1.Photochemical smog is a type of smog produced when ultraviolet light from the sun reacts with nitrogen oxides in the atmosphere. It is visible as a brown haze, and is most prominent during the morning and afternoon, especially in densely populated, warm cities.[2] Cities that experience this smog daily include Los Angeles, Sydney, Mexico City, Beijing, and many more.

2.Corrosion is a natural process that converts a refined metal into a more chemically stable form such as oxide, hydroxide, carbonate or sulfide. It is the gradual destruction of materials (usually a metal) by chemical and/or electrochemical reaction with their environment.

3.Stuart Monument, defaced during protests in Richmond, Virginia, was removed on July 7, 2020. The statue of Christopher Columbus at the Minnesota State Capitol moments after it was pulled from its pedestal by American Indian Movement protesters.

4.Ozone depletion is a major environmental problem because it increases the amount of ultraviolet (UV) radiation that reaches Earth's surface, which increases the rate of skin cancer, eye cataracts, and genetic and immune system damage.