Flooding in Vaison-LaRomaine (Vaucluse)
Source: Chardon-Martin, Gamma, Frank Spooner Pictures
INTRODUCTION |
Naturally occurring hazardous events and technological accidents are separate causes of environmental impacts. The information available on their occurrence and consequences is far from comprehensive (Box 18A) and, in particular, there are significant gaps in our understanding of the long-term environmental impacts of accidents. However, on the basis of data which are available from a range of sources, it is possible to indicate how these two kinds of events are different and why they need to be treated separately from other pressures. This chapter examines the characteristics and importance of accidents and natural hazards as causes of environmental impacts. It summarises their causes and consequences in Europe, identifying different types of damage which can result from different sources.
HAZARDOUS EVENTS: A SEPARATE CAUSE OF IMPACTS |
In the six preceding chapters, different causes of environmental impacts have been discussed. These are the pressures which come about through the routine performance of human activities, particularly in the different economic sectors (see Chapters 19 to 26). However, these activities can also exert pressure on the environment through the consequences of accidents. In this case the medium by which the environment is impacted is less important as a distinguishing factor determining the scope for potential impacts than the nature of the accident itself. The examples in Boxes 18B, 18C and 18D illustrate this well. Generally, it is important to consider accidents separately from other causes of impacts because of two distinguishing characteristics, discussed below: the uncertainty in magnitude, nature and timing, and the non-continuous character of the events; and the impact mechanisms and types of damage which result. Similar characteristics distinguish naturally occurring hazardous events as a cause of environmental impacts, but there are also important differences, as discussed below.
Uncertainty and duration |
Accidents and natural hazards manifest themselves in largely unpredictable, singular events. Accidents arise when routine operations go wrong, resulting, for example, in the unexpected release of toxic substances. The forces of nature cause hazardous events such as earthquakes and flash floods, mass movements, mud and snow avalanches, cold- and heat-waves, tidal waves, drought, volcanic eruptions, storms and tornados. Sometimes, natural hazardous events have a longer duration than accidents (eg, heatwaves, droughts) and in many cases it is easier to foresee their consequences.
Usually, unlike with accidents, little can be done to prevent or reduce the magnitude of a naturally occurring hazardous event. However, much can be done to reduce potential impacts; landuse and emergency planning are the keys to this. Landuse planning is particularly important for understanding and predicting potential interactions between natural hazards and human activities as a cause of environmental impact (eg, soil erosion from floods). This is a common element in the range of tools available for mitigating the impacts of hazardous events and accidents from all sources (see Chapter 30). In practice, planning for natural hazards relies on a type of quantitative risk assessment. Because it is often uneconomic to protect against the most severe foreseeable event, designs are chosen to plan, for example, for the 10-year or 100-year storm, based on the historical record and the design life of the structure.
In contrast to natural hazards, much can be done to prevent accidents. The first step in accident prevention is good planning, management and control of the routine activities in question. This, together with a thorough implementation of codes of good practice, goes a long way to ensuring that emission levels and other interactions with the surrounding environment are contained within limits considered to be acceptable. These limits can be specified in site licence conditions, in principle, allowing local environmental impacts due to any single source to be anticipated and accounted for (through auditing and monitoring programmes) and, if necessary, mitigated. It also means that the cumulative impact of numerous sources in a region can be estimated for the purpose of strategic planning and policy development; this is becoming increasingly important.
Accidents, however, such as the spilling of toxic chemicals into a river, are neither routine nor planned. This does not mean that they cannot be avoided or mitigated. Estimates of the most probable 'worst cases' can usually be made to assist planning. The cause of any particular accident can be traced back to a combination of operational failures relating to one or more aspects of the technical and management systems which control the activity. However, this uncertainty means that pollutant discharges and other sources of potential impact resulting from major accidents can be neither anticipated easily nor accounted for in the same way as normal sources from routine operations. In this respect, they represent an additional and largely unquantified source of impacts on the environment.
The cumulative effect of minor spills and discharges can be considered differently, since the precise time and location of spills are less important in determining their impacts and potential contribution to long-term environmental damage.
Impact mechanisms and types of damage |
Accidents can result in pollutant discharges and physical effects on the environment (eg, fire and explosions) which would be neither expected nor allowed during the course of normal industrial operations. The basic differences between accidents and routine operations, in terms of their potential pressures on the environment and human populations, relate to the following general parameters: the toxicity of discharges, volume and rate of release, and flammability and explosiveness.
