A woman is taken to the emergency room at a hospital. Looks like she has put a heavy duty degreaser gel containing dimethyl sulfone or dmso on her body to relieve body pains from her cancer. As the dmso was being absorbed into her system via her skin, it was breaking down in her blood. On the way to the ER, the EMTs put an oxygen mask on her. As the oxygen was being absorbed into her blood, the oxygen atoms bonded to the broken down dmso to form the more toxic dimethyl sulfate. When they went to draw her blood, some of the dimethyl sulfate vaporized into the surrounding air, which the hospital staff breathed in and promptly fell ill.
Dimethyl sulfate is used for industrial purposes to join methyl groups onto organic chemicals or it can be use as a biological weapon/war gas.