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DESIGNATIONS
CAS No.: 56-38-2
Registry name: Parathion
Chemical name: O,O-Diethyl-O-4-nitrophenyl-thiophosphate
Synonyms, Trade names: Parathion-ethyl, O,O-Diethyl-O-4-nitrophenyl-phosphorothioate, E 605, Eftol, Folidol
Chemical name (German): Parathion, Ethyl-Parathion
Chemical name (French): Parathion
Appearance: yellowish to dark brown liquid with garlic odour
BASIC CHEMICAL AND PHYSICAL DATA
Empirical formula: |
C10H14NO5PS |
Rel. molecular mass: |
291.27 g |
Density: |
1.265 g/cm3 |
Boiling point: |
375°C (above 160°C, parathion isomerises slowly to form O,S-Diethyl-O-4-nitrophenyl-thiophosphate which is less stable and less effective) |
Melting point: |
6.1°C |
Vapour pressure: |
5 x 10-3 Pa |
Flash point: |
> 120°C |
Ignition temperature: |
(may be marketed in flammable mixtures) |
Solvolysis/solubility: |
in water: 24 mg/l at 25°C soluble in most organic solvents: in dichloromethane, 2-propanol, toluene > 200 g/l; in n-hexane 50-100 g/l; very slightly soluble in kerosene and mineral oil |
Conversion factors: |
1 mg/m3 = 0.083 ppm 1 ppm = 12.106 mg/m3 |
ORIGIN AND USE
Usage:
Parathion is a broad-spectrum insecticide which acts as a contact, feed or respiratory
poison. It is widely used against biting and sucking insects in agriculture, fruit-,
vegetable- and winegrowing as well as against mites, beetles and caterpillars. It is
usually applied as a spray (emulsion: 500 g/l; oil: 10%).
Origin/derivation:
Emissions are mainly caused by the production and the use of parathion.
Toxicity
Humans: |
LD50 3-5 mg/kg, oral (estimated) |
acc. PERKOW, 1992 |
LD 5-15 mg/kg (pure subst.), oral |
acc. UBA, 1986 |
|
Mammals: |
||
Rat |
LD50 3.6-13 mg/kg, oral |
acc. PERKOW, 1992 |
LD50 6.8-21 mg/kg, dermal |
acc. PERKOW, 1992 |
|
LC50 0.05 mg/l (4h), inhalation |
acc. PERKOW, 1992 |
|
NOEL 10 mg/kg feed (2a) |
acc. PERKOW, 1992 |
|
TDLo 0.36 mg/kg (2.-22. day of pregnance), oral |
acc. UBA, 1986 |
|
Mouse |
LD50 12.8-25 mg/kg, oral |
acc. PERKOW, 1992 |
Guinea pig |
LD50 16-32 mg/kg, oral |
acc. PERKOW, 1992 |
Insects: |
||
Bees |
LD50 0.11 mg/bee, contact |
acc. PERKOW, 1992 |
LD50 0.28 mg/bee, oral |
acc. PERKOW, 1992 |
|
Aquatic organisms: |
||
Rainbow trout |
LC50 1.43 mg/l (96 h) |
acc. PERKOW, 1992 |
Perch |
LC50 0.4 mg/l (96 h) |
acc. PERKOW, 1992 |
Goldfish |
LC50 1.83 mg/l (96 h) |
acc. PERKOW, 1992 |
Golden orfe |
LC50 0.57 mg/l (96 h) |
acc. PERKOW, 1992 |
LC0 0.26 mg/l, (96h) |
acc. HOMMEL, 1993 |
|
LC50 0.48 mg/l, (96h) |
acc. HOMMEL, 1993 |
|
LC100 1.2 mg/l, (96h) |
acc. HOMMEL, 1993 |
|
Characteristic effects:
Humans/mammals: Human poisoning can result from oral intake, inhalation or dermal exposure. Parathion is readily adsorbed and distributed in the organism. It irreversibly inhibits the acetylcholinesterase enzyme and thus disrupts the normal functioning of the central nervous system. Typical symptoms of acute poisoning are headache, sweating and faintness followed by impaired vision, gastrointestinal disorders, shortness of breath, tremors, convulsions, unconsciousness, pulmonary paralysis and finally cardiac arrest. These symptoms may also appear after a delay of several hours [UBA, 1986].
