The article, “EPA’s air-quality guidelines called ‘a joke'” (BDN, April 24-25), on Environmental Protection Agency air quality guidelines, referred to ozone and said it was “also known as smog.” If the author had bothered to consult a knowledgeable scientist, she would have found that ozone is not “also known as smog,” but is a discrete chemical compound (a molecule) consisting of three oxygen atoms, and that it is a very strong oxidizing agent.

Ozone is not smog. It is what causes what we have come to call smog when it reacts with many hydrocarbons, such as those in automobile exhaust.

Interestingly enough, ozone was causing “smog” long before automobiles were invented. A source of smog hardly ever mentioned in articles condemning the lack of government interest in the atmosphere is the hydrocarbon compounds that are emitted by the conifers that inhabit Maine’s forestland and in fact all of the forested areas in our country. It is this natural “smog” that earned the Great Smoky Mountains their name, and that happened before we settled this nation.

Exposed to ultraviolet light (sunlight), the hydrocarbons emitted by trees react with the ozone present in the environment to form smog. The EPA found out many years ago that ozone levels in some forested areas were higher than those in urban areas. This is not to say that we do not need to control emissions from power plants and other such sources of pollution. However, those are not, by any means, the only source of what we call “pollution” in our air.

James Williamson

Senior research chemist (retired)

Lincolnville