A picture of one of the places where I work. The big pot in the middle is a cruise of molten aluminum. But behind that is the more important part. Those are little areas where molten aluminum is being made from alumina. When those pots are opened, when somebody lifts one of those lids, they're now exposed to 1400 degrees Fahrenheit. And it may be from 10 to 15 to 30 minutes. So the microenvironment is even more important sometimes than the total ambient environment. And I just do that as a kind of reminder to me of what the work involves. The work group on occupational heat-related illnesses were all of these individuals here. They did an incredible amount of research. They did Yeoman's work on putting everything together. And we were able to finally bring it into a full document that was used on the ACOM website and it's also in the JOEM. And we aren't going to cover the entire document at this time. But we will cover some of what we think are the pertinent areas. But we also firmly believe that it is really important that you actually get a chance to read it. And somebody says, well, why would ACOM do a heat-related illness prevention guidance document? Well, the fact is, OSHA is still working on their document and their regulations. And we felt that somebody should take the lead, provide guidance to all due to the effects of increasing heat from climate change and lack of standards in many locales. We do acknowledge that there are some locales that do have excellent requirements and regulations. But we also need to remember that as we have found out, many workers are now working much longer hours due to manning shortages. And some of the factories that I deal with, there is forced overtime routinely now. So part of the issue that we deal with is the increasing ambient temperatures. Both the National Oceanographic Atmospheric Administration and NASA state that between 2009 and 2020 was the hottest decade on record in the contiguous United States. 2020 was the fifth warmest year on record, with the five warmest years all occurring since 2012. Climate scientists predict or project that these warming trends will continue into the future. Therefore, it is likely that U.S. workers will be at increasing risk of heat-related illnesses occur more often and in more parts of the country. There is a prior ACOM guidance statement about climate change that contains general heat-related recommendations, and reviewing that article will be of benefit to you. And again, it's on the ACOM website under guidance documents. The document covers issues of heat-related illnesses that the occupational medicine provider should be aware of and does suggest ways to help the employer avoid heat-related illnesses. The document is subdivided into pertinent sections, as can be seen on the list above, that are easy then to navigate through. Methods of heat stress, personal risk factors, guidance for helping employers, and guidance for returning people back to work after a heat-related illness, which ideally is preventive medicine specialists, we don't see happening, although that is a dream. Heat stress has direct impact from excessive heat exposure. It can range from simple things as heat rash to heat stroke. And heat stroke can be fatal. Heat-related illnesses such as heat exhaustion must be taken seriously because it can progress quickly to heat stroke if the heat exposure continues. And I've seen this in my own life, and if we can prevent it ahead of time, then we can allow the person to not be endangered. Heat stroke itself is a life-threatening emergency with a reported case fatality rate above 80 in some workers. It is critical to remember that often the first manifestation is not core body temperature, but in fact confusion or other neurologic abnormalities. And we've seen this in the smelter more than once, that that was in fact how we determined it was heat stroke. And there are also other less severe diagnoses, but heat-exposed workers can develop other acute or chronic disorders. And we've seen traumatic injuries from people having cognitive impairment from heat stroke. So recommendations to protect workers from heat-related illness require, number one, a prevention plan, but number two, an emergency plan. And both of those are critical, and employers need to understand that. Now in determining heat stress, the industrial hygienists use that term, and it encompasses both environmental and metabolic heat produced by physical activity. And both components contribute to workers' overall thermal load. Wet bulb globe temperature is the obvious preferred environmental heat metric, which measures air temperature, humidity, wind speed, solar radiant heat, but the reality is most people don't do it. In the military, we always use wet bulb, but in the civilian world, it is not as common. Alternatives to wet bulb globe temperature include dry bulb temperature and heat index. The heat index is a screening tool that uses temperature and relative humidity to calculate an adjusted temperature, representing how the conditions feel more accurately than just the ambient temperature. And in reality, that's what most employers use, either the heat index or the ambient temperature. But we also have to remember, as I stated earlier, a microenvironment exists where there is excessive heat in a small location. The suggestion would be firefighters outside a building do not experience the same heat stress environment as those inside the burning building. And the recommendations for an employer prevention program are really good old basic preventive medicine, everything we always learn, the hierarchy to eliminate engineering controls. And engineering controls is obviously the most preferred when possible. But other important components include acclimatization protocols for new workers, work rest cycles or self pacing, heat stress hazard assessments, provision of hydration fluids, training about heat related signs and symptoms, and an emergency response plan. The elimination of exposure is, again, the most effective. And PPE controls are the least effective. A good heat stress prevention program should focus primarily on the levels in this diagram between engineering and administrative controls. Some engineering controls may involve cooling the environment with air conditioning, fans, increased ventilation. And the administrative controls may include a acclimatization plan, training on heat stress related illness and first aid, and emergency response procedures. You can also consider medical monitoring and surveillance, job rotation, work distribution to reduce exertion exposure, or water and cool down areas, physiologic monitoring, which we'll talk a bit more about in a