IPCS INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY
Health and Safety Guide No. 74
PARATHION
HEALTH AND SAFETY GUIDE
UNITED NATIONS ENVIRONMENT PROGRAMME
INTERNATIONAL LABOUR ORGANISATION
WORLD HEALTH ORGANIZATION
WORLD HEALTH ORGANIZATION, GENEVA 1992
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
Parathion : health and safety guide.
(Health and safety guide ; no. 74)
1. Parathion - poisoning 2. Parathion - standards
3. Parathion - toxicity 4. Environmental exposure I.Series
ISBN 92 4 151074 9 (NLM Classification: WA 240)
ISSN 0259-7268
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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. Exposure
2.2. Poisoning cases in humans
2.3. Evaluation of human health risks
2.4. Effects on the environment
3. CONCLUSIONS AND RECOMMENDATIONS
3.1. Conclusions
3.2. Recommendations
4. HUMAN HEALTH HAZARDS, PREVENTION AND PROTECTION,
EMERGENCY ACTION
4.1. Human health hazards, prevention and
protection, first aid
4.1.1. Advice to physicians
4.1.1.1 Symptoms of poisoning
4.1.1.2 Medical treatment
4.1.2. Health surveillance advice
4.2. Safety in use
4.3. Explosion and fire hazards
4.4. Storage
4.5. Transport
4.6. Spillage and disposal
4.6.1. Spillage
4.6.2. Disposal
5. HAZARDS FOR THE ENVIRONMENT AND THEIR PREVENTION
6. CURRENT REGULATIONS, GUIDELINES, AND STANDARDS
6.1. Previous evaluations by international bodies
6.2. Exposure limit values
6.3. Specific restrictions
6.4. Labelling, packaging, and transport
6.5. Waste disposal
6.6. Other measures
BIBLIOGRAPHY
ANNEX 1
INTRODUCTION
This Health and Safety Guide is not based on an existing
Environmental Health Criteria document, but on critical national
reviews. The hazard evaluation in the Health and Safety Guide was
made on the basis of carefully selected studies, after scrutiny of
the original publications.
In order to assist the peer-review process of the present Health and
Safety Guide, a background companion document was prepared by the
IPCS and can be obtained from the Director on request; the IPCS does
not intend that the background document should be published.
The first three sections of this Health and Safety Guide present
essential technical information and the hazard evaluation. 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. 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.
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 Director
International Programme on Chemical Safety
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
Chemical structure:
Molecular formula: C10H14NO5PS
Common name: Parathion (BSI, E-ISO, F-ISO, JMAF);
parathion ethyl (some countries);
thiophos (USSR)
CAS chemical name: O,O-diethyl O-(4-nitrophenyl)
phosphorothioate (9CI)
CAS registry number: [56-38-2]
OMS number: 19
RTECS registry number: TF4550000
Technical parathion is at least 95% pure.
1.2 Physical and chemical properties
Pure parathion is a pale yellow liquid. The technical material is a
brown liquid with garlic-like odour. It is slightly soluble in
water, heptane, and in petroleum oils, but readily soluble in most
organic solvents, such as acetone, benzene, chloroform, ethanol, and
xylene.
Parathion is hydrolysed very slowly at pH 1-7, but undergoes rapid
decomposition at higher pH. On heating, parathion readily isomerizes
to the O,S-diethyl analogue. It is generally considered to be a
non-persistent compound.
Some physical properties of parathion are given in Table 1.
Table 1. Physical properties
Relative molecular mass: 291.3
Boiling point 157-162 °C at 0.6 mmHg
25
Density d4 1.265
Vapour pressure (20 °C) 5.0 mPa
Water solubility (25 °C) 24 mg/litre
(40 °C) 77 mg/litre
Flash point (open cup)(°C) 200
Hydrolysis in aqueous solution
at pH 5.0-6.0 (25 °C) 1% in 62 d
Log Pow 3.15
1.3 Analytical methods
The active ingredient content of formulated products has been
determined using gas chromatography, high pressure liquid
chromatography, or hydrolysis to 4-nitrophenol for colorimetric
determination. Gas chromatographic and thin-layer chromatographic
methods are available for residue determination.
Recommendations for the methods of determining parathion residues
have been given by the Codex Alimentarious Commission (FAO/WHO,
1989).
1.4 Uses
Parathion is a non-systemic insecticide that controls numerous
insects by contact and stomach action. It is used in many countries
throughout the world. It has some fumigant as well as acaricidal
activity. Parathion is used as a pre-harvest soil and foliage
treatment on a wide variety of crops, both outdoors and in
glasshouses. The usual application rate is 0.2-1 kg/ha. Parathion is
non-phytotoxic, except to some sensitive ornamentals, apples, and
pears.
Parathion is available as 15 and 25% wettable powders, 2, 4, 6, and
8% emulsifiable concentrates, 0.5, 1, and 2% dust, 10% granules and
10% aerosols.
2. SUMMARY AND EVALUATION
2.1 Exposure
In the environment, parathion is degraded quite rapidly, mainly by
hydrolysis, but to a certain extent also by reduction of the nitro
group as well as conversion to the oxon. The half-life of the oxon
is much shorter than that of parathion itself, and it does not
accumulate.
