Asphalt is a dark-brown complex mixture composed of hydrocarbons of different molecular weights and their non-me
tal derivatives. It is a kind of high-viscosity organic liquid, mostly in the form of liquid or semi-solid petroleum, with a black surface and soluble Carbon disulfide, carbon tetrachloride. Asphalt is a kind of organic cementing material that is waterproof, moisture-proof and anti-corrosion. Pitch can be mainly divided into coal tar pitch, petroleum pitch and natural pitch. Among them, coal tar pitch is a by-product of coking. Petroleum pitch is the residue after the distillation of crude oil. Natural asphalt is stored underground, and some form mineral layers or accumulate on the surface of the earth's crust. Asphalt is mainly used in industries such as coatings, plastics, rubber, and paving roads.
On October 27, 2017, the World Health Organization’s International Agency for Research on Cancer released the preliminary list of carcinogens. Asphalt, occupational exposure to oxidized asphalt and their emissions during roofing are included in the 2A list of carcinogens, occupations when paving Exposure to straight-run asphalt and its emissions, and occupational exposure to hard asphalt and its emissions when working with asphalt sand glue are included in the 2B category of carcinogens.
