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Regulatory Principles and Objectives
18 Regulatory Principles and Objectives
Prevention and control of an adverse environmental agent involves three considerations: (1) the formulation of some measure of the amount or concentration of the agent in the environment that is judged to be adequate for the preservation of health or other objective; (2) the availability and feasibility of methods for keeping the amount or concentration of the agent from exceeding the limits that would achieve this preservation; (3) the establishment of an optimum resolution of any conflicts that may arise between what is desirable and what is feasible, and a decision on what is acceptable. Two steps can be distinguished in the establishment of what is "acceptable," although some overlap often occurs in practice: (a) the preparation of criteria which set out what is known about the adverse effects of the agent in question, review the availability and feasibility of control measures, and suggest environmental levels that would be "acceptable"; (b) the formulation of regulations or standards for the practical administration of control measures, taking into account the information reviewed in the criteria, considering any social or economic factors involved, and setting clear guidelines for control. Standards, in general, set precise limits which must not be exceeded, while regulations usually content themselves with specifying the objectives and control procedures that would be deemed satisfactory, without insisting on precise levels to be observed; the distinction, however, sometimes becomes semantic. Standards (or regulations) may be directed at various points in the 431
432
18. Regulatory Principles and Objectives
transmission of the agent from its source to man. Emission standards are those which address themselves to discharges from a machine or plant, such as those from a smoke stack, waste pipe, or automobile. Ambient standards relate to the concentrations permitted in ambient or community air. Consumer standards specify the allowable concentrations in food, water, or consumer products. Occupational standards deal with conditions in the work place. A case has also been made for biological standards, which specify the allowable concentrations of the agent or of its metabolic products, in human, animal or plant tissues or excreta. Biological standards, however, provide information only after the event; they indicate when excessive intake has occurred, not when it is in the act of occurring, and are better regarded as useful for post-hoc monitoring, which may be sufficient where the effects are relatively mild and appear quickly after exposure.
INFORMATION R E Q U I R E D F O R FORMULATION O F CRITERIA
The key word in the requirements cited above is "acceptable". Acceptance implies an act of judgment, and judgments are notoriously arguable. The room for argument can be limited if there is adequate information about the various points that may arise, and if this information is set down clearly and systematically with proper documentation. This is the function of criteria; the more thorough the information provided, the less the scope for later argument. Differences of opinion will still develop, but at least they will be forced to deal with accumulated evidence. The essential information to be provided by the criteria may be considered under four headings: 1. The agent a. Its exact chemical or physical nature b. Methods for identification and quantitation and their degree of reliability c. Its adverse effects—nature of effects, severity of effects, number of persons at risk or extent of risk d. Conditions affecting its operation—environmental distribution, synergists and antagonists, dose-response relationships, time frame of effects, and variations in target susceptibility 2. Purpose of proposed standard or regulation a. Conservation of health of persons exposed—mortality, morbidity, productivity b. Prevention of deterioration of materials
Status of Information on Asbestos
433
c. Preservation of social values—esthetics, community morale, and property values Consequences of failure to control a. Medical Degree b. Social Time frame c. Economic Feasibility of control a. Availability of technology b. Possibility of undesired repercussions c. Cost of control d. Economic effects—short term and long term e. Social reaction—risk acceptance and job security
STATUS OF INFORMATION ON ASBESTOS Having enunciated the general principles for the development of regulatory measures, and having pointed out the types of information required, we can now look at the situation that we face with the specific agent, asbestos. The available information was reviewed in detail in Parts I through IV of this monograph, but it will be summarized here in terms of the headings just listed, so that those whose major concern is with regulation can get the essential background more readily. Reference will be made back to the earlier chapters for detail as necessary. The Agent Chemical
and Physical
Nature
From the extent of the discussions in earlier chapters (Chapters 2 and 3) it is evident that a considerable body of information of the type needed for control programs already exists, even though there may be some uncertainty on details. Methods for Identification and Quantitation While complex and time-consuming methods of identification and measurement are often necessary for special studies or the determination of some crucial matter, methods for mass application need to be relatively straightforward and easily replicated. The light microscopy methods described in Chapter 4 generally meet these specifications, but
434
18. Regulatory Principles and Objectives
