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1. INTRODUCTION AND OVERVIEW The hazards to humans and ecosystems from exposure to the high concentrations of atmospheric pollutants in urban areas are now well documented, having been the focus of much research. As a result, air quality considerations are becoming an integral part of urban and industrial planning. On the other hand, when some of the same pollutants are disseminated broadly beyond urban areas, their fates and effects are still little known. The analytical methods sufficiently sensitive to measure trace concentrations of many pollutants have been developed only recently. But even our present rudimentary understanding of regional and global distribution of atmospheric pollutants, now coupled with improvements in the scope and sensitivity of toxicity testing, has produced a number of indications in the scientific literature suggesting that some pollutants, even when diluted by air masses on a continental or global scale, may accumulate in the biosphere to concentrations that may be proved to be harmful. Organochlorine pesticides and radionuclides from nuclear testing are among those cited for widespread dissemination and accumulation. More recently, evidence of other kinds of atmospheric pollution has been found in rural and even wilderness areas remote from major sources of atmospheric pollution. Examples are acid precipitation, increased trace metal deposition, and reduced visibility. Many lines of evidence have shown that most kinds of atmospheric pollution have close associations with patterns of intensive human energy use. The consumption of fossil fuels is known to be the major source of anthropogenic pollution of the atmosphere, rivalled only by the high temperature smelting of metallic ores. It is predicted that energy demands will continue to increase exponentially (NRC 1979), and fossil fuels will play an important role in satisfying As a result, the Committee on the Atmosphere and , such demands. the Biosphere decided to conduct a general review of the pollutants discharged to the atmosphere from fossil fuel burning. Some of the effects of pollutants from fossil fuel usage have been relatively well studied--for example, the postulated linkage between increasing atmospheric CO2 and climatic warming (NRC 1977a, Kellogg 1
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2 and Schware 1981~; the damage to vegetation by photochemical oxidants (NRC 1977b); and the health-related effects of SO2, NOX, and lead (NRC 1978a,d; 1980a). Therefore, this Committee focused its efforts on the broad scale ecological effects of SOX and NOX, as well as on the less well-known trace metal and organic pollutants. Attention was concentrated on the general properties of pollutants that govern their emission, dissemination, deposition, and ecological effects in the hope that discernible patterns would emerge that could assist management agencies and legislators in foreseeing some of the environmental consequences of continued fossil fuel burning, and in devising research programs that will address the most critical of unknown factors as quickly as possible. THE FOS SI L FUEL SCENARIO: THE PROBABILITY OF A CRISIS IN THE BIOSPHERE Ecologists, geochemists, and climatologists are beginning to discover that in many respects man is now operating on nature's own scale, particularly through the heavy use of fossil fuels to supply the energy that runs our industrial civilization. Because the uncertainties associated with such large-scale operations are very great--for good or ill--it behooves us to exercise restraint in our present intensive use of energy, and to mitigate where possible the ill effects that air pollution imposes not only on us but also on the ecosystems that make up our life support system. In this connection numerous studies have reported on the substantial opportunities for energy conservation and shifts to alternative energy sources. The predicted effects of the continued and accelerated combustion of fossil fuels are many and complicated. Some climatologists hypothesize that discharge to the atmosphere of CO2 and other pollutants is likely to change the radiation balance of the earth sufficiently within the next century or so to cause major warming as well as changes in the patterns of climate. While there is considerable uncertainty in predictions, some of the hypothesized consequences could be severe. Droughts may be caused that are capable of reducing food production in many areas now providing surpluses for export. Other areas of the world may become able to produce more food than before, but many of these currently lack the technology and capital to do so. The postulated changes in climate would also cause major changes in many of the earth's natural ecosystems. Moreover, the hypothesized rise in sea level caused by the melting or breakup of the Greenland and west Antarctic ice sheets might necessitate the eventual relocation of major cities (NRC 1977a, Kellogg and Schware 1981), although the time scale is uncertain. Perhaps the first well-demonstrated widespead effect of burning fossi1 fuel is the destruction of soft-water ecosystems by "acid rain," which has been caused by anthropogenic emissions of sulfur and nitrogen oxides that are further oxidized in the atmosphere. Major effects include destruction of many species of fish and their prey and
