Document vBrMge4eB89DnLJbvNmjBzD0E

Monsanto TO S. TUROVER, BRUSSELS JUNE 27.. 1974 PCB'a ST/nd IN TURN -r#Vkupt-RUADON PJA MARSH, BRUSSELS S TUROVER, BRUSSELS M. a /VAta tfrf. *(<ij'? f'vr Attached is a paper by Martin Holdgate - whom we hnow - recently presented at a function of the Chemical Society in the UK. i It is a perceptive and interesting paper, and it includes a rational discussion of PCB's in the environment. Papers of this hind can be very important in reducing the cries of the environmentalists to a somber examination of the facts. Please return to ST. Thanhs. '7. TUROVER t HONS 028890 71TB MOJOGICiUj liKFliCTo OF OlUiMICAIi oUBUTAIICSS Dr ft W Holdgatc, Central Unit on Environmental Pollution, Department ol the Environment* . Footnote. The views. expressed in this rmper are those of the author and not necessarily those of the Department of the Environment. Pollution may ho defined as "the introduction by man into the environment , of substances (or energy) liable to cause hazards to human health, harm to living resources or ecological systems, damage to amenity or interference with legitimate uses of tho environment". This definition brings out tho basic fact that in responding to pollution we are concerned with actual or potential adverse effects - damage to j * our own physiology, to the living resources on which we depend directly, or to tho wider ecological systems of land and sea that ploy a vital part in the renewal of atmospheric oxygen, the elimination of many of our wastes,'and the recycling of vital nutrients. In this panor I am concerned with the effects of chemicals injected into the biosphere by man (whether injected directly or indirectly via the physical environment), and the nature of our response to them. . i i } i , Even the most apparently stable of living systems exhibits dynamic I j equilibrium. This is affected by physical.and chemical variables at many levels. A pollutant in the environment may affect: (a) an ecosystem ' ' j | f (b) a population of a single species ' (c) a Bingle individual organism (d) an organ or system within thatorganism (o) a biochemical or cellular subsystem HONS 028891 ! I j , j or oovcral of these simultaneously. lit t /<n KC.I1 ic/iu k f ttict-S OF Foki, u7to Commonly, wo consider pollution in tome of it:: effect upon whole individual organisms. It is evident thnt the responses of indivjduels ore in fact the integral of a complex web of subsidiary effects upon biochemical systems, lending to changes in cellular physiology and behaviour which in turn affect the functioning of whole organs. A pollutant may often have a demonstrable effect at biochemical or cellular level which, because of the homeostatic machinery of living creatures, may not be manifest at the level of the whole individual at all. This does not mean that the individual is unaffected by the pollutant: indeed, it means thnt some of the biological capacity of that individual is being used up in the same'way that the discharge of a pollutant into a lake uses some of its dilution ' capacity even though it does not reach the threshold at which ecological change ensues. Similarly, the responses of whole ecolorical systems are the integral of many interdependent individual responses. It is quite common for significant effects on individuals not to be manifested at all at the ecosystem level, where so many organisms of so many different species interact to produce a system that is in dynamic equilibrium and which displays considerable inertia. Those levels of effect are arranged hierarchically. The ecosystem lovel of response is the highest level and a "no responco threshold" may yet be maintained while there is a considerable pollution-induced mortality at the individual lovel, and even at the species level should tho species exterminated from the Ecosystem not be of major .importance in determining tho characteristics of the whole. For example, it has boon established that exposure of lichen species on the trunks of English oaks to mean annual sulphur dioxide concentra- - 2- HONS 028892 tions of 40-180^ig/ro?^ con be correlated with their progressive extermination - und, no doubt, that of tho small insects that feed on them. This hus no effect, so for ns wo know, on the basic ecological stability of oak woods in tho Ilidlands or South-East England, and, while .it clearly leads to a degree 0f impoverishment compared with the natural situation, does not prevent the eobablishment of k^oodlanc! National Nature Reserves which supnort an othorwiso rich and varied wildlife. Similarly, it would be perfectly possible to contemplate a pollutant effect which exterminated some species from a freshwater, or marine environment without affecting either the capacity of those waters to support a balanced and productive ecosystem or creating a system unacceptable to man. i In this situation pollutants can be considered to impose "stress" on the ecological system .just as other forms- of human interforer.ee do. It seems probable that the very first effect is to increase the specioB diversity of the system, but thereafter rising levels of pollution are paralleled by reduction in diversity and also by a tendency to change from systems dominated by large, long-lived forms to those dominated by smaller species with shorter life cycles - ns when woodland gives way to grasslands. In more technical language, the shift is toward systems in which the annual production is larger in proportion to the standing crop. This is not the place to g,o into dotai.ls, but v/e do now know a good deal about how ecological systems ronpond to stress and this is valuable in predicting what new levels of pollution may do to patterns of vegetation and fauna. 