100 ppm

NOAEC: 2,500 ppm 

HEC5: 2,500 ppm x 6 hr/d / 8 hr/d = 1,875 ppm 

Uncertainty Factors: 3 – animal to human extrapolation

 

 4 No Observable Adverse Effect Concentration (NOAEC)

5 Human Equivalent Concentration (HEC)
Final—July 2, 2015

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I. Introduction

MPHE [ ] has been proposed as a replacement for CFC-113, HCFC-225ca/cb, and methyl chloroform in 

many solvent cleaning uses, as well as in carrier fluid and heat transfer fluid applications. Several studies 

assessing the potential toxicity of MPHE have been conducted, including the following: 

• An acute inhalation study in rats; 

• a sub-acute (28 day) inhalation study in rats;

• four genotoxicity studies in bacterial and mammalian cells; and 

• four gavage (oral) studies in rats. 

The results of these studies are discussed in the following sections to inform an assessment of the

potential health risks from human exposure to the study compound in the intended end-uses.

II. Summary of Toxicity Studies

The toxicological studies reviewed for the determination of an AEL for MPHE are summarized below in 

Table 1. The toxicity database is rather comprehensive, but is focused primarily on gavage (oral) 

exposure studies, which are of limited usefulness for the determination of an occupational AEL based on 

the expected inhalation exposures (as discussed in the latter portion of Section IV). 
Final—July 2, 2015

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Table 1. Select MPHE Toxicological Studies

a All values NOAEL/NOAEC unless otherwise reported; NOAEL/NOAEC = No observed adverse effect level/concentration 

(commonly used for oral or dermal/inhalation exposures); wt – weight

Principal Studies Concentrations NOAEC(L)a Effects

Acute (inhalation; whole 

body; rat)

0; 2,000; 5,000; 

9,700; 15,000 ppm

LC50>15,000 

ppm

Anesthetic effects at ≥5,000 ppm including 

↓ activity 10 min. into exposure; rats were 

motionless at 45 min. into exposure. 

28-day (inhalation; whole 

body; rat) with 14-day 

recovery

0; 1,000; 2,500; 

5,100 ppm 2,500 ppm

Diuresis-induced dehydration; changes in 

clinical chemistry parameters; 

degeneration of tooth epithelium in 1 male 

at 5,100. Adaptive liver effects

acute (oral; female rat) 0; 5,000 mg/kg LC50>5,000 

mg/kg No clinical findings or gross pathology.

28-day (oral; rat) 0; 250; 500, 1,000 

mg/kg 1,000 mg/kg

Sig. ↑ absolute, relative liver wt in males 

and females; sig. ↑ absolute, relative 

kidney wt in males. Hepatocellular 

hypertrophy in 2/10 males at 1,000 mg/kg; 

considered adaptive effect. No 

histopathology in kidneys in males. Some 

clinical chemistry changes at ≥500 mg/kg.

28-day with FOB (oral; 

rat) 

0; 100; 250; 1,000 

mg/kg 1,000 mg/kg

Sig. ↑ absolute, relative liver wt in males. 

Hepatocellular hypertrophy in both sexes at 

250 and 1,000 mg/kg; considered adaptive 

effect.

90-day (oral; rat) with 30-

day recovery

0; 250; 500, 1,000 

mg/kg

Not identified 

(males); 1,000 

mg/kg 

(females)

Evidence of chronic progressive 

nephropathy in males at all doses, 

including 7/10 control animals; no similar 

effects in females. Sig. ↑ absolute, 

relative liver weights in both sexes at all 

doses.

Developmental toxicity 

(oral; rat) 

0; 250; 500; 1,000 

mg/kg 1,000 mg/kg No exposure-related adverse effects.

Supporting Studies Doses NOAEL Effects

In vitro bacterial reverse 

mutation assay ≤5,000 μg/plate 5,000 μg/plate Negative

In vitro chromosomal 

aberration assay, CHL 

cells

≤3621 μg/mL 3621 μg/mL Negative

In vivo micronucleus 0, 500; 1,000; 2,000 

mg/kg 2,000 mg/kg Negative

In vivo micronucleus 0, 1,000; 2,500; 

5,100 ppm 5,100 ppm Negative
Final—July 2, 2015

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III. Development of the AEL for MPHE

