Selection of Least Hazardous Material Alternatives

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Alvin F. Meyer

A. F. Meyer and Associates, Inc.

McLean, Virginia


A. Summary

This chapter addresses the underlying purposes of accomplishing measures to select the least hazardous of alternative materials used or planned for use by industrial and governmental entities. It then discusses the relationship of substitution processes to other considerations in the decision process. An overview of some approaches for selection methods is presented. A "methodology" originally developed for the U.S. Navy is described, along with examples.

B. Substitution Methods as an Element of Pollution Prevention

1. Substitution vs. Controls

A longstanding principle of environmental control and industrial hygiene is that the first and basic consideration in control of hazards is the elimination of the hazardous component, or if that is not feasible, then the substitution of a lesser hazard [1], The concept of eliminating the source or reducing the amount of toxic materials includes in addition to substitution of materials such other measures as process or operational changes, proper design of operations, and housekeeping. The importance of eliminating the need for costly environmental control measures by substituting less dangerous or less offensive materials also is of longstanding recognition[2]. Likewise, the economic advantages of industrial waste recovery is not a new concept.

Nonetheless the primary approach to environmental control, until the late 1980s, was that of using "end of the pipe" control measures. This was primarily in response to the focus of environmental regulations specifying limits to be met by treatment or other control measures.

In the early 1990s there emerged a steady increase in recognition both in regulatory agencies [e.g., U.S. Environmental Protection Agency (EPA), the Department of Defense] and in the private sector that a comprehensive, cost-effective approach to environmental quality in-

eludes source reduction, recovery, and reutilization, with treatment and ultimate disposal as the last resort. The Pollution Prevention Act of 1990 established these concepts in a national policy that "pollution should be prevented or reduced at the source whenever feasible."

II. HAZARDOUS MATERIAL SUBSTITUTION ACTION A. Statutory and Regulatory Requirements

There are many statutory and regulatory requirements that directly or indirectly create the need for hazardous material assessment. These include federal statutes and their implementing regulations or standards, executive orders requiring federal agency compliance, and state and local codes, standards, and regulations. The Department of Defense (DOD) and the military departments and agencies have requirements that implement the federal mandates and some requirements that predate them.

1. Federal Codes, Standards, and Regulations

The primary federal statutes and their implementing regulations regarding environment, safety, and health are the Clean Air Act, Resource Conservation and Recovery Act (RCRA), Clean Water Act, Safe Drinking Water Act, Toxic Substances Control Act (TSCA), Emergency Planning and Community Right to Know Act (EPCRA), Pollution Prevention Act of 1990, Occupational Safety and Health Act (OSHA), Hazardous Materials Transportation Act, and the National Environmental Policy Act (NEPA). These acts taken together impose a need to examine the feasibility of using materials that are less hazardous, are less costly, or impose fewer administrative or other regulatory compliance resource requirements.

2. Possible Application of Department of Defense Methodologies

A Risk Assessment Code (R AC) procedure was developed by the Department of Defense in the early 1960s [3], Initially, it was designed to provide a means of ranking hazards associated with new weapon systems. Subsequently, the procedure was adapted in 1981 to rate occupational safety and health deficiencies.

In its simplest form, the procedure provides a rating scheme based on a matrix to estimate the severity of effects of the hazard and the probability of occurrence, with the results stated as a risk assessment code. The range is from RAC 1 (catastrophic impact) to RAC 5 (negligible) (see Table 1). The later (1981) procedure, which is still in use, includes a cost effectiveness index and an abatement priority ranking.

The revised procedure takes into account, with a numerical algorithm, such circumstances of exposure and resultant effects as the OSHA Permissible Exposure Limits (PEL), number of employees involved, effects of exposure (ranging from death to minimal lost time, disease, or injury), and duration of exposure. It is firmly established in the military services procedures for evaluating and prioritizing occupational safety and health hazard abatement requirements.

The RAC schemes deal primarily with chemical and safety hazards ratings, with no consideration for environmental ramifications. Recently there has been an increased focus on the environmental aspect of hazardous materials use on the decision-making process. Unlike the long history of chemical and safety hazards rating schemes, there are no universally accepted systems for environmental hazards and risk acceptance. One possible method is a European model, described below.

