exposures are unlikely to survive. Chronic exposure can lead to lung damage, kidney failure, heart failure, and oesophageal strictures. The mechanism underlying paraquat's toxic damage to humans is still unknown. The severe inflammation is thought to be caused by the generation of highly reactive oxygen species and nitrite species that results in oxidative stress. The oxidative stress may result in mitochondrial toxicity and the induction of apoptosis and lipid peroxidation which may be responsible for the organ damage. it is known that the alveolar epithelial cells of the lung selectively concentrate paraquat. It has been reported that a small dose, even if removed from the stomach or spat out, can still cause death from fibrous tissue developing in the lungs, leading to asphyxiation. Accidental deaths and suicides from paraquat ingestion are relatively common. For example, there are more than 5,000 deaths in China from paraquat poisoning every year. Long-term exposures to paraquat would most likely cause lung and eye damage, but reproductive/fertility damage was not found by the United States Environmental Protection Agency (EPA) in their review. "Paraquat pot" During the late 1970s, a controversial program sponsored by the US government sprayed paraquat on cannabis fields in Mexico. Following Mexican efforts to eradicate marijuana and poppy fields in 1975, the United States government helped by sending helicopters and other technological assistance. Helicopters were used to spray the herbicides paraquat and 2,4-D on the fields; marijuana contaminated with these substances began to show up in US markets, leading to debate about the program. Whether any injury came about due to the inhalation of paraquat-contaminated marijuana is uncertain. A 1995 study found that "no lung or other injury in cannabis users has ever been attributed to paraquat contamination". Also a United States Environmental Protection Agency manual states: "... toxic effects caused by this mechanism have been either very rare or nonexistent. Most paraquat that contaminates cannabis is pyrolyzed during smoking to dipyridyl, which is a product of combustion of the leaf material itself (including cannabis) and presents little toxic hazard." In a study by Imperial Chemical Industries, rats that inhaled paraquat showed development of squamous metaplasia in their respiratory tracts after a couple of weeks. This study was included in a report given to the State Department by the Mitre Corporation. The U.S. Public Health Service stated that "this study should not be used to calculate the safe inhalation dose of paraquat