The general population is not usually exposed to parathion from air
or water, parathion residues in food being the main source of
exposure. Dermal exposure may also occur through accidental contact
with foliar residues in sprayed fields or in areas adjacent to
spraying operations, as a consequence of off-target loss of
parathion. With correct usage, however, persons not occupationally
involved should not be exposed to hazardous amounts.
The data on levels of parathion reported so far by the Joint FAO/WHO
Food Contamination Monitoring Programme indicate that parathion does
not occur substantially above detection limits in most cases.
However, sporadic instances of higher levels in fruit and vegetables
indicate that contamination of crops can occur under certain
conditions of use (GEMS, 1986).
Analysis of fruit and vegetables entering commerce in Germany showed
that only 14 out of 228 samples contained measurable amounts of
parathion (more than 0.01 mg/kg). In most of these cases, the
residue was less than 0.1 mg/kg, but 2 samples of lettuce contained
residue levels of 0.15 and 1.5 mg/kg, respectively. One sample of
parsley contained 0.4 mg parathion/kg.
Total-diet studies in the USA in 1965-66 showed that only very low
residues (0-0.001 mg/kg) were present in vegetables and fruits, as
consumed. In 1963-64, parathion residues in food in commerce were
0.03-0.83 mg/kg.
Occupational exposure to parathion may occur during manufacturing,
formulation, application, and storage. This exposure is mainly
through dermal absorption and inhalation. Higher occupational
exposures may be observed in cases of accident, or as a result of
incorrect handling.
2.2 Poisoning cases in humans
There are more reported cases of poisoning with parathion than with
any other pesticide currently in use. There have been a number of
cases where intoxication and death have resulted from ingestion of
foodstuffs that have been grossly contaminated with parathion.
In one Asian country, there were 828 cases of poisoning with 106
deaths caused by flour, sugar, and other foodstuffs becoming
contaminated because parathion was transported in the same ship's
hold as the food. In another Asian country, barley became
contaminated with parathion. There were 38 cases of poisoning with
nine deaths.
In a country in the Americas, there were 559 cases of poisoning and
16 deaths when sacks of sugar, and possibly flour, absorbed
parathion from the floor of a truck. In another country in the
Americas, there were 165 known, and 445 more suspected, cases of
poisoning with 63 deaths, when parathion from broken containers
contaminated sacks of flour during transportation in a truck. In a
European country, there were 26 cases of poisoning, but no deaths,
when flour became contaminated because of transportation in a wagon
that was previously used for the transportation of parathion.
Several operators have died after rather extensive skin contact with
diluted agricultural sprays or dusts.
2.3 Evaluation of human health risks
Parathion is highly toxic and extremely hazardous (WHO, 1990), the
oral LD50 in the rat being of the order of 13 mg/kg. In man, an
oral dose of 3-5 mg/kg is usually fatal.
Parathion is easily absorbed through the intact skin, as well as by
inhalation and via the gastrointestinal tract. It is converted in
vivo to the more toxic oxygen analogue paraoxon, which inhibits
acetylcholinesterase. In the mouse, the LD50 of paraoxon by the
oral route is 12.8 mg/kg body weight. It is rapidly distributed to
all organs and tissues in the body. The presence of the metabolite
p-nitrophenol in the urine is used to monitor worker exposure to
parathion.
Parathion is not irritating to the eyes, but a single drop in the
eye could be fatal. It is also not irritating to the nose and
throat, but it is highly poisonous when inhaled. It is not
irritating to the skin but is rapidly absorbed through the intact
skin.
The acute and short-term studies on parathion are comprehensive and
cover a wide range of animal species. Long-term studies have been
carried out on the rat. The results of studies on the dog, though
limited, suggest that this species is more sensitive than the rat to
the anticholinesterase activity of parathion. Several short-term
studies have been conducted on groups of human volunteers. Man and
the rat are equally sensitive to the anticholinesterase action of
parathion. Erythrocyte cholinesterase activity is the most sensitive
indicator of this action of parathion and a wide margin exists
between the highest dose without action on cholinesterase activity
and the lowest dose needed to cause a clinical effect.
Parathion was not mutagenic to a wide range of microorganisms in the
presence or absence of rat liver microsomal preparations. It did not
induce unscheduled DNA synthesis in cultured mammalian cells,
recessive lethal mutations in Drosophila melanogaster, or dominant
lethal mutations in mice. Thus, no evidence has been found that
parathion is mutagenic.
Parathion was tested for carcinogenicity in one strain of mice and
in three strains of rats by administration in the diet. Although a
dose-related increase in the incidence of adrenal cortical adenomas
was observed in male and female rats of one strain, the significance
of the occurrence of these lesions in aged rats is not well
understood. A low incidence of carcinomas at this site was observed
in each of the treated groups in animals of both sexes.
Evidence is inadequate to evaluate the carcinogenicity of parathion
in experimental animals, and the available data are insufficient to
evaluate the carcinogenicity of parathion for humans (IARC, 1983).
Parathion produced embryocidal effects and fetal growth retardation,
but no malformations, in mice and rats at doses that were generally
below the level that was toxic for the mother.
Maximum levels causing no significant toxicological effects in
long-term studies (FAO/WHO, 1968) are as follows:
* Rat: the maximum level having no effect on cholinesterase
activity in the rat was 1 mg/kg in the diet, equivalent to 0.05
mg/kg body weight.
