5
Threats to the Ozone Layer
Some of the key strategies used in regulating toxic chemicals, nuclear
power, and recombinant DNA are less applicable to technologies that pose atmospheric
threats. The potential catastrophe cannot be contained, as it can to a considerable extent
in a nuclear reactor or in a biological research laboratory. Once problems occur in the
atmosphere, the consequences cannot readily be reversed or mitigated as is possible with
some pesticides and other toxic substances. Yet changes in the earth's atmosphere are even
more potentially threatening than chemical or nuclear disasters. To put it callously,
humanity could do without Buffalo (Love Canal) or Harrisburg (Three Mile Island) much more
easily than it could live without a benign global atmosphere.
The following two chapters examine whether we have a system for coping
with such atmospheric threats. Chapter 6 deals with the greenhouse effect the climatic
changes that may result from increasing emissions of carbon dioxide and other gases.
Serious problems appear to be perhaps half a century in the future, so the greenhouse case
can provide insight into how society heeds early warnings and plans advance action. In
contrast, this chapter focuses on an atmospheric threat on which some action has already
occurred: possible depletion of the ozone layer that protects humans and other species
from excessive ultraviolet radiation.
77
Ozone is formed and destroyed by a large number of photochemical
processes in the upper atmosphere. For example, ultraviolet radiation from the sun
catalyzes the combination of atmospheric oxygen molecules with free oxygen atoms to form
ozone. The strongest concentrations of ozone occur in the upper stratosphere, some twenty
miles above the earth's surface.[1] This ozone layer absorbs
ultraviolet radiation and thereby substantially cuts down the amount that reaches the
earth's surface.
Initial Concerns
The SST
It was not until about 1970 that scientists began to realize that
human activities could damage the ozone layer and thereby alter climate and harm
terrestrial life. The first warning came in a Boeing Company scientist's internal report
that was not intended for public release. It suggested that exhaust gases from the
supersonic transport (SST) would induce a number of environmental changes, including an
increase in water vapor in the stratosphere that could lead to partial depletion of the
ozone layer.
This report was a result of Boeing's efforts "to answer the
opposition of conservation groups and the concerns of numerous independent
scientists" about the SST.[2] It had the effect of spurring
opposition, however, when the estimates were obtained and used by Representative Henry S.
Reuss (Democrat, Wisconsin), who was trying to mobilize Congress to withhold funding from
the SST project. The report's author, Dr. Halstead Harrison, later disavowed his original
conclusions, saying that they were early "back-of-envelope stuff" that had been
disconfirmed by more sophisticated analysis. According to Harrison, the early research was
part of a "devil's advocate exercise," and the calculations had been based on
worst-case assumptions about how the atmosphere works. Revised estimates showed that a
full fleet of SSTs might reduce ozone by "only 3.8 percent."[3]
Meanwhile, the Study of Critical Environmental Problems (SCEP),
sponsored by the Massachusetts Institute of Technol-
78
ogy, was examining the possibility that exhaust emissions from an SST
fleet could cause smog in the stratosphere in the same way that automobile emissions cause
smog at ground level. SCEP found that particles released into the stratosphere could
affect global climate and were therefore a source of "genuine concern"; but
"reduction of ozone due to interaction with water vapor or other exhaust gases should
be insignificant."[4] Unknown to SCEP, however, other
atmospheric scientists doing basic research unrelated to the SST issue were rapidly
improving their understanding of the chemical reactions that affect ozone in the
atmosphere; their findings suggested that water vapor was not the critical factor in the
ozone balance.
Stimulated partly by this emerging information and partly by a federally
sponsored conference on SST environmental problems, atmospheric chemist Harold S. Johnston
performed calculations in early 1971 that suggested nitrogen oxides from SST exhausts
would pose a much greater threat to the ozone layer than would water vapor. A full fleet
of five hundred SSTs operating for seven hours per day could destroy up to half of the
earth's ozone layer, not the small percentage that other scientists had estimated based on
the belief that water vapor was the threat. The New York Times reported that
Johnston had predicted that such a change would occur in less than a year after a full SST
fleet began operations, but Johnston made a far more cautious appraisal in his article in Science
.[5]
Numerous other factors affected the 1971 congressional decision not to
approve construction of a supersonic transport jet. Key concerns were the effects of sonic
booms in populated areas and the high cost of the project, but the ozone threat was also a
significant drawback.