3. A European Method for Priority Selections and Risk Assessment

A study requested by the European Community Commission to provide a practical approach for priority setting among existing chemicals was prepared by Sampaolo and Binetti [4]. Using this

Least Hazardous Material Alternatives Table 1 Risk Assessment Code Rating Scheme3

Hazard Severity (HHSC)

Mishap probability (MPC)

"Interpretation of HM selection Risk Assessment Code: RAC 1 = high risk (imminent danger of life or property; possible civil or criminal action)

RAC 2 = serious risk (may result in severe injury or illness on or off site, potential for major damage to environment, and resulting notice of violation)

RAC 3 = moderate risk (may cause few illnesses or injuries or significant property damage or environmental impact on or off site) RAC 4 = low risk (can result in only minor impact on or off site or only violation of a standard without damage) RAC 5 = negligible (insignificant impact)

model, an individual property or a number of properties of a given chemical can be evaluated and then ranked with those of other substances. This flexibility allows for evaluating different relationships. For example, one might want to compare only the intrinsic properties with respect to direct personal exposure in a particular circumstance or with respect to environmental exposure. Certain chemicals might have different relative rankings for these two categories. This model offers a number of advantages: The system is simple and flexible enough to be adapted to different and specific needs (i.e., personal exposure to general exposure, risk from domestic exposure vs. professional exposure, etc.). It is a self-improving system because new information can be input and the result can be refined further. This model uses three sets of parameters to evaluate risk and the priority of a given chemical: assessment of intrinsic properties, risk assessment or potentiality, and priority assessment.

Intrinsic Properties. Intrinsic properties of a substance are based on the set of physicochem-ical, toxicological, and ecotoxicological properties that are considered fundamental (or intrinsic) to the first evaluation of the substance. Each element of the intrinsic property (e.g., molecular weight under the physicochemical category) is assigned a numerical value that corresponds to its level of danger. From this information a score is developed for each intrinsic property, which also addresses the availability or nonavailability of the data. These intrinsic properties are considered additive and determine the intrinsic danger of the substance independently of external agents or factors that may influence it.

External Factors. Risk assessment or potentiality includes not only the intrinsic danger of a substance but also the external factors that can influence the danger. These external factors include the quantity of the substance on the market, the plurality of possible exposures, and the size of the risk population. As an example, a substance may be highly dangerous, but if it is not on the market it will not pose any effective risk, and thus its intrinsic risk will be minimal.

Priority Measurement. Priority assessment involves both the known or presumed danger of the chemical and the degree of the lack of knowledge of the substance's properties. A priority measurement can be made by calculating the ratio of the weighted figures for properties without data to those figures with available data. Both the risk assessment and priority assessment parameters can affect the intrinsic properties of a substance by multiplying or canceling them.


Regardless of the methodology used in rating hazardous properties of a material, the selection process for the "least hazardous" involves more than environmental, safety, and health considerations. In addition to assessments to determine the least harmful material based on a hazard assessment (such as the algorithm described later in this chapter), there are major considerations that must be carefully assessed.

1. Basic Feasibility and Engineering Considerations

A fundamental question that should be addressed is: Does the substitute perform adequately for its intended use? This requires determination of the following:

1. "Favorable" vs. "adverse" effects on required performance of the material(s) in production, operations, and maintenance situations.

2. Creation of new or different hazards (such as substitution of a less toxic material with a fire hazard potential for one that is highly toxic but has a low hazard or no hazard).

3. Durability and life cycle times to failure (as with a low volatile organic compound (VOC) paint that may or may not last as long in a very hot or very cold climate).

4. Maintainability of equipment involved in using a substitute.

5. Possible process or equipment changes that may be needed.

6. Environmental and/or OSHA controls required even if it is the lesser hazard.

2. Life Cycle Cost Considerations

There are costs and benefits associated with the engineering and feasibility considerations that need to be assessed. In addition, there are many other costs associated with the life cycle of hazardous material. That life cycle extends from the time of concept through procurement, storage, use, and disposal. It is beyond the scope of this chapter to do more than highlight such costs. It is also beyond its scope to describe the economic analyses required to evaluate the relative costs and benefits of two or more candidate materials for selection. Among the many costs that should be taken into account in the selection process are those shown in Table 2. A very useful guide for comparing alternatives is the EPA Pollution Benefits Manual [5].

The EPA Pollution Benefits Manual provides for a financial analysis approach to compare alternatives for pollution prevention. It involves a four-tier cost analysis from which economy feasibility of alternatives can be evaluated. The four tiers are as follows:

Tier 0, Usual costs. The alternatives are identified, and all normal costs associated with each are determined. These include investment (depreciable capital, expenditures), operating costs, and operating revenues.

