Although fewer by-products are formed by ozonation, it has been discovered that ozone reacts with bromide ions in water to produces concentrations of the suspected carcinogen bromate.

For example, ozone reacts with the electron-rich 2-methylpropene about 100,000 times faster than the electron-poor tetrachloroethene (see reactivity scale below).

For all practical purposes, ozone does not react at all with such chemicals.

Second, for many of the chemicals with which ozone does readily react, the reaction can form a variety of harmful or irritating by-products (Weschler et al., 1992a, 1992b, 1996; Zhang and Lioy, 1994).

In the gas phase, ozone reacts with hydrogen sulfide to form sulfur dioxide:

When inhaled, ozone reacts with compounds lining the lungs to form specific, cholesterol-derived metabolites that are thought to facilitate the build-up and pathogenesis of atherosclerotic plaques (a form of heart disease).

Although few by-products are formed by ozonation, ozone reacts with bromide ions in water to produce bromate.

Ultraviolet light and ozone from these partial discharges (PD) then react with the nearby dielectric, decomposing and further degrading its insulating capability.

Because ozone reacts strongly with other molecules, high levels of ozone are toxic to living systems.

It is well established that when inhaled by mammals, ozone reacts with compounds in tissues lining the lungs and triggers a cascade of pathological effects.