Great Lakes Here is an overview of the origin, distribution, and fate of some heavy metals and organics, and some suggestions as to what may be done about them
Joseph J. Delfino Laboratory of Hygiene Uniuersity of Wisconsin-Madison Madison, Wisconsin 53706 Concern over the presence of chemicals in the Great Lakes has increased in recent years. Alfred Beeton reviewed historical trends of many common anions and cations, and found lhat their concentrations increased slowly but continuously in the past half century (Eutrophication, National Academy of Sciences, 1969). These changes were accompanied by changes in the biota, particularly the algae, as populations evolved from so-called clean-water species to those indicating eutrophic symptoms. Beeton hypothesized that man’s activities were influencing the limnology of the Great Lakes, resulting in decreased water quality. These conditions were noted particularly in Lakes Erie and Ontario Feature articles in ES&T hace by-lines, represent the ciews o f t h e authors. and are edited by the Washington staff. I f y o u are interested in contributing an article, contact the managing editor. 1462
Environmental Science & Technology
and in the southern basin and Green Bay in Lake Michigan. An international conference, held in Madison, Wis., in 1967, focused on eutrophication and spurred greater research interest. Numerous additional conferences have been held on this topic in the past 12 years. However, environmental issues rarely remain simple, and in the early 1970’s the eutrophication problem was confounded by concern over the potential effects of thermal pollution in the Great Lakes, a topic reviewed some years ago by Arthur Levin and others ( E S & T , March 1972, p 224). For instance, as demands for electric power increased, especially in the Midwest, many power plants were constructed on Great Lakes shorelines. Citizens and regulatory agencies, already alarmed by the specter of eutrophication-influenced water quality changes, attempted to restrict the discharge of power-plant cooling water into the lakes. By 1972, these two issues had created sufficient attention that an interstate enforcement conference on Lake Michigan pollution was convened. Also in 1972, the Great
Lakes Water Quality Agreement between the United States and Canada was first signed. It established waterquality objectives and timetables, and espoused a nondegradation philosophy. While these environmental issues in the early 1970’s originally emphasized phosphorus loading and thermal pollution in the Great Lakes, the toxicchemical problem was also developing. Although the first serious alert concerning toxic chemicals, particularly pesticides, had been sounded by Rachel Carson in The Silent Spring in 1962, it was not until the late 1960’s and early 1970’s that the combination of increased environmental awareness and laboratory analytical capability led to the discovery of pesticides throughout the Great Lakes Basin. The chemical stability of many pesticides, coupled with their capacity to bioaccumulate, resulted in high concentrations of compounds such as DDT and dieldrin in fish. Fish that exceeded U S . Food and Drug Administration (FDA) tolerance levels for pesticides could not be sold commercially.
0013-936X/79/0913-1462$01.00/0 @ 1979 American Chemical Society
FIGURE 1
Mercury concentrations in surface sediments of the Great Lakes
Mercury, ppba
-/
02000
During the time that extensive effort was mounted to document DDT levels in Great Lakes fish, chemists notqd that additional compounds were also present. In fact, some of these other substances created significant problems in the analysis of DDT. It was soon recognized that these troublesome compounds were polychlorinated biphenyls (PCB’s), and that they were also present at levels as high as 25 pg/g. These historical levels have been documented by scientists from the U S . Fish and Wildlife Service (FWS), the U S . Environmental Protection Agency (EPA), and particularly by Gilman Veith at EPA’s Duluth, Minn., laboratory. Thus, what was first a problem involving nondegradable pesticides, such as DDT, soon blossomed into a major issue of contamination by all types of toxic chemical substances. T o be sure, there is still concern about the input of phosphorus and thermal discharges into the Great Lakes. But, according to the Pollution from Land Use Activity Reference Group (PLUARG) of the International Joint Commission (IJC), toxic
chemicals have now become the predominant water-quality issue in the Great Lakes Basin. This concern is also shared at the‘national level by the President’s Council on Environmental Quality. What are toxic substances? Webster’s Seventh New Collegiate Dictionary defines toxic as something “of, relating to or caused by a poison or toxin”, where a poison is “a substance that through its chemical action usually kills, injures, or impairs an organism.” The Congress of the United States defined toxic substances in October 1976, when it enacted the Toxic Substances Control Act (Public Law 94-469). That law defines toxic substances as those chemical substances “whose manufacture, processing, distribution in commerce, use, or disposal may present an unreasonable risk of injury to health or the environment.” More specific definitions of a toxic substance and a hazardous polluting substance were included in the Great Lakes Water Quality Agreement of 1978, signed by the U S . and Canada on Nov. 22, 1978.
