The materials and methods used in manufacturing are changing rapidly and dramatically. So are the business management and product delivery models that have been part of the global manufacturing economy for decades. An informed and proactive industrial hygiene community can act now to embrace and influence the new challenges and opportunities that advanced manufacturing is creating. The current, traditional model of manufacturing includes large-scale production facilities that ship finished goods to strategically placed warehouses and distribution centers, where they are held until orders for these goods are received; the evolving 21st-century manufacturing model focuses on producing smaller, more distributed “batches” of products or individual product components that meet specific customer demands. One of the most notable changes is that the products are being manufactured closer to where they will be purchased or used. The current push in manufacturing is to have items made “just in time” and “just to order.” This new manufacturing model also includes a high degree of flexibility that promotes mass customization, which allows for several variations in a single product in order to match customer demands. Along with the advent of new technologies that support the growth of a distributed manufacturing model, products might also be made “just next door.” New manufacturing techniques—most notably, additive manufacturing and 3-D printing—are driving much of this change. Advanced robotics, synthetic biology, digital manufacturing interfaces, and rapid process simulation and prototyping are also accelerating the development of new ways to make things. In the United States, these innovations are being referred to as “advanced manufacturing.” These new manufacturing technologies frequently use or produce a new generation of materials now known as “advanced materials,” many of which originated in nanotechnology; this new way of manufacturing goes by many names: 21st-century manufacturing, advanced manufacturing, state-of-the-art manufacturing, next production revolution, next-generation manufacturing, industry 4.0. No matter what you call it, it is a rapid and dramatic change from the traditional manufacturing model that has evolved over the past 100 years.
Many of these new manufacturing and material technologies are simply a natural progression of nanotechnology research. A critical component of nanotechnology research has been developing good health and safety practices. (Figure 1 illustrates the overlapping development of nanomaterials and advanced materials.) For over 14 years, NIOSH has been an active contributor to the U.S. National Nanotechnology Initiative, supporting the effort to foster best practices. NIOSH has made major contributions in support of the safe and responsible development of nanotechnology, with a focus on protecting workers who manufacture and use engineered nanomaterials. NIOSH intends to leverage its knowledge and experience in managing engineered nanomaterials to create a framework that supports safe and responsible development of advanced manufacturing in the U.S.
The opportunity this progression presents to the occupational health and safety practitioner is that of translating and communicating all the best practices developed for nanotechnology over to advanced materials and advanced manufacturing processes. In many ways, good risk management practices will be the foundation for successful stewardship of advanced materials, processes, and products. Although not all types of manufacturing will change or be considered 21st-century manufacturing, enough of a change is underway that the industrial hygienist should be prepared for the resultant impact in the workplace. We are faced with the introduction of advanced materials into existing manufacturing processes and the development of totally new manufacturing technologies that might use either advanced materials or conventional materials, or both. Both situations present the need to reconsider how potential worker health and safety risks are evaluated and managed.
Let’s look at two types of 21st-century manufacturing and identify what new (and old) health and safety concerns may be of interest to the industrial hygienist.

ADDITIVE MANUFACTURING Additive manufacturing, as defined by the ISO/ASTM 52900 standard, encompasses seven technologies: binder jetting, directed energy deposition, material extrusion, material jetting, powder bed fusion, sheet lamination, and vat photo polymerization. (Figure 2 shows the key components of additive manufacturing.) In essence, this technology uses successive layering of very thin cross sections of a material until a three-dimensional product is built. It typically uses advanced materials (for example, metals, polymers, biopolymers, nanomaterials, ceramics, carbon fibers), which may be in the form of a fine powder, a liquid, or a solid strand. These materials are then subjected to very high and focused energy sources (such as lasers, E-beams, high temperatures) in order to bind (that is, melt, fuse, sinter, cure, or otherwise join) the material into very thin layers that build up to form the larger whole. The ISO and ASTM committees that developed the 52900 standard define 3-D printing as the fabrication of objects through the deposition of a material using a print head, nozzle, or other printer technology. However, the term is often used synonymously with additive manufacturing. The outputs from additive manufacturing vary from medical implants to aircraft wings.
Metal-based additive manufacturing uses fine metal powders; most commonly today these include aluminum, chromium, cobalt, molybdenum, nickel, steel, and titanium. To minimize worker exposures and safety concerns and to accommodate changes brought about by new additive manufacturing practices, companies will need to re-evaluate their current risk management procedures for handling fine metal powders. In some cases, a company that has not handled fine metal powder and dealt with resulting emissions will need the expertise of the industrial hygienist to help it develop an effective risk management plan.
