WORLD HEALTH ORGANIZATION FOOD AND AGRICULTURE
ORGANIZATION
ORGANISATION MONDIALE DE LA SANTE ORGANISATION POUR L'ALIMENTATION
ET L'AGRICULTURE
VBC/DS/75.18
ORIGINAL: ENGLISH
DATA SHEETS ON PESTICIDES No. 18
July 1975
CHLORPYRIFOS
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 Ce document ne constitue pas une
not constitute formal publication. Il ne doit faire
publication. It should not be l'objet d'aucun compte rendu ou
reviewed, abstracted or quoted résumé ni d'aucune citation sans
without the agreement of the l'autorisation de l'Organisation
Food and Agriculture des Nations Unies pour
Organization of the United l'Alimentation et l'Agriculture
Nations or of the World Health ou de l'Organisation Mondiale de
Organization. la Santé.
Part 1 - General information
CLASSIFICATION
Primary use: insecticide
Secondary use: acaricide
Chemical group: organophosphorus compound
Data Sheet No. 18
Date issued: July 1975
1.1 COMMON NAME:
chlorpyrifos (proposed ISO common name).
Identity: 0,0-diethyl 0-(3,5,6-trichloro-2-pyridyl)
phosphorothioate
Synonyms Local Synonyms
DURSBAN (R)
LORSBAN(R)
DOWCO(R)
ENT 27311
OMS 971
1.2 SYNOPSIS
An organophosphorus pesticide of moderate mammalian toxicity which
is active against a wide variety of agricultural and public health
arthropod pests.
1.3 SELECTED PROPERTIES
1.3.1 Physical characteristics:
A white granular crystalline solid with a mild mercaptan-like odour
mp 42-43.5°C.
1.3.2 Solubility:
Water at 25% practically insoluble (2 ppm.), soluble in most organic
solvents (e.g. methyl alcohol, 45%, iso-octane, 79%).
1.3.3 Stability:
Stable under normal storage conditions. Half-life in aqueous
methanolic solution 1930 days at pH 6.0; 7.2 days at pH 9.96.
Hydrolysed by water with similar dependence on pH. Decomposition is
rapid above pH 8.0. Compatible with non-alkaline pesticides.
Corrosive to copper and brass.
1.3.4 Vapour pressure (volatility):
1.87 x 10-5 mm Hg at 25°C.
1.4 AGRICULTURE, HORTICULTURE AND FORESTRY
1.4.1 Common formulations
Wettable powder, 25%; emulsifiable concentrates, 25 and 50%;
granules, 1-10%.
1.4.2 Pests mainly controlled
Broad spectrum insecticide and acaricide. Active against mosquitos
(larvae and adults), soil and household pests, ectoparasites of
cattle, sheep and poultry, foliar and fruit feeding pests of various
field, tree fruit and vegetable crops.
1.4.3 Use pattern
Used as dip or spray to control ticks, lice and horseflies on beef
and non-lactating dairy cattle, and blowflies, ticks, lice and keds
on sheep.
Used as a soil spray in turkey pens, before the turkeys are penned,
to control chiggers.
Used as pre- and post-planting soil treatment to control insects
attacking maize, spring cereals, beans, onions, carrots, turnips,
lettuce, bulb flowers and tobacco.
Used as foliar treatment against insect pests of rape, cereals,
potatoes, fodder crops, legumes, brassicas, rice, cotton, tobacco
and deciduous fruits, and as a spray on lawns.
Used on agricultural and household premises.
Chlorpyrifos has a short residual life on plant foliage, but is
effective for several weeks on soil, polluted water, wood, concrete,
etc. Very resistant to leaching from soils.
1.4.4 Unintended effects
Toxic to shrimps, crabs, and fish. Not phytotoxic at concentrations
recommended for use. Its persistence in soil (1-2 months) and on
various surfaces, although not hazardous in itself, could lead to
undesirable effects by accumulation, depending on the frequency of
applications and amount applied.
1.5 PUBLIC HEALTH PROGRAMS
Widely used in mosquito control, mainly as a larvicide. Also used as
ULV concentrate for control of adult mosquitos as space spray.
