Background on Ozone
  1. Mountain WatchWhat is ozone?
  2. Why is ozone higher on mountain tops?
  3. What are the impacts of ozone?

What are the impacts of ozone?

The US Environmental Protection Agency (EPA) posts warnings on high ozone days to "sensitive groups" to restrict their outdoor activity. "Sensitive groups" include "active children and adults and people with respiratory diseases such as asthma." Those "active" types – hikers, climbers, paddlers, joggers and bikers – use more oxygen and tend to stay out for longer periods, which increases exposure to ozone. The mountaintops that many hikers seek often have higher ozone levels than do lower elevations. Ozone levels on some peaks, for example, the Great Smokey Mountains, are often worse than those found in major U.S. cities.  The graphic below shows how increases in ozone concentration and total exposure time increase the level of health impacts.

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Hiker Health

What are the health effects of ozone? 
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Exposure to ozone results in coughing, wheezing, tightness in chest, difficulty breathing, and aggravated asthma
• Ozone works on your lungs much like a sunburn on your skin, affecting the cells within your lungs. Like a sunburn, ozone damage causes temporary inflammation
• Though effects are temporary, continued exposure can result in permanent damage
• Also increases sensitivity to allergens, aggravating asthma and wheezing. Recent studies indicate that ozone may actually induce asthma in children

Ecosystem Health

Ecosystem HealthOzone can enters plants through the leaves, just like other gases, where it can cause visible leaf injury, reduced photosynthetic capacity, increased respiration, premature leaf death, reduced growth, mortality and changes cell chemistry and diminished production of carbohydrates, the plants’ food. It also can negatively affects reproduction and growth of plants.  Some plants are more sensitive to ozone than others and different species have strategies to protect themselves from this highly reactive oxidant.  Similar to humans, the exposure time and maximum concentration factor in to how extensive the damage to individual plants is.