Pulmonary histological appearances in fatal paraquat poisoning.

The paper describes the histological appearances in the lungs from 11 fatal cases of paraquat poisoning. The study originated as an attempt to define the sequential changes in the condition and, from them, to assess the mode of action of the herbicide in the human. The main features of the "paraquat lung" include haemorrhage, extrusion of macrophages, oedema, "honeycombing", fibrosis and, rarely, epithelial hyperplasia. The indications are that the changes are progressive once a threshold tissue concentration has been reached. The appearances are compared to those in poisoning by hyperbaric oxygen and it is hypothesized that the toxic action of paraquat is to sensitize the lungs to oxygen at atmospheric pressure.