Which one of the following is a wrong statement?

Ozone $\left(\mathrm{O}_3\right)$ is an isotope of oxygen which exists in so called ozone layer at a height of about $15-60 \mathrm{~km}$ in the middle and upper stratosphere and lower mesosphere. This ozone layer absorbs UV-rays of longer wavelength and protects life on Earth from damaging effects of these radiations. Ozone in the lower atmosphere (troposphere) is regarded as a pollutant.