second, work rest cycles, and things to do when there is high heat events. There are other resources that you can look at here, and again, the information is on the slides that are in SwapCard that will help you. Recommendations for unacclimatized workers, and we all know that we have people that just come into a job new, we have migratory farm workers, we have multiple people that don't have a clue what the heat stress is. And those are at the greatest risk of heat related illnesses. And so the recommendation is to expose them to the heat stress over a period of seven to 14 days. Which also throws into the fact if someone works in a high heat environment and has been doing it for a while, and they're off for seven days, they're back to basically an unacclimatized worker. And as stated on the chart here, you can do two hours a day the first day, three hours, work slower, have greater work rest cycles, and more hourly breaks, and ideally some administrative controls of air conditioning or a shaded area. These are ideal perfect world things, okay? And just as anecdotally, when Dr. Bourgeois, the AECOM president, was involved with the Deepwater Horizon oil spill in the Gulf, and they had over 49,000 workers that had no clue about heat, they were all unacclimatized, despite the fact of not doing any pre-employment evaluations or anything else, all these 49,000 workers had no serious heat related illnesses or deaths from heat because they worked on an acclimatization process. So that is very critical. And physiologic monitoring, that has some great potential. It's difficult, it's expensive. One plant I know we found that we had some difficulty with the Bluetooth wiring to monitor, and we've had some pushback from workers that you're violating their privacy, from unions, but slowly it is gaining some traction, and the equipment that's out there now is much improved and is quite worth looking at if your company can afford it, but the reality is most people who work in heat work for very small companies, not large factories. And so we have to train the coworkers to recognize impending heat stress as part of the physiologic monitoring. The work evaluation is really nice. The problem is we, as occupational medicine providers, end up seeing the back end of the problem because they aren't evaluated ahead of time. People are just hired, put to work, and so we see the end of it. But it's nice to have this as a basic plan to say what you can or shouldn't do, and we'll cover this a little bit more now. There are personal risk factors for heat-related illness, and if given the opportunity to gain the information, at least the medical history for preexisting medical conditions, we have the ability possibly to find ways to mitigate working conditions, which then would decrease the risk of heat-related illnesses. That would be at least something we can do. Also, there's a lot of medications that cause people problems in the heat. I have had applicants for heat environments who are on medications to prevent sweating. I don't have a good way to get through that one. But if we're given the opportunity to do a pre-work evaluation, the history of the medications they're on is quite pertinent because then you could talk to the examinee, discuss options that they could talk about with their primary care provider to help them to, again, avoid heat-related illnesses. I think that that last slide and this slide are two, if you take nothing else from the guidance, these are really worth it, okay? I'm sorry, I blew it. I'm going slow around my slides. You can see the list of medications. They're quite extensive, actually. Okay, heat stress prevention program, medical monitoring. In the perfect world, this is ideal, but at least try to get your employers to do some level of screening. If nothing else, list of meds, history of prior heat injuries, and their previous medical and occupational history. Emphasis on past, present, and anticipated exposures to heat and hot environments, prior history of heat-related illness, risk factors for heat-related illness, emphasis on the respiratory, cardiovascular, musculoskeletal, neurologic, urinary systems, and medication and substance use that can block or interfere with sweating. And they talked about if you're worried about kidney injuries, you can evaluate by creatinine kinase, again. These are perfect world things that most companies won't pay for, and we as authors understand this is not a perfect world, so we encourage you to just do as much as the company will let you do. Return to work, this gets tough, because sometimes the prudent thing is to restrict them totally from heat exposure, but then you're jeopardizing people's livelihoods, and unless you work with a company that has options for non-heat exposure. Also, there are serum biomarkers may be elevated acutely in episodes of heat stroke or other types of heat-related illnesses, such as kidney disease, but OEM clinicians should ensure that the elevated biomarkers return to normal before clearing a worker to return to work. But biomarkers that are persistently elevated should require an evaluation by a specialist such as a nephrologist for kidney disease, et cetera. One challenge in determining the recovery from heat-related illnesses is that organ damage may be present even if biomarkers have returned to normal. Just throw a curveball here. There are lots of other resources on this information that are well worth looking at from the National Oceanic Atmospheric Administration, from CDC, and from OSHA, and OSHA has some good stuff they're working on, their heat stress guidance and regulations. The overview. This document is not the be-all and end-all on prevention of heat-related illnesses, but it gives you a good background. It gives guidance, and the authors realized that not all situations are the same, not all companies can afford routine testing and monitoring. But it behooves us as occupational and environmental medicine providers to provide the best advice we can to our companies and to their workers. And the bottom line is there's lots of processes that you can do, but if you have no other option, make sure your company tries some type of acclimatization. I thank you for your time, and now I'm going to pass it over to the next speakers, okay? Good morning. I'm going to present or introduce Dr. Judith Eisenberg while she gets her slides up on Zoom. Dr. Eisenberg is a board-certified emergency medicine physician who has been a medical officer with NIOSH since 2004 when she arrived as a new CDC EIS officer to the Health Hazard Evaluation Program. In 2020, she became the lead of the NIOSH Firefighter Fatality Investigation and Prevention Program's medical