The WHO Guidelines to Classification of Pesticides by Hazard (Extremely Hazardous to Moderately Hazardous)

Adapted from WHO 1996.

Individual products are classified in a series of tables according to the products’ oral and dermal toxicity and physical states. Technical products classified as Class IA (extremely hazardous, Class IB (highly hazardous), Class II (moderately hazardous) and Class III (slightly hazardous) are listed in table 1, table 2, table 3 and table 4, respectively. Technical products unlikely to present any acute hazard in normal use are listed in table 5. The classification given in tables 1 to 5 is of technical compounds and only forms the starting point for the final classification of an actual formulation: the final classification of any product depends on its formulation. Classification of mixtures of pesticides is not included; many of these mixtures are marketed with varying concentrations of active constituents. (For information on how to find the hazard class of formulations and mixtures, see WHO 1996.) Technical products believed to be absolete or discontinued (see table 6) are not inclued in the Classification. Table 7 lists gaseous fumigants not included in the WHO Recommanded Classification of Pesticides by Hazard.C

On this page are the following tables. Please return to the Minerals and Agricultural Chemicals chapter page for the remaining tables.

Table 1. List of technical products classified in Class IA: "Extremely hazardous"

Table 2. List of technical products classified in Class IB: "Highly hazardous"

Table 3. List of technical products classified in Class II: "Moderately hazardous"

Table 1. List of technical products classified in Class IA: "Extremely hazardous"

Name

Status

Main use

Chemical type

Physical state

Route

LD50 (mg/kg)

Remarks

Acrolein

C

H

 

L

O

29

EHC 127; HSG 67

Alachlor

ISO

H

 

S

O

930

Adjusted classification; carcinogenic in rats and mice; DS 84

Aldicarb

ISO

I-S

C

S

O

0.93

DS 53; EHC 121; HSG 64

Arsenous oxide

C

R

 

S

O

180

Adjusted classification; minimum lethal dose 
for humans of 2 mg/kg; evidence of 
carcinogenicity for  humans is sufficient;
EHC 18; HSG 70

Brodifacoum

ISO

R

 

S

O

0.3

DS 57; EHC 175; HSG 93

Bromadialone

ISO

R

 

S

O

1.12

DS 88; EHC 175; HSG 94

Bromethalin

ISO

R

 

S

O

2

 

Calcium cyanide

C

FM

 

S

O

39

Adjusted classification; calcium cyanide is in Class IA as it 
reacts with moisture to produce hydrogen cyanide gas; 
the gas is not classified under the WHO system (see table 7)

Captafol

ISO

F

 

S

O

5,000

Adjusted classification; carcinogenic in rats and mice; 
HSG 49

Chlorfenvinphos

ISO

I

OP

L

O

10

 

Chlormephos

ISO

I

OP

L

O

7

 

Chlorophacinone

ISO

R

 

S

O

3.1

DS 62; EHC 175

Chlorthiophos

ISO

I

OP

L

O

9.1

 

Coumaphos

ISO

AC, MT

OP

L

O

7.1

 

CVP

N(J)

         

See chlorfenvinphos

Cycloheximide

ISO

F

 

S

O

2

 

DBCP

N(J)

         

See dibromochloropropane

Demephion-O and -S

ISO

I

OP

L

O

15

 

Demeton-O and -S

ISO

I

OP

L

O

2.5

DS 60

Dibromochloropropane

C

F-S

 

L

O

170

Adjusted classification; has been found to cause sterility in 
humans and is mutagenic and carcinogenic in animals

Difenacoum

ISO

R

 

S

O

1.8

EHC 175; HSG 95

Difethialone

ISO

R

 

S

O

0.56

EHC 175

Difolatan

N(J)

         

See captafol

Dimefox

ISO

I

OP

L

O

1

Volatile

Diphacinone

ISO

R

 

S

O

2.3

EHC 175

Disulfoton

ISO

I

OP

L

O

2.6

DS 68

EPN

N(A,J)

I

OP

S

O

14

Has been reported as causing delayed neurotoxicity in hens

Ethoprop

N(A)

         

