Chlopyrifos fatal intoxication: homicide or suicide?

Abstract

To document a fatal case where the organophosphorus compound chlorpyrifos is the cause of death, but the manner of exposure (voluntary or surreptitious) remains unclear. Chlorpyrifos is an organophosphorus insecticide used against a wide range of pests in commercially important crops and also for ornamental garden plants. In addition to being a particularly harmful substance at an environmental level, it also has a dangerous profile for humans. Voluntary suicidal intoxication generally occurs by oral ingestion and gastrointestinal absorption; systemic effects occur within minutes of inhalation when exposed to vapors or aerosols, but are delayed in the case of gastrointestinal absorption. A case of human intoxication is discussed: a 77 y.o. man was admitted at the emergency department due to a sudden alteration of the sensory, with tremors in the upper limbs and poor contactability. His GCS was 10, and he exhibited neurological symptoms of unclear etiology, with myoclonus, diffuse fasciculations, strong asthenia, hyponatremia. Family members did not refer any suspect ingestion nor peculiar circumstances. Only nine days after hospitalization, upon the release of liquid faeces mixed with sand, the toxicological evaluation of biological samples was undertaken thus disclosing the presence of chlorpyrifos. Death occurred after 30 days of coma. A judiciary autopsy was requested by the prosecutor office. Blood, stool, hair were collected during hospitalization. At the autopsy, blood from femoral vein, vitreous, urine, bile, liver, brain, fat and lung tissues were collected. A specific screening and confirmation method for pesticides was performed by GC-MS/MS at the Laboratory of Forensic Toxicology after liquid/liquid extraction with dichloromethane. Chlorpyrifos metabolites (chlorpyrifos oxon, 3,5,6-trichloro-2-pyridinol (TCPy), diethyl thiophosphate, diethylphosphate and glucuronide and sulfate conjugates of TCPy) were also investigated. In vivo: chlorpyrifos levels in blood samples were 893 ng/mL (admittance), 319 ng/mL (2 days later), 92 ng/mL (10 days later), 26 ng/mL (20 days later), and negative (<1 ng/mL) 22 days later. Metabolites were also detected but not quantified due to the lack of reference standards. In the 0-1 cm proximal section of 3 cm long white hair, the parent molecule was absent while O,O,O-triethylthiophosphate was identified. The solid material found in faeces with the appearance of sand was identified as sepiolite. Post-mortem: chlorpyrifos was detected at low levels (<1 ng/g) in fat and brain specimens; nor chlorpyrifos nor its metabolites were found in blood, urine, vitreous, bile, liver and lung specimens. A sealed bottle of “universal insecticide” found near his garden proved to be an emulsion containing chlorpyrifos, with different co-formulants but without any solid material such as sepiolite. The way of ingestion was deemed to be oral comparing the case blood levels with those reported for different ways of exposure. The doubt arose about the intentionality of the ingestion. The sepiolite found in faeces suggested the use of a solid formulation of chlorpyriphos, whereas finding the sealed bottle of liquid formulation seemed to be purportedly confusing. In insecticides containing chlorpyrifos found on the market, solid silica can be used as formulants or co-formulants, and the resulting products are described as free of significant odor, which would make them not excessively disgusting to ingest or to be administered orally as such or mixed with foods/drinks. The cause of death was acute chlorpyrifos intoxication, associated with prolonged coma, multi-organ failure and terminal cardiac arrest. There were no circumstantial and documentary elements useful for defining the dynamics of the intoxicating event as a suicide or a homicide. Voluntary suicide with organophosphorus compounds represents a common occurrence in Asian countries and in Eastern European countries but not in Italy.