A cigarette filter is designed to serve as a mouthpiece and trap particulate matter from inhaled smoke. It acts as a physical barrier, preventing loose tobacco from entering the mouth and slightly reducing the harshness of the smoke. When the burning tobacco reaches the filter, the material is subjected to temperatures far exceeding its intended use, initiating thermal decomposition and melting. This transforms the filter from a passive barrier into an active source of concentrated thermal and chemical hazards.
The Composition of a Cigarette Filter
Modern cigarette filters are composed almost entirely of cellulose acetate, a synthetic plastic. This material is a derivative of cellulose, chemically modified to create a fibrous plastic tow. A single filter contains thousands of tightly packed, microscopic fibers, often with a Y-shaped cross-section designed to maximize surface area for trapping particles.
To hold the fibers together and provide firmness, a plasticizer, most commonly triacetin (glycerol triacetate), is incorporated. Triacetin typically makes up between six and nine percent of the filter’s total weight. This compound bonds the plastic fibers, ensuring the filter does not collapse during manufacturing or while being smoked.
Immediate Physical Effects of Burning the Material
When the glowing ember reaches the cellulose acetate, the material does not simply burn like tobacco or paper. Cellulose acetate begins melting around 230 degrees Celsius, causing it to soften and liquefy before full combustion. The filter material rapidly collapses under the heat, a process known as thermal degradation.
The melting plastic transfers intense, concentrated heat directly to the lips and mouth. This sudden influx of heat, combined with acrid fumes from the material breakdown, triggers an immediate physical rejection response. This sensation often results in an involuntary cough or gag reflex, which is the body’s attempt to reject the heating plastic and chemical vapors.
Toxic Chemicals Released Upon Combustion
Inhaling smoke from a burning cellulose acetate filter exposes the respiratory system to a highly concentrated mixture of toxic compounds, distinct from those in tobacco smoke. When the plastic fibers and additives are subjected to heat, they undergo pyrolysis, a chemical breakdown that generates Volatile Organic Compounds (VOCs). These VOCs are released directly into the smoke stream at high concentrations.
The thermal decomposition of the triacetin plasticizer is of particular concern, as it breaks down into highly toxic aldehydes. A confirmed byproduct is acrolein, a volatile and toxic compound known to cause severe irritation to the eyes and respiratory tract. Acrolein is a respiratory irritant that causes immediate damage to the lining of the throat and lungs.
The cellulose acetate base, being an acetate polymer, also contributes toxic substances to the smoke. The thermal breakdown of the acetate structure releases additional VOCs, which can include trace amounts of compounds like acetone, a known irritant. Inhaling these concentrated fumes can lead to chemical irritation or burns in the upper airway, resulting in inflammation and difficulty breathing. The process concentrates the release of these plastic-derived toxins and delivers them in a harsh, localized stream.