The damage pathways are often very complex, involving direct and indirect effects to more than one environmental medium. The resulting damage can differ from that associated with routine activities in a number of ways. For example, the development of unexpected, uncontrollable conditions in an industrial plant could result in the production of large quantities of toxic compounds. If the emergency facilities fail, this could result in release to the environment of large quantities of toxic gases and/or fire and explosion. Depending on the prevailing weather conditions and the sensitivity of the surrounding environment, a single event such as this could cause considerable short- and long-term damage to natural resources (groundwater, rivers, soils), to terrestrial and aquatic ecosystems and to humans. The Seveso accident in 1976 provides an example of this (see Box 18B).
In the case of a failure of a storage vessel or a rupture of a road tanker container in an accident, the sudden and rapid release may be caused of a large quantity of a substance which in normal circumstances might not be released at all, or only in small quantities and under controlled conditions. This can result in off-site concentrations of a pollutant which exceed the damage threshold level of the surrounding environment and/or cause serious human health effects, including fatalities. In some cases the consequences may be dramatic, for example in the form of fireball, as occurred tragically at Los Alfaques in Spain in 1978 (see Box 18C).
Unlike accidents, natural hazards are an important 'dynamic' of the environmental change process. To try to mitigate these events would indirectly constitute a form of environmental impact which could result in even greater, unforeseen impacts in the future.
Like an industrial accident, the nature and extent of the impact of a natural hazard on human society (number of deaths, structural damage, insurance costs) do not depend exclusively on characteristics of the event itself, eg, a storm path. Other factors are just as significant; for example, proximity to populations, construction of earthquake- and/or flood-resistant buildings and infrastructure, disaster prevention and emergency planning.
Similarly, the potential for environmental impacts resulting from natural hazards is to a large extent linked with human activities. These may imbalance natural systems, such as forest cover or groundwater level, and thereby make a natural disaster more likely. They may also result in the location of polluting activities in areas where natural hazards are likely to occur, and thereby enhance the impact potential of the activities. These linkages between human activities, natural hazards and environmental impact can become very complex and cyclic, the causeeffect relationship sometimes being unclear. Nevertheless, it is an area which is likely to become more important as both the pressure on natural resources and the intensity of polluting human activities increase in future.
SOURCES AND CONSEQUENCES |
The sources of hazards which cause damage are discussed in this section under the following headings:
The distinguishing characteristics of hazards arising from these sources and the important aspects of resulting impacts are outlined below. The order in which they are treated does not imply a ranking of importance, which is not possible given the complexity and variety of causes and effects between different sources of hazards.
Industrial installations |
Accidents at industrial installations can result in a wide range of possible damage routes (see Box18B). This is because of the vast range of toxic, flammable and explosive substances which are now used, produced or processed at high temperatures or pressures in large quantities. These substances may be released accidentally, frequently as a result of, or resulting in, fires and explosions.
By the end of 1991 a total of 121 accidents had been included in the Major Accident Reporting System (MARS) database reported to have occurred in the EU under Council Directive 82/501/EEC. Table 18.1 summarises the consequences of the accidents notified. An analysis of these accidents leads to the identification of the following key points:
Usually, public attention is given to major accidents which result in the most obvious and dramatic impacts. It was the major accident at Seveso (Italy, 1976) which stimulated action by the European Community to improve plant safety and minimise the likelihood of similar events in the future. Similarly, well-publicised accidents at Flixborough (UK, 1974), Bhopal (India, 1984) and elsewhere were instrumental in raising public awareness of, and concern about, the reality of industrial accidents.
However, relatively frequent minor accidents can also contribute to environmental damage in a different, but potentially significant, way. This is because minor spillages of liquid chemicals can accumulate to considerable amounts in some areas without being reported, resulting in potentially serious contamination of soils and groundwater. It is likely that this represents a significant source of uncertainty in regional and national inventories of total pollutant loadings to soils and the aquatic environment. The growing requirement for monitoring and reporting of such spills should ensure that current levels and future trends can be estimated with more confidence. (This is discussed further below when marine transport and offshore installations are considered).
Inland transport and distribution |
Box 18C provides examples of transport and distribution accidents which illustrate their considerable potential for impacts with regard to flammability, toxicity and persistence in the environment.
