Nitrogen Dioxide (NO) and Sulfur Dioxide (SO2)
From:
Health Problems Caused By Other Combustion
Products
(Stoves, Space Heaters, Furnaces, Fireplaces)
Co-sponsored by: The American Lung Association (ALA),
The Environmental Protection Agency (EPA),
The Consumer Product Safety Commission (CPSC), and
The American Medical Association (AMA)
U.S. Gov't Printing Office Publication No. 1994-523-217/81322
1994
Nitrogen dioxide (NO) and sulfur
dioxide (SO2) act mainly as irritants,
affecting the mucosa of the eyes, nose, throat, and respiratory tract.
Acute S02-related bronchial constriction
may also occur in people with asthma or as a hypersensitivity reaction.
Extremely high-dose exposure (as in a building fire) to N02
may result in pulmonary edema and diffuse lung injury. Continued exposure
to high N02 levels can contribute to the
development of acute or chronic bronchitis.
The relatively low water solubility of N02
results in minimal mucous membrane irritation of the upper airway. The
principal site of toxicity is the lower respiratory tract. Recent studies
indicate that low-level N02 exposure may
cause increased bronchial reactivity in some asthmatics, decreased lung
function in patients with chronic obstructive pulmonary disease, and an
increased risk of respiratory infections, especially in young children.
The high water solubility of S02
causes it to be extremely irritating to the eyes and upper respiratory
tract. Concentrations above six parts per million produce mucous membrane
irritation. Epidemiologic studies indicate that chronic exposure to S02
is associated with increased respiratory symptoms and decrements in
pulmonary function21. Clinical studies have found that some
asthmatics respond with bronchoconstriction to even brief exposure to S02
levels as low as 0.4 parts per million22.
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