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APPENDIXES
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A
Origins of Complex Mixtures
COMBUSTION AND DISTILLATION PRODUCTS
Combustion and distillation products can consist of thousands of chemicals
from fossil- and synthetic-fuel sources, vegetable sources, or synthetic materi-
als. These mixtures generally contain a high percentage of organic chemicals,
including polycyclic aromatic compounds and aliphatic compounds, inorganic
materials, and metallic and nonmetallic salts. The mixtures can be heter-
ogeneous and consist of both volatile gases (e.g., CO, NOx, SO2, and form-
aldehyde) and semivolatile materials (e.g., two- and three-ring aromatic
compounds) and condensed organic and inorganic matter adsorbed on carbo-
naceous material.
Fossil FUELS
Coal
The opportunity for synthesis of hazardous chemicals exists whenever coal
is subjected to severe conditions, such as those of pyrolysis in the production of
coal tar and coal-tar pitch and those of hydrogeneration or gasification in the
production of synthetic fuels (McNeil, 19661.
In general, the physical characteristics of coal-tar pitch are measurable and
predictable. In chemical composition, coal-tar pitch is a highly complex or-
ganic material that varies from batch to batch, depending on temperature and
refining procedures. Polycyclic aromatic hydrocarbons (PAHs) are important
components of coal tar and coal-tar pitch and have been used as predictors of
potential hazards (Gray, 1984; Richards et al., 19791.
127
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128
APPENDIX A
Petroleum
Of the various petroleum fractions, asphalt, gasoline, heavy distillates, and
diesel fuels appear to be of most interest to the toxicologist (MacFarland et al.,
19841. The biologic activity of petroleum fractions does not correlate with
aromatic content, but rather might be due to the promoter activity of the
aliphatic fraction. Extracts of diesel-exhaust particles have been found to con-
tain aliphatic hydrocarbons, PAHs, nitroaromatics, and oxygenated PAHs;
much of the toxicologic research has focused on the nitroaromatics. The heavy
distillates and residues from catalytic cracking have been found to contain
PAHs and saturated hydrocarbons, which contribute to the carcinogenic activ-
ity of the materials.
Oil Shale
Oil shale undergoes thermal decomposition processes similar to those of
coal. The possibility of the synthesis of hazardous chemicals during pyrolysis
procedures exists. Raw shale and spent shale are not biologically active, but the
shale oil produced has been found to be very carcinogenic (Barldey et al.,
1979a,b; gingham and Barkley, 1979~. Shale-oil retort samples have been
found to contain a variety of PAHs in parts-per-billion concentrations. The
biologic activities of shale oils do not correlate with the concentrations of ben-
zoLa~pyrene in the samples.
SYNTHETIC FUELS
Major processes that have been used for coal liquefaction are pyrolysis,
hydrogenation, solvent refining, and Fisher-Tropsch synthesis. All those pro-
cesses involve harsh conditions that produce hazardous chemicals. All the
products-of hydrogenation high-boiling-point distillates, centrifuged oils,
char, residues, recycled solvent oil, recycled solvent, and liquid coal are po-
tentially hazardous. The synthetic coal liquids from all processes are higher in
PAH, basic, acidic, and insoluble fractions than are crude petroleum products.
The higher-boiling-point cuts appear to be enriched in PAHs and nitrogen- and
oxygen-containing molecules (Beland et al., 1985; Gray, 1984; Pelroy and
Wilson, 19811.
However, synthetic gas is not expected to pose a carcinogenic risk. Trace
elements, organic carcinogens, or cocarcinogens present can be removed from
the raw product during cleanup and scrubbing. In coal gasification, the conver-
sion process itself, rather than the fuel produced, should be the primary con-
cern. Potentially carcinogenic polycyclic organic material found during gasifi-
cation of coal is likely to concentrate in the tars, oils, char, quench waters, and
organic substances from gas-entrained particles. In addition, if the crude gas
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APPENDIX A
129
contains tars of high-boiling-point oils, they must be considered hazardous.
The tars contain high-molecular-weight polyaromatic species, which appear to
pose the greatest health concern (Richards et al., 1979~.
VEGETABLE SOURCES
Tobacco and wood are two major vegetable combustion sources. Tobacco
smoke is one of the most extensively studied complex mixtures. Hydrogena-
tion, pyrolysis, oxidation, decarboxylation, and dehydration are all involved in
tobacco combustion. The vapor phase of cigarette smoke contains nickel car-
bonyl, hydrazine, vinyl chloride, formaldehyde, and inorganic gases, such as
COx, NOx, and HCN (Hoffmann and Wynder, 1976; Hoffmann et al., 19761.