they fail to distinguish fibers smaller than 0.5 μιη in any dimension and they do not permit the identification of a particular amphibole. Electron microscopy and associated techniques may permit such identification, but are very time-consuming and expensive. The practical use of electron microscopy for examination of routine samples waits upon the development of reliable automated methods with computer compilation of the emergent data. For critical situations many ancillary measurements may be made, but with added delay and cost. Such a difficult situation was described in the case of large scale water pollution in Chapters 4 and 5. Adverse
Effects
The major biomedical effects of asbestos dust, as reviewed extensively in Parts II and III, were seen to consist of four processes occurring in various degrees of combination: parenchymal asbestos or fibrosis in the substance of the lung; pleural asbestosis, or thickening and often calcification of the membranes lining the thoracic cavity; mesothelioma, a malignant tumor of the membranes lining the thoracic or abdominal cavities; and an increased incidence of carcinoma, particularly in the lung. The speed with which parenchymal asbestosis develops, and the severity of the involvement, varies with the degree of exposure. Under the extremely dusty conditions prevailing in the early years of the century, the disease could be well established in less than ten years from initial exposure, and result in death from cardiorespiratory insufficiency in less than 20 years. Under present day conditions, the rate of onset and the degree of disability from fibrosis is much reduced, but the consequent increase in life span ironically gives greater opportunity for the more slowly developing processes of carcinoma and mesothelioma to appear. The peak of incidence of pulmonary carcinoma deaths in asbestos workers appears 2 5 - 3 4 years, and of mesothelioma, 3 0 - 3 4 years after initial exposure. From the detailed data on prevalence given in Part III it is clear that the incidence rate of the neoplastic diseases is related more to lapse of time since initial exposure than to total dose. A low level of exposure can result in neoplastic response, particularly that of mesothelioma. In Table 1 2 - 4 citing the percentage of deaths from various causes in a cohort of 689 asbestos factors product and textile workers, for instance, the rate for lung carcinoma was as high (16%) in those with minimum as in those with high exposure to asbestos, whereas the rate for asbestosis increased steadily with the prevailing dust levels. Nor was there
Status of Information on Asbestos
435
any significant reduction of the death rate from mesothelioma in the lower exposure groups. The number of persons at risk from asbestos is hard to estimate, first, because there are no good statistics on the number of persons employed in the various industries handling asbestos. (Even if the employees of the major mining, milling, textile, asbestos-cement, and other plants were enumerated, there would still remain an unknown number of persons handling asbestos almost incidentally in the course of their trades.) Second, the degree of exposure varies greatly with the nature of the j o b ; third, a certain number of persons, such as the families of asbestos workers, may suffer nonoccupational exposure; and fourth, work practices and dust control measures are changing and other materials are being substituted for asbestos (as in the manufacture of insulating materials). It has been estimated that there are about 200,000 workers exposed to asbestos in the United States (664), but this could be a marked underestimate. The National Institute for Occupational Safety and Health puts the probable figure of exposed persons at one million. The measure of uncertainty is suggested by the fact that some 3 0 % of mesotheliomas occur in persons with no ascertainable occupational or paraoccupational exposure to asbestos, yet this disease has emerged from the category of rare diseases only since the widespread use of asbestos, and no other agent has yet been incriminated. Influential
Conditions
Asbestos dust is naturally more prevalent at the handling site, but even here the atmospheric concentration varies with the nature of the material, the mode of handling, work practices, and general hygiene. That the dust may by no means be confined to these sites is evidenced by the occurrence of pleural plaques, almost pathognomic for exposure to asbestos, and the development of mesothelioma, in the employees of British and other shipyards who are not directly involved with the material (Chapters 8-11). Data on the presence of asbestos dust in air away from operational sites was cited earlier (Chapter 5), as was its distribution in water and certain other aliments. Areas downwind from asbestos plants and dumps are naturally more subject to contamination. In the absence of controls, the concentrations can be high and continual. Hopefully, these obvious situations are coming under control. The synergistic action of cigarette smoking and exposure to asbestos dust in the production of pulmonary carcinoma (but not of mesothelioma) was reviewed in Chapter 12, where the combination was seen to result in an incidence many times greater than that in
436
18. Regulatory Principles and Objectives
