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Revised June 1996
Zineb
Trade and Other Names:
Trade names include Aspor, Chem Zineb, Devizeb, Dipher, Discon Z,
ethylene(bis)dithiocarbamate (EBDC), Hexathane, Kypzin, Lodaco,
Lonacol, Mancozan, Parazate, Parzate, Tiezene, Zebtox, Ziden, and
Zinosan. The compound may also be found in formulations with
other pesticides.
Regulatory Status:
Zineb was formerly registered in the U.S. as a General Use
Pesticide (GUP) and was rated as a pesticide of low toxicity -
EPA toxicity class IV. Products containing zineb were required to
carry the Signal Word CAUTION on the label. Following an EPA
Special Review of all the ethylene(bis)dithiocarbamate pesticides
(EDBCs), including zineb, all registrations for zineb were
voluntarily canceled by the manufacturer. All tolerances for
zineb in agricultural commodities in the U.S. (except grapes used
in winemaking) were revoked, effective 12/31/94. The tolerance
for grapes used in winemaking was revoked, effective 12/31/97.
Chemical Class:
dithiocarbamate
Introduction:
The EBDCs are dithiocarbamate fungicides used to prevent crop
damage in the field and to protect harvested crops from
deterioration during storage or transport. Zineb was used to
protect fruit and vegetable crops from a wide range of foliar and
other diseases. It was available in the U.S. as wettable powder
and dust formulations. Zineb can be formed by combining nabam and
zinc sulfate in the spray tank.
Formulation: It was
available in the U.S. as wettable powder and dust formulations.
Zineb can be formed by combining nabam and zinc sulfate in the
spray tank.
Toxicological Effects:
- Acute toxicity: The oral LD50 for zineb
in rats is 1850 to 8900 mg/kg, in mice is 7600 to 8900
mg/kg, and in rabbits is 4450 mg/kg. The LClo
(inhalation) in rats is 0.8 mg/L (4-hour). The dermal
LD50 in rats is over 2500 mg/kg, the highest dose that it
is possible to administer [3,4]. Zineb is slightly toxic
when ingested. Following a single large dose of zineb,
rats and mice exhibited incoordination, hyperactivity
followed by inactivity, loss of muscle tone, and loss of
hair [1,4]. Sheep died within 3 weeks of being given oral
doses of 500 mg/kg of zineb. In spray or dust forms,
zineb is moderately irritating to the skin, eyes, and
respiratory mucous membranes. It may also be a dermal
sensitizer, with possible cross sensitization to maneb
and mancozeb [4]. This irritation may result in itching,
scratchy throat, sneezing, coughing, inflammation of the
nose or throat, and bronchitis [40]. Early symptoms from
exposure of humans of zineb include tiredness, dizziness,
and weakness. More severe symptoms include headache,
nausea, fatigue, slurred speech, convulsions, and
unconsciousness [1,4]. These effects may be exacerbated
with concurrent exposure to alcohol. Acute neurotoxic
effects are probably due to carbon disulfide, a
metabolite of zineb [1]. Animal studies indicate that
changes in thyroid may occur following a single, large
dose [1], but that these may be reversible [1]. Ethylene
thiourea (ETU), a potentially toxic metabolite of zineb,
may be involved in thyroid effects [1].
- Chronic toxicity: The survival, growth,
and blood chemistry of dogs were not affected by dietary
levels up to 250 mg/kg/day for 1 year. However, thyroid
size and weight increases were observed at this dose
level. No effects on the thyroid were detected at 100
mg/kg/day [1]. In a 2-year study of rats fed 500
mg/kg/day, diminished growth, kidney pathology, and
increased thyroid weight and size were observed [1].
Sheep showed no adverse effects from dosages of 100 and
250 mg/kg/day for 19 weeks [1]. Occupational inhalation
of zineb can lead to changes in liver enzymes, moderate
anemia and other blood changes, increased incidence of
poisoning symptoms during pregnancy, and chromosomal
changes in the lymphocytes [4]. Liver functioning was
affected in workers exposed to zineb. Moderate anemia and
other blood changes were also reported in 150 workers
exposed to zineb in a chemical plant [1]. A 5-month study
of zineb showed that concentrations of 20 and 200 mg/L
caused decreases in the activity of cholinesterase, an
essential enzyme of the nervous system. Inhalation
exposure to zineb may decrease the size of the bronchial
passages [1]. Repeated or prolonged dermal exposure may
cause dermatitis or conjunctivitis [4]. Farm workers who
were repeatedly exposed to zineb, in fields sprayed with
0.5% suspension of the fungicide, reported severe and
extensive contact dermatitis [31]. Ethylene thiourea
formation during metabolism of zineb or other EBDC
pesticides, may potentially result in goiter, a condition
in which the thyroid gland is enlarged [2].
- Reproductive effects: It is advisable
that pregnant women avoid exposure to zineb, as it can
damage the fetus, as well as cause adverse reproductive
system effects [1,35]. A single intraperitoneal injection
of approximately 160 mg/kg of zineb in mice, during the
second half of pregnancy, resulted in abortions and weak
offspring. Oral doses of zineb, at a rate of 100
mg/kg/day for 2 months or more, produced sterility,
resorption of fetuses, and abnormal tails in offspring
[1,4]. After oral ingestion of zineb, similar
concentrations of ETU, a metabolite of this pesticide,
were found in both maternal and fetal tissues of rats.