The transport of hazardous chemicals by road and rail (and to some extent by barge), is a major potential cause of environmental and human health damage whose importance is growing as both the amount of traffic and the quantities of chemicals requiring transportation increase. Releases of toxic, flammable and explosive substances can occur following collisions and accidents resulting from mechanical and operational failures.
The possible accident and release scenarios associated with the transportation of one substance by road, or even several substances by rail, are more limited compared with industrial installations, where process complexity and bulk storage mean that the range of possible events and releases can be considerable. The volumes transported are relatively small compared with site storage and marine transport (from about 20 m3 for road tankers, 50 to 100 m3 for rail tankers and several thousand cubic metres for barges).
However, there are many more possible impact scenarios resulting from transport accidents, since the receiving environment and the surrounding population can vary considerably according to the chosen route of the vehicle and the time of the accident. This means that the potential for limitation of damage following an accident is significantly less than for fixed installations, where there is usually an emergency response plan to take account of the likely impacts on the surrounding environment and population. This is the most important factor which distinguishes inland transport accidents from others and necessitates special consideration for the purpose of risk management.
Even buried pipelines can, if not maintained properly, be the cause of catastrophic damage and loss of life, as illustrated by the 1989 disaster in Siberia (see Box 18C). However, the potential for environmental damage in such cases is low, except where liquid fuel is being piped close to a sensitive waterbody.
Marine transport and offshore installations |
Nearly 85 per cent of accidents at sea involve tankers (Table 18.2), whereas blowouts and pipeline incidents each account for less than 5 per cent. Clearly, these less frequent events can be serious, such as the Piper Alpha explosion and Ixtoc I blowout (see Box 18D); however, the potential environmental damage associated with tanker accidents is greatest, not only because of their frequency but also because of their tendency to take place near coastlines.
Figure 18.1 shows the worldwide trend in oil spills resulting from accidents involving tankers, combination carriers and barges between 1974 and 1989. Between 1975 and 1985 there were 74 reported spills of between 10 000 and 100 000 barrels of oil, but only 16 spills in the range 100 000 to 200 000 barrels and 24 spills of more than 200 000 barrels (Cooper, 1990). Both the number of oil spills and the quantity of oil spilled declined during this period. In addition, it appears that a growing percentage of the reported oil spilled has been due to a relatively small number of large spills. However, most unreported spills are likely to be at the smaller end of this range. It is likely, therefore, that the proportion of the total volume spilled coming from relatively small-scale incidents is higher than the official statistics would suggest. Nevertheless, the carrying capacity of the marine environment is less likely to be exceeded following individual small spills and so they have not been considered as a major cause of concern.
Map 18.1 shows the global distribution of large tanker spills since 1974. Not surprisingly they are concentrated in the areas of heaviest shipping traffic, which inevitably is found in coastal areas. Hence the high potential for ecological damage from this source.
As with industrial installations, it is the short-term impacts of large, dramatic marine oil spills which gain the public's attention. However, the environmental damage caused by accidents at sea can vary considerably, depending primarily on where the spill occurs especially whether or not the pollutant is released in coastal waters which are often very sensitive ecologically on the nature of prevailing weather conditions and on the type of oil spilled. Even small spills can cause significant damage under adverse conditions in a sensitive area.
For example, the world's biggest oil spill (550 000 tonnes over 9 months), from the Ixtoc I oil well in the Gulf of Mexico in 1979, apparently did remarkably little damage, the source being well away from any coasts (see Box 18D). In contrast, the Amoco Cadiz accident in 1978 (also Box 18D) caused considerably more ecological damage along the French coast: although the amount of oil spilled was less than half of that discharged from the Ixtoc blowout (220 000 tonnes), it was discharged in only a few days.
Prevailing weather conditions determine not only the overall direction in which an oil slick will move, but also how quickly it will break up. For example, the short-term impacts resulting from the Braer oil spill in 1993 (see Box 18D) were not as severe as had been expected from such a large spill in ecologically very sensitive coastal waters. This was because of the dispersive action of hurricane-force winds.
There are other aspects of marine spills which could also be significant in the longer term: the impacts of smaller spills (eg, on bottom fauna, flora and sediments); and the largely unknown impacts of spilled toxic chemicals, including heavy metals and chlorinated hydrocarbons.
The cumulative impacts of the many smaller accidents and spills which take place, both reported and unreported, are potentially significant in the longer term, depending on the persistence of the substance. However, very little long-term monitoring of impacts has occurred, even following major spills. Much more extensive monitoring and research will be required before the potential chronic effects of accumulated toxic spills will be known.
