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WORLD HEALTH ORGANIZATION

WHO/PCS/DS/96.86

ORGANISATION MONDIALE DE LA SANTE

Original: ENGLISH

FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS

Distr.: LIMITED

ORGANISATION DES NATIONS UNIES POUR L’ALIMENTATION ET L’AGRICULTURE

Date of issue: July 1996

WHO/FAO DATA SHEETS ON PESTICIDES

No. 86

ALACHLOR

1.0 GENERAL INFORMATION
1.1 Common Name:
1.1.1 Identity:
1.2 Synopsis:
1.3 Selected Properties
1.4 Agriculture, Horticulture And Forestry
1.4.1 Common formulations:
1.4.2 Susceptible pests:
1.4.3 Use pattern:
1.4.4 Unintended effects:
1.5 Public Health Programmes:
1.6 Household Use:
2.0 TOXICOLOGY AND RISKS
2.1 Toxicology - Mammals
2.1.1 Absorption route:
2.1.2 Mode of action:
2.1.3 Excretion products:
2.1.4 Toxicity, single dose:
2.1.5 Toxicity, repeated dose:
2.1.6 Dietary studies:
2.1.7 Carcinogenicity:
2.1.10 Reproduction:
2.1.11 Other:
2.2 Toxicology - Man
2.2.1 Absorption:
2.2.2 Dangerous doses:
2.2.3 Observations on occupationally exposed workers:
2.2.4 Observations on exposure of the general population:
2.2.5 Observations on volunteers:
2.2.6 Reported mishaps:
2.3 Toxicity - Non-Mammalian Species
2.3.1 Fish:
2.3.2 Birds:
3.0 FOR REGULATORY AUTHORITIES -
RECOMMENDATIONS OF COMPOUND
3.1 Recommended Restrictions On Availability
3.2 Transportation And Storage
3.3 Handling
3.4 Disposal And/Or Decontamination Of Containers
3.5 Selection, Training And Medical Supervision Of Workers
3.6 Additional Regulations Recommended If Distributed By Aircraft
3.7 Labelling
3.8 Residues In Food And Water
4.0 PREVENTION OF POISONING IN MAN
AND EMERGENCY AID
4.1 Precautions In Use
4.1.1 General:
4.1.2 Manufacture and formulation - TLV:
4.1.3 Mixers and applicators:
4.1.4 Other associated workers:
4.1.5 Other populations likely to be affected:
4.2 Entry Of Persons Into Treated Areas
4.3 Decontamination Of Spillage And Containers
4.4 Emergency Aid
4.4.1 Early symptoms of poisoning:
4.4.2 Treatment before person is seen by physician if symptoms appear following exposure:
5.0 FOR MEDICAL AND LABORATORY PERSONNEL
5.1 Medical Diagnosis And Treatment In Cases Of Poisoning
5.1.1 General information:
5.1.2 Symptoms and signs:
5.1.3 Laboratory:
5.1.4 Treatment:
5.1.5 Prognosis:
5.1.6 References to previously reported cases:
5.2 Surveillance Tests:
5.3 Laboratory Methods
5.3.1 Detection and Assay of Compound:
5.3.2 Other Tests in Case of Poisoning:

It must be noted that the issue of a Data Sheet for a particular pesticide does not imply endorsement of the pesticide by WHO or FAO for any particular use, or exclude its use for other purposes not stated. While the information provided is believed to be accurate according to data available at the time when the sheet was compiled, neither WHO nor FAO are responsible for any errors or omissions, or any consequences therefrom.

The issue of this document does not constitute formal publication. It should not be reviewed, abstracted or quoted without the agreement of the Food and Agriculture Organization of the United Nations or of the World Health Organization.

Ce document ne constitue pas une publication. Il ne doit faire l’objet d’aucun compte rendu ou résumé ni d’aucune citation sans l’autorisation de l’Organisation des Nations Unies pour l’Alimentation et l’Agriculture ou de l’Organisation Mondiale de la Santé.

CLASSIFICATION:

Primary use:

Herbicide

Secondary use:

 

Chemical group:

Acetanilide

1.0 GENERAL INFORMATION

1.1 Common Name:

alachlor (BSI, (BSI, E-ISO, ANSI, WSSA, JMAF) alachlore (F-ISO).

1.1.1 Identity:

IUPAC name:

2-chloro-2’,6’-diethyl-N-methoxymethylacetanilide

CA name:

2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide.