comparable persons who do not smoke and are not occupationally exposed. While a dose-response relationship can be demonstrated for parenchymal asbestosis, it is much less evident, as was noted above, for pulmonary carcinoma and mesothelioma, where quite a small exposure can set the development in train. While the time for development of parenchymal asbestosis can be just a few years where the exposure is heavy, it tends to a period of about 20 years under the conditions to which today's new cases were exposed. The period may possibly be longer, and the incidence lower in tomorrow's cases, working under conditions now prevailing in industry. As is common with environmentally-induced disease, and for that matter with infectious disease, a given degree of exposure does not produce the same degree of response in everyone. We are constantly struck by the fact that only some of those working under comparable conditions show pathogenic effects. Apparently there are differences in susceptibility that are far from being completely understood. One can speculate on the possible influence of breathing habits, leading in one person to a greater degree of entrapment in the nasopharynx; on eating practices, where food may be taken only away from the workplace and after cleansing of the hands and face; on the operation of other simultaneous insults to the respiratory system; on a more efficient series of defense reactions ranging from lung clearance to anticarcinogenic processes; and so on. Further elucidation of the causes of individual variability might point the way either to selection of personnel where exposure cannot be avoided, or to improved work practices; but our understanding of individual susceptibility is at present fairly nebulous. Purpose of Standard or Regulation For asbestos, the purpose of a standard or regulation is clearly the conservation of the health of persons exposed. Esthetic considerations do not loom large, even with today's socially sensitized work force; they were clearly ignored in the days when it was difficult to see across the room of a processing plant. In time, no doubt, the sight of an asbestos dust plume issuing from a work place, or the presence of rafter dust in nearby buildings, may have an effect on property values, but even then the concern would be secondary, no doubt, to the conservation of health. The question today is not whether health needs to be conserved; it obviously does. The real question is "how much health?", or more realistically, "how much cost or inconvenience are we prepared to pay for health?". Should it be our objective to reduce the risk of ill-health of
Status of Information on Asbestos
437
all exposed groups, families, and associates as well as asbestos workers, to that of the population at large, or should we aim more conservatively at removing the risk of a crippling degree of asbestosis appearing during the productive life of a worker? Until recently, national objectives seemed to be close to the latter, but there is abroad today a greater concern for minimization of the risk of mesothelioma and of an increased risk of carcinoma. Decisions on appropriate action are based on opinion, and the seat of influential opinion is changing. But whoever exerts the influence, the decision is a social decision, not a scientific and not a medical decision; although these disciplines must present the facts to the decision makers and are themselves entitled to opinions. Those who have the responsibility for social decisions must include the control of asbestos exposure in their list of responsibilities. Consequences of Failure to Control There is little that regulation can do for those exposed in the past, but it can see to if that those now working with or potentially exposed to asbestos escape adverse effects. The question is whether the controls now practiced are adequate to prevent these adverse effects, or whether they need tightening still further. In Chapter 7, evidence was adduced to show that what was the common practice of accepting 5 mppcf (all particles), as revealed by light microscopy, was still being attended by the development of some parenchymal asbestosis. As we will see in the next chapter (Chapter 19), more rigorous standards have been developed, and further stringency is under consideration. The opinion has been expressed (539) that a level in the work place of 2 lf 5/ml would virtually abolish the production of asbestosis in a normal working lifetime; proof, however, would be hard to come by. We do not have observations on a sufficient number of persons exposed at these levels for a sufficient length of time, and we have to take the estimate by responsible people on trust. As an act of faith, it is probably tenable, but it needs to be recognized as such. It should be understood that the figure of 2 lijml is simply a convenient level that hopefully would reduce the incidence of parenchymal asbestosis to an "acceptable" low level. It makes no pretence of protecting the exposed person against mesothelioma, an increased risk of pulmonary carcinoma, or even pleural asbestosis (Chapter 8). As with other tumorigens, it would be hard to show that there is any such thing as a "no response" level. We do not know the quantitative relationship between lower levels of exposure and the incidence of neoplastic responses in those who are exposed, or even if one exists. All that we
438
18. Regulatory Principles and Objectives
have is a range of opinions, based on scrappy evidence and more than a modicum of faith. As scientists, we may wish to reserve judgment; as public health workers, we cannot be so indulgent. The legal ramifications of the conflict between a hazard for scientific proof of injury and the ethical concern for probability of future health effect has been the subject of recent reviews (334,339). It is at this point that we encounter an inadequacy of the commonly used Threshold Limit Value (TLV) concept of environmental control (550). For chemical or physical agents that can be demonstrated to have a threshold dose, below which disease is unlikely to appear, the practice of setting environmental concentrations that will keep exposures down to that dose is sound. But where no such threshold can be demonstrated, the most that can be hoped for by reduction of exposure is a reduction in the number of cases that develop or a lengthening of the developmental (latent) period with a consequent increased expectation of life. A determinist approach has to give way to a probabilistic one. The decision to be made concerns, not elimination of risk and absence of disease, but a reduction of the probable risk to an "acceptable" level; and here, in particular, the term "acceptable" involves a high moral judgment—how much ill-health, or how many early deaths are "acceptable?"