Nuclear installations and transport of radioactive material |
In Europe, all sections of the civil nuclear industry are operational, from the production and use of radioisotopes to the production of electricity, involving all types of nuclear industrial facilities, such as: uranium enrichment plants, reactors and electronuclear power plants, and spent fuel reprocessing plants (Table 18.3). The nuclear power industry is discussed in Chapter 19, where the capacities and locations of nuclear power plants in Europe are presented (Map 19.2).
Nuclear accidents can potentially occur at a range of installations, including all those belonging to the nuclear industry as well as at military and medical facilities and research institutions. The transport of radioactive materials (eg, nuclear fuels, radioisotope sources and waste products) is also a potential source of accidents.
Accidents in such contexts are distinguished from all others by their unique potential to release radionuclides into the environment. The subsequent radioactive contamination can be extremely damaging (see Chapter 16) and some radionuclides are very persistent in the environment. The Chernobyl accident in 1986 (see below) demonstrated how nuclear accidents can have major impacts on the environment and human health.
The transport of radioactive materials during the last 30 years has not resulted in accidents with significant radioactive releases or other consequences for the environment (CEC, in press (a)). Some 2 million shipments are made yearly within the European Union, 90 per cent of which are medical isotopes and less than 5 per cent comprise nuclear fuel cycle material, including radioactive waste. Chemical hazards are also taken into account for shipments of uranium hexafluoride (a chemical compound used in industrial processes to enrich uranium). A hazard evaluation undertaken by the International Atomic Energy Agency (IAEA), following the sinking off the Belgian coast in 1984 of the freighter Mont-Louis, which was carrying this compound, concluded that there had been no significant radioactive or chemical consequences to the public or the environment.
Due to accumulated experience and technological progress, particularly in the field of radioactive waste management, public exposure to radiation and controlled radioactive releases to the environment, under normal conditions of plant operation, have been continuously decreasing during the last decade and kept below regulatory levels, at least in Western European countries. The environmental impact appears reasonably controlled and radiological exposure of the public well below the authorised limits in these countries (CEC, in press (b); Mayall et al, in press).
The situation is different in the countries of the former USSR, and especially in the Russian Federation. Here, waste disposal practices have been limited in many cases to direct releases of radioactive liquids to the environment (rivers, lakes, seas, soil see Chapters 5, 6 and 7), to ground storage of untreated solid waste, and to the sea dumping of waste and even marine nuclear reactors in violation of the Convention on the Prevention of Marine Pollution by dumping of waste and other matter (usually known as the 'London Convention'). This convention was signed in 1972, taking effect in the former USSR in January 1976. Most of the high-level waste was dumped by the former USSR prior to that date; low-level waste, however, continues to be dumped in shallow waters. Information about dumping nuclear reactors by the former USSR has been released by the Russian Federation Governmental Commission on matters related to radioactive disposal at sea (Table 18.4) (IMO, 1993; Yablokov et al, 1993). A comprehensive evaluation of the potential impact on the environment of these practices is not available and remains to be made, but initial international monitoring surveys indicate there is no immediate risk to health. See also Chapter 6.
The International Scale for Nuclear Events of Safety Significance (INES), adopted on a trial basis in 1989 under the aegis of the International Atomic Energy Agency and now formalised (IAEA, 1992), grades the impact of abnormal events which occur during the operation of nuclear installations on the environment (Table 18.5) as follows:
The INES system, having been designed to characterise abnormal events in the nuclear industry, was not intended initially for events resulting from activities involving the use of radionuclides outside this industry. Available information shows that most events are accidental irradiation of personnel due to the mishandling of radioactive sources in industry and medicine. However, uncontrolled release or disposal of spent sources caused some pollution (a severe accident of this type was reported in 1987, at Goiána, Brazil).
