Amitrole

61-82-5

ammonium thiocyanate
atrazine
bromacil
linuron
simazine
2,3,6-trichlorobenzoic acid

Herbicide, plant growth regulator, phytocide. 
Interferes with
plant production of histidine; reagent in photography. 
Use on
food croplands has been cancelled by EPA. 
Currently used for
control of woody plants, annual grasses and broadlead weeds;
perennial broadleaf weeds and grasses; cattails; poison ivy;
and certain aquatic weeds in marshes and drainage ditches 
(Sax 1986).

Colourless crystals.

84.08

Translocation of amitrole through the soil occurs in sandy,
low humus soil in cool, damp weather (or when the groundwater
level is high). 
Mobility decreases with increasing clay and
humus content of the soil (Sax 1986).

When strongly heated emits highly toxic fumes.

Sublimes undecomposed under reduced pressure.

Soluble in water.

Photooxidation half-life in air:
3.2hr - 32hr,
scientific judgement based upon an estimated rate constant for 
vapor phase reaction with hydroxyl radicals in air
(Howard 1991).

Aerobic half-life:
4w - 6mo,
scientific judgement based upon reported half-lives in soil and 
water (Howard 1991).

Anaerobic half-life:
16w - 24mo,
scientific judgement based upon estimated aqueous aerobic 
biodegradation half-life (Howard 1991).

Persists in water more than 200 days. 
Acts as a weak base and
forms salts with acids (aqueous solutions are neutral) 
(Sax 1986).

Impact on biodegradation processes: approx. 50 % inhibition of
NH3 oxidation in Nitrosomonas at 70 mg/l 
(Hooper & Terry 1973).

Freshwater algae remove amitrole from water at pH 7.5 or above.

Uptake of amitrole by Scenedesmus quadricauda was directly
related to herbicide concentration and easily metabolized 
(Sax 1986).

In diet: rats fed 50 ppm for 68 weeks suffered no effect on
growth or food intake but the male rats developed an enlarged
thyroid after thirteen weeks ; rats fed 500 ppm for 17 weeks
and returned to normal diet 2 weeks before sacrifice appeared
to have normal thyroids (Verschueren 1983).

Carcinogenic (McCann et al. 1975).

Cancer-suspect agent (Verschueren 1983).

Amitrol induced thyroid and liver tumors in both mice and rats
following oral and/or subcutaneous administration. 
An increased
incidence of liver-cell tumours in the trout has also been
reported following oral administration, but this cannot be
conclusive. 
Limited skin-painting studies in mice gave no
evidence of skin carcinogenicity. 
A single, small, cohort study
raised the suspicion that amitrole may be carcinogenic to
man,but the findings cannot be regarded as conclusive
(Sax 1986).

Mutagenicity in the Salmonella test: none: < 0.001 revertant
colonies/nmol; < 70 revertant colonies at 5 mg/plate 
(McCann et al. 1975).

mutagen data:
nd, esc, 0.010 mmol/l;
ic, esc, 15 g/l;
tr, rat, emb, 80 mg/l;
ma, mus, sat, 12 mg/kg;
tr, ham, emb, 10 mg/l 
(Sax 1986).

0 to 40 mg injected into chick yolk sacs during 0 to 96 hours
incubation periods produced abnormalities of the beak and
occasionally bent tibias (Sax 1986).

Day old corn seedlings (Zea mays) treated with nutrient
solution which contained 80 mg/l of amitrole produced
chlorotic tissues (McWhorter 1963).

Incubation of segments of Sesbania exaltata hypocotyls in 1%
sucrose containing 2 ppm amitrole inhibited protein synthesis
by 19 % (Mann et al. 1965).

ATA caused inhibition of root elongation, when applied to the
mature leaves of rooted cuttings of Populus tremula in
quantities of > 0.1 mg per plant (in a lanolin paste containing
0.5 % ATA) or to the growth solution in concentrations from
0.00003 M. 
In both cases the response was delayed about 24
hours (Eliasson 1962).

Crustacean: no effect level: Gammarus fasciatus; 100 mg/l, 48 hr
            no effect level: Asellus brevicaudus; 100 mg/l, 48hr
            no effect level: Palaemonetes kadiakensis;100 mg/l;
            no effect level: Orconectes nais; 100 mg/l,48hr 48hr
Fish:       no effect level: Lepomis macrochirus: 100 mg/l,48hr
(Sanders 1970).