1.6 HOUSEHOLD USE
Used for control of most common household insects, particularly
cockroaches.
Part 2 - Toxicology and risks
2.1 TOXICOLOGY - MAMMALS
2.1.1 Absorption route:
Absorbed from the gastrointestinal tract and to a lesser extent
through the intact skin and by inhalation.
2.1.2 Mode of action:
cholinsterase inhibition.
2.1.3 Excretion products:
The main excretion products which occur largely in the urine and to
a lesser extent in the faeces are: 3,5,6-trichloro-2-pyridyl
phosphate, 3,5,6-trichloro-2-pyridinol and traces of unchanged
chlorpyrifos.
2.1.4 Toxicity, single dose
Oral: LD50 rat (M) 155 mg/kg Dermal: LD50 rat (M) 202 mg/kg
rat (F) 135 mg/kg
Dermal: LD50 rabbit 2000 mg/kg
2.1.5 Toxicity, repeated doses
Oral: There was no inhibition of plasma or erythrocyte
cholinesterase when dogs were given 0.01 mg/kg daily by capsule for
32 days. At 0.03 mg/kg for 90 days, there was marginal reduction of
cholinesterase activity. At 0.1, 0.3 and 1 mg/kg for 90 days, there
was significant decrease in plasma and erythrocyte cholinesterase
activity, but there were no other abnormalities. Recovery of both
plasma and erythrocyte cholinesterase occurred within 14 days after
discontinuing feeding the compound.
Rhesus monkeys received 0.08, 0.4 or 2.0 mg/kg of chlorpyrifos by
gavage daily for six months. There were no abnormalities except
decrease in erythrocyte and plasma cholinesterase activity at 0.4
and 2.0 mg/kg and a slight decrease only in plasma cholinesterase
activity at 0.08 mg/kg.
Inhalation: Rats exposed for 7 h/day to an atmosphere of
chlorpyrifos (0.007 g/m3 air) for 16 exposures over a 21 day
interval, showed no effects on growth, appearance, behaviour or
plasma and erythrocyte cholinesterase activity.
Dermal: Rabbits were exposed dermally to it varying schedule of
dosages and number of exposures. At both ends of the schedule,
5 mg/kg applied for 12 h on 20 occasions and 50 mg/kg applied for
12 h once only, significant: plasma and erythrocyte cholinesterase
inhibition occurred without any other abnormalities.
Cumulation of compound: There is some persistence of chlorpyrifos
in fatty tissues, the half-life being about 62 h.
2.1.6 Dietary studies
Short-term: In a 90-day feeding study with rats, cholinesterase
inhibition in plasma and erythrocytes was evident at dietary levels
of 10 ppm (0.5 mg/kg/day) and above. No symptoms of toxicity were,
however, evident at 100 ppm (5 mg/kg/day) and below. At 300 ppm and
1000 pp (15 and 50 mg/kg/day) there were marked cholinergic symptoms
with high mortality at the top dose level. In another 90-day study,
the no-effect level with respect to cholinesterase inhibition was a
dietary level equivalent to 0.1 mg/kg per day.
Gross cholinergic effects were evident in dogs fed 600 and 200 ppm
(15 and 5 mg/kg/day) for 16 and 45 days respectively. At 60 and 20
ppm (1.5 and 0.5 mg/kg/day) for 88 and 77 days respectively,
retardation in growth and reduction of cholinesterase activity were
the only abnormalities.
Long-term: Groups of dogs were fed chlorpyrifos in the diet for
up to two years at dose levels of 0, 6.01, 0.03, 0.1, 1.0 and
3.0 mg/kg/day. Inhibition of erythrocyte cholinesterase in males and
females was evident at 1.0 and 3.0 mg/kg. Marginal reduction in
brain cholinesterase activity was shown at the highest level of
feeding. Plasma cholinesterase was inhibited at 0.1 mg/kg/day in
both males and females. Occasional reduction at 0.03 mg/kg was
noted. Gross examination showed an increase in liver weight and
ratio at 3.0 mg/kg. All other tissues were normal. Inhibition of
cholinesterase activity was the only abnormality detected.
