Ethics, Threshold Limit Values, and Community Air Pollution Exposures*

Jim Tarr, P.E.

IN THIS ARTICLE:
Air Pollution and Health
Threshold Limit Values
Air Pollution Control and TLVs
Health Effects at the TNRCC
Ethical Considerations

INTRODUCTION

One of the most significant problems in the field of air pollution control involves the task of deciding what level of toxic chemical exposure is acceptable in a community setting. The task is made daunting by the need to make judgments about literally thousands of different chemical substances. Often there is a dearth of human health effects information related to a particular chemical. If information is available, it is often contradictory, sketchy, difficult to interpret, or derived by an entity with a vested interest in the economic aspects of the chemical in question.

Given the need to act, a number of regulatory agencies have chosen to rely on so-called threshold limit values (TLVs) to develop acceptable levels of community exposure to toxic chemical emissions. The purpose of this discussion is to examine the technical basis for this approach, to review the uses of TLVs in state air pollution control programs, and to consider some of the ethical considerations that are inherent in the use of TLVs in assessing community air pollution exposures. The practices of the Texas Natural Resource Conservation Commission (TNRCC) will be given particular attention.

AIR POLLUTION AND HEALTH

The year 1962 marked a watershed in the environmental movement in the United States. Henceforth, the environment, human health, and exposure to toxic chemicals were inextricably linked. Rachel Carson catalyzed that new perspective when she presented eloquent and persuasive arguments based on the premise that for the first time in history all people were subjected to contact with toxic chemicals from the moment of their conception to the time of their death.1 Historically, air pollution control at the state level derived from the legal concepts of trespass and common law nuisance. In the wake of Carson's teachings, the emphasis for controlling air pollution was sharpened. In 1967, the U.S. Congress passed legislation to provide financial assistance to states to establish comprehensive air pollution control programs. By 1970, all fifty states had adopted laws to control air pollution.2 The primary thrust of those various state laws was protection of public health from the adverse effects of exposure to air pollution, that is, toxic chemical substances. That message was articulated in language like that found in the Declaration of Policy of the Health and Safety Code of the State of California as amended by the Pure Air Act of 1968 and by laws of 1969, which in essence declared that the health, safety, welfare, and sense of well-being of ordinary people were the primary concerns in the field of air pollution control.3

THRESHOLD LIMIT VALUES

TLVs are numbers that refer to airborne concentrations of substances. Those numbers were first introduced into the lexicon in 1942 by a group called the American Conference of Governmental Industrial Hygienists (ACGIH).4 TLVs define exposure levels related to people employed in the industrial workplace. They are said to represent the maximum average concentrations of contaminants to which workers may be exposed for an 8-hour work shift, five days a week, without injury to health.

The TLV concept is seriously flawed in a number of respects. Concurrent with the first publication of a list of TLVs, the idea that a given value represented a safe concentration was specifically rejected. On the contrary, the use of TLVs was simply meant to provide guidance for the control of health hazards in the workplace. Some ten years later, the idea that a TLV was equivalent to a level of safe exposure to a chemical substance was introduced by the ACGIH with little or no scientific justification.5

Three decades passed before that particular misconception was corrected in the scientific literature. It was shown that TLVs were, in general, poorly supported by scientific evidence, but were developed with a great deal of consideration given to the cost of controlling exposure.6 TLVs were developed with inadequate medical input, lack of scientific rigor, and by advocates with important financial conflicts of interest.7 The process of selecting a particular value for a TLV for a specific chemical was done in a setting in which technological and economic feasibility was an integral consideration.8

Recently, the recognition that TLVs are not thresholds at all has come full circle. It has been shown that adverse health effects occur in people at or below the level of exposure defined by the TLV for a number of chemical substances.9 The designation TLV has even been judged to be meaningless because the very concept no longer accords with what is known about the relationship between occupational exposure and human health risk.10