* Man: 0.05 mg/kg body weight per day.
The estimated acceptable daily intake for man (FAO/WHO, 1968) is
0-0.005 mg/kg body weight.
2.4 Effects on the environment
Parathion is degraded in soil, plants, and other substrates at a
moderate rate, though such conversion may be initially to the more
toxic metabolite paraoxon. Such conversion is especially true under
dry, hot conditions. The other degradation products are
p-nitrophenol, p-aminophenol, diethyl thiophosphoric acid, and
diethylphosphoric acid.
Parathion is highly toxic for fish, lower aquatic organisms, birds,
wild mammals, and soil organisms. There is no build up of this
insecticide in food-chains.
3. CONCLUSIONS AND RECOMMENDATIONS
3.1 Conclusions
Parathion is a highly toxic organophosphorus ester insecticide.
Overexposure through handling during manufacture or use, and/or
accidental or intentional ingestion may cause severe or fatal
poisoning. Parathion formulations may, or may not, be irritating to
the eyes or to the skin, but they are absorbed readily. As a
consequence, hazardous exposures may occur without warning.
Exposure of the general population to parathion residues occurs
predominantly via food. If good agricultural practice is followed,
the Acceptable Daily Intake (0-0.005 mg/kg body weight), established
by FAO/WHO, will not be exceeded. Dermal exposure may also occur
through accidental contact with foliar residues in sprayed fields or
in areas adjacent to spraying operations as a result of off-target
loss of the chemical.
With good work practices, hygienic measures, and safety precautions,
parathion is unlikely to present a hazard for those occupationally
exposed.
Parathion is degraded in the environment at a moderate rate. It is
highly toxic for fish, lower aquatic organisms, birds, wild mammals,
and soil organisms. There is no build up of this insecticide in
food-chains.
3.2 Recommendations
The existing uses of parathion in each country should be evaluated
in terms of risk-benefit, and serious consideration should be given
to replacing parathion with less hazardous chemicals.
For the health and welfare of workers and the general population,
the handling and application of parathion should be entrusted only
to competently supervised and well-trained applicators, who must
follow adequate safety measures and use the chemical according to
good application practices.
The manufacture, formulation, agricultural use, and disposal of
parathion should be carefully managed to minimize contamination of
the environment.
Regularly exposed workers should receive appropriate monitoring and
health evaluation.
To minimize risk to all individuals, a 48-h interval between
spraying and re-entry into any sprayed area is recommended.
Pre-harvest intervals should be established and enforced by national
authorities.
In view of the high toxicity of parathion, this agent should not be
considered for use in hand-applied, ultra-low-volume (ULV) spraying
practices.
Do not overspray water bodies. Time spraying to avoid killing
pollinating insects.
4. HUMAN HEALTH HAZARDS, PREVENTION AND PROTECTION, EMERGENCY
ACTION
4.1 Human health hazards, prevention and protection, first aid
The acute oral and dermal toxicities of parathion are high and it is
extremely hazardous for human beings, if incorrectly handled. With
excessive exposure, typical signs and symptoms of organophosphorus
poisoning may occur rapidly. For details see Table 2.
4.1.1 Advice to physicians
For a more complete treatise on the effects of organophosphorus
insecticides, especially their short- and long-term effects on the
nervous system, refer to EHC 63: Organophosphorus insecticides - a
general introduction (WHO, 1986).
4.1.1.1 Symptoms of poisoning
Parathion is an indirect inhibitor of cholinesterase, i.e., it is
converted in the body into the active transformation product
paraoxon. As a result, signs and symptoms of poisoning develop after
a latent period and may continue to increase after exposure has been
discontinued.
Signs and symptoms may include a feeling of exhaustion, headache,
blurred vision, weakness, and confusion. Vomiting, abdominal pain,
excessive sweating, and salivating may develop. The pupils are
constricted. Difficulty in breathing may be experienced, due to
congestion of the lungs and weakness of the respiratory muscles.
Arrhythmias and cardiac failure have been reported. On severe
poisoning, there will be muscle spasms, unconsciousness, and
convulsions. Breathing may stop, followed by death.
4.1.1.2 Medical treatment
If ingested and the formulation does not contain petroleum
distillates, induce vomiting, or preferably perform gastric lavage
using 5% sodium bicarbonate. In the case of ingestion of liquid
formulations containing hydrocarbon solvents, vomiting involves a
risk of aspiration pneumonia.