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3 acidification of surface and ground waters to the point where toxic trace metals reach concentrations undesirable for human consumption and for aquatic animal habitats (see Chapter 8~. Severe degradation of many aquatic ecosystems has been recorded in Norway, Sweden, the United States, Scotland, and Canada (Drablos and Tollan 1980~. Surprisingly, significant effects have also been recorded for aquatic systems in countries once thought to be geologically resistant to acidification, including the Netherlands, Denmark, and Belgium (Vangenechten and Vanderborght 1980, Van Dam et al. 1980, Rebsdorf 1980). Although claims have been made that direct evidence linking power-plant emissions to the production of acid rain is inconclusive (Poundstone 1980, Curtis undated), we find the circumstantial evidence for their role overwhelming. Many thousands of lakes have already been affected, according to estimates by European and North American scientists (Drablos and Tollan 1980~. Acidified lakes have been found in areas where geological factors, such as volcanism and the weathering of pyrites, or biological factors, such as acid bog drainage, cannot be implicated. At current rates of emission of sulfur and nitrogen oxides, the number of affected lakes can be expected to more than double by 1990, and to include larger and deeper lakes (Henriksen 19801. There is little probability that some factor other than emissions of sulfur and nitrogen oxides is responsible for acid rain. Although the deposited nitrogen and sulfur may be slightly beneficial in terrestrial soils deficient in these elements, the stimulus is expected to be short-lived (Abrahamson 1980), and over the long term acid precipitation is likely to accelerate natural processes of soil leaching that lead to impoverishment in plant nutrients (Overrein et al. 1980~. When freshwater effects are considered, the positive effects are greatly outweighed by the negative. The same gaseous oxides are known to affect human health directly in urban areas (Lave and Seskin 1977, NRC 1977b, NRC 1977c, NRC 1978a, Mendelsohn and Orcutt 1979) and to cause decreases in crop yields in some areas. Acid deposition is also known to cause large economic losses by corroding metals and eroding buildings and statuary made of calcareous rock (Bolin 1971, Nriagu 19781. The Committee believes that continued emissions of sulfur and nitrogen oxides at current or accelerated rates, in the face of clear evidence of serious hazard to human health and to the biosphere, will be extremely risky from a long-term economic standpoint as well as from the standpoint of biosphere protection. Less well appreciated is the widespread dispersal of toxic metals by the burning of fossil fuel (Bertine and Goldberg 1971, NRC 1980a). Of most immediate concern are mercury, lead, zinc, and cadmium. Mercury metal occurs at high concentrations in many fishes under natural conditions. Its release to the atmosphere through the burning of coal and crude oil, as well as through smelting, cement manufacture, and municipal incineration, may already have been sufficient to elevate mercury concentrations enough to make fish from many areas unacceptable for human consumption. Lakes and rivers
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4 containing fish with elevated mercury concentrations have been reported from Sweden, Quebec, New Brunswick, Ontario, Minnesota, New York State, and Maine (Tomlinson et al. 1980). Precipitation in areas receiving acid deposition and high sulfate deposition also has elevated mercury concentrations (Tomlinson et al. 1980, Semb 1978, Dickson 1980), and mercury uptake by fish appears to be enhanced by low pH. At present, there is no satisfactory technology for controlling large-scale emissions of mercury to the atmosphere. Its continued or accelerated release, especially in view of its synergism with acid deposition, may cause chronic problems in many areas in years to come. Natural lead releases now have been exceeded by emissions from man's activities (Lantzy and Mackenzie 1979, NRC 1980a). While data are scarce, some have argued that the present body burden of lead in average Americans, and probably in other residents of industrial societies, is approaching chronically damaging levels (Patterson, see minority report in NRC 1980a; Settle and Patterson 1980~. Leaded gasolines are heavily implicated, though other industries are also important sources of lead (NRC 1980a). Models based on concentrations in sediment and water and on projected rates of increases in emissions suggest that in Lake Michigan both cadmium and zinc will reach concentrations toxic to zooplankton within the next 30 to 80 years depending on the rate of increase in emissions of the metals (Muhlbaier and Tisue 1981; Marshall and Mellinger 1980; G.T. Tisue and J. Marshall, Argonne National Laboratory, Argonne, IL, personal communication; Figure 1.1~. Many other waters may be similarly affected, although careful studies have not been done yet to document these changes. The chronicle of detrimental substances from the burning of fossil fuel could be continued for many pages, treating--among others --vanadium, arsenic, copper, and selenium. Also emitted are organic micropollutants of many types, some of which are known to be carcinogens, acute toxicants, teratogens, and mutagens. Hence, faced with the total array of atmospheric pollutants that could be reviewed--far beyond the scope of one committee's abilities--the Committee on the Atmosphere and the Biosphere decided to focus its attention on pollutants generated in energy production, most notably on sulfur and nitrogen compounds including acid rain, trace metals' and organic substances. Carbon dioxide, an important pollutant, is treated in some detail by NRC (1979b), and little space is devoted to it here. THIS REPORT Patterns of emission, transport, deposition, interaction, and biological effects of energy-related pollutants are known only incompletely, and we were forced to use a mosaic of examples to illustrate different concepts. We hope that this review will provide a preliminary guide to the sorts of integrated research needed to overcome weaknesses in our understanding of the consequences of