Most importantly from an environmental protection perspective, the use of TLVs in a community air pollution setting is completely contrary to recommended practice. The document that lists values for workplace TLVs explicitly states that said values are not intended for use or for modification for use in assessing community air pollution exposures or for estimating the toxic potential of continuous, uninterrupted exposure to chemical substances.11

AIR POLLUTION CONTROL AND TLVs

A number of state and local air pollution control agencies use TLVs as a basis for controlling community air pollution exposures. That usage became more popular in the mid-1980s when the EPA began to delegate the responsibility of controlling toxic air emissions to various state agencies. The shift from federal to state control was begun in the wake of many years of failure on the part of the EPA to effectively regulate toxic chemical emissions under Section 112 of the federal Clean Air Act. To make matters worse, this new scheme was initiated by the EPA with a minimum of effective financial and technical support.12

In spite of obvious difficulties, for a number of air pollution control agencies the idea of using TLVs, or some modification of those numbers, apparently was an irresistible solution to a very difficult problem. By 1989, almost one-half of all states had incorporated the use of TLVs in their air pollution control efforts to limit public exposure to toxic chemical emissions. Among those states were some of the most populous in the U.S. including California, Connecticut, Florida, Michigan, New York, Ohio, Pennsylvania, and Texas.13

HEALTH EFFECTS REVIEW AT THE TNRCC

The TNRCC is the government agency in Texas charged with controlling air pollution. One of its predecessor agencies, the Texas Air Control Board (TACB), actually created the system that is used to pass judgment on community toxic chemical exposures in the state.

Initiated in the mid 1970s, the TACB approach to regulating community toxic chemical exposure was the development of the effects screening level (ESL) system. The original system was based almost entirely on fractional TLVs. Acute health effects screening levels were judged on the basis of comparing a predicted ambient air concentration to 1/100th of the TLV (30-minute average). Chronic health effects screening levels were based on a comparison of predicted concentrations with one/1000th of the TLV (annual average) for a toxic chemical of interest.14

At least two of the important premises on which the TACB's ESL system was based were deeply flawed. One of those premises was that if predicted ambient air concentrations of a toxic chemical did not exceed the ESL for that chemical, then no adverse health effects would occur. There was no valid scientific basis for that claim when it was made, and there is certainly none now. A second flawed premise was that if a permit applicant proposed to control air emissions with the "best available control technology," and if the applicant designed the proposed facility to protect workers from hazards, then residual public exposure to the toxic chemical air emissions from that facility would be acceptably low.15 This claim was made in spite of the fact that the TACB was statutorily prohibited from evaluating and regulating industrial hygiene matters in facilities. Furthermore, there was not then, and there is not now any direct connection between engineered pollution control devices and the response of nearby biological systems.

A confounding difficulty soon became apparent. The ESL system could only be employed in conjunction with those toxic chemicals for which a TLV existed. There are currently published TLVs for approximately 750 toxic substances. By 1987, the TACB had applied the ESL system to more than 1,800 different chemicals.16 This feat was made possible by the creation of numbers that, in candor, must be called pseudo-TLVs. A pseudo-TLV is a number that is not derived from human experience in the industrial workplace, but instead, is derived from a comparison of chemical structures and the toxic effects of other chemicals.17 In 1987, the TACB had apparently made health effects decisions on fully two-thirds of all chemicals they considered using pseudo-TLVs. To paraphrase their own description of the method, the derivation of pseudo-TLVs did not represent a pure science approach but it did allow the permit review process to proceed at a reasonable rate.18

Experience demonstrates that the ESL system at the TNRCC exists primarily for the convenience of the agency and to some degree for the economic purposes of the corporations that the agency is charged with regulating. The TACB has flatly stated that the system provides major advantages for the regulated community. For example, the acceptable levels of community exposure to toxic chemicals are said to be readily achievable. They also point out that the system does not prohibit modernization and industrial growth in the state. Furthermore, companies are not burdened with the need to provide extensive toxicity testing results for those dangerous chemicals they may want to emit into the environment.19 Another stated advantage for industry is that the ESL guidelines are flexible. They are also said to bring consistency to the review process.20