team. She is a contributing author to the 2016 update of the NIOSH Heat Stress Criteria document and has served as a heat stress subject matter expert during the Deepwater Horizon oil spill cleanup, Ebola, and COVID-19 public health response. She is also the director of the NIOSH Occupational Medicine Rotation Program. I'll turn it over to you, Judy. Good morning, everyone. Thank you for hanging in there with us. I just want to make sure are my slides visible? Hello? Can you see my slides? This is Aaron. I can see them, but I don't know if the people in the room can. Yes, we can see everything. We're good. There's really no way to communicate with you back and forth without interrupting the conversation. All right, then we'll just keep going on from here. So I will be talking this morning about heat-related fatalities and structural and wildland firefighters during training. So to start with, I want to tell you a little bit about the program. For 16 years, I was with the NIOSH Health Hazard Evaluation Program, and many of you may have seen some of our previous sessions here at AOHC, joining with OSHA, where we talked about our health hazard evaluations. This is a little different program where we specifically look at all firefighter fatalities. We are divided up into medical and trauma teams. The medical team investigates deaths due to non-traumatic events like heart attack and heat stroke, and we are based out of Cincinnati, Ohio, versus our trauma team. They look at traumatic firefighter deaths like falling through the roof, struck by a vehicle, entrapments, and things like that, and they are based out of Morgantown, West Virginia, through our Division of Safety Research. The way we find our cases, we are on the list from the U.S. Fire Administration. They send out fatality notices, and they get the notices submitted voluntarily by fire departments throughout the country. And once we determine which team that fatality would go under, we have a decision-making algorithm to determine which ones we investigate. And all of our completed case reports, just like completed health hazard evaluations, are posted on the NIOSH website. So just a quick outline of what I'll go over. First, a bit of heat stress definitions, which Dr. Butler has gone through a little bit. We'll do some basics of HRI prevention and some examples of these firefighter training-related fatalities, and then our recommendations. So just a quick review of heat stress and strain. Heat stress is a net exposure from all contributing heat sources. And this is sometimes the first step where people get tripped up a bit, is that it's easy to see a hot environment as a heat source, but oftentimes the contribution from metabolic heat due to exertion is often underestimated and underappreciated. And as we'll see in one of my examples here, you can get exertional heat stroke just from that. And it can happen in cool environments. And that's one of the reasons why I was happy to present today. We're still in spring, but yet we're going to be going into where people are going to be out doing a lot of sports and activities, and maybe not as aggressively as some firefighters, but we're still going to get that exertional heat contribution and it needs to be acknowledged and not underestimated. So heat strain itself, that's the physiological response to increased core body temperature, and it manifests as your heat-related illnesses. And as you know, heat stroke is the most severe form of heat-related illness, and it's solely characterized by a change in mental status, either in a hot environment or with exertion, and it can be fatal. And unfortunately, unlike these chickens, we don't have these nice pop-up buttons that tell us when we're getting into danger. And that's why education and training as to the early signs and symptoms of heat stroke are really important, as well as the preventative measures like the buddy system to help that be recognized sooner. So this is the HRI spectrum. I won't go through this since Dr. Butler did a great job of that, and you're all familiar with this, but really it's the important thing to take away from this is, you know, oftentimes the body doesn't read the book, and if it's looking like any type of heat-related illness, it has to be recognized the sooner, the better, and get them out of that environment, start the cooling down. So just a little bit about the relationship of heat-related illness and rhabdomyolysis, since that's what I've been concentrating on for a little while here, is oftentimes people are really focused on the issue of heat-related illness, but they forget how closely rhabdo can be tied with that. And as you all know, rhabdo has a laundry list of things that can precipitate it. Increased core body temperature is only one, exertion is another one, and then if you wind up with a seizure from heat stroke, you basically have involuntary exertion on top of that. So there's quite a few reasons why someone, if you're thinking might have heat stroke, might also be having rhabdo, and that should also be checked as well. So we always like to say that education about rhabdo should be included in the HRI training, and certainly in the 2016 update of the NIOSH criteria document that I showed on the last screen, I was able to contribute that information to our criteria document so that it's clear that there is a component of heat-related rhabdo. These are some educational materials that we developed from prior health hazard evaluations, and we have them for structural firefighters as well set for wildland firefighters, and they're all up on our website. We have a new rhabdo topic page that goes through and stores all these documents all in one place. So just to go over a little bit about the metabolic heat contributors for firefighters, and those who do not work with firefighters, either the wildland or structural, it's often can be underestimated all the work that they do and the exertion that they put themselves in at every single call. When you think of these, these are, this list here shows you some of what contributes to their metabolic heat generation. They have to climb ladders or stairs in the full turnout gear with the SCBAs. The turnout gear itself can weigh about 30 pounds, but the jacket and the pants, boots, and then you have the helmet, and then the SCBA tanks themselves are a good another, depending on the size of the tank, the duration of the air supply can be another 20 pounds or so. So now you put another approximately 60 pounds on a person and you're having them do stair climb, ladder climb, victim drag, and all that. That's for structural firefighters. With the wildland firefighters, as you see in the two pictures on