Groups of rats were fed dietary levels of chlorpyrifos of 0, 0.01,
0.03, 0.1, 1.0 and 3.0 mg/kg/day for two years. Blood cholinesterase
activity primarily in plasma was reduced in females at 0.1. mg/kg
and above. Brain cholinesterase was inhibited at 3.0 mg/kg and
slightly reduced at 1.0 mg/kg. Chlorpyrifos at all dosage levels had
no significant effect on behaviour, appearance, growth, mortality,
haematology, urinalysis, clinical biochemistry, gross or
histopathology of tissues and organs or the incidence of neoplasms.
2.1.7 Supplementary studies of toxicity
Reproduction and teratogenicity
In a three generation reproduction study, prolonged exposure to
dietary levels up to and including 1.0 mg/kg/day had no Adverse
effect on the reproductive capacity of either sex. No terata were
observed in the offspring of rats orally administered 1.0 mg/kg/day
on days 6-15 of gestation.
Delayed neurotoxicity
A maximum dose of 150 mg/kg of chlorpyrifos has been administered
orally to hens which were protected by pralidoxime. Surviving birds
did not display delayed ataxia or paralysis.
Studies on the metabolite 3,5,6-trichloro-2-pyridinol
Oral LD50 rat (M) 794 mg/kg
rat (F) 870 mg/kg
Studies in rats and dogs reveal that the no-effect level for the
metabolite 3,5,6-trichloro-2-pyridinol is 1000 ppm. in the diet of
rats (50 mg/kg/day) and 400 ppm in the diet of dogs (10 mg/kg/day).
Levels up to 1000 ppm of 3,5,6-trichloro-2-pyridinol for three weeks
did not produce mortality or cataracts in ducklings,
2.1.8 Modification of toxicity
Antidotes
The toxicity of chlorpyrifos was significantly moderated in rats by
treatment with atropine sulfate either alone or in combination with
pralidoxime. The following gives the LD50 values following
subcutaneous injection:
Chlorpyrifos (alone) 147 mg/kg
Chlorpyrifos (+ atropine sulfate - 17.4 mg/kg) 205 mg/kg
Chlorpyrifos (+ atropine sulfate - 17.4 mg/kg
+ pralidoxime 50 mg/kg) 540 mg/kg
2.2 TOXICOLOGY - MAN
2.2.1 Dangerous doses
Single: Not known.
Repeated: Not known.
2.2.2 Observations of occupationally exposed workers
Three studies have been conducted on spraymen applying chlorpyrifos
in public health programme. In all studies reduced cholinesterase
activity was recorded. In one study five of seven spraymen showed
more than 50% reduction of plasma cholinesterase activity within two
weeks after the beginning of the spraying. No clinical
manifestations of organophosphorus poisoning were noted in any of
the spraymen; no inhibition of erythrocyte cholinesterase activity
was observed at any time.
2.2.3 Observations on exposure of the general population
No information.
2.2.4 Observations on volunteers
In human volunteers given daily oral doses of 0, (control), 0.014,
0.03 or 0.1 mg/kg of chlorpyrifos, the threshold level for reduction
of plasma or cholinesterase activity was judged to be 0.03 mg/kg/day
given for 21 days. Recovery in the 0 10 mg/kg group on withdrawal of
chlorpyrifos was complete within four weeks. No changes in
erythrocyte cholinesterase were seen for any dose level given. Other
blood tests and results of urinalysis were normal. Neither
chlorpyrifos nor its oxygen analogue nor the metabolite
3,5,6-trichloro-2-pyridinol were detectable in the urine.
An adult male human volunteer exposed by inhalation to chlorpyrifos
1.1 mg/m3 for 8 min, showed no reduction of plasma or erythrocyte
cholinesterase levels at 4, 22 and 70 h after treatment. Human
volunteers of both sexes similarly exposed to lower concentrations
of chlorpyrifos for shorter periods showed no cholinesterase
inhibition.
Adult human volunteers exposed dermally to chlorpyrifos at doses of
1.0, 1.5, 3.0, 5.0 and 7.5 mg/kg body weight for 12 h displayed no
evidence of reduction in plasma or erythrocyte cholinesterase
levels.
2.2.5 Reported mishaps
No information.
