![[Ozone Molecule]](o3.gif)
Ozone
-- The Invisible Poison Ozone
-- The Invisible Poison Ozone is a poisonous form of oxygen that can damage both plant and animal tissue. The molecules forming this invisible, odorless gas contains 3 oxygen atoms --- O3. The oxygen we need to live contains 2 oxygen atoms per molecule. It may not seem like a big difference -- just one more atom per molecule -- but the effects of high ozone levels are considered a serious threat in our cities and at Sequoia and Kings Canyon National Parks.
A natural ozone layer high in the atmosphere blocks much of the sun's harmful ultraviolet radiation from reaching Earth. Unlike this protective layer, ozone near the Earth's surface can be very destructive. It forms when other chemicals in the air -- nitrogen oxides and hydrocarbons -- react in the presence of sunlight. Most nitrogen oxides and hydrocarbons come from car and truck exhaust; an estimated 60% of the ozone problem is due to vehicle emissions. Over 40% of these emissions are from diesel trucks and buses. Ozone is the most wide-spread air pollutant in our country and is the main ingredient in smog.
Ozone damages plants by interfering with photosynthesis, the process plants use to make food. Studies have found that 39% of the Jeffrey and ponderosa pine trees in Sequoia and Kings Canyon National Parks show some visible ozone injury. Tests on giant sequoia seedlings showed a significant decrease in photosynthesis and reduced growth at ozone levels 50% higher than what is already in the air.
Ozone injures the lungs of humans and other animals, decreasing their ability to fight infection and remove inhaled particles. Ozone can cause permanent lung damage, coughing, sinus inflammation, chest pains, scratchy throat, stinging eyes and general malaise. High concentrations are hazardous for people with heart and respiratory ailments. Most vulnerable are children, the elderly, and those with existing health problems.
The National Park Service keeps track of ozone levels at four places in these parks. During summer, ozone levels exceed the California Health Standard of 0.09 ppm (parts per million) an average of one out of every three days at low-elevation sites like Ash Mountain, and one out of every five days at mid-elevation sites like Grant Grove and the Giant Forest. Ozone levels at these park sites are often higher than in cities like Los Angeles. Continued research and monitoring will help to evaluate the extent of the problem. With this information, we can take appropriate actions to protect park ecosystems, and ourselves, from this invisible poison.
Learn more about air quality management throughout the National Park Service.
