Where is ozone harmful

In metropolitan areas of California, ozone concentrations frequently exceed existing health-protective standards in the summertime. Ozone is formed in the atmosphere through chemical reactions between pollutants emitted from vehicles, factories and other industrial sources, fossil fuels, combustion, consumer products, evaporation of paints, and many other sources.

Hydrocarbons and nitrogen oxide gases react in the presence of sunlight to form ozone. Hot, sunny, and calm weather promotes ozone formation.

Ozone has a very characteristic pungent odor, and it can sometimes be detected after lightning strikes or during electrical discharges. Individual humans vary in their ability to smell ozone; some people can smell it at levels as low as 0. The ozone that CARB regulates as an air pollutant is produced close to the ground level, where people live, exercise and breathe. A layer of ozone high up in the atmosphere is called stratospheric ozone.

Without the protection of the stratospheric ozone layer, plant and animal life would be seriously harmed. Air quality regulators are concerned about ozone pollution because of its effects on public health and the environment. Ozone can damage the tissues of the respiratory tract, causing inflammation and irritation, and result in symptoms such as coughing, chest tightness and worsening of asthma symptoms.

In addition, ozone causes substantial damage to crops, forests and native plants. Ozone can also damage materials such as rubber and plastics. Inhalation of ozone causes inflammation and irritation of the tissues lining human airways, causing and worsening a variety of symptoms.

Exposure to ozone can reduce the volume of air that the lungs breathe in and cause shortness of breath. Just as ground-level ozone can make it harder for people to breathe, it also makes it harder for plants to breathe.

EPA's Ozone National Ambient Air Quality Standards are intended to protect both human health and public welfare, which includes protecting vegetation. EPA has indicated that reducing ground-level ozone can have the following impacts on vegetation:. For more information on ground-level ozone and agriculture, click here.

Since , Central Texas has had ground-level ozone levels that are considered by EPA to be "unhealthy for sensitive groups" as early as March and as late as October. The months when high ozone is most common are between May and June and between August and October.

High ozone levels are less likely to occur on Sundays than any other day of the week due to lower mobile source emissions. The key difference between a high ozone day and a low ozone day is the weather. Weather conditions associated with high ozone include:. A large study published in found that children were more likely to suffer from hay fever and respiratory allergies when ozone and PM2.

Research shows lower levels of ozone cause harm. EPA released their latest complete review of the current research on ozone pollution in February The experts on the committee and EPA concluded that ozone pollution posed multiple, serious threats to health.

Their findings are highlighted in the box below. However, new research provides evidence that ozone can cause serious harm even at much lower levels. In a scientific paper, researchers provided further evidence in a nationwide study that older adults faced a higher risk of premature death even when levels of ozone pollution remained well below the current national standard.

Data updated as of January 31, Environmental Protection Agency. EPA, , Section 8. Who is more vulnerable to die from ozone air pollution? Air Pollution and Mortality in the Medicare Population. N Engl J Med. Relationship between visits to emergency departments for asthma and ozone exposure in greater Seattle, Washington.

Ann Allergy Asthma Immunol. Short-term associations between ambient air pollutants and pediatric asthma emergency department visits. Environ Res. Chronic exposure to ambient ozone and asthma hospital admissions among children. Environ Health Perspect. Jerrett M, Burnett RT, et al. Long-term ozone exposure and mortality. Ozone, oxidant defense genes, and risk of asthma during adolescence. Birth outcomes and prenatal exposure to ozone, carbon monoxide, and particulate matter: Results from the Children's Health Study.

Ozone is a molecule composed of three atoms of oxygen. Two atoms of oxygen form the basic oxygen molecule--the oxygen we breathe that is essential to life. The third oxygen atom can detach from the ozone molecule, and re-attach to molecules of other substances, thereby altering their chemical composition.

The same chemical properties that allow high concentrations of ozone to react with organic material outside the body give it the ability to react with similar organic material that makes up the body, and potentially cause harmful health consequences. When inhaled, ozone can damage the lungs. Relatively low amounts can cause chest pain, coughing, shortness of breath and throat irritation.

Ozone may also worsen chronic respiratory diseases such as asthma and compromise the ability of the body to fight respiratory infections. People vary widely in their susceptibility to ozone. Healthy people, as well as those with respiratory difficulty, can experience breathing problems when exposed to ozone. Exercise during exposure to ozone causes a greater amount of ozone to be inhaled, and increases the risk of harmful respiratory effects.

Recovery from the harmful effects can occur following short-term exposure to low levels of ozone, but health effects may become more damaging and recovery less certain at higher levels or from longer exposures US EPA, a, b. Manufacturers and vendors of ozone devices often use misleading terms to describe ozone. Terms such as "energized oxygen" or "pure air" suggest that ozone is a healthy kind of oxygen.

Ozone is a toxic gas with vastly different chemical and toxicological properties from oxygen. Several federal agencies have established health standards or recommendations to limit human exposure to ozone. These exposure limits are summarized in Table 1.

Table 1. Ozone Heath Effects and Standards. The phrase "good up high - bad nearby" has been used by the U. Environmental Protection Agency EPA to make the distinction between ozone in the upper and lower atmosphere. Ozone in the upper atmosphere--referred to as "stratospheric ozone"--helps filter out damaging ultraviolet radiation from the sun. Though ozone in the stratosphere is protective, ozone in the atmosphere - which is the air we breathe - can be harmful to the respiratory system.

Harmful levels of ozone can be produced by the interaction of sunlight with certain chemicals emitted to the environment e. These harmful concentrations of ozone in the atmosphere are often accompanied by high concentrations of other pollutants, including nitrogen dioxide, fine particles and hydrocarbons.

Whether pure or mixed with other chemicals, ozone can be harmful to health. Available scientific evidence shows that at concentrations that do not exceed public health standards, ozone has little potential to remove indoor air contaminants. Some manufacturers or vendors suggest that ozone will render almost every chemical contaminant harmless by producing a chemical reaction whose only by-products are carbon dioxide, oxygen and water.