The Effects of Fluorocarbons
A second threat to the ozone layer was suggested in late 1973 by
University of California chemists Mario J. Molina and F. Sherwood Rowland. They proposed
that fluorocarbons from aerosol propellants, refrigerators, and air conditioners could
79
pose a severe threat to the ozone layer.[6]
Such ozone damage, in turn, "might cause awesome changes in the earth's weather and
ecology, including damage to wildlife and crops."[7] Each
percentage decrease in ozone, the scientists theorized, would result in a 2 percent
increase in skin cancer. Published in June 1974 in Nature , this theory received
immediate attention from the scientific community, the media, and government.[8]
Fluorocarbons, also called halogenated chlorofluoromethanes (CFMs),
chlorofluorocarbons (CFCs), or halocarbons, are organic chemical compounds not found in
nature. They are synthesized from carbon, chlorine, and fluorine. Chemically inert, they
do not react with most substances. This means that they are not toxic, and are excellent
for aerosols because they will not contaminate the product. Because they are nonflammable,
fluorocarbons are much safer in refrigerators and air conditioners than are the available
substitutes, such as ammonia, methyl chloride, and sulfur dioxide. Fluorocarbons have been
used as refrigerants since the 1930s and in aerosols since the Second World War.
The potential threat posed by fluorocarbons is that they are complex
molecules that can be broken down into their constituent atoms under certain conditions.
The Molina-Rowland theory specified five steps to the process:
1. Fluorocarbons are carried by winds to the stratosphere; this process
can take as long as ten years.
2. Once in the stratosphere, the fluorocarbon compound is broken down by
ultraviolet light into its constituent chemicals, including the element chlorine.
3. The released chlorine reacts chemically with ozone to convert it to
atmospheric oxygen, which is less effective than ozone in absorbing ultraviolet radiation.[9]
4. Subsequent chemical reactions allow a single chlorine molecule to
continue to interact with tens of thousands of ozone molecules; thus, there is a
substantial multiplier effect.
5. Ozone depletion allows more ultraviolet radiation to reach the
earth's surface, resulting in an increase in skin
80
cancer among susceptible individuals and perhaps harming crops and
animals. Ozone depletion also may alter the temperature of the stratosphere and thereby
alter global weather patterns.
Confirmation of the Fluorocarbon Theory and Risks
As in the case of recombinant DNA (and as distinguished from the case
of nuclear power), a majority of scientists quickly became convinced of the accuracy of
the Molina-Rowland theory of ozone depletion. How did such agreement come about?
As with rDNA, the ability to test for risks appears to have been the key
factor in this agreement. Fellow researchers quickly tested various components of the
theory. By late 1975 the physicist Arthur L. Schmeltekopf of the National Oceanic and
Atmospheric Administration reported that "fluorocarbons are getting to the
stratosphere in the predicted amounts."[10] This finding was
based on air samples collected by weather balloons at heights of up to 17.4 miles
(midstratosphere).
The same experiment also helped confirm that fluorocarbon compounds were
being broken down in the stratosphere. Above a level of about 9.3 miles, the amount of
fluorocarbons in the air samples began to diminish, and only traces remained at the
highest levels sampled. So it was clear that "something is destroying the
fluorocarbons . . . at the rates predicted by theory."[11]
Other independent experiments, conducted under laboratory conditions
rather than in the stratosphere, found that fluorocarbon molecules split when bombarded by
light from ultraviolet lamps. Depending on conditions, either one or two chlorine atoms
were released from each fluorocarbon molecule. From these experiments, National Bureau of
Standards chemist Peter J. Ausloos concluded that "we have proved beyond any doubt
that you get chlorine atoms when a photon [of light] is absorbed by the fluorocarbon
molecule."[12]
So the first steps in the Molina-Rowland theory had been quickly
confirmed; even the affected industries conceded this point within about a year. But would
fluorocarbons break
81
down ozone under the actual conditions prevailing in the atmosphere?
