Hierarchy of Controls Contents

9 Hierarchy of Controls Contents

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b. . . Hierarchy of Controls

As explained in chapter 5, a generalized model tive equipment, work practices, and administra- of the workplace environment looks at sources tive procedures (see discussions in chs. 5 and 8). of hazards, transmission of the hazard, and work- This model can also be applied to injury haz- ers (see fig. 5-2 in ch. 5). Health and safety hazards are controlled by interrupting the transmission of ards, although much of the safety research published to date has followed other approaches. For hazardous agents to workers. Controls can be intro- example, control of electrical energy at the source duced at several points: the source of the hazard, might involve grounding to prevent the buildup the workplace atmosphere (or transmission points), and inappropriate release of hazardous amounts and the workers’ location(s). For health hazards, of energy. Control of transmission could include control at the source can include substitution of separating workers from the hazard by, for exam- less toxic agents or substances, as well as process ple, placing physical barriers or guards between and engineering changes to reduce emissions of the worker and the hazard, Personal protective the hazardous agents or substances. Control of equipment, such as insulated gloves, represents transmission of the agent can be accomplished by a control applied on the worker. ventilation, isolation, dilution, or enclosure. Con- trol at the worker can include personal protec-

DESCRIPTION OF HIERARCHY OF CONTROLS Health and safety professionals have tradi- cluded and generally constitute the “third” line of tionally ranked controls according to their relia- defense, falling after engineering controls and bility and efficacy in removing or controlling haz- work practice controls and ahead of protective ards. Put simply, the principle of the hierarchy equipment. For some hazards, however, the Oc- of controls is to control the hazard as close to the cupational Safety and Health Administration source as possible. (This hierarchical approach is (OSHA) places administrative controls on an most commonly discussed in relation to health equal basis with engineering controls. In addition, hazards and the methods of industrial hygiene. OSHA now usually groups engineering controls Although the principle can also be applied to safe- and work practices together and assigns them the ty hazards, most of the discussion in this chapter same priority. Nevertheless, in all cases, personal will focus on the control of health hazards. ) protective equipment is listed as the control of last resort. Expressed differently, the hierarchy of controls describes the order that either should be followed or must be followed when choosing among op- Views of Health Professionals tions for controlling health and safety hazards. In its simplest form, the hierarchy of controls The hierarchy of controls is widely supported specifies that engineering controls (including sub- in the professional community. Every current in- stitution, enclosure, isolation and ventilation) are dustrial hygiene textbook endorses the idea of preferred to the use of personal protective equip- such a hierarchy and lists engineering controls as ment. Work practices are frequently added to this the first priority and personal protective equip- list between engineering controls and personal ment as a last resort (455). It is often expressed protective equipment. Administrative controls, in the context of controlling exposures to airborne such as worker rotation, are also oftentimes in- contaminants-fumes, dusts, and vapors-that

