Coal tar

Chemical Properties

The term “coal tar products,” as used by NIOSH, includes coal tar and two of the fractionation products of coal tar, creosote and coal tar pitch, derived from the carbonization of bituminous coal. Coal tar, coal tar pitch, and creosote (coal tar creosote 8001-58-9) derived from bituminous coal often contain identifiable components which by themselves are carcinogenic, such as benzo(a) pyrene, benzanthracene, chrysene, and phenanthrene. Other chemicals from coal tar products, such as anthracene, carbazole, fluoranthene, and pyrene may also cause cancer,but these causal relationships have not been adequately documented. Also, the research chemical methylcholanthrene (CAS: 56-49-5), a powerful carcinogen, fits this category. Coal tar pitch is a black viscous liquid. Aromatic solvent odor. Boiling point =>260°C; specific gravity (H2O:1) = 1.07-108; freezing/melting point = 250-°180C;flash point = 207°C (coal tar pitch); 74C (creosote oil);autoignition temperature =>510°C. Insoluble in water.Coal tar creosote (8001-58-9, crosote) is an black oily,tar-like substance. Pungent odor

Uses

Coal tar pitch is used as a base for paints and coatings, as a binder for carbon electrodes, for impregnating fiber pipe, in briquetting coal, in foundry core compounds, as a plasticizer for elastomers and polymers, as extenders, saturants, impregnants, and sealants, and in paving and roofing. Occupations with potential exposures to coal tar, coal tar pitch.

Definition

coal tar: A tar obtained from the destructivedistillation of coal. Formerly,coal tar was obtained as a byproductin manufacturing coal gas.Now it is produced in making cokefor steel making. The crude tar containsa large number of organiccompounds, such as benzene, naphthalene,methylbenzene, phenols,etc., which can be obtained by distillation.The residue is pitch. At onetime coal tar was the major source oforganic chemicals, most of which arenow derived from petroleum andnatural gas.

Hazard

A human carcinogen. Toxic by inhalation. Combustible.

Health Hazard

Epidemiological evidence suggests that workers intimately exposed to the products of combustion or distillation of bituminous coal are at increased risk of cancer at many sites, including lungs, kidney, and skin.
The chemical composition and particle size distribution of coal tar pitch volatiles (CTPV) from different sources are significant variables in determining toxicity.

Safety Profile

Confirmed carcinogen with experimental carcinogenic and neoplastigenic data by skin contact. When heated to decomposition it emits acrid smoke and fumes.

Potential Exposure

The coke-oven plant is the principal source of coal tar. The hot gases and vapors produced during the conversion of coal to coke are collected by means of a scrubber, which condenses the effluent into ammonia, water, crude tar, and other by-products. Crude tar is separated from the remainder of the condensate for refining and may undergo further processing. Employees may be exposed to pitch and creosote in metal and foundry operations; when installing electrical equipment; in construction, railway, utility; and briquette manufacturing.

Carcinogenicity

The history of coal tar cancers begins with the observations of scrotal cancer in London chimney sweeps by Percivall Pott in 1777. Since that time, a large body of evidence has accumulated demonstrating that workers involved in carbonizing bituminous coal, those handling certain by-products, or those exposed by inhalation of coal tar pitch volatiles are at excess risk of scrotal and other forms of skin, respiratory, and other types of cancer. Coal tar contains many substances that can cause cancer and is a human carcinogen. The toxicity of coal tar may vary with its origin.

Shipping

UN1136 Coal tar distillates, flammable, Hazard Class: 3; Labels: 3-Flammable liquid

Incompatibilities

Incompatible with strong oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Keep away from alkaline materials, strong bases, strong acids, oxoacids, epoxides. Phenols, such as creosote react as weak organic acids. Phenols and cresols are much weaker as acids than common carboxylic acids (phenol has pKa = 9.88). These materials are incompatible with strong reducing agents such as hydrides, nitrides, alkali metals, and sulfides. Flammable hydrogen gas is often generated, and the heat of the reaction may ignite the gas. Heat is also generated by the acid-base reaction between phenols and bases. Such heating may initiate polymerization of the organic compound. Phenols are sulfonated very readily (e.g., by concentrated sulfuric acid at room temperature). The reactions generate heat. Phenols are also nitrated very rapidly, even by dilute nitric acid

Waste Disposal

Dissolve or mix the material with a combustible solvent and burn in a chemical incinerator equipped with an afterburner and scrubber. All federal, state, and local environmental regulations must be observed.

Raw materials

Preparation Products