IPCS INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY
Health and Safety Guide No. 51
PARAQUAT
HEALTH AND SAFETY GUIDE
UNITED NATIONS ENVIRONMENT PROGRAMME
INTERNATIONAL LABOUR ORGANISATION
WORLD HEALTH ORGANIZATION
WORLD HEALTH ORGANIZATION, GENEVA 1991
This is a companion volume to Environmental Health Criteria 39:
Paraquat and Diquat
Published by the World Health Organization for the International
Programme on Chemical Safety (a collaborative programme of the United
Nations Environment Programme, the International Labour Organisation,
and the World Health Organization)
This report contains the collective views of an international group of
experts and does not necessarily represent the decisions or the stated
policy of the United Nations Environment Programme, the International
Labour Organisation, or the World Health Organization
WHO Library Cataloguing in Publication Data
Paraquat : health and safety guide.
(Health and safety guide ; no. 51)
1. Paraquat - standards I. Series
ISBN 92 4 151051 X (NLM Classification: WA 240)
ISSN 0259-7268
(c) World Health Organization 1991
Publications of the World Health Organization enjoy copyright
protection in accordance with the provisions of Protocol 2 of the
Universal Copyright Convention. For rights of reproduction or
translation of WHO publications, in part or in toto, application
should be made to the Office of Publications, World Health
Organization, Geneva, Switzerland. The World Health Organization
welcomes such applications.
The designations employed and the presentation of the material in this
publication do not imply the expression of any opinion whatsoever on
the part of the Secretariat of the World Health Organization
concerning the legal status of any country, territory, city or area or
of its authorities, or concerning the delimitation of its frontiers or
boundaries.
The mention of specific companies or of certain manufacturers'
products does not imply that they are endorsed or recommended by the
World Health Organization in preference to others of a similar nature
that are not mentioned. Errors and omissions excepted, the names of
proprietary products are distinguished by initial capital letters.
CONTENTS
INTRODUCTION
1. PRODUCT IDENTITY AND USES
1.1. Identity
1.2. Physical and chemical properties
1.3. Analytical methods
1.4. Uses
2. SUMMARY AND EVALUATION
2.1. Environmental distribution and transformation
2.2. Kinetics and metabolism
2.3. Effects on experimental animals
2.4. Effects on human beings
2.4.1. Occupational exposure
2.4.2. Poisoning by paraquat
2.5. Effects on the environment
3. CONCLUSIONS AND RECOMMENDATIONS
3.1. Conclusions
3.1.1. General population exposure
3.1.2. Occupational exposure
3.1.3. General
3.2. Recommendations
3.2.1. General
3.2.2. Prevention and treatment
4. HUMAN HEALTH HAZARDS, PREVENTION AND PROTECTION, EMERGENCY ACTION
4.1. Main human health hazards, prevention and protection,
first aid
4.1.1. Advice to physicians
4.1.2. Health surveillance advice
4.1.3. Personal protection and hygienic measures
when handling concentrated paraquat
4.1.2. Health surveillance advice
4.1.3. Personal protection and hygienic measures
when handling concentrated paraquat
4.2. Explosion and fire hazards
4.3. Storage
4.4. Transport
4.5. Spillage and disposal
4.5.1. Spillage
4.5.2. Disposal
5. HAZARDS FOR THE ENVIRONMENT AND THEIR PREVENTION
6. SUMMARY OF CHEMICAL SAFETY INFORMATION
7. CURRENT REGULATIONS, GUIDELINES, AND STANDARDS
7.1. Previous evaluations by international bodies
7.2. Exposure limit values
7.3. Specific restrictions
7.4. Labelling, packaging, and transport
7.5. Waste disposal
BIBLIOGRAPHY
INTRODUCTION
The Environmental Health Criteria (EHC) documents produced by the
International Programme on Chemical Safety include an assessment of
the effects on the environment and on human health of exposure to a
chemical or combination of chemicals, or physical or biological
agents. They also provide guidelines for setting exposure limits.
The purpose of a Health and Safety Guide is to facilitate the
application of these guidelines in national chemical safety
programmes. The first three sections of a Health and Safety Guide
highlight the relevant technical information in the corresponding EHC.
Section 4 includes advice on preventive and protective measures and
emergency action; health workers should be thoroughly familiar with
the medical information to ensure that they can act efficiently in an
emergency. Within the Guide is a Summary of Chemical Safety
Information which should be readily available, and should be clearly
explained, to all who could come into contact with the chemical. The
section on regulatory information has been extracted from the legal
file of the International Register of Potentially Toxic Chemicals
(IRPTC) and from other United Nations sources.