Direct measurements of ozone levels had been made for other purposes since the late 1950s,
and steps were taken to expand and supplement these measurements. Interpretation of the
results was difficult, however, because ozone levels fluctuate daily by as much as 25
percent, vary with the season, and differ markedly over various parts of the globe. As a
result, most scientists doubted that direct measurements could be used to confirm the
Molina-Rowland theory until about 5 percent ozone depletion had occurred. Only then would
any depletion caused by human activity be dramatic enough to distinguish it from natural
variances.
Scientists resorted, therefore, to less direct methods of testing the
hypothesized chlorine-ozone reaction. If such a reaction were occurring, there would be
other changes in the chemistry of the stratosphere, and some of these changes might be
easier to measure than ozone. For example, some of the chlorine released from
fluorocarbons would be expected to form hydrochloric acid (HCl). Scientists at the Jet
Propulsion Laboratory (at California Institute of Technology) designed experiments using
U-2 flights and weather balloons to measure HCl levels in the stratosphere. Finding higher
HCl concentrations in the upper atmosphere than at lower levels, they concluded: "The
results show very clearly that there is a stratospheric source of hydrochloric acid that
it doesn't get there in that form from the earth."[13]
A variety of other experiments likewise contributed to the validation of
the Molina-Rowland hypothesis.[14]
At this point political judgment had to be exercised. Granted that
fluorocarbons would have some effect on atmospheric ozone, was the effect significant
enough to regulate? Various interest groups, scientists, and governments had substantially
different answers to this policy question.
Industry argued that the ozone-depletion theory should be proven before
the government took regulatory action. Some $400 to $450 million per year in fluorocarbon
product sales were at stake in the United States alone. In the words of an industry
spokesperson, there was "enough doubt to warrant making a better test in nature
before demolishing a major industry."[15] As
82
expressed in one 1975 industry paper: "The questions aren't just
whether the theory's general premises are valid, but also whether the magnitude of any
ultimate effect is meaningful to the quality of the environment and public health."[16]
The American Chemical Society complained during the height of the
dispute that any restriction on fluorocarbons would constitute "the first regulation
to be based entirely on an unverified scientific prediction." Such an action, the
professional group declared, would set "a very dangerous precedent."[17] Likewise, a DuPont spokesperson protested proposed regulations,
arguing that "what's happening is disturbing and alarming. We're going a very long
way into the regulatory process before the scientists know what's really going on."[18]
Government advisory bodies, in contrast, recommended quick action to
prevent potential dangers. In 1975, just one year after the original publication of the
Molina-Rowland theory, a federal task force reported that fluorocarbons constituted
"a legitimate cause for concern." Unless new evidence contradicted the data then
available, the task force concluded that fluorocarbons should be banned for newly
manufactured refrigerators and air conditioners. It was taken for granted that
fluorocarbon aerosols should be banned.[19] As a result, the
Environmental Protection Agency conducted an economic impact assessment of possible
regulations for limiting the fluorocarbon threat.[20]
A panel of the National Research Council (NRC) was convened in 1975 to
again review the evidence of fluorocarbon dangers. Reporting in spring 1976, the panel
scaled down the depletion estimate but confirmed the existence of a potentially severe
danger.[21] Additional federal studies followed in rapid succession
and averaged at least one per year through 1984.[22] While the
United States led the way, research was intensified in almost every industrial nation,
typically under governmental sponsorship.[23]
Governmental Restrictions on Fluorocarbons
The Molina-Rowland ozone theory had reached the major newspapers by
fall 1974, and it was the subject of a
83
congressional hearing that December.[24] In
1975 additional hearings were held before the House Commerce Committee, the House Science
and Technology Committee, and at least one committee in the Senate. As a result, the House
Commerce Committee added an ozone provision to the Clean Air Act amendments of 1977.
