Fun stuff.
Aniline is a systemic toxicant absorbed through all major routes of exposure, including inhalation, ingestion, and rapid absorption through the skin. Dermal absorption is particularly significant because the liquid or vapor penetrates the skin quickly, contributing to systemic toxicity even when air concentrations are low. The onset of adverse symptoms following exposure can be delayed for several hours, making it difficult to immediately link the event to the physiological effects.
The most severe acute effect of aniline poisoning is methemoglobinemia. This condition occurs when aniline metabolites oxidize the iron in hemoglobin, converting functional Fe2+ to Fe3+. This renders the hemoglobin molecule incapable of transporting oxygen to tissues. Symptoms, which can be delayed up to 20 hours, include headache, dizziness, fatigue, and cyanosis—a bluish discoloration of the skin and lips. Severe exposure can lead to convulsions, cardiac issues, collapse, and death.
Chronic exposure to aniline poses long-term health concerns, primarily affecting the blood. Long-term exposure can lead to chronic hemolytic anemia, involving the destruction of red blood cells. While human data remains inadequate to definitively link aniline to bladder tumors, the U.S. Environmental Protection Agency (EPA) has classified aniline as a probable human carcinogen based on animal studies showing it causes spleen tumors.