CAS registry name:

15972-60-8

RTECS number:

AE1225000

Molecular formula:

C14H20Cl NO.3.22

Relative molecular mass:

269.8

Structural Formula:

Structural Formula

Trade names: AlanexR; LassoR; LazoR; MicrotechR; PillarzoR.

1.2 Synopsis:

Alachlor is an acetanilide herbicide of low acute toxicity, but repeated exposure has been reported to cause hepatotoxicity, irreversible uveal degeneration and tumour formation in rats. Low to moderate leaching potential in soil and good translocation in plants demand careful adherence to good agricultural practices to avoid potential contamination of food and water resources.

1.3 Selected Properties

Physical characteristics: Alachlor is a white or cream, combustible crystalline solid without odour. The melting point is 39.5 - 41.5 ºC. Corrosive to steel and black iron but not stainless steel or aluminium.

Solubility: Soluble in acetone, benzene, chloroform, ethanol, ether and ethyl acetate. Sparingly soluble in heptane. Solubility in water is 242 mg/litre at 25 ºC.

Stability: Hydrolysed by strong acids and alkali. Decomposes at 105 ºC. Stable to ultra violet radiation.

Vapour pressure: 2.9 mPa at 25 ºC.

1.4 Agriculture, Horticulture And Forestry

1.4.1 Common formulations:

Emulsifiable concentrates, granules, wettable powders and micro encapsulated. In formulations with glyphosate or atrazine.

1.4.2 Susceptible pests:

Selective pre-emergence and post-emergence herbicide effective in the control of most grasses, most annuals and some broad leaved plants in corn, soybean and other crops.

1.4.3 Use pattern:

Used on soybean, brassica, maize, sugar-cane and cotton crops as a pre-planting application or as a post-emergence at the 1-2 leaf stage. Requires moisture for activation. Emulsifiable concentrates are frequently tank-mixed with other herbicides and fertilizers.

1.4.4 Unintended effects:

Phytotoxic to sugar beet and cucurbits.

1.5 Public Health Programmes:

No recommended usage reported.

1.6 Household Use:

No recommended usage reported.

2.0 TOXICOLOGY AND RISKS

2.1 Toxicology - Mammals

2.1.1 Absorption route:

Alachlor is readily absorbed from the gastrointestinal tract and, to a lesser extent from the skin. No published data are available on the extent of absorption following inhalation exposure.

2.1.2 Mode of action:

No published information available.

2.1.3 Excretion products:

Metabolism of alachlor in the rat is fairly rapid and complex because of extensive enterohepatic recirculation. Excretion is primarily as mercapturic acid, glucuronide and sulphate conjugates in the urine and faeces. Approximately 89% of an oral dose is recovered in the urine and faeces within 10 days. However, a significant portion is eliminated in 48 hours. Elimination is characterized in 2 phases: a rapid phase with a half-life of 0.2 to 10 hours, a slow phase with a half-life of 5-16 days. Urinary excretion accounted for some 50% of the total and elimination as CO2 is minimal.

In contrast, metabolism in the monkey is less complex; more than 90% of an intravenous dose is recovered in the excreta within two days. Approximately 90% of the total is recovered in the urine.

2.1.4 Toxicity, single dose:

Oral LD50

 

Rat

930 - 1360 mg (technical)/kg b.w.

Dermal LD50

 

Rabbit

13,300 mg (technical)/kg b.w.

In rats exposed to lethal amounts of alachlor, death was preceded by weakness, salivation, tremors, collapse and coma.

Primary irritation: A slight irritant effect on rabbit skin and eyes was observed following acute exposure. Alachlor was a skin sensitizer in repeated exposures (see Section 2.1.5).

2.1.5 Toxicity, repeated dose:

Dermal: A strong dermal sensitization was seen in guinea-pigs challenged with a dermal dose two weeks after four dermal applications of alachlor.

Accumulation of compound: Pharmacokinetic and metabolism studies indicate that alachlor does not bioaccumulate following repeated administrations.

2.1.6 Dietary studies:

Short-term: Ninety-day administration of 200 mg/kg diet had no adverse effect on rats or dogs. At 2000 mg/kg diet some reduction in the growth rate was observed. In dogs dietary exposure to doses of 5-75 mg/kg b.w./day for six months induced hepatic fatty degeneration and biliary hyperplasia in both sexes at doses  25 mg/kg b.w./day. An increase in absolute and relative liver weights was observed  5 mg/kg b.w./day in male dogs and  25 mg/kg b.w./day in females.

