Heat Stress & Occupational Health

New Understandings in Heat Stress

Emma Moynihan, MPH Doctoral Candidate – Johns Hopkins University Advisor: Gurumurthy Ramachandran, PhD Outline

• Introduction • Heat Stress & Occupational Health • Measuring Heat Stress • Worker Protections for Heat Stress • Application of Remote Sensing to Determine Heat Stress • Conclusion

1 Introduction

Sengupta, S & Frank, B.L (August 25, 2020). Heat Smoke and COVID are Battering the Workers who Feed America. The New York Times. Heat, Smoke and Covid Are Battering the Workers Who Feed America - The New York Times (nytimes.com)

• Nearly half (47%) of all jobs in the United States require working outside, where exposure to heat stress greatest, for some part of the workday.2

• Workers at particularly high risk to heat stress include: • Agricultural Workers • Emergency Responders • Firefighters • Construction & utility Workers • Healthcare workers • Transportation Workers3 Figure one: OSH Heat-Related Deaths and Extreme Heat Projections4

©2015,© 2020,© Johns2014, Johns JohnsHopkins Hopkins Hopkins University. University. University. All All rights rights All reserved.rightsreserved. reserved. 3 What is Heat Stress? Universal Thermal Climate Index Heat Exhaustion Heat Stress Heat Stroke Wet Bulb Globe Temperature Heat Strain Heat Index

©2015,© 2020,© Johns2014, Johns JohnsHopkins Hopkins Hopkins University. University. University. All All rights rights All reserved.rightsreserved. reserved. Definition of Heat Stress The National Institute for Occupational Health and Safety (NIOSH) defines heat stress as:4 “The net head load to which a worker is exposed from the combined contributions of metabolic heat, environmental factors, and clothing worn which results in an increase in heat storage in the body “ • Heat Strain – Physiological reaction heat, where body tries to stabilize body temperature and maintain homeostasis • Heat Exhaustion – Illness where core body temperature rises above 38 C/100.4 F leading to altered function of 1+ organ systems, if not controlled can lead to… • Heat Stroke – Medical Emergency when body temperature rises over 41.1 C/106 F. Onset at central nervous system

Heat Index: 26A measure of what the temperature “feels” like to us – a combination of relative humidity and air temperature.

Wet Bulb Globe Temperature: 30 Considered workplace gold standard for heat stress. Measurement of heat stress in sunlight.

Universal Thermal Climate Index: 29 A relatively new metric that uses air temperature plus a number of “offsets” that are supposed to more accurately reflect humans physiological response to heat stress.

Intergovernmental Panel on Climate Change (IPCC) declared the limited knowledge regarding the effects of climate change on workers is a research gap that needs to be prioritized.6

By the mid 21st century, the number of 38 C/100 F+ days are predicted to double or even triple compared to the period 1970-2000.7 Source: Schwingshackl et. al (2021)8 Heat Stress and Climate Change: A Public Health Burden Each year, 700+ deaths are attributed to heat exposure in the United States.5

Heat exposure causes more deaths than hurricanes, tornados, and floods.9

By end of 21st century thousands to tens of thousand more annual deaths are expected due to heat exposure.10

Chicago Heat Wave of 1995 – 739 deaths in period of a week

• Introduction • Heat Stress & Occupational Health • Measuring Heat Stress • Worker Protections for Heat Stress • Application of Remote Sensing to Determine Occupational Heat Stress • Conclusion

1 Heat Stress and Occupational Health • 79 worker fatalities between 2014-2016 directly due to environmental heat reported to OSHA.6 • The number of illnesses and injuries related to heat stress in the work-place is likely much higher. There is limited research on this topic. • Heat stress is not limited to workers outdoors. • NIOSH estimates 5-10 million workers are exposed to high temperatures at work that puts them at risk for serious medical Source: Los Angeles Times (2017) conditions.11 • Complicated by the fact other worker protections like PPE, can exacerbate heat stress.11 What happens to the body under heat stress?

The human body works to maintain a temperature around 37 C/98.6 F through a process known as thermoregulation. A series of feedback loops through the body work to dissipate heat or stimulate heat- preserving mechanisms depending on need.

There are limits to the human body’s ability to maintain homeostasis in the face of extremes, and this can be modified by age, overall health, climate acclimatation etc.

