UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, DC 20460

			OFFICE OF  PREVENTION, PESTICIDES,  AND TOXIC SUBSTANCES

 

January 14, 2008

MEMORANDUM:

Subject:	Dietary and Drinking Water Exposure Chapter for
Tributlytin-Containing Compounds for the Reregistration Eligibility
Decision (RED) Document (Case 2620)

To:		Jill Bloom, Chemical Review Manager

		Special Review & Reregistration Division (SRRD)

From: 		Cassi Walls, Ph.D., Chemist

Risk Assessment and Science Support Branch (RASSB)

Antimicrobials Division (7510P)

Thru:		Norm Cook, Branch Chief

Risk Assessment and Science Support Branch (RASSB)

Antimicrobials Division (7510P)

DP Barcode: 		347646

Chemical Names:	Tributyltin oxide (TBTO)

	Tributyltin benzoate (TBTB)

	Tributyltin maleate (TBTM)

		

PC Codes:		 083001, 083106, 083118

CAS Registry No. 	TBTO:  56-35-9

			TBTB:  4342-36-3

			TBTM:  4027-18-3

Attached is a review of the dietary and drinking water exposures for the
antimicrobial uses of tributyltin-containing compounds (TBTO, TBTB, and
TBTM) to support the Reregistration Eligibility Decision (RED) document.



I.  SEQ CHAPTER \h \r 1  	Dietary Exposures to Tributlytin-Containing
Compounds

	The Antimicrobials Division (AD) assessed the potential dietary
exposures for the antimicrobial uses of tributyltin (TBT)-containing
compounds, tributyltin oxide (TBTO), tributyltin benzoate (TBTB), and
tributyltin maleate (TBTM).  

	TBT compounds can be used in following use sites where a potential for
food contact appears to exist:

Algicides in water cooling systems for pasteurization/canneries, soft
drink and food canning plants

Algicides in paper mills

Materials preservative in adhesives

	However, all of the TBT labels that have one of these use sites that
might pose a potential for contacting food, contain specific “non-food
contact” requirements or use directions that minimize the indirect
dietary exposure.  For example, the label of a product containing
directions for use in paper mills (EPA Registration #47371-29) contains
the statement, “Do not use in the manufacture of paper which will have
direct or indirect contact with food.”  At this time, no registrant
has indicated that it wishes to support of the use of TBT in
pasteurization/canning or paper mills.

	The registrants of products bearing labels with directions for use in
manufacturing adhesives have indicated that such adhesives are used in
applications such as attaching face fibers to carpet backing.  It should
be noted that TBTO has an FDA clearance under 21 CFR 175.105 as a
material preservative in adhesives for use in food packaging, implying 
that there is a potential for indirect dietary exposure.  However,
during the SMART meeting, the registrants indicated that they did not
intend to support this indirect food use.  Therefore, all of the TBTO
labels used as a materials preservative for adhesives must state “for
non-food contact adhesives.”    

	It should be further noted that although there are no FDA clearances
for any TBT compounds for the pulp and paper uses, the labels all state
for non-food contact paper.  In order  for AD to accept non-food contact
language for pulp and paper mill uses, examples of non-food contact
paper (i.e., newsprint, Kraft paper, brown paper mills, sheets for
corrugated board) must be listed on the labels.

 

	One registrant holds a registration for a product that is used to
manufacture household sponges, scouring pads, and sponge mop-heads. 
This registration (EPA Registration  #10466-28) contains the TBTM active
ingredient.  The use of TBTM will be assessed for incidental exposure
for food contact surfaces and floors in the ORE assessment.

	In the livestock operation use, hogs, cattle, and poultry are removed
prior to the microbiocide treatment and the feeding equipment is rinsed
prior to use.  The premises must be aired for 24 hours after treatment,
and another 24 hours must pass before animals can be returned to the
treated areas—a total of 48 hours after application. 

	AD assumes that removing animals prior to treatment and rinsing feeding
equipment after treatment results in negligible residues in the animals
living in treated facilities.  For this reason, AD does not typically
assess livestock premises.

	 In the case of the TBTO product used in animal housing facilities, the
Agency believes there may be a greater potential for animals to be
exposed, and thus, a potential for human dietary exposure.  This
potential is a result of the way in which such treatments are conducted
and the particular fate characteristics of TBT.  Specifically, 1) the
product label does not require rinsing or removal of TBT solution or
fogging residue after treatment (except for feed bowls not removed
during treatment), 2) animal premises may be treated frequently, and 3)
TBT is environmentally persistent and bioaccumulative.  The product
label should indicate that treated surfaces must be rinsed before
animals can be re-housed, although whether this is feasible when
applications are made with a fogger rather than by immersion, spraying,
mopping, or foaming is not clear.  Data are needed to improve our
understanding of the scope of actual exposures in animals exposed to TBT
via this use.  Data on the effectiveness of rinsing in removing TBT
residues from the treated premises, and residue data in the associated
food commodities will enable the Agency to further refine the assessment
of the animal premises use.  

	AD has, in the past, assumed that incubating eggs do not absorb
pesticide chemicals as the result of hatchery treatments, but data are
lacking to support the assumption.  The hatchery use of TBTO (hatchery
rooms, incubators, and hatchers) may pose a greater likelihood of 
producing residues in  eggs.  As discussed above, the environmental fate
characteristics of TBT may present additional opportunities for dietary
exposure.  The label of the one TBTO product registered for use in
hatcheries provides use directions for fogging equipment, and incubating
eggs are not removed from the premises during treatment.  The registrant
has indicated that eggs removed from the premises for repeated
applications of the product will not be viable.  In addition, premises
may be treated as frequently as once a day.  The label does not require
that surfaces exposed via fogging be rinsed after treatment, and
removing the residues left behind after fogging may not be adequately
achieved by rinsing.  A chemical like TBT, with its large potential for
persistence and bioaccumulation, could pose an increased risk of
residues in eggs relative to other pesticides of lesser persistence and
bioaccumulative potential.  Data appropriate for use in examining the
assumption that this pesticide does not penetrate eggshells in
incubation would facilitate a quantitative assessment of dietary
exposures resulting from the use of TBT in hatcheries.

II.  	Drinking Water Exposure to Tributlytin-Containing Compounds

	AD assessed the potential drinking water exposures for the
antimicrobial uses of tributyltin-containing compounds, tributyltin
oxide (TBTO), Tributyltin benzoate (TBTB), and Tributyltin maleate
(TBTM).  Based on the use patterns, the potential for TBT, TBTM, or TBTO
to impact drinking water sources is negligible and therefore a
quantitative drinking water assessment was not conducted.  However, data
are lacking to characterize the effectiveness of water used to rinse
animal housing facilities after treatment, and conversely, the fate and
concentrations of TBT in the rinse water.

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