2.3 TOXICITY TO NON-MAMMALIAN SPECIES
The entries in these sections are intended to draw attention to
special risks and to give warnings of any needs for special
precautions.
2.3.1 Fish
Toxic to fish.
2.3.2 Birds
Toxicity to birds varies between and within species: it is generally
fairly high, with LD50 below 50 mg/kg for several species. Shows
some degree of cumulative toxicity.
2.3.3 Other species
Toxic to shrimps, crabs and other aquatic invertebrates.
Part 3 - For regulatory authorities
RECOMMENDATIONS ON REGULATION OF COMPOUND
see introduction)">3.1 RECOMMENDED RESTRICTIONS ON AVAILABILITY (for definition
of categories, see introduction)
Liquid formulations over 50%, category 3 and over 5%, category 4.
Solid formulations over 20%, category 4, all other formulations,
category 5.
see introduction)">3.2 TRANSPORTATION AND STORAGE
All formulations in categories 3 and 4
Should be transported or stored in clearly labelled rigid and
leakproof containers under lock and key safe from access by
unauthorized persons and children. No food or drink should be stored
in the same compartment.
Formulations in category 5
Should be stored in clearly labelled leakproof containers, out of
reach of children and away from food and drink.
3.3 HANDLING
All formulations in categories 3 and 4
Protective clothing (see 4.1.3 - Part 4) should be used by those
handling the compound. Adequate washing facilities should be
available at all times during handling and should be close to the
site of the handling. Eating, drinking and smoking should be
prohibited during handling and before washing after handling.
Formulations in category 5
No facilities other than those needed for handling of any chemical
need to be required.
3.4 DISPOSAL AND/OR DECONTAMINATION OF CONTAINERS
All formulations
Container may be decontaminated (for method, see para. 4.3 - Part
4). Decontaminated containers should not be used for food and drink.
Containers that are not decontaminated should be burned or should be
crushed and buried below topsoil. Care must be taken to avoid
subsequent contamination of water sources.
3.5 SELECTION, TRAINING AND MEDICAL SUPERVISION OF WORKERS
All formulations, categories 3 and 4
Pre-employment medical examination for workers desirable. Workers
suffering from active hepatic or renal disease should be excluded
from contact. Pre-employment and periodic cholinesterase test for
workers desirable. Special account should be taken of the workers'
mental ability to comprehend and follow instructions. Training of
workers in techniques to avoid contact essential.
Formulations, category 5
No special cholinesterase test for workers necessary. Warning of
workers to minimize contact essential.
3.6 ADDITIONAL REGULATIONS RECOMMENDED IF DISTRIBUTED BY AIRCRAFT
All formulations
Pilot and loaders should have special training in application
methods and early symptoms of poisoning, and must wear a suitable
respirator. Flagmen, if used, should wear overalls and be located
well away from the dropping zone.
3.7 LABELLING
All formulations, categories 3 and 4
"Chlorpyrifos is an organophosohorus compound which inhibits
cholinesterase. It is poisonous if swallowed. 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 reach of children and well away from foodstuffs, animal feed
and their containers."
"If poisoning occurs, call a physician. Atropine and pralidoxime are
specific antidotes and artificial respiration may be needed."
All formulations, category 5
"This formulation contains chlorpyrifos which is a toxic substance.
Keep the material out of reach of children and well away from
foodstuffs, animal feed and their containers."
3.8 RESIDUES IN FOOD
3.8.1 Maximum residue levels
"The Joint FAO/WHO Meeting on Pesticide Residues (1972) has
recommended the following limits:
Fat of meat of cattle 2.0 ppm
Apples, chinese cabbage, grapes, kale 1.0 ppm
Pears, carrots, tomatoes 0.5 ppm
Beans, aubergines, peppers, raspberries 0.2 ppm
Fat of meat of sheep and of poultry 0.2 ppm.
Lettuce, sugarbeet, rice (in husk) 0.1 ppm
Celery, cottonseed, cottonseed oil (crude),
mushrooms, onions 0.05 ppm
Cauliflower, red cabbage, potatoes 0.01 ppm
Milk (fat basis) 0.01 ppm
Part 4 - Prevention of poisoning in man and emergency aid
4.1 PRECAUTIONS IN USE
4.1.1 General
Chlorpyrifos is an organophosphorus pesticide of moderate toxicity.
