What type of air pollution causes bleaching of leaves in plants?

Bleaching of leaves in plants is primarily caused by sulfur dioxide (SO2), which is a significant air pollutant. When sulfur dioxide is absorbed by plants, it can lead to a variety of physiological changes. The gas interferes with photosynthesis and can damage the chlorophyll, which is responsible for the green color in leaves. This damage often manifests as a bleaching effect, where the leaves lose their green pigmentation and can appear yellowish or whitish.

Sulfur dioxide is commonly released from sources such as fossil fuel combustion, industrial processes, and vehicle emissions, making it a critical pollutant to understand in the context of environmental health. By affecting plant health, sulfur dioxide not only impacts the flora in a specific area but can also disrupt local ecosystems and food chains.

The other options pertain to different forms of pollution or impacts on the environment but do not specifically lead to the bleaching of leaves in the way that sulfur dioxide does. For instance, while PAN (Peroxyacetyl Nitrate) can harm vegetation, sulfur dioxide is more directly associated with the specific symptoms of leaf bleaching.