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Control of Workplace Hazards for the 21st Century
Setting the Research Agenda

White Paper: Engineering Control Technology Research

The opinions and conclusions expressed are not considered as final statements of NIOSH policy or of any other organization.

Background

The objective of engineering control technology is to provide pragmatic recommendations on the prevention and control of worker exposure to hazardous conditions. The purpose of this paper is to discuss the future direction of research on this topic. First, this paper reviews the current status of engineering control technology and states a vision for the future application of engineering control technology. Then, the knowledge gaps and research needs in the following topics are discussed:

1. Control Strategy
2. Prevention of exposures.
3. Control of exposures.

Current Status of Control Technology Research

Frequently, engineering control technology is frequently focused on the application of local exhaust and dilution ventilation to reduce worker exposure. For example, in NIOSH's Engineering Control Technology Branch, nine of ten present research projects are focused upon ventilation as a control measure. One project is looking at fundamental exposure causes, in this case material dustiness. This narrow focus is also typical of research papers published by the industrial hygiene community. In reviewing papers for the American Industrial Hygiene Association's Best Engineering Paper Award for 1997, the committee only had nine papers to review, seven of these papers were focused upon ventilation. Only one paper was focused upon an overall control strategy.

A Vision of Control Technology

While ventilation is an important component of a comprehensive control plan, a more holistic strategy involving the prevention, minimization and control of exposures can be used to provide optimum control. The ideal time to prevent or minimize the hazards is during the initial construction or perhaps during the renovation of a process. In the industrial hygiene community, the term "substitution" generally refers to the selection of a material with a lower toxicity to replace a material with higher toxicity. Exposure prevention can also be accomplished by selecting materials, the material's form, processes, process equipment, and process configuration to prevent or minimize worker exposure. In dealing with control technology from a holistic perspective, one makes process decisions to minimize the contaminant generation and worker exposure before addressing the control measures. Furthermore, process choices can be made to enhance the ability of control measures such as local exhaust ventilation to control worker air contaminant exposures. This generally involves the enclosure of emission sources and the use of ventilation and air cleaners to capture or contain contaminants.

Control Technology Strategies

Analysis of Research Gaps

In using engineering control technology to control workplace hazards, some private companies use a comprehensive strategy to protect their workers . In addition, some need to devise control strategies for the safe use of their products (product stewardship). To develop control strategies, information is needed on the ability of different control approaches to protect workers.

Generally, engineering control technology field research addresses the need to look at different strategies. During applied field studies of control measures, exposure measurements are made at different operations or plants along with ventilation system measurements and observations. Types of information collected during such studies include: air flow patterns, contaminant, temperature, humidity, production rates, generation rates, and quantitative identification of exposure sources. This information and professional judgement can be integrated to develop conclusions and recommendations about the control measures studied. Generally, these studies provide useful insights and control options.

Although field studies do provide useful insights, one can only use professional judgement to apply empirical findings from one situation to another situation. In reviewing new processes before construction, one needs to estimate the magnitude of the resulting exposures. Thus, there is a need to develop an approach to predicting exposure from a process flow sheet, the manner in which ventilation is applied, and a knowledge of the material's properties. There is a need for the occupational safety and health community to work with engineering and manufacturing community to design equipment so that health and safety concerns are addressed.

Field studies frequently do not consider the applied economics of controlling the hazard. In the business world, economics is an important consideration in the selection of process options. Simply stated: Economics determines what actually is done. Concerns about trade secret information and confidential business information limit the dissemination about economic impact of control measures. This is especially true when one is considering actual process options. Certainly, field studies can document factors which drive costs.

Possible Research Topics

These research projects could enhance the development of control technology strategies:

1. Quantitative models relating exposure to process parameters which will assist in control decisions. Research in this area will help evaluate the reliability, and economics of control decisions and provide guidance on the information necessary for collection in field studies of exposure.
2. Economics and control strategies.

Exposure Prevention and Minimization

Hazard prevention research has received very minimal attention in the industrial hygiene community. However, this area of research offers great potential for reducing worker exposures. Successful research will probably require a more fundamental understanding of the processes involved. For example in order to develop a relevant test to characterize a powder's ability to generate dust or liquid's tendency to create mist, a fundamental understanding of the forces causing aerosol generation and particle adhesion are needed. Presently, there is very little research being published on these topics and purely empirical efforts have not yielded completely satisfactory results.

Possible research areas

1. Fundamentals of dust generation by solids. The physical form of solid (granules, flakes, slurries, powder, etc) can greatly affect aerosol generation. If one knew more about the generation of aerosols by powders, it might be possible to devise more appropriate dedusting treatments and to devise more relevant tests of material dustiness.
2. Fundamentals of aerosol generation by mists. In the machining industries, additives to suppress mist generation provide only a factor of two reduction in mist exposures. Perhaps, if one understood the details of mist generation, it would be possible to devise additives which are more successful at suppressing mist generation.
3. Performance of seals and fittings on process equipment. The ability of process equipment to minimize leakage is an important means of controlling emissions from process equipment.
4. Application of Process Safety Management review techniques to the control of worker exposures. In reviewing the design of equipment to prevent catastrophic losses, elaborate review processes have been devised. Perhaps, the same sort of review can be devised for contaminant generation so that designers are encouraged to think about process choices which affect generation rates and occupational exposures.

Hazard Control

Generally, occupational safety and health researchers have conducted much research on the application of local exhaust and dilution ventilation to control worker exposure. Recommendations on the application of ventilation are a product of practically every project conducted by the NIOSH Engineering Control Technology Branch. High velocity low volume (HVLV) ventilation has been studied and is a technique which controls the exposure. The successful application of local exhaust ventilation is complicated. In order to address these complications, Computation fluid dynamics (CFD) needs to be incorporated into applied ventilation related research. Also, the identification of wakes and eddies in actual operations can be difficult.

In recent years, recirculation has been used to conserve energy in the workplace including offices and machining operations. Air cleaners are used in cabin filtration on vehicles such as tractors, airplanes, and forklift trucks. Air cleaners are frequently discharged back into the workplace because of energy considerations and environmental rules. Thus, there is a need to study the industrial hygiene implications of air cleaner performance and reliability. Anecdotal reports indicate that some facilities use recirculation because the EPA permitting process is too burdensome.

Potential Areas of Research

1. Application of computational fluid dynamics to the design of local exhaust ventilation systems. This could be used as a part of an effort to develop mathematical model of workplaces. The models are needed to predict the effect of workplace changes upon exposure.
2. The use of microprocessor-based process controllers that, in principle, could incorporate sensors and basic decision-making for the operation of ventilation systems and other controls.
3. Recirculation. Evaluate the safety and health implications of air cleaner performance.

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