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fenoprop (Silvex) Usage Suspension 2/79





Office of Pesticide Programs
February 28, 1979

Decision and Emergency Order Suspending Registrations for Certain Uses 
of 2-(2,4,5-Trichlorophenoxy) Propionic Acid (Silvex)

During the past two years, the Agency has been gathering information 
about the closely related phenoxy herbicides, 2-(2,4,5-trichlorophenoxy) 
propionic acid (silvex) and 2,4,5-trichlorophenxoy acetic acid (2,4,5-
T), as part of its Rebuttable Presumption Against Registration (RPAR) 
process in order to decide whether the registration of this pesticide 
should be continued.  This review was prompted by studies showing that 
silvex, 2,4,5-T, and/or their dioxin contaminant, 2,3,7,8-
tetrachlordibenzo-p-dioxin (TCDD) [Current methods for manufacturing 
silvex produce TCDD as a by-product of the manufacturing process.  
Although silvex manufacturers attempt to remove this contaminant, TCDD
cannot be completely removed.  An EPA contract laboratory has measured 
the TCDD content in 8 recently produced commercial samples of technical 
grade silvex from two different manufacturers.  The contractor reported 
that the TCDD content in these samples ranged from 0.012 to 0.024 ppm
TCDD (limit of detection: 0.01 ppm).  Therefore, because TCDD is present 
as a low-level contaminant in commercial samples of silvex, references 
in this document to "silvex" or the "pesticide product" mean silvex that 
is contaminated with TCDD.] caused reproductive and oncogenic effects
in test animals.  During the public debate initiated by the 2,4,5-T RPAR 
(43 FR 17116, April 21, 1978), the Agency received reports that women 
living in the vicinity of Alsea, Oregon, had miscarriages shortly after 
2,4,5-T was sprayed in the forest areas where they reside.  The Agency 
investigated the circumstances surrounding these reported miscarriages 
and compared the frequency of miscarriage in the Alsea area with 
comparable data from a control area.  The Agency has concluded that the 
use of 2,4,5-T over a six-year period in the Alsea area was related to a 
statistically significant increase in the frequency of miscarriages by 
women residents of the area, and that these miscarriages occurred 
shortly after the use of 2,4,5-T in the area where these women resided.

Based on this and other information, I am ordering several emergency 
suspensions under FIFRA Section 6(c), which halt the distribution, sale, 
and use of 2,4,5-T for forestry, rights-of-way, and pastures until the 
completion of further administrative proceedings.  Pasture is defined as 
land producing forage for animal consumption, harvested by grazing, 
which has annual or more frequent cultivation, seeding, fertilization, 
irrigation, pesticide application, and other similar practices applied 
to it. Fencerows enclosing pastures are included as part of the pasture.  
For details, see the risk discussion in Section IV of this document and 
the 2,4,5-T suspension document, published simultaneously with this 
document.  Because both silvex and 2,4,5-T are contaminated with TCDD, 
and because of similarities in chemical structure, manufacturing 
processes, use patterns, and effects in experimental systems, I consider
it prudent to take similar regulatory action against silvex.  I am 
therefore ordering emergency suspension of the forestry, rights-of-way, 
and pasture uses of silvex because I find that they pose an "imminent 
hazard" to humans and to environment; I also find that an "emergency" 
exists because there not enough time to hold a suspension hearing before
the next spraying season.

In addition, I am ordering the emergency suspension of the home and 
garden, aquatic weed control/ditch bank, and commercial/ornamental turf 
uses of silvex.  These additional uses of silvex are comparable to uses 
of 2,4,5-T cancelled or suspended in 1970 because of concern that 
exposure to 2,4,5-T and/or TCDD posed an imminent hazard to humans and 
to the environment.  I now make similar findings of imminent hazard for 
these uses of silvex.  I also find that an emergency exists relative to 
these uses because there is not enough time to hold a suspension hearing 
before the spring and early summer period of major silvex application 
for home and garden, aquatic weed control/ditch bank, and commercial/ 
ornamental turf uses.  In addition, I find that the year-round of silvex 
in certain areas of the country adds to the urgency of the situation for 
the home and garden and commercial/ornamental turf uses.

     A.  Standards for Maintaining a Registration

In order to obtain a registration for a pesticide under FIFRA, a 
manufacturer must demonstrate that the pesticide satisfies the statutory 
standard for registration.  That standard requires (among other things) 
that the pesticide perform its intended function without "unreasonable 
adverse effects" on the environment [FIFRA Section 3(c)(5)].  
"Unreasonable adverse effect on the environment" means "any unreasonable 
risk to man or the environment, taking into account the economic, social 
and environmental costs and benefits of the use of any pesticide" FIFRA 
Section 2(bb)].  In effect, this standard requires a finding that the 
benefits of each use of the pesticide exceed the risks of the use.  The 
burden of proving that a pesticide satisfies the registration standard 
rests with the registrant and continues for as long as the registration 
remains in effect [Environmental Defense Fund v. Environmental 
Protection Agency, 510 F.2d 1292, 1297 (D.C. Cir., 1975); Environmental 
Defense Fund v. Environmental Protection Agency, 465 F.2d 528, 532 
(D.C.Cir., 1972)].  Under Section 6 of FIFRA, the Administrator is 
required to cancel the registration, or change the classification, of a 
pesticide whenever he determines that the pesticide no longer satisfies 
the statutory standard for registration.