Draft Environmental Impact Statement for Roca Honda Mine

Chapter 3. Affected Environment and Environmental Consequences
anemia, as well as fetuses. Healthy people exposed to high CO concentrations can experience
headaches, dizziness, fatigue, unconsciousness, and even death. Such concentrations occur in
enclosed spaces containing combustion products and are not found outdoors during normal
conditions.
Nitrogen Dioxide
Nitrogen dioxide (NO2) is a reddish brown gas that is a byproduct of combustion processes.
Automobiles and industrial operations are the main sources of NO2. Aside from its contribution
to ozone formation, NO2 can increase the risk of acute and chronic respiratory disease and reduce
visibility. NO2 may be visible as a coloring component of a brown cloud on high pollution days,
especially in conjunction with high O3 levels. The only sources of NO2 for the proposed project
are the diesel generators and mobile sources burning gasoline or diesel fuel.
Ozone
Ozone (O3) is not emitted directly into the environment, but is formed in the atmosphere by
complex chemical reactions between NOx and VOCs in the presence of sunlight. O3 formation is
greatest on warm, windless, sunny days. The main sources of NOx and volatile organic
compounds (VOCs), often referred to as ozone precursors, are combustion processes (including
motor vehicle engines) and the evaporation of solvents, paints, and fuels. As with CO,
automobiles are the single largest source of ozone precursors. O3 levels usually build up during
the day and peak in the afternoon hours. Short-term exposure can irritate the eyes and cause
constriction of the airways. Besides causing shortness of breath, it can aggravate existing
respiratory diseases such as asthma, bronchitis, and emphysema. Chronic exposure to high O3
levels can permanently damage lung tissue, plants and trees, and materials such as rubber and
fabrics.
Particulate Matter
Particulate matter 10 microns or less in aerodynamic diameter and 2.5 microns or less in diameter
(PM10 and PM2.5) refer to a wide range of solid or liquid particles in the atmosphere, including
smoke, dust, aerosols, and metallic oxides. Some particulate matter, such as pollen, is naturally
occurring. However, most particulate matter is caused by combustion, construction, grading,
demolition, agricultural activities, and motor vehicles. Extended exposure to particulate matter
can increase the risk of chronic respiratory disease. Inhalable coarse particles, such as those found
near roadways and dusty industries, are larger than PM2.5 and typically smaller than PM10. Fine
particles (PM2.5), as defined by EPA, include smoke and haze and are a subset of PM10. These
particles can be directly emitted from sources such as forest fires, or they can form when gases
emitted from combustion equipment, industries, and automobiles react in the air.
PM10, which includes PM2.5, is of concern because it bypasses the body’s natural filtration system
more easily than larger particles and can lodge deep in the lungs. PM2.5 is so small it behaves
much like a gas and can bypass all of the human body’s defenses to reach the deepest portions of
the lungs where oxygen is absorbed.
As with CO and ozone precursors, motor vehicles constitute the single largest source of PM10.
Motor vehicles produce particulates through direct tailpipe emissions of particulate matter; direct
182 DEIS for Roca Honda Mine, Cibola National Forest