Feasibility of Control Availability of
Technology
There seems to be general agreement that the technology to be described in Chapter 20 is capable of bringing the time weighted average (TWA) concentration of particles, as counted by light microscopy, down to 2 lijml. In some places this seems to be attained right now (167). With adequate monitoring and provisions for enforcement of compliance it could be maintained in enclosed spaces. Little can be done, however, about controlling the concentration of particles in open pit mining or other open air occupations beyond attention to control of dust generation and maximum use of natural ventilation. To the extent that the atmospheric burden cannot be kept down to the desired limits, personal protection is necessary for the worker, as will be explained in a later chapter (Chapter 20). Technological methods are available for the virtual elimination of the escape into community air of fibers from indoor industrial operations, but
Status of Information on Asbestos
439
some contamination will still occur from the operation of community devices such as brake drums until an effective substitute is introduced for the embodied asbestos; dumps may also contribute their quota. Cost of Control Changes of work practices, such as mixing fiber with a medium in closed containers, can be introduced with little increase in cost or reduction of efficiency; but where the installation of exhaust fans, ductwork, filters, and precipitators is necessary, the capital cost can amount to a very significant figure, and the maintenance of the system once installed is not without its expense. Equipment for monitoring the air, the personnel for operation of monitoring and analysis of samples, and personnel for enforcement add to the running cost of control. The costs will vary with the nature of the operation and need to be assessed for the individual case. Socioeconomic
Effects
The installation of control equipment or procedures is least costly when included in new plant design; it can be much more expensive when added to existing plant that may have already undergone many modifications or have outlasted technological development. Additions to the price of the product in compensation for control expenses may affect sales and the future of the company. If a situation forces reduction of personnel, or, worse still, closure of the plant, a sharp conflict of interests arises. It can be, and sometimes is, argued that acceptance of a life-shortening risk may be socially preferable to loss of employment, particularly for the older workers and in times of high unemployment. Here again, the argument is in the social rather than in the medical sphere. Factual analysis of the situation is not readily obtained, and opinions emotionally expressed are more likely to lead to confrontation than resolution. A social solution needs to be sought for what is essentially a social problem. Consideration of long-term social consequences lead to the term "cost/benefit ratio"; a term which has been alternately promoted and decried, but expresses a concept that is inseparable from the administration of national affairs. There is no end to the list of things that may be considered as benefits, but the resources to provide them are always limited. Optimum deployment of the available resources has always to be worked out, often in the face of quite varied interpretations of the same data by persons or groups with varied interests. A solution becomes particularly difficult when one tries to apply the cost/benefit
440
18. Regulatory Principles and Objectives
concept to matters involving human health and productivity. (Incidentally, the common reference to "saving of life" is a hyperbole; lives are never "saved," but they may be prolonged with advantage to all.) The costs of a proposed action, such as controlling exposure to asbestos dust, can usually be estimated with some confidence, once there is agreement on which items may legitimately be included. The benefits of diminished ill-health and prolonged life can be quantified insofar as the productivity of the individual and savings in medical care are concerned, but it is very difficult to assign a cash value to the intangibles of social sentiment that are given to prolonged life and health. The denominator of whatever cost/benefit ratio is calculated is changed by an indefinable amount that depends upon the attitude of the propoTABLE 1 8 - 1 Benefit/Cost Ratios Calculated under Alternative Assumptions ( 6 7 5 )
Number of lives "saved"
Constant benefits, constant costs A.
630 1596 2563
B.
630 1596 2563
Increasing benefits, decreasing compliance costs
4 % Discount rate; 50-year time period 0 Conventional measures 0.16 0.38 0.38 0.91 0.60 1.43 Unconventional measures 0.90 2.21 2.22 5.47 3.54 8.70
630 1596 2563
630 1596 2563
Increasing benefits, constant costs
a&
0.52 1.20 1.90
0
10% Discount rate; 100-year time period Conventional measures' 0.07 0.12 0.17 0.29 0.27 0.47 Unconventional measures'* 0.40 0.55 0.99 1.49 1.56 2.36
3.00 7.50 11.90
0.15 0.36 0.58 0.68 1.80 2.90
" With kind permission of R. F. Settle. In consideration of OSHA standard of 2 lf 5/ml. c Conventional measures put gains from reduced morbidity and mortality and treatment resource savings in the numerator. d Unconventional measures include all quantified benefits in the numerator. (For details of calculations and parameters, see original paper.) b
Status of Information on Asbestos
441
nent. Legislators are understandably chary of assigning values to such intangibles, and no completely acceptable formula has been devised. In the absence of firm guidance, judgment in the individual case is subject to the adversary approach, with resulting variability in decision, susceptibility to challenge, and possible injustice to one of the contesting parties. The range of items that should be taken into account in dealing with the tangible components of the ratio have been well reviewed by Settle (675). In tangible benefits he includes conserved productivity and savings in medical care in the broadest sense of the terms. His costs embrace those of industrial compliance, enforcement activities, increased prices of products, loss of production through reductions in employment to meet costs, and support for the unemployed. He assigned alternative values to the various components and to possible changes in discount rates. Calculations made by the author (he used a benefit/cost ratio, the reciprocal of the usual expression) will illustrate the great dependence of calculated outcome on the values assigned to the various parameters (Table 1 8 - 1 ) .
