UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF                  

PREVENTION, PESTICIDES AND 

TOXIC SUBSTANCES        

February 5, 2007

Memorandum

SUBJECT: 	AD’s Revised Occupational and Residential Exposure Chapter
for the Propylene and Dipropylene Glycol Reregistration Eligibility
Decision (RED) Document.

Case No. 3126.  PC Codes 068603, 068604. 

FROM: 	Timothy Leighton, Environmental Scientist

Regulatory Management Branch II

Antimicrobials Division (7510P) 

TO:		SanYvette Williams-Foy, Science Coordinator

		Antimicrobials Division (7510P)

				And 

		Michelle Centra, Chemical Review Manager (CRM)

		Diane Isbell, Acting Team Leader

		Mark Hartman, Branch Chief

Regulatory Management Branch II

Antimicrobials Division (7510P) 

Executive Summary

	Propylene and dipropylene glycol are bacteriocides and
fungicides/fungistats.  Propylene glycol is registered as an air
sanitizer, insecticide (flea and mites), and as a hard surface
disinfectant.  Dipropylene  glycol is registered only as an air
sanitizer.  There is potential for dermal and inhalation exposures
occurring during and after the use of propylene and dipropylene glycol
in commercial/institutional premises, residential/public access
premises, and various applications for medical premises and equipment. 
In addition, the Antimicrobials Division’s Toxicology Endpoint
Selection Committee (ADTC) concluded that the toxicity data base for
propylene and dipropylene glycol is adequate for hazard
characterization.  However, the ADTC has determined that there are no
toxicological endpoints of concern.  Based on a review of available
toxicity data, there is no evidence of dermal toxicity and no adverse
effects in repeated dose inhalation toxicity studies up to and exceeding
the limit dose of 1 mg/L.  Therefore, no risks have been quantified for
the use of these chemicals.

Introduction

	The Occupational and Residential Exposure Chapter of the Propylene and
Dipropylene  Glycol Reregistration Eligibility Decision (RED) Document
addresses potential exposures and risks to humans who may be exposed in
“occupational settings” and the general population in “residential
settings.”  An occupational and/or residential exposure risk
assessment is required for an active ingredient if (1) certain
toxicological criteria are triggered and (2) there is potential exposure
to handlers (mixers, loaders, applicators, etc.) during use or to
persons entering treated sites after application is complete. For
propylene and dipropylene glycol, there are potential exposures, however
there are no toxicological endpoints of concern, according to a review
of the available toxicity data by the Antimicrobials Division
Toxicological Committee (ADTC) (USEPA, 2004).  The acute toxicity
profile is presented in Table 1 (USEPA, 2004).  Both propylene and
dipropylene glycol are listed as toxicity category IV for all routes of
exposure.

Table 1.  Acute Toxicity Profile of Propylene/Dipropylene Glycol



Guideline	

Study Type	

Results	

Toxicity Category



Propylene Glycol



870.1100	

Acute Oral - Rat	

LD50 range = 8000 - 46000 mg/kg	

IV



870.1100	

Acute Oral - Mouse	

LD50 = 24800 mg/kg	

IV



870.1100	

Acute Oral - Rabbit, Guinea pig	

LD50 range = 18350 - 19600 mg/kg	

IV



870.2400	

Acute Eye Irritation - Rabbit	

non irritant	

IV



870.2500	

Acute Skin Irritation - Rabbit	

non irritant	

IV



870.2600	

Skin Sensitization	

non sensitizer	

N/A



Dipropylene Glycol



870.1100	

Acute Oral - Rat	

LD50 > 5010 mg/kg	

IV



870.1100	

Acute Oral - Rat	

LD50 range > 5000 to >15000 mg/kg	

IV



870.1200	

Acute Dermal - Rabbit	

LD50 > 5010 mg/kg	

IV



870.1200	

Acute Dermal - Rabbit	

LD50 > 2000  mg/kg	

IV



870.1300	

Acute Inhalation - Rat	

LC50 > 2.34 mg/L	

IV



870.2400	

Acute Eye Irritation - Rabbit	

slight irritant	

IV



870.2400	

Acute Eye Irritation - Rabbit	

slight irritant	

IV



870.2500	

Acute Skin Irritation - Rabbit	

non irritant	

IV



870.2600	

Skin Sensitization - Guinea Pig	

non sensitizer	

 N/A

 N/A = Not applicable

Characterization of Uses

	Propylene and dipropylene glycol products can be used where exposure
may occur in both occupational and non occupational settings. Propylene
glycol is currently used in as an air sanitizer, hard surface
disinfectant, and as an insecticide.  Use sites include, but not limited
to,  household pets, eating establishments, air sanitization, laundry
equipment, and hospital and medical premises.  Although the air
sanitizer use is intended only for applications in 
industrial/institutional settings, the potential for exposure to the
general population exists as a result of these applications in areas
such as theaters, hotels, schools, airplanes, etc.  Propylene glycol is
formulated as a pressurized liquid.  It is formulated at 0.25 percent
for the disinfectant, up to 10 percent for pet uses, and from 0.25 to
5.13 percent for air sanitizers.  Application rates vary.  The high end
air sanitizer rate is 7 ounces of product per 6,000 ft3 or 0.022 lb
ai/6,000 ft3 (EPA Reg. No. 10807-38).  Dipropylene glycol, on the other
hand, is only used as an air sanitizer.  The two products containing
dipropylene glycol are formulated at approximately 4 percent.  The
products are used as aerosol sprays (metered delivery devices). 
Application rates are 6.2 ounces (weight basis) of a 4 percent product
per 6,000 ft3 and 7 ounces (weight basis) of a 3.43 percent product per
6,000 ft3.  These rates are equivalent to 0.015 lb ai/6,000ft3.  Table 2
lists the active EPA registration numbers of the products containing
propylene and dipropylene glycol. 

