66 THE FIVE-YEAR OUTLOOK 



trends toward increased atmospheric concentrations of 

 that substance. Coal use is especially problematic, be- 

 cause coal's low hydrogen-to-carbon ratio leads to the 

 release of larger amounts of CO2 for a given amount of 

 heat than other fossil fuels (NRC-15). 



The precise relationship between fossil fuel use and 

 atmospheric COi levels is not yet fully understood, nor is 

 the range of potential effects that increased CO: levels 

 might have. However, significantly increased atmospheric 

 concentrations of CO, could have far-ranging con- 

 sequences. For example, a doubling of current at- 

 mospheric CO: levels could result in marked changes in 

 Earth's climate, by as much as several degrees in some 

 regions (NRC-15). Those climatic changes, in turn, could 

 have very broad effects, including adverse effects on the 

 productivity of prime agricultural land and flooding of 

 coastal areas due to partial melting of polar ice. Thus, 

 although there remains considerable uncertainty about the 

 precise relationships among fossil fuel use, CO2 release 

 into the atmosphere, and consequent effects on world 

 conditions, there is general agreement that excessive 

 burning of fossil fuels could be accompanied by the se- 

 rious danger of upsetting world climatic and ecological 

 conditions. There is still considerable uncertainty about 

 how rates of increase in the atmospheric concentration of 

 CO: are related to rates of fossil fuel combustion, about 

 global atmospheric circulation patterns, and about the rate 

 at which CO: can be reabsorbed by vegetation and the 

 oceans (ENERGY). A high priority during the next 5 

 years will be to learn more about the details of the CO: 

 problem so that information can be factored into long- 

 range global energy and environmental planning 

 (NRC-15; ENERGY). 



ACID PRECIPITATION 



A second, more immediate problem associated with, and 

 exacerbated by, fossil fuel combustion is acid precipita- 

 tion, most frequently identified as '"acid rain." Rainfall is 

 generally slightly acidic, with a normal pH of 5.6. 

 However, reports place current rainfall pH levels in certain 

 parts of the eastern half of the United States at 4.0 to 4.5, 

 with some recorded levels as low as 3.0 — in other words, 

 at the acidity level of lemon juice.' 



The two principal artificial sources of precursors to acid 

 rain are oxides of sulfur and oxides of nitrogen, both of 

 which are products of the combustion of contaminants in 

 coal and oil (ENERGY). Emissions of sulfur and nitrogen 

 oxides can react in the atmosphere to form sulfuric and 

 nitric acid, which precipitate out with rain or snow, some- 

 times hundreds or thousands of miles from the emission 

 source. The acid precipitation can have effects on fish 

 survival, forest growth, communities of aquatic orga- 

 nisms, biomass production, survival of amphibian spe- 

 cies, and agricultural yields. Such effects are widespread 

 in eastern North America and the Western United States 



and are now recognized as major problems in Japan and 

 northern Europe. 



The control of acid rain through point source regulation 

 of stack emissions is difficult because sulfur and nitrogen 

 oxides do not show up on monitors of ambient con- 

 centrations of those substances, because of long-range 

 transport problems, and because of the increasing practice 

 of emitting gases through extremely tall stacks. The latter 

 practice avoids ground-level concentrations but can lead 

 to high-altitude mixing and chemical transformation, 

 which complicate accurate source tracing.' Some progress 

 is being made through industrial emission control efforts, 

 but continued national and international cooperative re- 

 search will be needed on the identification, control, and 

 monitoring of the sources; transport media; chemical 

 transformations; and environmental and health effects of 

 the oxides of sulfur and nitrogen. 



MANAGING HAZARDOUS AND TOXIC 

 SUBSTANCES 



The products of the U.S. chemical industry have yielded 

 enormous benefits to society in the form of fertilizers, 

 pesticides, pharmaceuticals, synthetic fibers, disinfec- 

 tants, and a host of other products now routinely used in 

 agriculture, industry, commerce, and medicine. Along 

 with those benefits, however, are a number of associated 

 known or suspected dangers to human health and to the 

 environment. Many chemicals are vital to human survival 

 in low concentrations, but highly toxic in higher con- 

 centrations; others are highly toxic at all concentrations. 

 Some are highly persistent and do not break down physio- 

 chemically or degrade biologically; certain otherwise 

 harmless chemicals can interact to form highly toxic 

 agents, pollute the atmosphere, and contaminate ground- 

 water supplies (Outlook I). 



Recognition of the dangers to human health and the 

 environment has spawned a substantial body of legislation 

 to control hazardous and toxic substances, including the 

 Toxic Substance Control Act and culminating in the pas- 

 sage in December 1980 of the Comprehensive Environ- 

 mental Response. Compensation, and Liability Act (the 

 so-called "Superfund" bill). The latter provides for a 

 cleanup fund for hazardous substance spills and for neu- 

 tralizing inactive hazardous waste disposal sites. ^ Over 

 the next 5 years, additional scientific and technological 

 activity will be important for learning more about con- 

 taining emergency spills and treating and disposing of 

 hazardous wastes. 



EMERGENCY SPILLS 



Hazardous wastes are typically thought of as those that are 

 ignitable, corrosive, reactive, or toxic. About 15,000 