©2015,© 2020,© Johns2014, Johns JohnsHopkins Hopkins Hopkins University. University. University. All All rights rights All reserved.rightsreserved. reserved. Risk Factors for Occupational Heat Related Illness and Injury

Source: NIOSH, 2016 The Importance of Worker Acclimization to Hot Environments

• More than 50% of heat related fatalities on the job occur within the first few days of working in warm environments.12 • NIOSH recommends no more than 20% exposure to a hot environment in the first few days on the job, gradually increasing by 20%.13

Source: NIOSH, 2014 Three Examples of Occupational Illnesses and Injuries Associated with Heat Stress

Fatalities due to direct heat exposure are among the most severe consequences of heat stress, but there are other insidious examples of heat stress negatively impacting worker health and well-being.

Three Examples are: 1. Chronic Kidney Disease of Unknown Etiology/Origin (CKDu) among Agricultural Workers

2. Elevated stress hormones among foundry Workers

3. Increased risk of cardiovascular disease Chronic Kidney Disease of Unknown Origin (CKDu) • In the late 20th century, cases of advanced kidney disease began to appear in global agricultural worker populations without presence of the disease’s traditional risk factors: diabetes, hypertension, and older age. • While some risk factors for CKDu remain enigmatic, “What we do know for certain is that CKDu is related to heat exposure and dehydration.”14 Elevated Stress Hormones

• Foundry plant workers exposed to higher wet bulb globe temperatures (WBGT) during their shift had elevated levels of cortisol, adrenaline, and noradrenaline compared to workers exposed to lower WBGTs.15 • Also found a decrease in cognitive performance among workers exposed to high WBGTs over course of shift.15 Heat Stress and Cardiovascular disease

• Heat stress puts additional strain on the cardiovascular system, requiring increased blood flow in attempt to maintain homeostasis.16 • A large cohort study in Finland found an increased risk of cardiorespiratory ailments among certain occupations (agriculture compared to industry or office work) and among individuals exerting a greater physical load at work compared to a less physical load.17 ACGIH

Source: ACGIH, 2019 Outline

• Introduction • Heat Stress & Occupational Health • Measuring Heat Stress • Worker Protections for Heat Stress • Application of Remote Sensing to Determine Heat Stress • Conclusion

1 Measuring Heat Stress • There are many metrics available • Heat Stress can be measured: to measure heat stress including (but not limited to): Indirectly • Remote Sensing • Wet Bulb Globe Temperature (WBGT) – “Gold Standard” • Questionnaire/Surveys • Heat Index Directly • Which itself has multiple equations • Personal Monitoring • Apparent Temperature Instruments • Universal Thermal Climate • Area Monitoring Index • Biomarkers • Effective Temperature, among others Personal Monitoring • There are a number of wearable instruments to measure WBGT, heat index, temperature, relative humidity etc.

Kestrell 5400 Heat Stress Tracker & Weather Meter. Can also be used for area monitoring

Source: Negin Nazarian et al 2021 Environ. Res. Lett. 16 034031 More Examples of Personal Monitoring

OSHA-NIOSH Heat Safety App

• Measures Heat Index – modified for working conditions.

• Works by plugging into phone’s locations services.

• Option to edit variables (i.e. temperature, humidity, location) to predict heat index.23

Source: NIOSH, 2021 Biomarkers of Heat Stress

What is a biomarker? “A biomarker is a biological characteristic that is objectively measured and evaluated as an indicator of normal biological or pathological processes, or a response to a therapeutic intervention. Examples include patterns of gene expression, levels of a particular protein in body fluids [i.e blood], or changes in electrical activity in the brain.”24

Source: Minnesota Dept of Health, 2020 Biomarkers of Heat Stress

Examples of potential heat stress biomarkers Heat stress can also be measured indirectly. include: Proxy indicators for heat stress might include dehydration, which can be 1. “Heat shock proteins (HSPs) measured through urine specific gravity. 2. Innate immune markers, such as Acute Phase Proteins (APPs) 3. Oxidative stress markers and, 4. chemical secretions in the saliva and urine. ”25

Physiologic monitoring, such as through heart rate, body temperature etc. can also indirect proxies for heat stress.

