Thermal Work Environments – Part 5: Managing Conditions in Hot Environments

     Safeguarding the health and well-being of employees is among the critical functions of management.  In hot workplaces, monitoring environmental conditions and providing adequate protection comprise a significant share of these responsibilities.  The details of these efforts are often documented and formalized in a heat illness prevention program.
     An effective heat illness prevention program consists of several components, including the measure(s) used for environmental assessment, exposure limits or threshold values, policies defining the response to a limit or threshold being reached, content and schedule of required training for workers and managers, and the processes used to collect and review data and modify the program.  Other information may be added, particularly as the program matures.  Though it is nominally a prevention program, response procedures, such as the administration of first aid, should also be included; the program should not be assumed to be infallible.
     In this installment of the “Thermal Work Environments” series, the components of heat stress hygiene and various control mechanisms are introduced.  Combined with the types of information mentioned above, an outline of a heat illness prevention program emerges.  This outline can be referenced or customized to create a program meeting the needs of a specific organization or work site.

     The content of a heat illness prevention program is presented in five (5) sections:

• Training
• Hazard Assessment
• Controls
• Monitoring
• Response Plans

A comprehensive review of each would be unwieldy in this format.  Instead, an overview of the information is provided as an introduction and guide to further inquiry when one begins to develop a program for his/her team.

Training
     Every person that works in or has responsibility for a hot workplace should be trained on the ramifications of excess heat.  Information relevant to the following four sections is included in an effective training program.  Examples of important topics for all team members include:

• basics of human biometeorology and heat balance,
• environmental, personal, and behavioral risk factors,
• methods used to monitor conditions,
• controls in place to prevent heat illness,
• signs and symptoms of heat illness, and
• first aid and emergency response procedures.

Training of supervisors and team leaders should emphasize proper use of controls, signs and symptoms, and appropriate responses to heat illness and failure of control mechanisms.
     A complete training plan includes the content of the training and a schedule for delivery.  It may be best to distribute a large amount of information among multiple modules rather than share it in a single, long presentation.  Refresher courses of reduced duration and intensity should also be planned to combat complacency and to update information as needed.  Refreshers are particularly helpful when dangerous conditions exist intermittently or are seasonal.
 
Hazard Assessment
     An initial hazard assessment consists of identifying the elements of job design (see Part 1) that are heat-related.  These include environmental factors, such as:

• atmospheric conditions (e.g. temperature, humidity, sun exposure),
• air movement (natural or forced), and
• proximity to heat-generating processes or equipment.

Also included are job-specific attributes, such as:

• intensity of work (i.e. strenuousness and rate),
• personal protective equipment (PPE) and other gear required, and
• availability of potable water and a cool recovery area.

Other relevant factors may also be identified.  A compound effect could be discovered, for example, between concentration required for task performance and an increase in heat stress due to resultant anxiety.
     Using the information collected in the hazard assessment, a risk profile can be created for each job.  The risk profile is then used to prioritize the development of controls and modifications to the job design.
 
Controls
     Similar to that for quality [see “The War on Error – Vol. II:  Poka Yoke (What Is and Is Not)” (15Jul2020)], there is an implied hierarchy of controls used to manage heat-related effects on workers.  Engineering controls modify the tasks performed or the surrounding conditions, while administrative controls guide workers’ behavior to reduce heat stress.  Finally, personal protective equipment (PPE) is used to manage heat stress that could not otherwise be reduced.  PPE is often the first protection implemented and is used until more-effective controls are developed.
     A comprehensive heat stress control plan is developed by considering each term in the heat balance equation (see Part 2).  Examples of engineering controls include:

• To reduce metabolic heat generation, M, provide lift assists, material transport carts, or other physical aids to limit workers’ exertion.
• To reduce radiative heat load, R, install shields between heat sources (e.g. furnaces or other hot equipment) and workers, just as an umbrella is used to block direct sunlight.
• Use fans to increase evaporative cooling, E, when air temperature is below 95° F (35° C).
• Reduce air temperature with water-mist systems if relative humidity (RH) is below 50% and general air conditioning is not practical.