5- - ^/Ug/m^ is microgram per cubic metre HONS 028893 At the population level, if one in concerned simply to have "no rounonse" in terms of population size, enhanced mortality io acceptable so long as thio io not on no great n scale that it lends to population decline. That io, it io permissible in these terms to substitute pollution for other forms of mortality that would otherwise remove the surplus of offspring produced in most populations of living creatures. If the annual production of young seabirds, for example, is three times that required for recruitment into a stable brooding population and the norm is for the surplus two-thirds to die, in population terms it is immaterial whether this surplus io removed by competition for food, predation or c'hemicnl pollution, so long as recruitment is sustained. The size of the population would be equally unaffected if the mortality among breeding adults wore increased by pollution, so long as enough young survived to maintain recruitment at the higher rate which would then become necessary. Indeed it seems very probable that during the early 1960's the heron population in England was in just this position in relation to certain organochlorine pesticides. We know that some adult herons were lcthally poisoned and there is considerable evidence to suggest that sub-lethal rosidueo affected egg-shell thickness and chick survival, resulting in a reduced output of young. Neither the adult mortality, nor the decrease in over-all breeding success, however, appear to have reached a level where they affected more than the nnnual surplus present in the population and so the total heron population of England and Vnlos of '1,500 pairs remained unchanged. - 4 HONS 028894 Annin, u demand for "no response" at; the individual level permits organ, cellular, or biochemical changes, so long ns mortality or o oerioua retardation of growth or distortion of behaviour does not onnuo. The influence of factorieo omitting fluoride on cattle prazing in their vicinity has been regulated on such a basis: a "no effect" standard at the phy3iolop;ical level has not been demanded, but the exposure has been restricted in such a way that unacceptable effects are avoided. Rather similarly, some pasture grasses nnd crop plants in industrial areas of Britain may have their growth rates affected by atmospheric pollution, including pollution by SOj, but this is regarded ns acceptable so long as yields are maintained above a contain threshold, determined by economics: Even in man one sees this situatibn, although the threshold is usually set much morn stringently on heal Mi grounds: eg, in our acceptance of blood lead levels which affect the activity of the enzyme delta-aminolnevulinic acid dehydratase, so long as those are not permitted to rise above around 56-A-Oyug/IOO ml of blood, which is commonly taken as the point beyond which we become socially concerned. Finally, if wo determine that we shall have a "no response" situation at the biochemical level, we are admitting of no detectable effect whatsoever and nro faced with.the most stringent of all demands for pollution control. Indeed, with an impossible situation, since some substances we release as pollutants aro present naturally in our environment at levels which have a biochemical effect. MONS 028895 In social terms, we tolerate different levels of effect according to the nature of the target nnd its immediacy to the human situation. For example, it is commonly agreed that we should not accept significant effects nt the organ level in man. We are indeed wary about tho cumulative effects of lifelong exposure to substances which may only have minor demonstrable effects on human biochemistry, fearing that they may in some way progressively erode the body's homeostatic machinery and shorten life. Ue recoct significant effects at the individual level. - illness or impaired growth - in cattle, sheep, other farm stock and domestic pets. Vo reject significant ecosystem 4 effects in merino and freshwater ecosystem.", and in forestland wild vogotntion, with their invertebrate and bncterinl components. Sometimes, of course, the standnrd wo net at one level affects organisms for which we would otherwise only be seeking lesser decrees of protection: standards set for mercury in fish as human food for tut example, may load to curbs on discharges of sheet metal to the sea which from the point of view of protecting marine ecosystems would not be necessary. It does not follow that our judgement in these matters io always wise (although I believe that it is defensible) but it does follow that wo should be aware