Numerous industrial chemicals, such as PCB’s, have been entering the environment for many years and, like DDT, have accumulated in living organisms including Great Lakes fish and in the people that consume them. PCB’s have been identified essentially everywhere in the world, despite the fact that they were produced for uses that should not have resulted in such widespread distribution. These uses included capacitors, transformers, and hydraulic fluids. Their careless use and disposal have led to ubiquitous contamination of the environment. Details about certain toxic chemicals, including lists of the so-called “priority pollutants”, were published recently by Larry Keith and William Telliard ( E S & T ,April 1979, p 416). These should be consulted for additional information. Distribution in water The extent of toxic-substances distribution in the water, sediments, and fish of the Great Lakes Basin is only now beginning to be understood. For example, a comprehensive inventory of information on the distribution of orVolume 13, Number 12, December 1979
1463
ganic and trace-metal contaminants in the basins of all of the Great Lakes, except Lake Ontario, has been prepared for a committee of the IJC's Water Quality Board by Dennis Konasewich and his co-workers. This inventory will serve as a basis for an assessment that will determine those contaminants that may present a hazard to human health and the environment. Data were obtained from municipal, state, provincial and federal agencies in the US. and Canada, as well as from reports and papers published by university researchers, government scientists and consulting firms. Among those groups that have performed considerable work and compiled extensive data on the Great Lakes are the Canada Centre for Inland Waters, the Ontario Ministry of the Environment, various EPA laboratories, the National Oceanic and Atmospheric Administration, and the natural resources departments of the Great Lakes states. Chemicals in Lake Michigan The most complete interpretive compilation of historical data for chemicals in Lake Michigan was published by Marguerite Torrey in 1976. N o similarly thorough treatise for the other Great Lakes has been prepared. At one time, organochlorine pesticides were widely used in the Lake Michigan Basin and were applied to forest and agricultural lands, and to noncrop lands. Pesticides were also used in industry and for household-pest control. According to a 1972 EPA report, the extensive use of DDT and dieldrin in Wisconsin led to the transport of these chemicals to Lake Michigan via tributaries, land runoff, and wastewater-treatment plants. Atmospheric precipitation was also implicated because of the wind-borne transport of these pesticides following aerial spraying. The concentrations of pesticides in the waters of the Great Lakes is relatively low, due partly to their low aqueous solubility. As reported by Torrey, typical concentrations were generally below 1 pg/L, and often near I ng/L. In addition to DDT and dieldrin, numerous other compounds were detected by gas chromatography, including PCB's, lindane, heptachlor, heptachlor epoxide, endrin, aldrin, and methoxychlor. Much of the early DDT and dieldrin data from Lake Michigan and other waters, prior to the late 196O's, are now considered only approximate because of the likely interference of PCB's in the analysis of these pesticides. 1464
Environmental Science 8 Technology
Torrey demonstrated that the concentrations of the main toxic inorganic materials (Hg, Pb, As) are quite low in Lake Michigan. There, inorganic substances do not appear to pose significant problems, except for As in the Green Bay area (currently being studied by Marc Anderson and associates a t the University of WisconsinMadison), and Pb in the southern basin. Distribution in sediments Great Lakes sediments are the ultimate sink for many, but not all, of the toxic contaminants that enter the lakes. Some of the contaminants, such as mercury, can be converted to more biologically active forms. Also, com-
A toxic substance means "a substance which can cause death. disnase. behavioral abnormalities, cancer, genetic mutations, physiological or reproductive illalfunctions or physical deformities in any organism or its offspring, or which can become poisonous after concentration in the food chain or in combination with olher substances." A hazardous polluting substance is defined to mean "any element or compound which, if discharged in any quantity into or upon receiving waters or adjoining shorelines, would present an imminent and substantial danger to public health or welfare. For this purpose. public health or welfare encompasses all factors affecting the health and welfare of man including but not limrted to human health, and the conservation arid protection of flora and fauna, public and private property, shoreline and beaches." Source: Great Lakes Water Quality Agreement of 1978, International Joint Commission
pounds such as PCB's are taken up by bottom organisms that either live or feed in the sediments, and which are subsequently eaten by larger carnivores. This results in an eventual increase in the concentration of this contaminant in carnivorous fish. Thus, despite the fact that the sediments are many meters below the water's surface, they do not always act as the ultimate sink for toxic substances. The presence of many contaminants in the Great Lakes sediments was summarized in the 1978 P L U A R G Final Report to the IJC. Of particular concern were Hg, Pb, and PCB's. A contour map prepared by PLUARG, showing the approximate distribution of mercury (Hg) in Great Lakes sediments, is reproduced as Figure 1. The highest 'Hg concentrations