     Administrative control examples include:

• Establish policies that limit work during periods of excessive heat; thresholds can be based on Heat Index (HI), Wet Bulb Globe Temperature (WBGT), or other index.  The American Conference of Governmental Industrial Hygienists (ACGIH) regularly publishes threshold limit values (TLVs) based on WBGT with adjustments for clothing and work/rest cycles.  ACGIH TLVs often serve as the basis for standards and guidelines developed by other organizations and government agencies.
• Reduce M by increasing periods of rest in the work cycle.
• Implement an acclimatization program for new and returning workers that allows them to develop “resistance” to heat stress.
• Encourage proper hydration; ensure availability of cool potable water.

     Heat-related PPE examples include:

• Reflective clothing to reduce radiative heat load, R.
• A vest cooled with ice, forced air, or water increases conductive, K, and/or convective, C, heat loss.
• Bandana, hat or similar item that can be wetted to enhance evaporative cooling, E, particularly from the head and neck.
• Hydration backpack.

     Many controls are used in conjunction to achieve maximum effect.  Tradeoffs must be considered to ensure that the chosen combination of controls is the most-effective.  For example, cooling with a water-mist system increases humidity; if it begins to inhibit evaporation from skin, its use may be inadvisable.
 
Monitoring
     Monitoring is a multifaceted activity and responsibility.  In addition to measuring environmental variables, the effectiveness of controls and the well-being of workers must be continually assessed.  A monitoring plan includes descriptions of the methods used to accomplish each.
     Measurement of environmental variables is the subject of Part 4 of this series.  As discussed in that installment, multiple indices may be used to inform decisions regarding work cycle modifications or stoppages.  Those used in popular meteorology, such as Heat Index (HI), are often insufficient to properly characterize workplace conditions; however, they can be useful as early warnings that additional precautions may be needed to protect workers during particularly dangerous periods.  See “Heat Watch vs. Warning” for descriptions of alerts that the National Weather Service (NWS) issues when dangerous temperatures are forecast.
     After controls are implemented, they must be monitored for proper use and continued effectiveness.  This should be done on an ongoing basis, though a formal report may be issued only at specified intervals (e.g. quarterly) or during specific events (e.g. modification of a control).  Verification test procedures should be included in the monitoring plan to maintain consistency of tests and efficacy of controls.
     Monitoring the well-being of workers is a responsibility shared by a worker’s team and medical professionals.  Prior to working in a hot environment, each worker should be evaluated on his/her overall health and underlying risk factors for heat illness.  An established baseline facilitates monitoring a worker’s condition over time, including the effectiveness of acclimatization procedures and behavioral changes.
     Suggestions for behavioral changes, or “lifestyle choices,” can be made to reduce a worker’s risk; these include diet, exercise, consumption of alcohol or other substances, and other activities.  Recommendations to an employer regarding one’s fitness for certain duties, for example, must be made in such a way that protects both safety and privacy.  Heat-related issues may be best addressed as one component of a holistic wellness program such as those established by partnerships between employers, insurers, and healthcare providers.
 
Response Plans
     There are three (3) response plans that should be included in a heat illness prevention program.  Somewhat ironically, two of them are concerned with heat illness that was not prevented.
     The first response plan details the provisioning of first aid and subsequent medical care when needed.  Refer to Part 3 for an introduction to heat illnesses and first aid.
     The second outlines the investigation required when a serious heat illness or heat-related injury or accident occurs.  The questions it must answer include:

• Were defined controls functioning and in proper use?
• Had the individual(s) involved received medical screening and been cleared for work?
• Had recommendations from prescreens been followed by individual(s) and the organization?
• Had the individual(s) been properly acclimatized?
• Were special circumstances involved (e.g. heat advisory, other emergency situation, etc.)?

The investigation is intended to reveal necessary modifications to the program to prevent future heat illness or heat-related injury.
     The final response plan needed defines the review process for the heat illness prevention program.  This includes the review frequency, events that trigger additional scrutiny and revision, and required approvals.
 