of the logic' of our actions. EXPOGUHE AND EFFECT The effect on a target depends upon three groups of variables: (a) the nature of the pollutant, (b) the biological state of the target with which it is interacting, including the individual and temporal variation which is exhibited by individuals, organs and biochemical systems, (c) the concentration of the pollutant and the time of exposure (not usually, incidentally, capable of being summarised by a oimplo arithmetical multiplication. Short term exposures to very high concentrations need not always be the equivalent of exposures to half that concentration for twice the time or one-tenth the concentration for ten times as long. Ozone for oxamplo, con affect , HONS 028896 I --------BU1IH1U.9U lumreu..nr-nour-ty exposures to around^o-^r^pprin^r------twice the time ut half the level may have much los3 effect). In addition, it is important to know the site of entry of the pollutant (eg skin, lung, rut) nnd the site of notion (nervoun system, blood, kidney, liver etc). It is worth emphasising that exposure has to be measured at the t.qrrct. The pathway from the source of pollution to the target is all important in determining exposure levels, ouch a pathway may be represented ns in Figure 1. It is evident that n whole series of physical nnd chemical properties nnd interactions influence this movement, and parameters such as diffusion coefficients, absorption properties in and from soil, solubility in water or other liquids, retes of break down by ultraviolet radiation nnd reactivity with other components of air, water or soil can have a mo^or influence. This is well exemplified by the pathway of sulphur dioxide in nir (Figure 2) washing'out in rain as dilute sulphuric acid and/or combinotion with amonin to form an ammonium sulphate haze ("Teossido mist") have nn important influence on the actual nature of target exposure. Similarly, chlorofluoro hydrocarbon compounds emitted to the environment as uorosol propellants apparently consist for a long time u.ndnr groundlevel conditions but are fairly rapidly degraded by ultraviolet radiation in the upper atmosphere: here physical mixing of layers of air will clearly bo an important determinant of persistence. In predicting the scale of a possible pollution problem, therefore, any model we develop must take full account of- the pathways, as well as the nature of the actual interaction of the pollutnnt and the target. It must also enter for individual variations in susceptibility and 7 HONS 028897 pphm pnrts nor hundred million variations with time and circumstance. Somotimns these'variations con be very largo. For example, concentra tions of load in air in Britain may roach 20-25/ug/in'' in the centre of motorways by day and average lO-'l^yufl/m7' over 24 hours. In ordinary busy streets, and around factories, ?A hour averages are around 1-2yug/m^. In the country levels are much lower - below O.l/ig/m^. Human exposure inovitubly varies as people move around. Human intake to the lungs likewise varies according to the volume of air wo breathe in the day - and while the average for an adult man is around 15 this can bo doubled by activity or halved by rest. Not all the lead particles passing the nose or mouth reach, or stay in the lungs: various calculations give retentions of 10-60?o of the potential intake. Only a proportion of the lead retained is absorbed - maybe 50?'' on average, but with much individual variation. If you sum the cumulative effect of all these variables, you can readily see how there could be a thousandfold variation in human lead absorption from the air - and the uncertainties in many figures cast doubts on the usefulness of such a broad-brush calculation at all. Generally speaking, the effect of exposure to a pollutant is related to concentration, although the curve is unlikely to be linear. Moreover, the response to increasing concentration is frequently hierarchical in nature. That is, at the lowest concentrations the-e is a biochemical effect. Vith increasing concentration this becomes manifest in whole cell or whole organ changes, then in variations in individual behaviour. At higher concentrations still, individual mortality may ensue while greater exposure leads on to whole population or whole ecosystem changes. -8- MONS 028698 Vc havo partial documentation of many of those curves. Often the information rcoultG from laboratory tests, under conditions remote .Cron those in the field, of single pollutants against single target npocieo. Thin may bo reasonable enough for exposures to pollutants with a specific action, like the effects of radiation on r.onotic systems /figure-but how valid is it ns an indientor of wholepopulation or whole-organism responses to chemical factors? Often the laboratory toots estimate doses that kill 50"'> of the exposed organisms (LDJO) in 24, 48 or 72 hours or over a longer period of days. Often, the dose concentrations used in such tests are relatively high - sometimes this is necessary to demonstrate a response in a convenient time. The test species used are often selected for convenience in the laboratory and basic (and sometimes sweeping) assumptions are