Prevention and control of an adverse environmental agent involves three considerations: (1) the formulation of some measure of the amount or concentration of the agent in the environment that is judged to be adequate for the preservation of health or other objective; (2) the availability and feasibility of methods for keeping the amount or concentration of the agent from exceeding the limits that would achieve this preservation; (3) the establishment of an optimum resolution of any conflicts that may arise between what is desirable and what is feasible, and a decision on what is acceptable. Two steps can be distinguished in the establishment of what is "acceptable," although some overlap often occurs in practice: (a) the preparation of criteria which set out what is known about the adverse effects of the agent in question, review the availability and feasibility of control measures, and suggest environmental levels that would be "acceptable"; (b) the formulation of regulations or standards for the practical administration of control measures, taking into account the information reviewed in the criteria, considering any social or economic factors involved, and setting clear guidelines for control. Standards, in general, set precise limits which must not be exceeded, while regulations usually content themselves with specifying the objectives and control procedures that would be deemed satisfactory, without insisting on precise levels to be observed; the distinction, however, sometimes becomes semantic. Standards (or regulations) may be directed at various points in the 431
432
18. Regulatory Principles and Objectives
transmission of the agent from its source to man. Emission standards are those which address themselves to discharges from a machine or plant, such as those from a smoke stack, waste pipe, or automobile. Ambient standards relate to the concentrations permitted in ambient or community air. Consumer standards specify the allowable concentrations in food, water, or consumer products. Occupational standards deal with conditions in the work place. A case has also been made for biological standards, which specify the allowable concentrations of the agent or of its metabolic products, in human, animal or plant tissues or excreta. Biological standards, however, provide information only after the event; they indicate when excessive intake has occurred, not when it is in the act of occurring, and are better regarded as useful for post-hoc monitoring, which may be sufficient where the effects are relatively mild and appear quickly after exposure.
INFORMATION R E Q U I R E D F O R FORMULATION O F CRITERIA
The key word in the requirements cited above is "acceptable". Acceptance implies an act of judgment, and judgments are notoriously arguable. The room for argument can be limited if there is adequate information about the various points that may arise, and if this information is set down clearly and systematically with proper documentation. This is the function of criteria; the more thorough the information provided, the less the scope for later argument. Differences of opinion will still develop, but at least they will be forced to deal with accumulated evidence. The essential information to be provided by the criteria may be considered under four headings: 1. The agent a. Its exact chemical or physical nature b. Methods for identification and quantitation and their degree of reliability c. Its adverse effects—nature of effects, severity of effects, number of persons at risk or extent of risk d. Conditions affecting its operation—environmental distribution, synergists and antagonists, dose-response relationships, time frame of effects, and variations in target susceptibility 2. Purpose of proposed standard or regulation a. Conservation of health of persons exposed—mortality, morbidity, productivity b. Prevention of deterioration of materials
Status of Information on Asbestos
433
c. Preservation of social values—esthetics, community morale, and property values Consequences of failure to control a. Medical Degree b. Social Time frame c. Economic Feasibility of control a. Availability of technology b. Possibility of undesired repercussions c. Cost of control d. Economic effects—short term and long term e. Social reaction—risk acceptance and job security
STATUS OF INFORMATION ON ASBESTOS Having enunciated the general principles for the development of regulatory measures, and having pointed out the types of information required, we can now look at the situation that we face with the specific agent, asbestos. The available information was reviewed in detail in Parts I through IV of this monograph, but it will be summarized here in terms of the headings just listed, so that those whose major concern is with regulation can get the essential background more readily. Reference will be made back to the earlier chapters for detail as necessary. The Agent Chemical
and Physical
Nature
From the extent of the discussions in earlier chapters (Chapters 2 and 3) it is evident that a considerable body of information of the type needed for control programs already exists, even though there may be some uncertainty on details. Methods for Identification and Quantitation While complex and time-consuming methods of identification and measurement are often necessary for special studies or the determination of some crucial matter, methods for mass application need to be relatively straightforward and easily replicated. The light microscopy methods described in Chapter 4 generally meet these specifications, but
434
18. Regulatory Principles and Objectives