Plants: Tolerance is generally good. Some strains of apples, cucumbers and tomatoes are sensitive to overfeeding.
ENVIRONMENTAL BEHAVIOUR
Water:
The half life in aqueous solutions is strongly dependent on the pH. At low pH, hydrolysis
is very slow but in a neutral and especially in an alkaline environment, it takes place
much faster. In addition, the hydrolysis rate rises with increasing temperature [KOCH,
1989].
pH |
temperature |
half-life |
1-5 |
0°C |
3000 d |
20°C |
690 d |
|
30°C |
180 d |
|
8 |
20°C |
99 d |
In experiments carried out in a sealed glass jar (initial concentration: 10 mg/l) in sunlight and under artificial fluorescent light, residues of 50% have been detected after 1 week. After 4 weeks, residues of less then 5% have been detected and after 8 weeks no residues could be detected [VERSCHUEREN, 1983].
Soil:
The data on the persistence of parathion in soil are varying: the persistence of
organophosphorus insecticides is generally low. The half-life of parathion is about 3-6
months [ULLMANN, 1989].
After 3 weeks, residues of 5% and after 15 weeks residues of 3.2% have been detected in sandy-loamy soil. In organic soil, residues of 5% have been found after 10 weeks. Residues are detectable up to 16 years following the application [PERKOW, 1992; VERSCHUEREN, 1983].
Degradation, decomposition products:
In the organism of mammals, parathion is oxidised forming the more toxic paraoxone,
and hydrolysed forming nitrophenol and diethyl phosphate. It is excreted relatively fast
mainly via urine (86-93%) [PERKOW, 1992].
ENVIRONMENTAL STANDARDS
| Medium/ acceptor |
Sector | Country/organ. | Status | Value | Cat. | Remarks | Source |
| Water: | Drinkw | D | L |
0.1 mg/l |
single substance | acc. KOCH, 1989 | |
| Drinkw | D | L |
0.5 mg/l |
sum of pesticides | acc. KOCH, 1989 | ||
| Drinkw | SU | L |
0.3 mg/l |
acc. KOCH, 1989 | |||
| Surface | EC | G |
1 mg/l |
1) | physical treatment | acc. LAU-BW, 1989 | |
| Surface | EC | G |
2.5 mg/l |
1) | physical / chemical treatment | acc. LAU-BW, 1989 | |
| Surface | EC | G |
5 mg/l |
1) | physical / intensified chemical treatment | acc. LAU-BW, 1989 | |
| Air: | Workp | D | L |
0.1 mg/m3 |
MAK | Skin | acc. AUER TECHNIKUM, 1988 |
| Workp | D | L |
500 mg/l |
BAT | 2) | acc. AUER TECHNIKUM, 1988 | |
| Workp | SU | (L) |
0.05 mg/m3 |
PDK | Skin | acc. AUER TECHNIKUM, 1988 | |
| Workp | USA | (L) |
0.1 mg/m3 |
TWA | Skin | acc. AUER TECHNIKUM, 1988 | |
| Workp | USA | (L) |
0.3 mg/m3 |
STEL | Skin | acc. UBA, 1986 |
1)Quality requirements for the preparation of drinking water from surface water.
2) parameter: p-nitrophenol plus acetylcholinesterase in blood
Assessment/comments
Parathion is only moderately persistent in the environment and does not accumulate in the pedosphere or in the biosphere. On the other hand, it lacks sensitivity and is highly toxic to bees, beneficial parasites, fish, mammals and humans.