See ethoprophos

Ethoprophos

ISO

I-S

OP

L

D

26

DS 70

Ethylthiometon

N(J)

         

See disulfoton

Fenamiphos

ISO

N

OP

L

O

15

DS 92

Fensulfothion

ISO

I

OP

L

O

3.5

DS 44

Flocoumafen

N(B)

R

 

S

O

0.25

EHC 175

Fonofos

ISO

I-S

OP

L

O

c8

 

Hexachlorobenzene

ISO

FST

 

S

D

10,000

Adjusted classification; has caused a serious outbreak of 
porphyria in humans; DS 26

Leptophos

ISO

I

OP

S

O

50

Adjusted classification; has been shown to cause delayed 
neurotoxicity; DS 38

M74

N(J)

         

See disulfoton

MBCP

N(J)

         

See leptophos

Mephosfolan

ISO

I

OP

L

O

9

 

Mercuric chloride

ISO

F-S

 

S

O

1

 

Merkaptophos

N(U)

         

When mixed with merkaptophosteolovy, 
see demeton -O and -S

Metaphos

N(U)

         

See parathion-methyl

Mevinphos

ISO

I

OP

L

D

4

DS 14

Nitrofen

ISO

H

 

S

O

c3,000

Adjusted classification; carcinogenic in rats and mice; 
teratogenic in several species tested; 
DS 84

Parathion

ISO

I

OP

L

O

13

DS 6; HSG 74

Parathion-methyl

ISO

I

OP

L

O

14

DS 7; EHC 145; HSG 75

Phenylmercury acetate

ISO

FST

 

S

O

24

Adjusted classification; highly toxic to mammals and very 
small doses have produced renal lesions; 
teratogenic in the rat

Phorate

ISO

I

OP

L

O

2

DS 75

Phosfolan

ISO

I

OP

L

O

9

 

Phosphamidon

ISO

I

OP

L

O

7

DS 74

Prothoate

ISO

AC,I

OP

L

O

8

 

Red squill

           

See scilliroside

Schradan

ISO

I

OP

L

O

9

 

Scilliroside

C

R

 

S

O

c0.5

Induces vomiting in mammals

Sodium fluoroacetate

C

R

 

S

O

0.2

DS 16

Sulfotep

ISO

I

OP

L

O

5

 

TEPP

ISO

AC

OP

L

O

1.1

 

Terbufos

ISO

I-S

OP

L

O

c2

 

Thiofos

N(U)

         

See parathion

Thionazin

ISO

N

OP

L

O

11

 

Timet

N(U)

         

See phorate

Source: WHO 1996.

Table 2. List of technical products classified in Class IB: "Highly hazardous"

Name

Status

Main use

Chemical
type

Physical
state

Route

LD50 (mg/kg)

Remarks

Aldoxycarb

ISO

I,N

C

S

O

27

 

Aldrin

ISO

I

OC

S

D

98

DS41; EHC 91; HSG 21

Allyl alcohol

C

H

 

L

O

64

Highly irritant to skin and eyes

Aminocarb

ISO

I

C

S

O

50

 

Antu

ISO

R

 

S

O

8

Induces vomiting in dogs. Some impurities are 
carcinogenic

Azinphos-ethyl

ISO

I

OP

S

O

12

DS 72

Azinphos-methyl

ISO

I

OP

S

O

16

DS 59

Benfuracarb

N(B)

I

C

L

O

138

 

Bis(tributyltin) oxide

C

F,M

 

L

O

194

Irritant to skin. DS 65; EHC 15

Blasticidin-S

N(J)

F

 

S

O

16

 

Bromophos-ethyl

ISO

I

OP

L

O

71

 

Butocarboxim

ISO

I

C

L

O

158

 

Butoxycarboxim

ISO

I

C

L

D

288

 

Cadusafos

ISO

N,I

OP

L

O

37

 

Calcium arsenate

C

I

 

S

O

20

 

Carbofuran

ISO

I

C

S

O

8

DS 56

Carbophenothion

ISO

I

OP

L

O

32

 

3-chloro-1,2-propanediol

C

R

 

L

O

112

In non-lethal dosage is a sterilant for male rats

Coumachlor

ISO

R

 