This legislation called for research and periodic assessment of the
ozone-fluorocarbon problem and gave EPA until late 1978 to issue regulations restricting
or banning the use of fluorocarbons in aerosol sprays if the agency concluded that the
chemicals could "reasonably be anticipated to cause or contribute to the endangerment
of public health or welfare." (The legislation authorized EPA to issue regulations
even earlier if the agency found a "significant risk" from the sprays.) Although
EPA waited for an NRC report, which recommended that action be delayed pending further
study, EPA went ahead and banned most aerosol uses of fluorocarbons in 1978. There were a
few exemptions for high priority needs where available substitutes were considered
unsatisfactory (for instance, for some pharmaceuticals in spray form). U.S. manufacturers
had begun to phase out aerosols well before the legislation and subsequent ban took
effect.
The 1977 Clean Air Act also authorized EPA to propose restrictions on
nonaerosol sources of fluorocarbons. The agency considered banning the use of fluorocarbon
refrigerants but retreated from the idea, partly in response to manufacturers' arguments
that economic substitutes were not available. Instead, EPA in 1980 proposed a rule to
limit increases in overall U.S. production of fluorocarbons (there are further details
later in this chapter). These proposed production limits resulted in some two thousand
formal complaints, with much of the opposition coming from a coalition of about five
hundred corporations called "The Alliance for Responsible CFC Policy."
Nevertheless, EPA announced in March 1982 that regulations would soon be proposed that
would limit fluorocarbon production to 1981 levels, but no proposal was ever actually
made.
By 1980 only Sweden and Canada had joined the United States in banning
fluorocarbon aerosols. Denmark and Nor-
84
way soon followed suit, but a majority of European nations did not.
The European Economic Community subsequently cut back on aerosols to some extent and has
halted construction of additional fluorocarbon manufacturing capacity.[25] Since existing capacity is expected to be underutilized until
the turn of the century, this step has had no real effect on emission levels. The United
States, Canada, and a handful of other nations have continued trying to persuade the
majority of nations to adopt tougher controls on fluorocarbons. In 1985 forty-three
nations signed an international treaty providing for cooperative research and agreed to
meet in 1987 to consider formal international controls. As part of the pact, the Soviet
Union for the first time agreed to provide information on its fluorocarbon usage.[26]
Fertilizers and Other Threats
While research on fluorocarbons was proceeding, it became apparent
that there could be other sources of damage to the ozone layer. Nitrogenous fertilizers
were identified as a threat in 1974; like the SST, they too contribute nitrogen oxides to
the atmosphere. Most nitrogen oxide is produced in the oceans and is thus not within human
control; human-induced changes in soil acidity (for instance, from acid rain) and use of
nitrogen fertilizers are the principal ways humans add to the natural rates of nitrogen
oxide production.[27] In 1976 the first quantitative estimate of
possible ozone depletion from fertilizer was calculated at approximately 10 percent.[28] Other scholars pointed to the partially offsetting effects of other
atmospheric and soil chemistry processes that could be expected to reduce the extent of
the problem from fertilizers.[29]
By 1977 increases in worldwide fertilizer use led one scientist to argue
that this source could constitute the principal long-term threat to the ozone layer (see
Figure 2).[30] A 1978 NRC report partially endorsed this view.[31] Subsequent NRC ozone studies have given about equal attention to
nitrogen oxides and fluorocarbons and have also begun to explore other trace gases that
pose depletion threats.
85
Figure 2.
World fertilizer use in megatons
Source: "Will Fertilizers Harm Ozone as Much as SSTs?,"
Science 195 (1977): 658.