the left, they can be going up very steep and ragged terrain, not just for a few hours, but for days or weeks at a time as they fight these huge wildfires. They can also be carrying a large amount of equipment. The chainsaw that you see in the left middle picture by itself is 25 pounds and they have to carry all their equipment in and out to these remote areas of the fire. So you are doing lots of prolonged intense exertion day in and day out. So they, as you can see, just by the exertion alone, generate significant metabolic heat. So these basic HRI risk reduction strategies work, but in order to work, you actually have to implement them consistently. Things like the buddy system, access to cooling stations, acclimatization protocol, work rest cycles, and when possible, schedule the outdoor task training and events during cooler months or at night. It's obvious with firefighting, you can't schedule when a fire happens. So you have to be ready to tackle it any time of the year, any time of day. But if we can possibly schedule these training programs to minimize their risk, it would be preferable. And also encourage rehydration with non-alcoholic, caffeine-free, and low and no sugar products. And that may be somewhat of a challenge with some of the enjoyment of caffeine our first responders have, but it's worth encouraging that. We also have seen that a lot of aggressive encouragement of rehydration in the fire service has been very successful, but we also need to keep at it. Especially now we're coming into the warmer months, it's sometimes easy to forget how much fluid they lose with their exertion. And so rehab areas like the one you see above are really good to see becoming more and more frequent. So the standards that the firefighters adhere to are those issued by the National Fire Protection Association or NFPA. And they have several different standards that refer to these issues. The main one here is the 1582 that looks at the comprehensive occupational medical program for fire departments, where it tells you first what they have to pass to get into the fire service and what their essential job tests are. And certainly, as you can see the last two bullet points below, they clearly recognize that this metabolic heat generation can and will probably put them into significant heat-related illness during the execution of their job duties. And adding to that, that they may not have the opportunity for rest and rehydration all the time at the ideal periods that we would like them to have. So they know they're going into a high-risk profession for this. As Dr. Butler was talking about, medical pre-screening is really important as far as minimizing risk of HRI. And they certainly recognize this in the standard, as you can see here. And not just for incoming firefighters, but incumbents are basically existing professional firefighters. So those who have completed their training and are actual working firefighters. So they actually are supposed to get a baseline medical evaluation after they get hired and then annually thereafter. And as you can see, this supposedly is to be focused on their occupational exposure risks. And unfortunately, there's no timeframe specified. And where this comes into play sometimes is with the cadets. And we'll talk about one of the cases in a minute where that came into play as far as the timeframe. So this is one of the HHEs I presented last year here, but just as a short summary, there was two cadets who went down with heat stroke and rhabdo the first day of training. And it turns out that this department was very large and there could have been a considerable delay up to two years between the time they get accepted, the time they get accepted, meaning that they had their initial medical evaluation and screening. And the time they actually were assigned a start date for their cadet course. And at that time, there was no requirement for a medical reassessment before they start training, regardless of that interim period that they were assigned to. And oftentimes, especially those who had a long wait time, they would get concerned as that start date would roll upon them, be worried they weren't in good shape and basically put themselves through these self-imposed pre-training boot camps and potentially put themselves into rhabdo right before they started their training course, thinking that they were getting themselves in better shape to handle their training. There was also at that time, no standardized method for assessing outdoor heat conditions, communicating those to the staff or basically any standard way of modifying the training for high heat conditions. Although individual instructors were doing that, there were no systematic guidelines on how that should happen. Going to our cases here, our fatality cases. So between the years of 2003 and 2016, NIOSH actually investigated 14 heat-related firefighter deaths. So this doesn't mean these are all those that happened. These are just the ones that NIOSH investigated. And 10 of these occurred during training events. So as you can see, it's really important to have that increased awareness increased awareness from the very start and not wait till they're done to really emphasize the dangers of heat-related illness. So the first one we're going to talk about occurred in during structural firefighter training in a survival house. And basically, these are houses that are rigged up to simulate what firefighters may encounter combating an actual structural fire. And that includes everything from entanglement props, as you see below, to simulate debris and other things that might trip them up inside the house. At the very bottom of that picture, you'll see the hose line guide that supposedly gets them through the maze. The interior is air conditioned, but there is a smoke generator used to decrease their visibility, like what would happen in a live fire, but no actual live fire in these houses. And there are monitor stations throughout the interior where instructors can keep an eye on the cadets and dive in and grab them out if needed. They have 30 minutes to complete the course using the hose line guide. So what happened with our first example, this was a 32 year old male structural firefighter cadet who really had no significant medical history. This happened in March of 2016 with the ambient temperature of 74, heat index was 75, so really not much humidity to complicate things. As I said, all areas of the house were air conditioned, and that set point was at 66 degrees Fahrenheit. They make it a little cooler to account for the heavy turnout gear and SCBAs that they know they're wearing. So at 0900, the cadet was in the staging area in his shorts and