Harmful Effects of Smog

Smog adversely affects human health and comfort, plants, materials, and atmospheric quality. Each of these aspects is addressed briefly here. Ozone is the smog constituent that is generally regarded as being most harmful to humans, plants, and materials, although very small particles, oxidants other than ozone, and some of the noxious organic materials, such as aldehydes, are harmful as well. 

Materials that are adversely affected by smog are generally those that are attacked by oxidants. The best example of such a material is rubber, especially natural rubber, which is attacked by ozone. Indeed, the hardening and cracking of exposed natural rubber has been used to test for the presence of atmospheric ozone. 

The adverse toxic effects of ozone on crops are a major sustainability concern. This is especially true when coupled with adverse climate effects from human activities such as increased greenhouse gas emissions, heat, drought, and sunlight-obscuring particle emissions from increased urbanization. The areas most affected are those with rapidly growing populations and industrialization, with adverse effects on production of staple crops such as rice and wheat, giving rise to problems of food security. 

FIGURE 7.15 The leaf of a lemon tree afflicted with chlorotic stippling because of exposure to oxidants in a smoggy atmosphere. This condition, which can seriously damage vegetation, is characterized by bleached or yellow spots on the leaves. 

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