=======================Electronic Edition========================
RACHEL’S HAZARDOUS WASTE NEWS #226
—March 27, 1991—
News and resources for environmental justice.
——
Environmental Research Foundation
P.O. Box 5036, Annapolis, MD 21403
Fax (410) 263-8944; Internet: erf@igc.apc.org
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TOXIC GASES EMITTED FROM LANDFILLS.
A recent report [1] from California state government takes a fresh
look at a problem that has been ignored for years: toxic gases
released from landfills. Solid waste landfills and hazardous
waste landfills both emit toxic gases into the surrounding air.
U.S. EPA (Environmental Protection Agency) published its opinion
back in 1982 that air pollution from landfills is a significant
problem but said it would have to ignore the problem because no
one knew how to get a handle on it.[2] So far as we know, EPA has
never said another word on the subject. University researchers
reported almost a decade ago that landfills emit airborne toxins
into the local environment, but until now no one has defined the
extent of the problem.
Under California state law (Health and Safety Code Section
41805.5) all solid and hazardous waste landfills must be tested
for toxic gas emissions. The California Air Resources Board
(CARB) selected 10 toxic gases for measurement; they selected
these particular gases because they are known to have ill effects
(particularly cancer) on humans who are exposed for extended
periods. The ten toxic gases they tested for are: vinyl chloride,
benzene, ethylene dibromide, ethylene dichloride, methylene
chloride, perchloroethylene, carbon tetrachloride,
1,1,1-trichloroethane (methyl chloroform), trichloroethylene, and
chloroform. In addition, landfill gas samples were also analyzed
for oxygen, nitrogen, methane, and carbon dioxide.
The CARB summarized their findings this way:
1) One or more of the 10 toxic chemicals could be measured in
gases emitted from 240 out of 356 landfills tested; in other
words, 67% of the tested landfills emitted one or more of the
toxic gases.
2) Hazardous waste landfills and municipal solid waste landfills
appeared to be similar in their ability to produce toxic gases.
3) In many cases, but not all, toxic gases escaping from
landfills could be measured at the property line, the legal
boundary of the landfill.
4) Methane at concentrations greater than the regulatory limit of
5% was found to be migrating offsite underground at approximately
20% of the landfills. Methane is a naturally-occurring gas
created by the decay of organic matter inside a landfill. As
methane is formed, it builds up pressure and then begins to move
through the soil, following the path of least resistance; often
it moves sideways for a time before breaking through to the
surface of the ground. Methane is lighter than air and is
flammable. If it enters a closed building and the concentration
builds up to about 15% in the air, a spark or a flame is likely
to cause a serious explosion. For this reason, landfill designers
sometimes install a set of pipes full of holes like a swiss
cheese to provide a known pathway for the methane to escape
through; such systems are sometimes successful and sometimes not.
The new California study does not go into great detail, but it
certainly provides evidence that toxic gases are likely to be
measurable in the air near landfills. For example, of 340
California landfills studied, more than half had measurable
airborne releases of benzene (average: 2.5 parts per million
[ppm]), methylene chloride (average: 4.8 ppm), perchloroethylene
(average: 1.1 ppm), 1,1,1-trichloroethane (average 650 parts per
billion [ppb]), and trichloroethylene (average: 840 ppb). Nearly
half had releases of vinyl chloride (average: 2.2 ppm). Methane
was found at three quarters of all landfills tested. At half of
these, the concentration was 10% or less. In the other half, the
concentration varied from 11% to 73%. These were measurements at
the ground surface of the cap of the landfill.
Another set of measurements was taken at the property boundary of
each of 288 landfills, to see if toxic gases could be detected in
the “ambient” outdoor air. At 57% of these landfills,
1,1,1-trichloroethane was detected (maximum: 51 ppb); at 49%,
perchloroethylene was detected (maximum: 269 ppb); at 45%,
methylene chloride (maximum: 1.3 ppm); at 40%, benzene (maximum:
500 ppb); at 32%, trichloroethylene (maximum: 130 ppb); at 22%,
carbon tetrachloride (maximum: 15 ppb); at 13%, chloroform
(maximum: 32 ppb).
In all, off-site migration of gases, including methane, was
detected at 83% of all the 288 landfills. It’s enough to make you
think twice before buying a home near a landfill, or before you
sit by silently while someone else builds a new landfill near
your home, farm, church, or school.
Actually, this is not the first time landfill gas emissions have
been reported–it’s just the first time anyone has looked at
several hundred landfills to see how they behave in general. A
Princeton University study of the Monument Street Landfill in
Baltimore[3] reported in 1983 that toxic gases were escaping
through the methane venting system, which had been installed to
prevent methane from escaping through the cracks in Baltimore
streets. Toxic gases were escaping right along with the methane
(which had a concentration of 7%), in the following peak
concentrations: 1,1-dichloroethane (3.9 ppm);
1,1,1-trichloroethane (1.1 ppm); trichloroethylene (4.9 ppm);
ethylbenzene (10.4 ppm). In that study, a Gaussian air pollution
dispersion model was used to gauge the human exposure, which was
estimated to be 7 micrograms of ethylbenzene per cubic meter of
air 100 yards downwind from the landfill property line, and 0.14
micrograms of ethylbenzene per cubic meter of air 1000 yards
downwind from the property line (assuming stable atmospheric
conditions). These are not trivial exposures-especially near a
landfill surrounded by a residential community. Proposals to
“flare” the methane (set it on fire and allow it to burn
continuously) were considered but were rejected until such time
as a proper study could be done to learn what additional toxic
byproducts would be created by the flame. Such a study was never
done. James Craner[4] has described a study conducted in 1983 by
the New Jersey Department of Environmental Protection (DEP) at
Waste Management’s Parklands Landfill in Bordentown, NJ, in which
the DEP measured toxic gases inside a high school near the
landfill. Craner also described methods and apparatus suitable
for measuring toxic air emissions from landfills, so that any
unit of government that became interested in the problem could
take its own measurements. The system does require access to a
gas chromatograph/mass spectrometer (GC/MS). Except for that
critical (and expensive) piece of equipment, Craner’s system of
measurement is relatively inexpensive.
–Peter Montague, Ph.D.
Descriptor terms: ca; california; landfills; toxic emissions;
epa; carb; MSW; hazardous waste landfills; studies; methane;
james craner; nj dep;