Ethion
Ethion
adalah racun serangga dari jenis organophosphate. Pendedahan Ethion kepada
manusia boleh berlaku melalui makanan, sedutan nafas mahupun hanya dengan
sentuhan kulit kepada tanah yang telah tercemar dengan racun ini. Ethion
bersifat racun kepada saraf (Neurotoxin - inhibits cholinesterase enzyme).
Ethion
boleh menyebabkan sakit kepala, pandangan kabur, mata berair, air liur meleleh
dengan berlebihan, kencing dalam seluar, selsema, pening, keliru, lemah anggota
badan, ketar, loya, cirit birit, dan rentak jantung caca marba. Kesan jangka
panjang Ethion boleh sebabkan lemah anggota badan, hilang selera makan dan rasa
letih yang keterlaluan.
Malangnya,
Ethion telah ada digunakan bagi menyembur racun serangga ke atas permukaan buah
buahan. Mungkinkah buah seperti cili, buah limau dll dicemari dengan racun Ethion?
TRADE OR OTHER
NAMES
Trade
names include Ethanox, Ethiol, Hylemox, Nialate, Rhodiacide, Rhodocide, RP-Thion,
Tafethion, Vegfru Fosmite.
INTRODUCTION
Ethion
is an organophosphate pesticide used to kill aphids, mites, scales, thrips,
leafhoppers, maggots and foliar feeding larvae. It may be used on a wide
variety of food, fiber and ornamental crops, including greenhouse crops, lawns
and turf. Ethion is often used on citrus and apples (1,
5).
It is mixed with oil and sprayed on dormant trees to kill eggs and scales.
Ethion may also be used on cattle. It is available in dust, emulsifiable
concentrate, emulsifiable solution, granular and wettable powder formulations.
Products containing ethion must bear the signal word "Warning" (2).
EPA has established re-entry intervals of from 2 to 30 days, depending on the
crop, for ethion (8).
Ethion is one of a class of insecticides
referred to as organophosphates. These chemicals act by interfering with the
activities of cholinesterase, an enzyme that is essential for the proper
working of the nervous systems of both humans and insects. Please refer to the
Toxicology Information Brief on cholinesterase-inhibition for a more detailed
description of this topic.
TOXICOLOGICAL
EFFECTS
ACUTE TOXICITY
Ethion
is highly toxic by inhalation, dermal exposure, and ingestion. Like most
organophosphates, ethion is readily absorbed through the skin. Skin which has
come in contact with this material should be washed immediately with soap and
water and all contaminated clothing should be removed. It may cause contact
burns (11).
Ethion is almost non-volatile at normal temperatures, but when it is used as a
spray, it is easily inhaled (14).
If ethion is inhaled, runny nose and a sensation of tightness in the chest are
common complaints(12).
Persons with respiratory ailments, recent exposure to cholinesterase
inhibitors, impaired cholinesterase production, or with liver malfunction may
be at increased risk from exposure to ethion. High environmental temperatures
or exposure of ethion to visible or UV light may enhance its toxicity (6).
Ethion may be very irritating to the eye. It
caused slight inflammation and redness in the eye and skin, both of which
cleared within 48 hours. Ethion is not a skin sensitizer (8).
The organophosphate insecticides are
cholinesterase inhibitors. They are highly toxic by all routes of exposure.
When inhaled, the first effects are usually respiratory and may include bloody
or runny nose, coughing, chest discomfort, difficult or short breath, and
wheezing due to constriction or excess fluid in the bronchial tubes. Skin
contact with organophosphates may cause localized sweating and involuntary
muscle contractions. Eye contact will cause pain, bleeding, tears, pupil
constriction, and blurred vision. Following exposure by any route, other
systemic effects may begin within a few minutes or be delayed for up to 12
hours. These may include pallor, nausea, vomiting, diarrhea, abdominal cramps,
headache, dizziness, eye pain, blurred vision, constriction or dilation of the
eye pupils, tears, salivation, sweating, and confusion. Severe poisoning will
affect the central nervous system, producing incoordination, slurred speech,
loss of reflexes, weakness, fatigue, involuntary muscle contractions,
twitching, tremors of the tongue or eyelids, and eventually paralysis of the
body extremities and the respiratory muscles. In severe cases there may also be
involuntary defecation or urination, psychosis, irregular heart beats,
unconsciousness, convulsions and coma. Death may be caused by respiratory
failure or cardiac arrest (6).