The body of data indicates that MPHE induces anesthetic effects in rodents at concentrations ≥ 5,000 ppm 

in inhalation exposures lasting 4 hours; however, no neurotoxic effects were noted in the 28-day 

inhalation study. Toxicity from repeated inhalation exposure is limited to diuresis-induced dehydration, 

increased serum levels of albumin, globulin and total proteins, and decreased body weight, in male rats 

only at 5,100 ppm. Further, one male rat at 5,100 ppm exhibited degeneration/atrophy of the ameloblastic 

epithelium (the enamel-producing cells of the teeth). Hepatocellular hypertrophy was noted in both sexes 

at 5,100 ppm and in males at 1,000 and 2,500 ppm, but this effect is due to an adaptive increase in 

metabolic enzymes and commonly occurs in response to many xenobiotics. Thus, it was not considered 

adverse. Oral toxicity appears to be limited to adaptive effects in the livers and kidneys of primarily male 

rats. No effects in the kidneys other than increased absolute and relative weight were present in the 28-

day gavage study, whereas, kidney lesions (i.e., chronic progressive nephropathy [CPN]) were present in 

the 90-day study. 

Because of the high incidence of CPN in control male rats in the 90-day gavage study, however, the effect 

cannot be ascribed specifically to oral exposure to the study compound. The problematic kidney data 

limits the usefulness of the oral studies for establishing an occupational exposure limit. Another limitation 

of the studies is that the gavage (oral) pathway used to expose the rodents to MPHE is not relevant for 

worker exposure. Although the submitter argues that inhalation toxicity is unlikely to be a significant 

pathway of exposure (DuPont 2013), the vapor pressure for the compound ([ ] mm Hg) and boiling point 

([ ]oC) are comparable to those of perchloroethylene (18.6 mm Hg; 121.1oC), and the compound is 

generally classifiable as volatile or likely to be volatile (Mackay et al. 1993). It is reasonable to expect 

that MPHE will enter the vapor phase during vapor degreasing and if it is used as an aerosol solvent. 

Further, exposure to high concentrations identified in the acute inhalation exposure study resulted in 

clinical signs indicative of anesthetic effects. This contrast between the acute inhalation study and the oral 

studies indicates that there are differences in activity in the compound between exposure routes, and thus 

the oral studies will not serve as a basis for development of an exposure limit that is protective of 

occupational health. For this reason, the 28-day inhalation exposure study has been chosen as the 

appropriate toxicity study. 

ICF calculated the AEL using the following equations:

2,500 ppm x (6 hr/8 hr) = 1,875 ppm

1,875 ppm x 1/3 = 625 ppm

A HEC was determined by adjusting the identified NOAEC of 2,500 ppm in the 28-day inhalation study 

by the ratio of rat exposure duration per day to that of an occupational worker (6 hours/8 hours). No 

further exposure duration adjustment was necessary. A total uncertainty factor (UF) of 3 was applied to 

account for pharmacodynamic differences between rats and humans as the guidelines for developing 

Reference Concentration (RfC) values (U.S. EPA, 1994) were followed. 
Final—July 2, 2015

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IV. Principal Toxicity Studies

Inhalation Exposure

Acute Study

In the acute study (Kegelman 2011), five young adult Sprague-Dawley rats per sex were exposed via 

inhalation (whole-body exposure) to MPHE in measured concentrations of 0; 2,000; 5,000; 9,700; or 

15,000 ppm for 4 hours. During the exposure, the rats were reportedly assessed for response to stimuli 

(startle response) three times. Rats were sacrificed 14 days following exposure and assessed for gross 

pathological effects; rats in control and 15,000 ppm groups were assessed for histopathology in the 

respiratory tract, livers, and kidneys. 

According to the study summary and discussion sections, 5/5 rats of both sexes at 9,700 ppm exhibited 

decreased activity within 10 minutes of the start of exposure, and within 30 minutes of exposure, the rats 

became motionless and remained motionless throughout the rest of the exposure period. The only 

exception is that the rats did exhibit a normal startle response when challenged. All male and female rats 

at 15,000 ppm exhibited increased activity level from 10 minutes until 45 minutes of exposure, which 

included the following: rapid head-bobbing and ear twitching, chewing motions, excessive grooming, and 

an increased startle response. All rats were motionless within 20 minutes of the start of exposure. The 

anesthetic symptoms were gone 5 minutes (9,700 ppm) or 6 minutes (15,000 ppm) post-exposure, 

indicating that the study compound was exhaled quickly and did not persist in the bloodstream to cause 

any adverse clinical signs (DuPont 2013a). No abnormal clinical signs were reported during the 14-day 

recovery period in any exposure group. 

Four of five male rats at 9,700 ppm, 5/5 male rats at 15,000 ppm, and 2/5 female rats at all levels 

exhibited weight loss after the first day of exposure (≤ 10 grams), but normal weight gain was reported 

during the recovery period. As food consumption was not measured, it is not possible to determine if this 

minimal weight loss was a result of the animals avoiding their food.