175 176 ● Preventing Illness and Injury in the Workplace

may enter the worker’s respiratory system. Elim- Consensus Standards ination of the contaminants by substitution of materials, enclosure of operations that generate The hierarchy of controls is also found in the fumes and vapors, dust suppression methods, or “consensus” standards written by committees dilution of the contaminants by ventilation are meeting under the auspices of the American Na- all preferred over reliance on respirators. Leaders tional Standards Institute (ANSI) and its prede- in this field and industrial hygiene texts all agree cessor, the American Standards Association. The on this point (129,173,199,362,369,423). Association’s 1938 standard for protective equipment did not require any particular “hierarchy of Excerpts from a 1947 textbook on industrial hy- controls, ” but the attached commentary noted: giene and from a 1980s text underline the un- changing preference for engineering controls. It is obviously better to remove the hazard, when this is possible, than to protect the worker Obviously, the most successful approach to the against it [using personal protective equipment]. problem of industrial atmospheric sanitation lies Thus, in granite cutting it is preferable to remove in the design or alteration of plant and equipment the dust by an exhaust system rather than to allow so that the control features are engineered into the it to contaminate the air, and then to protect the structure and machinery (71, emphasis in original). worker against breathing the dust. . . . This code In many instances, however, the reduction of ex- does not attempt to specify how various indus- posure [through engineering methods] is not suffi- tries shall be conducted, with respect to avoiding cient to eliminate the hazard, and other control hazards, but points out the method of protecting measures are needed. . , . Respiratory protective de- the worker where the hazard has not been elimi- vices have a distinct place in the field of industrial nated by other means (15). health engineering. That they are a last Zinc of de- In the 1959 revision of this consensus standard, fense can hardly be denied (71, emphasis added). respirators were assigned a supplemental function The newer text states: in the actual text of the standard: If confinement or removal by adequate proper- General Considerations. Respirators are used ly engineered and operated ventilation systems is to supplement other methods of control of air- not possible, personal protective equipment on a borne contaminants rather than to substitute for temporary basis should be considered. We stress them. Every effort should be made to prevent the the word “temporary” since respiratory protec- dissemination of contaminants into the breathing tion can seldom be relied on for long periods of zones of the workers. In some instances, it is nec- time in hazardous exposures, unless highly unu- essary to use respirators only until these control sual control procedures are established and rig- measures have been taken; in others, such meas- orously enforced (172). ures are impracticable, and the continued use of respirators is necessary (16). In 1963, the American Conference of Govern- mental Industrial Hygienists (ACGIH) and the In 1969, ANSI issued a separate standard for American Industrial Hygiene Association jointly respiratory protection. The heading of the para- issued a comprehensive guide to respiratory pro- graph that describes the applicable principles was tection in the United States. The opening para- changed from “General Considerations” to “Per- graph is clear on the preferred methods of con- missible Practice,” adding weight to the impor- trolling occupational hazards: tance of the control hierarchy. In addition, emphasis was given to what was now viewed as the In the control of those occupational diseases “primary objective” of workplace controls: pre- caused by breathing air contaminated with harm- venting the contamination of the workplace at- ful dusts, fumes, mists, gases, or vapors, the pri- mosphere. In addition the word “feasible” was mary objective should be to prevent the air from used in connection with controls. becoming contaminated. This is accomplished as far as possible by accepted engineering control Permissible Practice. In the control of those oc- measures; . . . (9). cupational diseases caused by breathing air con- . .——. ...—

Ch. 9—Hierarchy of Controls ● 177

taminated with harmful dusts, fogs, fumes, mists, other protective measures shall be used to keep gases, smokes, sprays, or vapors, the primary ob- the exposure of employees to air contaminants jective shall be to prevent atmospheric contamina- within the limits prescribed . . . Any equipment tion. This shall be accomplished as far as feasible and/or technical measures used for this purpose by accepted engineering control measures (for ex- must be approved for each particular use by a ample, enclosure or confinement of the operation, competent industrial hygienist or other technically general and local ventilation, and substitution of qualified person. Whenever respirators are used, less toxic materials). When effective engineering their use shall comply with section 1910.134 [the controls are not feasible, or while they are being OSHA respirator standard] (29 CFR 1910.1000 instituted, appropriate respirators shall be used (e), emphasis added). . . . (11, emphasis in original). In addition, in all of its substance-specific pro- The 1980 revision of this ANSI standard is vir- ceedings that resulted in new or revised permissi- tually identical in wording, although the phrase ble exposure limits, OSHA has maintained a pol- beginning with “the primary objective” is no icy of first requiring employers to comply by longer underscored. In addition, respirators are implementing “feasible” engineering and work now permitted “[w]hen effective engineering con- practice controls. Although the precise wording trols are not feasible, or while they are being in- of these requirements has differed slightly among stituted or evaluated . . . “ (12, emphasis added). these health standards, the basic outline is clear: First, an employer must institute feasible engi- Government Standards neering and work practice controls to reduce em- The conclusions and practices of the profession- loyee exposures to or below the permissible exposure limit. al community and the consensus standards orga- nizations now have regulatory force. The startup Second, even if the feasible engineering and standards adopted by OSHA in 1971 under the work practice controls are insufficient to achieve compliance with the permissible limit, the em- authority of section 6(a) of the Occupational ployer is required to use them in order to reduce Safety and Health (OSH) Act (see ch. 12) included exposures as low as possible before issuing per- three specific provisions concerning the hierarchy sonal protective equipment. of controls. Personal protective equipment, such as dust The applicable paragraph in OSHA’s standard masks, gas masks, and other types of respirators, concerning respiratory protection (29 CFR 1910.134 is to be used against airborne contaminants in (a)(l)) was taken, word for word, from the paragraph only four circumstances: in the 1969 ANSI standard quoted above, although the ● one phrase underscored in the ANSI standard is not during the time period necessary to install underscored in the OSHA standard. Second, the feasible engineering and work practice OSHA noise standard requires employers to com- controls, ● ply with the permissible exposure limit through when engineering and work practice controls the use of “feasible administrative or engineering are not feasible (including many repair and controls” (29 CFR 1910.95(b)(l)). maintenance activities), ● when engineering and work practice controls Finally, OSHA’s main requirement for limiting ex- are not sufficient to achieve compliance with posures to toxic substances (the Air Contaminants the permissible limits, and standard) reads: ● in emergencies. To achieve compliance with . , , this section, administrative or engineering control must first Controls for Safety Hazards be determined and implemented whenever feasible. When such controls are not feasible to achieve A similar priority system has been suggested full compliance, protective equipment or any for the control of injury hazards. A clear exam-