86
Shortly after the SST controversy, an environmental scientist reported
that methane produced indirectly by human activities could pose a threat to the ozone
layer.[32] Like nitrogen, methane reacts chemically with individual
oxygen atoms and reduces the number of free oxygen atoms available to form ozone. Methane
is produced primarily by decaying vegetable matter and by intestinal food digestion. Major
sources include paddy fields fertilized with human and animal wastes, swamps, and the
flatulence of domesticated cattle. While it seems almost a joke, this latter source
contributed an estimated 150 million tons of methane to the atmosphere in 1981, a 75
percent increase in just one decade. Termites recently have been shown to produce levels
of methane that could be significant when added to other sources. Incredibly, there are
approximately 100 million termites (equal to three-quarters of a ton) for every human on
earth, and the combined effect of their methane production rivals that of cattle.[33]
A 1979 NRC report drew attention to another potentially significant
threat to ozone methylchloroform. It is used widely as an industrial degreasing solvent,
and production of the chemical has been doubling every five years. Less inert than
fluorocarbons (so more is destroyed before it can reach the upper atmosphere),
methylchloroform nevertheless could lead to substantial ozone depletion if its use
continues to increase rapidly.[34] A number of other trace gases of
which carbon tetrachloride is the best known also carry ozone-depleting chlorine into the
stratosphere, and production of most of these chlorocarbons is increasing steadily.[35]
Another chemical that is gaining attention is bromine. Methylbromide now
is the largest source of the chemical and its production increased more than 400 percent
between 1972 and 1984. Organic bromine also comes from ethylenedibromide, an additive in
leaded gasoline and a now-restricted fumigant for agricultural produce. Two of the minor
fluorocarbons also contain bromine; their use as fire extinguisher chemicals has been
increasing, and atmospheric concentrations have gone up by more than 10 percent annually
in recent years. Altogether, if organic bromine concentrations grow by another 400
percent, they could lead to destruction of 4 to 5 percent of global ozone
87
in addition to the depletion caused by chlorine compounds such as the
major fluorocarbons.[36]
Ozone Depletion
A Declining Threat?
Refined computer models of the ozone balance and new information about
the rate of key chemical reactions have been developed almost every year since 1970.
Frequent changes in estimates of ozone depletion have been the result.
A 1979 NRC report suggested eventual ozone depletion at about twice the
level indicated in 1976. Continued production and use of ozone-depleting chemicals at
current rates, the panel said, would eventually lead to destruction of about 16.5 percent
of the world's total stratospheric ozone. Growth in fluorocarbon use, to be expected in
the absence of international controls, would exacerbate the problem still further. If the
projected 7 percent annual increase in fluorocarbon production occurred up to the year
2000, for example, the panel estimated at least a 30 percent reduction in ozone.[37]
After 1979, however, depletion estimates began to decline. In 1982 the
NRC reverted to estimates closer to the 1976 report in the range of 6 to 12 percent. The
NRC projected significantly reduced ozone depletion in the lower stratosphere, in part
because recent studies had drawn attention for the first time to unexpected sources of
ozone production.[38] Aircraft that fly below an altitude of about
ten miles, for example, release nitrogen oxides that undergo chemical reactions to form
ozone. This recent research also had begun to take into account the greenhouse effect from
heating of the earth's lower atmosphere; this is expected to cool down the stratosphere
and thereby slow rates of ozone destruction and speed rates of ozone formation.
Research on the stratosphere and its ozone balance had made enormous
progress by 1982. Some discrepancies remained between actual measurements of chemicals in
the stratosphere and estimates provided by computer simulation models, but these
discrepancies had been reduced greatly in the course of a decade. Even technical prose
could not dis-
88
Figure 3.
Changing ozone depletion estimates
Source: Adapted from National Research Council,
Causes and Effects of Changes in
Stratospheric Ozone: Update 1983
(Washington, D.C.: National Academy Press, 1984).
guise many scientists' beliefs that the models were accurately
reflecting the true state of the ozone balance. Of one important discrepancy concerning
chlorine oxide, for example, the 1982 NRC report said: "Those of us who believe there
are grounds to judge the effect [of resolving the discrepancy] . . .
conclude that our estimate of ozone reduction from CFC emissions should not change [go up]
by more than a factor of two."[39] In other words, they
expected that the 1982 prediction would remain relatively stable over time.