None of the rats exhibited adverse signs upon gross necropsy and no exposure-induced signs of toxicity 

were noted in the 15,000 ppm-group animals as compared to controls. It is notable that 2/5 control males 

exhibited minimal CPN, as did 1/5 males at 15,000 ppm. The incidence of CPN in the other groups, if 

any, is not reported because tissues from those animals were not evaluated microscopically.

Subacute (28-day) Study

In a 28-day whole body inhalation study (DeLorme 2014), male and female CD® rats (20/sex) were 

exposed to: 0; 1,000; 2,500; and 5,100 ppm of the study compound for 6 hours per day, 5 days per week,

for 4 weeks (21 exposures). Blood samples were taken from 5 rats/sex/exposure group following the 

fourth exposure and again at the end of the exposure period for analysis of micronuclei induction 

(discussed in the Genotoxicity section). Following the exposure period, 10 male and 10 female rats in 

each group were allowed a 14-day recovery period to assess the reversibility of any observed adverse

effects. Blood and urine samples were taken from the remaining 10 rats/sex in each exposure group for 

hematology, clinical chemistry and urinalysis assessment; the rats were then sacrificed for gross necropsy 

and organ analysis.
Final—July 2, 2015

14

The study followed harmonized guidelines and appropriate endpoints were measured. Exposure to 

MPHE did not result in early mortality, moribundity or adverse clinical signs.6 Further, no adverse 

findings were noted in the measured ophthalmological or neurobehavioral endpoints, including forelimb 

and hindlimb grip strength, motor activity assessment, and functional observational battery 

measurements. No changes were noted in any exposed groups in body weight gain, food consumption, or 

hematology. High-concentration males did exhibit a slight (11.3%) but significant reduction in body 

weight following the final exposure compared to controls. Plasma fluoride was increased significantly in 

mid- and high-concentration males and females and urinary fluoride was increased significantly in all 

exposed rats. Plasma fluoride levels returned to near control levels following the 14-day recovery period; 

urinary fluoride levels had decreased, but not completely returned to pre-exposure levels following 

recovery. Male rats at 5,100 ppm exhibited diuresis (increased urine volume and decreased urine specific 

gravity), as well as increased serum albumin, globulin, and total protein levels, and decreased body 

weight. The study authors considered the increased serum protein load and the decreased body weight to 

be secondary to the dehydration resulting from fluoride-induced increased urine output; ICF agrees with 

this assessment. Diuretic effects were also noted in low- and mid-concentration males and in mid- and 

high-concentration females; slight increases in serum proteins in males at 1,000 and 2,500 ppm were also 

seen, but the changes were minimal and were not coincident with body weight decrements. Thus, 

although exposure related, the changes were not deemed adverse. Further, the observed changes in 

urinalysis and clinical chemistry parameters were reversible following the recovery period.

Adaptive changes related to compound exposure were noted in the liver, as well as in the larynx:

• mild hepatocellular hypertrophy in all high-concentration rats,

• minimal hypertrophy in 

o 3/10 males at 1,000 ppm

o 10/10 males at 2,500 ppm, and 

o 10/10 females at 5,100 ppm; 

• minimal hyperplasia/squamous metaplasia of the larynx in 

o 8/10, 6/10, and 10/10 exposed males in low-, mid-, and high-concentration groups at 

necropsy, 

o 5/10, 8/10, and 10/10 exposed females in low-, mid-, and high-concentration groups at 

necropsy,

o 3/10 low- and 4/10 high-concentration males at recovery, and

o one high-concentration female at recovery; 

• minimal goblet cell7 hyperplasia in the anterior section of the nose at terminal and recovery 

necropsy in 

o 8/10, 8/10, and 8/10 low-, mid-, and high-concentration males, and

o 5/10, 8/10, and 7/10 low-, mid-, and high-concentration females. 

Liver weights were slightly but significantly increased in all exposed male groups and in highconcentration females, resulting from the hypertrophy. These increases were partially resolved after the 

14-day recovery period: males at 2,500 and 5,100 ppm and females at 5,100 ppm still exhibited increased 

liver weights compared to controls, but the values had decreased over the preceding 14 days. 

Interestingly, 2,500-ppm recovery females had significantly (8%) increased liver weights compared to 

controls, but this value was unlikely to be biologically relevant as it was not present at the end of 

exposure. No other organ weights were affected by exposure.

 6 One 1,000-ppm male was sacrificed on day 27 due to poor health; based on necropsy findings, the animal's condition was 

attributed to urogenital tract inflammation that was not related to exposure.