Long-term: A two year feeding study at levels equivalent to 14-126 mg/kg b.w./day produced toxicity in Long Evans rats at all dose levels. The major lesions were uveal degeneration and hepatotoxicity. Examination of a satellite 126 mg/kg b.w./day dose group, following exposure for less than a life-time demonstrated that the ocular condition, once established, was irreversible. In a second two year dietary study in rats a no-effect level for uveal degeneration was established as 2.5 mg/kg b.w./day for rats.

In a one-year study in dogs by the oral route a no-effect-level of 1 mg/kg b.w. was established.

2.1.7 Carcinogenicity:

In an 18 month feeding study with technical alachlor (26, 78 and 260 mg/kg b.w./day) an increased incidence of bronchio-alveolar tumours was observed in female CD-1 mice at 260 mg/kg b.w./day (the highest dose tested). No significant increase in tumour incidence was reported in male mice or in females at lower doses. The incidence of these tumours in the control group (female) was unusually low in comparison to historical control values and therefore, the lung adenomas were not considered to be treatment related.

Two chronic feeding studies were conducted with alachlor in Long-Evans rats. The feeding levels used in the first study were eqivalent to 14, 42 and 126 mg/kg b.w./day for 2 years. A dose-related increase was observed for nasal turbinate adenomas in both sexes. A significant increase in the incidence of malignant stomach tumors was also observed in both sexes at the highest feeding concentration. In addition, follicular cell tumours were increased in the thyroid of the male rats exposed to the highest dietary concentration. In the second study a complex dosing regimen was introduced: 126 mg/kg b.w./day for 5 to 6 months for some of the animals, the others remaining exposed for 2 years. In a second phase of the study, groups of rats received diets containing equivalents of 0.5, 2.5 and 15 mg/kg b.w./day for 2 years.

The incidence of nasal turbinate adenomas was significantly elevated at 126 mg/kg b.w./day in both sexes. Malignant stomach tumours were also noted in females at this dose level. In addition, the follicular tumours of the thyroid were even more pronounced than in the first study.

Teratogenicity: No teratogenic effect was observed following gavage administration of up to 400 mg/kg b.w./day to rats. A no effect level of 150 mg/kg b.w./day was established for maternal and foetotoxicity.

Mutagenicity: Chromatid-type aberrations were observed in the bone-marrow of Wistar rats following a single intraperitoneal injection of 2.5 mg/kg b.w. of alachlor of an unspecified source. In a similar study, using technical alachlor, chromatid aberrations were not observed in rats at doses up to 1000 mg/kg b.w. No clastogenic effect was observed in Wistar rats following 280 days administration of 200 mg/kg diet.

Cultured human lymphocytes showed a dose-dependent increase in aberrations following in vitro incubation at concentrations of 2-40 mg/litre. Alachlor was not mutagenic with or without metabolic activation in Escherichia coli, or in several strains of Salmonella typhimurium. Commercial grade alachlor was mutagenic without metabolic activation in Saccharomyces cerevisae D4; technical alachlor only showed mutagenic activity in this strain following metabolic activation by Zea mays extract.

2.1.10 Reproduction:

A three generation reproduction study in rats gave a no-effect level of 10 mg/kg b.w./day. A dose of 30 mg/kg b.w./day caused renal toxicity in the adult F2 males and the F3 pups. The condition was characterized by discolouration of the kidneys, chronic nephritis and increased absolute and relative kidney weights.

2.1.11 Other:

Following administration of 14C-labelled alachlor to rats, radioactivity was observed in those organs with high blood perfusion and also in the eyes, brain, stomach and ovaries.

2.2 Toxicology - Man

2.2.1 Absorption:

Alachlor has the potential to be absorbed from the gastrointestinal tract and from intact skin. There are no published data available on the extent of absorption following inhalation exposure in man or animals.

2.2.2 Dangerous doses:

No published information available.

2.2.3 Observations on occupationally exposed workers:

No published information available.

2.2.4 Observations on exposure of the general population:

No published information available. If not used according to manufacturers’ recommendations, the relative stability of alachlor could lead to contamination of foodstuffs, ground and surface waters.