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5 1 ' 1 1 1 l ~ ~ l ~ 105 104 0 A 103 - UJ =5 10' Cal 10° 0% per annum 1% per annum 3% per annum ~—~ 5% per annum 7% per annum - 1 - 40 60 80 100 0 20 YEARS AFTE R P R ESENT FIGURE 1.1 Projected cadmium concentrations in Lake Michigan for various rates of increase in the annual input rate. The lower horizontal dashed line represents the con- centration at which toxic effects have been reported for aquatic organisms (Marshall and Mellinger 1980). The upper dashed line is the current U.S. EPA standard for waters of Lake Michigan's hardness. The present rate of increase of the input rate for Lake Michi- gan is 4.6 percent per annum, which would cause the lake to reach the toxicity threshold for aquatic organisms in about 40 years. The authors indicate that a high proportion of the input of cadmium is from the atmosphere. Cadmium in sediment at 10 6 gig is equal to 1.5 X 10 ~ g/1 in water. SOURCE: After Muhlbaier and Tisue (1981). Copyright (3 1981 by D. Reidel Publishing Co., Dordrecht, Holland.
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6 atmospheric pollutants. We hope, too, that the report will make apparent the probable consequences of unregulated reliance on fossil fuels to fulfill future energy needs. Chapter 2 reviews the scientific discoveries that led to the realization that the atmosphere is inseparably linked to the biosphere and that pollution of the atmosphere--even with trace amounts of toxicants--could have serious consequences for the latter. It is noteworthy that although atmospheric pollution has only recently become a widespread public concern, clearcut scientific evidence for the effects of atmospheric pollution from fossil fuel burning and smelting was generated during the second half of the 19th century. Confusion has recently developed over natural emissions of substances from the biosphere to the atmosphere. The mechanisms of exchange of sulfur, nitrogen, reactive trace metals, and organic substances between atmosphere and biosphere, insofar as they are known, are reviewed in Chapter 3. In Chapter 4, we quantify the emissions of these substances from fossil fuel burning and compare the magnitude and form of these emissions with those from other important anthropogenic activities as well as from natural sources. Chapter 5 is devoted to the transport, chemical transformation, and deposition of energy-related pollutants, with particular emphasis on physical and chemical properties of the emissions that affect their residence time in the atmosphere and thus the distance they are carried. Chapter 6 is devoted to processes affecting pollutants once they enter the biosphere, with particular attention to similarities in pathways, repositories, and effects of different pollutants. Examples of synergism, antagonism, and development of resistance to pollutants are given. Chapter 7 represents an attempt to generalize from what is known about important pollutants and sensitive parts of the biosphere to develop a blueprint for predicting the consequences of continued or accelerated pollution of the atmosphere. Again, because the information base is incomplete, only a rough, conceptual outline has resulted. Two of the major impediments to making more specific conclusions or predictions are the lack of a long-term data base sufficient to quantify small increases in toxicants and the inadequacy of methods for detecting and predicting low-level toxic effects, at the level of either organisms or ecosystems. In Chapter 8, we give an up-to-date case history of acid deposition, one example of the severe biospheric effects resulting from anthropogenic pollution of the atmosphere that appears already to have eliminated or substantially reduced the populations of some organisms, including fishes, in parts of their natural ranges. Owing to the concentrated efforts of scientists in the Northern Hemisphere, most notably in Scandinavia during the past decade, we have a much more complete knowledge of the causes and consequences of acid deposition than we have for other pollutants discussed here. Yet even for acid deposition, many mechanisms and effects are poorly known. Throughout the above-mentioned chapters we have attempted to indicate how widespread and complicated the atmospheric pollution problem is,
