CO enters the bloodstream and reduces oxygen delivery to the body's organs and tissues. The health threat from CO poisoning is most serious for those who suffer from cardiovascular disease. Healthy individuals are also affected, but only at higher levels of exposure to CO poisoning. Symptoms related to CO poisoning include visual impairment, reduced work capacity, reduced manual dexterity, poor learning ability, and difficulty in performing complex tasks.
Nature and Sources of the Pollutant
Trends in Carbon Monoxide Levels
Carbon Monoxide (CO)
Nature and Sources of the Pollutant:
Carbon monoxide is a colorless, odorless, poisonous gas formed when
carbon in fuels is not burned completely. It is a byproduct of highway
vehicle exhaust, which contributes about 60 percent of all CO emissions
nationwide. In cities, automobile exhaust can cause as much as 95
percent of all CO emissions. These emissions can result in high
concentrations of CO, particularly in local areas with heavy traffic
congestion. Other sources of CO emissions include industrial processes
and fuel combustion in sources such as boilers and incinerators. Despite
an overall downward trend in concentrations and emissions of CO, some
metropolitan areas still experience high levels of CO.
Carbon monoxide enters the bloodstream and reduces oxygen delivery to
the body's organs and tissues. The health threat from exposure to CO is
most serious for those who suffer from cardiovascular disease. Healthy
individuals are also affected, but only at higher levels of exposure.
Exposure to elevated CO levels is associated with visual impairment,
reduced work capacity, reduced manual dexterity, poor learning ability,
and difficulty in performing complex tasks. EPA's health-based national
air quality standard for CO is 9 parts per million (ppm) measured as an
annual second-maximum 8-hour average concentration.
Trends in Carbon Monoxide Levels:
Long-term improvements continued between 1986 and 1995. National average
CO concentrations decreased 37 percent while CO emissions decreased 16
percent. Long-term air quality improvement in CO occurred despite a 31
percent increase in vehicle miles traveled in the U.S. during the past
10 years. Between 1994 and 1995, national average CO concentrations
decreased 10 percent, while total CO emissions decreased 7 percent.
Transportation sources (includes highway and off-highway vehicles) now
account for 81 percent of national total CO emissions.
Environmental Protection Agency
The information provided on
this page is based upon the EPA current scientific and
technical understanding of the issues presented. Following the advice given
will not necessarily provide complete protection in all situations or
against all health hazards that may be caused by indoor air pollution and
other indoor environmental contaminants.
The EPA have not reviewed or
approved all the information and documents on indoor air quality that may be
provided by other groups or organizations.
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