t-shirt. So even before he started getting geared up, he was reported feeling hot and was observed to be sweating, but still started the course about an hour and a half later in his full gear on air with his SCBA. At 1115, the instructor heard the cadet stop moving, and he actually missed the exit. And even though he went right through the trapdoor access to get a hold of him, by then he was already pulseless and hot to the touch. He was quickly extricated from the house, PPE and clothes removed, CPR initiated, cold packs placed, ALS was not on site. They arrived about 15 minutes later, and he was intubated and cooled the IV fluids. However, despite these measures, by the time they got to the ER, his core body temperature was 109. Resuscitation was unsuccessful, and the cause of death was listed as exertional heat stroke. So as I was saying, that it's really important not to underestimate that even in cool weather, you can get exertional heat stroke if you're doing a lot of exertion very intensely for a prolonged period. So the recommendations that we had for this was, it was somewhat concerning that the heat-related illness he had before he started, if he's already in, just in a t-shirt and shirts and complaining of being hot and sweated, that that wasn't recognized right there. And then that, you know, this guy maybe is already in trouble, we shouldn't have them go through the course. And part of that is this idea of reducing barriers and changing culture, because there's a very fine line a lot of these supervisors walk between wanting to encourage these cadets to push hard, to exceed their expectations of themselves, dig deep, that whole mentality, while also trying to keep an eye out for those who may actually be in medical trouble. So it is difficult. And again, we've got to increase that awareness that it's okay to report, it's okay to step back from training. And it's just as important as completing the event, as it is to take care of yourself. One of the other issues we noticed that there was no ALS on site during training, and certainly the time taken to get a unit there may have impacted the outcome. We don't know, but that was something we also wanted to recommend, that perhaps if there had been an ALS unit on site, maybe when this cadet was noted to having heat-related illness before he started, maybe they could have done an assessment and pulled him at that time. And also having it on site would allow for a rapid initiation of treatment and transport. Going to the wildland firefighters, there are three basic duty levels. And as you see on the screen here, I'm not going to read it. There are arduous, moderate and light duty levels. And each of them have a correspondingly difficult work capacity test, which is also known as their pack test. So as you get up in difficulty, so does the test. And as far as the duration that you have to complete as the time you have to do it in and the amount of weight you have to carry to do it. So one of these wildland firefighters failed at his first attempt. He only finished it in 55 minutes. And as you can see, depending on his duty, he had the most he could take, depending on his level was 45 minutes. So he didn't make any of these categories. And that was at early morning, it was only 74 degrees out with ambient temperature. So he had the next day to rest, which actually was not rest much at all. He spent the entire day clearing brush all day with his crew in an ambient temperature that went up to 95 degrees Fahrenheit. He was allowed to do a second attempt on this pack test the following day. So again, they started out early in the morning at 7.20. It was 78 degrees ambient temperature then. And 40 minutes later, he collapsed a hundred feet from the finish line. He couldn't stand, but he was still responding to questions from his crewmates. They moved him to a shaded area and started applying the cold packs. Dispatch was notified shortly after an ambulance departed, but he became unresponsive and then pulseless en route. And unfortunately resuscitation was unsuccessful. The cause of death was listed as hyperthermia and probable dehydration due to physical exertion due to the prolonged transport time that they didn't, we can't really know what his core body temp was at the time, but it was expected to be significant. He did have some HRI risk factors, as we talked about a pre-screening for medical conditions that would put you at increased risk. He was obese as per his BMI was over a 30 definition. And he also had recently arrived to Arizona from Colorado, just four days before doing this pack test. So he really didn't have the ideal two weeks of acclimatization before doing this activity. And he was cleared for his arduous duty in May, 2015. So about a month beforehand. We recommended that, again, to ensure cadets are acclimatized prior to the pack test, especially when they're coming from all over the country, not just being drawn from the local population. And we needed to improve heat-related illness, educational and assigned symptoms, and initial management of heat stroke. And there was a question about whether having an ice bath available may have impacted the outcome. So that was also brought in as another recommendation, especially when we know these were a group of arduous duty wildland firefighters doing the most difficult pack test with the highest weight. So what did we learn from all this? The take-home points are here, is that exertion and exposure to heat are unavoidable occupational exposures to both structural and wildland firefighters. And heat-related illness and heat stroke can and does incur in these firefighters solely due to the metabolic heat generation from exertion. So even in cooler weather, like we have now, it can and will happen. And even in air-conditioned indoor environments, it can and will happen. So we just have to have that increased awareness of the signs and symptoms and not be so quick to dismiss these symptoms. And that especially holds true as we move forward to the hotter months of summer, but then people tend to have a higher awareness when it gets hot outside that they're more inclined to think of heat stroke rather when it's not so much of a hot environment. We wanna work in basic HRI prevention methods, and they only work if you actually take them from the heat stress management protocols and apply them consistently. And although culture is hard to change, we have to try to do it in order to lower these barriers to reporting, to make it okay to step down when you're not feeling well, and to take that step back from training if you need to. So that's a very hard and long process, but we have to start somewhere. And that's all I had. Thank