178 ● Preventing Illness and Injury in the Workplace

ple can be found in the National Safety Council’s Accident Prevention Manual (322), which lists the following “hierarchy”: The basic measures for preventing accidental injury, in order of effectiveness and preference are: 1. Eliminate the hazard from the machine, method, material, or plant structure. 2. Control the hazard by enclosing or guarding it at its source. 3. Train personnel to be aware of the hazard and to follow safe job procedures to avoid it. 4. Prescribe Personal protective equipment for personnel to shield-them against the hazard. Discussions about the hierarchy of controls in these situations is often concerned with the relative priorities to be placed on workplace and machinery design as opposed to worker training. Em- ployee training and education will always be an important adjunct to any control technique. But ergonomics and safety research now stress the im- portance of design over primary reliance on the inculcation of certain “safe” work routines through training. (See also discussions of safety hazard identification, injury controls, ergonomics, and worker training in chs. 4,6,7, and 10).

Photo credit: NIOSH (photo provided by OSHA, Office of Information and Consumer Affairs Because respirators increase the effort required for breathing and are uncomfortable, workers often do not wear them or wear them only intermittently. Engineering cent rots can often eliminate the need to use respirators

ADVANTAGES AND DISADVANTAGES OF THE HIERARCHY OF CONTROLS The preference for engineering methods for con- professionals, the National Institute for Occupa- trolling workplace hazards is sometimes ques- tional Safety and Health (NIOSH), and OSHA tioned. Why are engineering controls preferred assigned personal protective equipment to the and why is personal protective equipment ranked position of being only a ‘last line of defense”? The lower than other methods? Why have nearly all reasons can be divided into those that deal with .

Ch. 9—Hierarchy of Controls ● 179 specific, often technical, problems of currently available personal protective equipment and those that address more general advantages of engineering controls.