Cigarette-smoke condensate (CSC) contains aliphatic hydrocarbons, aromatic
hydrocarbons, phenols, and long-chain acids and alcohols, some of which are
cocarcinogenic (Van Duuren and Goldschmidt, 1976), tumor-promoting, and
tumor-inhibiting agents. Nitrosamines are present in sidestream smoke.
Thus, cigarette smoke contains many biologically active compounds. A va-
riety of fractionation procedures have been used to identify these components,
but, despite elaborate analytic procedures, it has been difficult to design toxi-
cologic strategies that address the many biologically active compounds present
in this very complex mixture.
Pyrolysis products of vegetable materials also have attributes in common
with materials isolated from cooked food.
SYNTHETIC MATERIALS
Combustion of synthetic materials—such as polyurethane foam, polyester,
polyethylene, polystyrene, and polyvinyl chloride results in the production
of many components (Levin, 1986) . Depending on the synthetic material used,
thermal-degradation products include aliphatic and aromatic hydrocarbons,
aliphatic amines, aldehydes, ketones, acids, and a mixture of toxic gases. The
acute toxicity of a material's combustion products can be explained by either
the interactions of major gases (e.g., CO, CO2, and HCN) or the pnma~y
thermal-degradation products.
NONCOMBUSTED MATERIALS
COAL DUST
Coal can be described as a compact stratified mass of vegetation, inter-
spersed with smaller amounts of inorganic matter, that has been modified
chemically and physically by agents over a very long time. The chemical prop-
erties of coal depend on the amounts and ratios of the vegetation's constituents,
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APPENDIX A
the nature and quantity of inorganic material, and the changes that the constitu-
ents have undergone. Coal has a complicated chemical structure based on car-
bon and hydrogen with various amounts of oxygen, nitrogen, and sulfur. Bitu-
minous coal, from which coal-tar pitch is derived, contains a number of PAHs
end toxic trace elements(Francis, 1961;Torrey, 19781.
01L SHALE
Health and environmental concerns have been raised in connection with oil-
shale extraction and processing. Blasting and mining produce dust, particulate
organic matter (POM), gases, hydrocarbons, silica, and metal salts. Crushing
and screening produce more dust, silica, and POM. Retort operations can also
produce polycyclic organic compounds, H2S, NH3, and volatile substances.
Some of those compounds, as well as arsenic and other metals, are produced in
the upgrading process, and disposal of the solid waste products is a major
environmental concern. Many of the compounds can contaminate both the
atmosphere and water. Because water is used in the oil-shale industry, many of
the compounds are found in the waste and runoff waters. Many potentially
hazardous chemicals might be present in the work area and environs. The
major health concern appears to be the carcinogenicity associated with fossil-
fuel production (Barkley et al., 1979a,b).
WASTE
Disposal of solid wastes produced in processing and extracting of fossil fuels
presents a major environmental problem. For example, the potential hazard to
workers who handle spent shale, which can contain substantial quantities of
silica and PAHs, should be of primary concern. The possibility that carcino-
gens will leach into the environment is also a concern. Spent shale might be
used in revegetation of disturbed land, so it is possible that products leached
from spent shale will be ingested by plants containing the contaminants.
Dump sites can contain hazardous chemicals from various sources. These
materials are usually very complex mixtures with nonpredictable chemical
composition. The source of materials at the dump site is often unknown, so the
analytic procedures are even more difficult. Municipal waste and sewage
waste, although complex, are somewhat more predictable.
WATER
Raw and finished surface and ground drinking waters contain carcinogenic,
mutagenic, and toxic chemicals. Industrial and municipal discharges, urban
and rural runoff, natural sources, and water and sewage chlorination practices
have been identified as possible sources of those pollutants (Menzer and Nel-
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APPENDIX A
131
son, 1986). In a surface dnnking-water sample, approximately 460 organic
compounds were identified, including 41 PAHs, 15 PCBs, and some amines,
amides, and halogenated species (Coleman et al., 1980), as well as a number of
inorganic chemicals. Knowledge and understanding of basic chemical princi-
ples is important in predicting the chemical composition of drinking water. For
example, chlonne, chlorine dioxide, and chloramine treatment processes have
been used for dnnking-water disinfection. Those practices have generated a
number of disinfectant byproducts from the reactions between background or-
ganic chemicals and chlonne.
REFERENCES
Barkley, W., D. Warshawsky, and M. Radike. 1979a. Toxicology and carcinogenicity of oil shale
products, pp. 79-95. In O. White, Jr. (ed.). Proceedings of the Symposium on Assessing the Indus-
trial Hygiene Monitoring Needs for Coal Conversion and Oil Shale Industries. Brookhaven National
Lab, Upton, N.Y. (Available from NTIS as BNL-51002.)