Table 2. Human health hazards, preventive and protective measures, and first aid
HAZARD/SYMPTOM PREVENTION AND PROTECTION FIRST AID
GENERAL Cholinesterase inhibition Avoid exposure
SINGLE EXPOSURE
SKIN Contamination may cause PVC or neoprene gloves, apron, Remove contaminated clothing;
poisoning and rubber boots wash contaminated skin with water
and soap; obtain medical attention
immediately; launder contaminated
clothing separately before reuse
EYES Redness, irritation Goggles or face shield Flush immediately with clean water for
at least 15 min; if irritation
persists, obtain medical attention
INHALATION Excessive inhalation Avoid breathing mist or In case of signs and symptoms of
may cause poisoning dust; use proper (exhaust) organophosphorus poisoning, remove
ventilation or proper mask from contaminated area and obtain
or ventilator medical attention immediately
INGESTION Unlikely occupational Wash hands before eating, drinking,
hazard using the toilet, and after work;
do not keep food in areas with
potential exposure
Accidental or intentional Obtain medical attention immediately;
swallowing may rapidly cause induce vomitinga if subject is
typical organophosphorus conscious; if breathing has stopped
poisoning leading to respiratory apply artificial respiration
arrest and death
HAZARD/SYMPTOM PREVENTION AND PROTECTION FIRST AID
REPEATED EXPOSURE
INGESTION, INHALATION,
SKIN: May gradually lead to Wash hands before eating, Obtain medical attention
signs, symptoms and poisoning; drinking, using the toilet, and immediately; induce vomiting
sensitization may occur after work if subject is consciousa; if
breathing has stopped, apply
artificial respiration
a Caution: if parathion is dissolved in solvents, e.g., petroleum solvents, vomiting may cause pulmonary
aspiration.
Instead, the stomach should be emptied as soon as possible by
careful gastric lavage (using a cuffed endotracheal tube already in
place). If possible, identify the solvents present in the
formulation and observe the victim for additional toxic effects. As
early as possible, administer 2 mg of atropine sulfate i.v. and
1000-2000 mg of pralidoxime chloride or 250 mg of obidoxime chloride
(adult dose) i.v. to patients suffering from severe respiratory
difficulties, convulsions, and unconsciousness. Repeated doses of
2 mg of atropine sulfate should be given, as required, based on the
respiration, blood pressure, pulse frequency, salivation, and
convulsion conditions. Diazepam should be given in all but the
mildest cases in doses of 10 mg, s.c. or i.v., which may be repeated
as required.
For children, the doses are 0.04-0.08 mg of atropine/kg body weight,
250 mg of pralidoxime chloride per child, or 4-8 mg of obidoxime
chloride/kg body weight.
Artificial respiration should be applied, if required.
Morphine, barbiturates, phenothiazine derivatives,
tranquillizers, and all kinds of central stimulants
are contraindicated.
The diagnosis of intoxication should be confirmed as soon as
possible by determination of the cholinisterase activity in venous
blood.
For more information on the treatment of organophosphorus
insecticides see EHC No. 63: Organophosphorus insecticides - a
general introduction (WHO, 1986). The section on therapy from this
publication is attached as Annex 1 of this guide.
In all cases of clinical poisoning with parathion and other
organophosphate insecticides, it is essential to maintain general
surveillance and cholinesterase and cardiac monitoring for at least
4 days, and longer if necessary, and to adopt general supportive and
specific therapy in accordance with the findings.
4.1.2 Health surveillance advice
Human beings potentially exposed to parathion should undergo
periodic health monitoring and monitoring of cholinesterase activity
in the blood. Measurement of whole blood-AChE is the most widely
adopted method for monitoring occupational exposure to
organophosphorus insecticides. However, physiological variations of
blood-ChE levels occur in healthy persons and are seen in
populations.
Depressions of AChE or ChE of 20-25% are considered diagnostic of
exposure, but not necessarily indicative of hazard. Depressions of
30-50% or more are considered indicators for the removal of an
exposed individual from further contact with pesticides until levels
return to normal. Work procedures and hygiene should also be
checked. Exposure can also be monitored by measuring the urinary
excretion of p-nitrophenol.
4.2 Safety in use
Parathion and its formulations should only be handled by
well-trained, competent and supervised personnel wearing protective
clothing. When opening a container or mixing, protective impermeable
boots, clean overalls, gloves, and respirators should be worn.
Mixing, if not mechanical, should be carried out with a paddle of
appropriate length. When spraying tall crops or during aerial
application, a respirator should be worn as well as an impermeable
hood, clothing, boots, and gloves. The applicator should avoid
working in spray mist and avoid contact with the mouth.
Particular care is needed when equipment is being washed after use.
All protective clothing should be washed immediately after use,
including the insides of gloves. Splashes must be washed immediately
from the skin or eyes with large quantities of water. Before eating,
drinking, or smoking, hands and other exposed skin should be washed.
Puncture and crush empty containers to prevent reuse.
4.3 Explosion and fire hazards
Liquid formulations may be flammable. With sufficient burning or
external heat, parathion will decompose, emitting toxic fumes.
Firefighters must wear protective clothing and self-contained
breathing apparatus. Extinguish fires with alcohol-resistant foam or
powder. Confine the use of water spray to the cooling of unaffected
stock, thus avoiding polluted run-off from the site.
4.4 Storage
Technical parathion and its formulations should be stored in
original, labelled containers in locked, well-ventilated storage
areas, preferably dedicated to insecticides. Do not expose parathion
formulations to direct sunlight. Keep products out of reach of
children and unauthorized personnel. Do not store near food or
animal feed.
4.5 Transport
Comply with any local regulations regarding the movement of
hazardous goods. Do not transport with food or animal feed. Food and
animal feed should not be transported in vehicles that have been
used for the transport of pesticides. Make sure that containers are
in good condition and labels undamaged before dispatch.