S

D

33

 

Coumatetralyl

ISO

R

 

S

O

16

 

Crotoxyphos

ISO

I

OP

L

O

74

 

zeta-Cypermethrin

ISO

I

PY

L

O

c86

 

DDVF

N(U)

         

See dichlorvos

DDVP

N(J)

         

See dichlorvos

Delnav

N(U)

         

See dioxathion

Demeton-S-methyl

ISO

I

OP

L

O

40

DS 61

Demeton-S-methylsulphon

ISO

I

OP

S

O

37

 

Dichlorvos

ISO

I

OP

L

O

56

Volatile, DS 2; EHC 79; HSG 18

Dicrotophos

ISO

I

OP

L

O

22

 

Dieldrin

ISO

I

OC

S

O

37

DS 17: EHC 91

Dimetilan

N(A,B)

I

C

S

O

47

 

Dinoseb

ISO

H

CNP

L

O

58

 

Dinoseb acetate

ISO

H

CNP

L

O

60

 

Dinoterb

ISO

H

CNP

S

O

25

 

Dioxathion

ISO

I

OP

L

O

23

 

DMTP

N(J)

         

See methidathion

DNBP

N(J)

         

See dinoseb

DNBPA

N(J)

         

See dinoseb acetate

DNOC

ISO

I-S,H

CNP

S

O

25

 

EDDP

N(J)

         

See edifenfos

Edifenphos

ISO

F

OP

L

O

150

 

Endrin

ISO

I

OC

S

O

7

DS 1; EHC 130; HSG 60

ESP

N(J)

I

OP

L

O

105

 

Famphur

N(A)

I

OP

S

O

48

 

Flucythrinate

ISO

I

PY

L

O

c67

Irritant to skin and eyes

Fluoroacetamide

C

R

 

S

O

13

 

Formetanate

ISO

AC

C

S

O

21

 

Fosmethilan

ISO

I

OP

S

O

49

Irritant to skin and eyes.

Furathiocarb

N(B)

I-S

C

L

O

42

 

Heptenophos

ISO

I

OP

L

O

96

 

Isazofos

ISO

I-S

OP

L

O

60

 

Isofenphos

ISO

I

OP

oil

O

28

 

Isothioate

ISO

I

OP

L

O

150

 

Isoxathion

ISO

I

OP

L

O

112

 

Lead arsenate

C

L

 

S

O

c10

 

Mecarbam

ISO

I

C

oil

O

36

 

Mercuric oxide

ISO

O

 

S

O

18

 

Methamidophos

ISO

I

OP

L

O

30

HSG 79

Methidathion

ISO

I

OP

L

O

25

 

Methomyl

ISO

I

C

S

O

17

DS 55, EHC 178; HSG 97

Methyl-merkapto-phosteolovy

N(U)

         

See demeton-S-methyl

Metilmerkapto-phosoksid

N(U)

         

See oxydemeton-methyl

Metriltriazotion

N(U)

         

See azinphos-methyl

Monocrotophos

ISO

I

OP

S

O

14

HSG 80

MPP

N(J)

         

See fenthion

Nicotine

ISO

   

L

D

50

 

Omethoate

ISO

I

OP

L

O

50

 

Oxamyl

ISO

I

C

S

O

6

DS 54

Oxydemeton-methyl

ISO

I

OP

L

O

65

 

Oxydeprofos

N(B)

         

See ESP

Paris green

C

L

 

S

O

22

Copper-arsenic complex

Pentachlorophenol

ISO

I,F,H

CNP

S

D

80

Irritant to skin; EHC 71; HSG 19

Phenylmercury nitrate

C

FST

OM

S

   

Oral LD50 not available, rat i.v. LD50 is 27 mg/kg

Pirimiphos-ethyl

ISO

I

OP

L

O

140

 

Propaphos

N(J)

I

OP

L

O

70

 

Propetamphos

ISO

I

OP

L

O

106

 

Sodium arsenite

C

R

 

S

O

10

 

Sodium cyanide

C

R

 

S

O

6

 

Strychnine

C

R

 

S

O

16

 

