I don't think it can be shut down. Here is info from Sharp (mfg of PlasmaCluster) on why this system is better than other ion filtration systems... My assumption (hope) is that Toyota looked into this system before decided to deploy it and deemed it to be effective and safe
First, let me distinguish the difference between "Ionizers", and Plasmacluster Ion Technology. "Ionizers" produce ONLY NEGATIVE IONS, while Plasmacluster Ion Technology is the only technology in the world to use BOTH POSITIVE AND NEGATIVE IONS. With negative ions only, you do not inactivate any contaminants, but simply add weight to the particles so that they drop to the ground. The danger is that they are still ACTIVE and can still HARM you. However, with Plasmacluster Ion's POSITIVE and NEGATIVE ions, the contaminant is INACTIVATED, rendered harmless and therefore CANNOT HARM you. Consumer reports conquered that these "Ionizers" do not work, and moreover produce large amounts of Ozone. For the record, Plasmacluster Ion Air Purifiers generate less than 0.001 ppm of ozone. That is more than 50 times less than the legal limit. The bottom line, Plasmacluster Ion Air Purfiers work much better at cleaning the air than the competition, and do not produce dangerous amounts of ozone in the process. The reality is that there are a wide range of electrical appliances that give off ozone. Health Canada has established two basic guidelines in regards to ozone. #1 - You cannot use ozone as a means of air purification. #2 - Incidental production of ozone cannot exceed 0.05 ppm (parts per million). Again, our Plasmacluster Ion air purifiers generate less than 0.001 ppm, which is more than 50 times less than the legal limit.
Here's a link to a Sharp web site that describes the technology involved, including videos and such for what it's worth... http://www.sharp.ca/products/ion/plasma_2.asp