The target readership includes occupational health services, those in
ministries, governmental agencies, industry, and trade unions who are
involved in the safe use of chemicals and the avoidance of
environmental health hazards, and those wanting more information on
this topic. An attempt has been made to use only terms that will be
familiar to the intended user. However, sections 1 and 2 inevitably
contain some technical terms. A bibliography has been included for
readers who require further background information.
Revision of the information in this Guide will take place in due
course, and the eventual aim is to use standardized terminology.
Comments on any difficulties encountered in using the Guide would be
very helpful and should be addressed to:
The Manager
International Programme on Chemical Safety
Division of Environmental Health
World Health Organization
1211 Geneva 27
Switzerland
THE INFORMATION IN THIS GUIDE SHOULD BE CONSIDERED AS A STARTING POINT
TO A COMPREHENSIVE HEALTH AND SAFETY PROGRAMME
1. PRODUCT IDENTITY AND USES
1.1 Identity
Common name paraquat
Molecular formula: C12H14N2Cl2
1,1'-dimethyl-4,4'-
bipyridyliumdichloride (paraquat
dichloride)
C12H14N2(CH3SO4)2
1,1'-dimethyl-4,4'-bipyridylium
dimethylsulfate sulfate (paraquat
dimethylsulfate)
Chemical structure of 1,1'-dimethyl-4,4'-bipyridylium-dichloride:
CAS chemical name: 1,1'-dimethyl-4,4'-bipyridylium (9 Cl)
Trade names: Gramoxone; Dextrone X; Esgram; and
others
CAS registry number: 4685-14-7 (ion)
1910-42-5 (dichloride)
4032-26-2 (diiodide)
2074-50-2 (dimethylsulfate)
RTECS registry number: DW1960000 (ion)
DW2275000 (dichloride)
DW2280000 (diiodide)
DW2010000 (dimethylsulfate)
Relative molecular mass: 186.2 (ion)
1.2 Physical and Chemical Properties
Pure paraquat salts are white and the technical products, yellow.
They are crystalline, odourless, hygroscopic powders.
Some of the physical properties of paraquat dichloride, the salt most
used for herbicide formulations, are listed in the Summary of Chemical
Safety Information (section 6).
Paraquat is slightly soluble in alcohol and practically insoluble in
organic solvents.
Paraquat is non-explosive and non-flammable in aqueous formulations.
It is corrosive to metals and incompatible with alkylarylsulfonate
wetting agents. It is stable in acid or neutral solutions, but is
readily hydrolysed by alkali.
1.3 Analytical Methods
Product analysis and determination of residues can be carried out
colorimetrically after reduction; impurities can be determined by
gas-liquid chromatography (GLC).
1.4 Uses
Paraquat is a total contact herbicide, applied around trees in
orchards and between crop rows, to control broad-leaved and grassy
weeds. It kills all green tissues, but does not harm mature bark.
Paraquat is used for plantation crops (banana, cocoa-palm, coffee,
oil-palm, rubber, etc.) and for citrus fruits, apples, plums, vines,
and tea. On certain crops (potato, pineapple, sugar-cane, sunflower),
it is used as a desiccant; it is also used as a cotton defoliant.
Uncropped land on industrial sites, railways, roadsides, etc. can be
cleared of weeds by applying high concentrations of paraquat.
2. SUMMARY AND EVALUATION
2.1 Environmental Distribution and Transformation
Photochemical degradation takes place when paraquat-treated plants are
exposed to normal daylight and continues after the plants die. The
products formed have been identified and found to be of a lower order
of toxicity than the parent compounds. Ultraviolet degradation on
soil surfaces also occurs, but photodecomposition of paraquat in the
soil is insignificant in comparison with adsorption on clay particles.
Microorganisms can degrade free paraquat rapidly, but chemical
degradation of adsorbed paraquat is relatively slow.
(a) Soil
Paraquat is rapidly and tightly bound to clay materials in soils.
The adsorbed paraquat is biologically inactive and, in normal
agricultural use, no harmful metabolic or breakdown products are to be
expected. In multiple spray trials, paraquat residues in soil varied
from 22 to 58 mg/kg. Under field conditions, the residual paraquat is
slowly redistributed. Long-term field studies have shown degradation
rates of 5-10% per annum, which is usually sufficient to prevent
saturation of the deactivation capacity of the soil. Thus, no adverse
effects are expected on the soil microflora and other soil organisms,
or on crop growth, at normal and high rates of application.
