The movement of toxics underground and the health effects of certain

organic toxics are not well understood

The dominant impression conveyed by a water conference held in late January in Philadelphia is that scien­tists understand very little about cer­tain aspects of water quality, particu-lar ly g r o u n d w a t e r q u a l i t y . T h e amount of groundwater that is con­taminated is not known; in many cases the movement of toxics through the ground and in the aquifers is ex­tremely difficult—if not impossible— to predict; and the human health ef­fects, if any, caused by many organic c o n t a m i n a n t s a r e known e i t h e r vaguely or not at all.

The conference, entitled "The Fate of Toxics in Surface and Ground Wa­ters," was the Second National Water conference. It was sponsored by the Academy of Natural Sciences, the American Water Works Association, and the Water Pollution Control Fed­eration.

The speakers held diverse views abou t the seriousness of cur ren t groundwater contamination. Former EPA Deputy Adminis t ra tor John Quarles of the Washington law firm of Morgan Lewis & Bockius seemed to have a very optimistic attitude to­ward the subject. He said that "most of the contamination that does exist is highly localized," and the majority of the aquifers that have been contami­nated can't be cleaned up. "In most respects, that won't make any differ­ence," he noted, because the "ground­water that is contaminated won't be needed." But contaminated isolated residential wells are a problem, he ad­mitted.

Glenn Paulson of the National Au­dubon Society holds a rather different view of groundwater. He mentioned an unreleased EPA survey of ground­water in 954 cities g rea te r than 10 000 people which found contami­nation in 29% of the underground wa­

ter supplies and said that there are large numbers of industrial impound­ments and hazardous waste sites which could cause contaminat ion over time.

Many of the speakers mentioned that, according to current estimates, 1 - 2 % of the groundwater in the U.S. is contaminated. This figure is not based on a comprehensive survey of groundwater quality because none has been done. Marian Mlay, acting director of EPA's groundwater office,

said that it would cost half a billion dollars to do an accurate survey.

Some observers consider the 1-2% figure low or uncertain when viewed in light of the number of hazardous waste sites, surface impoundments, underground injection wells, and gas­oline storage tanks—many of them leaking—in the U.S. Ruth Patrick, senior curator at the Patrick Center for Environmental Research, Acade­my of Natural Sciences, mentioned that tens of thousands of sites have

124A Environ. Sci. Technol., Vol. 18. No. 4, 1984 0013-936X/84/0916-0124A$01.50/0 © 1984 American Chemical Society

ES&T OUTLOOK

Water quality uncertainties

received hazardous wastes and hun­dreds of sites are continuing to receive them. In addition, surface impound­ments containing toxic liquids num­ber approximately 59 000, according to an EPA review in the late 1970s cited by Paulson.

Many of these surface impound­ments and hazardous waste sites, even those that contain a small amount of toxic material, could become sources of groundwater contamination if the sites described by John Cherry of the University of Waterloo are represen­tative. He told about experiments in which an aquifer was contaminated by just a few milliliters of a halogenat-ed hydrocarbon so that it exceeded drinking water standards. "I t only takes a drum or two, given time, given dispersion, given dissolution, to pro­duce large domains of contaminated groundwater when we are looking at halogenated hydrocarbons that are of concern at ppb levels," he said.

A number of the speakers men­tioned sources of surface and ground­water contamination that up to the present have not been highly visible concerns of the general public. Pat­rick said that spraying or spreading sludges on land may cause contami­nation from the water that passes through the sludge and enters the ground and hence the ground or sur­face water. She also noted that im­properly designed or maintained sep­tic tanks often pollute water not only with human waste, but with metals and complex organic compounds that are used in the home, She especially emphasized nonpoint sources. "Feed-lots where a thousand or more head of cattle are fattened" were mentioned in particular as important nonpoint sources of nitrates that often seep di­rectly into groundwater. Nitrate con­centrations as low as 50 m g / L can cause intestinal upsets in children or the birth of blue babies if the expec­tant mother drinks the water.

Unpredictable movement Cleanup activities to prevent the

contamination of aquifers are often predicated on the assumption that sci­entists have some ability to predict what happens to contaminants once they enter the ground. Cherry de­scribed a number of situations in which such predictions are impossible or nearly so. Sand and gravel are often considered the most predictable me­dia for contaminant movement. How­ever, in these media, " 'blobs' of con­taminants split off into separate blobs in unpredictable ways, but the move­ment of each individual blob can be predicted more accurately," Cherry

said. Those contaminants that he calls sinkers or floaters—those heavier or lighter than water—are a special problem. They seem to be almost en­tirely unpredictable, even in sand and gravel.

The movement of contaminants in clay is sometimes even more difficult to predict. It is generally believed that clay is a good place to put toxics be­cause in the laboratory they move so slowly through clay that their move­ment is virtually zero. In the field, however, the situation is often quite different. Here, the clay is usually cracked, at least down to a consider­able depth, so the pollutants may move just as fast through clay as they do through sand and gravel. Cherry showed many sites where clay was deeply fractured from weather or from tunnels created by decayed tree roots. He described a site in Oregon where drums containing liquids were bulldozed into trenches in clay soil. From these, a plume of 2,4-dichloro-phenol was moving 100 ft/y at a con­centration of m g / L — a high level.

