Chemical Hazard Explanation
Greenhouse gases describe chemicals that may increase the temperature of the Earth when present in sufficient quantities. Ozone is a molecule that forms smog near the ground, and it is formed by chemical reactions of greenhouse gases. Criteria pollutants are legally enforced by the Environmental Protection Agency; they include ozone and chemicals that pose public health threats when present in large quantities.
Adapted From: http://www.epa.gov/climatechange/ghgemissions/gases.html
Gases that trap heat in the atmosphere are called greenhouse gases. This section provides information on common greenhouse gases that are emitted from oil refineries and associated chemical plants.
- Carbon dioxide (CO2) : Carbon dioxide enters the atmosphere through burning fossil fuels (coal, natural gas and oil), solid waste, trees and wood products, and also as a result of some chemical reactions. Carbon dioxide is removed (or "sequestered") from the atmosphere when it is absorbed by plants.
- Methane (CH4) : Methane is emitted during the production and transport of coal, natural gas, and oil. Methane emissions also result from livestock and other agricultural practices and by the decay of organic waste in municipal solid waste landfills.
- Nitrous oxide (N2O) : Nitrous oxide is emitted during agricultural and industrial activities, as well as during combustion of fossil fuels and solid waste.
- Fluorinated gases: There are many types of fluorinated gases that act as powerful greenhouse gases when they are emitted from industrial processes. Fluorinated gases are sometimes used as substitutes for stratospheric ozone-depleting substances (e.g., chlorofluorocarbons (CFCs), hydrochlorofluorocarbons, and halons). Because these gases are potent even in small quantities, they are sometimes referred to as High Global Warming Potential gases ("High GWP gases").
Each gas' effect on climate change depends on three main factors:
How much of the gas is in the atmosphere?
Concentration, or abundance, is the amount of gas in the air. Larger emissions of greenhouse gases lead to higher concentrations in the atmosphere. Greenhouse gas concentrations are measured in parts per million, parts per billion, and even parts per trillion. One part per million is equivalent to one drop of water diluted into about 13 gallons of liquid (roughly the fuel tank of a compact car).
How long does a gas stay in the atmosphere?
Each gas can remain in the atmosphere for different amounts of time, ranging from a few years to thousands of years. Gases mix in the atmosphere, meaning that the amount of gas measured at one point in the atmosphere is roughly equivalent to the amount of gas located anywhere else in the world, regardless of the source of the emissions.
How strongly does a gas impact global temperatures?
Some gases are more powerful than others at trapping heat and "thickening the Earth's blanket." The Global Warming Potential (GWP) describes how long a gas remains in the atmosphere on average, and how strongly it absorbs energy. Gases with a higher GWP absorb more energy per pound and thus more greatly contribute to warming the Earth than gases with a lower GWP.
Adapted From: http://epa.gov/air/criteria.html
The Clean Air Act(1990) requires EPA to set National Ambient Air Quality Standards (40 CFR part 50) for pollutants considered harmful to public health and the environment. The Clean Air Act identifies two types of national ambient air quality standards. Primary standards provide public health protection, including protecting the health of "sensitive" populations such as asthmatics, children, and the elderly. Secondary standards provide public welfare protection, including protection against decreased visibility and damage to animals, crops, vegetation, and buildings. EPA has set National Ambient Air Quality Standards for six principal pollutants, which are called "criteria" pollutants. Units of measure for criteria pollutant standards are parts per million (ppm) by volume, parts per billion (ppb) by volume, and micrograms per cubic meter of air (µg/m3).
National Ambient Air Quality Standards (NAAQS)
- Final rule signed October 15, 2008. The 1978 lead standard (1.5 µg/m3 as a quarterly average) remains in effect until one year after an area is designated for the 2008 standard, except that in areas designated nonattainment for the 1978, the 1978 standard remains in effect until implementation plans to attain or maintain the 2008 standard are approved.
- The official level of the annual NO2 standard is 0.053 ppm, equal to 53 ppb, which is shown here for the purpose of clearer comparison to the 1-hour standard.
- Final rule signed March 12, 2008. The 1997 ozone standard (0.08 ppm, annual fourth-highest daily maximum 8-hour concentration, averaged over 3 years) and related implementation rules remain in place. In 1997, EPA revoked the 1-hour ozone standard (0.12 ppm, not to be exceeded more than once per year) in all areas, although some areas have continued obligations under that standard ("anti-backsliding"). The 1-hour ozone standard is attained when the expected number of days per calendar year with maximum hourly average concentrations above 0.12 ppm is less than or equal to 1.