Paraquat is similarly strongly bound to humus and other organic
material in soils containing little clay. However, in sandy soils
with a low organic content, paraquat may be more readily released into
soil water and be more bioavailable to organisms. While it is still
unlikely to pose any hazard to the organisms in the soil, its
bioavailability to higher animals feeding on soil biota may be
increased.
(b) Water
When paraquat was applied as an aquatic herbicide, at a normal
application rate of 1 mg/litre, the concentration was found to
decrease to about one half of the initial level within 36 h and to
below 0.01 mg/litre in less than 2 weeks. Phytotoxic damage to crops
irrigated with treated water is unlikely to occur, if an interval of
10days is observed between treatment of the water and its use, because
of the rapid decrease of paraquat residues in the water.
Normal application of paraquat for aquatic weed control is not harmful
for aquatic organisms. However, care should be taken in the
application of paraquat to water containing heavy weed growth, since
oxygen consumed by subsequent weed decay may decrease oxygen levels in
the water to an extent that is dangerous for fish or other aquatic
organisms.
(c) Air
Paraquat is not volatile; thus, inhalation of paraquat vapour is not a
problem. The amount of respirable airborne paraquat was found to be
negligible under normal conditions of use.
The amount of paraquat present in airborne dust was found to range
from 0.0004 to 0.001 mg/m3. The paraquat was so strongly bound to
the dust particles that it did not exert any toxicological effect on
rats that were exposed via inhalation.
2.2 Kinetics and Metabolism
Although toxic amounts of paraquat may be absorbed after oral
ingestion, the greater part of ingested paraquat is eliminated
unchanged in the faeces. Paraquat is poorly absorbed through normal
human skin, but the extent of absorption may increase significantly in
cases of severe skin damage. The toxic effects of paraquat are
largely the result of a metabolically catalysed, single-electron,
reduction-oxidation reaction, resulting in depletion of cellular NADPH
and the generation of potentially toxic forms of oxygen, such as the
superoxide radical.
Absorbed paraquat is distributed via the bloodstream to practically
all organs and tissues of the body, but storage is not prolonged in
any tissue. The lung selectively accumulates paraquat from the plasma
by an energy-dependent process. Consequently, this organ contains
higher concentrations than other tissues. Since the removal of
absorbed paraquat occurs mainly via the kidneys, an early onset of
renal failure following uptake of toxic doses will have a marked
effect on paraquat elimination and distribution, and on its
accumulation in the lungs.
2.3 Effects on Experimental Animals
Paraquat induces a characteristic dose-related lung injury in the rat,
mouse, dog, and monkey, but not in the rabbit, guinea-pig, or hamster.
Pulmonary toxicity is characterized by the initial development of
pulmonary oedema and damage to the alveolar epithelium, which may
progress to fibrosis. Exposure to high doses of paraquat may also
cause less severe toxic effects in other organs, primarily the liver
and kidney. Minor toxic effects have been noted in the nervous,
cardiovascular, blood, adrenal, and male reproductive systems, but
only at high doses. Toxic effects have not been reported at low doses
of paraquat.
Paraquat has not been found to be teratogenic or carcinogenic in
long-term studies on rats and mice. The results of in vitro
mutagenicity studies were inconclusive, but generally suggested a
weak potential activity; the results of in vivo studies were
negative.
Concentrated solutions of paraquat have been found to irritate both
the skin and the eyes.
The FAO/WHO (1986) determined no-observed-effect levels of paraquat
dichloride of: 17 and 52 mg/kg diet, equivalent to 1.9 and 5.9 mg/kg
body weight, per day, for male and female mice, respectively; 30 mg/kg
diet, equivalent to 1.1 and 1.2 mg/kg body weight, per day, for male
and female rats, respectively; and 20 mg/kg diet, equivalent to 0.62
and 0.66 mg/kg body weight, per day, for male and female dogs,
respectively.
2.4 Effects on Human Beings
2.4.1 Occupational exposure
There are several studies on paraquat exposure during normal
agricultural use. The main route of occupational exposure of
agricultural workers is via the skin. The spray aerosol and dust
particles are relatively large and are mostly deposited in the upper
respiratory tract. Paraquat aerosol concentrations (total airborne)
ranged up to 0.55 mg/m3 in the work situation, depending on the
method of spraying. Under normal conditions of use, the amount of
respirable airborne paraquat was found to be insignificant.
The potential dermal exposure of field workers is closely related to
working conditions. Workers on tractors were found to have a paraquat
exposure of 12-168 mg/h, while spraying between tomatoes or citrus.