Some organophosphates may cause delayed
symptoms beginning 1 to 4 weeks after an acute exposure which may or may not
have produced immediate symptoms. In such cases, numbness, tingling, weakness
and cramping may appear in the lower limbs and progress to incoordination and
paralysis. Improvement may occur over months or years, but some residual
impairment will remain (6).
The amount of a chemical that is lethal to
one-half (50%) of experimental animals fed the material is referred to as its
acute oral lethal dose fifty, or LD50. The oral LD50 for pure ethion in rats is
208 mg/kg. The oral LD50 for technical ethion in rats is 13 to 191 mg/kg, and
40 mg/kg in mice and guinea pigs (2,
6).
The dermal LD50 in rats is 62 mg/kg, 915 mg/kg in guinea pigs, and 890 mg/kg in
rabbits (6).
The lethal concentration fifty, or LC50, is
that concentration of a chemical in air or water that kills half of the
experimental animals exposed to it for a set time period. The 4-hour LC50 for
ethion in rats is 0.864 mg/l (2).
CHRONIC
TOXICITY
In a
chronic toxicity study with rats fed 0, 0.1, 0.2 or 2 mg/kg/day for 18 months,
decreased cholinesterase levels occurred in the high dose group. No other toxic
effects were observed. The NOEL for this study was 0.2 mg/kg (9).
Repeated or prolonged exposure to
organophosphates may result in the same effects as acute exposure including the
delayed symptoms. Other effects reported in workers repeatedly exposed include
impaired memory and concentration, disorientation, severe depressions,
irritability, confusion, headache, speech difficulties, delayed reaction times,
nightmares, sleepwalking and drowsiness or insomnia. An influenza-like
condition with headache, nausea, weakness, loss of appetite, and malaise has
also been reported (6).
Reproductive
Effects
A
3-generation reproduction study with rats given dietary doses as high as 1.25
mg/kg/day did not show any ethion related reproductive effects (8,
9).
Once in the bloodstream, ethion may cross the placenta (6).
Teratogenic Effects
When
rats were given doses of 0, 0.2, 0.6 or 2.5 mg/kg on days 6 to 15 of pregnancy,
developmental effects were seen only in the highest dose tested. In fetuses of
the high dose group, there was an increased incidence of delayed ossification
of the pubic bones. The developmental NOEL in this study was 0.6 mg/kg. When
rabbits were given doses of 0, 0.6, 2.4 or 9.6 mg/kg on days 6 to 18 of
pregnancy, fetuses from the highest dose tested exhibited an increased
incidence of fused sternal bones. The developmental NOEL in this study was 2.4
mg/kg (9).
Mutagenic Effects
Assays
on gene mutation, structural chromosomal aberration, and unscheduled DNA
synthesis indicate that ethion is not mutagenic (8,
9).
Carcinogenic Effects
Ethion
was not found to be carcinogenic in rats and mice (8).
There was no increase in the incidence of tumors in rats fed dietary doses as
high as 2 mg/kg/day for 18 months. No evidence of carcinogenicity was observed
in mice fed dietary doses of up to 1.2 mg/kg/day for 2 years (9).
Organ Toxicity
Ethion
primarily affects the nervous system through cholinesterase inhibition, by
which there is a deactivation of cholinesterase, an enzyme required for proper
nerve functioning.
Fate in Humans and Animals
The
literature reviewed is not specific, but ethion is probably degraded in the
same general way as other organophosphates.
ECOLOGICAL
EFFECTS
Effects on Birds
Ethion
is highly toxic to practically non-toxic to birds, depending on the species.
Ethion is highly toxic to songbirds (LD50 in Red-winged blackbirds is 45
mg/kg). It is moderately toxic to medium sized birds such as bobwhite quail
(LD50 is 128.8 mg/kg) and starlings (>304 mg/kg). Ethion is practically
non-toxic to larger upland game birds (ring-necked pheasant) and waterfowl
(mallard duck) (9).
Because ethion is persistent in the
environment and because it is stored in plant and animal tissues, EPA is
concerned that ethion may adversely affect bird reproduction. EPA has called
for studies on the effects of ethion on bird reproduction (9).
Effects on Aquatic Organisms
Ethion
is very highly toxic to freshwater and marine fish and to freshwater
invertebrates (7,
8).
The 96-hour LC50 for ethion in rainbow trout is 500 ug/l (2).