made about the similarity of response other organisms may be expected to show. But what of the situation in nature, when wc are dealing with mobile populations, forming part of a much more complex system , and able to move away from areas of high pollution. There can be no confidence in their extrapolation to the real world. Often,too, ecologically nipnificant effects can be sub-lethal and will not show up at all in I1B5O tests. For instance, seaweed growth rates can be related to dogreoa of marine pollution f.figure 4) /fi-.wrowe,--d(i--jf, with conse quences for herbivorous marine animals; and fish physiology can be adversoly affected by DDT levels below the directly lethal dose, . making fish moro likely to succumb to cold or to be unsuccessful on migration ^Figure 0)' '("Anderson, <19--/i. HONS 028899 A pood example of a complex and imperfect framework of knowlcdpe is provided by sulphur dioxide in air - ono of the. commonest and most- studied of atmospheric contominante. As figure >/ implies, quite a lot is known about the exposures at whioh various kind;; of plant first show injury and then serious damage. Likewise, tho onset of symptoms in tho moot sensitive people (bronchi.tics) is predictable. But in both cases allowance must bo made for a very wido range of individual variation (in man there is probably a thousandfold range in sensitivity in an nverago populati on); furthermore, there is a groat deni of variation in response according to tho duration of the . exposure, and at least in man, the levels of smoke accompanying the BOp' exposure arc critical. Thus, the "threshold" level f.or SOp, averaged over ?A hours, is 500^/ig/m3 when accompanied by g^O/Hg/m^ omoke /pjp;urc ^ whereas laboratory studies have failed to find significant impairment of human respiratory function by BOg alone at concentrations below 2500yug/m^ for comparable periods In this case wc do have enough knowledge of dose/response relationship to conclude that in order to protect vulnerable people we should seek to keep daily average sulphur dioxide levels in air below DOOyug/ra-' and smoko below and these figures have been adopted ug short-term objectives by a WHO Working Party. If we consider that tho manifest sensitivity of lichens indicates potential biochemical disturbance which, while we cannot prove its parallel existence in man ought in common prudence to be avoided, we would need to toko an annual mean of around AOyjg/m'' as our environmental quality goal - and that peuks never greatly exceeded this figure. Although wo have little information on other species, this would almost certainly also prevent any crop lossoa and protect most forms of life while it would not eliminate the beneficial action of air-borne 30p in correcting sulphur deficiency in some soils. The recently published national 10 - MQNS 028900 survey of smoko and sulphur dioxide /iiHiO-loy?/ indicates that 500/ur/di^ is only exceeded in the south of England, excluding London, for a very few days in the year, whoreus in London end in the midland and northern towns it is frequently exceeded. Jiut in many rural areas tho lower "target" of an annual moan of 'JO^ig/m^ is exceeded, no that it is not surprising that tho British Lic.henol ogical Society has recorded considerable impoverishment of tho lichen flora in the whole central midland zone of England /Figure1 6^. The question is whether this is paralleled by any significant agricultural losses (one report placed these at A0 million- j-'-r annum in England, but with an enormous possible'margin of,error) and sufficiently serious to justify tho major expenditure that would be required,to reverse it (especially in the current energy situation). Only raroly do we have even this degree of detailed information about exposure-effect relationships. More commonly all that we hr vo it; a brosd, descriptive correlation, between pollvition levels, generally ftu. li</Ur. is n (.cttt-KiU-wu assessed, and biological response: an^oxample for fresh water,Ao-givon in I'liicrrcr-'^/ There is clearly a need for more research to determine rigorous "criteria" on which our social judgement of tho need for more'(or less) intensive effort to combat pollution must depend. Such work needs to take into account the biochemical means by which the whole-organism responses are mediated. We need a better understanding of individual variations in response, and how variables such us age, nutritional stato or reproductive condition of tho individual internet with environmental chemical factors in determining them. THE IKTJSHACTION OF POLLUTANT.'