In other studies, field workers were dermally exposed to paraquat at
approximately 0.40 mg/h, and individuals spraying the garden, to
0.29 mg/h. In all trials, respiratory exposure was not higher than
0.01 mg/h. Urine concentrations in occupationally-exposed workers
were often lower than 0.01 mg/litre, but concentrations of up to
0.73 mg/litre were determined, after improper paraquat application in
tropical agriculture use.
2.4.2 Poisoning by paraquat
A large number of cases of poisoning have been reported, following the
drinking of concentrated paraquat, overwhelmingly with suicidal
intent. A few unusual cases, in which the liquid concentrate was used
improperly to treat body lice, have also been reported.
The possibility of patient recovery clearly depends on the dose of
paraquat taken and the time interval between ingestion and the
commencement of emergency treatment. Speed is imperative, and it
should be noted that emergency treatment can start before the patient
arrives at hospital.
In less severe cases, without lung damage, recovery has always been
complete.
(a) Suicidal ingestion
The majority of paraquat poisonings are due to swallowing liquid
concentrates. The response to treatment is disappointing and the
mortality rate is high. Ingestion of granular paraquat is less common
and usually causes milder poisoning, though fatalities have occurred.
(b) Accidental poisoning
Poisoning by accidental swallowing is less common than intentional
swallowing and is usually the result of storing liquid concentrates in
inappropriate containers, particularly beer or soft drink bottles.
The mortality rate is lower than in suicidal cases. Childhood
poisoning is usually accidental. In some countries, legislation on
the control of the sale of liquid concentrates has reduced accidental
ingestion.
A small number of fatal cases of accidental paraquat poisoning via the
skin have been reported following the intentional application of
liquid concentrates (200 g/litre) to kill body lice.
(c) Occupational poisoning
A number of cases of severe poisoning following inappropriate
behaviour have occurred. Fatal poisoning through dermal soaking with
insufficiently diluted paraquat, associated with severe skin lesions,
has been reported. This may result from continuous contact with
paraquat-soaked clothing, e.g., as a result of using a leaking
sprayer.
Splashes of liquid concentrate may lead to severe ocular and skin
damage. Spraying with inadequately diluted paraquat (e.g., with
ultra-low-volume application) may result in similar problems.
Local skin effects (contact, irritative, or photoallergic dermatitis),
delayed wound healing, and nail damage have been observed among
formulation workers and among individuals handling the herbicide
improperly. Blepharitis and epistaxis may result through the delayed
irritative action of paraquat. Such incidents illustrate the need for
strict personal hygiene and rigorous adherence to safe handling
procedures (see section 4).
2.5 Effects on the Environment
The fact that paraquat is used as a herbicide indicates that it is
toxic for aquatic and terrestrial vegetation.
On reaching the soil, paraquat becomes rapidly and strongly adsorbed
on the clay minerals present. This process inactivates the herbicidal
activity of the compound. Strongly-bound paraquat does not have any
adverse effects on soil microfauna or soil microbial processes.
Paraquat residues disappear rapidly from water by adsorption on
aquatic weeds and by strong adsorption on the bottom mud. The
toxicity of paraquat for fish is low, and the compound is not
cumulative. Normal applications of paraquat for aquatic weed control
are not harmful for aquatic organisms. However, when applying
paraquat to water containing heavy weed growth, care should be taken
to treat only a part of the growth, since oxygen consumption by
subsequent weed decay may result in a reduction in dissolved oxygen
levels to an extent that may be dangerous for fish.
Treated water should not be used for overhead irrigation for 10 days
following treatment.
Normal use of paraquat has been shown not to have any harmful effects
on birds.
Paraquat is not subject to bioconcentration and has not been found to
accumulate in food chains.
3. CONCLUSIONS AND RECOMMENDATIONS
3.1 Conclusions
3.1.1 General population exposure
Residue levels of paraquat in food and drinking-water, resulting from
its normal use, are unlikely to pose a health hazard for the general
population.
This likely lack of hazard with normal usage of dilute paraquat
contrasts strongly with the potentially serious hazard that may result
from handling concentrated paraquat.
Accidental paraquat poisoning usually results from swallowing liquid
concentrate that has been decanted into unlabelled bottles or other
containers, and stored inappropriately.
The number of suicides by means of paraquat is of great concern, but
the total number of such suicides is unknown. The reasons for suicide
may be manifold and complex, and paraquat is only one among many means
towards this goal. However, because of the prolonged and painful way
of dying from paraquat poisoning, every effort should be made to
diminish its attractiveness and availability for this purpose.
