Ground level ozone also interferes with the ability of plants to produce and store food. It damages the leaves of trees and other plants, and contributes to a reduction in crop productivity, because the plants are more vulnerable to disease, pests, and harsh weather. Carbon monoxide (CO) is also a threat to the air we breathe. CO is formed when the carbon in fuel is not burned properly. The largest factor of CO emissions is automobiles. Cars, trucks, and buses account for 56% of the Earth’s carbon monoxide emissions. CO is.