The acute LC50 in Atlantic silversides is 49 ppb, 49 ppb in bluegill sunfish,
and in 720 ppb cutthroat trout and flathead minnows. The LD50 for freshwater
invertebrates is 0.056 to 7.7 ppb, depending on the species, and 5.6 to 49 ppb
for marine and estuarine invertebrates. Ethion accumulates in the tissues of
fish (8, 9).
Effects on Other Nontarget Species
ENVIRONMENTAL
FATE
The
major metabolite of ethion is carbon dioxide (8).
Breakdown of Chemical in Soil and Groundwater
Ethion
adsorbs strongly to soil particles and it is nearly insoluble in water. It is
therefore unlikely to leach or contaminate groundwater (3).
In soil, ethion is subject to microbial degradation. It is resistant to
hydrolysis, except in alkaline conditions (pH 9 or above) (4,
8).
Ethion is broken down in acids and bases. It is very slowly broken down in the
air (7).
Under laboratory conditions, the soil
half-life of ethion was 1.3 to 8 weeks, but in a greenhouse with an organic
soil, it was more persistent, with half-lives of 16 to 49 weeks, depending on
the degree of watering. When used repeatedly, ethion residues in soil will
increase from one year to the next (4).
Breakdown of Chemical in Water
Ethion
is almost insoluble in water (7).
In open waters, it is likely to adsorb to suspended particles and bottom
sediments. The persistence half-life of ethion varied from 4 to 22 weeks when
tested in three different natural waters under laboratory conditions. It breaks
down slowly in irrigation canal water (half-life = 26 days) (J. Agric. Food
Chem. 31 (4):704.1983). Its hydrolysis half-lives at 25 degrees C are 63, 58,
25 and 8.4 weeks at pHs 5, 6, 7 and 8, respectively. The half-life was 1 day at
pH 10 and 30 degrees C. Microbial degradation of ethion may be insignificant in
open waters. Volatilization be important only in shallow, rapidly moving
streams. Photo-oxidation may occur in sunlight. Bioconcentration of ethion may
be significant (4).
Breakdown of Chemical in Vegetation
No
information found.
Physical
Properties and Guidelines
Pure ethion is a colorless to light brown or
pale yellow liquid with no odor (2,
6).
Technical ethion has a very disagreeable odor. Ethion is stable under normal
temperatures and pressures if kept in a closed container, but it may oxidize
slowly if exposed to air. Ethion will hydrolyze in the presence of bases, acids
or lime (6).
Thermal decomposition of ethion may release toxic gases such as diethylsulfide,
sulfur dioxide, carbon monoxide, carbon dioxide, and phosphorus pentoxide (2).
Major tranquilizers (phenothiazines and
thioxanthines) may enhance the toxicity of organophosphates (Martin. Hazards of
Medication. 1971).
Persons who work with organophosphate
materials for long periods of time should have frequent blood tests of their
cholinesterase levels. If the cholinesterase level falls below a critical
point, no further exposure should be allowed until it returns to normal (10).
Protective clothing must be worn when using
ethion. Before removing gloves, wash them with soap and water. Always wash
hands, face and arms with soap and water before smoking, eating or drinking.
After work, remove all work clothes and shoes. Shower with soap and water. Wear
only clean clothes when leaving the job. Wash contaminated clothing and
equipment with soap and water after each use. Keep contaminated work clothes
separate from regular laundry (8).
Exposure
Guidelines:
0.4 mg/m3 OSHA TWA (skin) (6)
|
0.4 mg/m3 ACGIH TWA (skin) (6)
|
0.4 mg/m3 NIOSH Recommended TWA (skin) (6)
|
Physical
Properties:
CAS #:
|
563-12-2
|
Specific gravity:
|
|
Solubility in water:
|
practically insoluble (2)
|
Solubility:
|
|
Boiling point:
|
|
Melting point:
|
|
Flash point:
|
176 degrees C (2)
|
Vapor pressure:
|
1.5 x 10 to the minus 6 power mm Hg at 20
degrees C (5).
|
Koc:
|
8890 g/ml (3)
|
Oil:
|
water partition coefficient - 5.073 (J.
Environ. Sci. Health part B. B18 (6):667-83.1983).
|
pH:
|
5.1 in an equal volume of water (8)
|
Chemical class/use:
|
organophosphate insecticide
|
BASIC
MANUFACTURER
FMC
Corp.
Agricultural Chemicals Group
2000 Market St.
Philadelphia, PA 19103
Agricultural Chemicals Group
2000 Market St.
Philadelphia, PA 19103
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