7 Goblet cells are epithelial cells that produce mucins (components of mucus).
Final—July 2, 2015

15

A single male at 5,100 ppm exhibited degeneration/atrophy of ameloblastic epithelium8 at recovery, 

believed to be due to fluoride exposure in the study compound. Very slight lamination of dentin was 

noted in one male at 2,500 ppm and in 2/10 males at 5,100 ppm at recovery, and incomplete 

decalcification of enamel/dentin in 4/10 males at 2,500 ppm and 5/10 males at 5,100 ppm. No exposed 

females exhibited these endpoints. The incomplete decalcification is indicative of exposure only and is an 

artifact of tissue processing. The slight lamination of dentin was not considered adverse and occurred in 

only one male at 2,500 ppm. The NOAEC was identified as 2,500 ppm by the study author, based on 

diuresis-related effects (increased serum proteins, dehydration and weight loss) and microscopic effects in 

the enamel-producing cells of the teeth in 1 male at 5,100 ppm.

Oral Exposure

The remaining rodent toxicity studies all utilized the gavage (oral) exposure pathway because, according 

to the submitter, significant repeated inhalation exposures were unlikely and it would be difficult to 

achieve airborne concentrations of MPHE given its relatively low vapor pressure (DuPont 2013b). Four 

gavage studies were conducted: a limit dose (acute) study, two subacute (28-day) repeat exposure studies, 

one subchronic study, and a developmental study.

Acute exposure

An oral limit-dose assay in young adult Sprague-Dawley rats (5 females) was performed to determine the 

limits of acute toxicity (Durando 2009). In this study, only female rats were used because the study 

authors claimed that females are "frequently more sensitive to the toxicity of test compounds than males." 

One female was initially given a single bolus dose of MPHE (neat) via gavage at 5,000 mg/kg. When this 

rat did not die prematurely, 4 additional females were dosed in the same manner. The animals were 

watched cage-side for mortality and clinical signs of toxicity within the first 30 minutes and during the 

first several hours after dosing. No behavioral challenges were performed as in the inhalation study, 

although it was noted that "particular attention was directed to observation of tremors, convulsions, 

salivation, diarrhea, and coma." Gross necropsies were performed after 14 days of recovery, but no 

histopathology was done to determine that tissues were not affected. No adverse effects were reported 

and the rats satisfactorily gained weight (body weights were only measured at days 7 and 14, so subtle 

changes in body weight over 1-2 days would not have been evaluated in this study). Food consumption 

was not measured. The LC50 for females was determined to be >5000 mg/kg.

Subacute (28-day) Study

In the first 28-day repeat exposure study (MacKenzie 2009), male and female young adult SpragueDawley rats (10/sex/dose) were exposed to the following doses of MPHE once daily, for 28 total days: 0;

250; 500; or 1,000 mg/kg. The exposure did not adversely affect mortality, clinical signs of toxicity, food 

consumption or efficiency, body weight gains, hematology or clinical chemistry parameters, or gross 

necropsy. Significant increases in absolute and relative liver weights were noted in all dosed male and

female groups, with an associated, small increase (2/10) incidence of minimal centrilobular hypertrophy 

at 1,000 mg/kg. No histological effects were noted in any dosed females. Significantly increased 

absolute and relative kidney weights were also seen in dosed male rats, but not in females; however, there 

was no associated kidney histopathology in these male rats. The liver effects were considered by the study 

authors to be the result of an adaptive response to the presence of a xenobiotic; ICF agrees because of the 

lack of effects on liver cells (i.e., no adverse histopathology). There were incidental, small changes in 

some clinical chemistry parameters which were not considered adverse either because the changes were 

not consistently dose-dependent or they did not correspond with tissue damage: increased serum globulin 

 8 Ameloblastic cells produce enamel in the tooth.
Final—July 2, 2015

16

and glucose in female rats at the top two doses, and decreases in select enzymes/compounds (sorbitol 

dehydrogenase, creatinine, inorganic phosphorus). The NOAEL for this study is identified as 1,000 

mg/kg. 

In the second 28-day repeat exposure study (Akahoshi 2010), 5 male and female Sprague-Dawley rats 

were administered doses of 0; 100; 250; and 1,000 mg/kg via gavage (oral) once daily for 28 consecutive 

days. Because certain parameters were not measured (e.g., urinary analyses) this was not considered a 

guideline study. An additional 5 male and female control and high-dose (1,000 mg/kg) rats were exposed 

identically to the main group animals, and were then maintained post-dosing for 14 days to assess 

recovery. Exposure to MPHE did not affect clinical signs, parameters measured in a functional 

observational battery, mortality, food consumption, body weights, hematology, most clinical chemistry 

parameters, select urinalysis parameters, or gross necropsy findings. 