they fail to distinguish fibers smaller than 0.5 μιη in any dimension and they do not permit the identification of a particular amphibole. Electron microscopy and associated techniques may permit such identification, but are very time-consuming and expensive. The practical use of electron microscopy for examination of routine samples waits upon the development of reliable automated methods with computer compilation of the emergent data. For critical situations many ancillary measurements may be made, but with added delay and cost. Such a difficult situation was described in the case of large scale water pollution in Chapters 4 and 5. Adverse
Effects
The major biomedical effects of asbestos dust, as reviewed extensively in Parts II and III, were seen to consist of four processes occurring in various degrees of combination: parenchymal asbestos or fibrosis in the substance of the lung; pleural asbestosis, or thickening and often calcification of the membranes lining the thoracic cavity; mesothelioma, a malignant tumor of the membranes lining the thoracic or abdominal cavities; and an increased incidence of carcinoma, particularly in the lung. The speed with which parenchymal asbestosis develops, and the severity of the involvement, varies with the degree of exposure. Under the extremely dusty conditions prevailing in the early years of the century, the disease could be well established in less than ten years from initial exposure, and result in death from cardiorespiratory insufficiency in less than 20 years. Under present day conditions, the rate of onset and the degree of disability from fibrosis is much reduced, but the consequent increase in life span ironically gives greater opportunity for the more slowly developing processes of carcinoma and mesothelioma to appear. The peak of incidence of pulmonary carcinoma deaths in asbestos workers appears 2 5 - 3 4 years, and of mesothelioma, 3 0 - 3 4 years after initial exposure. From the detailed data on prevalence given in Part III it is clear that the incidence rate of the neoplastic diseases is related more to lapse of time since initial exposure than to total dose. A low level of exposure can result in neoplastic response, particularly that of mesothelioma. In Table 1 2 - 4 citing the percentage of deaths from various causes in a cohort of 689 asbestos factors product and textile workers, for instance, the rate for lung carcinoma was as high (16%) in those with minimum as in those with high exposure to asbestos, whereas the rate for asbestosis increased steadily with the prevailing dust levels. Nor was there
Status of Information on Asbestos
435
any significant reduction of the death rate from mesothelioma in the lower exposure groups. The number of persons at risk from asbestos is hard to estimate, first, because there are no good statistics on the number of persons employed in the various industries handling asbestos. (Even if the employees of the major mining, milling, textile, asbestos-cement, and other plants were enumerated, there would still remain an unknown number of persons handling asbestos almost incidentally in the course of their trades.) Second, the degree of exposure varies greatly with the nature of the j o b ; third, a certain number of persons, such as the families of asbestos workers, may suffer nonoccupational exposure; and fourth, work practices and dust control measures are changing and other materials are being substituted for asbestos (as in the manufacture of insulating materials). It has been estimated that there are about 200,000 workers exposed to asbestos in the United States (664), but this could be a marked underestimate. The National Institute for Occupational Safety and Health puts the probable figure of exposed persons at one million. The measure of uncertainty is suggested by the fact that some 3 0 % of mesotheliomas occur in persons with no ascertainable occupational or paraoccupational exposure to asbestos, yet this disease has emerged from the category of rare diseases only since the widespread use of asbestos, and no other agent has yet been incriminated. Influential
Conditions
Asbestos dust is naturally more prevalent at the handling site, but even here the atmospheric concentration varies with the nature of the material, the mode of handling, work practices, and general hygiene. That the dust may by no means be confined to these sites is evidenced by the occurrence of pleural plaques, almost pathognomic for exposure to asbestos, and the development of mesothelioma, in the employees of British and other shipyards who are not directly involved with the material (Chapters 8-11). Data on the presence of asbestos dust in air away from operational sites was cited earlier (Chapter 5), as was its distribution in water and certain other aliments. Areas downwind from asbestos plants and dumps are naturally more subject to contamination. In the absence of controls, the concentrations can be high and continual. Hopefully, these obvious situations are coming under control. The synergistic action of cigarette smoking and exposure to asbestos dust in the production of pulmonary carcinoma (but not of mesothelioma) was reviewed in Chapter 12, where the combination was seen to result in an incidence many times greater than that in
436
18. Regulatory Principles and Objectives
comparable persons who do not smoke and are not occupationally exposed. While a dose-response relationship can be demonstrated for parenchymal asbestosis, it is much less evident, as was noted above, for pulmonary carcinoma and mesothelioma, where quite a small exposure can set the development in train. While the time for development of parenchymal asbestosis can be just a few years where the exposure is heavy, it tends to a period of about 20 years under the conditions to which today's new cases were exposed. The period may possibly be longer, and the incidence lower in tomorrow's cases, working under conditions now prevailing in industry. As is common with environmentally-induced disease, and for that matter with infectious disease, a given degree of exposure does not produce the same degree of response in everyone. We are constantly struck by the fact that only some of those working