• Smog causes plants to deplete, discolor and lose growth.niebla 2 image by Antoni Traver from Fotolia.com
  
  According to the textbook, "Environmental Science and Technology: A Sustainable Approach to Green Science and Technology," by Stanley E. Manahan, smog harms plants more than any other life form. People cannot rely on plants affected by smog to release fresh oxygen into the air. This is in addition to the effects of smog on humans, as smog causes a myriad health problems, including respiratory concerns and premature aging.
  
  

What Smog Is

• Smog is a mixture of chemical gases, both natural and manmade. It forms when there's a reaction between sunlight and airborne pollutants, and hence is at its peak in the summer. Up to ninety percent of smog is ozone that has dropped to ground level, while the rest includes nitrogen oxides, sulfur dioxide, acidic aerosols and volatile organic compounds (VOCs).
  
  

How Ozone Affects the Appearance of Plants

• Plants develop brown, black, or white spots when exposed to high levels of ozone in smog. They also experience depleted growth and quantity, so crops near major urban areas often don't grow as well as crops in rural areas. Plants may also develop very thin areas on leaves and age prematurely.
  
  

Ozone's Choking Effect

• Plants close the pores on their leaves so they won't lose water when they take in too much ozone. This also causes them to shrivel and die because no sugar or nourishment can be adsorbed.
  
  

The Effect of Nitrogen Oxides

• Even plants outside of urban areas, especially crops, are susceptible to the harmful effects of smog. The nitrogen oxides that turn into smog come primarily from grassland being burned for agricultural purposes. This is practiced in North America to a small degree, but is especially prevalent in tropical areas, where the intense sun also aides in the formation of smog.
  
  

Acid Aerosols and Plant Life

• Aerosol particles may be the most harmful components of smog to plant and animal life. Acidic aerosols include salts, metals, sulfuric acid droplets and chemicals known as polycyclic aromatic hydrocarbons commonly found in toxic or corrosive materials. If inhaled, acid aerosols can cause serious respiratory illness. For plants, the danger lies in aerosols falling as acid rain.
  
  

Hope for the Future

• A recent study by University of California Professor Daniel Gallie shows that vitamin C may help protect plants from smog. This may lead to the development of methods for plants to survive and thrive in cities, because urban areas are only expanding while farmland and wildlife conservations are becoming more scarce.