In males at 1,000 mg/kg, significantly increased serum cholesterol and total phospholipids were noted at 

the end of exposure. This is most likely the result of stress to the liver as a result of increased metabolic 

activity, which is noted in the increased absolute liver weights in these males and the presence of mild 

centrilobular hepatocellular hypertrophy in 1/5 males at 250 mg/kg and 3/5 males at 1,000 mg/kg. 

Significantly increased liver weight relative to body weight was noted at all three exposure doses in 

males, but in low- and mid-dose males, this is most likely the result of decreased mean body weights at 

the end of the study (compared to controls). Liver weights in exposed females were unaffected, but 1/5 

and 2/5 females at 250 and 1,000 mg/kg respectively did exhibit mild centrilobular hypertrophy and 1/5 

of the high-dose females also exhibited fatty periportal hepatocyte degeneration with resultant 

mononuclear cell infiltration. Females and males at 250 mg/kg showed significantly increased absolute 

and relative kidney weights, respectively, but these changes were not considered related to compound 

exposure as no other dose groups were affected. One high-dose male showed histological evidence of 

accumulation of alpha 2-mu globulin; this effect was not considered clinically relevant because it is malerat-specific and has no corollary in the human. In recovery animals, only 1,000-mg/kg males still 

exhibited significantly increased absolute and relative liver weights. Liver histopathology was resolved in 

high-dose males after recovery. The NOAEL was identified by the study authors as 1,000 mg/kg as the 

adaptive effects were not considered adverse and were reversible; ICF agrees that because the effects 

noted in this study were similar to those noted in the first 28-day study, the effects are indicative of 

adaptive response to a xenobiotic (i.e., increased cell size due to increased production of metabolizing 

enzymes) and are considered to be reversible and not adverse.
Final—July 2, 2015

17

Subchronic (90-day) Study

In a subchronic oral study (Anand 2011), groups of male and female Sprague-Dawley rats (15/group for 

controls and high-dose animals, 10/group for intermediate groups) were given the following doses via 

gavage once/day, 5 days/week, for 13 weeks: 0; 250; 500; and 1,000 mg/kg. At the end of the 90-day 

exposure period, 5 rats per sex at 0 and 1,000 mg/kg were maintained for 30 days post-dosing to 

determine the reversibility of any observed effects.

The exposure to MPHE did not affect the following measured parameters in any toxicologically 

significant way: 

• mortality,9

• clinical signs (including neurological parameters measured in a functional observation battery), 

• ophthalmology, 

• hematology or 

• gross necropsy.

Changes in liver and kidney weights and other measured parameters in exposed rats (main study) are 

provided below in Table 2. Mean terminal body weights of all male dosed groups were significantly 

lower than the controls (16%, 11%, and 9%, in the low-, mid-, and high-dose groups respectively). Mean 

body weight values for the 250-mg/kg-day male group were consistently lower throughout the study 

(including prior to dosing at day 0); this may partly be the result of a significantly decreased food 

consumption (compared to controls) that occurred throughout the study except for days 42-56. Food 

consumption levels of the 500- and 1,000-mg/kg-day males were comparable to controls throughout the 

exposure period. Overall mean body weight gains in the dosed groups were 76%, 83%, and 87%, 

respectively, of controls from day 0-91 (all values significantly decreased compared to controls). The 

study authors did not attribute decreased food consumption in the low-dose males to exposure to MPHE

because the behavior did not follow a dose-related trend; no potential mechanism for the decreased 

terminal body weights or deficits in overall body weight gain in all dosed male groups was offered in the 

study report. These deficits suggest a problem related either to the health of the male rats prior to the 

onset of exposure or to stress related to dosing methodology or treatment. Dosed females showed no 

changes in food consumption or efficiency compared to controls, and mean body weight gains were 

generally higher in dosed females than in controls, which are reflected in the mean terminal body weights 

(shown in Table 2).

 9 One control male in the recovery group was found dead after intubation on day 85.
Final—July 2, 2015

18

Table 2. Selected Organ Weights in Male and Female Rats Exposed to MPHE

Absolute and Relative Organ Weights (g) and Effects

Exposure Dose, mg/kg

0 250 500 1,000

Male, number of rats (10) (10) (10) (10)

Mean terminal body wt. 596.0 500.8* 528.1* 549.1

Liver

Absolute wt. 15.956 19.424* 20.553* 23.066*

Relative wt. (to body wt.) 2.668 3.882* 3.900* 4.196*

Hepatocellular 

hypertrophy

minimal 0 3 6 7

mild 0 0 0 1

Kidney

Absolute wt. 3.412 3.460 3.765 4.409*

Relative wt. (to body wt.) 0.573 0.694* 0.711* 0.801*

CPN, incidence 7 8 10 10

Severity, minimal 6 4 4 1

mild 1 4 6 9

Female, number of rats (10) (10) (10) (10)