generally appear in Lakes Erie, Ontario, and St. Clair. Previous industrial discharges, apparently current atmospheric deposition into the Great Lakes, and runoff from the land surface appear to be sources of Hg. Prior to 1970, major inputs into the lakes' system were discharges from the St. Clair and Detroit Rivers. On the basis of the sediment patterns, Lake St. Clair appears to be a continuing source of Hg to Lake Erie, despite the elimination of the chloralkali-plant source. The transport of Hg-enriched sediments from Lake St. Clair, through the Detroit River, and into western Lake Erie, continues to be a problem. The resuspension of Hg-contaminated sediments from western Lake Erie, and subsequent in-lake transport, has carried Hg along the southern shoreline and led to its ultimate deposition in the eastern basin. The western basin of Lake Erie is an active area of sediment resuspension because of windinduced wave action. In Lake Ontario, Hg appears to be carried by the Niagara River, with eventual dispersal throughout the eastern basin. The sharp decrease in point-source inputs of Hg to the lakes should result in a gradual decrease in Hg content of the surface sediments, according to PLUARG. The concentrations of most organic Contaminants in Great Lakes sediments have not been well mapped. PCB contours, however, were compiled by PLUARG for Lakes Huron, Erie, and Ontario. These indicate a general occurrence of PCB's in the sediments, with higher loadings in the western and southern areas of Lake Erie and in the south central area of Lake Ontario. The PLUARG Report estimated that nonpoint sources, including atmospheric inputs, account for the major reflux of PCB's to the lakes. Distribution in fish Data for PCB's in Great Lakes fish were compiled in the PLUARG Report with additional data provided by the State of Wisconsin. These appear in Table 1. The most significant PCB contamination occurs in Lake Michigan, according to data now available. One interesting aspect of PCB, DDT, and dieldrin contamination of fish in Lake Michigan is the slightly decreasing trend in concentrations that has developed over the past five to eight years. Data from the FWS and EPA indicate such a trend, but further analysis and monitoring will be required in the future to verify the trend. The PCB concentrations in fish can
vary from one season to another, as well as during spawning periods. Thus, fish monitoring programs must be conducted in a consistent manner to avoid bias in the interpretation of the data. One reason that PCB's continue to appear in relatively high concentrations in Lake Michigan fish is that the chemical is easily bioaccumulated; that is, passed through the food chain as smaller organisms are consumed by larger ones, ultimately reaching the primary carnivores in the lake (salmonids) which are highly prized sport fishery species. This process is illustrated in Figure 2 . Mercury concentrations in Great Lakes fish are not too much of a concern, except for those caught in Lake Erie. Concentrations from fish in that lake indicate that the FDA consumption guideline of I .Opg/g is still being exceeded, although trends of decreasing concentrations have been noted. The PLUARG Report noted that lead (Pb) concentrations are nowhere close to the recommended consumptionadvisory limit of I O p g l g in any of the Great Lakes. Effects of toxic substances One effect on citizens in the Great Lakes Basin, particularly those who consume relatively large amounts of locally caught fish, is contamination from certain species by chemicals, especially PCB's. Most of the species that have sport fishery importance, particularly the salmonids, consistently exceed the proposed FDA tolerance guideline of 2 pg/g in Lake Michigan. However, sportsmen are not prevented from consuming their catch, and many of these people are unwilling to abandon their sport (which involves considerable financial investment), particularly since toxicological studies have not conclusively linked the dietary intake of low levels of PCB's with human health problems. Despite the lack of firm human health evidence, there is ample documentation that the intake of PCB's near the FDA guideline significantly affects rhesus monkeys. James Allen and co-workers at the University of Wisconsin-Madison have shown that infants born to monkeys that were fed 2.5-5.0 p g / g of PCB's developed facial acne and edema, swelling of the eyelids, loss of facial hair including eyelashes, and hyperpigmentation of the skin. Half of the PCB-exposed infant monkeys died within eight months following birth, assumedly from PCB intoxication. Surviving infant monkeys proved to be hyperactive in locomotor tests, and to be slow in learning how to
Toxic substances: classes a n d sources According to the Great Lakes Basin Commission, the general classes of toxic substances that are presently of concern in the Great Lakes Basin are: halogenated organic compounds (PCB's, PBB's, chlorophenols), radioactive substances, pesticides, heavy metals and toxic nonmetals (Hg, Pb, As), and petroleum products. There are many sources for the toxic substances that enter the Great Lakes. The Great Lakes Basin Commission and others have itemized these as: * point sources (municipal- and industrial-effluent discharges).
nonpoint sources (land application of toxic materials followed by runoff; the atmosphere), urban runoff (Pb from automobile exhausts; grease and oil; metals; household pesticides), toxic and hazardous waste disposal sites or "phantom" disposal activities (legal or illegal waste disposal that results in the pollution of the Great Lakes; transportation accidents), the atmosphere (€S&T, November 1979, p 1337) (can be considered a nonpoint source but represents a major point of entry of PCB's, Pb and other toxic substances to the lakes), agricultural runoff (nonpoint source but emanates from specific useage of chemicals in agriculture).
TABLE 1
PCB concentrations in Great Lakes fish. Lake
Superior Michigan Huron Erie Ontario
Mean PCB concentrations' Pg/g
Sampling period
0.61 10.2
1968-1 975 1972-1974 1974-1978 1968-1976 1968-1976 1972-1977
NCb
0.82 0.88 2.37
Range Pgfg