Available information concerning the last decade (Table 18.6) shows that nearly all nuclear events have been 'anomalies', and a few of them 'incidents'. The most important 'incidents' in Western Europe are reported in Table 18.7 in relation to the type of facility and the probable cause of the incident. The most significant was probably the Sellafield incident (UK, 1983) where a total of 5.9 x 1013 becquerels, mostly of ruthenium-106, was released to the Irish Sea, leading to temporary advice being given not to access the beaches in the vicinity unnecessarily, as a precautionary measure. 'Accidents', that is, nuclear events leading to environmental contamination, have been exceptional and none have occurred since 1980 in Western Europe (Windscale pile, UK, 1957; Windscale reprocessing plant, UK, 1973; and Saint-Laurent power plant, France, 1980). A reservation should be made, however, as far as the safety record of nuclear plants or ships of the former USSR is concerned: because many of them have a military character, at least partially, available information has been limited. Two extremely severe accidents have been recorded (Table 18.8) (IAEA, 1991; SCOPE, 1993): the Kyshtym accident (Southern Urals, former USSR, 1957) in a military processing plant and the Chernobyl accident at an electronuclear power plant (level 7 of INES scale, Ukraine, former USSR, 1986). According to the more open policy of the Russian Federation, information about 'anomalies' and 'incidents' (levels 1 to 3 of INES scale) is also released, in particular through the INES channels (Chernobyl nuclear power plant, 1982; St Petersburg nuclear power plant, 1991 and 1992; Tomsk military reprocessing plant, 1993).
The few nuclear accidents listed above are individual in cause and consequence and do not easily allow general conclusions to be drawn about the effects of important accidental releases of radioactivity into the environment. These are discussed under five headings below and related to the particular experience of the Chernobyl and Kyshtym accidents. The Chernobyl case is particularly noteworthy here, and a description of the accident and its consequences is detailed in Box 18E.
During an abnormal event, the radionuclides released depend on the nature of the accident and of the type of nuclear plant; these determine the main sources of exposure to radiation and changes with time. In the Chernobyl case, after the decay of short-lived radionuclides, radioiodine was predominant for some weeks after the accident, present in milk and fresh vegetables. Since 1987, the radiobiological significance of contamination has been defined mainly by caesium-137 and -134, and, more locally, by strontium and plutonium isotopes.
The distribution of the radioactive fall-out depends strongly on the conditions of radioactive release and on the meteorological conditions at the time of the accident. The continuous release of radioactivity during the first ten days of the Chernobyl accident, with changing wind directions and the intermittent presence of rain along the path of the airborne activity, explains the broad spread and somewhat patchy distribution of the resulting radioactive deposition (see Maps in Box 18E). Biogeochemical processes such as radionuclide migration through soil, plant-root uptake and leaching processes subsequently modify the distribution of deposited material.
Radiation damage to vegetation
For both the Chernobyl and Kyshtym accidents, various degrees of radiation damage to vegetation were detected; during the first and second years in particular after the incidents, trees and herbaceous vegetation were affected, and especially the tree species most sensitive to radiation such as conifers (Pinus spp). The so-called 'Red Forest', to the north of the Chernobyl plant, died, was cut down and buried where it stood. Other forests in the vicinity of the plant continue to be a significant source of contamination for the biosphere, although wild animals are prospering in the zone. Since 1987, there has been evidence that forests have stopped showing the effects of radiation exposure and contamination in terms of mutations.
Radiation damage to fauna appears to have been limited to the first years after both accidents. In the Kyshtym case, diminished reproduction was apparent in the vulnerable herbivorous fish species a few years after doses to eggs exceeded lethal levels. By 1960 no ecological effects were observable; effects on plankton, invertebrates or aquatic plants have not been detected. After the Chernobyl accident, most animals, including cattle and horses, that were not removed from the 30 km exclusion zone died; surviving cattle were all hypothyroidic and of stunted growth; the second cattle generation seems to be normal. There were no clinical signs of health effects recorded in cattle from outside the exclusion zone. A fact-finding mission, led by the Food and Agriculture Organization of the United Nations (FAO), investigated evidence from reports that had been widely published in newspapers around the world concerning birth anomalies in domestic and wild animals in the affected areas. The team concluded that none of the abnormalities reported were different from others observed elsewhere in the world.
The consequences of both accidents were mitigated, first, through evacuation of the population at risk, then through countermeasures related to food production and monitoring of agricultural products, and finally by reorganisation and modification of agriculture and forestry techniques. When applied to large areas, available techniques for land remediation are unsatisfactory and need improving in terms of both cost and efficiency.
Besides the more obvious questions of reviewing the major design and operation changes to the RBMK-type reactor and the training of operators and fire brigades, the Chernobyl accident certainly highlighted the need for a better emergency preparedness nationally as well as internationally in case of a large nuclear accident (see Chapter 30).