4.6 Spillage and disposal
4.6.1 Spillage
Stay upwind, wear protective equipment to avoid skin contamination
and inhalation of vapour. Absorb spilled liquid and cover
contaminated areas with a 1:3 mixture of sodium carbonate crystals
and damp sawdust, lime, sand, or earth. Sweep up and place it in a
closeable impervious container. Ensure that the container is tightly
closed and suitably labelled, before transfer to a safe place for
disposal.
Prevent liquid from spreading and contaminating other cargo,
vegetation, or waterways by constructing a barrier of the most
suitable material available, e.g., earth or sand. If the spill
occurs into a waterway and the parathion-containing material is
immiscible with water and sinks, dam the waterway to stop the flow
and to retard dissipation by water movement. Use a bottom pump,
dredging, or underwater vacuum equipment to remove undissolved
material.
Empty any of the product remaining in damaged/leaking containers
into clean empty containers, which should then be tightly closed and
suitably labelled.
Decontaminate emptied leaking containers with a 10% sodium carbonate
solution, added at the rate of at least 1 litre per 20-litre drum.
Swirl round to rinse walls, empty, and add rinsings to sawdust for
proper disposal.
4.6.2 Disposal
Contaminated absorbents, containers, surplus product, etc., should
be burnt in a proper incinerator at high temperature in a unit with
effluent gas scrubbing. When no incinerator is available, bury in an
approved dump, or in an area where there is no risk of contamination
of surface or ground water. Before burying, liberally mix with
sodium carbonate (washing soda) crystals to help neutralize the
product and mix with soil rich in organic matter. Comply with any
local legislation.
5. HAZARDS FOR THE ENVIRONMENT AND THEIR PREVENTION
With normal usage, parathion does not accumulate in organisms. It is
highly toxic for aquatic invertebrates, birds, bees, wild mammals,
fish, and soil organisms.
Avoid contamination of soil, water, and the atmosphere by proper
methods of use, storage, transport, handling, and waste disposal. In
case of spillage, use the methods advised in section 4.6.1.
6. 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 and other United Nations sources. A full reference to the
original national document from which the information was extracted
can be obtained from IRPTC.
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. Furthermore, the
regulations and guidelines of all countries are subject to change
and should always be verified with the appropriate regulatory
authorities before application.
6.1 Previous evaluations by international bodies
Parathion was evaluated by the Joint FAO/WHO Expert Committee on
Pesticide Residues (JMPR) in 1963, 1965, and 1967. In 1967, the JMPR
established an Acceptable Daily Intake (ADI) for man of 0-0.005
mg/kg body weight.
The International Agency for Research on Cancer (IARC) evaluated
parathion in 1983, and concluded that there was inadequate evidence
to evaluate the carcinogenicity of parathion for experimental
animals and that the available data were insufficient to evaluate
the carcinogenicity of parathion for humans.
WHO classified technical parathion as extremely hazardous (Class
la). WHO has issued a data sheet on parathion (No. 6).
6.2 Exposure limit values
Some exposure limit values are given in the following table.
CURRENT REGULATIONS, GUIDELINES, AND STANDARDS
Exposure limit values
Medium Specification Country/ Exposurel limit description Value Effective
organization date
AIR Workplace Argentina Maximum permissible concentration
- time-weighted average (TWA) 0.1 mg/m3 a 1979
- short-term exposure limit (STEL) 0.3 mg/m3
Germany Maximum worksite concentration (MAK)
- time-weighted average (TWA) 0.1 mg/m3 a 1986
Japan Maximum acceptable concentration 0.1 mg/m3 a 1986
United Kingdom Recommended limit (RECL)
- time-weighted average (TWA) 0.1 mg/m3 a 1985
- short-term exposure level (STEL) 0.3 mg/m3
(10-min TWA)
USA-OSHA Permissible exposure limit (PEL)
- time-weighted average (TWA) 0.1 mg/m3 a 1989
USA-ACGIH Threshold limit value (TVL)
- time-weighted average (TWA) 0.1 mg/m3 a 1990
USSR Maximum acceptable concentration
(ceiling) 0.05 mg/m3 a 1977
GENERAL Urine of Germany Maximum content of p-nitrophenol 500 µg/litre 1986
workers
Medium Specification Country/ Exposurel limit description Value Effective
organization date
FOOD Intake from FAO/WHO Acceptable daily intake (ADI) 0-0.005 mg/kg 1967
body weight
Residue FAO/WHO Maximum residue limit (MRL) 0.5-1 mg/kg 1986
products specified as follows:
- apricots, citrus fruit, peaches 1 mg/kg
- other fruit 0.5 mg/kg
- vegetables (except carrots) 0.7 mg/kg
WATER Ambient EEC Maximum acceptable concentration for
total pesticides
- for drinking-water purification 0.001-0.005 mg/litre 1977
Japan Environmental water quality standard Not detectable 1970
Mexico Maximum permissible concentration
(coastal) 0.001 mg/litre 1973
(estuarine) 0.01 mg/litre 1973
USSR Maximum acceptable concentration
(in surface water) 0.003 mg/litre 1983
a Skin absorption.
