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Parathion

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:

375C

(above 160C, parathion isomerises slowly to form O,S-Diethyl-O-4-nitrophenyl-thiophosphate which is less stable and less effective)

Melting point:

6.1C

Vapour pressure:

5 x 10-3 Pa

Flash point:

> 120C

Ignition temperature:

(may be marketed in flammable mixtures)

Solvolysis/solubility:

in water: 24 mg/l at 25C

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

0C

3000 d

20C

690 d

30C

180 d

8

20C

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.


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