Negative ions are needed in order to take in oxygen.

"Please, we’re dying here!"
Russian scientist, Dr. A. L. Tchijewsky, tried raising mice, rats, guinea pigs, and rabbits in totally de-ionized air. Almost all of them died within two weeks due to an inability to utilize oxygen properly (Tchijewski, 1960).

Tchijewsky’s colleague, Dr. D. A. Lapitsky, tried raising small animals in air completely devoid of oxygen. He added only negative ions to the air as they were about to die from asphyxiation. At which point, their respiration frequency drastically increased, as they began to sit up and run around the chamber (Tchijewski, 1960).

Don’t travel to space without `em
Former NASA scientist James B. Beal, who came across the negative ion problem while studying the type of environment needed in space capsules, wrote: "The human race was developed in ionized air. Nature used the ions in developing our biological processes." In other words, people have been designed to function properly in an environment that contains certain level of ionization (Soyka, 1991).

The more the better
Fred Soyka, author of "The Ion Effect" reports that based on the 5,000 plus scientific documents that have been published regarding negative ion studies, all support the conclusion that an overload of negative ions seems to be beneficial (Soyka, 1991).