Figure 1. The progression of materials, processes, and products, from nanotechnology to advanced manufacturing.
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Figure 2. Key components of additive manufacturing.
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Often, low-cost desktop-style 3-D printers that use polymer strands as feed material are built without any designed ventilation or fume/particulate capture devices; this contrasts with the design of commercial 3-D printers, some of which employ technologies requiring inert atmospheres or otherwise sophisticated enclosures that provide a high level of containment. (Figures 3 and 4 depict a desktop 3-D printer and a commercial model.) Affordable desktop-style 3-D printing technology has spawned increased applications in small businesses, schools, and home projects, where users may have inadequate ventilation for indoor airborne toxicants and limited access to professionals who can provide guidance on controls or personal respiratory protection. The health and safety concerns include possible exposures to the feedstock materials, ultrafine particles (including nanomaterials and fumes), metal powders, organic vapors, alcohols, aldehydes, BTEX (benzene, toluene, ethylbenzene, and xylene), or styrene, to name a few. With larger metal printers, there is the potential for dust (and nanomaterial) exposure during tasks such as post-processing recovery of unspent materials (powder recovery) or from finishing (for example, sanding) of the built object. Potential physical hazards include the use of combustible dusts, high-energy sources (lasers, high heat, pressure), or oxygen-deficient processes (for example, some metal printing is completed under an inert atmosphere).
Figure 3. A desktop 3-D printer (photo courtesy of MakerBot).
Figure 4. A large-scale 3-D printer (photo courtesy of Thermwood Electronics).
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Ozone and volatile organic compounds may be emitted from thermoplastic 3-D printers. When designing exposure assessment and control strategies, an industrial hygienist should consider the factors that influence the release of chemical contaminants (including known and suspected asthmagens, such as styrene and 4-oxopentanal) from 3-D printers. Relevant factors include those of the printer itself and the properties of the thermoplastic filaments.
Ergonomic considerations should be factored into any hazard analysis and risk management plan because 3-D printers vary in size from small desktop models to very large printers (some are close to the size of a semitrailer bed), and material handling will vary widely. ROBOTICS In use for more than 30 years, robots have become increasingly more sophisticated. New classes of robots are being designed to work alongside human workers (see Figure 5). Autonomous commercial vehicles are being tested on U.S. roadways as self-driving taxis. Autonomous tractors are plowing, planting, and harvesting fields, and drones are moving goods in warehouses and in the sky. In Japan, robots are being employed as store greeters and are performing simple household tasks. Robots are also being evaluated for use in dangerous environments, including mines, nuclear-contaminated sites, bomb detonations, and search-and-rescue in hostile locations. There are even workers equipped with performance-enhancing robotic devices such as robotic prostheses and exoskeletons (see Figure 6). The potential benefits are substantial and may prevent worker injuries and save lives; however, it is important to consider the possible harmful consequences of robot-human interaction.
Figure 5. Worker and robot interface (photo from ATE Centers Impact 2011 report,
Figure 6. Robotic exoskeleton (photo courtesy of National Science Foundation: Peter Neuhaus, IHMC Robotics).
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Risks from unintended contact with robots are a significant concern for workers in many industries, and voluntary consensus standards by the American National Standards Association and the Robotics Industry Association (such as R15.06, Industrial Robot and Robot Systems Safety Requirements) are relevant to robot safety.
However, these standards pertain primarily to automation-type robotics (that is, those robots that perform a single repetitive task) and not those that are autonomous or even those with some form of artificial intelligence (those robots that can learn and make adjustments). Today, there is much more opportunity for the human and robot to interact, and examining the health and safety implications will need to move beyond the old standby of lock-out/tag-out and noise control. Workplace safety standards for the operation, maintenance, and interaction of 21st-century robots and workers must be developed. Proactive approaches for establishing robotic risk profiles are needed, and redundant safety measures should be developed to protect those who work near the robots. Robots working in conjunction with workers may need design features such as proximity sensors or passive compliance systems to shut them down should they inadvertently contact a worker. The design of robots should also ensure that the motions of the robot are predictable to humans and do not cause any unpleasant reactions like fear or surprise. NEXT-GENERATION MANUFACTURING Manufacturing is changing. New materials that are more sophisticated, reactive, and efficient in their behavior are being utilized in novel ways, electronics are becoming smaller and faster, robots and their involvement in manufacturing are increasing in numbers and complexity—and these trends will affect how work is organized and how we protect workers’ safety and health. The smarter and faster supply chain plus the mass customization of products and processes will demand an agile work force and a new model for the organization of work. A work force may be distributed across multiple geographical locations instead of being concentrated all at one site, and workers may be dealing with more automated manufacturing provided by robotics.