you very much. So I will stop sharing now, and let me introduce the next speaker that we have. It is Dr. Aaron Tustin, who graduated from Vanderbilt Medical School. He then completed an internship in pediatrics at the Johns Hopkins Hospital and a residency in occupational and environmental medicine at Johns Hopkins Bloomberg School of Public Health. From 2016 to 2021, he was a medical officer at the Occupational Safety and Health Administration, and much of his work at OSHA focused on the epidemiology of heat-related illness. Dr. Tustin is a board certified in occupational medicine, and he is a fellow of ACOM. Dr. Tustin, please take it away. Thank you, Judy. Thanks for that introduction. Today, I will be discussing an emerging problem, heat-related kidney injury that has implications for worker health, both in the U.S. and abroad. I don't have any financial ties or conflicts of interest to disclose. In the interest of full disclosure, I just note that this work was performed while I was a medical officer at OSHA, but I am no longer an employee of OSHA. And before I start, I'd just like to thank Jason Glazer and the La Isla Network for providing some of the background slides that I'm about to show about chronic kidney disease. So let's jump right into some of that background material. First of all, this project that I'll be discussing is an epidemiology study of acute kidney injury, abbreviated AKI, that is due to heat stress. AKI is defined as a short-term, temporary decline in kidney function. And AKI is often diagnosed by elevated serum creatinine levels that return to normal within a week. And the reason for this is that serum creatinine levels that return to normal within a week. So like I said, it's temporary and it resolves. That's the definition of AKI. And there are many causes of AKI in general, but one of these causes is occupational heat stress. When workers are exposed to environmental heat and heavy physical activity, they can develop kidney injury through various mechanisms, such as dehydration, which can cause volume depletion and pre-renal kidney injury, or hyperthermia, which can damage kidney structures, or rhabdomyolysis, which is the breakdown of skeletal muscle that Judy already talked about that releases chemicals such as myoglobin that can harm the kidneys. And throughout the remainder of this talk, just so you know, I will use the acronym HRAKI to refer to heat-related acute kidney injury. So why worry about AKI if by definition acute kidney injury is temporary and it resolves? Well, there are several very good reasons to worry about it. One of these is that AKI has shown to be a risk factor for subsequent development of chronic kidney disease, or CKD, which is a long-term ailment with substantial morbidity and mortality even due to end-stage renal disease. And this quote on this slide from a New England Journal article about the interconnectedness of AKI and CKD makes the point that there is a strong association between the two. In the next few slides, I'm going to show some background information about the phenomenon of what's called CKD-NT, which stands for chronic kidney disease of nontraditional causes. Although my research project is about AKI and not CKD-NT, I want to provide this background information to motivate an understanding of why cases of heat-related AKI in the United States need to be taken seriously. CKD-NT is an epidemic that's affecting many people, but mostly young male agricultural workers in equatorial regions such as Mesoamerica and Sri Lanka. The disease is called CKD of nontraditional causes because although these workers develop chronic kidney disease, they do not have traditional kidney disease risk factors such as diabetes or hypertension. Unfortunately, CKD-NT often progresses to end-stage renal disease. And this epidemic of CKD-NT has claimed the lives of tens of thousands of workers since this entity was discovered in the 1970s. Currently, CKD-NT is the subject of much research globally and also interventions to protect workers. And so if you're not familiar with CKD-NT, I would direct you to some of the excellent epidemiology studies and also review articles that others have written. Just briefly though, as I mentioned, CKD-NT is different than traditional chronic kidney disease in several ways. Traditionally, CKD affects older individuals who have other chronic diseases like diabetes and hypertension that can damage the kidneys. CKD-NT, on the other hand, primarily affects younger males who have none of the traditional risk factors. And CKD-NT is a disease that's associated with occupation, performing strenuous physical labor in hot environments, often in sugarcane cutting or other forms of agriculture is an important risk factor. Although other occupational and non-occupational risk factors are also being explored, there is a substantial amount of evidence to suggest that occupational heat stress can lead to CKD-NT. Interventions that reduce heat stress, such as providing shade and rest breaks and potable drinking water, can also reduce the incidence of adverse kidney outcomes. Unfortunately, the incidence of CKD-NT is increasing in places like Costa Rica, where mortality rates from this disease are highest in areas that cultivate sugarcane. And these areas tend to be hot. And in fact, I mentioned sugarcane cutting a couple of times. Sugarcane cutting is one of the industries that researchers think is one of the highest risk for development of CKD-NT. Not only do sugarcane cutters labor in hot conditions, but the work is physically demanding. Shifts can be of long duration and the physical activity level is high, which generates considerable metabolic heat load in these workers. Then on the final background slide, before I begin to talk about my own study, I want to just reiterate why I am spending so much time on CKD-NT and to talk about acute kidney injury. And again, I just reiterate that epidemiology studies have shown that workers who develop heat-related AKI are at risk for later development of chronic kidney disease. This slide is about a prospective study from Nicaragua that identified almost 50 agricultural workers who developed chronic kidney disease after having experienced an episode of acute kidney injury during the harvest season. Alarmingly, most of these workers were younger than 35 years old, and most of them had moderate to severe chronic kidney disease at the time of diagnosis. Okay, now let's dive into the US-based acute kidney injury study that my co-authors and I performed. We attempted to count and characterize hospitalizations for heat-related AKI among US workers in a variety of industries, not just agriculture. To do so, we performed a