3.2.1 Occupational exposure
With reasonable work practices, including safety precautions, hygiene
measures, and proper supervision, occupational exposure during the
manufacture, formulation, and application of paraquat will not cause a
hazard. However, the undiluted concentrate must be handled with great
care, because improper work practices may result in the contamination
of the eyes and skin (with possible consequent dermal absorption).
Spray concentrations should not exceed 5 g paraquat ion/litre, in
order to avoid skin damage and absorption of the herbicide through the
skin. Hand-held, ultra-low-volume application should be discouraged.
3.1.3 Environment
Paraquat in soil binds rapidly and strongly to clay particles, and
residual phytotoxicity from freely-available paraquat is unlikely.
The toxicity of paraquat for birds has been shown to be of little
significance. Under normal conditions of use, paraquat toxicity for
aquatic animal life is low, though the resulting depletion of
water-oxygen, because of weed decay, may pose a problem. Paraquat
does not seem to present an environmental hazard.
3.2 Recommendations
3.2.1 General
Where practical and reasonable, the availability and use of the 20%
liquid product should be limited to bona fide agriculturalists,
horticulturalists, and professional users, who work with trained
personnel, properly maintained equipment, and adequate supervision.
Every effort should be made to prevent the practice of decanting into,
or rebottling of the product in, improperly labelled containers.
Further research should be carried out, to achieve a safer commercial
product and a reduced incidence of fatalities.
National Registers of cases of poisoning should be maintained for all
classes of chemicals, including paraquat. The information obtained
should be made available to international bodies, such as the World
Health Organization.
3.2.2 Prevention and treatment
Attention should be drawn to the fact that persons with skin lesions
(either pre-existing or following contamination with paraquat) should
not be permitted to take any part in spraying procedures, until the
skin condition has resolved.
It must be stressed that treatment of persons with paraquat poisoning
should be instituted as early as possible. The likelihood of recovery
from a potentially fatal dose is greatest when therapy begins within
5-6 h of poisoning.
4. HUMAN HEALTH HAZARDS, PREVENTION AND PROTECTION, EMERGENCY ACTION
4.1 Main Human Health Hazards, Prevention and Protection, First Aid
Paraquat is highly toxic and often fatal, if swallowed. Contact with
liquid products can cause severe damage to the skin or eyes. Utmost
care must be taken to avoid exposure during handling operations and
application in the field. In applications where inhalation exposure
to aerosols containing paraquat is likely, proper respiratory
protective equipment should be used.
The human health hazards, together with preventive and protective
measures and first-aid recommendations, are listed in the Summary of
Chemical Safety Information (section 6).
4.1.1 Advice to physicians
The most important measures are the immediate neutralization of
ingested paraquat by 15% Fuller's earth, bentonite, or activated
charcoal, and urgent removal of the poison by vomiting or, when
possible, gastric lavage. The urgency of these measures is such that,
where transfer to hospital may involve a delay of an hour or more, the
emergency treatment may need to be given by a paramedical person,
e.g., a nurse or a medical assistant, without any delay. Furthermore,
Fuller's earth should be given together with a strong purgative, such
as magnesium sulfate or mannitol.
Admission to a hospital (preferably a specialized intensive care
unit), either directly, or after emergency treatment elsewhere, is
essential.
Where a person has swallowed a lethal dose, the most important single
determinant of survival is the early commencement of treatment.
Depending on local facilities, patients who reach hospital after the
initial treatment will have further treatment aimed at neutralizing
paraquat in the gastrointestinal tract (Fuller's earth, bentonite,
activated charcoal) or its excretion in the faeces (purgatives, 10%
mannitol, gut lavage). In addition, attempts to remove absorbed
paraquat from the circulation (haemoperfusion, haemodialysis) or aid
its excretion by the kidney (forced diuresis) can be instituted.
Care must be exercised in the administration of most of these
treatments, as the following serious complications may occur:
perforation of the oesophagus during gastric intubation; serious blood
chemistry disturbance, when severe diarrhoea is induced; fluid
overload during forced diuresis.
In centres where facilities for analytical procedures are available,
measurement of urinary, or, ideally, plasma levels of paraquat may
give guidelines for the required intensity of treatment or likely
prognosis. Determination of paraquat levels in stomach washings,
serum, and urine is useful for the management of poisoning. The
urinary levels decline rapidly during the 24 h following exposure and
may remain low for some weeks.
Many other therapies including corticosteroids, immunosuppressive
treatment, vitamins, beta-blocking and alkylating agents,
alpha-tocopherol, superoxide dismutase and/or glutathione peroxides
proved to be of no significant importance in human paraquat poisoning.
