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DDT

DESIGNATIONS

CAS No.: 50-29-3
Registry name: DDT
Chemical name: 1,1,1-Trichloro-2,2-bis(4-chlorophenyl)ethane
Synonyms, Trade names: p,p’-Dichlorodiphenyltrichloroethane, p,p’-DDT, 1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane, Dicophane (GB); Chlorophenothane (USA); Anofex; Cezarex; Dinocide; Gesarol; Guesapon; Guesard; Guesarol; Gyron; Ixodex; Neocid; Neocidol; Zerdane
Chemical name (German): DDT, 1,1,1-Trichlor-2,2-bis(4-chlorphenyl)ethan
Chemical name (French): DDT
Appearance: colourless crystals ranging from odourless to slightly aromatic

BASIC CHEMICAL AND PHYSICAL DATA

Empirical formula: C14H9Cl5
Rel. molecular mass: 354.49 g
Density: 1.55 g/cm3
Melting point: 109C
Vapour pressure: 25.3 x 10-6 Pa
Solvolysis/solubility: in water: 3 x 10-6 g/l

readily soluble in numerous organic solvents and in fats

Conversion factors: 1 ppm = 14.7 mg/m3

1 mg/m3 = 0.07 ppm

ORIGIN AND USE

Usage:
Contact poison and feed insecticide for combating a wide range of insects (malaria and yellow-fever mosquito, plague flea, clothes louse, tsetse fly etc.). The substance was used on a large scale because of its broad-spectrum effectiveness, its low phytotoxicity, its good long-term effect and its low acute toxicity to warm-blooded animals. Whereas the use of DDT is banned today in most industrial nations, it is still used in numerous Third-World countries since the costs of substitute materials are much higher.

Origin/derivation:
DDT is not found naturally. It was synthesised for the first time in 1874 and has been commercially available by condensation of chloral with chlorobenzene since 1945.

Production figures:
Recent data are not available. The estimated production figures in 1974 (OECD) were about 60,000 t worldwide (WHO, 1979). DDT was originally manufactured in many countries, but by 1979 there were only 3 production facilities left, namely in America, India and France (WHO, 1979). The DVGW, on the other hand, quotes two companies in the EC alone (1988).

Emission figures:
Virtually all the DDT produced is released into the environment. The quantities applied are usually between 1 and 3 kg DDT per hectare; the products used contain between 1 and 10 % active agent.

Toxicity

Humans: LD approx. 500 mg/kg, oral acc. RIPPEN, 1989
Mammals:
Rat LD50 113 mg/kg, oral acc. RIPPEN, 1989
LD50 1900 mg/kg, dermal acc. RIPPEN, 1989
Mouse LD50 150-300 mg/kg, oral acc. DVGW, 1988
Dog LD50 150-750 mg/kg, oral acc. DVGW, 1988
Cat LD50 150-600 mg/kg, oral acc. DVGW, 1988
Insects:
House fly (musca domestica) LD50 0.033 g/animal (24 h) acc. KORTE, 1980
Aquatic organisms:
Fish LC50 8-100 g/l (96 h) acc. RIPPEN, 1989
Water flea (daphnia magna) EC50 0.36-4.4 g/l (24-48 h) acc. RIPPEN, 1989
Algae (skeletonema costatum) EC50 100 g/l (7 d) acc. DVGW, 1988

Characteristic effects:

Humans/mammals: The exact mechanism of action still has to be completely clarified. DDT is a neurotoxin which mainly acts on the central nervous system. The external symptoms indicate a temporary easing of the transmission of stimuli followed by blockage. Various enzymes are inhibited by DDT. It thus also acts as a respiratory poison. It accumulates in fatty tissue. Damage to the liver in particular with high doses; sustained exposure (rats) led to liver, kidney and spleen damage. Mutagenity and carcinogenity are highly likely in humans; carcinogenity discovered in animal experiments.

Plants: DDT does not usually damage plants. Some sensitive plants show signs of impaired root growth in the event of DDT accumulation in the soil.

Synergism: Enhanced action (aquatic animals) due to lindane and alkylbenzene sulphonates.

ENVIRONMENTAL BEHAVIOUR

Water:
DDT exhibits a strong tendency towards adsorption on solid particles in water. It thus accumulates in sediment and can be transported in running water over long distances.

Air:
DDT is found in the atmosphere as a gas, as an aerosol and adsorbed on dusts. It can still be detected 6 months after application in the air over fields on which it has been used. Adsorbed on dusts, it is sometimes transported over thousands of kilometres and thus dispersed worldwide. DDT has been detected not only in Antarctic snow, but also in precipitation over Scotland and the Shetland Islands. The concentrations found in rain permit to draw the conclusion that the distribution of DDT throughout the world is relatively uniform.