Mean terminal body wt. 278.0 310.5* 288.4 291.1

Liver

Absolute wt. 7.314 9.127* 8.535* 8.833*

Relative wt. (to body wt.) 2.639 2.947* 2.953* 3.041*

Hepatocellular 

hypertrophy

minimal 0 0 1 4

mild 0 0 0 0

Kidney

Absolute wt. 1.828 2.190* 2.053* 2.017*

Relative wt. (to body wt.) 0.660 0.708 0.712 0.695

CPN, incidence 1 1 2 0

Severity, minimal 1 1 2 0

Source: Anand (2011)

*Statistically significant at p<0.05.
Final—July 2, 2015

19

Absolute and relative (to body weight) liver weights were significantly increased in all dosed male and 

female rats. In addition, minimal to mild hepatocellular hypertrophy, "characterized by an increase in the 

size of cells due to an increase in cytoplasmic volume," was present in a dose-dependent manner in all 

exposed male groups and in females at the top two doses (Anand 2011). Serum cholesterol was 

significantly increased in male rats at the top two doses (46% and 74% higher than controls), and in the 

recovery males, cholesterol levels were still statistically higher (26%) than controls. The difference in the 

recovery males was smaller than in the main study, indicating that the liver damage was reversible. 

Absolute liver weights in 1,000-mg/kg recovery males and females were not significantly increased over 

controls, but relative (to body weight) liver weights in 1,000-mg/kg males were still significantly

increased (see Table 3 below). These changes indicate that the increased metabolic burden posed by 

MPHE was having some cellular effect on the liver, which had not fully resolved at 30 days past the 

termination of exposure.

Table 3. Organ Weights and Incidence and Severity of Hepatocellular Hypertrophy in Livers and 

CPN in Kidneys of Recovery Rats

Finding Dose, mg/kg

0 1,000

Liver Weights (incidence of hypertrophy)

Absolute, male 15.001 (0) 17.457 (0)

Absolute, female 7.534 (0) 8.466 (0)

Relative to body weight, male 2.413 2.963*

Relative to body weight, female 2.488 2.780

CPN (Male) 3 4

Minimal 3 3

Mild 0 1

Source: Anand (2011)

*statistically significant at p<0.05.

The absolute and relative kidney weights in treated males were all significantly increased compared to 

controls in a dose-related fashion, although the increased relative kidney weights were affected by the 

lower terminal body weights of the dosed male rats. Absolute, but not relative, kidney weights of dosed 

female rats were also significantly increased compared to controls. CPN was noted in all male rats, and 

increased in severity in the dosed rats. CPN was also noted in female rats in the control, low- and middose groups, although the severity was "milder" than that observed in the males. CPN was not noted in 

control or high-dose recovery females, but it was noted in a smaller number of control males (3/4; 

minimal severity) and 1,000-mg/kg-day males (4/5; 3 with minimal severity, 1 with mild severity). 

Because of the decreased number of recovery animals compared to main study animals (5 rather than 10) 

it is not possible to determine if the incidence of CPN was decreased, but the severity of the effect does 

appear to have decreased.

All dosed male rats exhibited significant increases in urinary micro-total protein (83%, 186%, and 253%, 

respectively) compared to controls at the end of exposure, which corresponded to higher severity of CPN 

in these rats. There was also an increased incidence, not dose-related, in granular casts in the urine. Mean

urine volume was increased and specific gravity decreased, in mid- and high-dose males (these last two 

endpoints were highly influenced by the values of one male rat in each group, and the values for the 

remaining rats in each group were within historical ranges). Mean urine volume and specific gravity were 

similar in control and high-dose recovery males. Urinalysis parameters were not affected by treatment in 

dosed females.
Final—July 2, 2015

20

The study authors note that CPN is a common lesion in the aging rat, but can also be found in rodents as 

young as 2 months of age. The phenomenon is well-known in 13-week and 2-year toxicity studies 

conducted by the National Toxicology Program (Travlos et al. 2007) and is associated with a high-protein 

diet, NIH-07 (Seely and Hard 2008; Hard et al. 2009). It is noted that DuPont consistently uses in all its 

oral studies a diet with a protein content of 20%, which is intermediate between the old diet used by the 

NTP(NIH-07; 23% protein) and the new diet adopted in the 1990s (NTP 2000; 14% protein) (Hard et al. 

