MEMORANDUM                                                              
             

September 29, 2005

SUBJECT:		Science Chapter on: Environmental Fate Studies and
Environmental Fate Assessment of Iodine

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

Regulatory Management Branch II

Antimicrobials Division (7510C)		

To:			Michelle Centra, Science Coordinator of Iodophors RED

Regulatory Management Branch II

Antimicrobials Division (7510C)

And

Heather Garvie , Chemical Review Manager for Iodine and Iodophors

Regulatory Management Branch II

Antimicrobials Division (7510C)

Thru:			Ben Chambliss, Team Leader,

Regulatory Management Branch II

Antimcrobials Division (7510C)

And

Mark Hartman, Chief

Regulatory Management Branch II

Antimicrobials Division (7510C)

Enclosed is the Environmental Fate Science Chapter Environmental Fate
Assesssment for the Reregistration Eligibility Decision (RED) for
Iodine/ Iodophors

Environmental Fate Science Chapter and Fate Assessment of
Iodine/Iodophors 

EXECUTIVE SUMMARY

Environmental Fate Assessment:

Iodine itself is an element ubiquoutously presnt in water , air, and
soils. It is a part of human diet. Iodine is not likely to volatilize
from iodophors due to lower vapor pressure.  Both iodine and iodophors
may be immobile to moderately immobile in soils and  iodine as iodide 
and iodate exist in water and the iodophor use is not likely to
contaminate the surface waters. Estimated log Kow is about 2.5 which
makes it less likely to bioaccumulate in aquatic organisms like fish.

APPENDIX 

 

Environmental Fate Science Chapter for Iodine and Iodophors

Iodine is a naturally occurring chemical, and iodine and potassium
iodide in iodophors are registered with Office of Pesticides Program
(OPP) as an actives. Iodine is listed as an inorganic substance under
Group 1 for Case No. 3080.  Iodine falls under the reregistration of
Iodine, Iodine Compounds and Complexes.   OPP has no database on
environmental fate studies. on iodine.  For the Reregistration
Eligibility Decision (RED) process the Agency has relied on open
literature and fate properties of iodine obtained from open literature.
The following fate properties were obtained from an open literature
search. 

	

Vapor Pressure of Iodine: .0.305 mm Hg at 25 oC (1)	

Henry law Constant (air/water partition coefficient): N/A

KOC (organic carbon ratio in soil): N/A

Log KOW (octanol/water partition coefficient): 2.49(1)

Exists in free gaseous form in the atmosphere(1)

Undergoes photochemical reactions in the atmosphere to form iodine
radicals.  The radicals may go on to form various other iodine
species.(1)

Iodine residence time in the atmosphere is 14 days for inorganic
particulates, 10 days for inorganic gases, and 18 days for organic
gases.(1)

Aquatic Bioconcentration Factor in fresh water for iodine is 40 for
algae, 5 for invertebrates, and 15 for fish.(1)

Aquatic Bioconcentration Factor in salt water for iodine is 4,000 to
10,000 for algae, 50 to 100 for invertebrates, and 10 to 20 for fish.(1)

Certain seaweeds and algae can concentrate iodine to levels of 0.8 - 4.5
g/kg of dried material.(1)	

Kds: -0.22 mL/g for chlorite minerals and 15.4 mL/g for illite
minerals.(1)

 Iodine is not hydrolyzed in water as other halogens proceeding it in
the halogen family. It is photolytically unstable in the atmosphere as
it can form iodine radicals.

The transfer of iodine  from air, water, and land may  is due to the
volatility of iodine.  The wet deposition of iodine is  predominantly
deposited into soil.  Iodine in water exists as iodide and iodate at a
55:45 ratio.  Mobility of iodine in soil depends on the soil porosity,
saturation and the amount of organic matter and iron/ aluminum oxides in
the soil.  In most soils it is immobile to moderately immobile.  There
is little evidence of iodine bioaccumulation in the food chain, even
though freshwater and marine fish concentrate iodine in the tissues.    

For antimicrobials uses, Iodine/ KI used with carrier molecules
(iodophors), the vapor pressure of pure iodine (0.30 mm Hg) decreases to
6.6 x10-6 mm Hg2 and hence the volatilization process from water, soils
will also be considerably decreased. The Agency at this time, does not
have any data to quantitate the reduction in volatilization processes. 
Similarly Agency lacks data about degradation processes of the iodine
carrier molecules (iodophors). At this time the Agency does not have
concerns for the degradation of iodine carrier molecules in soil, air or
water. 

OPP(s Lower Risk Pesticide Chemical Group (LRPCG) in its Science
Assessment for iodine chemicals as active and inerts, did not observe
any real or potential environmental concerns for these pesticides
(Chemicals assessed were: Iodine, Potassium Iodide, Sodium Iodide,
Hydroiodic Acid, Potassium Iodate)3

Surface Water and Ground Water Contamination:

Iodine is a naturally occurring chemical, which exists in water as
iodide or iodate.  Microbial action converts iodide to organic forms of
iodine, primarily methyl iodide.  The low vapor pressure and limited
solubility of methyl iodide in water promote the volatilization of
methyl iodide from surface waters to the surrounding atmosphere.  Iodine
has a low probability of surface and ground water contamination due to
the low mobility of iodine in soil and volatilization in surface waters.
With iodine present in the iodine carrier molecules (iodophors), the
volatilization will decrease and hence idophors possibly remain immobile
in soils. 



BIBLIOGRAPHY

MRID# 					CITATIONS

1.	ATSDR (Agency for Toxic Substances and Disease Registry). 
Toxicological Profile for Iodine.  U.S. Department of Health and Human
Services.  April 2004. 

. 		2.	Calculations of the Maximum Atmospheric Iodine Concentrations
From Solutions of Iodophors, A Memo Submitted by Iodophors Joint Venture
Group, Nov. 24, 2004

Science Assessment for Iodine Chemicals, drafted by: Lower Risk
Pesticide Chemical Focus Group, September, 2004.