But in 1983 new information led to further reduction down to just 2 to 4
percent in estimates of ozone depletion. The NRC Committee went so far as to suggest that
ozone might even increase by 1 percent![40]
Altogether, as shown in Figure 3, estimates of ozone depletion declined
steadily from 1979 to early 1984. There was reason to have greater confidence in these
later estimates, since models of the atmosphere now describe some two hundred chemical
reactions over twice the number used in 1974 and the rates of many reactions now are much
better known. It began to seem that the ozone controversy was over.
In late 1984 and 1985, however, the picture again changed
89
for the worse. New research by Harvard scientists indicated that ozone
depletion is not linear beyond a certain point.[41] Within two
generations, if use of ozone-depleting chemicals continues to increase at the pace set in
recent years, concentrations of trace gases in the lower stratosphere could be high enough
to trigger an exponential rate of depletion. If so, the scientists calculated, eventual
depletion would total approximately 15 percent almost the same as had been estimated in
1974. A 1985 EPA background paper suggested that even greater ozone destruction is
possible, given the sharp increase in fluorocarbon usage that began again in 1983 after
nearly a decade of reduced sales.[42] The concept of exponential
depletion spurred renewed activity by environmental interest groups, including a federal
lawsuit filed by the Natural Resources Defense Council that asked that EPA be required to
issue more stringent regulations against ozone-depleting chemicals.[43]
The recent depletion estimates are not as different from those of
immediately preceding years as they may seem. The 1983â84 NRC report
acknowledges that "total ozone could decrease substantially, perhaps by as much as 10
percent by 2040" under certain circumstances.[44] However, the
NRC emphasized a lower figure, as did the media. Why was this? Depletion estimates have
always depended on two factors: the rate of depletion induced by a given volume of each
chemical, and the amount of each ozone-depleting chemical produced and released into the
atmosphere. Only the first factor is scientifically determinable; about the second,
scientists have no special expertise, since production levels of chemicals are determined
by political and economic factors. Instead of explicitly calling attention to the
inevitable uncertainty introduced by this factor, however, most ozone reports have quietly
made sensible guesses. Now, for the first time, different groups of scientists are
publicly disagreeing about their guesses.
Elements of the Regulatory Strategy
The United States led most of the world in considering the threat to
ozone as a danger deserving active response. While there were several serious shortcomings
in translating
90
science into public policy, there also were conspicuous strengths.
Overall U.S. ozone policy has displayed a very sensible sequence: scientific monitoring
revealed a variety of threats; selective actions were taken to limit the potential damage;
and further research and debate attempted to reduce remaining uncertainties and thereby
clarify the need to implement more stringent regulatory measures.
Detecting the Threat
The first strategy, not evident except in retrospect, was deployment
of diverse scientists in academic, governmental, and industrial research institutions.
These atmospheric chemists and other specialists established a framework within which the
ozone problem could begin to be understood. These early researchers were not looking for
atmospheric threats but were merely pursuing their own relatively esoteric interests
concerning atmosphere and climate. Some were employed by institutions with practical
objectives, such as weather forecasting, but most were simply part of the large network of
scientists that has developed over the past century. Without anyone planning it, this
network has come to constitute an early warning system to alert society about physical
threats to the environment and to human health and safety.
This scientific community also provides a means for determining whether
the first warnings about a potential threat should be taken seriously. Once Molina and
Rowland had offered a speculative theory about the risks of fluorocarbons, their idea was
broken down into many smaller, more comprehensible parts; scientists from diverse
specialties clarified small parts of the complex theory and reached consensus on its basic
accuracy. Thereafter, prestigious National Research Council committees synthesized
available scientific knowledge and made this information comprehensible to policy makers.
All these are common approaches to complex problems with substantial technical components
and are unremarkable except for the fact that many people still do not recognize them as
standard operating procedures for monitoring risks.
91
While it is comforting that scientists have been attempting to clarify
the extent of the ozone threat, can we count on scientists to attend to other potential
problems from risky technologies? What will draw scientific attention to problems that
society needs diagnosed? The case discussed in this chapter indicates at least three
incentives.