Problems with Personal Protective Equipment

Many types of existing personal protective equipment do not provide reliable, consistent, and adequate levels of protection. Indeed, research conducted on the real-world or workplace, as opposed to laboratory, effectiveness of such equipment shows that the protection provided by these devices is unequal, highly variable, and substan- tially lower than that predicted from laboratory measurements (see ch. 8). For example, it has been estimated that the mean real-world attenuation of hearing protectors is only about one-third their laboratory attenuation (49). These shortcomings often make personal protective equipment inade- those at the source of a hazard, can simultane- quate for worker protection. ously control several exposure routes, such as respiratory and dermal exposure, while protective Advantages of Engineering Controls equipment is generally limited to protecting only one exposure route. The problems specific to personal protective In addition, OTA has identified five other areas equipment are sufficient to cause professionals to for which engineering controls have advantages rank engineering controls above them in the hier- over personal protective equipment. First, many archy of controls. Additionally, engineering controls have a number of advantages ranging from employer-provided personal protective programs the relatively mundane and pragmatic to the more are currently inadequate. Most discussions of the philosophical. relative merits of engineering controls and personal protective equipment center on respiratory In brief, engineering controls are inherently hazards. For those hazards, it is argued that res- more reliable and provide more effective protec- pirator programs can be designed and imple- tion than personal protective equipment and are mented to provide protection equal to that af- more likely to result in successful hazard control forded by engineering controls. Successful control (see box G). Once installed and adequately main- through the use of respirators has sometimes been tained, engineering controls provide reliable and achieved by a few, usually large, employers who consistent performance, and, if designed correctly, have sophisticated health and safety programs. adequate levels of protection. But not all employers have implemented such programs or are capable of doing so. Engineering controls work day after day, hour after hour, without depending on human super- Indeed, failures in employer respirator pro- vision or intervention. Because they do not de- grams are the most frequent cause of OSHA cita- pend on a “good fit” with workers, they provide tions in health inspections, reinforcing the experi- the same protection to all, and monitoring devices ence of many industrial hygienists and OSHA can measure the protection afforded. Separated inspectors that most existing respirator programs from contact with the worker, engineering con- are inadequate. More than one-third of all OSHA trols do not create additional health or safety citations for violations of health standards in- problems, Moreover, these controls, especially volved the respirator program requirements, 180 . Preventing Illness and Injury in the Workplace which were directly adopted from the 1969 ANSI ogy-forcing” controls (see ch. 14). New control consensus standard (180). technology can be, and has been, accompanied by other changes in plant and equipment that im- Former OSHA inspectors have written that, in prove productivity, as well as protecting worker their experience, for most cases of employee over- health and safety (see ch. 16). Relying on personal exposure to air contaminants the employers’ res- protective equipment would reduce technologi- pirator programs were inadequate (329,363). This cal development—including the development of is supported by analysis of OSHA inspection data. controls that may find application to other OSHA inspectors cite violations of the respira- hazards, as well as improvements in equipment tor program requirements in 40 to 70 percent of that reduce hazards and simultaneously raise pro- the inspections in which employee overexposure ductivity. For example, if OSHA had permitted was measured (402). A leading consultant in the the use of dust masks to comply with the cotton field has summarized his experience: dust standard, the installation of new technology having reviewed the respirator programs of in the cotton textile industry would probably not hundreds of private companies, I can state that have taken place as rapidly as it did. Modernized I have not, with the exception of the nation’s very equipment has both dramatically improved pro- largest corporations, ever observed a proper and ductivity and lowered worker exposures to cot- adequate use of respirators in the occupational ton dust (413). setting (309). Second, it is generally impossible to make peri- Finally, personal protective equipment is bur- odic measurements of respirator efficiency, and densome on employees. It is usually uncomfortable, it is very difficult to monitor each individual em- decreases mobility, and the weight of many types ployee as he/she cleans, dons, and uses his/her of personal protective equipment increases em- respirator. Moreover, it is probably human nature ployees’ physical work loads. Negative-pressure to be on one’s “best behavior” when someone is respirators, in addition to their discomfort, also “watching. ” It is therefore difficult to be certain significantly increase the effort needed for breath- that the use of equipment observed by a respira- ing. This can create special difficulties for work- tor program manager is representative of regular ers who have already suffered lung impairments. use. Similarly, it is much more difficult for OSHA Moreover, this equipment often impairs produc- to monitor the use of masks and respirators dur- tivity. In many cases workers are paid on a “piece- ing an inspection, which are conducted infre- work” basis or are evaluated on how well they meet quently, and to be certain that the use observed employer-set productivity standards. If allowance then is representative of use on other days. is not made for the decrease in productivity due to Third, in a hierarchical approach, with control the use of protective equipment, an economic bur- achieved close to the source of the hazard, there den may be borne by the employee. is room for backup or supplemental controls. For The use of such equipment, especially respirators, example, if the primary control involves the use also impairs communication and worker-to-worker of process containment (“control at the source”), contact. This may lead to additional safety prob- then this control can be supplemented by having lems because employees wearing respirators will be personal protective equipment available (“control unable to warn each other of potential safety haz- at the worker”) for emergency use. If the primary ards, while those wearing hearing protection may control is protective equipment, the opportunity be unable to hear instructions, warning signals, or to provide for supplemental control is eliminated changes in the operations of plant equipment. (How- because the control selected is already “at the ever, one study has found decreases in accidents worker”; that is, the last line of defense has after implementation of a hearing conservation pro- already been used. gram (622).) In addition, reducing worker-to-worker Fourth, primary reliance on engineering con- communication can increase a person’s sense of trols can spur the advance of technology. The isolation and detract from the important social func- OSH Act allows the agency to mandate “technol- tions of work.

Ch. 9—Hierarchy of Controls ● 181

Lastly, workers required to use personal protective equipment may feel that they are no longer being treated as persons, especially if they are not allowed to participate in any decisions concerning the use of equipment. People in this position may feel that they are merely cogs in the workplace, similar to other machines that require hoods, filters, and masks.