under comparable conditions show pathogenic effects. Apparently there are differences in susceptibility that are far from being completely understood. One can speculate on the possible influence of breathing habits, leading in one person to a greater degree of entrapment in the nasopharynx; on eating practices, where food may be taken only away from the workplace and after cleansing of the hands and face; on the operation of other simultaneous insults to the respiratory system; on a more efficient series of defense reactions ranging from lung clearance to anticarcinogenic processes; and so on. Further elucidation of the causes of individual variability might point the way either to selection of personnel where exposure cannot be avoided, or to improved work practices; but our understanding of individual susceptibility is at present fairly nebulous. Purpose of Standard or Regulation For asbestos, the purpose of a standard or regulation is clearly the conservation of the health of persons exposed. Esthetic considerations do not loom large, even with today's socially sensitized work force; they were clearly ignored in the days when it was difficult to see across the room of a processing plant. In time, no doubt, the sight of an asbestos dust plume issuing from a work place, or the presence of rafter dust in nearby buildings, may have an effect on property values, but even then the concern would be secondary, no doubt, to the conservation of health. The question today is not whether health needs to be conserved; it obviously does. The real question is "how much health?", or more realistically, "how much cost or inconvenience are we prepared to pay for health?". Should it be our objective to reduce the risk of ill-health of
Status of Information on Asbestos
437
all exposed groups, families, and associates as well as asbestos workers, to that of the population at large, or should we aim more conservatively at removing the risk of a crippling degree of asbestosis appearing during the productive life of a worker? Until recently, national objectives seemed to be close to the latter, but there is abroad today a greater concern for minimization of the risk of mesothelioma and of an increased risk of carcinoma. Decisions on appropriate action are based on opinion, and the seat of influential opinion is changing. But whoever exerts the influence, the decision is a social decision, not a scientific and not a medical decision; although these disciplines must present the facts to the decision makers and are themselves entitled to opinions. Those who have the responsibility for social decisions must include the control of asbestos exposure in their list of responsibilities. Consequences of Failure to Control There is little that regulation can do for those exposed in the past, but it can see to if that those now working with or potentially exposed to asbestos escape adverse effects. The question is whether the controls now practiced are adequate to prevent these adverse effects, or whether they need tightening still further. In Chapter 7, evidence was adduced to show that what was the common practice of accepting 5 mppcf (all particles), as revealed by light microscopy, was still being attended by the development of some parenchymal asbestosis. As we will see in the next chapter (Chapter 19), more rigorous standards have been developed, and further stringency is under consideration. The opinion has been expressed (539) that a level in the work place of 2 lf 5/ml would virtually abolish the production of asbestosis in a normal working lifetime; proof, however, would be hard to come by. We do not have observations on a sufficient number of persons exposed at these levels for a sufficient length of time, and we have to take the estimate by responsible people on trust. As an act of faith, it is probably tenable, but it needs to be recognized as such. It should be understood that the figure of 2 lijml is simply a convenient level that hopefully would reduce the incidence of parenchymal asbestosis to an "acceptable" low level. It makes no pretence of protecting the exposed person against mesothelioma, an increased risk of pulmonary carcinoma, or even pleural asbestosis (Chapter 8). As with other tumorigens, it would be hard to show that there is any such thing as a "no response" level. We do not know the quantitative relationship between lower levels of exposure and the incidence of neoplastic responses in those who are exposed, or even if one exists. All that we
438
18. Regulatory Principles and Objectives
have is a range of opinions, based on scrappy evidence and more than a modicum of faith. As scientists, we may wish to reserve judgment; as public health workers, we cannot be so indulgent. The legal ramifications of the conflict between a hazard for scientific proof of injury and the ethical concern for probability of future health effect has been the subject of recent reviews (334,339). It is at this point that we encounter an inadequacy of the commonly used Threshold Limit Value (TLV) concept of environmental control (550). For chemical or physical agents that can be demonstrated to have a threshold dose, below which disease is unlikely to appear, the practice of setting environmental concentrations that will keep exposures down to that dose is sound. But where no such threshold can be demonstrated, the most that can be hoped for by reduction of exposure is a reduction in the number of cases that develop or a lengthening of the developmental (latent) period with a consequent increased expectation of life. A determinist approach has to give way to a probabilistic one. The decision to be made concerns, not elimination of risk and absence of disease, but a reduction of the probable risk to an "acceptable" level; and here, in particular, the term "acceptable" involves a high moral judgment—how much ill-health, or how many early deaths are "acceptable?"