Table 2 Life Cycle Hazardous Materials Costs and Cost Avoidance Considerations

Acquisition Supply and storage Use

Waste treatment Other disposal Emission control Inventory control

Engineering/process control/change Training


Hazard/risk assessment



Personal protection Medical monitoring Spill prevention and control Regulatory overhead Liability

Tier 1, Hidden Costs. These include such investments as monitoring equipment, protective equipment, control technology, and operating costs such as reports, monitoring training, and medical costs.

Tier 2, Liability Costs. Included are penalties, fines, and future liabilities. Tier 3, Less Tangible Costs. These include costs such as those associated with labor relations, and public relations.

The results of the tier analyses are then incorporated into cost summaries and financial worksheets, which result in an assessment and/or comparison of any cost savings for each alternative. This procedure allows for comparison of relative costs and benefits of selected alternatives.

B. Management Decisions and Actions for Selection of Least Hazardous Material

1. Driving Forces

The basic driving forces for management to consider in the selection of less hazardous materials, in addition to regulatory requirements, include the life cycle cost considerations discussed above and such needs as planning for new products or processes (or changes to existing ones), avoidance of new and long-term liabilities, and the possible benefits of participation in such voluntary programs as the U.S. EPA Industrial Toxics Project (ITP). Other benefits include improved employee and community relations.

2. "Closing the Loop"

Once decisions are made for substitution, a large number of follow-on actions are needed. These include planning for phase-out of the existing in-use materials, development of new specifications and technical data documents, training of personnel, provision of any necessary controls, and compliance with any new permit or similar requirements.

IV. DESCRIPTION OF METHODOLOGY A. Overview of the Navy Substitution Algorithm

The hazardous material substitution algorithm developed for the U.S. Navy also had wide potential for selection or substitution of least hazardous materials in civilian applications [6].

1. The Navy Model

The hazardous material substitution algorithm is sufficiently flexible that it can either serve as a preliminary screening to identify the most likely candidate for further study or become a part of a much more detailed and sophisticated decision model. In the first instance, the model would be useful to an industrial or commercial concern or to a military installation comparing materials proposed by vendors as substitutes for existing materials not conforming to regulatory requirements. The second application would be for screening as part of an in-depth decision process for changes to production operations, or comparison of newly synthesized materials for possible large-scale application throughout a major industry. For maximum utility, the Navy model is adaptable to either simple manual computations or computer applications.

2. Description of the Algorithm

The algorithm is used to assign numerical "points" for various hazard descriptor elements such as toxicity, duration of personnel exposures, number of persons exposed, related medical effects, fire and explosion potential, requirements for personal protective equipment, and a limited assessment of environmental impact and control requirements. These latter include volatile organic chemicals, EPA Reportable Quantities, and EPA's List of Lists materials (40 CFR 302,4) among others.

The "points" assigned are totals that provide a numerical score and a risk assessment code (RAC). This provides for determination of a hazardous material selection factor (HMSF), which allows for materials to be compared with one another in numerical terms. The result can then be used as an entry point into the foregoing overall decision process.

The input data are readily available. Principal among these are the Material Safety Data Sheets (MSDS) required by 29 CFR 1910.1000, OSHA Permissible Exposure Limits (Table Z 29 CFR 1910.100), and EPA Publication 560/4-90-011 "Title III List of Lists." The RAC procedure is based on a commonly used system safety analysis method (MIL-STD-882), and the basic approach to the "point" algorithm is the previously described DoD system for rating occupational, safety, and health hazards.

B. Understanding the Basis for the "Points"

The following brief information provides an understanding of the basis for selecting the range of numerical values for the algorithm's points.

1. Toxic Effects

The evaluation should include the frequency and duration of possible worker exposure. This includes whether the material presents toxic hazards on brief, short-term exposures associated with high concentrations and accidental releases or primarily causes harm from extended exposure to relatively low concentrations. Materials that are skin irritants or sensitizers or that are suspect or known carcinogens, teratogens, or mutagens require special attention even if the projected quantities are small.

In many instances, the MSDS will only summarize the toxicity data of the individual components of the mixture and will not provide information concerning specific toxicological studies on the material itself. In such cases, judgments will have to be based on consultation with such approved sources as the Navy Environmental Health Center. Attention also must be given to any information indicating that the material is a known skin sensitizer or possesses allergenic properties. A suggested source of reference regarding toxic hazards is the National Institute of Occupational Safety and Health (NIOSH) Pocket Guide to Chemical Hazards available from the U.S. Government Printing Office.

