Many respiratory effects of toxic chemicals are due to excessive oxidative burden on the lungs, leading to chronic bronchitis, emphysema, and fibrosis, for example.. Central nervous system oxygen toxicity can cause seizures, brief periods of rigidity followed by convulsions and unconsciousness, and is of concern to divers who encounter greater than atmospheric pressures. Pulmonary oxygen toxicity results in damage to the lungs, causing pain and difficulty in breathin