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Second Thoughts on an Acid-Rain Bill
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12205 |
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Section : |
CURRENT ISSUES
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| Issue
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2 / 1987 |
1,592 Words |
| Author
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S. Fred Singer
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Congress is at it again. The 100th Congress is pushing for an acid-rain bill, a "tough" piece of legislation that virtually mandates expensive retrofits of flue-gas scrubbers to existing coal-fired boilers and further tightens automobile emissions to nearly impossible standards.
However, recent scientific evidence indicates that the efficacy of these approaches is very much in doubt. Even if more emissions reductions led to corresponding decreases in rain acidity and ecological impacts - by no means sure - is it worth the cost? Or is the bill simply a billion-dollar solution to a million-dollar problem, as its opponents claim? That question has to be addressed by a cost-benefit analysis, so far nonexistent.
The scientific chain between emissions and acid rain consists of three links: It requires knowledge about the emission of polluting gases into the atmosphere, the acidity of precipitation, and the ecological effects on soils and water. The evidence for all three can best be described as confused and confusing.
For instance, the Environmental Protection Agency (EPA) has been saying for several years that emissions of sulfur dioxide (SO2) have decreased significantly, by 24 percent since the passage of the 1970 Clean Air Act. While that is still the EPA position, a National Academy of Sciences (NAS) report released in March 1986 claims instead a 20 percent increase in SO2 in the Eastern United States between 1970 and 1980. The NAS report dutifully records its disagreement with the EPA and explains, rather unhelpfully, "These differences undoubtedly arise from the different assumptions employed in deriving the estimates." With this basic historical datum in dispute, how can one decide on policies to control future SO2 emissions?
Direct effect?
The scientific controversy sharpens when considering to what extent a reduction in emissions will reduce the acidity of rain. Will removing 50 percent of the emitted SO2 reduce acid deposition by the same amount? No one really knows if the relation is linear; in any case, natural rain is quite acidic, even without industrial emissions. An earlier (1983) NAS report hedges: "There is no evidence for a sharp non-linearity in the relationship between long-term average SO2 emissions and sulfate depositions." But even this rather weak conclusion, based on incomplete historical data, is said to apply only to eastern North America. The report acknowledges strong nonlinearities between SO2 emission and sulfate depositions in European data but shrugs off this important finding by claiming that Europe is different.
(Kenneth Mellanby, a noted ecologist and chairman of a United Kingdom acid-rain commission, has pointed to the fact that a 30 percent reduction in British SO2 emission [thanks to the use of clean North Sea gas] has had little influence on the acidity of bodies of water in Scandinavia.)
Another distinguished group of scientists, the Defense Department-supported Jason group, concluded in its 1983 report that a reduction of SO2 emissions may not always be effective. The limiting item in the complex atmospheric chemistry of acid rain may be oxidants, produced largely by nitrogen oxides (NOX) emitted about equally by mobile and stationary sources. Clearly, the final
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