Among the several layers of the Earth’s atmosphere lies thestratosphere, where most of the atmospheric ozone is known to be concentrated.Since a molecule of ozone contains three unstable oxygen atoms, they areconstantly being formed and re-formed. But research studies have shown thatozone levels have remained, more or less, constant, over the last few decades. https://www.evolving-science.com/environment/banned-chemical-depleting-earths-ozone-study-00672