  SEQ CHAPTER \h \r 1 

									February 5, 2007

MEMORANDUM

SUBJECT:		Science Chapter: Revised Environmental Fate Studies and
Environmental Fate Assessment of Dipropylene Glycol

FROM			A. Najm Shamim, Ph.D., Chemist

			Regulatory Management Branch II

			Antimicrobials Division (7510P)

To:			Sanyvette Williams, Science Coordinator for

			Propylene and Dipropylene Glycols RED

			Antimicrobials Division (7510P)

					And 

			Michelle Centra, Chemical Review Manager

			Diane Isbell, Acting Team Leader

			Mark Hartman, Branch Chief

			Regulatory Management Branch II

			Antimicrobials Division (7510P)

					

	Environmental Fate Science Chapter and Fate Assessment on Dipropylene
Glycol is submitted for Reregistration Eligibility Decision (RED).

EXECUTIVE SUMMARY

	Environmental Fate Assessment:

	Dipropylene glycol has a log KOW of -1.07 and is not bioaccumulative. 
Highly miscible in water, dipropylene glycol does not hydrolyze, has a
low binding constant with soils, and is very mobile in soils.  Due to
high mobility in soil and slow biodegradation, the possibility exists
for dipropylene glycol to contaminate ground and surface water systems
if outdoor use occurs.  However, considering the registered pesticide
uses, this is not likely.  Soil grab samples and river die-away test
data pertaining to the biodegradation of dipropylene glycol in soil and
natural waters were not available from the open literature.  A few
aerobic biological screening studies that utilized settled waste water,
sewage or activated sludge for inocula, indicate that dipropylene glycol
should biodegrade slowly in the environment. The air half-life is
estimated to be 13 hours due to the induced photochemical reaction with
hydroxyl-radical in the atmosphere; hence, its presence in the
atmosphere is not likely to pose any problem.

	Environmental Fate Science Chapter For Dipropylene Glycol:

	Dipropylene Glycol is registered with OPP as an active product and is
used as a solvent, and a plasticizer in polyester and alkyd resins, and
in reinforced plastics.  OPP has no data base on environmental fate
studies for dipropylene glycol as a solvent or plasticizer.  For the
reregistration eligibility decision (RED) process, the Agency has relied
on the fate properties of Dipropylene Glycol obtained from the open
literature. The following fate properties were obtained from an open
literature search. 

	Vapor Pressure: 3.19 x 10-2 mm Hg at 25 oC (1)	

	Henry law Constant (air/water partition coefficient): 3.58 x 10-9
atm-cu m/mole at 25 oC (1)

	KOC (organic carbon ratio in soil): 6 (1)

	Log KOW (octanol/water partition coefficient):  - 1.07 (1)

	Does not Photolyze as it does not absorb UV light at wave length > 290
nm (1)

	Soil grab samples and river die-away test data pertaining to the
biodegradation of dipropylene glycol in soil and natural waters were not
available in open-literature.  A few aerobic biological screening
studies, which utilized settled waste water, sewage or activated sludge
for inocula, indicate that dipropylene glycol should biodegrade slowly
in the environment. (2, 3)

	Miscible in water (1)

	Does not undergo direct air photolysis, but half life in air
(estimated) is 13 hours due to induced photochemical reaction of
atmospheric hydroxyl radical.  Physical removal of dipropylene glycol
from air by precipitation and dissolution in clouds may occur.(4)

	Low absorptivity and therefore very high mobility in soil. (1)

	Aquatic hydrolysis, oxidation, volatilization, bioconcentration, and
absorption to sediment are not expected to be significant fate processes
for dipropylene glycol because of its high miscibility in water and lack
of a hydrolyzable hydrogen within its chemical structure.  Because of a
low Henry’s Law Constant, it has a low potential to partition from
surface water to air.  Dipropylene glycol has low absorptivity and
therefore, highly mobile in soil.  Biodegradeability of dipropylene
glycol should be slow, but may still be an important removal mechanism
from aerobic soil.  The low KOW indicates that it is not likely to
bioaccumulate in aquatic organisms like fish.  With a vapor pressure of
0.129 mm Hg at 25 oC, dipropylene glycol exists almost entirely in the
vapor phase in the atmosphere and degrades rapidly by reaction with
photochemically produced hydroxyl radicals (half-life of 13 hours). 

	Surface Water and Ground Water Contamination:

Dipropylene glycol may be released into surface water and ground water
via effluents at sites where it is produced or used as a solvent,
plasticizer or in reinforced plastic.  Due to the high mobility in soil
and the slow biodegradation, the possibility exists for dipropylene
glycol to contaminate water systems.

					

					BIBLIOGRAPHY

	Hazard Substances Databank (HSDB), A Database of the National Library
of Medicine’s TOXNET System.

	Bridie A, et al. (1979) “BOD and COD of some petrochemical.”  Water
Research 13: 627-630.

	Niemi G, et al.  (1987) “Structural features associated with
degradable and persistent chemicals.”  Env Toxicol Chem 6: 515-527.

	Environmental Fate Database.  A Database of the Syracuse Research
Corporation (SRC). 

