Molecule of the Week: Polychlorinated biphenyls (PCBs)

structure of PCBs via Wikimedia Commons, GNU Free Documentation license

The molecule of the week is actually a collection of 209 different possible versions of this molecule that have multiple chlorine atoms connected in different combinations along the hexagonal segments of the structure– like charms on a bracelet.

Though these chemicals are highly heat resistant (used as flame retardants in electronics manufacturing until the late 1970s, more info at the EPA website), they are now considered possible cancer causing agents, may cause developmental problems, and persist in the environment for years. They also bioaccumulate, increasing in concentration in larger animals as they eat smaller ones.

PCBs are particularly problematic in the Hudson River, where more than 1 million pounds of the chemicals were dumped in the upper part of the river from 2 General Electric factories for 30 years before the chemicals were banned. For the last 25 years, 197 miles of the river– reaching all the way to New York Harbor have been considered an EPA Superfund site. On, May 15, the dredging clean-up began— in an area upstream of Albany, New York, near where the chemicals were originally dumped.