paraquat

Paraquat is a non-selective contact herbicide whose active ingredient is paraquat dichloride. It is used worldwide in agriculture and horticulture to kill a wide range of weed species by destructive desiccation of green plant tissue. When applied to foliage, paraquat acts primarily on contact and does not move systemically within the plant after absorption. It binds strongly to soil, making it relatively immobile and generally inactive in soil after application.

The herbicidal effect stems from paraquat’s redox cycling in plant cells, generating reactive oxygen species that cause rapid membrane damage and cellular injury. This leads to rapid chlorosis and desiccation of treated tissue and, at effective doses, plant death. Paraquat is quickly degraded in most environments, but its toxicity to exposed tissues means accidental exposure can be dangerous to humans and animals.

Uses and formulations vary by crop and region, with paraquat products often marketed under brand names such as Gramoxone. It is typically applied as an aqueous spray to actively growing weeds, with care taken to avoid drift and contact with non-target vegetation.

Toxicity and safety are central considerations. Paraquat is highly toxic to humans and many animals when ingested, inhaled, or absorbed through the skin, and there is no widely accepted antidote. Management of exposure focuses on decontamination, supportive care, and, in some cases, early gastric lavage or charcoal. Long-term hazards include potential severe lung injury and fibrosis after ingestion.

Regulatory status varies by country. Paraquat is subject to strict labeling, handling, and usage restrictions in many jurisdictions and has been banned or severely restricted in several markets due to its acute lethality and public health concerns.