The administration of oxygen should be avoided, unless vital for the
patient's comfort.
It should be noted that, as with the great majority of chemicals,
there is no specific antidote.
Despite such an array of both simple and sophisticated measures, the
response to therapy in paraquat poisoning is disappointing and the
mortality rate remains high.
In cases of skin and eye contamination, irrigation with water
(preferably running water) should be commenced urgently and must be
continued uninterrupted for at least 15 minutes (timed by the clock).
Eye cases should always be taken for medical treatment. In cases of
skin contamination by the concentrate, or extensive and/or prolonged
contamination by the diluted material (particularly where signs of
skin irritation are present), the patient must be assessed at hospital
for systemic poisoning.
4.1.2 Health surveillance advice
Pre-employment and annual medical examinations should be made
available to all persons who are regularly exposed to paraquat at
potentially hazardous levels. Attention should be given to all normal
parameters of overall health status, with particular attention to the
state of the skin and of pulmonary function.
4.1.3 Personal protection and hygienic measures
Avoid all contact with skin, eyes, nose, and mouth, when handling
concentrated paraquat. Wear PCV-, neoprene- or butyl-rubber gloves
(preferably gauntlet form), neoprene apron, rubber boots, and face
shield.
* Wear a face-shield when handling and applying the diluted
formulation.
* Immediately remove heavily contaminated clothing and wash
underlying skin.
* Wash clothes before re-use.
* Do not eat, drink, or smoke, when using paraquat.
* Wash splashes from skin or eyes immediately.
* Do not inhale spray.
* Wash hands and exposed skin, before meals and after work.
* Keep away from food, drink, and animal feed.
* Paraquat should not be sprayed with inadequate dilution, e.g., by
hand-held, ultra-low-volume application.
* It should not be used by people suffering from dermatitis or by
people with wounds, notably on the hands, until these have
healed.
4.2 Explosion and Fire Hazards
Paraquat products are generally not flammable. If involved in a fire,
control with dry powder or alcohol-resistant foam. Advise the fire
service that protective clothing and self-contained breathing
apparatus should be worn, to avoid skin contamination and the
breathing of toxic fumes. Confine the use of water spray to the
cooling of unaffected stock, thus avoiding the accumulation of
polluted run-off from the site.
4.3 Storage
Store technical material and formulations away from heat, under lock
and key, and out of reach of children, animals, and unauthorized
personnel. Store in an area designated for pesticide storage,
preferably without drains.
Store away from foodstuffs and animal feed.
4.4 Transport
Ensure that containers are sound and that labels are securely fixed
and undamaged before dispatch. Comply with local transport
regulations.
Do not load together with foodstuffs or animal feed.
Accident procedures:
Avoid exposure by the use of appropriate protective clothing, gloves,
and goggles or masks. Keep spectators away from leaking or spilled
product and prevent smoking, and the use of naked flames, in the
immediate vicinity.
Extinguish fires with dry powder, carbon dioxide, alcohol-resistant
foam, sand, or earth.
Prevent liquid from spreading to other cargo, vegetation, or waterways
by containing it with the most readily available barrier material,
e.g., earth or sand.
Absorb spilled liquid and cover contaminated areas with earth, lime,
sand, or other absorbent material; sweep up and place in a secure
container for subsequent safe disposal.
4.5 Spillage and Disposal
4.5.1 Spillage
Avoid exposure by the use of appropriate protective clothing and
face-shield.
Empty any product remaining in damaged or leaking containers into a
clean empty drum and label.
Absorb spillage with lime, damp sawdust, sand, or earth and dispose of
safely (see below). If spillage is large, contain it by building a
barrier of earth or sandbags.
Decontaminate empty, damaged, or leaking containers with a 10% sodium
carbonate solution, added at the rate of at least 1 litre per 20-litre
drum. Puncture or crush containers to prevent re-use.
4.5.2 Disposal
Waste containing paraquat should be burnt in a proper high temperature
incinerator with effluent gas scrubbing.
Where no incinerator is available, contaminated absorbents or surplus
products should be decomposed by hydrolysis at pH 12 or above. A 5%
sodium hydroxide (caustic soda) solution or saturated (7-10%) sodium
carbonate (washing soda) solution can be used. Before disposal of the
resultant waste, the material must be analysed to ensure that the
active ingredient has been degraded to a safe level.
Paraquat is rapidly inactivated by clay soil. If the above mentioned
methods are not possible, it can be buried in an approved landfill.
