Multimedia maneuvers; shifting tactics for controlling shifting pollutants.
But pollutants don't correspond as neatly. They waft from the air onto soils, wash into streams and seep from landfills into groundwater supplies. And in each different medium they can change chemical character, reacting with water in one phase to become acidic or turning toxic through microbial degradation in the soil. Often, one regulatory office's cleanup becomes another's undetected problem.
Acid rain is the most mentioned cross-media pollution. Standards set by EPA's air office to control sulfur dioxide have led some coal-burning plants to send emissions up and away from the locale through tall smokestacks. But once delivered to the upper atmosphere, the gas can disperse, combine with water vapor and rain down as weak acid onto distant forests and lakes.
Sulfur dioxide is among a spate of such pollutants. The large category of synthetic organic chemicals may be the most arresting cross-media problem, given their toxicity and wide use. These compounds--chemical arrangements of carbon, hydrogen and most often chlorine -- are manufactured in billions of pounds annually and constitute industrial solvents, pesticides, household cleaners and dry-cleaning fluids. The compounds themselves or caustic by-products of their manufacturer eventually become the stuff of hazardous waste. Because they can easily evaporte as well as dissolve in liquids, they have entry to air, soil, wate and organisms. In animals they affect heart, nerve, liver and kidney function; some cause cancer.
"These substances, including carbon tetrachloride, perchloroethylene, trichloroethylene, methylene chloride and methly chloroform [trichloroethane], are ubiquitous in society and in the environment," says Alvin L. Alm, who, as deputy administrator of EPA, spoke to a pollution control conference in Washington, D.C., last fall. "We find them in landfills, in urban ambient air, in discharges to surface waters and move readily from land to water or from water to air, and persist in the environments long after their release." Alm has since left EPA to join Clean Sites, Inc., an Alexandria, Va.-based organization working on hazardous waste cleanup.
The conference, sponsored by the Washington, D.C.-based Conservation Foundation, was the first national meeting to focus on cross-media pollutations. One hundred environmentalists, industrialists, academics and splintered enironmental laws and whole-environment pollutants. An integrated approach should be the rule of pollution control, they agreed, but shortcomings in existing laws and in scientific understanding of how pollutants circulate suggest that a truly integrated environmental policy is not likely to be realized anytime soon. Still, uncontainable hazardous wastes are drawing more attention to cross-media problems and may prompt a change from the prevailing view of pollution as a single-medium, neatly boxed affair.
A first step in controlling pollutants on a cross-media basis is knowing where a volume of chemical goes after it's created. Mass balance studies chart a pollutant's path by comparing the amount of the chemical in the air, water and soil with how much has been released.
New Jersey has one of the few organized programs compiling information on production and emissions to track specific chemicals. State regulators survey some 45,000 industrial sites, quantifying the chemicals that go into a product and amounts that are discharged into air or water, or trundled off as solid waste. The valuable chemical bookkeeping has pinpointed, for example, which generators are responsible for making toluene the most prevalent toxic substance in the New Jersey air -- the kind of information policymakers need but rarely get.
Mass balance studies can be done on any environmental scale, and EPA is tracking the paths of chlorinated organic solvents nationwide as a model for cross-media control. According to Alm, "The work [EPA is] doing on chlorinated solvents grapples with the issue that lies at the heart of the cross-media problem: Where od we really want the stuff to end up?"
The air may be the sink for many toxic compounds. Most air today holds a mix of about 100 organics and other toxic chemicals that may or may not be harmful at their parts-per-billion and parts-pertrillion levels. The spotty data on their health effects, as opposed to the better-known hazards of conventional air pollutants such as lead, leave them in regulatory limbo.
The first EPA study on the extent of air-borne toxic chemicals may prod some action when official review of the report is completed. Currently only two toxic organic compounds -- vinyl chloride and benzene -- fall under enforceable EPA standards, along with six other toxic air pollutants. An additional 25 hazardous compounds, including some organics, are under study for possible regulation.