It is readily absorbed by the gastrointestinal tract and may also be
absorbed through the intact skin and by inhalation.
4.1.2 Manufacture and formulation
A TLV value of 0.2 mg/m3 has been proposed (A.C.G.I.H.).
Closed systems of forced ventilation may be required to reduce as
much as possible the exposure of workers to the chemical.
4.1.3 Mixers and applicators
When opening the container and when mixing, protective impermeable
boots, clean overalls, gloves and respirator should be worn. Mixing,
if not mechanical, should always be carried out with a paddle of
appropriate length. When spraying tall crops or during aerial
application, a face mask 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 the 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.
4.1.4 Other associated workers (including flagmen in aerial
operations)
Persons exposed to chlorpyrifos and associated with its application
should wear protective clothing and observe the precautions
described above in 4.1.3 under "Mixers and applicators".
4.1.5 Other populations likely to be affected
With correct use in agriculture and public health, other persons
should not be exposed to hazardous amounts of chlorpyrifos.
4.2 ENTRY OF PERSONS INTO TREATED AREAS
Unprotected persons should be kept out of treated areas for 12 h.
4.3 DECONTAMINATION OF SPILLAGE AND CONTAINERS
Residues in containers should be emptied in a diluted form into a
deep pit taking care to avoid ground waters. The empty container
may be decontaminated by rinsing two or three times with water and
scrubbing the sides. An additional rinse should be carried out with
5% sodium hydroxide solution which should remain in the container
overnight. Impermeable gauntlets should be worn during this work and
a soakage pit should be provided for the rinsings. Decontaminated
containers should not be used for food and drink.
Spillage of chlorpyrifos and its formulations should be removed by
washing with 5% sodium hydroxide solution and then rinsing with
large quantities of water.
4.4 EMERGENCY AID
4.4.1 Early symptoms of poisoning
Early symptoms of poisoning may include excessive sweating,
headache, weakness, giddiness, nausea, vomiting, stomach pains,
blurred vision, slurred speech, and muscle twitching. Later there
may be convulsions, coma, loss of reflexes and loss of sphincter
control.
4.4.2 Treatment before person is seen by a physician, if these
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 quantities of water. If
swallowed, vomiting should be induced if the person is conscious. In
the event of collapse, artificial respiration should be given,
bearing in mind that if mouth-to-mouth respiration is used, vomit
may contain toxic amounts of chlorpyrifos.
Part 5 - For medical and laboratory personnel
5.1 MEDICAL DIAGNOSIS AND TREATMENT OF CASES OF POISONING
5.1.1 General information
Chlorpyrifos is an organophosphorus pesticide of moderate toxicity
which is active against a variety of agricultural and public health
arthropod pests. It is readily absorbed by the gastrointestinal
tract and may also be absorbed through the intact skin and by
inhalation. Although rapidly excreted, largely in the urine, there
is some persistence of the unchanged compound in fatty tissues.
5.1.2 Symptoms and signs
Initial symptoms of poisoning may include excessive sweating,
headache, weakness, giddiness, nausea, vomiting, stomach pains,
blurred vision, slurred speech and muscle twitching. More advanced
symptoms of poisoning may be convulsions, coma, loss of reflexes and
loss of sphincter control.
5.1.3 Laboratory
The most important laboratory finding is reduction in activity of
blood cholinesterases. Urinary levels of ether-extractable
phosphorus containing compounds may also be used as an index of
exposure. Neither of these methods is specific for chlorpyrifos.
Urinary levels of 3,5,6-trichloro-2-pyridinol should also be able to
be used as an index of exposure to chlorpyrifos and related
compounds.
5.1.4 Treatment
If the pesticide has been ingested, unless the patient is vomiting,
rapid gastric lavage should be performed using 5% sodium
bicarbonate, if available. For skin contact, the skin should be
washed with soap and water. If the compound has entered the eyes,
they should be washed with isotonic saline or water.