Problems with Engineering Controls

Notwithstanding the advantages of engineering controls over personal protective equipment, there are some drawbacks. First, although they are less subject to human error and inherently more reliable, engineering controls can fail. No matter how well designed, a ventilation system will fail to remove an airborne contaminant if the fan stops. Although these failures can be kept to a minimum with adequate maintenance, respirators must be available for use in such emergencies. Even substitution does not eliminate the possi- bility of a failure in hazard control. For example, carbon tetrachloride, which had been used as a substitute for petroleum naphtha, is now widely recognized as toxic itself. Some of the substitutes for carbon tetrachloride (tricholoroethylene, per- Photo credit OSHA Office of Information and Consumer Affairs chlorethylene) are now suspected of having vari- Engineering controls for occupational noise exposures ous previously unrecognized toxic effects. include the use of sound dampening enclosures Second, there are a number of situations for control techniques or by facilitating dissemina- which feasible control methods have not yet been tion of existing techniques. fully developed. In these situations, the best that can be done is to require the use of personal pro- Cost is the principal objection to requiring engi- tective equipment while attempting to develop neering controls. Although a well-designed and feasible engineering controls. In addition, such well-conducted respirator program can be expen- equipment will always be needed when engineer- sive, such programs are in many cases cheaper ing controls are insufficient to reduce exposures than engineering controls and certainly capital to permissible levels and during the interim period costs are lower. Sometimes the concern about the while engineering controls are being designed and costs of engineering controls arises because of the implemented. belief that these costs would be infeasible for a particular firm (leading to a plant closing) or for These situations are widely recognized and are an industry as a whole. Sometimes arguments are provided for in OSHA’s hierarchy of controls. based on the relative “cost-effectiveness” of There are, and will be, however, disputes about controls. what kinds of controls are “technologically feasible” in any given situation. This is particularly Some employers and economists have suggested true when OSHA issues a regulation that “forces” that employers should be allowed the flexibility technology, either by speeding development of to choose among the available control methods, 182 ● Preventing Illness and Injury in the Workplace

rather than being required first to install feasible ployee protection at reduced cost. This argument engineering controls. This flexibility would allow is used with regard to both full 8-hour exposures employers to choose the least-costly control method. and for brief and intermittent exposures. These industry representatives argue that if the degree For example, in its reconsideration of the lead of protection offered by the equipment is equiva- standard, OSHA estimated the compliance costs lent to that provided by engineering controls, it for a group of industries. If these industries were would be sensible to choose the least costly means. required to use engineering controls, total annual Unfortunately, as already noted, many kinds of Costs were estimated to be nearly $130 million. protective equipment have not been demonstrated But if respirators were allowed, the costs would to be effective in actual workplace conditions. In be about $78 million (626). addition, there may be additional benefits from A second example concerns compliance costs requiring engineering controls, such as increases for reducing asbestos exposures from 2 fibers/ in productivity or relative decreases in absentee- cubic centimeter to 0.5 fiber/cubic centimeter. The ism. These economic benefits need to be consid- total annual costs for all industries, in 1982 ered when judging the “cost-effectiveness” of dif- dollars, are estimated to be about $134 million ferent control techniques. if engineering controls are required and $54 mil- The cost-effectiveness argument is also raised lion if respirators are allowed. If the permissible in connection with the requirement that feasible limit is set still lower, at 0.2 fiber/cubic centi- engineering controls be installed even when engi- meter, the annual costs would be about $170 mil- neering and work practice controls are insufficient lion for engineering controls and $56 million for to achieve compliance. In these situations personal compliance through the use of respirators (647). protective equipment is needed for workers in or- For both examples, there are limitations to the der to meet permitted exposure levels. It is argued accuracy of these estimates. Moreover, in neither that in such cases expenditures for engineering case was OSHA able to estimate the potential re- controls are wasted because personal protective duction in worker productivity due to the in- equipment will still be required. But because per- terference caused by respirators. But, as esti- sonal protective equipment often fails, reducing mated, the cost differences between these control contaminant levels through the use of engineer- methods appear, in many cases, to be substantial. ing controls minimizes the likely degree of worker overexposure. Many employers believe that the use of personal protective equipment can provide adequate em-

