ATRAZINE

Common name:    Atrazine

Other name:   atrazine (BSI, E-ISO, (f) F-ISO, ANSI, WSSA, JMAF)

Iupac name:   6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine

Chemical abstracts name:    6-chloro-N-ethyl-N`-(1-methylethyl)-l,3,5-triazine-2,4 -diamine

Type:Herbicide

CAS RN:[1912 24 9]

 

M.F.:C₈H₁₄ClN₅

Mol Wt:   215.7

 

Form (appearance):Composition: Tech. is ≥96% pure.

Colourless powder.

M.P.:175.8℃

B.P.:205.0℃/101 kPa

V.P.:3.85 x l0 2 mpa (25℃) (OECD 104)

S.G.:1.23 (22℃)

Solubility.:In water 33 mg/I (pH 7, 22℃). In ethyl acetate 24, acetone 31,

dichloromethane 28, ethanol 15, toluene 4.0, n hexane 0.11, n-octanol 8.7 (all in g/l,

25 ℃).

Stability:Relatively stable in neutral, weakly acidic and weakly alkaline media.

Rapidly hydrolysed to the hydroxy derivative in strong acids and alkalis, and at 70℃

in neutral media; DT50 (pH 1) 9.5, (pH 5) 86, (pH 13) 5.0d.

Henry:1.5× 10-4 Pa m3 mol-1 (calc.)

KowlogP:2.5 (25℃)

Pka:l.7, v. weakbase

 

Formulation types:FW; GR; SC; WG; WP.

Biochemistry:Photosynthetic electron transport inhibitor at the photosystem II

receptor site. Maize tolerance is attributed to rapid detoxification by glutathione

transferases.

Mode of action:  Selective systemic herbicide, absorbed principally through the roots,

but also through the foliage, with translocation acropetally in the xylem and

accumulation in the apical meristems and leaves.

Uses:Pre- and post-emergence control of annual broad leaved weeds and annual

grasses in maize, sorghum sugar cane, pineapples, chemical tallow_grassland,

macadgmla nuts, conifers, industrial weed control. In Europe, use is concentrated in

maize and sorghum. Used also in combinations with many other herbicides.

Phytotoxicity Phytotoxic to many crops, including most vegetables, potatoes, soya

beans, and peanuts.

 

Reviews: /IARC ref. 53; class 3

Oral:Acute oral LD50 for rats 1869-3090 mg tech./kg, mice >1332-3992 mg/kg.

Skin and eye: Acute percutaneous LD50 for rats >3100 mg/kg. Mild skin irritant; non-irritating to eyes (rabbits). Skin sensitiser in guinea pigs, but not in humans.

Inhalation:LC₅₀ (4 h) for rats >5.8 mg/l air.

Noel:(2 y) for rats 10 mg/kg diet (0.5 mg/kg daily), for dogs 150 mg/kg diet (3.75 mg/kg daily), for mice 10 mg/kg diet (1.4 mg/kg daily).

ADI: 0.005 mg/kg b.w.

Water GV 2 μg/l (TDI 0.5 μg/kg b.w.)

Toxicity:  WHO (a.i.) III (Table 5); EPA (formulation) III

EC hazard:(Xn; R48/221 R431 N; R50 R53)

 

Birds:Acute oral LD₅₀ varies from 940 mg/kg for bobwhite quail to >2000 mg/kg for

mallard ducks and 4237 mg/kg for adult Japanese quail. Eight-day dietary LC₅₀for

Japanese quail (chicks) >5000, (adults) >1000 mg/kg.

Fish:LC₅₀ (96 h) for rainbow trout 4.5-11.0, bluegill sunfish 16, carp 76, catfish 7.6, guppies 4.3 mg/I. Daphnia LCso (24 h) 87 mg/l.

Algae:EC₅₀ (72 h) for Scenedesmus subspicatus 0.043 mg/l, (96 h) for Selenastrum capricornutum 0.13 mg/l.

Worms:  LC₅₀ (14 d) for Eisenia foetida 78 mg/kg soil.

/ Bees: LD₅₀ (oral) >97 μg/bee; (contact) >100 μg/bee.

 

Plant:In tolerant plants, atrazine is readily metabolised to hydroxyatrazine and amino

acid conjugates, with further decomposition of hydroxyatrazine by degradation of the

side-chains and hydrolysis of the resulting amino acids on the ring, together with

evolution of CO2. In sensitive plants, unaltered atrazine accumulates, leading to

chlorosis and death.

Animals:   In mammals, following oral administration, atrazine is rapidly and

completely metabolised, primarily by oxidative dealkylation of the amino groups (R.

Ikonen et al., Toxicol. Lett., 1988, 44, 109; Bull. Environ. Contain. Toxicol., 1989, 43,

199; Y. Deng et al.,J. Agric. Food Chem., 1990, 38, 1411), and by reaction of the

chlorine atom with endogenous thiols. Diaminochlorotriazine is the main primary

metabolite, which readily conjugates with glutathione. More than 50% of the dose is

eliminated in the urine and around 33% in the faeces within 24 h.

Soil/Environment:Major metabolites under all conditions are desethylatrazine and

hydroxyatrazine. Field DT50 16-77 d (median 41 d), the longer values being from

cold or dry conditions. In natural waters, DT50 10-105 d (mean 55 d). DT50 under

groundwater conditions 105->200 d, depending on test system (M. J. Wood et al. in: A

Walker (Ed.), Pesticides in soils and water: current perspectives (BCPC Monograph

1991, 47, 175-182)). Kd 0.2-18 mi/g, Koc 39-173 mi/g; desalkylated metabolites had

alues similar to those of atrazine, while hydroxyatrazine was much more strongly

adsorbed.