Gulf of Mexico Oil Spill Burnoff – Adverse Health Effects

Athough the current burning of the oil slick in the Gulf of Mexico  provides a faster solution for eliminating surface oil, it does provide it’s health challenges as well. 

Resource: NOAA 

Download PDF:  Health and Safety Aspects of “In-situ” Burning of Oil

Burning Efficiency
“In-situ burning has been studied under controlled conditions in laboratories and in field
tests, and recently under realistic conditions in an experiment off the coast of
Newfoundland, Canada. This experience indicated that in-situ burning can be an effective
oil-removing technique, removing 50 to 99 percent of the oil collected in the boom. In
addition, a field “real” burn conducted in the first days of the Exxon Valdez spill in Prince
William Sound, Alaska, resulted in the burning of 15,000 to 30,000 gallons of Prudhoe
Bay crude oil at an estimated efficiency of 98 percent or better (Allen 1990).”

Toxic Components of the Smoke Plume
The smoke emitted from oil combustion contains gases and particulates that may have
toxic effects on our bodies, much like exhaust emissions from motor vehicles or smoke
from wood stoves. The health risk will depend on the actual exposure to these agents.

Most of the oil in in-situ burning will be converted to carbon dioxide and water.
Particulates, mostly soot, comprise ten to fifteen percent of the smoke plume. Small
amounts of toxic gases are emitted as well. These include sulfur dioxide, nitrogen
dioxide, and carbon monoxide. In addition, small amounts of polynuclear aromatic
hydrocarbons (PAHs) are emitted from the fire, mostly as residues attached to the
particulates. These combustion by-products are discussed below, and their NAAQS and
occupational exposure limits are shown in Table 1.

Sulfur dioxide (SO2) is a gas formed when sulfur in the oil or hydrogen sulfide coming
out of a well oxidize during the combustion process. This gas is toxic and irritates the
eyes and respiratory tract by forming sulfuric acid on these moist surfaces (Amdur 1986).
The concentration of SO2 in the smoke plume depends on the sulfur content of the oil.
Average SO2 levels measured in experimental burns have been below 2 ppm in the plume
100-200 meters downwind of the burn (Fingas et al. 1993). Several miles downwind,
sulfur dioxide from in-situ burning is expected to be much below the level of concern for
the general population.

Nitrogen dioxide (NO2) is another gaseous by-product of oil combustion. Like SO2, it is
reactive, toxic, and a strong irritant to the eyes and respiratory tract. NO2 is less soluble
than SO2 and therefore may reach the deep portions of the lungs (the critical gas
exchange area of the lungs) so that even low concentrations may cause pulmonary edema,
which may be delayed (Amdur 1986).

Sampling results to date indicate that the concentration of nitrogen dioxide in the plume
several miles downwind of the burn does not exceed several parts per billion (Ferek
1994). Therefore, it is not expected to pose a threat to the general public several miles
downwind of the burn.

Polynuclear aromatic hydrocarbons (PAHs) are a group of hydrocarbons characterized
by multiple benzene rings attached together. These compounds have very low vapor
pressures and are not very flammable (compared to other compounds found in crude
oils.) PAHs are found in the unburned oil as well as the smoke plume. Some PAHs are
known or suspected carcinogens. Target organs may include the skin (from chronic skin
contact with oils) or the lungs from inhalation of aerosol. Based on data from NOBE and
previous burns, most PAHs are burned in the fire, and their concentration in the oil
residue is higher than in the smoke plume (Fingas et al. 1994).

PAHs were found in barely detectable concentrations in the smoke from the Kuwaiti oil
fires (Campagna and Humphrey 1992). Low levels of PAHs were also detected in
experimental oil burns, (Mass Selective Detector, analytical sensitivity 0.01 mg/m3 air)
with levels in the plume less than 0.01 ppm (Fingas et al. 1994). Considering the low
level of PAHs detected so far, it is felt that they present only a small exposure hazard.
Carbon monoxide (CO) is a common by-product of incomplete combustion. The
toxicity of CO is acute and stems from its high affinity to the hemoglobin molecule in red
blood cells. CO will chemically displace oxygen from the blood and cause oxygen
deprivation in the cells of the body. In experimental burns the average level of CO in the
smoke plume over the duration of the burns (15 to 30 minutes) was found to be 1 to 5
ppm 150 meters downwind of the burns (Fingas et al. 1993).
Particulates in the smoke plume are considered by most health professionals to be the
main combustion product to investigate and monitor. Therefore, particulates will be
discussed in more detail.

Particulates are small pieces of solid materials (dusts, soot, fumes) or liquid material
(mists, fogs, sprays) that remain suspended in the air long enough to be inhaled. During
in-situ burning elemental carbon (soot) and hydrocarbons are emitted. Since these
particulates absorb light to a high degree, the smoke plume is usually black.
Particulate concentration is measured in several ways. A relatively accurate method
involves sampling with an air pump that draws air through a filter. Depending on pore
size, the filter may collect more than 99.9 percent of the particulates in the air. Real-time
instruments that can measure particulate concentration at the time of measurement are
also available; some are quite sensitive and accurate. They must be calibrated to the
particulates of concern, and may be affected by other aerosols such as water vapor.

REFERENCES
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