2009). It is possible that the diet used by DuPont has a high enough protein content to contribute to the 

development of CPN in its male and female rats. As noted previously, a few male rats in the acute 

inhalation study exhibited signs of CPN at the age of 2 months (2/5 control rats, with minimal severity; 

1/5 rats at 15,000 ppm, with minimal severity; no other dose groups were evaluated histologically). CPN 

was observed in a significant number of control and dosed male rats in the 90-day oral study; the presence 

of CPN in 2 control rats and 1 dosed rat in the inhalation study indicates that there may have been a 

predisposition for CPN in this particular strain of rat, or the potential for developing CPN in a very short 

period of time as a result of diet or other factors. 

The study report argues that no NOAEL was identified for male rats due to the presence of CPN in all 

male rat groups, but identifies a NOAEL for females at 1,000 mg/kg due to the absence of test-substancerelated effects. The author indicates that CPN is a kidney pathology unique primarily to the male rat with 

no known relevance to humans; the study author did, however, state that the increase in CPN severity was 

believed to be an adverse effect related to MPHE exposure. Some scientists do believe that CPN has no 

relevance to human health risk assessment (Hard et al. 2009; Seely and Hard 2008), but others have 

disagreed with that viewpoint (Melnick et al. 2012). Nevertheless, the high incidence of CPN in control 

rats makes an assessment of the kidney as a target organ for MPHE impossible. As such, CPN is not 

considered a toxicologically relevant endpoint for humans, and it does not inform the AEL for this 

compound.

Of greater importance for the development of the AEL, however, is the lack of relevance of oral exposure 

to an occupational worker. It is not believed that workers will be incidentally ingesting the study 

compound in any significant amounts. It is possible that like some perfluorinated alkanes which are also 

nephrotoxins, MPHE may be metabolized by glutathione conjugation, followed by ß-lyase dependent 

biotransformation to reactive intermediates (Iyer and Anders 1997; Anders 2008). However, even if 

metabolic studies were to indicate MPHE were metabolized in this fashion, the ß-lyase metabolism 

pathway in humans is 10-30 fold less active than in rodents (Anders and Dekant 1998; Gentz and Malan 

2001), suggesting that the effect in humans would be much less significant. As discussed previously, the 

inhalation pathway is the most relevant, and the 28-day inhalation study performed was used to determine 

the AEL.

Developmental Study

In a developmental assay, 22 time-mated female Sprague-Dawley rats were administered MPHE via 

gavage (oral) on gestation days (gd) 6-20 at doses of 0; 250; 500; and 1,000 mg/kg (Munley 2010). The 

dams were euthanized on gd 21 and the recommended reproductive and developmental parameters were 

evaluated. Exposure to the study compound did not affect any measured endpoint including those 

assessing maternal health and fetal development (e.g., fetal number or weight, as well as external, 

visceral, or skeletal alterations). It was noted in the study that the percentage of male rat pups was 

statistically significantly increased at 500 and 1,000 mg/kg. The study authors indicated that the 

statistical significance was likely a result of the low ratio of males in the control group, and ICF agrees. 

Furthermore, ICF notes the following:

• no changes in pre-or post-implantation loss were observed across the exposed groups, 
Final—July 2, 2015

21

• pup gender was established at conception, 

• the dams were purchased already mated and at gd 1, 2, or 3, and 

• the dams were not exposed to the study chemical until gd 6. 

Other than selective loss of female pups, which the aforementioned data disprove, there is no other 

mechanism by which exposure to the compound during this developmental period could increase the 

percentage of male pups. In addition, the ranges of male pups in this study are comparable to those found 

in more wide-ranging analyses (Stump et al. 2012). Therefore, ICF believes that the sex ratio in this study 

was unaffected by exposure to MPHE. The NOAEL was identified as 1,000 mg/kg by the study authors; 

ICF agrees.

V. Supporting Genotoxicity Studies 

The genotoxicity data for this study compound consist of a bacterial reversion assay, an assay evaluating 

chromosomal aberration in Chinese hamster ovary cells, and two micronucleus assays in rat blood cells 

following repeated oral and inhalation exposures (Myhre 2009; Glover 2009; Myhre 2012; DeLorme 

2014). All studies were determined to be negative, indicating that under the conditions used, MPHE

and/or its metabolites are not believed to be mutagenic or clastogenic. 
Final—July 2, 2015

22

VI. References

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Medience Corporation for EI duPont de Nemours and Company, Wilmington, DE. 21 December 2010.

Anand, S. S. 2011. [ ]: Subchronic toxicity 90-day gavage study in rats. E.I. du Pont de Nemours and 

Company, DuPont Haskell Global Centers for Health & Environmental Sciences, Newark, DE. 2 June

2011.

Anders, M.W. 2008. Chemical toxicology of reactive intermediates formed by the glutathione-dependent 

bioactivation of halogen-containing compounds. Chem. Res. Toxicol 21:145-159.

