Scientists have been puzzled by the fact that the San Joaquin Valley often suffers high ozone levels even though the mostly rural, agricultural domain has fewer cars and trucks than big cities. Research by UC Davis scientists is now showing that some of the ozone in the valley is being generated by fermented animal feed, according to a story posted yesterday on the website Science News.

While ozone provides a protective barrier for the earth in the stratosphere, it is an unwelcome molecule to have around where people are breathing. Ozone (O₃) is a powerful oxidizing agent, far stronger than...