Ozone Standards Updated for First Time in 20 Years
In 1997, EPA updated the national air quality standards for ozone, after years of intensive scientific review determined that the old standards were not adequate to protect public health.
The new ozone standard moves from a one-hour standard of 0.12 ppm, to an 8-hour standard of 0.08 ppm. The change was necessary because scientific studies showed that ozone smog poses health problems when people are exposed to lower concentrations for longer periods of time, as occurs when children play outdoors.
The new standards have not yet been enforced, pending an EPA response to the courts on how the standards will be implemented.
When fully implemented, the new ozone standard will extend health protections to 35 million additional people, bringing total protection to more than 100 million Americans.
Meanwhile, the one-hour standard remains in force.
In 2001, EPA initiated its periodic five-year review of the ozone standards.
Ozone is the principle component of ground-level smog. It is formed when hydrocarbon and nitrogen oxide pollution from vehicles, power plants, refineries and other sources combine in the atmosphere in the presence of sunlight. Ozone is a powerful oxidizing agent that damages lung tissue.
Recent research with laboratory animals, clinical subjects, and human populations has identified a cascade of adverse health effects from ozone at levels common in the United States. Effects include increased respiratory symptoms, damage to cells of the respiratory tract, declines in lung function, increased susceptibility to respiratory infections, and increased risk of hospitalization and early death.
EPA revised the National Ambient Air Quality Standard (NAAQS) for ozone in 1997 because the health evidence showed that adverse health effects were experienced at lower concentrations than the earlier standard established in 1978.
· Short-term exposures to ozone can cause a decline in lung function, including rapid breathing, decreased lung volumes and flow, and increased twitchiness of the airways. Exposure early in life may lead to acceleration in the decline of lung function that is a normal process of aging.
· Respiratory symptoms can include coughing, throat irritation, shortness of breath, and pain on taking a deep breath. Asthmatics can experience wheezing, a hallmark of an asthma attack.
· When children with allergies and asthma are exposed to ozone, they can be more responsive to allergens that can trigger an asthma attack.
· Ozone triggers an inflammation response in the cells lining the lungs, causing them to rupture and leak. Repeated exposures may lead to structural changes in the respiratory tract including increased production of fibrous tissue associated with lung scarring.
· Ozone compromises the lung’s natural defense mechanisms, increasing susceptibility to respiratory infections such as colds, flu, and pneumonia.
· Short-term exposures are also associated with an increase in daily mortality, and increased hospital admissions and emergency department visits for respiratory causes. A recent risk assessment estimated that ozone sends 53,000 people to the hospital, 159,000 to the emergency room, and triggers 6,200,000 asthma attacks in the Eastern half of the United States each summer.
Four groups of people are especially sensitive to ozone:
· Children are at increased risk because their faster breathing rates means they take in proportionately more ozone than adults. Their exposure to ozone can also be high because they spend time playing outdoors in the summer months when ozone concentrations typically are highest. In addition, children’s respiratory systems are still undergoing development, so natural lung defense mechanisms aren’t fully mature.
· People with chronic obstructive respiratory disease (chronic bronchitis and emphysema) and asthma suffer the most from ozone air pollution. People with asthma, including children with asthma, are more likely to experience asthma attacks when exposed to ozone. This also results in increased use of medications, physician visits and emergency room and hospital admissions for asthma. People suffering from chronic bronchitis and emphysema are already struggling to breathe and can least afford additional breathing difficulties from exposure to ozone.
· Healthy adults who exercise or work outdoors have higher exposures and thus experience greater effects from ozone exposure. Joggers, bicyclists, hikers, and others that undertake moderate exercise outside, as well as construction workers, teachers, and letter carriers are included in this category of susceptible people.
· People with special sensitivity who are otherwise healthy can be significantly more responsive to ozone than other healthy individuals. Between five and twenty percent of the population falls within this category.