! AND OTHER FACTORS HONS 028901 This loads to another important generalisation: pollutants rarely operate in isolation. I would liko to give a case history that underlines this rather well and illustrates the true complexity of tho kind of situation that confronts us. Between August and November 1969 about IP,000 seabirds died in the Irish Sea. They wore n.lmont nil of ono npecion (llria anlpo, the Ouilleraot); they wore almost all adults, and nearly all of them came ashore after fioptember pales in on emaciated condition. Investigation --"J showed, however, that the pales were not the primary cause, for while the peak in the number of strandings coincided with the storms, some birds hod begun to leave the water in a distressed condition before the pales began and While pales of equal severity had affected tho whole western seaboard of Britain, the mortality was conccntratod in the' Irish Sea north of a line from Holyhead to Dublin and south of a lino from Donegal to the Hull of Kintyre ypigure-^jf. Histological examination showed that many of tho birds had lesions in the kidney and liver and changes in the heart and pericardium which paralleled experimental effects obtained by exposing birds to large concentrations of polychlorinated biphenyls (PCBs). Chemical analysis subsequently showed high levels of PCBs in liver and kidney, and to a lesser extent in brain ^-ablfr--4^. It would bo tempting, therefore, to frame the hypothesis that those birds died of PCB poisoning. This, too, would be an oversimplification, since healthy birds shot off the west const of Scotland contained whole-body loadsof PCBs comparable with those in tho victims of the disaster The difference was that in tho healthy birds tho PCBs were distributed in the body fat and the levels in liver and kidney were low. The conclusion of the study was that we wore dealing with a multi-vnriato situation. The moot plausible hypothesis was that something, - 12 - HONS 028902 t possibly climatic change, causod a reduction in the available food supply of these birds in midsummer at a time when their renerveo wore fairly low after the breeding season and they were about to go into the moult, which imposes a further stress. The oceanographers were unable to detect any change in marine life, but since these birds feed only in the very top layer of the water, a long clear spell with bright sun might have lod their food organisms to descend slightly deepor than normal, thereby shutting off the food supply but not creating changes detectable with the marine biologist's tow net. Be that as it may, the initiating enuse of the mortality was .very possibly an interruption of feeding. This would, of course, have led to the mobilisation of body fat, which would have brought the PCBs stored there into the blood stream and on their way to liver and kidneys. This in turn might well have had minor behavioural effects at the whole-organism level. It might have made the birds a little less efficient at feeding, thus exacerbating the situation, and more pron to exhaustion by storm, especially since their food reserves were already low; any further stress could only load to the increasing flushing of PCBs into the. blood. There would then be the recipe for a localised disaster in the area where the initial imbalance between food-intake and food requirement had occurred, and the whole disaster would be attributable not directly to PCB poisoning, but to the impact of this pollutant within the system, tipning the scale between survival and doath whon tho environment imposed external stress. I believe that this is likely to bo a model commonly valid in tho pollution area and that many pollutants must be looked on as operating in this way, changing the probabilities between health and disease in a situation depending on a great complex of variables. - 13 - HONS 028903 TI1K riOJDICTICN OF EFFECTS In predicting whgit will hoppen under a variety of circumstances, it in clear f'Pt wo must take account of the sensitivity of organisms to various levels of exposure to both individual significant pollu tants and combinations of pollutants. Ve must also endeavour to predict the levels of exposure at those turret organisms, nnd these in turn depend on the pathways of the pollutants and the factors determining their rate of input to and removal from tho environment. It is well known that all chemical substances vary in those respects. It is self-evident that the pollutants likely to attain significant concentrations in regions remote from their sources of emission arc those released in large quantities, readily soluble in water or cosily dinporoed in air, having a rapid rote of diffusion and having a low rate of chemical or biological transformation into innocuous products or a low rate of settlement of sedimentation from air or water in which they are suspended and perhaps ultimately exhibiting the phenomenon of concentration via food chains. Those of high persistence, but less ready dispersal, on the other hand, are clearly type-cost to create "hot spots" about points of emission. In both cases, if we know about their inherent toxicity and the way by which that toxicity takes effect, we have the recipe for predicting tho likely seriousness of a pollutant substance. It would bo useful were we able to go further than this, and predict from the molecular structure of a substance what its behaviour in the environment was likely to be. Sometimes this can be done to a degree, as with the probability of biodegradation of certain detergents - 14 - MONS 028904 o recent noynl Society discussion cxnoced tho limitations of thia approach k-------:--------------Kvon minor structural ohnnp;os alter the behaviour of molecules to a surprising decree. for tho foreseeable future wo