Fractured rock is an equally serious problem, he noted. It is a medium where it is almost impossible to pre­dict the movement of plumes. Cherry also said that knowing where the inor­ganic contaminants go tells you very little about the movement of organic contaminants and therefore these need to be monitored. As a result of these observations, Cherry said, "I think there are going to be a lot of cleanup activities that are going to be done in the absence of very good sci­entific information." This will lead to "many, many more wells and water supply systems going bad" because of groundwater contamination that is unpredictable and unexpected.

Wayne Pettyjohn of Oklahoma State University spoke in a similar vein. He noted that it has become "common practice within the past few years to develop manuals and tech­niques for regulatory pe rsonne l . . . to predict concentration distributions in the subsurface" and that many of these techniques involve the use of computer programs. When computer programs are used to predict the movements of contaminants under­ground, he said, the results are often extremely uncertain or limited be­cause the inputs to the program are often very uncertain, limited, or sim­ply unavailable. He advised that it is far more realistic to enter data into computer programs that have lower and upper bounds of uncertainty so that the results are expressed in a kind of risk probability curve rather than as definite numbers.

Liai Tischler, vice president and manager, Southwest Operations, En­gineering-Science, Inc., noted re­search needs in the area of waste treatment. He said that "the proper conditions of biodégradation, or pos­sibly adsorption, of many complex or­ganic compounds are still not well un­derstood." On the other hand, he concluded from a review of the litera­ture that the number of organic com­pounds that are resistant to biodégra­dation is much smaller than was believed a few years ago.

Unknown health effects Many of the speakers emphasized

how little is known about the effects of organic water contaminants on hu­man heal th . Gordon Wolman of Johns Hopkins University said, " I think it is safe to say that the data on the hea l th effects of h a z a r d o u s wastes, particularly the chronic ef­fects, are exceedingly limited." Wil­liam Lynch, president of the Ameri­can W a t e r W o r k s A s s o c i a t i o n , echoed the same idea. "We can identi­fy substances in water with incredible accuracy, but as to their significance as potential threats to human health, we have only some very shaky ex­trapolations from some very vague ideas."

Abel Wolman, professor emeritus at Johns Hopkins University, men­tioned that many of the diseases that could be caused by organic chemicals in water are in the carcinogenic group and that if we wait for epidemiolog­ical evidence, we might have to wait 60 years. "Sufficient data are turning up to indicate that toxics in water ex­ist and that their presence is certainly not salutary," he said. He expressed particular concern about the genetic damage that chemicals in the water might cause to future generations. "The genetic risk causes special con­cern," he said, "because . . . the bulk of the risk is not to our immediate children but to our remote grandchil­dren."

Dr. Norton Nelson of New York University Medical Center noted that sometimes the attention given to toxic chemicals has been inflated, but that "there is enough actuality for these to be of concern." He said that the medi­cal center is especially concerned about chronic exposures to various chemicals and mentioned in particu­lar t r i h a l o m e t h a n e s ( T H M s ) in drinking water. He observed that in epidemiological studies of T H M s , positive results abound and that none of the results are negative, although none of the studies are as definitive as epidemiologists would like to see. He

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mentioned Kenny Crump's (Science Research Systems) idea that rather than THMs, the cause of the cancers may be the nonvolatile organic com­pounds and other volatile organic compounds not yet tested that often coexist in water with THMs.

To test the effects of contaminants on aquatic organisms, John Cairns, Jr., of Virginia Polytechnic Institute recommended that scientists begin multispecies testing followed by vali­dation in the field. Single-species tests in the laboratory have been relied on almost exclusively in the past. In the natural environment, we sometimes see fish swimming around in 10 times the "lethal doses" that were calculat­ed using single-species tests in the lab­oratory, Cairns observed. Therefore, he believes that the single-species test may be vastly overprotective. He said the first suitable multispecies toxicity tests are now available for both aquat­ic and terrestrial systems.

Society's response Scientists and other experts in the

water field seem to agree that little is known about the human health ef­fects of many organic contaminants found in water, but they disagree greatly about how much society should be willing to pay to clean up the water supplies or how urgent a priority it should be.

Earnest Gloyna, president of the Water Pollution Control Federation, defines acceptable pollution control as controlling those pollutants that cause demonstrable harm. But some scientists point out that, if it takes several decades to demonstrate an ac­tual cause and effect relationship be­tween certain organic chemicals and cancer, many cancers will have to oc­cur before these pollutants are con­trolled.

Abel Wolman's approach to the question is entirely different from Gloyna's. His philosophy can be summed up in a few words: "Take it out." He said that as a result of a National Science Foundation inquiry, he was drawn to an old maxim "that the consumer should be given the benefit of the doubt when contami­nants are being assessed." He also be­lieves that keeping contaminants out of drinking water is not nearly as ex­pensive as some suggest, especially when you consider that drinking water is a cheap commodity, now costing an average of 25 cents a ton.

The proceedings of the conference will be available this month from the Academy of Natural Sciences, Phila­delphia, Pa. 19103.

—Bette Hileman

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