The PCB Problem

When petroleum-based solvents like paint thinner and jet fuel are combined with chlorine a number or useful products result: dry cleaning fluid, pesticides, and electrical transformer oil, to name a few. Pure petroleum distillates flushed into our oceans are digested by bacteria as are all naturally occurring products of photosynthesis. But chlorination prevents digestion because the unusual compounds formed resist enzymatic attack. So compounds such as polychlorinated biphenyls (PCB'S) eventually find their way into the ocean where they accumulate.

PCB's are easy to find in water because they prefer not to get wet. They will penetrate plastics just to dry off. Scientists can easily obtain PCB samples from the ocean by letting pieces of styrofoam cup soak them up. The problem with PCB's is that they are collected in the fatty parts of microorganisms. This concentration factor between the organism and the water can be as much as a million. Concentrations may be further amplified as the microorganisms become food for animals farther up the food chain.

Although detoxification mechanisms are common in higher organisms, some mammals and fish wind up with a large dose of PCB's and other recalcitrant (metabolism resistant) man-made molecules anyway. While an understanding of PCB toxicology mechanisms is just emerging, it is known that these substances do make animals sick. There are localized examples of other effects such as thinning egg shells, that has led to declining populations of falcons and other birds at the top of the food chain.

Because of these problems industry is using biodegradable substitutes for PCB's. Researchers here in Alaska are seeking to find which PCBs can safely be used and the distribution of organisms that can manage to eat them.