First, the pioneering efforts of early scientists were stimulated
primarily by intellectual curiosity and ordinary career considerations. At a later stage,
these motives combined with a desire to help clarify how society should respond to a new
threat. (The SST analyses and the series of NRC reports on fluorocarbons are the best
examples.) Finally, additional scientists were drawn in when increased funding became
available after government was pressed to action by interest groups and concerned
government officials. Much of the research on atmospheric threats since about 1975
probably falls in this category. The key point is that all of these routes for focusing
scientific attention are predictable ones that we see repeated in many different policy
areas. They are part of society's implicit strategy for averting catastrophes.
Protecting against the Threat
Once scientists had narrowed the range of credible dispute, the U.S.
government acted very rapidly in the SST and fluorocarbon aerosol cases. Other nations
moved more slowly, if at all, against these threats, and no nation so far has taken action
against the other ozone depleters.
No one knew for sure in the mid-1970s whether there would be any ozone
destruction since direct evidence would not be available until several percent depletion
had occurred. But if depletion were occurring, it could have very severe results.
Faced with this possibility, the least risky approach would have been to ban all
ozone-depleting chemicals, but this policy would have been extremely costly, if not
impossible, to implement. Hence, EPA pursued a more expedient approach: it banned most
aerosol sprays while permitting the continued use of fluorocarbons for refrigeration and
other purposes considered more essential. Thus, if fluorocarbons
92
turned out to be a problem, at least some reduction in the magnitude
of the consequences would have been achieved at an acceptable cost.
Monitoring and Debate
The ban on aerosols can be seen as a way of buying time for additional
research; it slowed down any ozone destruction caused by U.S. fluorocarbon usage and
thereby gained time to determine the magnitude of the threat. In effect, the strategy was
to first take readily achievable steps to at least partially protect against the potential
hazard and then attempt to reduce uncertainty about the threat before taking more
stringent precautions.
This two-step approach also provided time for political innovation and
debate. In its 1980 proposal for regulating nonaerosol fluorocarbons, EPA borrowed and
extended a distinctive new tactic from Europe: a ceiling on overall production levels and
an auction among competing manufacturers to bid for rights to produce fixed quantities of
fluorocarbons.[45] As simple as this seems, the idea of
quantitative limits on dangerous activities is still relatively novel. The usual approach
is to allow activities to occur with unlimited frequency but to restrict the amount of
hazard posed by each one; emission controls on automobiles are a typical example.
The second part of the proposal was also innovative. Since manufacturers
would have to raise their prices to cover the fees paid to EPA, consumer demand for
fluorocarbons probably would drop somewhat. But if demand still exceeded supply, prices
would go up until some former fluorocarbon users switched to cheaper substitutes. Thus,
"the marketplace would determine what kinds of products using fluorocarbons were
produced within the overall limit."[46] This idea of sing
market-like procedures in place of ordinary command-and-control regulations was championed
by many economists during the 1970s, and there have been several experiments with
pollution taxes and licenses. But in 1980 it was an innovative approach for a major
regulatory endeavor, and it still remains far from ordinary. While EPA did not actually
use these tactics in the
93
ozone case, they now are part of the repertoire available for dealing
with future threats.
Evidence in the early 1980s seemed to suggest that additional
restrictions would not be necessary on production and use of ozone-depleting chemicals.
Subsequently, however, fluorocarbon production began to increase rapidly, and new
scientific evidence suggests that ozone depletion may be exponential rather than linear.
Moreover, the foam-blowing industry is becoming a large user of fluorocarbons, and molded
seat cushions are hardly as essential as refrigerants. So there is reason to expect
renewed debate about the imposition of more stringent controls on fluorocarbons.
Shortcomings of the Strategy
While the U.S. ozone strategy followed a sensible overall course, it
had several important limitations. First, the handling of the ozone episode may have
reinforced an already excessive tendency of policy makers to substitute scientific
analysis for judgment and strategy when regulating risky technologies. When the magnitude
of the threat is very uncertain, as it was in this case, scientific analysis has a way of
dressing up as "fact" conclusions that actually are based on judgment. Each NRC
depletion estimate contained implicit judgments about future increases in use of
ozone-depleting chemicals. This did not invalidate the scientific components, but it
obscured the tasks facing policy makers.