Source: Gordon, R.E., Kassier, S., & Biggs, C. (2015) Area monitoring

In contrast to personal monitoring or ‘wearable’ instruments, area for heat stress records the ambient surroundings of a worker/group of workers.

Image: TSI QuestTemp

A WBGT and Heat Index area monitor Area Monitoring

• Weather stations

• NOAA provides archived Climate data going back several decades.

• Real time data available from National Weather Service Remote Sensing: ”Remote sensing is the process of detecting and monitoring the physical characteristics of an area by measuring its reflected and emitted radiation at a distance (typically from satellite or aircraft). Special cameras collect remotely sensed images, which help researchers "sense" things about the Earth. “26

The Landstat satellite program has been in continual existence since the 1970s to take remote satellite images of the United States. Landstat 9 will launch September 2021.

Data are publicly available. Source: NASA, 2020 Many Different Metrics to Measure Heat Stress • There is no official measure for heat stress, though a number of metrics have been used in research and for industrial hygiene purposes. • Estimated more than 100 in the literature.28

• The decision on which metric to use will depend on needs, what data are available, what the climate looks like (for instance, some metrics better in shade than direct sunlight). Apparent Temperature

• Developed by Robert Steadman in 1970s/1980s • What the temperature “feels” like to humans – includes relative humidity, wind speed/chill and air temperature.

• Simplified Formula

Apparent Temperature = -1.3 + 0.92*Temperature (°C) + 2.2*e

*e is vapor pressure in kPa.27

Steadman, 1979a Examples of Apparent Temperature used in Public Health Heat Index

• “Calculating apparent temperature using Steadman’s original equations requires iterating multiple equations that describe heat and moisture transfer until a final equation converges.”26

• A simplified version of apparent temperature, taking into consideration air temperature and relative humidity.

• Used by the National Weather Service to describe what the temperature “feels like.” Source: NOAA Heat Index

• T = Temperature • A simplified version of apparent temperature, taking • HI = Heat Index into consideration air temperature and relative humidity.

• Many iterations on Steadman’s apparent temperature have been developed in the literature. • See Anderson et al., 2013

Source: Anderson et al, 2013 Examples of Heat Index in Public Health Universal Thermal Climate Index (UTCI)

• Developed in 2009 by consensus of scientists. • Motivated by: • Lack of consensus regarding which existing metric to use. • Wanted metric that would be suitable for all climates and seasons. • Lack of metric designed to be thermal-physiologically relevant.29 Formula: UTCI = Temperature + Offset(Ta, Tmrt, va, vp)

Ta = Air Temperature Tmrt = Mean Radian Temperature Va = Wind Speed Vp = Vapor Pressure or Relative humidity Universal Thermal Climate Index (UTCI)

• Provide reference values to make estimating UTCI more accessible

Source: Krzysztof Blazejczk et. al, 2013. Wet Bulb Globe Temperature

• Developed by the U.S. military in the 1950s30 • Considered the ‘gold standard’ in Occupational Health Formula: • Used for “direct sunlight” • OSHA Estimated WBGT Calculator: WBGT = (.7 * Tw) + (.2 * TG) + (.1 * T) https://www.osha.gov/heat- exposure/wbgt-calculator Where: T = Temperature in Celsius • Takes into consideration: Tg = Globe thermometer temperature in Celsius 1. Air Temperature Tw = Wet-blub Temperature in Celsius 2. Humidity 3. Wind speed 4. Sun angle 5. Cloud Cover (Solar Radiation)29 Measurement Challenges with WBGT

• Solar Radiation and Sun Angle are not easily accessible meteorological variables to collect with standard weather data.

• As such, researchers have developed equations and metrics that approximate the WBGT. Summary of WBGT Recommended Limits

Source: NIOSH, 2016 Are current WBGT recommendations protective enough?

• A Morbidity and Mortality Weekly Report (MMWR) evaluated whether NIOSH and other IH organizations have recommended WBGT that are protective enough to prevent mortality.31

Source: Tustin et al., 2018 Outline

• Introduction • Heat Stress & Occupational Health • Measuring Heat Stress • Worker Protections for Heat Stress • Application of Remote Sensing to Determine Heat Stress • Conclusion

1 OSHA

National Weather Service Heat Index with OSHA notes21

Beyond the general standard duty clause, there is no federal standard to protect workers from hot environments (indoor or outdoor).

