Environmental Toxicology and Health Effects Associated with Methyl Parathion Exposure – A Scientific Review

Abstract

Methyl parathion - MP (C[8]H[10rsqbNO[5rsqbPS) is a restricted-use pesticide that has been widely used as an agricultural insecticide. It belongs to the class of organophosphate chemicals characterized by their ability to inhibit acetylcholinesterase activity. The main route of human exposure is inhalation, but dermal contact and inadvertent ingestion can also be substantial. Populations that are susceptible to MP exposure primarily are applicators, manufacturers and individuals living near application and/or disposal sites. Exposure has also been reported as a result of illegal indoor application. MP related health effects include headaches, nausea, night-waking, diarrhea, difficulty breathing, excessive sweating and salivation, incoordination, and mental confusion. Other symptoms including behavior problems, motor skill problems and impairment of memory recall have also been reported. The primary targets of toxicity are the hematopoietic system (serum cholinesterase inhibition), the cardiovascular system (cardiovascular lesions, abnormalities in heart rate and increase in heart-to-body ratio), the reproductive system (placental morphology, fibrosis and hemorrhage, and inhibition of DNA synthesis in seminiferous tubules), and the nervous system (headache, muscle weakness, insomnia, dizziness, and impaired memory). MP is believed to not have any carcinogenic effects. In an attempt to update its toxicologic profile, we hereby provide a critical review of MP-related environmental and toxicologic effects, with a special emphasis on their potential implications for public health.

Effects of the organophosphorus pesticide Folisuper 600 (methyl parathion) on the heart function of bullfrog tadpoles, Lithobates catesbeianus (Shaw, 1802)

“…It is available in several commercial formulations as Metaphos, Dalif, Bladan, Cekumethion, E601, Folidol -M, Fosferno M50, Gearphos, Kilex, Parathion, Folisuper 600 BR, among others (Edwards and Tchounwou, 2005). However, due to its high toxicity, the use of MP in the US has been restricted to certified industries by the US Environmental Protecting Agency (Edwards and Tchounwou, 2005).…”

“…It is available in several commercial formulations as Metaphos, Dalif, Bladan, Cekumethion, E601, Folidol -M, Fosferno M50, Gearphos, Kilex, Parathion, Folisuper 600 BR, among others (Edwards and Tchounwou, 2005). However, due to its high toxicity, the use of MP in the US has been restricted to certified industries by the US Environmental Protecting Agency (Edwards and Tchounwou, 2005). In contrast, in developing countries, where neither its sale nor its application are intensively monitored by controlling agencies, MP is consumed without limitation in agriculture and for aquaculture purposes due to its low cost associated to a high efficacy.…”

“…As a consequence, ACh accumulates in the synaptic cleft. Among the effects of cholinergic overstimulation already described to mammals are tearing, sweating, cardiorespiratory alterations, salivation, changes in the central nervous system, bradycardia, as well as muscle necrosis (Cavaliere et al, 1996;Edwards and Tchounwou, 2005). However, information regarding the effects of exposure to MP and other OPs in amphibians is still scarce (Taylor et al, 1999;Khan et al, 2003).…”

In vitro evaluation of neutral oximes as reactivators of parathion-inhibited electric eel acetylcholinesterase

“…Inhibition of AChE and butyrylcholinesterase results in ACh accumulation in cholinergic synapses of the peripheral and central nervous systems. Increased ACh overstimulates muscarinic and nicotinic receptors, resulting in peripheral muscarinic (salivation, lacrymation, nausea, bradycardia, bronchosecretion), nicotinic (skeletal muscle fasciculations, diaphragm and intercostal paralysis) and central (muscle tremors, convulsions, coma and respiratory depression) manifestations that lead to death [7][8][9] . Current antidotal regimens approved for human treatment of OP poisoning consist of a combination of muscarinic receptor antagonists (atropine), anticonvulsants (benzodiazepines) and AChE reactivators (oximes), such as obidoxime, 2-PAM, TMB-4 and HI-6 10,11 .…”

Headache caused by handling the pesticide Antracol Combi WP 76: a case report

“…Pesticides can cause gene mutations and chromosomal aberration in exposed individuals [1][2][3][4][5]. The primary targets of toxicity are the haematopoetic system (serum cholinesterase inhibition), the cardiovascular system (cardiovascular lesions, abnormalities in heart rate and increase in heart-to-body ratio, tachycardia, tachypnoea, sinus bradycardia, depression of ST segments with T-wave inversion, elevated blood pressure), the reproductive system (placental morphology, fibrosis and haemorrhage, and inhibition of DNA synthesis in seminiferous tubules) and the nervous system (headache, muscle weakness, insomnia, dizziness, impaired memory, miosis, fasciculation, neuralgia) [6][7][8][9]. Some patients poisoned with pesticides complain of vague symptoms such as headache, dizziness, fatigue, nausea, vomiting, abdominal pain, myalgia, flulike symptoms, etc.…”