Out of sight, out of mind: the trouble with runoff

Every high-school science student knows that water is the great solvent. Perhaps that’s why societies around the world tend to use streams, rivers, oceans, and bays as dumping grounds. Out of sight, out of mind. We assume that the world’s water bodies are big enough to dilute sewage, industrial waste, farm runoff, and any other pollution we send their way.

But two recent studies show that, as you might suspect, the pollutants running into our water aren’t helping our already beleaguered fish populations.

For instance, scientists have long known that pesticides and fertilizers running off of farm fields could disrupt the food chain in nearby streams. But now an Indiana University study suggests that the crops themselves might be contaminating nearby water bodies. When the leaves, cob, and pollen from Bt corn—a variety of corn genetically engineered to produce the Bt insecticide—are washed into streams near cornfields, aquatic insects are exposed to the toxin. (Bt corn now covers roughly 35 percent of the U.S. Corn Belt and Bt cotton grows on an increasing share of the nation’s cotton land.) The insecticide is aimed at the corn borer, but it also has toxic effects on many non-target insects, including caddisflies, aquatic insects that are a major food source for fish and frogs. In laboratory trials, caddisflies that were fed leaves from Bt corn had growth rates that were less than half those of flies fed non-Bt corn litter.

A separate study of the lower Columbia and Willamette rivers found that other, inadvertent, pollutants could be hurting salmon populations in the Northwest. Shampoos, coffee grounds, flame retardants, medicines, beauty care products, pesticides, cleaners, and household chemicals that end up down our drains show up in these rivers in amounts large enough to disrupt the fish’s reproductive systems, growth rates, and ability to deal with predators. The study examined salmon flesh and stomachs and found traces of a long list of chemicals, indicating that even substances we wash away can come back to haunt us in the food we eat.

To help address this problem, the Lower Columbia River Estuary Partnership plans to encourage consumers to purchase eco-friendly household and body care products, organize proper disposal programs for unwanted prescription medications and toxic chemicals, and promote composting as a way to keep certain foods out of the sewage stream. Encouraging organic farming and lawn care, which would eliminate the use of genetically modified crops like Bt-corn, could also help.