Tars are complex heterogeneous substances that are derived from a variety of sources. Any organic compound that is subjected to great heat, as in frying or roasting, undergoes decomposition with the formation of highly complex black tar. Most people are familiar with the tar formed in the burning of tobacco in cigarette, pipe and cigar. The bowl of the pipe and the pipe stem become clogged with the sticky, and foul smelling stuff.

Tar forms in coffee while it is being roasted; it forms in the cereals, beans and fruits when these are roasted in making coffee-substitutes. Coffee drinkers and drinkers of coffee substitutes daily take tar into their bodies just as the smoker gets tar into his mouth, throat, lungs and blood.

If potatoes, beans, peas, etc., become dry in cooking and get scorched, tar forms. Scorched toast has tar in it. In frying potatoes, eggs, meat and other foods tar is often formed unless great care is exercised not to overheat these foods. Meats roasted in an oven that is too hot get black on the outside. Tar is formed.

Tar is an irritant. It is one of the irritants that is known to result in the formation of tumors and cancers. It would be profitable to know what percentage of the tumors and cancers that exist today owe their origin to the tars taken into the bodies of almost everyone who eats cooked foods and drinks coffee or coffee substitutes. Living in smoky cities and inhaling the smoke takes tar into the lungs. This as much as tobacco smoke, may contribute to the production of cancer of the lungs.