can expect to have to rely as the chemical industry now does on laboratory and field testing prior to tho introduction of new substances or new formulations, '..hat we can ensure however is that the mass of available information is more effectively retrieved, and this is the aim of the information referral system boinfr developed for the United Nations, with the active participation of tho UK Chemical Information Service /sv.scircy;-- Tho construction of meaningful numerical models of environmental pollution is- extremely difficult. Not only is one confronted with the almost endless variation in biological response, but tho curves relating; omissions to concentrations in the environment at a particular point and time are influenced by a very larfie number of factors, '..'e hove at the present time some relatively crude models for the behaviour of pollutants in water, particularly rivers, which have the merit of beinft relatively confined.and subject to predictable patterns of flow. Such raodolo are boinR attempted for the sea, but ore prone to creat difficulty, while for air they have succeeded only at the most superficial level. Clearly, we need many more studies of pathways and effects, and these are the two key areas for research upon which must depend our social response in terms of judrcinK the relative seriousness of a pollution problem and therefore the priority v/e must piv0 to its control. For wo must remind ourselves thn't wo live in n world in which chemical factors arc, and always have been, important in ocolorry and physiology. Many of tho pollutnnta to which wo ore exposed are natural substances whose concentrations and distributions, rnthor than HONS 028905 15 eliminate thono substances; indeed many of them are essential at low concentrations to our well-being. We could not expect to take their concentrations buck to pre-induntrinl leveln even if wo knew what those wore. What wo nan do is nook to predict the points at which thoir concentrations become socially unacceptable and to work out the most efficient means, in economic and technological terms, of restrict ing those levels below that threshold. And none pollutants, op, l'CB3, are entirely unknown in nature. Here also we must apply the principle of restricting their concentrations to the threshold of nociul unncceptibility. On the basis of this knowledge, too, we can make a more sensible decision about the parameters we need to monitor in the environment and the frequency of the sampling we require in space and time, fuitc evidently, that monitoring mu3t allow us to assess as accurately and precisely as possible the degree of exposure of various tnrgeto. It would bo logical to sen the network of measurements most closely grouped about targets in which v;c arc not prepared to see any significant changes at individual level, while a looser network of monitoring might be acceptable where we are concerned only to prevent changes at the ecosystem -level. Moreover, if we are prepared to accept changes at all levels short of the ecosystem level, biological monitoring bocomeo evidently acceptable. If we monitor the performance of indicator species, we are tacitly accepting that we are prepared to sec their numbers or their performance impaired but because the ecosystem level is unlikely to show change until such impairment at individual level has occurred on a substantial scale, the biological monitoring programme yet gives U3 something of a safety factor and time span in which to effect corrections should that bo needed. On the other hand, biological monitoring may be lens acceptable where wo - 16- MONS 028906 are ueoking to prevent damage at the individual level unless kc onn .find an organism which if! on order of magnitude more susceptible than the targots we qre chiefly coneornod to protect and displaying a similar sensitivity to the whole interacting matrix of foctors. Alternatively, we can monitor at the biochemical Dovol (for example following lend levels in human blood or organochlorine levels in wild life) so ns to pain early warninp of effects at tho orpan or individual level. Whatever conclusion we reach, the desipn of a competent monitorinp system must be grontly influenced by our knowledge of tho exposuro-effect relationship between pollutants and th'e -targets with which we are particularly concerned. TRENDS IN POLLUTION AND SOCIAL RESIONSE Pollution has become a subject of increasing national and international concern in the last two decades. But it is fair to point out that the majority of the incidents which have served to focus this concern have been due to localised concentrations of particular pollutants in pollution "hot spots" (eg smoke and sulphur dioxide in the London "smogs" of tho 1950s, mercury and cadmium in water receiving effluent from certain Japanese factories, and raised blood lead levels near a number of. factories using lead). It is also fair to add that while the number Of incidents causing concern has mounted, tho actual damage duo to pollution has declined: London "pea-soupers" and acute pollution near ' industries almost certainly harmed more people fifty years ago. What has increased is our