TBTO

           

See bis-(tributyltin) oxide

Tefluthrin

N(B)

I-S

PY

S

O

c22

 

Thallium sulfate

C

R

 

S

O

11

DS 10

Thiofanox

ISO

I-S

C

S

O

8

 

Thiometon

ISO

I

OP

oil

O

120

DS 67

Thioxamyl

           

See oxyamyl

Triamiphos

ISO

F

 

S

O

20

 

Triazophos

ISO

I

OP

L

O

82

 

Triazotion

N(U)

         

See azinphos-ethyl

Vamidothion

ISO

I

OP

L

O

103

 

Warfarin

ISO

R

 

S

O

10

DS 35, EHC 175; HSG 96

Zinc phosphide

C

R

 

S

O

45

DS 24, EHC 73

Source WHO 1996.

Table 3. List of technical products classified in Class II: "Moderately hazardous"

Name

Status

Main Use

Chemical type

Physical state

Route

LD50 (mg/kg)

Remarks

Alanycarb

ISO

I

C

S

O

330

 

Allidochlor

ISO

H

 

L

O

700

Irritant to skin and eyes

Anilofos

ISO

H

 

S

O

472

 

Azaconazole

N(B)

F

 

S

O

308

 

Azocyclotin

ISO

AC

OT

S

O

80

 

Bendiocarb

ISO

I

C

S

O

55

DS 52

Bensulide

ISO

H

 

L

O

270

 

Benzofos

N(U)

         

See phosalone

BHC

ISO

         

See HCH

gamma-BHC

           

See gamma-HCH

Bifenthrin

N(B)

I

PY

S

O

c55

 

Bilanafos

ISO

H

 

S

O

268

 

Binapacryl

ISO

AC

 

S

O

421

 

Bioallethrin

C

I

PY

L

O

c700

Bioallethrin, esbiothrin, esbiol and esdepalléthrine are 
members of the allethrin series; their toxicity varies 
considerably within this series according to 
concentrations of isomers.

Bisthiosemi

N(J)

R

 

S

O

c150

Induces vomiting in non-rodents

BPMC

           

See fenobucarb

Bromoxynil

ISO

H

 

S

O

190

 

Bronopol

N(B)

B

 

S

O

254

 

Bufencarb

ISO

I

C

S

O

87

 

Butamifos

ISO

H

 

L

O

630

 

Butenachlor

ISO

H

 

L

O

1,630

 

Butylamine

ISO

F

 

L

O

380

Irritant to skin

Camphechlor

ISO

I

OC

S

O

80

DS 20; EHC 45

Carbaryl

ISO

I

C

S

O

c300

DS 3; EHC 153; HSG 78

Carbosulfan

ISO

I

 

L

O

250

 

Cartap

ISO

I

 

S

O

325

 

Chloralose

C

R

 

S

O

400

 

Chlordane

ISO

I

OC

L

O

460

DS 36; EHC 34; HSG 13

Chlordimeform

ISO

AC

OC

S

O

340

 

Chlorphenamidine

N(J)

         

See chlordimeform

Chlorphonium

ISO

PGR

 

S

O

178

Irritant to skin and eyes

Chlorpyrifos

ISO

I

OP

S

O

135

DS 18

Clomazone

ISO

H

 

L

O

1,369

 

Copper sulfate

C

F

 

S

O

300

 

Cuprous oxide

C

F

 

S

O

470

 

Cyanazine

ISO

H

T

S

O

288

 

Cyanofenphos

ISO

I

OP

S

O

89

Has been reported as causing delayed neurotoxicity 
in hens; no longer manufactured

Cyanophos

ISO

I

OP

L

O

610

 

CYAP

N(J)

         

See cyanophos

Cyfluthrin

ISO

I

PY

S

O

c250

 

beta-Cyfluthrin

ISO

I

PY

S

O

450

 

Cyhalothrin

ISO

Ix

PY

oil

O

c144

EHC 99

lambda-Cyhalothrin

N(B)

I

PY

S

O

c56

EHC 142; HSG 38

CYP

N(J)

         