retrospective analysis of cases found in two databases maintained by the Occupational Safety and Health Administration, or OSHA. The primary database was the Severe Injury Reports, which I abbreviate SIR in these slides. By law, since 2015, employers have been required to report work-related hospitalizations to OSHA. The SIR database is publicly available, and it contains information about each of these reports. The secondary database that we used is abbreviated OOMN, which stands for OSHA's Office of Occupational Medicine and Nursing. OOMN is a group of physicians, nurses, and health scientists who assist OSHA with medical and epidemiological investigations. We examined OOMN case files from investigations that the office performed during approximately the past decade. SIR was our primary database because it is larger and more comprehensive. SIR is a semi-national surveillance database because reporting of work-related hospitalizations is mandatory for employers who are under the authority of federal OSHA. At the time when we performed this study, SIR contained more than 57,000 incident reports. SIR provides variables such as the date, location, and industry, and also a short narrative description of what happens to each worker. Of note, however, SIR does not contain some demographic variables such as age and gender, nor does it contain medical records or serum creatinine values. The OOMN case files did contain medical records. So for this study, we created three different case definitions to reflect how confident we were in the diagnosis of AKI. The highest confidence case definition is called confirmed HR AKI. And this was possible only in the OOMN dataset because it refers to heat-related hospitalizations where we had medical records to verify that the worker's serum creatinine values and the rise in serum creatinine met K-DIGO criteria for the diagnosis of acute kidney injury. These criteria are based on the magnitude of the absolute or relative rise in serum creatinine from baseline. The other two case definitions were ascertained in the SIR database, which, as I mentioned, contained narrative descriptions of the hospitalizations, but not serum creatinine data. When these narratives explicitly stated that the workers had AKI, we assigned a case definition of probable AKI. And additionally, based on our own clinical investigations at OOMN, we knew that workers who are hospitalized with heat-related dehydration or rhabdomyolysis often have acute kidney injury also. So for this reason, we assigned a case definition of possible HR AKI in those situations. Our statistical analyses involved first simply counting how many workers met each case definition. We then stratified these counts by industry and worksite location because we wanted to determine how many incidents occurred outdoors versus indoors. We also computed incidence rates by industry, for which we used U.S. Census Bureau data to determine the number of workers in each industry. And finally, we performed a so-called capture-recapture analysis, which is a way of assessing the completeness of a surveillance database when there is another overlapping database to which one can compare it. Because there was some overlap in the cases in the OOMN database and the SIR database, we were able to estimate how complete the SIR database was. This map shows in gray the states where federal OSHA has jurisdiction over most private employers. To a first approximation, these gray states are the areas that are included in our study. OSHA databases have limited ability for surveillance in the white areas, so our study included few cases in those states. Of note, this geographic restriction has some implications, such as the fact that most occupational AKI cases in California were outside the reach of our two databases. And this is a substantial limitation because California is the most populous state and it is also home to a lot of agriculture. Okay, now I'm going to move into some results. The next few slides are about the results of the study, this retrospective case series. First of all, the number of cases that we ascertained is on this slide. The primary database, SIR, like I mentioned, it had 57,000 records in the raw database of which about 1,400 were heat-related hospitalizations. And of those, 586 met our case definitions for either probable or possible heat-related AKI. The secondary database, OOMN, was much smaller, comprising 141 heat-related illness investigations of which 22 cases were confirmed to be HR AKI hospitalizations. And after accounting for the overlap between these two databases and to remove the risk of double accounting, we found that the grand total was, we ascertained 608 hospitalizations were confirmed or suspected heat-related acute kidney injury in workers in the United States. And most of these were between 2015 and 2020. When we examined the location of the work sites, we found that about half of them were strictly outdoors. And furthermore, about a quarter of the affected workers were performing tasks from a vehicle, such as delivering mail or packages or collecting solid waste in conjunction with a garbage truck. And another quarter of affected workers developed heat-related acute kidney injury while working indoors. Ours is one of the first studies to report indoor heat-related acute kidney injury. So this appears to be an under-recognized phenomenon. Because of that, I wanted to go into a little bit more detail in this talk about the indoor cases. Some people are surprised to learn that indoor workers can experience high levels of heat stress. We identified AKI cases in several types of indoor facilities, the most common of which was manufacturing. The glass bottle plant is pictured here, but there were also other cases in other indoor manufacturing facilities that manufacture things like metals or plastics. Also, indoor cases occurred in restaurants where some kitchen areas might be hot or steamy, residential attics which are not climate-controlled, bakeries which obviously have hot ovens, smelters and foundries, and warehouses which are often not air-conditioned. So one conclusion is that workers in some indoor industries need heat stress protections because they are at risk of kidney injury or other adverse outcomes like other heat-related illnesses. When looking at the map of where these cases occurred, I suggest focusing your attention primarily on the gray states where federal OSHA has the most jurisdiction. Like I said, these are the states that have the most coverage in our databases. Within these gray areas, we found most of the hospitalizations occurred in southern states like Texas and Florida. The reason for this finding is probably that these states are both hot and populous. However, we found heat-related AKI hospitalizations as far north as North Dakota and Maine. So stakeholders should recognize that pretty much every state in the country has summer weather that can be hot enough to cause heat-related AKI or other heat-related illnesses in workers. This chart provides some additional demographic and clinical information about the 22 confirmed heat-related AKI hospitalizations for which we had medical records. By and large, these patients were males with a median age of 41 years. 