 
     Currently, management of hot work environments is governed by the “General Duty Clause” of the Occupational Safety and Health Act of 1970.  The General Duty Clause provides umbrella protections for hazards that are not explicitly detailed elsewhere in the regulations.  It is a generic statement of intent that provides no specific guidance for assessment of hazards or management of risks.
     In 2021, OSHA issued an “advance notice of proposed rulemaking” (ANPRM) to address this gap in workplace safety regulations.  A finalized standard, added to the Code of Federal Regulations (CFR), will add specific enforcement responsibilities to OSHA’s current role of education and “soft” guidance on heat-related issues.
     That an OSHA standard will reduce heat-related illness and injury is a reasonable expectation.  However, it must be recognized that it, too, is imperfect.  No standard or guideline can account for every person’s unique experience of his/her environment; therefore, an individual’s perceptions and expressions of his/her condition (i.e. comfort and well-being) should not be ignored.  A culture of autonomy, or “self-determination,” where workers are self-paced, or retain other responsibility for heat stress hygiene, is one of the most powerful tools for safety and health management imaginable.
 
 
     For additional guidance or assistance with complying with OSHA regulations, developing a heat illness prevention program, or other Operations challenges, feel free to leave a comment, contact JayWink Solutions, or schedule an appointment.
 
     For a directory of “Thermal Work Environments” entries on “The Third Degree,” see Part 1:  An Introduction to Biometeorology and Job Design (17May2023).
 
References
[Link] Kodak's Ergonomic Design for People at Work.  The Eastman Kodak Company (ed).  John Wiley & Sons, Inc., 2004.
[Link] “NIOSH Criteria for a Recommended Standard Occupational Exposure to Heat and Hot Environments.”  Brenda Jacklitsch, et al.  National Institute for Occupational Safety and Health (Publication 2016-106); February 2016.
[Link] “Threshold Limit Values for Chemical Substances and Physical Agents.”  American Conference of Governmental Industrial Hygienists (ACGIH); latest edition.
[Link] “National Emphasis Program – Outdoor and Indoor Heat-Related Hazards.”  Occupational Safety and Health Administration (OSHA); April 8, 2022.
[Link] “Ability to Discriminate Between Sustainable and Unsustainable Heat Stress Exposures—Part 1:  WBGT Exposure Limits.”  Ximena P. Garzon-Villalba, et al.  Annals of Work Exposures and Health;  June 8, 2017.
[Link] “Ability to Discriminate Between Sustainable and Unsustainable Heat Stress Exposures—Part 2:  Physiological Indicators.”  Ximena P. Garzon-Villalba, et al.  Annals of Work Exposures and Health;  June 8, 2017.
[Link] “The Thermal Work Limit Is a Simple Reliable Heat Index for the Protection of Workers in Thermally Stressful Environments.”  Veronica S. Miller and Graham P. Bates.  The Annals of Occupational Hygiene; August 2007.
[Link] “Thermal Work Limit.”  Wikipedia.
[Link] “The Limitations of WBGT Index for Application in Industries: A Systematic Review.”  Farideh Golbabaei, et al.  International Journal of Occupational Hygiene; December 2021.
[Link] “Evaluation of Occupational Exposure Limits for Heat Stress in Outdoor Workers — United States, 2011–2016.”  Aaron W. Tustin, MD, et al.  Morbidity and Mortality Weekly Report (MMWR).  Centers for Disease Control and Prevention; July 6, 2018.
[Link] “Occupational Heat Exposure. Part 2: The measurement of heat exposure (stress and strain) in the occupational environment.”  Darren Joubert and Graham Bates.  Occupational Health Southern Africa Journal; September/October 2007.
[Link] “Heat Stress:  Understanding factors and measures helps SH&E professionals take a proactive management approach.”  Stephanie Helgerman McKinnon and Regina L. Utley.  Professional Safety; April 2005.
[Link] “The Heat Death Line: Proposed Heat Index Alert Threshold for Preventing Heat-Related Fatalities in the Civilian Workforce.”  Zaw Maung and Aaron W. Tustin.  NEW SOLUTIONS: A Journal of Environmental and Occupational Health Policy; June 2020.
[Link] “Loss of Heat Acclimation and Time to Re-establish Acclimation.”  Candi D. Ashley, John Ferron, and Thomas E. Bernard.  Journal of Occupational and Environmental Hygiene; April 2015.
 
Jody W. Phelps, MSc, PMP®, MBA
Principal Consultant
JayWink Solutions, LLC
jody@jaywink.com