As a result, an estimated 130 million workers in the United States lack specific protection against hot environments. 18 NIOSH

REL-Recommended Exposure Limit

Source: NIOSH 2016 State Protections

1. Maryland – Has until 2022 to adopt protections.19

2. California – Above 29C/85F, employers must provide shade, water and education about heat illness prevention.20

3. Washington – Action limits depend on clothing worn (52-89F). Employers must provide water and education on heat illness Source: Cal/OSHA, 2021 prevention. Indoor and outdoor. 21

4. Minnesota – Uses two-hour time-weighted averages of WBGT depending on activity level. Indoor and outdoo.r22 Outline

• Introduction • Heat Stress & Occupational Health • Measuring Heat Stress • Worker Protections for Heat Stress • Application of Remote Sensing to Determine Heat Stress • Conclusion

1 Remote Sensing Example for Retrospective Assessment • Example of remote sensing methods to assess occupational exposure to heat stress retrospectively.

• Currently researching association between pesticide use, heat stress, and chronic kidney disease among agricultural workers in the United States. • Heat exposure not captured during study –retrospectively assessing it using climate data.

• Basic Steps: 1. Gather climate data 2. Geocode climate data to each worker’s home address 3. Determine how to aggregate climate data for each worker 4. Develop heat stress metric for each worker given available climate data and known work history AHS Demographics Characteristic Percentage Gender Male 97% • National Institute of Environmental Health Sciences Female 3% & National Cancer Institute Race White 97% • A prospective cohort study of 52,394 pesticide Other 3% applicators, 32,345 spouses of applicators, and State 4,916 commercial applicators Iowa 61% • Study began in 1993 and is ongoing with four North Carolina 39% completed stages Education ≤ High School 59% • North Carolina and Iowa > High School 41% Smoking Status • Survey-based research (limited biomarker data) Never Smoked or Past Smoker 84% Current Smoker 16% • Asks questions about pesticide use, health history, work practices, demographics, and lifestyle & diet

©2015,© 2020,© Johns2014, Johns JohnsHopkins Hopkins Hopkins University. University. University. All All rights rights All reserved.rightsreserved. reserved. 11 Remote Sensing Data • Data source on daily climatic variables from 1979-2018 come from the North American Regional Reanalysis (NARR).33

• An atmospheric reanalysis is a highly popular method that combines modeling with past weather data.32

• In NARR, data available at 32 kilometers /20 miles grid.

• Data available daily and monthly • Climatic variables include (but not limited to): • Air temperature • Wind Speed • Soil Moisture Content • Vegetation • Precipitation • Humidity • Cloud Cover Source: NOAA PSL, 2021 Geocoding • Geocoding is the process of matching “points” on a map (often addresses) to coordinates (Latitude and Longitude).

• Geocoding can also be used to merge multiple datasets together, so long as latitude and longitude coordinates are available.

• We geocoded agricultural worker’s home address to the closest 32KM grid from NARR.

Source: ESRI, 2021 • Asked for updated addresses in follow-up surveys Constructing Heat Stress Metric for Each Worker • Data were not available to calculate Wet Bulb Globe Temperature (WBGT).

• Instead, we estimated Heat Index (HI) for each worker using relative humidity and air temperature.

• Approximated WBGT for each worker using equation developed Thomas Bernard and Ivory Iheanacho (2015).33

WBGT = [ (-.0034 * HI2 ) + (.96 * HI) -34 ] + 3.5 C Constructing Heat Stress metric for Each Worker

• Create seasonal average (May-September) relative humidity and temperature for each worker from daily NARR data from 1979-2018. • May through September is when workers most at risk for heat stress and coincides with pesticide application.

• Use seasonal average relative humidity and temperature data for each worker to create a seasonal Heat Index value. • For sensitivity analysis, also calculate Heat Index using maximum relative humidity and temperature values as well as 95th percentile values.

Input Heat Index for each worker into previous equation to estimate WBGT. • Use estimated WBGT in regression model looking at association between WBGT (as measure of heat stress) and chronic kidney disease (CKD) Outline

• Introduction • Heat Stress & Occupational Health • Worker Protections for Heat Stress • Measuring Heat Stress • Application of Remote Sensing to Determine Heat Stress • Conclusion

1 Conclusion

• Currently no federal protections exist to protect workers from heat stress beyond OSHA’s general duty clause.

