Water has become the most precious natural resource in this modern age, but humanity is indifferent to and unaware of the dangers facing this environmental system. There are many kinds of pollutants affecting the water supply, but it is the mixture of these chemicals that is particularly threatening, since the interactions between these chemicals are poorly understood. Rolf Eliassen, a professor at M.I.T. testified to this effect at a congressional hearing on water purity, warning those assembled that we do not know what is in our water.
This is the first of the chapters in which Carson tackles individual parts of the environment to show their vulnerability to pesticides. A main theme, again, is just how little is known about the potentially dangerous effects of these chemicals on the precious water system. Since water is a fundamental part of human life, as well, the focus here is on the unknown substances in drinking water that humans consume.
Insecticides are being applied directly to water systems, or indirectly via aerial spraying that then becomes mixed in with agricultural runoff water, making these systems toxic to fish. Further, discoveries of DDT traces in fish upstream of contamination or spraying sites suggest that once these chemicals get into the groundwater that the groundwater transfers the chemicals all throughout the system. This means that all water is threatened by contamination anywhere.
The water system is a particularly good example of the ways in which nature is an interconnected system; it is impossible to treat water ‘selectively,’ since any contamination spreads throughout the environment. Most often, water is not sprayed purposefully – but chemicals find a way to contaminate it nonetheless, beyond the control of humans.
Chemicals from agricultural runoff have been found to contaminate drinking water even after the runoff has passed through water purification plants. Chemists have little understanding of what chemical combinations might be reaching the public, how to test for them, or what their effects might be.
This situation, in which dangers are unknown, massive, and insufficiently researched, requires that the public exercise caution and slow down the rapid spread of chemicals according to the precautionary principle.
Carson recounts the story of a farming district in Colorado contaminated by chemicals that had leached into the water table from the Rocky Mountain Arsenal—a factory that produces pesticides—located several miles away. Over seven or eight years, these chemicals had traveled through the groundwater to pollute local wells. Most alarmingly, wells tested positive for a synthetic chemical called 2,4-D, a weed killer that had apparently formed spontaneously in when certain chemicals combined, independent of human oversight.
Here is a concrete example of the sort of environmental changes undergone by chemicals that Carson has been hinting at – the unaided formation of 2,4-D is a sign that poisonous substances can result from these interactions. The time since contamination – eight years – demonstrates that the effects of spillage or leaching can be long term, making them very difficult to detect.
In another example, at key wildlife refuges in Oregon and Northern California, agricultural runoff of DDD and DDE caused mass poisonings of migratory birds within ‘protected’ zones. The poisons were passed up the food chain from plankton to waterfowl, as fish that ate infected plankton accumulated a larger dose, and waterfowl that ate infected fish concentrated the poison within their own bodies further still. This process in which poisonous chemicals become more focused as they move up the food chain, is known as bioaccumulation or biomagnification, and is particularly dangerous because of its impact on humans, who are often at the top of the food chain.
This example illustrates the ways that nature’s interconnected systems can spread the effects of a poison that is meant to target only a single species of pest to other parts of the natural community – including those parts that humans have designated as worth protecting. Bioaccumulation, explained here, is a key part of this ripple effect, transferring poisons from insects to birds, larger mammals, and humans themselves.
In Clear Lake, California, fishermen chose to dose ‘gnat-infested’ waters with DDD, even though the gnats were not especially harmful. Despite ‘careful planning’, the operation had to be repeated, and the following winter revealed that other species had been affected. The western grebe, a bird of “spectacular appearance,” died out completely in the area, having eaten fish that had in turn eaten infected gnats and plankton, again accumulating increasingly concentrated doses of the chemical. Because the chemicals had passed from the lake into the tissues of its inhabitants, initial tests of the water had suggested that it was safe.
Carson emphasizes that the gnat was not a dangerous pest – merely an annoyance. When the fishermen decided (recklessly, or arrogantly, as Carson would see it), to exert their control over the natural world, their efforts backfired, as bioaccumulation led to the poisoning of the western grebe. The fact that this contamination was initially undetectable should inspire caution in a reader, who may have been assured of the harmlessness of pesticides in the past.
Carson questions the wisdom of using substances with such strong biological effects that can impact the drinking supply. Dr. Hueper has warned that cancer hazards in public drinking water are increasing, and there is evidence to support his claim. The complex, interconnected nature of the water system, especially, supports Carson’s claim that “in nature nothing exists alone.”
Carson concludes the chapter by returning to the dangers posed to humans by contaminated drinking water, with the new awareness of the interconnected nature of the water system and its inhabitants to support her suggestion that current practices are foolish.