Combustion-Derived Polycyclic Aromatic Hydrocarbons in the Environment—A Review

Associations between diet and cancer, ischemic heart disease, and all-cause mortality in non-Hispanic white California Seventh-day Adventists

The photomutagenicity of 16 polycyclic aromatic hydrocarbons (PAHs), all on the United States Environmental Protection Agency (US EPA) priority pollutant list, was studied. Concomitant exposing the Salmonella typhimurium bacteria strain TA102 to one of the PAHs and light (1.1 J/cm 2 UVA+2.1 J/cm 2 visible) without the activation enzyme S9, strong photomutagenic response is observed for anthracene, benz[ a ]anthracene, benzo[ ghi ]perylene, benzo[ a ]pyrene, indeno[1,2,3- cd ]pyrene, and pyrene. Under the same conditions, acenaphthene, acenaphthylene, benzo[ k ]fluoranthene, chrysene, and fluorene are weakly photomutagenic. Benzo[ b ]fluoranthene, fluoranthene, naphthalene, phenanthrene, and dibenz[ a , h ]anthracene are not photomutagenic. These results indicate that PAHs can be activated by light and become mutagenic in Salmonella TA102 bacteria. At the same time, the mutagenicity for all the 16 PAHs was examined with the standard mutagenicity test with 10% S9 as the activation system. Benzo[ b ]fluoranthene, benzo[ k ]fluoranthene, chrysene, acenaphthylene, and fluorene are weakly mutagenic, while the rest of the PAHs are not. In general, the photomutagenicity of PAHs in TA102 does not correlate with their S9-activated mutagenicity in either TA102 or TA98/TA100 since they involve different activation mechanisms.

Photomutagenicity of 16 polycyclic aromatic hydrocarbons from the US EPA priority pollutant list.

Review of the estrogenic and antiestrogenic activity of polycyclic aromatic hydrocarbons: Relationship to carcinogenicity

B[a]P (benzo[a]pyrene) has been used as a prototype carcinogenic PAH since its isolation from coal tar in the 1930's. One of its diol epoxides, BPDE-2, is considered its ultimate carcinogen on the basis of its binding to DNA, mutagenicity and extreme pulmonary carcinogenicity in newborn mice. However, BPDE-1 has a similar binding to DNA and mutagenicity but it is not carcinogenic. In addition, BPDE-2 is a weak carcinogen relative to B[a]P when repeatedly applied to mouse skin, the conventional assay site. Its carcinogenicity is increased when applied once as an initiator followed repeatedly by a promoter. This indicates a major role for promotion in carcinogenesis by PAHs. Promotion itself is a 2-stage process, the second of which is selective propagation of the initiated cells. Persistent hyperplasia underlies selection by promoters. The non-carcinogenicity of BPDE-1 has yet to be resolved. PAHs have long been considered the main carcinogens of cigarette smoke but their concentration in the condensate is far too low to account by themselves for the production of skin tumors. The phenolic fraction does however have strong promotional activity when repeatedly applied to initiated mouse skin. Several constituents of cigarette smoke are co-carcinogenic when applied simultaneously with repeated applications of PAHs. Catechol is co-carcinogenic at concentrations found in the condensate. Since cigarette smoking involves protracted exposure to all the smoke constituents, co-carcinogenesis simulates its effects. Both procedures, however, indicate a major role for selection in carcinogenesis by cigarette smoke. That selection may operate on endogenous mutations as well as those induced by PAHs. There are indications that the nicotine-derived NNK which is a specific pulmonary carcinogen in animals contributes to smoking-induced lung cancer in man. Lung adenoma development by inhalation has been induced in mice by the gas phase of cigarette smoke. The role of selection has not been evaluated in either of these cases.

