By Yervand Kondrahjian | Staff Writer
Butadiene: A Ubiquitous Toxin
By Yervand Kondrahjian, Staff Writer
1,3-butadiene (butadiene, or BD), a colorless gas, is an important petrochemical manufactured in high volumes. Butadiene is primarily used to produce synthetic rubber and thermoplastic resins. It was first identified and named in 1886 and isolated in 1910. The molecule can be viewed as the union of two vinyl groups (bivinyl).
In the United States, western Europe, and Japan, butadiene is produced as a byproduct of the production of ethylene and other alkenes. When mixed with steam and heated to very high temperatures (often over 900 °C), aliphatic hydrocarbons give up hydrogen to produce a complex mixture of unsaturated hydrocarbons, including butadiene. In other parts of the world, including South America, eastern Europe, China, and India, butadiene is also produced from ethanol. This process was the basis for the Soviet Union’s synthetic rubber industry during and after World War II, and it remained in limited use in Russia and other parts of eastern Europe until the end of the 1970s.
Human exposure to BD can be divided into two categories: occupational at industrial sites and non-occupational. In the fuels industries, it is formed as a byproduct of incomplete combustion of fossil fuels and biomass. It is also produced from industrial emissions as a result of manufacturing rubber and resins. As for non-occupational exposure, cigarette smoke contains significant amounts of BD and could thus be the primary source of this pollutant in indoor air (microenvironments). Other sources include automobile exhaust and cooking.
BD is a ubiquitous environmental pollutant and one of the volatile organic compounds monitored routinely in the ambient air. It was determined to be a human group 1 carcinogen by the U.S. Environmental Protection Agency (EPA) in 2002 and by the International Agency for Research on Cancer (IARC) in 2008. It is one of 187 hazardous air pollutants, also known as air toxics, as defined by EPA.
Butadiene and its metabolites are widely distributed throughout the body. They can readily react with nucleosides and DNA to yield DNA adducts, which are genotoxic and mutagenic. In other words, exposure to BD is genotoxic to humans and can cause chromosomal damage. Acute high exposures may cause damage to the central nervous system or cause symptoms such as distorted blurred vision, vertigo, general tiredness, decreased blood pressure, headache, nausea, decreased pulse rate, and fainting. Urine and exhaled air are the major routes of elimination of butadiene metabolites.
The Occupational Safety and Health Administration’s (OSHA’s) new limits reduce the permissible exposure limit (PEL) for BD to an 8-hour total weight average (TWA) of 1 ppm for occupational exposure. Further epidemiological studies and more regulations are needed to further promote the safety of the public.