And in one of the more telling statements of the TACB, it was pointed out that the regulatory agency can explain the meaning of the ESLs to the public, indicating that the TLVs upon which the numbers are based represent concentrations to which industrial workers may be exposed over a lifetime without adverse effect.21 Stated another way, one goal of the ESL system is to use the presumed prestige of the omniscient regulatory agency as a means to mollify public concern about the emission of toxic chemicals into the environment.

Also, of most practical value to those who emit toxic chemicals into the atmosphere, it is clear that predicted ambient air concentrations greater than an ESL will not cause serious difficulty for a permit applicant. The TACB has declared that an exceedance of an ESL does not necessarily mean that a proposed project will not be approved.22 In fact, said finding may not represent a problem at all.23 Exceedances of ESLs are routinely considered acceptable.24 Taken as a whole, the record reflects that the agency will acquiesce to avoid prohibiting the emission of toxic chemicals into the atmosphere whether or not that action threatens the health of ordinary people.

The agency purports to conduct health effects reviews with thoroughness, fairness, and flexibility.25 Clearly, their real concerns about fairness fail to include those who breathe the toxic chemical emissions that are allowed under the auspices of a discredited system. They also categorically state that if their ESLs are not exceeded then no adverse health effects will occur.26 That all encompassing claim is made with the certain knowledge that the agency has failed to conduct the research needed to document that kind of sweeping generalization.27

Current TNRCC procedures explicitly include a premise that an ESL can be exceeded without creating an unacceptable increase of adverse human health or welfare effects.28 Those increases may be acceptable to the agency and the regulated entities, but the interests of the people who must bear the subsequent risks remain unspoken and unrepresented in any meaningful way.

ETHICAL CONSIDERATIONS

There are at least two systems of ethical thought that are of interest in the present context. One system involves a utilitarian approach to ethical reasoning based on the idea of doing the greatest good for the greatest number. Another relevant ethical system flows from the concept of deontology, or an approach based on duties and obligations.29 These systems share a number of basic principles.

Non-malfeasance
The principle of non-malfeasance requires the practitioner to refrain from doing harm. It is a familiar concept, perhaps best stated in the physician's ethical charge: "First do no harm."

In an air pollution control setting, the concept of non-malfeasance places a substantial burden on an agency charged with protecting human health. The clear implication is that such an agency would have to gather a lot of information about a toxic chemical and its possible health effects before allowing the release of that chemical into populated areas. Definitive, incontrovertible evidence concerning the toxic properties of the chemical in question would have to be readily at hand. The information would have to be exactly relevant to the subject population. Unbiased evaluations by highly trained, skillful practitioners with the authority to make unpopular decisions would be normal operating procedure. None of these is an integral part of the health effects review system at the TNRCC. The best that can be said about the system is that TNRCC usually does not know whether the toxic chemical emissions it allows will actually harm anyone. There is certainly no demonstration that those emissions will do no harm. In spite of that lack of knowledge, TNRCC routinely permits toxic chemical emissions from many sources.

Autonomy
Simply stated, the ethical principle of autonomy requires respect for persons, all persons. In this context, respect for persons must be maintained in a situation where the interests of one group are in actual or potential conflict with the interests of another group. The entities that the TNRCC regulates tend to be corporations with an overriding need to make as large a profit as possible. Controlling, or perhaps completely eliminating, the emission of a toxic chemical may well represent a cost, and make profit difficult or impossible. The regulatory agency must respect that need, but balance the profit motive against the needs of the broader community. Community needs include the need for a healthy environment. In fact, the very laws that created the TNRCC mandate the protection of human health and welfare as the concern of primary interest. Respect for the broader community must therefore command the highest priority if this ethical principle is to have meaning.

