Toxic Chemicals and Drinking Water

Without toxic chemicals in our drinking water supplies, life itself might continue to be possible.


| March/April 1983



toxic chemicals drinking water - accumulated sludge near river bank

Contamination like this is easy to see, but drinking water is often laced with toxic chemicals that are colorless and odorless.


Photo by Lester V. Bergman & Advocates

As William Ashworth so aptly put it in his book Nor Any Drop to Drink (see Paupers in the Midst of Plenty: Water Pollution and Water Shortages), "We are not destroying our water; but we are rendering it unusable, which amounts to the same thing." And clearly, one of the greatest threats to our ability to assure ongoing and adequate supplies of clean drinking water is the increasing presence of toxic chemicals in those precious resources.

In order to understand the scope of the problem, it's necessary to realize that the General Accounting Office (GAO) has stated that 43% of community water systems in the U.S. violated safe drinking standards in 1981. Now many of those problems no doubt were biological in nature, but at least as many likely involved a toxic metal or compound. Worse yet, of the 146,000 recorded violations, only 16,000 were properly reported to the public (as is required by law). And lest country folk feel too secure with their private wells, Cornell University reported last year that approximately 39,000,000 rural citizens are drinking unsafe water. And, of that sample, 17% reportedly were exposed to dangerous concentrations of the extremely toxic heavy metals lead and cadmium.

Of course, many people are aware of the well-publicized water quality problems that have cropped up in some parts of New Jersey and were created by leaks from hazardous waste dumps. But the lack of publicity given to other contaminated wells hides the fact that water pollution is playing no regional favorites. From the 39 wells closed in the San Gabriel Valley in California because levels of trichloroethylene (TCE, a carcinogen and toxicant) reached 600 parts per billion (PPB), to nitrate contamination from fertilizer runoff and feedlot leaks in Nebraska, to a well in Pennsylvania that was actually measured at 27,300 PPB of trichloroethylene, water pollution is a national (indeed, a worldwide) problem.

Where Does Your Water Come From?

In general, potable water is extracted either from surface supplies (lakes and rivers) or from ground water (which lies below the earth's surface and either rises by hydrostatic pressure as in artesian wells or must be pumped out). These two sources interact in sometimes complicated ways: Ground water, for instance, may help to fill lakes and rivers, or the lakes and rivers may slowly recharge ground-water supplies. The mapping of such exchanges is probably best left to trained hydrologists, but there are a few important basic differences that you should understand.

Water in streams takes about two weeks (on the average) to make its journey from the headwaters to the ocean, while lakes hold a portion of their rainfall somewhat longer, but ground water may be in place for thousands of years, and generally moves at an annual pace of less than ten feet. For that reason, contaminants can remain present at high concentrations long after entering ground water.

Yet another important characteristic of ground water is that this liquid is actually contained within rock and/or sediments, and therefore receives considerable filtration. (The image of underground rivers is accurate only in the loosest sense; cavities filled with water actually are quite rare.) This filtration effectively eliminates biological hazards, but it's far less successful at stopping toxic chemicals. In fact, some particularly volatile synthetic organic substances (trichloroethylene is one of these) may move even more rapidly through ground water than does the H20 itself. There is also some concern that layers of subterranean sediment which are, for all practical purposes, impermeable to such substances as oil and salt may be far more permeable to this new breed of pollutant. Thus clay layers that had previously been considered adequate for "insulating" drinking-water aquifers from those used to house disposed-of waste (yes, toxic substances of all sorts are actually pumped underground in efforts to "get rid" of them) may already be proving inadequate to confine the volatile organic chemicals.

brianna
4/24/2007 4:56:05 PM

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