2.2.5 Observations on volunteers:

Patch-tests with LassoR revealed that 5/21 volunteers showed a sensitization reaction to alachlor. All volunteers were agricultural workers, although three of the five sensitized subjects had no history of direct exposure to alachlor.

2.2.6 Reported mishaps:

No published information available.

2.3 Toxicity - Non-Mammalian Species

2.3.1 Fish:

aquatic organisms

 

 

LC50 96 hour

Bluegill sunfish

2.8 mg/litre (technical)

 

Fathead minnow

5.0 mg/litre (technical)

 

Rainbow trout

1.8 mg/litre (technical)

EC50 (48h)

Daphnia magna

10 mg/litre (technical)

2.3.2 Birds:

Acute LD50

Bobwhite quail

1536 mg/kg

LC50 (5 day)

Mallard duck

5000 mg/kg diet

 

Bobwhite quail

5000 mg/kg diet

3.0 FOR REGULATORY AUTHORITIES -
RECOMMENDATIONS OF COMPOUND

3.1 Recommended Restrictions On Availability

The product labels should include: handling instructions to reduce applicator exposure; prohibition of use on potato crops; prohibition of aerial application; inclusion of a tumour warning on the label; a warning against water contamination and a statement on use of protective clothing.

US EPA classification: B2 carcinogen (probable human carcinogen). Not evaluated by IARC and JMPR.

All formulations - Category 1

[For definition of categories see the 'Introduction to Data Sheets']

3.2 Transportation And Storage

All formulations: Should be transported and stored in clearly labelled, rigid, leakproof containers away from food or drink. Storage should be under lock and key, secure from access by children and other unauthorized persons. Combustible; do not store near heat or flame.

3.3 Handling

All formulations: Protective clothing should be used at all times (see Section 4.1.3). Adequate washing facilities should be available close at hand. Eating, drinking and smoking should be prohibited during handling and before washing after handling.

3.4 Disposal And/Or Decontamination Of Containers

Decontamination of containers should not be permitted. Container must be either burned or crushed and buried below the topsoil. Keep clear of smoke when container is burned. Extreme care must be taken to avoid subsequent contamination of water sources when burying container and/or residues.

3.5 Selection, Training And Medical Supervision Of Workers

All formulations: Pre-employment medical examination of workers is desirable. Workers suffering from active hepatic or renal disease should be excluded from contact. Training of workers to avoid contact is essential. Account should be taken of the workers’ ability to comprehend and follow instructions. Persons with a history of sensitization to acetanilide compounds should be excluded from contact.

3.6 Additional Regulations Recommended If Distributed By Aircraft

Application by air is not recommended. US EPA (1984) recommends prohibition of aerial application.

3.7 Labelling

All formulations - Minimum cautionary statement:

Alachlor is an acetanilide herbicide. It is poisonous if swallowed and is a possible human carcinogen. Avoid all contact with skin and eyes, sensitization may occur with repeated contact. Clean protective clothing, including gloves, and face mask must be worn when handling alachlor. Keep out of reach of children and well away from foodstuffs. Extreme care must be taken to avoid contamination of all water sources.

3.8 Residues In Food And Water

Maximum residue levels have not yet been considered by the Joint FAO/WHO Meeting on Pesticide Residues. Maximum residue limits have been recommended in several countries.

WHO Guidelines for Drinking Water Quality propose the guideline value for alachlor of 20 μg/litre, for the excess risk of 1/100 000.

4.0 PREVENTION OF POISONING IN MAN
AND EMERGENCY AID

4.1 Precautions In Use

4.1.1 General:

Alachlor is an acetanilide herbicide of low acute toxicity but is considered a possible human carcinogen. It has the potential to be absorbed from the gastrointestinal tract and across intact skin. It is important that contamination be washed from the skin as alachlor is a sensitizer following repeated dermal exposure.

4.1.2 Manufacture and formulation - TLV:

No published information available. Adequate ventilation must be provided to reduce the extent of dermal and inhalation exposures. Adequate protective clothing must also be worn (Section 4.1.3).

4.1.3 Mixers and applicators:

When opening the container and when mixing, care should be taken to avoid contact with eyes, skin and mouth. A clean protective suit should be worn, along with gloves, goggles and a face mask. Wash all the clothing, including the insides of gloves, before re-use. Mixing, if not mechanical, should always be carried out with a paddle of appropriate length. Splashes should be washed immediately from the skin or eyes with copious amounts of water. Before eating, drinking or smoking, hands and exposed skin should be thoroughly washed.