Persons without signs of respiratory inefficiency but with manifest
peripheral symptoms should be treated with 2-4 mg of atropine
sulfate and 1000-2000 mg of pralidoxime chloride or 250 mg of
toxogonin (adult dose) by slow intravenous injection. More atropine
may be given as needed. Persons with severe intoxication, with
respiratory difficulties, convulsions and unconsciousness, should
immediately be given atropine and a reactivator. In such severe
cases, 4-6 mg of atropine sulfate should be given initially followed
by repeated doses of 2 mg at 5-1.0 min intervals. The patients'
condition, including respiration, convulsions, blood pressure, pulse
frequency, salivation and convulsions, should be carefully observed
as a guide to further administration of atropine. If the patient
is cyanotic, artificial respiration should be given first, then
atropine sulfate.
The airways should be kept free and artificial respiration should be
applied, if required, preferably by mechanical means. If necessary,
intubation should be performed.
Contraindications are morphine, barbiturates, phenothiazine
tranquillizers and central stimulants of all kinds.
5.1.5 Prognosis
Although there have been reports of reduced cholinesterase activity,
there have been no reports of overt symptoms resulting from
poisoning of man by chlorpyrifos. For this reason, the prognosis is
not known. However, by analogy with other organophosphorus
compounds, it may be assumed that if the acute toxic effect is
survived the chances of complete recovery are good. In very severe
cases, it is possible that without adequate artificial respiration,
prolonged anoxia could give rise to permanent brain damage.
5.1.6 References of previously reported cases
None.
5.2 SURVEILLANCE TESTS
Test Normal level Hazard level* Symptomatic level*
Plasma
cholinesterase 100%* 50% variable
Erythrocyte
cholinesterase 100% 70% usually <40%
*Expressed as percentage of pre-exposure activity.
Urinary levels of ether-extractable organic phosphorus should also
be able to be used to determine degrees of exposure.
5.3 LABORATORY METHODS
References are given only.
5.3.1 Detection and assay of compound
Methods for determining chlorpyrifos in plant and animal tissues and
milk have been extensively reviewed by FAO/WHO (1973). The review
includes suitable clean-up procedures and recommends
gas-chromatographic methods as being suitable for regulatory
purposes. The multi-residue method of Abbott et al. (1970) would
also probably be satisfactory, but has not yet been fully
established for chlorpyrifos.
5.3.2 Other tests in cases of poisoning
Levels of cholinesterase in the blood, particularly plasma, provide
the most useful diagnosis of poisoning:
Michel, N. O. (1949) J. Lab. Clin. Med., 34, 1564-1568
Ellman, G. L., Courtney, K. D., Andres, V., Jr & Featherstone,
R. M. (1961) Biochem. Pharmacol., 7, 88-95
Levels of diethyl phosphate and phosphorothioate in urine may also
be determined in order to give an indication of the extent of
exposure (see Shafik & Enos, 1969; Shafik et al., 1970). Unchanged
chlorpyrifos might be detectable in the blood in cases of poisoning:
the gas-chromatographic method of Machin et al. (1973) should be
adaptable to chlorpyrifos.
REFERENCES
Abbott, D. C., Crisp, S., Tarrant, K. R. & Tatton, J. O'G.
Pesticide Residues in the Total Diet in England and Wales,
1966-1967. III. Organophosphorus Pesticide Residues in the Total
Diet. Pestic. Sci., 1970, 1, 10
FAO/WHO
1972 Evaluations of some pesticide residues in food. FAO/AGP:
1972/M/9/1; WHO/1973, p. 190
Shafik, M. T. & Enos, H. F.
Determination of Metabolic and Hydrolytic Products of
Organophosphorus Pesticide Chemicals in Human Blood and Urine.
J. Agric. Fd Chem., 1969, 17, 1186
Shafik, M. T., Bradway, D., Biros, F. J. & Enos, H. F.
Characterization of Alkylation Products of Diethyl Phosphorothioate.
J. Agric. Fd Chem., 1970, 18, 1174
Machin, A. F., Quick, M. P. & Waddell, D. F.
The Rapid Determination of the Organophosphorus Pesticides Diazinon
and Dichlorvos in Blood by Gas Chromatography. Analyst, 1973,
98, 176