Ethylene dibromide - Nematicides

NEMATICIDES

·              These are compounds which kill nematodes (i.e. worms). For example, ethylene dibromide.

Ethylene dibromide

Fumigants are applied to control rodents, nematodes, insects, weed seeds, and fungi anywhere in the soil, structures, crop, grains, and commodities. Many different chemical classes have use today. Most fumigants were abandoned because of their toxicity, many of which were halogenated solvents. The list of discontinued halogenated hydrocarbons includes carbon tetrachloride, chloroform, dibromochloropropane, 1,2-dichlo- ropropane, ethylene dibromide, and ethylene dichloride. Ethylene dibromide was previously approved for use as in citrus, vegetable, and grain crops, and as a fumigant for turf, particularly on golf courses. In 1984, the Environment Protection Agency (EPA) banned its use as a soil and grain umigant. Unfortunately, in India, it continues to be used widely, causing human poisoning not infrequently.

Mode of Action

Ethylene dibromide alkylates macromolecules causing cellular disruption and reduced glutathione levels. Cellular disruption in tissues and organs, such as liver and kidneys, results in progres- sive dysfunction. Manifestation of some of the effects of acute high exposure may be delayed a few days.

Clinical Features

·              Ethylene dibromide is a severe skin irritant in liquid form, and inhaling or ingesting it can cause death.

·              Inhalation/Ingestion: Burning sensation, cough, bronchitis, dyspnoea, pulmonary oedema, hepatotoxicity with liver necrosis, acute renal failure, metabolic acidosis, CNS depres-sion, coma and death. Abdominal pain, vomiting, and diar-rhoea, are common early manifestations in cases of ingestion.

·              Dermal Exposure: Erythema, pain, blistering.

·              Ocular Exposure: Conjunctivitis has been reported after exposure to ethylene dibromide. Temporary loss of vision may occur.

·              Chronic Exposure: There is inconclusive but suggestive evidence that ethylene dibromide may reduce fertility in men. Antispermatogenic effects have been demonstrated in various animal species.

Diagnosis

·      Serum bromide levels can be used to document that expo-sure did occur. However, bromide levels do not accurately predict the clinical course.

·      Routine laboratory studies include CBC, glucose, and electrolyte determinations.

·      Additional studies for patients exposed to ethylene dibro-mide include liver-function tests and renal-function tests.

·      In cases of inhalation exposure, chest radiography and arterial blood gas measurements may be helpful.

Treatment

·      Establish a patent airway, ensure adequate respiration and pulse. Administer supplemental oxygen as required and establish intravenous access if necessary. Place on a cardiac monitor.

·      Irrigate exposed skin and eyes as appropriate. Remove contaminated clothing.

o     Flush exposed skin and hair with water for at least 15 minutes, then wash twice with mild soap. Rinse thor-oughly with water. Use caution to avoid hypothermia when decontaminating patients, particularly children or the elderly. Use blankets or warmers after decontamina-tion as needed.

o     Irrigate exposed or irritated eyes with tap water or saline for 15 to 20 minutes. Remove contact lenses if easily removable without additional trauma to the eye. An ophthalmic anaesthetic, such as 0.5% tetracaine, may be necessary to alleviate blepharospasm, and lid retractors may be required to allow adequate irrigation under the eyelids.

·      Activated charcoal is helpful in cases of ingestion.

·      Treat patients who have bronchospasm with an aerosolised bronchodilator such as salbutamol.

·      If evidence of shock or hypotension is observed, begin fluid administration. For adults with systolic pressure less than 80 mmHg, bolus perfusion of 1,000 ml/hour intravenous saline or lactated Ringer’s solution may be appropriate. Higher adult systolic pressures may necessitate lower perfusion rates. For children with compromised perfusion administer 20 ml/kg bolus of normal saline over 10 to 20 minutes, then infuse at 2 to 3 ml/kg/hour.

·      There is no proven antidote for ethylene dibromide poisoning. Dimercaprol (BAL) or N-acetylcysteine have been suggested as antidotes based on the postulated mechanism of ethylene dibromide’s toxicity. However, no adequate studies have tested the efficacy of these therapies, and they are not recommended for routine use.

·      Supportive and symptomatic measures.

·              Patients who survive should be monitored over a period of time for late neuropsychiatric seque\lae.