6.3 Specific restrictions
Because of its high toxicity, the use and/or sale of parathion is
non-registered, banned, or has been phased out in many countries or
territories, e.g., Belize, Bulgaria, China, Ecuador, El Salvador,
Guatemala, Hong Kong, Hungary, India, Ireland, Japan, Malaysia, New
Zealand, Philippines, Santa Lucia, Sri Lanka, Sweden, Thailand,
Turkey, the United Kingdom, and the Russian Federation. Its use has
been severely restricted in several other countries, including
Brazil, Denmark, Finland, and Norway.
In Canada, Israel, and the USA, the use, sale and application of
parathion is restricted to those licensed to do so. In Germany,
parathion may not be handled by adolescents or by pregnant women and
nursing mothers.
In the USA, field workers may not enter sprayed fields without
protective clothing until at least 48 hours after spraying.
Pre-harvest intervals have been set in many countries. These are
generally in the range of 7-15 days, but, for greenhouse use, they
may be double this time, and, for certain fruits, may last up to 5
weeks.
6.4 Labelling, packaging, and transport
Depending on the content of the active ingredient, the United
Nations Committee of Experts on the Transportation of Dangerous
Goods classifies parathion in:
Hazard Class 6.1: poisonous substance;
Packing Group I: substances and preparations presenting a
very severe risk of poisoning, when the
content of the active ingredient is
40-100%;
Packing Group II: substances and preparations presenting a
serious risk of poisoning, when the content
of active incredient is 4-40%;
Packing Group III: a substance presenting a relatively low
risk of poisoning in transport, when the
content of active ingredient is 1-4%
(solid) or 0.4-4% (liquid).
The label should be as follows:
Packaging Groups I and II
Packaging Group III
Parathion has been identified as a severe marine pollutant in the
International Maritime Dangerous Goods (IMDG) Code and a MARINE
POLLUTANT mark (see below) is required for transport by sea.
The following specifications for technical material and some
formulations (powders, dusts, concentrates, and solutions) have been
agreed between FAO and the parathion manufacturers.
All packages shall bear, durably and legibly marked on the
container, the following:
manufacturer's name
technical parathion to specification
batch or reference number, and date of test
net weight of contents
date of manufacture
and, in the case of the formulated products:
manufacturer's name
parathion to specification
parathion ... g/kg
batch or reference number, and date of test
net weight of contents
instructions for dilution
date of formulation
and the following minimum cautionary notice:
Parathion is an organophosphorus compound that inhibits
cholinesterase. It is poisonous if swallowed or inhaled. It
may be absorbed through the skin. Avoid skin contact; wear
protective gloves, clean protective clothing and a respirator
when handling the material. Wash thoroughly with soap and
water after using.
Keep the material out of the reach of children and well away from
foodstuffs and animal feed and their containers.
If poisoning occurs, call a physician. Atropine and pralidoxime are
specific antidotes, and artificial respiration may be needed.
The parathion content shall be declared (minimum 95% for the
technical product) and shall not differ from the declared percentage
by more than 2% for the technical product and 5-10 for its
formulations.
Containers shall be suitable, clean, dry, and as specified in the
order and shall not adversely affect, or be affected by, the
product, but shall adequately protect it from external conditions.
They shall comply with pertinent national and international
transport and safety regulations.
Specifications for storage stability are given.
The European Community legislation on labelling of pesticide
preparations classified parathion in Class I/a for the purpose of
determining the label for preparations containing parathion and
other active ingredients.
The European Community legislation requires labelling as dangerous
substance using the symbol:
The label must read:
Very toxic by inhalation, in contact with skin and if
swallowed; keep locked up; keep away from food, drink and
animal feeding stuffs; after contact with skin, wash
immediately with plenty of ..... (to be specified by the
manufacturer); in case of accident or if you feel unwell, seek
medical advice immediately (show the label where possible)
6.5 Waste disposal
In the USA, any non-domestic waste containing parathion and its
metabolites must be treated as hazardous waste. Specific
instructions are given for handling, transport, treatment, storage,
and incineration, as well as notification and permit requirements.
Owners/operators of vessels or onshore or offshore facilities must
notify the USA Government (National Response Center) for any release
of parathion in, or on, navigable waters, adjoining shorelines, in
the contiguous zone, or beyond the contiguous zone in an amount
equal to, or greater than, one pound (0.454 kg), in any 24-hour
period.
An owner or operator of a hazardous waste incinerator must achieve
99.99% destruction and removal efficiency for this substance.
6.6 Other measures
In the countries of the European Economic Community, parathion is
listed as a dangerous substance at quantities >100 kg in the
directive on the major accident hazards of certain industrial
activities. Any person in charge of an industrial activity
involving, or possibly involving, one or more dangerous substances
is obliged to take all the measures necessary to prevent major
accidents, to limit their consequences for man and the environment,
and to notify the competent authority about the industrial activity.
BIBLIOGRAPHY
CEC (1987) Legislation on dangerous substances - classification and
labelling in the European Communities. Vol. 1 & 2. Commission of the
European Communities, London, Graham & Trotman, Ltd.
FAO (1985a) Guidelines for the packaging and storage of pesticides.
Rome, Food and Agriculture Organization of the United Nations.
FAO (1985b) Guidelines for the disposal of waste pesticides and
pesticide containers on the farm. Rome, Food and Agriculture
Organization of the United Nations.
FAO (1985c) Guidelines on good labelling practice for pesticides.