See cyanofenphos

Cypermethrin

ISO

I

PY

S

O

c250

DS 58; EHC 82; HSG 22

alpha-Cypermethrin

ISO

I

PY

S

O

c79

EHC 142

beta-Cypermethrin

ISO

I

PY

S

O

166

 

Cyphenothrin ((1R)-isomers)

ISO

I

PY

L

O

318

 

Cyprofuram

ISO

F

 

S

O

174

 

2,4-D

ISO

H

PA

S

O

375

DS 37; EHC 29; EHC 84

DAPA

N(J)

         

See fenaminosulf

DDT

ISO

I

OC

S

O

113

DS 21; EHC 9; EHC 83

Deltamethrin

ISO

I

PY

S

O

c135

DS 50; EHC 97; HSG 30

Dialifor

N(A,J)

         

See dialifos

Dialifos

ISO

I

OP

S

D

145

 

Di-allate

ISO

H

TC

L

O

395

 

Diazinon

ISO

I

OP

L

O

300

DS 45

Dibrom

N (Denmark)

         

See naled

Dichlofenthion

ISO

I-S

OP

L

O

270

 

Difenzoquat

ISO

H

 

S

O

470

 

Dimethoate

ISO

I

OP

S

O

c150

DS 42; EHC 90; HSG 20

Dinobuton

ISO

AC,F

 

S

O

140

 

Dioxabenzophos

N(B)

I

OP

S

O

125

 

Dioxacarb

ISO

I

C

S

O

90

 

Diquat

ISO

H

P

S

O

231

Irritant to skin, and eyes, and damages nails;
DS 40; EHC 39; HSG 52

Drazoxolon

(ISO)

FST

 

S

O

126

 

ECP

N(J)

         

See dichlofenthion

Endosulfan

ISO

I

OC

S

O

80

DS 15; EHC 40; HSG 17

Endothal-sodium

(ISO)

H

 

S

O

51

 

EPBP

N(J)

I-S

OP

oil

O

275

 

EPTC

ISO

H

TC

L

O

1,652

 

Esbiol

           

See bioallethrin

Esbiothrin

           

See bioallethrin

Esdepalléthrine

           

See bioallethrin

Esfenvalerate

ISO

I

PY

S

O

87

 

Ethiofencarb

ISO

I

C

L

O

411

 

Ethion

ISO

I

OP

L

O

208

 

Etrimfos

ISO

I

OP

L

O

1,800

 

Fenaminosulf

ISO

F-S

 

S

O

60

 

Fenazaquin

ISO

AC

 

S

O

134

 

Fenchlorphos

ISO

I

OP

L

O

1,740

DS 69

Fenitrothion

ISO

I

OP

L

O

503

DS 30; EHC 133; HSG 65

Fenobucarb

N(B)

I

C

S

O

620

 

Fenpropathrin

ISO

I

PY

S

O

c66

 

Fenthion

ISO

I,L

OP

L

D

586

DS 23

Fentin acetate

(ISO)

F

OT

S

O

125

DS 22

Fentin hydroxide

(ISO)

F

OT

S

O

108

DS 22

Fenvalerate

ISO

I

PY

L

O

c450

EHC 95, DS 90; HSG 34

Fipronil

N(B)

I

Pyrazole

S

O

92

 

Fluvalinate

N(B)

I

 

oil

O

282

Irritant to skin

Fluxofenim

ISO

H

 

oil

O

670

 

Formothion

ISO

I

OP

L

O

365

 

Fosfamid

N(U)

         

See dimethoate

Furconazole-cis

ISO

F

 

S

O

450

 

Guazatine

N(B)

FST

 

S

O

230

LD50 value refers to triacetate

Haloxyfop

N(A,B)

H

 

S

O

393

 

HCH

ISO

I

OC

S

O

100

The LD50 varies according to the mixture of isomers. 
The value shown has been chosen, and the technical 
product placed in Class II, as a result of the cumulative 
properties of the beta isomer

Gamma-HCH

ISO

I

OC

S

O

88

DS 12; EHC 124; HSG 54

Heptachlor

ISO

I

OC

S

O

100

DS 19; EHC 38; HSG 14

Imazalil

ISO

F