Advanced manufacturing includes many complicated techniques that all have their own particular safety concerns. Addressing them will be a complex process; however, an initial framework for hazard identification can begin with assessing the feedstock materials, binding processes, and instrumental peculiarities of the specific technique in question and then analyzing them in a holistic way. As in other industries that utilize materials with unknown or altered toxicological profiles, manufacturing must employ containment and control strategies (such as enclosures) to minimize potential exposures; such tactics should constitute an effective, proactive approach to worker safety and risk management.
The time is right for all industrial hygienists to consider the reapplication of good industrial hygiene practice to the next generation of manufacturing. Industrial hygienists should follow the tried-and-true practice of protecting workers by hazard anticipation, recognition, evaluation, control, and confirmation. This practice includes determining the types and locations of hazards, identifying potential hazards or exposures, identifying the potentially exposed worker population, and developing a risk management plan. It is important for the industrial hygiene community to keep pace with the changes in processes and the continued introduction of new and more active materials—and to leverage resources with others who have greater expertise. NIOSH will continue to utilize knowledge gained from promoting responsible development of nanomaterials as it seeks to promote responsible development of 21st-century manufacturing. CHARLES GERACI, PhD, CIH, FAIHA, is associate director for Nanotechnology and Advanced Materials at NIOSH. He can be reached at (513) 533-8339 or via email. LAURA HODSON, MSPH, CIH, FAIHA, is coordinator of the Nanotechnology Research Center at NIOSH. She can be reached at (513) 533-8256 or via email.
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RESOURCES American National Standards Institute/Robotic Industries Association: R15.06: Industrial Robot and Robot Systems Safety Requirements (2012).
International Organization for Standardization/ASTM International: ISO/ASTM 52900, Additive Manufacturing—General Principles—Terminology (2015).
Journal of Occupational and Environmental Hygiene: “Characterization of Chemical Contaminants Generated by a Desktop Fused Deposition Modeling 3-Dimensional Printer” (July 2017).
Journal of Occupational and Environmental Hygiene: “Fume Emissions from a Low-cost 3-D Printer with Various Filaments” (July 2017).
Journal of Occupational and Environmental Hygiene: “Working Safely with Robot Workers: Recommendations for the New Workplace” (March 2016).

21st-century Manufacturing Challenges and Opportunities for Industrial Hygienists
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Disadvantages of being unacclimatized:
  • Readily show signs of heat stress when exposed to hot environments.
  • Difficulty replacing all of the water lost in sweat.
  • Failure to replace the water lost will slow or prevent acclimatization.
Benefits of acclimatization:
  • Increased sweating efficiency (earlier onset of sweating, greater sweat production, and reduced electrolyte loss in sweat).
  • Stabilization of the circulation.
  • Work is performed with lower core temperature and heart rate.
  • Increased skin blood flow at a given core temperature.
Acclimatization plan:
  • Gradually increase exposure time in hot environmental conditions over a period of 7 to 14 days.
  • For new workers, the schedule should be no more than 20% of the usual duration of work in the hot environment on day 1 and a no more than 20% increase on each additional day.
  • For workers who have had previous experience with the job, the acclimatization regimen should be no more than 50% of the usual duration of work in the hot environment on day 1, 60% on day 2, 80% on day 3, and 100% on day 4.
  • The time required for non–physically fit individuals to develop acclimatization is about 50% greater than for the physically fit.
Level of acclimatization:
  • Relative to the initial level of physical fitness and the total heat stress experienced by the individual.
Maintaining acclimatization:
  • Can be maintained for a few days of non-heat exposure.
  • Absence from work in the heat for a week or more results in a significant loss in the beneficial adaptations leading to an increase likelihood of acute dehydration, illness, or fatigue.
  • Can be regained in 2 to 3 days upon return to a hot job.
  • Appears to be better maintained by those who are physically fit.
  • Seasonal shifts in temperatures may result in difficulties.
  • Working in hot, humid environments provides adaptive benefits that also apply in hot, desert environments, and vice versa.
  • Air conditioning will not affect acclimatization.
Acclimatization in Workers