Direct release from stacks and tailpipes is not the only way toxic pollutants from other media get shunted to the air. Contaminated groundwater is commonly cleanup up by pumping the water to the surface and allowing the undestroyed organics to volatilize into the air. In other cases, the pumped water is run through charcoal granules that sponge out the chemicals. Though spent carbon can be recycled--an extra cost-incurring step--it can also be dumped into landfills from which the volatile compounds can enter the air.
Hazardous pollutatns can sidle into the air from other unsuspected places. An EPA study in Philadelphia found that sewage plants, in treating municipal waste and an increasing amount of commercial waste, are releasing as much of that city's toxic air pollutants as the more obvious chemical factories.
If the air is becoming the sink for volatile and toxic pollutants, they can still drain out. A report to be published in ENVIRONMENTAL SCIENCE & TECHNOLOGY describes a model for one known carcinogenic organic, trichloroethylene (TCE), that shows how TCE in the air -- where about 60 percent of all manufactured TCE is lost -- disperses to soil and water over time.
Coauthors Yoram Cohen and Patrick A. Ryan of the University of California at Los Angeles (UCLA) constructed a mathematical model to represent air, soil, water, sediment and fish, then looked at how TCE distributes itself into each of these. If TCE stayed in the air, it would degrade in sunlight as all chlorinated organic compounds do (though some take longer than others). But the UCLA model shows that before all the TCE can be broken down, it settles into soils and sediments, where it is more stable.
The final TCE concentrations predicted by the model reasonably correspond, say the authors, to actual levels found in the environment. And because the model considers shifting pollutants over time, it can siders shifting pollutants over time, it can be used to point out to policymakers which chemicals pose the most threat and where.
"This is a tool for determining pollutant pathways and where the environmental hot spots are," says Cohen. A toxic chemical may not be an air problem if it breaks down quickly, but it can become a serious land problem if it accumulates in the agricultural topsoil. Cohen expects multimedia modeling to be useful in screening new chemicals as well as existing ones. Manufacturers develop more than 1,000 new chemicals each year.
Cohen conducts his research at the National Center for Intermedia Transport Research, an EPA-funded center at UCLA. In the young field of cross-media research, it is the only organized academic research group that studies the mechanisms of pollutant transport through the whole environment. The group of eight scientists and engineers is concentrating on organic pollutants and their behavior at media boundaries, as well as their flow and accumulation in the environment.
Tracking and transport studies look at pollutants once they are released inot the environment. But the ultimate cross-media control, according to many speakers at the Washington conference, is to catch pollutants at their sources. Source reduction is going on, says Richard E. Heckert of E.I. du Pont de Nemours & Co. in Wilmington, Del. Industries are practicing "preventive environmental medicine," he says, by designing manufacturing processes to avoid or reduce waste, by recycling some wastes as fuel and by considering potential environmental impacts before buidling new plants.
Still, four-fifths of the 118 million metric tons (dry weight) of sludge generated annually in the United States comes from industries. Their wastes, along with the remains of sewage and water treatments, make up a morass of organic and inorganic chemicals, heavy metals, viruses and bacteria. Land receives the bulk of this waste, which is intended to be securely contained. But its more toxic and persistent ingredients often make their way into soils and groundwater as well as into the air.
Conference speakers pointed out the need for an umbrella policy to deal with the seemingly disparate problems of hazardous sludge, contaminated groundwater and acid rain, all of which affect mixed media. The basic ideas of integrated enivronmental control are not new--the EPA itself was formed in the ecology-minded mood of the late 1960s. But mdeium-specific laws, bureaucratic divisions, strict scientific specialties and even environmental groups that lobby separately for clean air, clean water and clean land have hampered the development of an integrated policy. "The lack of data hamstrings us all," says Glenn Paulson of the National Audubon Society in New York, but "we lack conceptual, intellectual tools, too" for an integrated control.
Resurgent interest in the cross-media problem may provide a few more tools that work within the existing framework. There is enough "wiggle room" in current laws to allow cross-media considerations at least at the state or local level, according to Ernest Abbott of EPA's policy office. But in the long run, says J. Clarence Davies of the Conservation Foundation, the media-oriented laws will at least have to be modified for an integrated approach.
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|Title Annotation:||cross-media pollution by air, water and solid waste|
|Date:||Feb 23, 1985|
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