The SMOG grade is a measure of readability that estimates the years of education needed to understand a piece of writing. SMOG is the acronym derived from Simple Measure of Gobbledygook. It is widely used, particularly for checking health messages. The SMOG grade yields a 0.985 correlation with a standard error of 1.5159 grades with the grades of readers who had 100 omprehension of test materials.

Smog is a type of air pollutant. The word "smog" was coined in the early 20th century as a portmanteau of the words smoke and fog to refer to smoky fog. The word was then intended to refer to what was sometimes known as pea soup fog, a familiar and serious problem in London from the 19th century to the mid 20th century. This kind of visible air pollution is composed of nitrogen oxides, sulfur oxides, ozone, smoke or particulates among others (less visible pollutants include carbon monoxide, CFCs and radioactive sources). Man-made smog is derived from coal emissions, vehicular emissions, industrial emissions, forest and agricultural fires and photochemical reactions of these emissions.

Bill Callahan (born June 3, 1966) is an American singer-songwriter and guitarist who has also recorded and performed under the band name Smog. Callahan began working in the lo-fi genre of underground rock, with home-made tape-albums recorded on four track tape recorders. Later he began releasing albums with the label Drag City, to which he remains signed today.