Asphalt is made of a compacted “aggregate” mixed with a “binder.” The aggregate takes the wear-and-tear of traffic while providing a nonskid surface. It comes from rock quarries, natural gravel, and/or soil. The binder is a type of cement that holds the aggregate together in place and provides waterproofing. It comes from the distillation of crude oil. To mix it with the aggregate, the binder is heated and thinned with other chemicals distilled from crude oil.

Some of these chemicals used to thin asphalt cement are classified as volatile organic compounds (VOCs), which are chemicals that contain carbon and readily evaporate into the air at room temperature. Common examples of VOCs include kerosene, chloroform, benzene, trichloroethylene, and perchloroethylene. Many VOCs are dangerous to human health. Inhaling air contaminated with VOCs can cause nose and throat irritation, headaches, nausea, and loss of coordination. Long-term exposure can cause more serious damage to the brain, liver, and kidneys. Some VOCs are also known to cause cancer in humans. Workers in facilities that make and mix asphalt are at the highest risk for health effects of exposure to VOCs. However, because VOCs diffuse through the air, people who live and work near these facilities could also be at risk.

VOCs aren’t only used in asphalt production; they’re also used in many industrial and commercial products. The US Environmental Protection Agency (EPA) estimates that VOCs are emitted by thousands of products. CHEJ has previously written about specific chemicals classified as VOCs: benzene, ethylbenzene, formaldehyde, trichloroethylene and perchloroethylene, toluene, and xylene.