Soil:
When DDT is applied, a considerable amount ends up in the soil. Considerable accumulation has been discovered in the top few centimetres, thus concluding that the mobility in soil is relatively low.

Degradation, decomposition products:
Important metabolites of DDT are DDE (1,1-bis-(4-chlorophenyl)-2,2-dichloroethene), DDA and DDD. DDE is at least as toxic as DDT and would appear to be even more resilient in the environment.

There is little information to date regarding the degradation of DDT in soil. The relationship between biological and chemical decomposition reactions remains to be explained. All in all, DDT and certain transformation products (see above) should be classed as very persistent.

There is also a lack of reliable data concerning the transformation and degradation processes of the substance in the atmosphere. HCl and CO2 were established as degradation products in laboratory experiments under simulated upper-atmosphere conditions. Rapid decomposition due to UV rays has been reported by various authors. There are no representative data regarding photomineralisation under natural conditions (WHO, 1979).

Food chain:
Considerable accumulation via food chains. It can be detected in the circulation of warm-blooded animals soon after absorption, it is however subsequently removed by organs containing lipids and is stored in, for example, fatty tissue, the brain and the liver.

ENVIRONMENTAL STANDARDS

Medium/ acceptor Sector Country/ organ.

Status

Value Cat. Remarks Source
Water: Drinkw A

(L)

1 g/l   DDT and isomers acc. DVGW, 1988
Drinkw CDN

(L)

30 g/l MAC DDT and isomers acc. DVGW, 1988
Drinkw D

L

0.1 g/l   single substance acc. DVGW, 1988
Drinkw EC

G

0.1 g/l     acc. DVGW, 1988
Drinkw WHO

G

1 g/l   DDT and isomers acc. DVGW, 1988
Groundw USA

G

0.05 mg/l   State of Illinois acc. WAITE, 1984
Surface IAWR

G

0.1 g/l   Drinking water1) acc. DVGW, 1988
Surface IAWR

G

0.5 g/l   Drinking water2) acc. DVGW, 1988
Surface D

G

2 g/l   Drinking water1) acc. DVGW, 1988
Surface D

G

10 g/l   Drinking water2) acc. DVGW, 1988
Surface USA

G

0.05 mg/l   State of Illinois acc. WAITE, 1984
Air: Workp D

L

1 mg/m3 MAK   DFG, 1987
Workp USA

(L)

1 mg/m3 TWA   acc. RIPPEN, 1989
Foodstuffs:
Tea, spices   D

L

1 mg/kg     acc. DVGW, 1988
Fruit, vegetables   D

L

0.1 mg/kg     acc. DVGW, 1988
Other veg. foodstuffs   D

L

0.05 mg/kg     acc. DVGW, 1988
Fat in meat   D

L

3 mg/kg     acc. DVGW, 1988
Fat in fish   D

L

2-5 mg/kg     acc. DVGW, 1988
Fat in milk   D

L

1 mg/kg     acc. DVGW, 1988
Eggs   D

L

0.5 mg/kg     acc. DVGW, 1988

Notes:

1) Drinking water treatment using natural methods
2) Drinking water treatment using chemophysical methods
The production and use of DDT has been banned in Germany since 1974. Usage is also banned in Sweden and the USA.

Comparison/reference values

Water:
Surface water (1977-79) USA 0.1 ppb; (max. n=604)
Antarctic   40 ppt
Baltic   0.2 ppt
Groundwater (1977-79) USA 0.9 ppb; (max. n=1074)
Rainwater GB 104-229 ppt
Sediment:
Lakes and river (Berlin) D 0.01-136 ppb (n=8)
Lake Libya 0.02 ppb
Mediterranean (1981)   <0.01-19 ppb
Air:
'Clean air' D 0.2-0.6 ng/m3
Persian Gulf   0.05-0.58 ng/m3 (mean value: 0.08 ng/m3)
Gulf of Mexico   0.010-0.047 ng/m3
Humans:
Mother's milk D 1.5-1.8 mg/kg fat
Fatty tissue   1.1-5.3 mg/kg (mean values)
Animals:
Fish (Lake Michigan; 1969-78) USA 0.8-9.9 mg/kg
Fish (North Sea; 1972)   2-73 g/kg
Pike-perch (Havel, Berlin; 1981) D 2-105 g/kg
Plants:
Aquatic plants (Danube)   2 g/kg

Note: 1) If no other source is quoted, the data cited are from RIPPEN, 1989.

Assessment/comments

The ban of DDT in several countries in the early Seventies shows its hazardous nature which can primarily be attributed to its considerable persistence in all environmental media (a basic precondition of the worldwide distribution of DDT today). Apart from its acute toxicity, the decisive aspect for any assessment of DDT is its accumulation in organisms, soils, surface water and groundwater and thus its incalculable long-term effect. In view of the fact that substitute products already exist (although still expensive), the application of DDT and also its continued production are ecologically intolerable.


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