Paraquat (dipyridylium) is a highly toxic weed killer once promoted by the United States for use in Mexico to destroy marijuana plants. Research found that this herbicide was dangerous to workers who applied it to the plants.

This article discusses the health problems that can occur from swallowing or breathing in Paraquat.

In the United States, Paraquat is classified as "restricted commercial use," and people must obtain a license to use the product.

Breathing in Paraquat may cause lung damage and can lead to a disease called Paraquat lung. Paraquat causes damage to the body when it touches the lining of the mouth, stomach, or intestines. You can get sick if Paraquat touches a cut on your skin. Paraquat may also damage the kidneys, liver, and esophagus.

If Paraquat is swallowed, death can rapidly occur. Death may occur from a hole in the esophagus, or from acute inflammation of the mediastinum, the area that surrounds the major blood vessels and airways in the middle of the chest.

Chronic exposure to Paraquat may cause pulmonary fibrosis, a stiffening of the lung tissue.