In the first instance it became clear that there was an urgent need for sufficient coverage of radioactivity monitoring stations and the necessity for rapid automatic transmission and processing of the collected data. EU countries have already updated or are in the process of updating their national early detection systems using gamma-ray detectors, and their continuous monitoring systems by means of on-line aerosol detectors. However, differences in objectives of these systems, reflected in the detection limits and rapidity of response of the systems as well as the spatial density of the network, still exist between countries. Also more attention is being given to the role of mobile monitoring equipment, in order to assess the radiological situation adequately, to examine the need for countermeasures and to provide reliable information to the public (Janssens et al, 1993).
Natural hazards |
The risks associated with natural disasters worldwide, in particular in developing countries, have increased over recent decades. This has been partly due to demographic changes which have increased population density in vulnerable areas such as coastlines and river basins. This has been coupled with a general increase in polluting human activities (mainly industrial), which have not been exclusive to areas with low natural hazard potential. Although these trends have been most acute in the developing world, certain parts of Europe (particularly in the south and east) have been undergoing similar changes. This interaction between human activities and natural hazards has increased the potential for natural hazards to contribute to environmental impacts. This is an important issue which is highlighted in this section and provides a further reason for landuse planning to play a vital role in mitigating or even avoiding such impacts.
Natural hazards are grouped below into three main sources of impact for the purpose of this review:
In Europe, as worldwide, storms and floods are the most common natural disaster and also, in terms of economic and insured losses, the most costly. The threat of coastal and estuary flooding as a result of storm surges has particularly been recognised and planned against since the North Sea floods of 1953. These resulted in serious human and infrastructural impacts to low-lying areas in the UK and The Netherlands in particular, and stimulated the development of coastal defences and more sophisticated preventative measures such as The Netherlands delta plan and the Thames barrage. Coastal defence works need a regional and transboundry approach so that impact is not just transferred elsewhere (see also Chapter 35).
Although some areas are more vulnerable than others, the transboundary nature of inland flood potential can be appreciated by considering that the river Danube runs through nine different countries. The catastrophic flooding in southern France and Switzerland in 1992 and 1993, caused by continuous thunderstorms, provides an example of the susceptibility of regional populations to inland flooding. In addition to the local damage caused by flooding, there can be unforeseen events such as landslips, mudflows or river surges caused by dam failure. This happened in northeastern Romania in 1992 when the Tazlu dam gave way, killing 107 people and resulting in economic losses of $50 million.
Environmental impacts typically include soil erosion, sedimentation and tree levelling. However, when such events interact with the pollution resulting from human activities there is the potential for more catastrophic environmental damage. This kind of potential interaction between pollution from human activities and natural hazards introduces a new dimension to international risk management and emergency planning which urgently needs to be addressed.
Heatwaves periodically have serious effects in Europe, including crop damage, reduced water supplies, drying up of rivers and lakes (with associated ecological impacts), human health effects and even deaths. Structural damage in urban areas has also been observed. As with floods, however, the most important potential for environmental impacts is in conjunction with human activities:
In addition to direct effects on vegetation, droughts can lead to soil erosion, lowering of water tables, excessive demand on surface waters and ecological effects resulting from saline intrusion. Though a climatological drought (lack of precipitation) can be enhanced by a heatwave, the most serious consequences are often a result of a long-term decrease in precipitation in conjunction with excessive demand on water resources and poor distribution and planning. Intensive farming techniques and inappropriate forestry practices (eg, eucalyptus plantations in Portugal see Chapter 23) can exacerbate a drought situation. Again, this indicates the important role to be played by environmentally aware landuse planning in preventing environmental disasters.
Direct impacts of earthquakes on the environment are very small, the most serious effects on society usually being due to infrastructural damage and consequent fires, disease and lack of shelter. Clearly, however, there is the potential for earthquakes and volcanoes to cause the release of pollutants and to have serious effects (eg, by causing damage to industrial facilities). This is another aspect of risk management which needs consideration as pressure increases for industrial expansion in areas subject to seismic activity. In fact, design codes for industrial installations and nuclear plants against seismic effects are well established in earthquake-prone areas, and even in Northern Europe, including for offshore installations.
The main environmental consequence of volcanic eruptions relates to air quality. Apart from the considerable local impacts of particulate emissions, there is now evidence that emissions into the stratosphere can have other impacts, particularly on climate.
