Expanded Polystyrene (EPS), often recognized by the trade name Styrofoam, is a lightweight material used extensively in packaging and insulation. The foam is largely composed of air, making it an excellent insulator. The remaining small percentage is a plastic called polystyrene. When this material is exposed to heat, such as from melting or burning, it releases toxic fumes that pose a danger to human health. Toxicity arises because thermal energy breaks down the plastic’s chemical structure, releasing volatile, hazardous building blocks into the air.
The Chemistry of Polystyrene Degradation
Expanded Polystyrene (EPS) is a synthetic polymer created from long chains of styrene monomer. While inert in its solid, room-temperature state, its chemical stability changes drastically when subjected to heat. Simple melting is a physical change that occurs at lower temperatures, causing the foam to collapse and potentially releasing residual monomers into food or the air.
The more severe danger comes from thermal degradation, or pyrolysis, which occurs at higher temperatures, such as those found in fires. During this process, the polymer’s strong carbon-carbon bonds break apart. The large polystyrene chains revert back into smaller, volatile organic compounds, creating a complex mixture of hazardous gaseous byproducts.
Key Toxic Compounds Released by Melting
Thermal degradation of polystyrene releases several toxic substances into the air. The most abundant is styrene monomer, the primary chemical building block of the plastic. Styrene is classified as a suspected human carcinogen and a neurotoxin that can negatively affect the nervous system.
Benzene, a known human carcinogen, is another dangerous aromatic hydrocarbon released during heating. Incomplete combustion also generates large amounts of carbon monoxide (CO). Carbon monoxide is an odorless, colorless gas that acts as a lethal asphyxiant. It displaces oxygen in the blood, leading to oxygen deprivation in the body’s tissues.
Burning polystyrene also releases polycyclic aromatic hydrocarbons (PAHs). These PAHs are known to be carcinogenic and can cause birth defects. The mixture of these volatile organic compounds (VOCs) creates a smoky, acrid plume that is irritating and hazardous to inhale.
Health Effects of Fume Exposure
Exposure to fumes from melting or burning polystyrene can lead to both immediate and long-term health consequences. Acute exposure typically causes irritation of the eyes, nose, and upper respiratory tract. Symptoms of immediate inhalation include coughing, throat irritation, and increased nasal secretions.
Higher levels of acute styrene exposure can quickly depress the central nervous system, leading to “styrene sickness.” This condition is characterized by nausea, headaches, dizziness, fatigue, and confusion. The presence of carbon monoxide in the fumes can also cause carbon monoxide poisoning. Symptoms of poisoning include severe headaches, weakness, vomiting, and loss of consciousness.
Long-term exposure, even at lower concentrations, carries a risk of chronic health issues. Studies indicate potential effects on the nervous system, including impaired short-term memory, hearing loss, and changes in color vision. Repeated exposure to benzene and styrene has been linked to an increased risk of lymphohematopoietic cancers, such as leukemia and lymphoma.
Safe Handling and Prevention
The simplest way to avoid exposure to these toxic fumes is to keep polystyrene products away from any source of heat. It is particularly important to avoid microwaving polystyrene containers, as heat can cause chemicals to leach into food before the foam physically melts. Food should always be transferred to a microwave-safe ceramic or glass container before reheating.
Polystyrene should never be burned in a campfire, fireplace, or incinerator as a method of disposal. Burning directly causes the release of toxic gases like carbon monoxide and styrene. For disposal, check with local waste management authorities, as many curbside recycling programs do not accept EPS. If accidental exposure occurs, immediately move to fresh air and ventilate the area thoroughly. If symptoms such as severe dizziness, persistent coughing, or confusion develop, seek emergency medical attention right away.