At the TNRCC, respect for the broader community is not reflected in the day-to-day workings of the health effects review system. The agency operates in such a manner as to subjugate the interests of the broader community to the interests of corporations. In fact, agency descriptions of their intent with respect to the ESL system make it clear that they intend to place themselves in the position of advocates-convincing the community that a given toxic chemical exposure is harmless in spite of the fact that the methods of review are scientifically invalid, superficial, and oftentimes applied in a manner best characterized as slipshod. This ethical standard is therefore not met by the reality of the workings of the health effects review system at the TNRCC.

Justice
The ethical principle of justice speaks to the equal administration of policy and to the equitable allocation of resources to all segments of society. In an air pollution regulatory context, the implication is that all segments of the community are approached in an evenhanded way and treated in a fair and equitable manner with regard to the resource of clean air.

The TNRCC health effects review system is unjust for a number of reasons. The burden of toxic chemical exposure falls predominately on that segment of the community that resides in close proximity to industrial facilities. In Texas, that often means the poor, the undereducated, and minorities. It is also clear that the workings of the agency are significantly tilted toward meeting the needs of the corporations responsible for emitting toxic chemicals into the environment. Since 1972, when the construction permit system was begun, the TACB and the TNRCC have issued tens of thousands of permits for new or modified industrial facilities. During the same period, those agencies denied permit applications for a very small number of proposed operations. The minimal number of permit denials that occurred generally resulted from considerations other than health effects concerns.

Fidelity
To be consistent with the ethical concept of fidelity requires faithfulness and the keeping of promises. Implicit in the duties of the TNRCC is the promise that the health and welfare of the public will be given primary consideration in all agency actions. That promise must presuppose that whatever methods are employed in the quest to protect health and welfare will be firmly grounded in valid scientific principles.

The ESL system at the TNRCC is the foundation of the agency's means to protect health and welfare. It is a system that forms the basis for hundreds of decisions each year concerning the kind and quantity of toxic chemicals to which thousands of men, women, and children will be exposed. As explained in the preceding section of this discussion, the ESL procedures are based on discredited, invalid information, false premises, and plain nonsense. As a result, the promise of fidelity is breached, and this ethical principle is not met.

Veracity
Veracity is the simplest ethical principle to articulate and to understand. To practice veracity is to tell the truth, to be candid, to be open and honest. The practice of veracity is the opposite of lying, hypocrisy, and prevarication.

The health effects review system at the TNRCC is not based on veracity. In the strictest sense, the TNRCC doesn't often lie about the health effects review system. But the agency often fails to tell the whole truth. The use of TLVs to assess the impact of toxic chemical exposures on community health is at best a questionable methodology. The use of pseudo-TLVs for the same purpose is not questionable methodology, it is plainly grasping at straws in the name of economic development. It is one thing to conduct a regulatory policy for that purpose, it is quite another to pretend that you don't. The pretense creates a condition of a falsehood. The ESL system is therefore unethical in light of the principle of veracity.

CONCLUSION

TLVs were developed for use in controlling health hazards in an industrial setting. They were not intended to be used in evaluating the potential harm of toxic chemical emissions in neighborhoods surrounding industrial facilities. There are reasons to doubt that TLVs are valid for any human health effects evaluation. In spite of those difficulties, the use of TLVs in air pollution control agencies has become widespread.

The TNRCC relies heavily upon air pollution evaluations based on TLVs. As implemented, the system works primarily for the benefit of the agency, and to some extent, for the benefit of the corporations that the agency regulates. The TNRCC can point to a "health effects review system" and make exaggerated claims about its effectiveness. The corporations can receive permits to emit toxic chemicals into the atmosphere and continue business as usual. In the meantime, the public is left to suffer the unknown consequences of a scientifically meaningless, bureaucratic endeavor.