Over the past century, serious earthquakes have occurred in Italy, Greece, Turkey, Yugoslavia, Armenia and Romania, resulting in catastrophic damage and loss of life. However, there are few active fault lines in Europe and such events are infrequent compared with other regions of the world. Volcanic activity is even less frequent.
HAZARDOUS EVENTS AS A CAUSE OF DAMAGE |
The identification of trends in accidents over the years has to be undertaken with some caution, since only major accidents are reported and there are different reporting limits for different chemicals. The reporting of accidents has improved over the past 20 years, but inconsistencies still occur (Box 18A). Some geographical areas receive less attention (eg, Eastern Europe) and certain types of accidents are often not reported at all.
Coincidentally there has been an apparent increase in impacts from natural hazards in recent decades (Swiss Re, 1993). Whether this is due to an increase in the frequency or intensity of events, an increased vulnerability to them, or perhaps a combination of these, is not totally clear. However, as mentioned above, it is in any case increasingly relevant to consider the importance of natural hazardous events, in conjunction with human activities, as a cause of environmental impacts.
Short- and long-term impacts |
Accidents have a unique potential to cause massive short-term impacts and sometimes irreparable damage to local populations and ecosystems. This results from the acute effects of highly toxic chemicals or the impacts of explosions or large-volume releases of pollutants over a short length of time. Natural hazards have the potential to precipitate or enhance the effects of such events. In such cases, the risks to the surrounding environment presented by the hazardous activity will be significant, if not dominant, compared with contributions from more chronic sources of pollution.
In general terms, accidents are likely to cause greatest ecological damage through aquatic impacts, whereas atmospheric emissions are the greater cause of human health effects and fatalities. It is also likely that transport accidents present the greatest potential for ecological damage, taking account of oil tanker spills.
It is not realistic, therefore, to categorise accidents according to their ecological or human health impacts. Increasingly, it may be more useful for impacts to be expressed in an integrated way, accounting for both types of impact, as well as potential risks to natural resources such as groundwater (see Chapter 30).
Serious environmental impacts of single accidents are generally perceived in terms of local, immediate and short-term effects. To appreciate better the long-term environmental effects of accidents, extensive post-accident monitoring is required. Long-term monitoring is still, however, very rarely undertaken following an accident, so the long-term effects of accidents on the environment are still very poorly understood. The investigation of long-term impacts of the Basle accident (Box 18B) has revealed less damage than originally feared, whereas the river Roding accident in the UK (Box 18C) provides an indication of the potential long-term nature of resulting damage. The long-term monitoring of the Braer oil-spill impacts (Box 18D) will also provide useful information in this respect.
Relationship with other causes of impacts |
The direct effects of a single accident on the surrounding population and environment can be very serious and warrant special consideration, as discussed above. Nevertheless, overall, the general health of the population and the quality of the environment are more affected by chronic, ongoing pollution than by the acute effects of singular events. To a large extent, therefore, the significance of the environmental and human health impact of accidents needs to be seen in the context of environmental stresses (pollution loadings, etc) from routine sources (as discussed in Chapters 12 to 17).
Only major accidents are routinely reported and smaller accidents often receive no attention and do not become part of accident statistics. There is concern, however, that the discharges from these smaller accidents can accumulate and contribute significantly to overall pollutant loads to soils and waterbodies. This source of impact is currently largely unquantified in Europe because of the lack of past reporting. As an indication, however, in North America the total amount of polychlorinated biphenyls (PCBs) released in spills between 1981 and 1985 has been estimated to be nearly twice the amount of PCBs routinely discharged into the Great Lakes (Peakall, 1989).
In addition, growing evidence of accumulated soil and groundwater contamination is resulting from site investigations, indicating that this general problem could be very serious in some areas of Europe with a long history of industrial activity (see also Chapter 15).
There is a similar concern in relation to marine oil spills. They attract a large amount of public attention and can have serious short-term impacts on the environment. The importance of tanker spills derives from their relatively rapid release of large volumes of oil, which can easily overwhelm the local receiving waters in coastal environments. However, when the possible longer-term effects of cumulative discharges are considered, other sources become important.
Petroleum hydrocarbons reach the sea by many other routes and tanker accidents are not of major significance alongside other inputs, such as operational discharge of oil during tanker operations, fuel oil discharges, and municipal and industrial wastes. An indication of the contributory sources is given in Table 18.9. It can be seen that reported tanker accidents are likely to account for about 25 to 30 per cent of the total input from transportation and only about 10 to 15 per cent of the total input due to human activities.