4.1.4 Other associated workers:

Persons associated with alachlor application should observe the precautions listed above under "Mixers and Applicators".

4.1.5 Other populations likely to be affected:

With good agricultural practice, other populations should not be exposed to hazardous amounts of alachlor.

4.2 Entry Of Persons Into Treated Areas

The general population should be kept out of treated areas until the application has dried.

4.3 Decontamination Of Spillage And Containers

Residues in containers should be emptied in a diluted form into a deep pit. Extreme care should be taken to avoid contamination of water resources. Decontamination of containers in order to use them for other purposes should not be permitted. Spillage of liquid formulations should be contained with absorbent material, which should be burned or buried in a deep pit. Remaining residues should be removed by thorough washing with detergent and water, ensuring that the run-off does not contaminate water resources.

4.4 Emergency Aid

4.4.1 Early symptoms of poisoning:

No reported cases. Symptoms would probably include headache, nausea, vomiting, and dizziness. Severe poisoning may induce convulsions and coma. Dermal irritation and allergic reactions have been reported.

4.4.2 Treatment before person is seen by physician if symptoms appear following exposure:

The person should stop work immediately, remove contaminated clothing and wash the affected skin with water (and soap if available) and flush the area with large volumes of water. If the eyes are affected they should be thoroughly washed with large volumes of clean water. Vomiting should not be induced following ingestion of emulsifiable concentrate formulations, but may be induced in a fully conscious person, if granule formulations have been ingested. In the event of collapse, artificial respiration should be given.

5.0 FOR MEDICAL AND LABORATORY PERSONNEL

5.1 Medical Diagnosis And Treatment In Cases Of Poisoning

5.1.1 General information:

Alachlor is an acetanilide herbicide of low acute toxicity. Absorption from the gastrointestinal tract and across the intact skin are the likely routes of exposure. No published information is available on the extent of absorption following inhalation exposure in man or animals. Dermal contact may elicit an allergic response in susceptible individuals. The description of dermal sensitization is given by Iden, D.L. and Schroeter, A.L. (1977) Arch. Dermatol., 113.

5.1.2 Symptoms and signs:

No reported cases but symptoms of poisoning would probably include nausea, vomiting, dizziness. Collapse and coma may occur in severe poisoning. Dermal irritancy and allergic dermatitis may be seen in susceptible individuals following exposure to spray-mists, liquids or particulates.

5.1.3 Laboratory:

No specific biochemical tests available. Determination of alachlor and its metabolites in the blood or urine may confirm exposure.

5.1.4 Treatment:

Following dermal or oral exposure treatment is symptomatic. Vomiting should not be induced following ingestion of emulsifiable concentrate formulations unless the risk of pulmonary complications from the accompanying solvents can be avoided.

Activated charcoal may be given to reduce the extent of absorption. Residues must be thoroughly washed from skin and eyes. Treatment is symptomatic for irritation or allergic dermatitis.

5.1.5 Prognosis:

No published information available following systemic exposure, but the acute toxicity is low. Sensitized individuals should expect a recurrence of dermal reactions on re-exposure to alachlor and possibly to other acetanilide compounds.

5.1.6 References to previously reported cases:

No reported cases published.

5.2 Surveillance Tests:

None

5.3 Laboratory Methods

5.3.1 Detection and Assay of Compound:

Conkin RA (1978), Anal Methods Pestic Plant Growth Regul 10:255-265. Acad Press, New York, U.S.A.

5.3.2 Other Tests in Case of Poisoning:

None.

REFERENCES

IRPTC Legal File 1992-1995 (Vol.1): Regulations and Guidelines on Chemicals. An Extract of the IRPTC Data Bank. United Nations Environment Programme, Geneva (1993).

The Pesticide Manual, A World Compendium (10th Edition 1994), Tomlin, C., ed., British Crop Protection Council, 20 Bridport Road, Thornton Heath, CR4 7QG, U.K.

US EPA (1984), Alachlor Special Review, document 1. Office of Pesticide Programs.

WHO (1993), Guidelines for Drinking-Water Quality, 2nd ed., Vol.1, World Health Organization, Geneva, p.176.



    See Also:
       Toxicological Abbreviations
       Alachlor (ICSC)