capacity to diagnose the problems, our will to respond, and our fastidiousness in environmental matters. HONS 028907 There is no evidence of damage to human health or ecological stability oil a global scale, due to a globally-distributed pollutont (except perhaps for tho statistical prediction of increased radiation damarr. iui> vw vits, u j. wuv Ui uut.i^;iu *v *; u | ;u J l x< w'it; ntnosphore). The most-quoted examples of global trendy in pollution, the gradual increase in the proportion of carbon dioxide in the atmosphere, the trace quantities of DDT ur.d other pesticides to be found in oceans and wildlife throughout the world, and the possible changes in atmospheric turbidity due to the .injection of fino dust into tho air, are all no more than changos in pollutant level without as yot proven consequences for living "targets". nonetheless, it does not follow that increased emissions of pollutants will not have unwelcome effects, both through the creation of more and more unacceptable local "hot spots" and through the elevation of the general level of contamination of ocean and atmosphere to tho ooint at which undesirablo climatic or ecological changes ensue. Granted that tho latter process, in particular, is likely to build up slowly and require an equally long time and great effort to reverse, it in clearly important to improve uuf scientific knowledge- of pollutants and their effects and our predictive capability, an well as our technical capacity to control pollution. In tho past, we have allowed pollution domngo to develop, and had to cure it when we no longer found it acceptable; in tho future we need to forestall such damage, and this requires better understanding than we now hnve, . TrtKMDI IK rOII/UTANT EMISSION It is a historical fact that some pollutants have been omitted in stoudily rising quantities, in parallel with mounting human populations and Increasing industrialisation. The generation of nan's body w.-stos and food residues, and tho body wanton of his livestock, inevitably rise in direct proportion to population. Energy generation through the 10 - HONS 028908 burning of fossil fuel releases carbon dioxide, carbon monoxide, oxides of nitrogen nnd of sulphur,' water-vapour, hydrocarbons and n variety of particulates. Total emissions of all these 1 :vo risen steadily over past docadoo or even centuries, although nun ntill adds lorsa of many of them to the environment than is contributed by natural processes. There is a similar tendonc^ for the vastly wider range of pollutants generated by industry likewise to rise in direct relation to industrial growth, unless anti-pollution measures arc taken, or unless inherently 'cleaner' processes are developed. But in practical terms many of the most noxious substances - persistent orgnnohnlogens, heavy metals, radioactive natorialo and known carcinogens - are being released in diminishing amountsnnd their concentration in the biosphere - in the UK, if not globally - is fulling. This in because of recognition of the need for abatement and the ' development of increasingly efficient pollution control technology. The pollutants still on a rising trend are generally thoso not known to be harmful at present or projected levels and hence not yet justifying control, liecognition of the need for control, eg on omissions of hydrocarbons, carbon monoxide and lead from cars, lead from industry or sulphur oxides from low level chimneys., has already begun to affect the trends in the products of fossil fuel combustion, until recently looked on as harmless. However, abrupt changes in the cost of various fuels will necessarily have a modifying effect on control policies ndopted in future for various forms of energy generation. For we live in a situation where marginal benefits nnd marginal control costs have to be balanced, and the balance can shift cither way. - 19 - HONS 028909 FACTORS INFbUENCIKG FUTURE TREK DU In crude torrao the concentration of a pollutant in tho environment in tho result of omission nnd removal. In practice.! termo, the important determining factor is man's deliberate control over emissions. This is in turn governed by the costs and benefits of tho activities loading to tho Generation of the pollution and the actual or predicted cost to the community of tho damage it does. Research, lendinG to a deeper undcrstandinG of these matters is likely to be a powerful determinant of tho actual future trends in emission, concentration and effects of any substance. It is impossible to cataloGue all major pollutants and predict their future levels. But we can reliably forecast a continuing decline in damaging industrial emissions such as acidic and alkaline vapours, particulates and heavy metals, nnd in persistent organohologons such as PCBo and DDTs, for which substitutes cither exist or are being sought. Wo can predict a slowing down in the upward curve of emission of pollutants from motor vehicles since most developed countries are adopting standards that will halt, or even reverse, this trend within their borders. Substitution of nuclear for fossil energy sources will also lend to a not decline in gaseous and particulate emissions, although