Rome, Food and Agriculture Organization of the United Nations.
FAO (1986) International code of conduct on the distribution and use
of pesticides. Rome, Food and Agriculture Organization of the United
Nations.
FAO/WHO (1964) Evaluation of the toxicity of pesticide residues in
food. Report of a Joint Meeting of the FAO Committee on Pesticides
in Agriculture and the WHO Expert Committee on Pesticide Residues.
Geneva, World Health Organization (FAO Meeting Report. No.
PL:1963/13; WHO/Food Add./23 (1964)).
FAO/WHO (1965) Evaluation of the toxicity of pesticide residues in
food. Geneva, World Health Organization (FAO Meeting Report, No.
PL:1965/ 19/1; WHO Food Add./27.65).
FAO/WHO (1968) 1967 Evaluation of the toxicity of some pesticide
residues in food. Geneva, World Health Organization (FAO Meeting
Report, No. PL:1967/M/11/1; WHO Food Add./68.30).
FAO/WHO (1986) Codex Maximum Limits for pesticide residues. Codex
Alimentarius Commission CAC/Vol. XIII, 3rd ed. Rome, Food and
Agriculture Organization of the United Nations.
FAO/WHO (1989) Guide to Codex recommendations concerning pesticide
residues. Part 8. Recommendations for methods of analysis of
pesticide residues. 4th ed. Rome, Codex Committee on Pesticide
Residues.
GEMS (1986) Chemical contaminants in food: 1980-1983. Global
Environment Monitoring System (UNEP/FAO/WHO), World Health
Organization, Geneva, (Unpublished document WHO/EHE/FOS/86.5).
GIFAP (1982) Guidelines for the safe handling of pesticides during
their formulation, packing, storage and transport. Brussels,
Groupement International des Associations Nationales des Fabricants
de Produits Agrochimiques.
GIFAP (1983) Guidelines for the safe and effective use of
pesticides. Brussels, Groupement International des Associations
Nationales des Fabricants de Produits Agrochimiques.
GIFAP (1984) Guidelines for emergency measures in cases of pesticide
poisoning, Brussels, Groupement International des Associations
Nationales des Fabricants de Produits Agrochimiques.
GIFAP (1987) Guidelines for the safe transport of pesticides.
Brussels, Groupement International des Associations Nationales des
Fabricants de Produits Agrochimiques.
Hayes WJJ Jr & Laws, ER Jr (1991) Handbook of pesticide toxicology.
3 Vol. New York, Academic Press.
IARC (1983) IARC monographs on the evaluation of carcinogenic risk
of chemicals to man. Vol. 30. Miscellaneous chemicals. Lyon,
International Agency for Research on Cancer.
ILO (1991) Safety and health in the use of agro-chemicals - a guide.
Geneva, International Labour Office.
IPCS/CEC (1990) International Chemical Safety Card No. 6: Parathion.
Luxembourg, Commission of the European Communities.
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chemicals. Geneva, International Register of Potentially Toxic
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Plestina R (1984) Prevention, diagnosis, and treatment of
insecticide poisoning. Geneva, World Health Organization
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restricted or not approved by governments. 2nd ed. New York, United
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Council.
ANNEX 1. TREATMENT OF ORGANOPHOSPHATE INSECTICIDE POISONING
IN MANa
All cases of organophosphorus poisoning should be dealt with as an
emergency and the patient sent to hospital as quickly as possible.
Although symptoms may develop rapidly, delay in onset or a steady
increase in severity may be seen up to 48 h after ingestion of some
formulated organophosphorus insecticides.
Extensive descriptions of treatment of poisoning by organophosphorus
insecticides are given in several major references (Kagan, 1977;
Taylor, 1980; UK DHSS, 1983; Plestina, 1984) and will also be
included in the IPCS Health and Safety Guides to be prepared for
selected organophosphorus insecticides.
The treatment is based on:
(a) minimizing the absorption;
(b) general supportive treatment; and
(c) specific pharmacological treatment.
I.1 Minimizing the absorption
When dermal exposure occurs, decontamination procedures include
removal of contaminated clothes and washing of the skin with
alkaline soap or with a sodium bicarbonate solution. Particular care
should be taken in cleaning the skin area where venepuncture is
performed. Blood might be contaminated with direct-acting
organophosphorus esters and, therefore, inaccurate measures of ChE
inhibition might result. Extensive eye irrigation with water or
saline should also be performed. In the case of ingestion, vomiting
might be induced, if the patient is conscious, by the administration
of ipecacuanha syrup (10-30 ml) followed by 200 ml water. This
treatment is, however, contraindicated in the case of pesticides
dissolved in hydrocarbon solvents. Gastric lavage (with addition of
bicarbonate solution or activated charcoal) can also be performed,
particularly in unconscious patients, taking care to prevent
aspiration of fluids into the lungs (i.e., only after a tracheal
tube has been put into place).
a From EHC 63: Organophosphorus insecticides - a general
introduction. Geneva, World Heralth Organization, 1986.
The volume of fluid introduced into the stomach should be recorded
and samples of gastric lavage frozen and stored for subsequent
chemical analysis. If the formulation of the pesticide involved is
available, it should also be stored for further analysis (i.e.,
detection of toxicologically relevant impurities). A purgative can
be administered to remove the ingested compound.