OSHA’S POLICY TOWARD THE HIERARCHY OF CONTROLS Since its creation in 1971, OSHA has enforced sonal protective equipment. Many of these same the provisions of the startup standards requiring professionals, and other representatives of em- the use of engineering controls. In addition, OSHA ployers’ and trade associations, would then ex- has developed, through rulemaking proceedings, plain why this general policy did not apply to their new or revised standards covering a number of own workplaces or industries. Representatives toxic substances or hazardous physical agents. from labor unions, public-interest groups, and In these proceedings, nearly every health and Government would carefully argue in reply that the preference for engineering controls was nec- safety professional, irrespective of whether the person worked for an employer, a trade associa- essary to protect employee safety and health. tion, a labor union, a public-interest group, a The requirement that regulatory agencies per- university, or the Government, agreed that engi- form “economic impact assessments” (see ch. 14) neering controls are preferable to the use of per- has resulted in economists becoming directly in- Ch. 9—Hierarchy of Controls ● 183 volved in discussions concerning health standards. NIOSH, in its comments, supported the hierar- The Council on Wage and Price Stability advised chy of controls: OSHA, on a number of occasions, to change its Each element of the hierarchy: 1) preventing policy and allow the use of personal protective emissions at their source, 2) removing the emis- equipment in place of engineering controls. In sions from the pathway between the source and each proceeding on health standards before 1981, the worker, and 3) control at the recipient, should OSHA rejected that advice and continued to re- be applied in descending order to the extent fea- quire engineering controls as the first line of de- sible before the next lower element is applied fense for controlling exposures to air contaminants. (585). Health and safety professionals working for Actions by the Current Administration universities and government agencies supported the preference for engineering controls. The two In February 1983, OSHA published an Advance associations of professional industrial hygienists Notice of Proposed Rulemaking announcing that (the American Conference of Governmental In- it was conducting a review of the hierarchy of con- dustrial Hygienists and the American Industrial trols and requesting information and comments Hygiene Association) supported the concept of from the public. OSHA stated that its objectives first using engineering controls: were to: The elected Board of Directors of the [ACGIH] ● Explore whether a revised policy will allow . . . unanimously endorses continuation of the employers to institute more cost-effective current [OSHA] policy to require employers to compliance strategies. use feasible engineering controls, work practices, ● Investigate whether advances in respirator and administrative controls to prevent employee design, technology, and applications may exposures above permissible levels. Personal protective equipment, including respirators, may be permit increased reliance on respirators. ● used as alternatives only when other methods are Attempt to identify processes, operations, not adequate, are not feasible, or have not yet and circumstances appropriate for particu- been installed. Furthermore, we endorse engineer- lar compliance strategies. ing controls as the preferred approach (125). ● Assess actual workplace conditions and em- The AIHA would like to go on record as stating ployee health in industries and operations that the elimination of workplace hazards is employing different compliance strategies superior to the use of engineering controls, per- (639). sonal protective equipment, and other control strategies. Where elimination is not feasible, engi- During the comment period that followed this neering and other control strategies should be the announcement, OSHA received 132 separate com- primary methods for reducing or eliminating ex- ments from the public, including employers, trade posures in the workplace. However, personal pro- associations, labor unions, and individuals. Em- tective equipment may be necessary pending more ployers and their representatives supported a gen- long-term solutions, We recognize that there are eral change in OSHA’s policy, and asked that the times where personal protective equipment is ul- agency allow the use of respirators to substitute timately the only feasible control. The decision for engineering controls. There were some differ- to recommend engineering controls, personal pro- ences among employers and trade associations tective equipment or other control strategies de- concerning the precise circumstances under which pends on the nature of the hazard in question and such a substitution should be permitted, but should be based upon the professional judgment nearly all were in favor of allowing employers of an industrial hygienist (375). flexibility to choose between engineering controls At this time, OSHA has not yet publicly an- and respirators. Labor unions, on the other hand, nounced what course it will follow concerning the voiced support for the existing policy and objected general hierarchy of controls policy. in light of strongly to any changes. OSHA's reconsideration of the hierarchy of con- 184 . preventing Illness and Injury in the Workplace

