Nitrogen Oxides (NOx)
Nitric oxide (NO) and nitrogen dioxide (NO2) together are represented by NOx. Most of the emissions from combustion devices (approximately 90%) are in the form of NO.
NOx react in the air to form ground-level ozone and fine particulates, which are associated with adverse health effects.
- Short-term exposures (e.g., less than 3 hours) to low levels of NO2 may lead to changes in airway responsiveness and lung function in individuals with preexisting respiratory illnesses. These exposures may also increase respiratory illnesses in children.
- Long-term exposures to NO2 may lead to increased susceptibility to respiratory infection and may cause irreversible alterations in lung structure.
NOx contributes to a wide range of environmental effects directly and when combined with other precursors in acid rain and ozone.
- Increased nitrogen inputs to terrestrial and wetland systems can lead to changes in plant species composition and diversity.
- Direct nitrogen inputs to aquatic ecosystems such as those found in estuarine and coastal waters (e.g., Chesapeake Bay) can lead to eutrophication (a condition that promotes excessive algae growth, which can lead to a severe depletion of dissolved oxygen and increased levels of toxins harmful to aquatic life).
- Nitrogen, alone or in acid rain, also can acidify soils and surface waters.
Acid rain can ruin a fishing trip!
Acidification of soils causes the loss of essential plant nutrients and increased levels of soluble aluminum that are toxic to plants. Acidification of surface waters creates conditions of low pH and levels of aluminum that are toxic to fish and other aquatic organisms. NOx also contributes to visibility impairment.
Particulate Matter (PM)
Particles smaller than or equal to 10 µm (micro meter or millionth of a meter) in diameter can get into the lungs and can cause numerous health problems. Inhalation of these tiny particles has been linked with illness and death from heart and lung disease. Various health problems have been associated with long-term (e.g., multi-year) exposures to these particles. Shorter-term daily and potentially even shorter term peak (e.g., 1-hour) exposures to these particles can also be associated with health problems.
Particles can aggravate respiratory conditions, such as asthma and bronchitis, and have been associated with cardiac arrhythmias (heartbeat irregularities) and heart attacks. People with heart or lung disease, the elderly, and children are at highest risk from exposure to particles.
Particles of concern can include both fine and coarse-fraction particles, although fine particles have been more clearly linked to the most serious health effects.
- Particles larger than 2 micro meters (µm) do not penetrate beyond the nasal cavity or trachea.
- Particles smaller than 0.1 µm tend to deposit in tracheobronchia tree and are removed when exhaling.
- Particles between 0.1 and 2.0 µm penetrate deep into the lungs and settle in respiratory bronchioles or alveolar sacs
In addition to health problems, PM is the major cause of reduced visibility in many parts of the United States by scattering and absorbing some of the light emitted or reflected by the body reducing the contrast. Airborne particles can also impact vegetation and ecosystems, and can cause damage to paints and building materials.
How particulate matter is breathed into the human body
Instructions: See what happens when the name of each size of particulate matter is clicked on. (Note: The animation has no audio.)
Exposure to lead occurs mainly through inhalation of air and ingestion of lead in food, water, soil, or dust. It accumulates in the blood, bones, and soft tissues and can adversely affect the kidneys, liver, nervous system, and other organs.
- Excessive exposure to lead may cause neurological impairments such as seizures, mental retardation, and behavioral disorders.
- Even at low doses, lead exposure is associated with damage to the nervous systems of fetuses and young children, resulting in learning deficits and lowered IQ.
- Recent studies indicated that lead may be a factor in high blood pressure and subsequent heart disease.
- Lead can also be deposited on the leaves of plants, presenting a hazard to grazing animals and to humans through ingestion.
Instructions: Click the "play" button to see the impact of using unleaded rather than leaded gasoline. (Note: The animation has no audio.)