These compounds are notorious for their health hazards. Most of the health effects are due to inhibition of cholinesterases (Kamanyire and Karalliedde, 2004). Other than this, inhibition of other enzymes and individual susceptibility also play a role. The compounds are highly lipid-soluble and can be absorbed from any route like skin, conjunctiva, mucus membranes, gastrointestinal tract and respiratory tract.
The onset of illness, severity and duration of each phase of illness depends not only on the type of the OP compounds to which the individual has been exposed to, but also the dosage of exposure, route of exposure, characteristics of the cholinesterase enzyme, rate of metabolism in the body and the physico-chemical properties of the compound. Cholinesterase plays an important role in the cell-to-cell communication and is present in several parts of the body like blood, nerves, neuromuscular tissue and glandular tissues. Inactivation of acetyl cholinesterase causes accumulation of acetyl choline in ganglia and synapses leading to various clinical problems (Kamanyire and Karalliedde, 2004).
Exposure to these OP compounds leads to triphasic illness in human beings. The first phase is the cholinergic phase. In most of the exposed individuals, only the cholinergic phase may be observed. This is followed by an intermediate phase in 20 percent of the cases, followed by a final phase. The initial 2 phases are associated with mortality and morbidity, while the final phase is not associated with mortality and may not be preceded by the initial 2 phases (Kamanyire and Karalliedde, 2004). In the acute cholinergic phase, accumulation of acetyl choline in the muscarinic sites leads to bronchoconstriction, increased bronchial secretions, increased gastrointestinal motility, vomiting, bradycardia and blurring of vision due to miosis. Accumulation in nicotinic sites like the neuromuscular junction results in flaccid