- Final rule signed June 2, 2010. The 1971 annual and 24-hour SO2 standards were revoked in that same rulemaking. However, these standards remain in effect until one year after an area is designated for the 2010 standard, except in areas designated nonattainment for the 1971 standards, where the 1971 standards remain in effect until implementation plans to attain or maintain the 2010 standard are approved.
Ozone Forming Chemicals
Adapted From: http://www.epa.gov/airnow/aqi_brochure_08-09.pdf
What is ozone?
Ozone is a gas found in the air we breathe. Ozone can be good or bad, depending where it occurs:
Ozone is found at ground level and in the upper regions of the atmosphere (approximately 6 to 30 miles above the Earth's surface). Both types of ozone have the same chemical composition (O3). Upper atmospheric ozone protects the earth from the sun's harmful ultraviolet rays; ground level ozone forms a thick synthetic fog called smog.
Tropospheric, or ground level ozone, is created by chemical reactions between oxides of nitrogen (NOx), carbon monoxide (CO), and volatile organic compounds (VOC) in sunlight. Ozone is likely to reach unhealthy levels on hot sunny days in urban environments. Ozone travels long distances by wind, thus affecting areas that are not point sources. Emissions from industrial facilities and electric utilities, motor vehicle exhaust, gasoline vapors, and chemical solvents are some of the major point sources of NOx and VOC.
Who is most at risk?
Several groups of people are particularly sensitive to ozone. Because ozone levels are higher outdoors, outdoor physical activity causes faster and deeper breathing, drawing more ozone into the body.
- People with lung diseases such as asthma, chronic bronchitis, and emphysema, can be particularly sensitive to ozone. Ozone can aggravate their diseases, leading to increased medication use, doctor and emergency room visits, and hospital admissions.
- Children are at higher risk from ozone exposure because they often play outdoors and their lungs are still developing. In warm weather when ozone levels are higher, children are thus more likely to experience asthma or related difficulty with breathing.
- Older adults may be more affected by ozone exposure, possibly because they need more energy is needed to respire and they may have existing breathing problems.
- Active people of all ages who exercise or work vigorously outdoors are at increased risk.
- Some healthy people are more sensitive to ozone. They may experience health effects at lower ozone levels than the average person even though they have none of the risk factors listed above. There may be a genetic basis for this increased sensitivity.
In general, as concentrations of ground-level ozone increase, more people begin to experience more serious health effects. Everyone should be concerned about preventing and responding to high ozone exposure.
What are the health effects?
Ozone affects the lungs and respiratory system in many ways. It can:
- Irritate the respiratory system, causing coughing, throat soreness, airway irritation, chest tightness, or chest pain when taking a deep breath.
- Reduce lung function, making it more difficult to breathe as deeply and vigorously as you normally would, especially when exercising. Breathing may start to feel uncomfortable, and you may notice that you are taking more rapid and shallow breaths than normal. The risk of exposure to unhealthy levels of ground-level ozone is greatest during warmer months. Children, who often play outdoors in warmer weather, are at higher risk.
- Inflame and damage the cells that line the lungs. Within a few days, the damaged cells are replaced and the old cells are shed-much like the way your skin peels after sunburn. Studies suggest that if this type of inflammation happens repeatedly, lung tissue may become permanently scarred and lung function may be permanently reduced.
- Make the lungs more susceptible to infection. Ozone reduces the lung's defenses by damaging the cells that move particles and bacteria out of the airways and by reducing the number and effectiveness of white blood cells in the lungs.
- Aggravate asthma. Ozone also makes people more sensitive to allergens-the most common triggers for asthma attacks. Also, asthmatics may be more severely affected by reduced lung function and airway inflammation. People with asthma should ask their doctor for an asthma action plan and follow it carefully when ozone levels are unhealthy.
- Aggravate other chronic lung diseases such as emphysema and bronchitis. As concentrations of ground-level ozone increase, more people with lung disease visit doctors or emergency rooms and are admitted to the hospital.
- Cause permanent lung damage. Repeated short-term ozone damage to children's developing lungs may lead to reduced lung function in adulthood. In adults, ozone exposure may accelerate the natural decline in lung function that occurs with age.