United Satm Wiea of Pnticidm and Toxic Subnincn
Environmenal Prottction Otfica o< Periods Proqrimi (TS-766C)
Agency Washington. DC 20460
&EPA Pesticide
Fact Sheet
Name of Chemical: DINOSEB
Reason for Issuance: Special Review/Emergency Suspension
Date Issued: October, 1986
Fact Sheet Number: 130
1. Description of Chemical
Common Name: Dinoseb (includes parent chemical as well
as four salts)
Chemical Name: 2-{sec-butyl)-4,6-dinitrophenol
Trade Names: DNBP, DNOSBP, "dinitro", dinoseb (F-ISO),
Caldon, Sinox, Vertac General and Selective
Weed Killer, Basanite, Chemox General & PE,
Chemsect, Dinitrex, Dinitro-3, Dinitro
General, Drexel Dynamite 3, Dynamite,
Elgetol 318, Gebutox, Hel - Fire, Kiloseb,
Nitropone C, Subitex, Unicrop DNBP, Vertac
Dinitro Weed Killer 5, Dynanap, Premerge
Plus,with Dinitro, and Klean Krop.
EPA Shaughnessy Code: 037505
Chemical Abstracts Service (CAS) Number: 88-85-7
Year of Initial Registration: 1948
Pesticide Type: Fungicide, Herbicide, Insecticide,
Desiccant
Chemical Family: Dinitrophenol
U.S. and Foreign Producers: Baird and McGuire, Uni^1
Chemical Company, Cedar Chemical Corp., Hoechst AG, S.H.
Marks Co. Ltd., Universal Crop Protection Ltd., S.N.P.E.,
Combinatal Chimic Fararar.
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2. Use Patterns and Formulations
Dinoseb is a contact herbicide widely used tocontrol
broadleaf weeds. Approximately 180 registered products
contain dinoseb (or its 4 salts) as an active ingredient.
The four salt formulations are alkanolamine, triethanolamine,
sodium and ammoniuzn. Between 7 and 11 million pounds of
dinoseb active ingredient are sprayed annually as a
liquid from airplanes, tractor—drawn equipment and hand
held equipment. The major use sites by volumne include
soybeans (40%), cotton (15%), potatoes (16%), peanuts
(9%), alfalfa (4%), snap beans (2%), peas (2%), grapes
(2%) and almonds (1%).
° Uses of Dinoseb
Agricultural Uses: Food Crops — alfalfa, almonds, c] .overs,
apples, apricots, barley, beans, blackberries, blueberries,
boysenberries, cherries, citrus, corn, cotton, cucurbits,
currants, dates, figs, garlic, gooseberries, grapes,
hops, loganberries, nectarine8, oats, olives, onions,
peaches, peanuts, pears, peas, pecans, plums 1 potatoes,
raspberries, rye, soybeans, strawberries, walnuts, and
wheat. Terrestrial Non—Food Crops — clovers, birdsfoot
trefoil, dichondra, flax, and timothy.
Aquatic Management: drainage ditches
Ornamentals: bulbous iris, daffodil, gladiolus, ligustrum,
lilac, narcissus, roses spirea, tulip, yew.
Forest Management: brush control, conifer release.
Methods of Application: aerial 1 tractor—drawn ground boom,
hand—held sprayer.
• Types of Formulations: The majority of products are soluble
and emulsifiable concentrates. Other formulations include
granular and flowabte concentrates.
3. Scientific Findings
° Chemical Characteristics
Dinoseb is a dark brown/reddish brown solid or viscous
liquid with a pungent odor. Depending on the technical
formulation, dinoseb is soluble ira toluene, petroleum oil,
ether, ethyl alcohol, ethanol, n—heptane, slightly soluble
in water, and miscible in ethyl ether and xylene. Dinoseb
has a melting point range from 30—34°C. Technical dinoseb
contains at least 90 percent active ingredient.
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Toxicological Characteristics
Dinoseb causes developmental toxicity in laboratory animals
and may pose a risk of birth defects in pregnant women.
Biologically and statistically significant increases in
malformations and/or anomalies were observed in a recently
submitted rabbit teratology study. The primary malformations
or anomalies observed were in the neurological and skeletal
systems. Based upon a NOEL of 3/mg/kg/day, the Agency
has calculated Margins of Safety (t’tDs). At all use sites
the f 1DS is less than 100, and in many cases less than 1.
The risk of birth defects is greatest for those women exposed
at the dinoseb application site.
Dinoseb is acutely toxic to humans and has been classified
into Toxicity Category I (acute oral LD 50 rat = 40—60 mg/kg).
Several human fatalities have been attributed to dinoseb
piosonings. The EPA Toxicity Peer Review Committee has
tentatively concluded that dinoseb be classified as a Category
C carcinogen (limited evidence of carcinogenicity in animals)
due to statistically significant elevations of liver
adenomas in the mid and high dose groups of test animals.
Studies in laboratory animals Indicate that dinoseb has
the potential to cause male sterility, cataracts, and
damage to the immune system. Also, several formulations
are contaminated with nitrosamines (cancer causing
substances).
• Physiological and biochemical behavorial characteristics
Dinoseb interferes with the basic energy metabolism of
cells. Specifically, it uncouples” oxidative phosphor—
ylation by preventing the conversion of adenosine di-
phosphate (ADP) to adenosine triphosphate (ATP). This is
a basic energy conserving step in cell biochemistry and,
when disrupted, results in other cellular changes such as
increased oxygen uptake and increased permeability of
mitochondria to hydrogen ions.
The above effect on energy metabolism may be a common de-
nominator for all toxic events observed in man and laboratory
animals when exposed to dinoseb.
• Environmental Characteristics: Available data indicate
that dinoseb has the potential to leach to groundwater.
Residues in the range of 1—5 ppb have been found in ground-
water in potato growing regions of New York, Maine, and
Massachusetts.
• Ecological Characteristics: Dinoseb is highly toxic to
birds, mammals, and invertebrates and may pose a risk to
non target organisms including endangered or threatened
species.
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° Tolerance Assessment: Tolerances were established in 40
CFR 180.281 for residues of dinoseb and its hydrolyzable
salts.
4. Summary of Agency’s Regulatory Position and Rationale
After considering a range of regulatory options to miti-
gate exposure to dinoseb, the Agency has decided to emergency
suspend all registrations. Data indicating that the use
of dinoseb may pose a risk of inducing developmental toxic
effects in humans is the basis for this action. This risk
is presented not only to mixers, loaders and applicators of
dinoseb, but also to persons entering treated fields or ex-
posed through spray drift. There is no hazard to persons
consuming food that has been treated with dinoseb. In
conjuncture with this action, a Notice of Intent to Cancel
all dinoseb registrations has been issued. The Administrator
has determined that continued registration of dinoseb
poses an imminent hazard during the period in which
administrative hearings could delay the effectiveness of
the cancellation of these registrations.
• Benefits Analysis: Suspension o all herbicide, fungicide
and desiccant uses of dinoseb would be expected to result
in first year losses primarily at the farm level of $80
to 90 million.
5. Contact Person
Michael. McDavit
Special Review Branch, Registration Division
Office of Pesticide Programs (TS—767C)
401 M Street, S.W.
Washington, D.C. 20460
(703) 557—1787
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