Abstract
Unconventional natural gas development uses horizontal drilling in conjunction with
hydraulic fracturing to gain access to natural gas deposits which may be tightly held
in shale deposits and unavailable to conventional vertical drilling operations. The
intensive work required to extract this source of energy results in higher than usual
numbers of vehicles involved, potential release of emissions from those vehicles in
congested zones surrounding the drill site, and release of other contaminants from
materials drawn back out of the borehole after fracturing of the shale. Typical contaminants
would be diesel exhaust particulate and gases, volatile organic compounds and other
hydrocarbons both from diesels and the drilling process, crystalline silica, used
as part of the hydraulic fracturing process in kiloton quantities, and methane escaping
from the borehole and piping. A rise in respiratory disease with proximity to the
process has been reported in nearby communities and both silica and diesel exposures
at the worksite are recognized respiratory hazards. Because of the relatively short
time this process has been used to the extent it is currently being used, it is not
possible to draw detailed conclusions about the respiratory hazards that may be posed.
However, based on the traffic volume associated with each drill site and the number
of drill sites in any locale, it is possible at least to compare the effects to that
of large traffic volume highways which are known to produce some respiratory effects
in surrounding areas.
Keywords
VOCs - hydraulic fracturing - ultrafines - diesel exhaust