One consequence of this unethical behavior needs to be emphasized. The potential for harm done by the actions of the TNRCC in the realm of health effects review is magnified by the fact that many of the communities that are subjected to the toxic chemical emissions thus allowed are populated by low-income, relatively uneducated people. That segment of our society often lacks the expertise to understand what is happening as a result of the decisions made by the TNRCC. They are therefore unable to protect themselves and their families.

NOTES:

* Reprinted with permission of the author from Sacrificing Science for Convenience: A Technical and Ethical Evaluation of Texas' Risk Assessment Process for Air Toxics. Downwinders at Risk Education Fund, Cedar Hill, Texas, October 1996.

1. Carson RL: Silent Spring. Houghton Mifflin Company, Boston, Massachusetts, 1962.
2. Degler SE. State Air Pollution Control Laws, Revised Edition: 1. The Bureau of National Affairs, Inc., Washington, DC, 1970.
3. Ibid.
4. Ziem GE and Castleman BI: Threshold limit values: Historical perspective and current practice. Journal of Occupational Medicine 31(11):910, 1989.
5. Ibid.
6. Castleman BI and Ziem GE: Corporate influence on threshold limit values. American Journal of Industrial Medicine 13:531, 1988.
7. Ziem and Castleman, 1989.
8. Robinson JC, Paxman DG, Rappaport SM: Implications of OSHA's reliance on TLVs in developing the Air Contaminants Standard. American Journal of Industrial Medicine 19:3, 1991.
9. Roach SA, Rappaport SM: But they are not thresholds: A critical analysis of the documentation of threshold limit values. American Journal of Industrial Medicine 17:727, 1990.
10. Goldsmith JR: Perspectives on what we formerly called threshold limit values. American Journal of Industrial Medicine 19:805, 1991.
11. Threshold Limit Values for Chemical Substances in the Work Environment, 2. American Conference of Governmental Industrial Hygenists, Cincinnati, Ohio, 1994.
12. Robinson JC, Paxman DG: The role of threshold limit values in US air pollution policy. American Journal of Industrial Medicine 21:383, 1992.
13. NATICH Data Base Report on State, Local, and EPA Air Toxic Activities, 3-2 through 3-5. US Environmental Protection Agency, Research Triangle Park, North Carolina, 1989.
14. Dydek ST, Wiersema J, Price JH: Risk assessment in health effects review of air permits in Texas. Proceedings of the Air Pollution Control Association Annual Meeting, 85-34.3. Pittsburgh, Pennsylvania 1985.
15. Price JH, Wiersema J, Dydek T, Henry JP: Texas procedure for assessing air toxics. Symposium on Setting Air Toxics Standards. Lone Star Chapter of the Society for Risk Analysis, Houston, Texas, 1987.
16. Ibid.
17. Dydek et al., 1985.
18. Price et al., 1987.
19. Ibid.
20. Price JH, Wiersema JM, Dydek ST, Rogers B: New source review in Texas for noncriteria air contaminant impacts. Proceedings of the Air Pollution Control Association Annual Meeting, 85-63.5. Pittsburgh, Pennsylvania, 1985.
21. Price et al., 1987.
22. Ibid.
23. Toxicology and Risk Assessment Section Staff: Effects Screening Levels (ESLs) List. Texas Natural Resource Conservation Commission, Austin, Texas, 1994. See also "Resources" section of this report for revised list.
24. Toxicology and Risk Assessment Section Staff: Effects Evaluation Procedure. Texas Natural Resource Conservation Commission, Austin, Texas, 1994.
25. Price et al., 1985.
26. Dydek et al., 1985.
27. Wiersema JM: [Personal communication.] Texas Air Control Board, Austin, Texas, 1989.
28. Toxicology and Risk Assessment Staff Effects Evaluation Procedure, 1994.
29. Soskolne CL: Rationalizing professional conduct: Ethics in disease control. Public Health Review 19:311, 1991/92.