Anders, M.W., W. Dekant. 1998. Glutathione-dependent bioactivation of haloalkanes. Ann Rev 

Pharmacol Toxicol 38:501-537.

DeLorme, M. P. 2014. [ ]: Four-week inhalation toxicity study with micronucleus evaluation in rats. E.I. 

du Pont de Nemours and Company, Newark, DE. 2 July 2014.

Durando, J. 2009. [ ]: Acute oral toxicity--fixed dose procedure in rats. Eurofins Product Safety 

Laboratories Dayton, NJ for EI duPont de Nemours and Company, Wilmington, DE. 12 March 2009.

E.I. du Pont de Nemours and Company. 2013a. Additional information provided to SNAP from DuPont. 

27 May 2013.

E.I. du Pont de Nemours and Company. 2013b. Additional information provided to SNAP from DuPont. 

11 February 2013.

Gentz, B.A. and T. P. Malan. 2001. Renal toxicity with sevoflurane: a storm in a teacup? Drugs 61:2155-

62.

Glover, K. P. 2009. [ ]: In vitro mammalian chromosome aberration test in Chinese hamster ovary cells. 

E.I. duPont de Nemours and Company, DuPont Haskell Global Centers for Health & Environmental 

Sciences, Newark, DE. 26 June 2009.

Hard, G.C., J. K. Johnson, and S. M. Cohen. 2009. A comparison of rat chronic progressive nephropathy 

with human renal disease--implications for human risk assessment. Crit Rev Toxicol 39:332-346.

Iyer, R.A. and M.W. Anders. 1997. Cysteine conjugate ß-lyase-dependent biotransformation of the 

cysteine S-conjugates of the Sevoflurane degradation product 2-(fluoromethoxy)-1,1,3,3,3-pentafluoro-1-

propene (Compound A). Chem Res Toxicol 10:811-819.

Kegelman, T.A. 2011. [ ]: Inhalation acute exposure with anatomic pathology evaluation in rats. E.I. 

duPont de Nemours and Company, DuPont Haskell Global Centers for Health & Environmental Sciences, 

Newark, DE. 22 February 2011.

Mackay D., W. Y. Shiu, and K. C. Ma. 1993. Illustrated Handbook of Physical-Chemical Properties and 

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MacKenzie, S. A. 2009. [ ]: Repeated-dose oral toxicity 28-day gavage study in rats. E.I. duPont de 
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Nemours and Company, DuPont Haskell Global Centers for Health & Environmental Sciences, Newark, 

DE. 16 July 2009.

Melnick, R.L., K. M. Burns, J. M. Ward, et al. 2012. Chemically exacerbated chronic progressive 

nephropathy not associated with renal tubular tumor induction in rats: an evaluation based on 60 

carcinogenicity studies by the National Toxicology Program. Toxicol Sci 128:346-356.

Munley, S. M. 2010. [ ]: Developmental toxicity study in rats. E.I. duPont de Nemours and Company, 

DuPont Haskell Global Centers for Health & Environmental Sciences, Newark, DE. 10 August 2010.

Myhre, A. 2009. [ ]: Bacterial reverse mutation test. E.I. duPont de Nemours and Company, DuPont 

Haskell Global Centers for Health & Environmental Sciences, Newark, DE. 30 June 2009.

Myhre, A. 2012. [ ]: Rat blood micronucleus test. E.I. duPont de Nemours and Company, DuPont Haskell 

Global Centers for Health & Environmental Sciences, Newark, DE. 11 January 2012.

Seely, J. C. and G. C. Hard. 2008. Chronic progressive nephropathy (CPN) in the rat: review of pathology 

and relationship to renal tumorigenesis. J Toxicol Pathol 21:199-205.

Stump, D. G., M. D. Nemec, G. A. Parker, et al. 2012. "Significance, reliability, and interpretation of 

developmental and reproductive toxicity" in Hood RD, ed: Developmental and Reproductive Toxicology, 

A Practical Approach, 3rd Edition. London: Informa Healthcare. 2012.

Travlos, G. S., L. Betz, and G. C. Hard. 2007. The influence of diet or route of exposure on chronic 

progressive nephropathy, kidney weight, blood urea nitrogen and creatinine concentrations in 13-week 

toxicity studies for control F344/N male rats. Abstract. Toxicol Pathol 35:1.

United States Environmental Protection Agency (U.S. EPA). 1994. Methods for Derivation of Inhalation 

Reference Concentrations (RfCs) and Application of Inhalation Dosimetry. U.S. Environmental 

Protection Agency, Office of Research and Development, Office of Health and Environmental 

Assessment, Washington, DC, EPA/600/8-90/066F.