• There is no one agreed upon definition of heat stress or exposure limits for heat stress.

• While WBGT is commonly thought as a gold standard for assessing occupational heat stress, many other (100+) measures exist and as such there is a lack of consensus on which to use and when.

• Some metrics, including WBGT are challenging to use given the climatic variables required, so alternatives have been proposed.

• Data from remote sensing, satellite imagery, and local weather stations can be a valuable resource in retrospectively assessing occupational heat stress. Still, we should be aware of the limitations in doing so (exposure misclassification etc.) Thank You! Questions?

Johns Hopkins Bloomberg School of Public Health Funding Sources Gurumurthy Ramachandran, PhD Jordan Kuiper, PhD 1. U.S. Centers for Disease Control & Prevention, Roni Neff, PhD National Institute for Occupational Safety and Health (T42 OH0008428) National Institute of Environmental Health Sciences Dale Sandler, PhD - Chief, Epidemiology Branch 2. Johns Hopkins Education and Research Center for Christine Parks, PhD – Staff Scientist Occupational Safety and Health National Cancer Institute Laura Beane-Freeman, PhD, Senior Investigator Mary Ward, PhD, Senior Investigator Rena Jones, PhD, Investigator

Occupational Health and Safety Administration Joseph Coble, PhD – Director of Technological Feasibility

©2015,© 2020,© Johns2014, Johns JohnsHopkins Hopkins Hopkins University. University. University. All All rights rights All reserved.rightsreserved. reserved. References 1. Sengupta, S & Frank, B.L (August 25, 2020). Heat Smoke and COVID are Battering the Workers who Feed America. The New York Times. Heat, Smoke and Covid Are Battering the Workers Who Feed America - The New York Times (nytimes.com) 2. Bureau of Labor Statistics (2017). Retrieved: https://www.bls.gov/opub/ted/2017/over-90-percent-of-protective-service-and- construction-and-extraction-jobs-require-work-outdoors.htm. Accessed: March 20, 2020 3. Schulte, P. A., & Chun, H. (2009). Climate Change and Occupational Safety and Health: Establishing a Preliminary Framework. Journal of Occupational and Environmental Hygiene, 6(9), 542-554. doi:10.1080/1545962090306600 4. NIOSH [2016]. NIOSH criteria for a recommended standard: occupational exposure to heat and hot environments. By Jacklitsch B, Williams WJ, Musolin K, Coca A, Kim J-H, Turner N. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication 2016-106 5. Vaidyanathan A, Malilay J, Schramm P, Saha S. Heat-Related Deaths — United States, 2004–2018. MMWR Morb Mortal Wkly Rep 2020;69:729–734. DOI: http://dx.doi.org/10.15585/mmwr.mm6924a1external icon. 6. Intergovernmental Panel on Climate Change (IPCC). (2018).The 1.5 Health Report: Synthesis on Health & Climate in the IPCC SR1.5 7. : Kristina Dahl et al 2019 Environ. Res. Commun. 1 075002 8. Schwingshackl, C., Sillmann, J., Vicedo-Cabrera, A.M., Sandstad, M., Aunan, K. (2021). Heat Stress Indicators in CMIP6: Estimating Future Trends and Exccedances of Impact-Relevant Thresholds. Earth’s Future. https://doi.org/10.1029/2020EF001885 9. Climate change is killing Americans. Health departments aren’t equipped to respond – Center for Public Integrity 10. Chapter 2: Temperature-Related Death and Illness | Climate and Health Assessment (globalchange.gov) 11. Gubernot, D. M., Anderson, G. B., & Hunting, K. L. (2014). The epidemiology of occupational heat exposure in the United States: a review of the literature and assessment of research needs in a changing climate. International journal of biometeorology, 58(8), 1779–1788. https://doi.org/10.1007/s00484-013-0752-x 12. https://www.osha.gov/heat-exposure 13. https://www.cdc.gov/niosh/topics/heatstress/acclima.html 14. Sorensen, C., & Garcia-Trabanino, R. (2019). A New Era of Climate Medicine – Addressing Heat Triggered Renal Disease. New England Journal of Medicine 381:693-696. DOI: 10.1056/NEJMp1907859

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