- Teratogenic effects: Offspring of rats
given a near lethal oral dose of 2000 mg/kg/day of zineb
on days 11 or 13 of pregnancy, showed a high incidence of
skeletal malformations, as well as defects in the closing
of the neural tube, an embryonic tube that eventually
develops into the brain and spinal cord [12]. A very high
single oral dose of 8000 mg/kg to rats on day 11 of
gestation produced numerous deformities in the offspring
[1]. Teratogenic effects were also seen when pregnant
mice were given intraperitoneal injections of 150 mg/kg
[41]. In pregnant rats fed 5.0 mg/kg/day, the lowest dose
tested, developmental toxicity was observed in the form
of delayed hardening of the skull bones in offspring.
Zineb's metabolite, ethylene thiourea (ETU), may cause
abnormal fetal development [35]. It has been shown to be
teratogenic in hamsters, but not in mice [2].
- Mutagenic effects: Results of
mutagenicity assays of zineb and its metabolite, ETU, are
inconclusive [4]. The data suggest that zineb may be a
weak mutagen.
- Carcinogenic effects: Available data
clearly show that low doses of zineb are not
carcinogenic. Very high doses have caused tumors in some
test animals. In two strains of mice, the maximum
tolerated lifetime dose of zineb did not cause tumors.
Oral doses of 3500 mg/kg/week for 6 weeks caused one of
two mice strains tested to develop benign lung tumors
after 3 weeks [1]. Two rat feeding studies showed no
evidence of tumor formation [4]. Overall, evidence of
carcinogenicity in chronic oral feeding studies in rats
and mice is inconclusive, although they suggest it is not
likely to be carcinogenic in humans [1].
- Organ toxicity: Zineb appears to be
harmful to the thyroid, liver and muscles. Liver and
kidney injury was observed in autopsies done on sheep
that died after a 3-week exposure to oral doses of 500
mg/kg/day zineb [1]. Studies of the effects of zineb on
test animals have shown rapid reduction in the uptake of
iodine and swelling of the thyroid (i.e., goiter) [1].
- Fate in humans and animals:
Approximately 68 to 74% of ingested zineb was recovered
unchanged in the feces after administration at various
dietary levels. It is estimated that only 11 to 17% of an
oral dose of zineb was absorbed into the body from the
gastrointestinal tract of the rat [1]. In general, zineb
is rapidly excreted from the body following ingestion.
Zineb is metabolized in mammalian tissues into ETU and
carbon disulfide [1].
Ecological Effects:
- Effects on birds: Zineb is practically
nontoxic to birds. The oral LD50 for zineb in mallards
and young pheasants is greater than 2000 mg/kg [42].
- Effects on aquatic organisms: Zineb is
moderately toxic to fish. The 96-hour LC50 in perch is 2
mg/L [3,4].
- Effects on other organisms: Zineb is not
toxic to bees [3,4]. Little or no reduction in the
numbers of beneficial predatory and parasitic arthropods
was seen when zineb was used in Nova Scotian orchards at
recommended dosages. Mites appear to be sensitive to
zineb [15].
Environmental Fate:
- Breakdown in soil and groundwater: Zineb
is subject to chemical breakdown (hydrolysis) and is of
low persistence in soil. It adsorbs strongly to soil
particles and usually does not move below the upper layer
of soil [21]. For this reason, zineb is unlikely to
contaminate groundwater. Its bioactive half-life in the
field is 16 days. Within 4 months after a field planted
with alfalfa was sprayed, 99.7% of the applied zineb was
lost [19]. ETU, a metabolite of zineb, has been detected
(at 0.016 mg/L) in only 1 out of 1295 drinking water
wells tested [2].
- Breakdown in water: Zineb is practically
insoluble in water [3]. It is unstable in water and
hydrolyzes rapidly, producing ETU and other compounds
[19].
- Breakdown in vegetation: Zineb is
generally not poisonous to plants, except in
zinc-sensitive varieties, such as tobacco and cucurbits.
Pears have been slightly injured by this fungicide in a
few cases [4]. ETU is the major zineb metabolite in
plants [3].
Physical Properties:
- Appearance: Zineb is a light-colored
powder or crystal [3]. Zineb is a polymer of
ethylene(bis)thiocarbamate units linked with zinc.
- Chemical Name: zinc
ethylenebis(dithiocarbamate) [3]
- CAS Number: 12122-67-7
- Molecular Weight: 275.74
- Water Solubility: 10 mg/L @ 25 C [3]
- Solubility in Other Solvents: s. in
carbon disulfide; s.s. in pyridine; practically i.s. in
common organic solvents [3]
- Melting Point: Thermal decomposition @
157 C [3]
- Vapor Pressure: <0.01 mPa @ 20 C [3]
- Partition Coefficient: <1.3010 at 20
C [3]
- Adsorption Coefficient: 1000 (estimated)
[21]
Exposure Guidelines:
- ADI: 0.03 mg/kg/day [33]
- MCL: Not Available
- RfD: 0.05 mg/kg/day [27]
- PEL: Not Available
- HA: Not Available
- TLV: Not Available
Basic Manufacturer:
ELF Atochem North America
2000 Market Street
Philadelphia, PA 19103-3222
- Phone: 215-419-7219
- Emergency: 800-523-0900
References:
References for the information in this PIP can be found in
Reference List Number 4
DISCLAIMER: The
information in this profile does not in any way replace or
supersede the information on the pesticide product labeling or
other regulatory requirements. Please refer to the pesticide
product labeling.