Never pour untreated waste or surplus products into public sewers or
where there is any danger of run-off or seepage into streams,
water-courses, open waterways, ditches, fields with drainage systems,
or the catchment areas of boreholes, wells, springs, or ponds.
5. HAZARDS FOR THE ENVIRONMENT AND THEIR PREVENTION
Paraquat is highly toxic for aquatic and terrestrial vegetation.
Under normal conditions of use, the toxicity of paraquat for aquatic
animal life is low, though resulting depletion of water-oxygen,
because of weed decay, may pose a problem.
Do not contaminate ponds, waterways, or ditches with the product or
used containers.
6. SUMMARY OF CHEMICAL SAFETY INFORMATION
This summary should be easily available to all health workers
concerned with, and users of, paraquat. It should be displayed at, or
near, entrances to areas where there is potential exposure to
paraquat, and on processing equipment and containers. The summary
should be translated into the appropriate language(s). All persons
potentially exposed to the chemical should also have the instructions
in the summary clearly explained.
Space is available for insertion of the National Occupational
Exposure Limit, the address and telephone number of the National
Poison Control Centre, and for local trade names.
PARAQUAT
(C12H14N2Cl2) 1,1'-dimethyl-4,4'-bipyridylium dichloride (paraquat dichloride)
CAS registry no. 1910-42-5
RTECS registry no. DW2275000
PHYSICAL PROPERTIES OTHER CHARACTERISTICS
Physical state crystalline powder Total contact herbicide, used to control broad-leaved
Colour yellow and grassy weeds; corrosive to metals, and incompatible
Odour odourless with alkylarylsulfonate wetting agents; stable in acid
Relative molecular mass 186.2 (ion) or neutral solutions, but readily hydrolysed by alkali;
Specific gravity (20°C) 1.240-1.260 slightly soluble in alcohol and practically insoluble in
Melting point (°C) 175-180 organic solvents
Boiling point (°C) approximately 300
with decomposition
Solubility in water (20°C) 700 g/litre
pH of liquid formulation 6.5-7.5
Vapour pressure not measurable
HAZARDS/SYMPTOMS PREVENTION AND PROTECTION FIRST AID
SKIN: Irritating to skin, may Proper application technique; Remove contaminated clothing; wash skin with
cause blisters proper skin protection, soap and water; wash clothes before re-use
including impervious clothing
and gloves
EYES: Severe irritant Wear face-shield; goggles Flush immediately with clean water for at least
15 minutes; seek medical advice and observe
for delayed effects
INHALATION: Irritant to Avoid inhalation of fine dust Fresh air
respiratory system and mist; use proper
respiratory protection
INGESTION: Unlikely Do not eat, drink, or smoke
occupational hazard during working hours; wash
hands
Accidental or deliberate ingestion Obtain medical attention immediately;
may cause vomiting, abdominal transport to hospital urgently; induce vomiting;
discomfort, and soreness of mouth do not delay
and throat; signs of liver and kidney
damage may appear in 1-3 days;
signs of lung damage may gradually
develop after a few days; paraquat
can kill
SPILLAGE STORAGE FIRE AND EXPLOSION
Absorb spillage with lime, damp Store in locked, well-ventilated Non-flammable and non-explosive
sawdust, sand, or earth; sweep up, storeroom, away from
place in closed container, and foodstuffs and animal feed,
dispose of safely; avoid children, and unauthorized
contamination of personnel, ponds, personnel
and waterways
WASTE DISPOSAL
Burn in high-temperature National Occupational Exposure UN No. 2781, 2782, 3015, 3016
incinerator with effluent scrubbing; Limit:
alternatively treat with 5% caustic
soda as a hydrolysing agent; comply National Poison Control Centre:
comply with local regulations
Local trade names:
7. CURRENT REGULATIONS, GUIDELINES, AND STANDARDS
The information given in this section has been extracted from the
International Register of Potentially Toxic Chemicals (IRPTC) legal
file. A full reference to the original national document from which
the information was extracted can be obtained from IRPTC. When no
effective date appears in the IRPTC legal file, the year of the
reference from which the data are taken is indicated by (r).
The reader should be aware that regulatory decisions about chemicals,
taken in a certain country, can only be fully understood in the
framework of the legislation of that country. The regulations and
guidelines of all countries are subject to change and should always be
verified with appropriate regulatory authorities before application.
7.1 Previous Evaluations by International Bodies
The FAO/WHO Joint Meeting on Pesticide Residues (JMPR) has reviewed
residues and toxicity data on paraquat on several occasions (1970,
1972, 1976, 1978, 1981, 1982, 1985, and 1986). In 1986, it estimated
the acceptable daily intake (ADI) for man to be 0-0.006 mg paraquat
dichloride/kg body weight (or 0.004 mg paraquat ion/kg body weight).
