Polynuclear aromatic hydrocarbons carbon black

IARC. 1984. lARC monographs on the evaluation of the carcinogenic risk of chemicals to humans Polynuclear aromatic hydrocarbons, part 2. carbon blacks, mineral oils (lubricant base oils and derived products) and some nitroarenes. Volume 33. Lyon. France World Health Organization, International Agency for Research on Cancer. 

NIOSH considers Carbon Black to be the material consisting of more than 80% elemental carbon, in the form of near-spherical colloidal particles and coalesced particle aggregates of colloidal size, that is obtained by the partial combustion or thermal decomposition of hydrocarbons. The NIOSH REL (10-hour TWA) for carbon black is 3.5 mg/m. Polycyclic aromatic hydrocarbons (PAHs), particulate polycyclic organic material (PPOM), and polynuclear aromatic hydrocarbons (PNAs) are terms frequently used to describe various petroleum-based substances that NIOSH considers to be potential occupational carcinogens. Since some of these aromatic hydrocarbons may be formed during the manufacture of carbon black (and become adsorbed on the carbon black), the NIOSH REL (10-hour TWA) for carbon black in the presence... 

Mixtures of gaseous or liquid hydrocarbons which can be vaporized represent the raw materials preferable for the industrial production of carbon black. Since aliphatic hydrocarbons give lower yields than aromatic hydrocarbons, the latter are primarily used. The best yields are given by unsubstituted polynuclear compounds with 3-4 rings. Certain fractions of coal tar oils and petrochemical oils from petroleum refinement or the production of ethylene from naphtha (aromatic concentrates and pyrolysis oils) are materials rich in these compounds. These aromatic oils, which are mixtures of a variety of substances, are the most important feedstocks today. Oil on a petrochemical basis is predominant. A typical petrochemical oil consists of 10-15% monocyclic, 50-60% bicyclic, 25-35% tricyclic, and 5-10% tetracyclic aroma tes. 

Fillers are materials that modify rubber characteristics (e.g., hardness) and improve its physical characteristics (e.g., tensile strength), in addition to reducing costs. Rubber is sometimes compounded without the use of fillers the resultant product is called gum rubber. Typical fillers are calcined and hydrated clays, magnesium silicate (talc), magnesium oxide, and silicas. Carbon black, a common filler used to increase the heat resistance in industrial components such as tires, is not used as a filler in pharmaceutical components but it is used in smaller amounts as a black pigment. Polynuclear aromatic (PNA) hydrocarbons are a concern with carbon blacks but the grades used by manufacturers of pharmaceutical components contain very low concentrations. 

Formation of gaseous carbon black precursors at high temperature. This involves dehydrogenation of primary hydrocarbon molecular species to atomic carbon or primary free radical and ions which condense to semisolid carbon precursors (or polynuclear aromatic sheet) and/or formation of large hydrocarbon molecules by polymerization, which then is dehydrogenated to particle precursors. 

Ordinary aromatic hydrocarbons do not have the low Characterization Factors of 10.1 to 10.8 although the coal-tar distillate cut between creosote and pitch (anthracene oil) is used widely in En and and Germany. The aromatics must be polynuclear aromatics and if any side-chains are present, these must be unsaturated. Almost ideal polynuclear aromatics are produced in the vapor-phase cracking of gases, but the amount is ve small (Table 20-3). The main sources of superior carbon black oils are 44... 

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