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7 and how intertwined the biogeochemical cycles of pollutants are with the cycles of naturally important elements. As a consequence, second- and third-order effects may be of great importance, but they are far more difficult to predict than the first-order effects upon which most attention is focused. Though necessarily incomplete in many respects, the information synthesized by the Committee renders a rather unfavorable picture of the consequences of current fossil fuel burning practices. Along with the probable large-scale effects described above, slow, nearly undetectable increases in a multitude of extremely toxic substances are taking place. It is the Committee's opinion, based on the evidence we have examined, that the picture is disturbing enough to merit prompt tightening of restrictions on atmospheric emissions from fossil fuels and other large sources such as metal smelters and cement manufacture. Strong measures are necessary if we are to prevent further degradation of natural ecosystems, which together support life on this planet. Some pollutants, such as sulfur and nitrogen oxides, particulate pollutants, and lead, are readily amenable to control by appropriate engineering technologies. Others, such as mercury and CO2, are more difficult and expensive to control by available technologies. In the long run, only decreased reliance on fossil fuel or improved control of a wide spectrum of pollutants can reduce the risk that our descendants will suffer food shortages, impaired health, and a damaged environment. CONC LUS I ONS AND RECOMMENDAT IONS Atmospheric pollution and its consequences deserve major consideration when the sources and sites of energy production are decided. However, much remains to be done if we are to assess adequately the ecological significance of atmospheric pollutants generated by different energy systems. To improve and refine our ability to detect what may be irreversible degradation in natural ecosystems, increased and improved scientific effort is needed in two critical areas: long-term monitoring and forecasting of future effects, and ecotoxicology. At present, the long-term data base on emission, deposition, and biological effects of all energy-related pollutants is insufficient. Such information is critical to forecasting ecological effects, both of fossil fuel combustion and of alternative energy production systems. Natural sources of the substances and linkages to the cycles of ecologically important chemicals must also be known, in order to discern how natural biogeochemical processes may be stressed or disrupted. Likewise, our knowledge of the toxicity of pollutants requires rapid development in four major areas: (1) identification of the phys~co-chemical and biological properties of natural ecosystems and organisms that are sensitive indicators of stress from pollutants; (2) development of statistical and mathematical methods for detecting and
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8 quantifying ecological deviations significantly outside the normal range in unstressed ecosystems, particularly in response to the synergistic and antagonistic effects of several pollutants acting in concert; (3) identification and protection of ecosystems, communities, and species that are especially sensitive to present or projected pollution burdens; and (4) an evaluation of how current toxicity tests, usually done with single species, relate to stresses at the ecosystem level. The personnel available to undertake such studies are not sufficient in number, nor are they trained adequately in the several disciplines necessary for the detection of subtle increases in pollutant stress on ecosystems over long periods. Protection of our threatened, sensitive ecosystems requires educational programs that are specifically designed to produce scientists with the necessary qualifications. While this need and some appropriate topics for study are identified and discussed in this report and elsewhere (NRC 1975, NRC 1981, Butler 1978), educational programs and research techniques need to be more clearly defined. In particular, current educational programs in toxicology must be upgraded to include rigorous statistical training and thorough grounding in ecological principles, with emphasis on detection of long-term, whole-ecosystem effects rather than on the current, short-term tests of individual species. The needed curriculum should utilize the combined strengths of programs in ecology and environmental engineering. University programs of biology and ecology usually lack strength in applied aspects of ecology, while programs in environmental engineering often pay insufficient attention to the foundations of their discipline in ecology. While combined programs do exist at some institutions, many lack the scientific rigor necessary for training experts to attack the complex problems that will be faced in the coming years. Current institutional arrangements are not designed to undertake effectively the complex, long-term studies envisaged. One possibility that deserves consideration is to set up a National Center for Ecology and Environmental Science, with functions similar in part to those of the National Center for Atmospheric Research and the U.S. Geological Survey. These organizations provide alternative models of governance--the first being supported by federal funds but governed by a consortium of universities, the second, a larger organization both funded and controlled federally. Such an institution would also require the cooperation and coordination of federal agencies, such as the U.S. Departments of Agriculture, Energy, the Interior, Health and Human Services, and the Environmental Protection Agency.
Representative terms from entire chapter: