Used as contact insecticides; formerly widely used in agriculture and for domestic purposes, their use is now restricted in some countries due to recognition of their extreme persistence in the environment and potential for chronic toxicity.

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Animals most affected
All species.

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Etiology

• accidental ingestion (cattle, dogs) of agricultural products, treated cereals
• and dressed seeds, and by licking out empty drums which previously contained the chemical;
• inhalation following crop spraying (spray or spray drift) in bad weather,
• using either aerial or ground sprays in the vicinity of domestic or wild animals;
• incorrect disposal of rinsing water from chemical containers or spray equipment into rivers and ponds;
• accidental disposal of wood preservatives (containing pentachlorophenols, and frequently lindane) directly
• into rivers or soakaways.

Note: possibility of iatrogenic incidents where some organochlorines (e.g. lindane) are used on domestic pets for the treatment of ectoparasites.

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Compounds in this category
AIdrin, chlordane, chlordecone, DDT, dicofol, dieldrin, dienochlor, endosulfan, endrin, lindane, perthrane, toxaphene. Lindane is also widely known as gamma hexachlorocyclohexane (gamma-HCH) or gamma benzene hexachloride (gammaBHC).
Many of the above, along with organochlorine compounds in general, are either banned from use (in both the UK and France) or are permitted for only severely restricted usages.

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Toxicity
Persistent liposoluble compounds which concentrate in body fat and nervous tissue.
Toxic to the nervous system. For toxicity, see entries for individual compounds.

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Clinical features
Acute poisoning
Occasionally immediate onset of clinical signs with death occurring in a few minutes, accompanied by hyperaesthesia, trembling, convulsions, or depression (particularly following inhalation exposure). Characteristic clinical signs include:

• muscular fasciculations of the face and neck followed by
• tremor and shaking, generalized fasciculations;
• salivation;
• ataxia;
• occasionally agitation, aggression, abnormal postures or behaviour (wall butting, autoausculation), groaning or whining, grinding of the teeth, nystagmus, superseded by:
• tonic-clonic convulsions with periods of remission, paddling movements of the legs, hyperaesthesia, opisthotonos and hyperthermia, which is common at this stage.

Death may occur during the convulsive stage within a few hours, or after several days. In particular species (e.g. cats), or in some individual animals, the dominant features of poisoning are depression, weakness, prostration, coma and death.

Chronic poisoning
(Difficult to diagnose and relatively nonspecific):

• anorexia, weight loss, fall in milk production;
• several episodes of trembling and shaking, persistent convulsions, deterioration, leading to
• death in several weeks to several months.

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Lesions
Non-specific.

In acute poisoning

• generalized congestion;
• petechiae on the heart, intestines and lungs;
• oedema of the brain and spinal cord.

In chronic poisoning

• degeneration of the liver and kidneys is common.

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Treatment
No antidote. Symptomatic care only:

• encourage excretion;
• minimize dermal absorption (wash the skin with soap) and limit absorption from the gut (adsorbents, gastric lavage);
• cardiorespiratory stimulants;
• control the convulsions: diazepam, xylazine; use barbiturates with caution as they may depress cardiac and respiratory functions.

Notes:
Organochlorines have two fundamental characteristics: liposolubility and chemical persistence. In addition, they are powerful enzyme inducers. These factors explain the extent and the degree of contamination of ecosystems by organochlorines, justifying their restriction or even prohibition in use.
Organochiorines accumulate in the food chain, with highly significant concentration factors of 10000 or more. Due to their ability to induce mono-oxygenase enzymes, specific toxic effects can be observed which are clearly evident in animals at the top of food chains. In raptors (birds of prey), eggshell fragility and lowered fecundity have been well documented.
The inherent properties of the organochlorines also explain their transfer as residues into fats used for foods, such as dairy products (milk, butter, etc.), which have had important consequences for public health and a significant economic impact.