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Many volatile organic compounds, or VOCs, are found in emissions from
burning coal, oil and gasoline and in evaporation at gasoline service
stations. These and other sources, such as solvents, cleaners and
paints, all contribute to the baseline level of different VOCs found in
outdoor air. Some VOCs are also released from tobacco smoke. VOCs are of
special concern because they photo-chemically react (in sunlight) to
cause ozone or smog. VOC levels in urban areas like New York City
fluctuate widely; large differences occur because of both location (near
idling cars or trucks vs. on the waterfront) and time (rush hour vs.
middle of the night).
EPA has created several programs to reduce VOC emissions from such large
urban sources as motor vehicles. More information on these programs can
be found at www.epa.gov/otaq.
Measurements of VOCs from World Trade Center smoke and associated
cleanup activities (vehicles and equipment) included background levels
from other baseline sources such as city traffic.
To protect workers at the site, EPA attempted to identify the highest
concentration levels of VOCs by taking samples lasting for a few
minutes. Some of these "grab samples," taken where smoke plumes were
seen at the work site, have shown concentrations up to 4000 times higher
than those taken in the surrounding streets. EPA and others have
provided workers with respirators and other protective gear. Used
properly, respirators can protect workers from exposure to VOCs and
other contaminants at the levels we found. EPA urges workers to use all
available protective gear.
VOCs dissipate quickly; grab samples outside the work zone showed
dramatically lower levels away from the work zone. Full-day air samples
have also been taken for many VOCs at eight sites, mainly along the
outer edge of the work zone. These measurements confirm the rapid
dissipation of VOCs away from the debris pile and illustrate that over a
full day, average VOC levels are much lower than those found in the
short-duration grab samples. These full-day air samples for all VOCs
are below our corresponding screening levels, which were set to protect
against significantly increased risks of cancer and other long term
health problems, and are based on continuous exposure for a year.
Of the volatile organic compounds we monitored, EPA analyzed benzene
first because we thought it had the greatest potential to be present at
levels above our screening level. Full benzene information is available on separate web pages.
As described below, we have also analyzed other VOCs.
Results as of mid-April, 2002:
EPA detected 51 VOCs. About half of them are hazardous air pollutants
(HAPs), also called toxic air pollutants, under the Clean Air Act.
Although we detected these pollutants, their generally low
concentrations outside of the work zone mean they pose little risk of
long-term health problems from the WTC cleanup effort. A handful of VOCs
were not detected in any air samples.
EPA continues to monitor and analyze these substances in the air
surrounding the WTC. We do not, however, expect future results to be
substantially different from the samples listed here. We will continue
to make subsequent sample results available here.
Additional details can be found at www.epa.gov/wtc/voc/addl_detls.html.
This map shows the locations of EPA VOC monitoring stations in
Manhattan. Select a station to view VOCs monitoring data.
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