The pollutants generated by the cigarette arise from the chemical process of burning organic matter, or combustion of tobacco and paper. Combustion processes, such as wood burning or waste incineration, emit thousands of pollutants, some of which are in the gas phase and some of which are in the form of small particles called particulate matter.
Particulate matter consists of millions of tiny particles of diverse chemical composition. Particulate matter from tobacco smoke includes many particles in the size range that reflects light, which explains why tobacco smoke is easily seen by the eye. In contrast to smoke particles, gases emitted by the cigarette such as benzene and carbon monoxide (CO) are invisible to the eye. Particles smaller than 2.5 micrometers (PM2.5) are major components of cigarette smoke and can enter deep into the lung where they can cause serious health problems. To illustrate how small a PM 2.5 particle is, consider that 25,000 particles of this diameter, when placed side to side, can fit into 1 inch on a ruler.
Although a single cigarette is small in size and typically weighs less than 1 gram, a cigarette typically emits between 7 and 23 milligrams (mg) of PM2.5 when it is smoked, depending on the manner of smoking and the brand (see References 1 and 2 on the reference citation list). When people congregate in an airport baggage area or enter a smoking lounge where many brands are smoked, the average amount of PM2.5 mass emitted per cigarette is about 14 mg (see Reference 3). Although 14 mg may not seem like a lot of mass emitted, each cigarette weighs only about 0.9 grams total, making it an extremely potent source of air pollution for its weight.
As we shall see in subsequent chapters of this booklet, the 14 mg of particles emitted by each cigarette is really a large amount of particulate matter mass, causing extremely high indoor air pollutant concentrations when a cigarette is smoked at home or in a car. The chapter "Where does the smoke go?" presents calculations that you can do yourself to illustrate that a single cigarette smoked indoors is a potent source of exposure to toxic pollutants, causing concentrations indoors that are often higher than the federal air quality standards designed to protect public health in ambient air outdoors.