imposing a demand for continuing stringent controls on radioactive discharges. Recent international agreements seem to lead to a progressive reduction in the dumping or discharge of organohalogons, oils, heavy metals and known carcinogens to tho sea and rivers, and the levels of those substances in the ocean and marine life should soon begin to fall. MONS 028910 Nevertheless, pollutants continue to bo an inevitable accompaniment of man's increasingly technological society, nnd we shall always have to dispose of in the onvironment. Tnds''d. it is oni.i -r legitimate to uso the environment for thin purpose, so long no we do not over-tnx itu finite capacity to disperse and degrade aston. With increasingly stringent demands for the testing of now substances for environmental effects before they are used or discharged, and increasingly precise analytical, toxicolog.i.cal roncarch methods at our disposal, the probability in that pollutant levels will loss and less frequently bo allowed to mount to tho point at which damage begins. THE TREND IN THE COdT OF rOLl/UTIOK COJITliOL This cssontially optimistic projection is Grounded on history, for in Britain and moot other developed countries, pollution has become a diminishing problem as our awareness, scientific understanding and technological capabilities have grown. But there ia a price to pay for continued optimism. There is a tendency for the energy cost of pollution abatement or prevention to rise disproportionately as popula tions prov/ and tho standard of living and technological development increase. This is because: (a) the capacity of the environment to disperse and degrade pollutants is finite, and any increment of pollution over and above that capable of natural degradation demands treatment prior to release, (b) tho larger that increment, the purer the effluent may hove to be, volume for volume, if tho qualify of the environment is to bo sustained, HONS 028911 (c) the costs of removing pollution from an effluent tend to mount exponentially as one moves towards greater purity, (d) tho development of substitute or new products becomes more and room costly as the comnunity demands increasingly strini .ia teats of their safety, (o) the environmental quality which people demand tends also to rise in parallel with the standard of living, and this provides a "positive feed-back" increasing the costa listed above, (f) as we become more and more dependent on technology to purify emissions and protect the environment, so the consequences of break-down become leps acceptable and more thorough "fail-safe" mechanisms nre needed, often a.t substantial cost (c.f. the standards required for nuclear as against convential power stations). As economic and technological growth proceeds, an increasing proportion of GNF thus tends to be demanded for environmental protection, Tf this is to be prevented, increasing effort needs to be devoted to the development of better, safer and room efficient technologies, giving higher quality controls at less. cost. This is one of the needs of society to which chemistry has shown itself responsive, and must continue to respond. HONS 028912 Cant-dorm for firniroe Figure 1. The pathways of pollutants from source to the point of effect. Figure 2. The pathway of sulphur dioxide in air (from Kellogg, V/ Cudle, H.D., Allen, E H, Lazarus, A L and Kartell, K A, Science (February 1072), Vol. 175, No 4022). Figure J. Thresholds of sulphur dioxide effect on some plants ' and people. MONS 028913 Sources HONS 028914 Chesical Transformation in Air or iat6r PIGU2S 1 Dispersion Via Air or Eater_____ Contanination of Drir.Jd.n5 Eater or food Surface cr target -------------(permeability varies according to nature of substance and surface) Dispersion cithin Target (affected by solubility, reactivity etc.) 3iochesical Interaction Soil Clerical Transformation in Soil--------------------- ----- Pathray in Eedius Entry to Target Pathway to Target XSO i Particles in Lower Stratosphere Grow by CoacjuUtson ami Settle Out or Mix Downward (1 to 2 Vrs. Residence Time) * Sulfur and S compounds Deposited in S*.`dirt;cr`t Carried to Oceans l>v Rivers TOTAL * = 2G8 - f Hi. 2 Stun * c\ mul sink ' of uiitu>'p}um sulphur < t>r)i[u>u/tif\. Cntts arc HT tons rah ulata! c/\ sulphate per vein . r^7ii: I'.r f jyt /&;,/, 7 ; T&t*. J> water. xceetath^n .t structures: cip/thc\ max he !rails- >concem arc those emitted m laree qtiantfricir-e'pecia!| ornicil in the air into other substances which, in soine as a result of iWf eomhiistion. The chic!' of these ar 'be more obno\ioi:yihan the orininul on carbon dio\uio/c;trbon monoxide. Indroearbonv oxide HONS 028915 00.Q00 -i ' 10.000 H 1,000 100 H 10- PEOPLE TOLERABLE BY HEALTHY ADULTS AT WORK PLANTS 1 C-Ij-4000 +SMOKE MANV increased death; c 250p threshold OF S0| action alone j- harmful to sensitive people HARMFUL TO MOST plants -400 MOST LICHENS ELIMINATED -170 . SOME CROP PLANTS DAMAGEO OR CHECKED c- 500 + SMOKE C--300 . > BRONCHITIS AFFECTED -85. , SOME CONIFERS ATTCCTED -30 SENSITIVE LICHENS AFFECTED -12 ' . NOT ENOUGH FOR MAXIMUM ' CROP GROWTH IN SOME AREAS SO -CONCENTRATION P s / m " C5 NATURAL BACKGROUND HONS 028916 0J