trols, the advisory panel for this OTA assessment also concluded that most operations that gener- asked to be recorded as endorsing the hierarchy ated short-term exposures to ethylene oxide could of controls. To turn away from the hierarchy of be controlled with the use of engineering controls. controls without careful verification of the level Thus, the agency did not, as it proposed for ethyl- of protection afforded by personal protective ene dibromide, allow the general use of respira- equipment is likely to increase exposures to health tors for all short-term operations with ethylene hazards. oxide exposures (649). (However, because of objections from OMB, the agency did not issue any In several substance-specific standards, the cur- short-term exposure limit for ethylene oxide, but rent administration has both continued the tradi- requested public comments on the need for such tional policy and proposed changes. In its recon- a limit and the feasibility of a short-term exposure sideration of the cotton dust standard, OSHA limit without the use of respirators.) decided to continue to require engineering controls, even in the face of objections from the Of- In addition, OSHA concluded that for some sit- fice of Management and Budget (OMB). This dis- uations, engineering controls to meet the 8-hour pute between OSHA and OMB was, at least time-weighted average for ethylene oxide were not temporarily, resolved in OSHA’s favor and the feasible and, for the first time in any health stand- published proposal reiterates the hierarchy of con- ard, specifically lists those operations in the text trols (641). of the regulation. For those situations, employers However, in a proposal concerning a new are allowed to issue respirators as the primary standard for ethylene dibromide (EDB), OSHA means of control (649). proposed for the first time to make an important Moreover, the current administration has also exception to the traditional hierarchy of controls, issued an administrative directive to OSHA in- although this exception would be limited to cases spectors, ordering that no citations concerning of intermittent exposure. The agency’s proposal OSHA’s permissible exposure limit for noise be would allow employers to use respirators as the issued to employers who had issued and required primary means of control “where exposure to EDB the use of hearing protectors by employees ex- . . . is intermittent [defined as an operation that posed to levels up to 10 decibels (dB) above the results in exposures occurring for 1 or 2 days at permissible limit (that is, exposures between 90 any one time] and occurs less than a total of 30 dB to 100 dB) (646). Because of the logarithmic days per year” (642). nature of the decibel scale, this difference of 10 In its 1984 proposal for a new asbestos stand- decibels is equal to a tenfold increase in permissi- ard, the agency proposed that employers be al- ble exposures. One researcher has estimated that lowed to use respirators on a continuous basis as using hearing protectors instead of engineering the primary means to comply with a new, reduced controls for noise exposures between 90 dB and exposure limit. Employers would still be required 100 dB will double the probability that an exposed to use feasible engineering and work practice con- worker will incur an occupational hearing loss trols to meet the current existing limit (2 fibers/ (165). cubic centimeter). But they would be allowed to Finally, OSHA first granted and then withdrew use personal protective equipment on a continu- an experimental variance from the medical remov- ous basis to reduce exposures from the 2 fibers/ al protection provisions of the lead standard. The cubic centimeter limit to the new permissible ex- lead standard requires that employees whose posure limit (either 0.5 or 0.2 fibers/cubic centi- blood lead levels exceed certain specified limits meter) (647). must be transferred to jobs with little or no ex- In its 1984 final rule reducing the permissible posure to lead. The variance would have allowed exposure limit (measured as an 8-hour time-weighted one employer to issue respirators to several em- average) for ethylene oxide exposures, OSHA re- ployees with blood lead levels above the permitted quires employers to comply with the new permis- limits, who would then continue in lead-exposed sible exposure limit through the use of feasible jobs instead of being transferred to positions with- engineering and work practice controls. OSHA out lead exposures (243,338,349). . —

Ch. 9—Hierarchy of Controls ● 185

CONCLUSION

In summary, OTA finds the hierarchy of con- controls allow easier monitoring of performance trols to be a well-founded and protective concept. by employers, employees, and OSHA. In addi- Applicable to both health and safety hazards, the tion, these controls are inherently more reliable hierarchy is derived from the experience of health and do not create employee burdens, and requir- and safety professionals and has been embodied ing them enhances the development of new con- for years in consensus standards, professional trols and production technology. practice, and OSHA regulations. Engineering con- OSHA’s reevaluation of its longstanding pol- trols are more likely to meet the essential require- icy favoring engineering controls for airborne con- ments for hazard control, and personal protec- taminants may indicate a shift in the agency’s ap- tive equipment is a last line of defense to be used proach to the hierarchy of controls. That policy when engineering controls are infeasible, insuffi- has led to improvements in the health of U.S. ciently protective, or not yet installed. The prob- workers and has spurred, at least to some extent, lems of personal protective equipment arise out the development of control technologies. Policy of 1) limitations in performance, 2) difficulties in changes that allow greater use of personal pro- evaluating their performance, 3) problems asso- tective equipment may endanger the health and ciated with their use, and 4) the physical and other well-being of many American workers and reduce burdens they create. Moreover, engineering con- the regulatory imperative to develop new and bet- trols are preferred on more general grounds be- ter production and control technologies. cause most personal protective equipment programs are inadequate and because engineering