Feasibility of Control Availability of
Technology
There seems to be general agreement that the technology to be described in Chapter 20 is capable of bringing the time weighted average (TWA) concentration of particles, as counted by light microscopy, down to 2 lijml. In some places this seems to be attained right now (167). With adequate monitoring and provisions for enforcement of compliance it could be maintained in enclosed spaces. Little can be done, however, about controlling the concentration of particles in open pit mining or other open air occupations beyond attention to control of dust generation and maximum use of natural ventilation. To the extent that the atmospheric burden cannot be kept down to the desired limits, personal protection is necessary for the worker, as will be explained in a later chapter (Chapter 20). Technological methods are available for the virtual elimination of the escape into community air of fibers from indoor industrial operations, but
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some contamination will still occur from the operation of community devices such as brake drums until an effective substitute is introduced for the embodied asbestos; dumps may also contribute their quota. Cost of Control Changes of work practices, such as mixing fiber with a medium in closed containers, can be introduced with little increase in cost or reduction of efficiency; but where the installation of exhaust fans, ductwork, filters, and precipitators is necessary, the capital cost can amount to a very significant figure, and the maintenance of the system once installed is not without its expense. Equipment for monitoring the air, the personnel for operation of monitoring and analysis of samples, and personnel for enforcement add to the running cost of control. The costs will vary with the nature of the operation and need to be assessed for the individual case. Socioeconomic
Effects
The installation of control equipment or procedures is least costly when included in new plant design; it can be much more expensive when added to existing plant that may have already undergone many modifications or have outlasted technological development. Additions to the price of the product in compensation for control expenses may affect sales and the future of the company. If a situation forces reduction of personnel, or, worse still, closure of the plant, a sharp conflict of interests arises. It can be, and sometimes is, argued that acceptance of a life-shortening risk may be socially preferable to loss of employment, particularly for the older workers and in times of high unemployment. Here again, the argument is in the social rather than in the medical sphere. Factual analysis of the situation is not readily obtained, and opinions emotionally expressed are more likely to lead to confrontation than resolution. A social solution needs to be sought for what is essentially a social problem. Consideration of long-term social consequences lead to the term "cost/benefit ratio"; a term which has been alternately promoted and decried, but expresses a concept that is inseparable from the administration of national affairs. There is no end to the list of things that may be considered as benefits, but the resources to provide them are always limited. Optimum deployment of the available resources has always to be worked out, often in the face of quite varied interpretations of the same data by persons or groups with varied interests. A solution becomes particularly difficult when one tries to apply the cost/benefit
440
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concept to matters involving human health and productivity. (Incidentally, the common reference to "saving of life" is a hyperbole; lives are never "saved," but they may be prolonged with advantage to all.) The costs of a proposed action, such as controlling exposure to asbestos dust, can usually be estimated with some confidence, once there is agreement on which items may legitimately be included. The benefits of diminished ill-health and prolonged life can be quantified insofar as the productivity of the individual and savings in medical care are concerned, but it is very difficult to assign a cash value to the intangibles of social sentiment that are given to prolonged life and health. The denominator of whatever cost/benefit ratio is calculated is changed by an indefinable amount that depends upon the attitude of the propoTABLE 1 8 - 1 Benefit/Cost Ratios Calculated under Alternative Assumptions ( 6 7 5 )
Number of lives "saved"
Constant benefits, constant costs A.
630 1596 2563
B.
630 1596 2563
Increasing benefits, decreasing compliance costs
4 % Discount rate; 50-year time period 0 Conventional measures 0.16 0.38 0.38 0.91 0.60 1.43 Unconventional measures 0.90 2.21 2.22 5.47 3.54 8.70
630 1596 2563
630 1596 2563
Increasing benefits, constant costs
a&
0.52 1.20 1.90
0
10% Discount rate; 100-year time period Conventional measures' 0.07 0.12 0.17 0.29 0.27 0.47 Unconventional measures'* 0.40 0.55 0.99 1.49 1.56 2.36
3.00 7.50 11.90
0.15 0.36 0.58 0.68 1.80 2.90
" With kind permission of R. F. Settle. In consideration of OSHA standard of 2 lf 5/ml. c Conventional measures put gains from reduced morbidity and mortality and treatment resource savings in the numerator. d Unconventional measures include all quantified benefits in the numerator. (For details of calculations and parameters, see original paper.) b
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nent. Legislators are understandably chary of assigning values to such intangibles, and no completely acceptable formula has been devised. In the absence of firm guidance, judgment in the individual case is subject to the adversary approach, with resulting variability in decision, susceptibility to challenge, and possible injustice to one of the contesting parties. The range of items that should be taken into account in dealing with the tangible components of the ratio have been well reviewed by Settle (675). In tangible benefits he includes conserved productivity and savings in medical care in the broadest sense of the terms. His costs embrace those of industrial compliance, enforcement activities, increased prices of products, loss of production through reductions in employment to meet costs, and support for the unemployed. He assigned alternative values to the various components and to possible changes in discount rates. Calculations made by the author (he used a benefit/cost ratio, the reciprocal of the usual expression) will illustrate the great dependence of calculated outcome on the values assigned to the various parameters (Table 1 8 - 1 ) .