Why the chemical is considered of concern:
Styrene is a colorless liquid, which is reacted with itself or other chemicals to produce polystyrene and synthetic plastic resins. The U.S. National Toxicology Program has classified styrene as a chemical reasonably anticipated to be carcinogenic to humans. Exposure to high levels of styrene in occupational settings has been associated with an increased risk for lymphohematopoietic cancers, which include leukemia and lymphoma. These cancers are characterized by abnormally high levels of white blood cells, which are thought to result from DNA mutations. In the human body, styrene is metabolized to styrene-7, 8-oxide, which has been shown to cause DNA damage in white blood cells. This damage is thought to result in chromosomal abnormalities in lymphocytes, a potential mechanism for styrene-induced cancer. Styrene exposure may also increase the risk for other cancers, including those of the esophagus and pancreas.
Styrene is hazardous if inhaled or ingested, and by means of skin or eye contact. Chronic exposure to styrene, or acute inhalation at high levels, negatively affects the nervous system. Changes in color vision, slowed reaction time, lethargy, headaches, memory deficits, hearing loss, and concentration and balance problems can occur and may be permanent. Styrene is also suspected to be toxic to the kidney, liver and respiratory system [pdf]. In animal studies, mice exposed to styrene developed lung tumors and nasal passage linings were damaged.
Styrene may be inhaled from off-gassing of building materials, tobacco smoke, photocopier fumes [pdf], and automobile exhaust. It is incorporated into a widely used polymerized plastic, polystyrene. While the polymer is non-toxic, styrene may leach from polystyrene containers into food at low levels. Styrene exposure has also occurred from drinking and bathing in contaminated water.
Occupational exposure occurs through inhalation and skin contact. Workers in the reinforced plastic, styrene-butadiene rubber, and styrene monomer and polymer industries are especially at risk for exposure. Workers in car, truck and boat fabrication industries are also likely to be exposed to high levels of styrene.
A cohort study of 17,924 workers in the styrene-butadiene rubber industry in North America found that leukemia-related mortality was elevated 16% compared to the general population. Cases of mortality were even higher among those having worked 20 or more years in the industry. Leukemia incidence was concentrated in those with jobs with a higher likelihood for chemical exposure. However, uncertainty remains about the specific chemical agent(s) that contribute to the increased leukemia incidence. In addition to styrene, workers could have also been exposed to the chemicals butadiene and dimethyldithiocarbamate.
Styrene is detected in air, water and soil as a consequence of its release from manufacturing processes involving styrene, as well as from the use and disposal of styrene-containing products. Styrene breaks down [pdf] in the air within one to two days and binds with ozone and hydroxyl radicals in the atmosphere. In bodies of water, styrene volatilizes quickly, and in soil, styrene is typically broken down by bacteria and microorganisms.
Where the chemical is found:
Styrene is used to manufacture polystyrene, a widely used category of plastic. Polystyrene is used in CD hard cases, plastic silverware and other rigid molded plastics. Polystyrene foams, like Styrofoam™, are commonly used for their insulating properties and are found in building and home maintenance materials, craft supplies, packaging peanuts and disposable coffee cups.
Styrene is also used to produce reinforced plastics and rubbers used in insulation (building construction and refrigeration equipment), pipes, automotive parts, tires, printing cartridges, food packaging and carpet backing. Trace amounts of styrene may also be found naturally in some foods.
Styrene is regulated by the Occupational Safety and Health Administration; worker exposure is limited to an average of 100 parts per million (ppm) over an 8-hour workday during a 40-hour work week. The US Food and Drug Administration regulates styrene in bottled drinking water; the concentration of the chemical may not exceed 0.1 milligrams per liter (mg/L).
Styrene is regulated as a contaminant under the Safe Drinking Water Act. The Environmental Protection Agency (EPA) has determined that exposure to styrene from drinking water is not expected to cause adverse health effects in children at concentrations at or below 20 mg/L for one day, or 2 mg/L for 10 days. EPA has also indicated that lifetime exposure to 0.1 mg/L styrene in drinking water is not expected to cause adverse effects. Styrene is listed under the EPA’s Emergency Planning and Community Right to Know Act (EPCRA), and as part of the Toxic Release Inventory, industries must report environmental releases and waste management of styrene.
What should be done:
You can play a role in limiting your exposure to styrene. Try to avoid inhaling cigarette smoke and car exhaust. Don’t microwave food or beverages or put hot drinks in polystyrene foam containers and cups. Heat may permit styrene monomers to leach from the polystyrene material and into your food or drink.
Workers who use styrene-containing materials can protect themselves from skin absorption of the substance by wearing protective gloves and clothing. Exposure by inhalation can be reduced with appropriate ventilation of the workspace.
But despite all personal measures, the significant potential for adverse health effects from exposure to styrene really demonstrates a larger problem: inadequate chemicals policy in the U.S. The current legislation, the Toxic Substances Control Act (TSCA), is flawed and limits the EPA’s authority to require chemical information from industry or ensure safe use. Through effective reform, like that presented in the Safe Chemicals Act, measures will be put in place to ensure the safety of all chemicals on the market and better inform and protect consumers from the harms of toxic chemicals. Show your support for smart, safe chemicals policies here.