Polycyclic aromatic hydrocarbons (PAHs) are thought to account for about 20% of the carbon in the universe (see here, here, and here) and are considered building blocks of life. On Earth, PAHs occur in organic matter, including fossil organic matter (oil, coal), and are constantly being made when organic matter is heated or decays. They are also constantly being destroyed – eaten by microorganisms, degraded by the sun, other natural processes.

PAHs cause headaches for both regulators and the regulated. The headaches are rooted, in part, in history, so this post is a brief introduction to the history of PAHs in the environment, with an example of a regulatory headache exacerbated by government scientists who misrepresented historical data.

Generally speaking, no one makes PAHs on purpose – they are just part of the raw materials and byproducts of modern life. In addition to being present in oil and coal, PAHs are made in wood-burning fireplaces and stoves, in engine lubricants, in compost heaps, in decaying plants in a swamp… wherever organic matter is heated. Thus, humans are now and have, since fire was tamed, been exposed to PAHs. As one researcher put it: Continue reading →