2. Characteristics

Physical Characteristics. Materials with a high vapor pressure are more likely to be easily dispersed into the environment than those with lower vapor pressures. Those with low flash point and low boiling point (flash point lower than 73°F and boiling point below 100°F) are extremely hazardous from a fire and explosion viewpoint compared with those with flash points greater than 100°F. Liquids with specific gravities less than 1.0 present fire-spreading hazards because such materials float on water. A "toxic material" with a high vapor pressure is more of a hazard in a confined work area than one with the same toxic properties but a much lower vapor pressure. This is because the higher vapor pressure will afford a greater risk of room atmospheric contamination.

Chemical Characteristics. Where mixtures are involved, it is important to understand that those that include aromatic organic chemicals are generally more toxic (and often pose greater fire and explosion hazards) than those classed as aliphatic chemicals. Among the chemical characteristics that must be considered are stability, reactivity with other chemicals (for example, is the material an oxidizer or corrosive?), and solubility, not only in water but in other media.

Circumstances of Exposure. In addition to the specifics of probable work areas, questions on the distribution of material throughout the weapon system life cycle or on-shore activity need to be considered. Localized use (in a single work area) of a material determined to be highly hazardous presents a different set of concerns with respect to approval decisions than those that apply to a material with moderate hazard potential that is widely used. Among the considerations that should be examined are size of the work force or number of persons at a work site, present and/or needed engineering or other controls, and work area environmental conditions that affect the hazard (temperature, humidity, the presence of other chemicals that may be synergistic or additive, etc.). During a general review and evaluation of a proposed material, questions need to be examined with respect to the interaction of the proposed material with others already approved and its use in the system or work areas and with nearby operations. For example, it would be a mistake to approve a new cleaning solvent with a high vapor pressure and low flash point for use in shops in which arc welding is conducted.

Environmental Implications. The potential for hazardous waste (HW) generation and compliance with various federal, state, and local codes, standards, and regulations must be evaluated. In some geographical areas, regulations on use and/or release of volatile organic compound air pollutants are very severe and may require special controls if a material is approved. Similar concerns must be examined with regard to air quality and water permits. Because of the wide variety of such requirements, the "points" used in this method are simplified. More detailed ratings may have to be developed by the user for some analyses.


The hazardous material substitution algorithm developed for the U.S. Navy has been tested extensively and found to be a useful first screening tool. It also fills the need for a wide variety of applications in the civil sector. As indicated earlier in this chapter, it is only one element of the decision process.

It is also essential to note that although one goal may be the elimination of hazardous materials that affect people or the environment, in many instances complete elimination is not feasible. The selection method, and other considerations in the decision process, provide for a rational and cost-effective determination of the most suitable material. As stated by EPA (Pollution Prevention 1991, EPA 21P-3003) and the Pollution Prevention Act of 1990, when pollution cannot be prevented, reduced at the source, or recycled, it "should be treated in an environmentally safe manner . . . and disposal or other release to the environment should be employed only as a last resort and should be conducted in an environmentally safe manner."


This chapter is based in part on AFMA-TR-91001, Development of Guidance for Selection/ Substitution of Less Hazardous Materials, for the U.S. Naval Supply Systems Command, under USAF contract F33615 89-D-4003, Order 16, A. F. Meyer and Associates, Inc. with Engineering-Science, Inc. Publication rights to this chapter are retained by the U.S. Government. Copies of the basic technical report can be obtained from Defense Technical Information Center.


1. Patty, F. T., Industrial Hygiene Toxicology, Vol. 1, Inter-Science Publishing Co., Chicago, 1948.

2. Meyer, A. F., Jr., Engineering biotechnology in occupational health, Trans. Am. Soc. Civil Eng., 121: Paper No. 2798 (1956).

3. U.S. Department of Defense, Department of Defense Occupational Safety and Health (OSH) Programs, DODI 6055.1 A, 9 Sep 87.

4. Sampaolo, A., and Binetti, R., Regulatory Toxicology and Pharmacology, Vol. 6, 1986.

5. U.S. Environmental Protection Agency, Pollution Benefits Manual, October 1989.

6. U.S. Navy, Naval Supply Systems Command, Development of guidance for selection substitution of less hazardous materials, Tech. Rep. AFMA-TR-91001, 1992.

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