	Table 2.  EPA Registration Numbers for Propylene and Dipropylene Glycol
Products

Use Category	Formulation	EPA Registration Numbers

Propylene Glycol

Disinfectant/Sanitizer	Pressurized Liquid	4822-491

Air Sanitizer	Pressurized Liquid	10807-7, -24, -26, -37, -38, -39, -43,
-72

51838-1, -2

Flea Spray 

(dogs, cats, etc)	Pressurized Liquid	4758-151

11715-243

Mite and Lice Control (Birds)	Pressurized Liquid	11715-20



Dipropylene Glycol

Air Sanitizer	Pressurized Liquid	9444-19, -136





Potential Exposures

	

	The potential handler scenarios identified are illustrated in Table 3. 
These scenarios were selected based on examination of product labels.  
Because air disinfectants can be applied in a wide variety of rooms, the
list of possible application scenarios is exhaustive.  		

Table 3.  Propylene and Dipropylene Glycol Handler Scenarios

Antimicrobial Use Site Category	Scenario

Commercial, institutional and industrial premises and equipment	• 
Spraying disinfectant in rooms of institutions, offices, schools,
motels, hotels, etc.

Residential and public access premises	•  Spraying disinfectant in
rooms such as lobbies, theaters, reception rooms, sleeping rooms,
bathrooms, etc.

•  Spraying pest control spray on caged birds and to small animals
(e.g., dogs/cats)

Medical premises and equipment	•  Spraying disinfectant on surfaces in
hospitals and nursing homes.

•  Spraying disinfectant in hospital rooms.



No chemical-specific handler data were submitted to estimate the
potential exposures associated with these uses of propylene and
dipropylene glycol (nor are they required at this time).  Specifically,
exposure data associated with spraying an aerosol can indoors, away from
any surfaces (i.e., air sanitizer), or with spraying pets, are
unavailable.  However, similar exposures associated with spraying
surfaces (i.e., aerosol cans), such as crack and crevice treatments, are
available from data provided by the Chemical Manufacturers Association
(CMA) Antimicrobial Assessment Study (EPA, 1999) and the Pesticide
Handlers Exposure Database (PHED).  The PHED exposure data for aerosol
can spraying is deemed more appropriate then the CMA data (e.g., more
replicates, better analytical recovery values, etc).  However, because
no toxicological endpoints of concern were identified, the exposures
have not been quantified.

	In addition to potential dermal and inhalation handler exposure, there
is the potential for postapplication exposure to individuals reentering
treated rooms and/or contacting sprayed surfaces.  OPPT/EETD has
developed a model, EFAST (Exposure and Fate Assessment Screening Tool),
to estimate air concentrations.  More information and access to the
EFAST model is available at   HYPERLINK
http://www.epa.gov/opptintr/exposure/
http://www.epa.gov/opptintr/exposure/ .  In summary, EFAST Version 1.0
bases its air concentration estimates on physical/chemical properties. 
Potential air concentration estimates for the gylcols could be developed
based on the model’s standard input parameters.  Postapplication
inhalation exposure would expected to be from both the aerosol (e.g.,
air sanitizer is metered spray every 15 minutes) and the vapor phase. 
The following information is presented in the EFAST model:

“For a "Product Sprayed on Surface," such as a fabric protector or an
aerosol paint, a portion (default of 1%) is assumed to be aerosolized
and is therefore immediately available for uptake by inhalation.  The
remainder is assumed to contact the target surface, and to subsequently
volatilize at a rate that depends upon the chemical's molecular weight
and vapor pressure.”

	No estimates are available to determine the spray deposition, if any,
on surfaces to estimate potential dermal contact.

Conclusion

	Based on the lack of toxicological concerns for propylene and
dipropylene glycol, a quantitative risk assessment is not necessary at
this time.  If inhalation toxicological endpoints are identified in the
future, a screening-level occupational and/or residential inhalation
exposure estimate is available using EFAST and PHED.  If dermal
toxicological endpoints are identified in the future, potential dermal
exposure estimates from treated surfaces may need to be developed.

References

USEPA. 1998. PHED Surrogate Exposure Guide. Estimates of Worker Exposure
from the Pesticide Handler Exposure Database Version 1.1.   Washington,
DC:  U.S. Environmental Protection Agency.

  SEQ CHAPTER \h \r 1 USEPA. 1999.  Evaluation of Chemical Manufacturers
Association Antimicrobial Exposure Assessment Study (Amended on 8
December 1992).  MRID No. Memorandum from Siroos Mostaghimi, PH.D.,
USEPA to Julie Fairfax, USEPA. Dated November, 4 1999.  DP Barcode
D247642.

USEPA. 2004.  PROPYLENE GLYCOL/DIPROPYLENE GLYCOL – Report of the
Antimicrobials Division Toxicity Endpoint Selection Committee (ADTC). 
Memorandum: T. McMahon, Ph.D, Chair, July 20, 2004. 	

