A fatal case of malathion and organic-solvent intoxication: the potential utility of cerebrospinal fluid

Malathion is one of the most widely used organophosphate insecticides worldwide. Although generally regarded as relatively safe, numerous accidental and intentional poisoning cases have been reported, including fatalities. However, interpretation of postmortem blood concentrations is challenging because reported concentrations vary widely among fatal cases, and malathion may be undetectable in postmortem blood despite documented exposure. Postmortem loss of intact malathion from blood may occur, and no definitive lethal concentration or diagnostic criteria for malathion poisoning have been established. We report the case of an elderly woman in her 80s who was found dead outdoors. Toxicological analysis revealed the presence of malathion, ethylbenzene, and xylenes in blood and cerebrospinal fluid (CSF), and the death was attributed to mixed intoxication. Malathion concentrations were 0.89 μg/mL in cardiac blood, 0.70 μg/mL in femoral blood, and 2.6 μg/mL in CSF, with higher levels in CSF than in blood. This difference may partly reflect the substantially lower protein content of CSF and its negligible red blood cell content, which may reduce protein-associated loss of free malathion. These findings suggest that CSF may be a useful complementary matrix for evaluating malathion in postmortem cases.