The same JMPR recommended maximum residue levels (tolerances) for
paraquat in food commodities of plant and animal origin.
The WHO/FAO (1979), in its series of "Data sheets on chemical
pesticides", issued one on paraquat (No. 4). It classified technical
paraquat as moderately hazardous in normal use (WHO, 1990).
7.2 Exposure Limit Values
Some exposure limit values are given in the table on pages 30-32.
7.3 Specific Restrictions
Paraquat is prohibited for use in, amongst other countries, Finland
and Sweden.
In some other countries, e.g., the Federal Republic of Germany,
Hungary, the United Kingdom, and the USA, the use of paraquat is only
registered for certain specified applications or for use under certain
specified conditions. For instance, in the United Kingdom and the USA,
the use of the 20% liquid is restricted to bona fide, certified
professionals. In the Federal Republic of Germany, paraquat may not
be handled by adolescents or pregnant or nursing women.
EXPOSURE LIMIT VALUES
Medium Specification Country/ Exposure limit descriptiona Value Effective
organization date
AIR Work-place Argentina Maximum permissible concentrationb
- Time-weighted average (TWA) 0.1 mg/m3 1979
Australia Threshold limit value (TLV)b
- Time-weighted average (TWA) 0.5 mg/m3 1983
of respirable dust (provisional)
Belgium Tolerable limit value (TLV)
- Time-weighted average (TWA) 0.1 mg/m3 1988
Bulgaria Maximum permissible concentrationb
- Time-weighted average (TWA) 0.1 mg/m3 1987
Germany, Federal Maximum work-site concentration (MAK)b
Republic of - Time-weighted average (TWA) 0.1 mg/m3 1988
- Short-term exposure level (STEL) 0.2 mg/m3
(5min) (8 × per shift)
(ceiling value)
Hungary Maximum permissible concentration
- Time-weighted average (TWA) 0.02 mg/m3 1978
- short-term exposure level (STEL) 0.02 mg/m3
(30 min)
Netherlands Maximum permissible concentration
- Time-weighted average (TWA) 0.1 mg/m3 1986
Switzerland Maximum work-site concentration (MAK)b
- Time-weighted average (TWA) 0.1 mg/m3 1987
Medium Specification Country/ Exposure limit descriptiona Value Effective
organization date
AIR Work-place United Kingdom Recommended limit
- 8-h Time-weighted average (TWA) 0.1 mg/m3 1987
(of respirable dust)
USA (OSHA) Permissible exposure limit (PEL)b
- Time-weighted average (TWA) 0.1 mg/m3 1989
(respirable dust)
USA (ACGIH) Threshold limit value (TLV)
- Time-weighted average (TWA) 0.1 mg/m3 1987
(respirable sizes)
FOOD Intake from FAO/WHO Acceptable daily intake (ADI) 0-0.004 mg/kg 1986
(paraquat ion) body weight
FOOD General FAO/WHO Maximum residue limit (MRL) 0.01-10 mg/kg 1983
for specified products
European Maximum levels in and on fruit
Community and vegetables 0.05 mg/kg 1989
(expressed as paraquat cation)
a TWA=time-weighted average over one working day (usually 8h).
b Skin absorption.
7.4 Labelling, Packaging, and Transport
The United Nations Committee of Experts on the Transportation of
Dangerous Goods classifies paraquat in:
* Hazard Class 6.1: poisonous substance.
* Packing Group II: substances and preparations presenting a
serious risk of poisoning, when the active ingredient is within
the range of 40-100%.
* Packing Group III: substance presenting a relatively low risk of
poisoning in transport, when the active ingredient is in the
range of 8-40%.
The labels should be as follows:
The European Economic Community legislation requires labelling of
paraquat as a dangerous substance using the symbol:
The label must read:
Toxic in contact with skin and if swallowed; irritating to eyes,
respiratory system and skin.
The European Economic Community legislation on the labelling of
pesticide preparations classifies paraquat in Class 1A, for the
purpose of determining the label for preparations containing paraquat
and other active ingredients.
The chemical name must be stated on the label.
The FAO specifications for plant protection products containing
paraquat specify the composition and purity of its formulations and
the methods for checking this. They also specify the quality of the
containers.
7.5 Waste Disposal
In the USA, paraquat is regarded as a hazardous waste and permits are
required for its discharge from any point source into USA national
waters. This requirement contains detailed instructions.
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