Synergistic mechanisms in carcinogenesis by polycyclic aromatic hydrocarbons and by tobacco smoke: a bio-historical perspective with updates

Polynuclear aromatic compounds

1,170,222. Tetrahydrofurans. SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ N.V. 10 June, 1968, No. 27444/68. Heading C2C. A tetrahydrofuran of the general formula in which each R represents a hydrogen atom or a C 1 -C 5 alkyl group is prepared by (a) contacting a conjugated diolefin of general formula in an anhydrous, or substantially anhydrous, liquid medium, with a metal salt of an aliphatic carboxylic acid having 2-6 carbon atoms, together with a compound of divalent palladium, or with a divalent palladium salt of such a carboxylic acid alone; (b) separating from the reaction mixture one or more olefinically unsaturated 1,4-glycol acylates having the general formula in which at least one of the radicals R 1 and R 2 represents an acyl group having 2-6 carbon atoms, the other being the same or a hydrogen atom; (c) hydrogenating the ester obtained in (b) to give a saturated 1,4-glycol mono- and/or diacylate; and (d) converting the 1,4-glycol mono- and/or diacylate into the desired tetrahydrofuran, either directly by the action of an acidic catalyst in the presence of water or indirectly by first hydrolysing the mono- and/or diacylate and subsequently allowing the cyclization into the desired tetrahydrofuran to take place by methods known per se.

Process for the preparation of Tetrahydrofuran and/or Homologues thereof

Acyclic olefins are disproportionated in the presence of a suitable catalyst and molecular hydrogen The presence of hydrogen retards catalyst deterioration, promotes catalyst activity, and enables the process to be conducted without the need for removal of conjugated alkadiene contaminants from the feed By suitable adjustment of the amount of hydrogen and the type of catalyst, the olefin products can be simultaneously hydrogenated, either partially or completely Since hydrogenation of lower olefins under these conditions proceeds more easily than that of higher olefins, the process may be used to convert an alkene feed into a mixture of lower alkanes and higher alkenes Suitable catalysts contain one or more oxides, sulphides, p -alkenyl or carbonyl derivatives of molybdenum, tungsten or rhenium, supported on alumina or an admixture thereof with up to 25% of magnesia, thoria or silica A mixture of molybdenum trioxide and cobalt oxide on alumina is particularly suitable The selectivity of the catalyst may be increased by the presence of an oxide of potassium, rubidium or cesium, and the hydrogenating activity thereof by the presence of metallic Fe, Co, Mn, Ni, Pd, Pt, Rh or Ru, or an oxide, sulphide, p -alkenyl or carbonyl derivative thereof Numerous gaseous or liquid diluents are mentioned, and the process may be effected in the gaseous or liquid phase using any desired form of catalyst, eg fixed bed, fluidized bed or slurried Examples describe the conversion of propylene to ethylene and butene, or to ethylene, ethane and butene, and of butene-1 to a variety of product mixtures comprising mainly alkenes, mainly alkanes and various intermediate mixtures

Improvements in or relating to the disproportionation of alkenes

Preparation of alkenyl esters from alkenyl chlorides and metal carboxylates in the presence of palladous chloride

1,164,687. Disproportionation. SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ N.V. 15 June, 1967 [17 June, 1966], No. 27709/67. Heading C5E. The disproportionation of acyclic alkenes is carried out in the presence of a supported disproportionation catalyst which has been modified by the presence of a compound of potassium, rubidium or caesium (particularly an oxide or hydroxide), the support comprising at least 75 wt. per cent alumina. The catalyst suitably comprises an oxide, sulphide, #-alkenyl or carbonyl compound of molybdenum, tungsten or rhenium, and may be promoted by a compound of Co, Ni, V, Ti, Fe, Cr, Zr, Ta or Bi, particularly cobalt oxide. The support may be 100% Al 2 O 3 , or may contain up to 25% of thoria, magnesia or silica. The process may be carried out in the gas or liquid phase, and in the presence of a gaseous or liquid diluent. Water, oxygen, alkynes and dienes are preferably absent. Examples describe the disproportionation of propylene to ethylene and butenes; of butene-1 to mainly ethylene and hexene with some propylene and pentene; of n-octane-1 to a C 2-14 olefin mixture with ethylene and tetradecene predominating; and of n-dodecene to a C 2-22 olefin mixture with ethylene and C 22 olefin predominating.

Robert Van Helden

Papers

Polynuclear aromatic compounds

Process for the preparation of Tetrahydrofuran and/or Homologues thereof

Improvements in or relating to the disproportionation of alkenes

Preparation of alkenyl esters from alkenyl chlorides and metal carboxylates in the presence of palladous chloride

Disproportionation of alkenes