Barkley, W., D. Warshawsky, R. R. Suskind, and E. gingham. 1979b. Toxicology and carcinogenic
investigation of shale oil and shale oil products, pp. 157-162. In Oak Ridge National Laboratory.
Proceedings of the Symposium on Potential Health and Environmental Effects of Synthetic Fossil
Fuel Technologies, Gatlinburg, Tenn., September 25, 1978. Oak Ridge National Laboratory, Oak
Ridge, Tenn. (Available from NTIS as CONF-780903.)
Beland, F. A., R. H. Heflich, P. C. Howard, and P. P. Fu. 1985. The in vitro metabolic activation of
nitro polycyclic aromatic hydrocarbons, pp. 371-396. In American Chemical Society Monograph
283. American Chemical Society, Washington, D.C.
gingham, E., and W. Barkley. 1979. Bioassay of complex mixtures derived from fossil fuels. Environ.
Health Perspect. 30:157-163.
Coleman, W. E., R. G. Melton, F. C. Kopfler. K. A. Barone, T. A. Aurand, and M. G. Jellison. 1980.
Identification of organic compounds in mutagenic extract of a surface drinking water by a computer-
ized gas chromatography/mass spectrometry system (GC/MS/COM). 13nviron. Sci. Technol.
14:576-588.
Francis, W. 1961. Coal; Its Formation and Composition. Edward Arnold, London. (47 pp.)
Gray, R. H. 1984. Chemical and toxicological aspects of coal liquefaction and other complex mixtures.
Regulatory Toxicol. Pharmacol. 4:380-390.
Hoffmann, D., and E. L. Wynder. 1976. Environmental respiratory carcinogenesis, pp. 324-365. In
C. E. Searle (ed.). Chemical Carcinogens. American Chemical Society Monograph No. 173. Amer-
ican Chemical Society, Washington, D.C.
Hoffmann, D., C. Patrianakos, K. D. Brunnemann, and G. B. Gori. 1976. Chromatographic determi-
nation of vinyl chloride in tobacco smoke. Anal. Chem. 48:47-50.
Levin, B. C. 1986. A Summary of the NBS Literature Reviews on the Chemical Nature and Toxicity of
the Pyrolysis and Combustion Products from Seven Plastics: Acrylonitrile-Butadiene-Styrenes
(ABS), Nylons, Polyesters, Polyethylenes, PolysWrenes, Poly(Vinyl Chlorides) and Rigid Polyure-
thane Foams. NBSIR 85-3267. National Bureau of Standards, Gaithersburg, Md.
MacFarland, H. N., C. E. Holdsworth, J. A. MacGregor, R. W. Call, and M. L. Lane. 1984. Applied
Toxicology of Petroleum Hydrocarbons. Advances in Modern Environmental Toxicology, Vol. VI.
Princeton Scientific Publishers, Princeton, N.J. (287 pp.)
McNeil, D. 1966. Coal Carbonization Products. Pergamon Press, New York. (159 pp.)
Menzer, R. E., and J. O. Nelson. 1986. Water and soil pollutants, pp. 825-853. In C. D. Klaasen,
M. O. Amdur, and J. Doull (eds.). Casarett and Doull's Toxicology: The Basic Science of Poisons,
3rd ed. Macmillan, N.Y.
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APPENDIX A
Pelroy, R. A., and B. W. Wilson. 1981. Fractional Distillation as a Strategy for Reducing the Geno-
toxic Potential of SRC-II Coal Liquids: A Status Report. PNL-3787. Pacific Northwest Lab, Rich-
land, Wash. (Available from NTIS as DE 82002242.) (82 pp.)
Richards, D. E., W. P. Tolos, J. B. Lal, and C. V. Cooper. 1979. Tumors Induced in C3H/HeJ Mice by
Coal Tar Neutral Subfractions. DHEW (NIOSH) Publication No. 80-101. National Institute for
Occupational Safety and Health, Cincinnati, Ohio. (Available from NTIS as PB 80-175-854.)
Torrey, S., ed. 1978. Trace Contaminants from Coal. Pollution Technology Review No. 50. Noyes
Data Corporation, Park Ridge, N.J.
Van Duuren, B. L., and B. M. Goldschmidt. 1976. Cocarcinogenic and tumor-promoting agents in
tobacco carcinogenesis. J. Natl. CancerInst. 56:1237-1242.
Representative terms from entire chapter:
complex mixtures