I.2 General supportive treatment
Artificial respiration (via a tracheal tube) should be started at
the first sign of respiratory failure and maintained for as long as
necessary.
Cautious administration of fluids is advised, as well as general
supportive and symptomatic pharmacological treatment and absolute
rest.
I.3 Specific pharmacological treatment
I.3.1 Atropine
Atropine should be given, beginning with 2 mg iv and given at
15-30-min intervals. The dose and the frequency of atropine
treatment varies from case to case, but should maintain the patient
fully atropinized (dilated pupils, dry mouth, skin flushing, etc.).
Continuous infusion of atropine may be necessary in extreme cases
and total daily doses up to several hundred mg may be necessary
during the first few days of treatment.
I.3.2 Oxime reactivators
Cholinesterase reactivators (e.g., pralidoxime, obidoxime)
specifically restore AChE activity inhibited by organophosphates.
This is not the case with enzymes inhibited by carbamates. The
treatment should begin as soon as possible, because oximes are not
effective on "aged" phosphorylated ChEs. However, if absorption,
distribution, and metabolism are thought to be delayed for any
reasons, oximes can be administered for several days after
intoxication. Effective treatment with oximes reduces the required
dose of atropine. Pralidoxime is the most widely available oxime. A
dose of 1 g pralidoxime can be given either im or iv and repeated
2-3 times per day or, in extreme cases, more often. If possible,
blood samples should be taken for AChE determinations before and
during treatment. Skin should be carefully cleansed before sampling.
Results of the assays should influence the decision whether to
continue oxime therapy after the first 2 days.
There are indications that oxime therapy may possibly have
beneficial effects on CNS-derived symptoms.
I.3.3 Diazepam
Diazepam should be included in the therapy of all but the mildest
cases. Besides relieving anxiety, it appears to counteract some
aspects of CNS-derived symptoms that are not affected by atropine.
Doses of 10 mg sc or iv are appropriate and may be repeated as
required (Vale & Scott, 1974). Other centrally acting drugs and
drugs that may depress respiration are not recommended in the
absence of artificial respiration procedures.
I.3.4 Notes on the recommended treatment
I.3.4.1 Effects of atropine and oxime
The combined effect far exceeds the benefit of either drug singly.
I.3.4.2 Response to atropine
The response of the eye pupil may be unreliable in cases of
organophosphorus poisoning. A flushed skin and drying of secretions
are the best guide to the effectiveness of atropinization. Although
repeated dosing may well be necessary, excessive doses at any one
time may cause toxic side-effects. Pulse-rate should not exceed
120/min.
I.3.4.3 Persistence of treatment
Some organophosphorus pesticides are very lipophilic and may be
taken into, and then released from, fat depots over a period of many
days. It is therefore quite incorrect to abandon oxime treatment
after 1-2 days on the supposition that all inhibited enzyme will be
aged. Ecobichon et al. (1977) noted prompt improvement in both
condition and blood-ChEs in response to pralidoxime given on the
11th-15th days after major symptoms of poisoning appeared due to
extended exposure to fenitrothion (a dimethyl phosphate with a short
half-life for aging of inhibited AChE).
I.3.4.4 Dosage of atropine and oxime
The recommended doses above pertain to exposures, usually for an
occupational setting, but, in the case of very severe exposure or
massive ingestion (accidental or deliberate), the therapeutic doses
may be extended considerably. Warriner et al. (1977) reported the
case of a patient who drank a large quantity of dicrotophos, in
error, while drunk. Therapeutic dosages were progressively increased
up to 6 mg atropine iv every 15 min together with continuous iv
infusion of pralidoxime chloride at 0.5 g/h for 72 h, from days 3 to
6 after intoxication. After considerable improvement, the patient
relapsed and further aggressive therapy was given at a declining
rate from days 10 to 16 (atropine) and to day 23 (oxime),
respectively. In total, 92 g of pralidoxime chloride and 3912 mg of
atropine were given and the patient was discharged on the
thirty-third day with no apparent sequelae.
References to Annex 1
Ecobichon DJ, Ozere RL, Reid E, & Crocker JFS (1977) Acute
fenitrothion poisoning. Can Med Assoc J, 116: 377-379.
Kagan JuS (1977) [Toxicology of organophosphorus pesticides],
Moscow, Meditsina, pp. 111-121, 219-233, 260-269 (in Russian).
Plestina R (1984) Prevention, diagnosis, and treatment of
insecticide poisoning, Geneva, World Health Organization
(Unpublished document VBC/84.889).
Taylor P (1980) Anticholinesterase agents. In: Goodman LS & Gilman
A, ed. The pharmacological basis of therapeutics, 6th ed., New York,
Macmillan Publishing Company, pp. 100-119.
UK DHSS (1983) Pesticide poisoning: notes for the guidance of
medical practitioners, London, United Kingdom Department of Health
and Social Security, pp. 41-47.
Vale, J.A. & SCOTT, G.W. (1974) Organophosphorus poisoning. Guy's
Hosp. Rep., 123: 13-25.
Warriner RA III, Nies AS, & Hayes WJ Jr (1977) Severe
organophosphate poisoning complicated by alcohol and turpentine
ingestion. Arch environ Health, 32: 203-205.