Technically this expert is correct given exactly what your question asked.
However, in consideration of the merits of ozone therapy, the medical community has recognized the antiviral and antibacterial properties of this gas for some time. In fact, it has long been used to sterilize surgical instruments.
During World War II, a topical formulation containing suspended ozone was often administered to the wounds of soldiers to deter infection. In more recent years, veterinarians use intravenous fluid ozone preparations to treat infection and decrease inflammation in animals.
In Germany, ozone generators are standard pieces of equipment in ambulances, which many claim has resulted in a lower occurrence of severe or permanent paralysis in stroke patients.
Skeptics of ozone therapy argue that the evidence supporting its therapeutic benefits is largely anecdotal, and point to the fact that ozone is a toxic gas classified as an environmental pollutant which presents health risks to those with cardiopulmonary and respiratory disorders. The strongest point of view against this therapy is a concern that ozone readily degrades into unstable oxygen atoms that will seek to gain electrons by pairing, or oxidizing, with other molecules.
Proponents of this form of therapy, however, maintain that ozone atoms retain their ion characteristics rather than behaving like free radicals. This means they will target and oxidize with molecules that lack glutathione peroxidase and other protective enzymes and destroy them, namely those found in foreign bacterial and viral cells.
Treatment with ozone involves very specific dosage concentrations and various methods of administration. These include autohemotherapy, or the reintroduction of ozone-infused blood, rectal, vaginal, or auricular insufflations, intramuscular injections, and ozonated water or steam. Topical applications consist of ozonated ointments or salves made from olive, hemp, or avocado oil.
In the U.S., the Food and Drug Administration (FDA) strictly prohibits claims that ozone therapy can prevent or cure any disease. However, the FDA permits the use of ozone as a germicide in the food processing industry and numerous states have adopted legislation making the medical use of ozone legal.
Ozone therapy is widely practiced in most European and Mediterranean countries.
Stating the ozone in a municipal potable water system is just plain false. While it is true that during a water break where the psi drops below the state required minimum there is a risk of contamination. This is why BOIL WATER ORDERS are put in action regardless of the treatment method used for disinfection. I suppose in a discussion of the dangers the lurk in water we could get into the whole problem with chlorine treatment and the production of large amounts of THMs especially in surface supplies...
On question #2 yet more misleading manipulation of the facts. It is "technically" correct again. However, depending on the method used to produce the ozone there is a great variation in the by-products generated. In the VUV system nitrogen oxides are a non-issue.