In considering options for dealing with the ozone threat, the key issue
is whether or not to limit increased use of certain chemicals. So growth rates and their
effects on depletion estimates are the critical variables. If policy makers are not
explicitly made aware of what to expect at low, medium and high rates of increase, they
cannot readily monitor whether chemical usage is remaining in the range judged to be an
acceptable risk. The NRC ozone committees did not hide their judgments about future
increases of ozone-depleting chemicals, but neither did they set forth separate scenarios
in case actual growth rates proved higher or lower than expected. Moreover, studies of
changes in usage rates for the various chemicals
94
have not been as extensive or as sophisticated as contemporary
economic analysis permits.
A related shortcoming in the ozone case concerns society's ability or
willingness to respond to a threat. Although it seems counterintuitive, concern about
ozone depletion went down as the number of actual threats went up. First, the SST and then
fluorocarbons were the focus for alarm, and both evoked considerable public concern. But
this concern diminished thereafter, well before scientific evidence became more
reassuring. This could be a simple attention-cycle phenomenon, in which the media and the
public simply got tired of ozone stories. Or perhaps the problem was too complex "If
it is too hard for me to grasp, I don't want to hear about it."
Furthermore, some of the newer sources of ozone threats, such as
nitrogenous fertilizers, are more central to contemporary economic activity and have
stronger political constituencies than did the SST and aerosol fluorocarbons. Even if the
1985 estimate of 15 percent depletion survives further scrutiny for a number of years,
powerful interest groups are likely to oppose regulatory action in the name of waiting for
reduced uncertainty. A political paralysis can thereby develop, based in part on a hope
that the next scientific report will have discovered new ozone-producing processes that
will make ozone depletion less of a threat. Waiting certainly is easier than deciding how
to act, given the factual uncertainties and the known economic costs of regulatory
strategies.
In some ways, waiting is intelligent: when a broad range of interests
would be affected by regulatory action, it often makes good sense to wait for greater
certainty about the threat before taking costly curative actions. Unfortunately, it is
difficult to draw the line between prudent waiting and shortsighted preservation of
interest.
A third problem revealed in the ozone case is the difficulty of taking
concerted action against international threats from risky technologies. Even though it
would have been relatively easy to do, many nations did not ban fluorocarbon aerosols. If
the ozone threat had materialized as expected in the mid-1970s, considerable damage would
have been done before all nations had unambiguous evidence of the danger. In spite of a
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number of global environmental threats in addition to ozone depleters,
there still is no institution strong enough to impose a global perspective on
international, national, and industry decision makers. The result is a typical example of
the so-called tragedy-of-the-commons predicament: any nation that restricts dangerous
products penalizes itself economically and does little to impel global action.
Fortunately, U.S. aerosol usage comprised a large percentage of global
fluorocarbon production in the 1970s. Hence, unilateral action by the one nation could
temporarily reduce whatever threat the entire world faced. But growing use of a wide
variety of ozone depleters throughout the world means that no single nation will be able
to have much effect in the future, if additional restrictions come to be warranted.
Finally, the ozone case raises in a new way an issue common to every
technological risk in this volume: How safe is safe enough? While the United States took
sensible initial precautions against fluorocarbons, even greater caution might have been
warranted. It requires as much as a century for atmospheric processes to decompose
fluorocarbons; so, if conclusive evidence of ozone depletion were obtained this year and
all implicated chemicals were banned immediately, ozone depletion would continue for many
years because of the chemicals already put into the atmosphere. There would be a long
delay, then, before the effects of an error in ozone policy could be corrected. Under such
circumstances, it might make sense to proceed very cautiously in order to avoid getting
trapped in an ozone-depletion sequence that could not be halted. More precautions would be
costly, but so is inadequate caution. We will have more to say about the "How
safe" question in chapter 8.
