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Re: another question ...landfill gases
Perhaps what Jon read was RACHEL's summary of TOXIC GASES EMITTED FROM
<<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.>>
Another earlier study found vinyl chloride in landfill leachate.
However, landfill gases were not mentioned. The study "An Estimation
of the Risk Associated with the Organic Constituents of Hazardous and
Municipal Waste Landfill Leachates," appeared in the journal, HAZARDOUS
WASTES AND HAZARDOUS MATERIALS, Vol. 5, No. 1 (Spring, 1988), pgs.
Peter Montague summarized this study in RACHEL's Hazardous Waste New #90