40% of these hospitalizations occurred during the first week after a worker had just started a new job. Prior studies have also shown that newly hired workers are overrepresented among other heat-related illnesses such as fatal heat stroke. These consistent results highlight that new workers are at high risk of many adverse health and safety outcomes. These data suggest that a large percentage of heat-related acute kidney injury cases might be prevented if employers would provide extra protection to new workers and allow them to acclimatize to heat stress gradually. Almost wrapping up, I have a couple more slides. This one shows the 10 industries organized by six-digit NAICS codes that had the highest incidence rates of heat-related AKI in our study. When we examined these data, a couple of patterns became evident. These red boxes show that four of the top 10 industries have workers who do a combination of manual labor while driving or riding in a vehicle that may not have air conditioning. Specifically, I'm referring to solid waste collection, mail and package delivery, and local deliveries using trucks. The second pattern, shown in these blue boxes, is that there were high incidence rates of heat-related AKI in several construction industries such as highway and bridge construction, concrete foundation pouring, and power line construction. Finally, as mentioned, we performed a capture-recapture analysis to assess the completeness of the SIR database. This Venn diagram shows that of the 17 confirmed HR AKI hospitalizations in the OOMN database that should have been present in SIR, only one case, or 8.3%, was actually reported to SIR as a heat-related AKI diagnosis. The other 92% of the AKI hospitalizations either were not reported to SIR at all, or they were reported only as some nonspecific illness like heat exhaustion, so the report did not give any indication that the worker had also suffered acute kidney injury. In conclusion, our retrospective analysis of two OSHA databases identified over 600 U.S. workers who were hospitalized with confirmed or suspected heat-related acute kidney injury in recent years. For several reasons, this count is probably only the tip of the iceberg. One reason is that our study included only illnesses that were severe enough to require inpatient hospitalization. For each hospitalization, there were probably several other workers who suffered subclinical kidney injury or who were treated and released without being admitted. Furthermore, we were able to cross-reference the two databases to show that there was a high rate of underreporting and failure to report. For these reasons, we believe that the actual number of U.S. workers who have suffered heat-related AKI in recent years is likely much higher than what we have reported here. And I also reiterate that heat-related AKI happened in many outdoor and indoor industries, not just agriculture. There are many industries in the U.S., including large sectors like the construction sector and the mail-and-package delivery sector and the manufacturing sector, where workers are at risk of acute kidney injury and possibly subsequent progression to chronic kidney disease. So that's why I believe that more research and surveillance are needed in the United States to determine the true burden of both acute kidney injury and chronic kidney disease due to occupational heat stress. Thank you very much for listening, and I believe we're holding questions until the end, but I just note that my slides have a bibliography at the end for anyone who's interested. You can download the PDF version and look at the further reading. Thank you. Thank you very much, Aaron. Our next speaker is Dr. Kristen Eumann. She is a medical epidemiologist with the CDC's National Institute for Occupational Safety and Health, or NIOSH. Since joining NIOSH in 2013, she has worked on studies to understand health issues among minors and other high-risk Western occupations. She is currently the principal investigator of a study to assess the performance effects of heat stress among minors. Thank you, Judy. Good morning, everyone. Just for the last few minutes, I'm going to talk about our work on heat strain and mining. This will only take a few minutes. I'm going to make sure that you get out on time and that we do have a few minutes for questions. I'm going to talk about why we're focusing on heat strain and mining and provide a very brief overview of our heat stress studies. Why are we focusing on heat strain? We are, of course, concerned about the risk of heat illness, but as you have heard, there are other health and safety consequences. You've already heard about the kidney disease and rhabdomyolysis associated with heat strain. There are also multiple studies that have demonstrated associations between heat strain and worker injuries. Although the mechanism underlying this association is not precisely known, it's thought to include a combination of fatigue, thermal discomfort, psychomotor, and cognitive decline. Heat strain research is especially important in mining given that underground mines are expanding to deeper, hotter levels and heat waves affecting surface mines are expected to increase. This is an example of a local underground mine that has expanded to deeper levels recently with increasing rock temperatures. As the mine has expanded to deeper levels, it becomes hotter for the workers working in these levels. Despite the increasing impact of heat exposure on mines and the effects of heat strain on health and safety, we don't actually know how much of a problem it is in U.S. mining because it's not generally reported. So we need more effective monitoring and prevention of heat strain, and we need a better understanding of all heat-related impacts on workers, not just heat illness, and this includes the effect on worker performance and injuries. I am going to move through these slides. This just talks about a pilot study that we did that showed that in a local mine, the miners in the study had elevated core body temperatures multiple times throughout their shifts. And one of the things that this points out is that a lot of the standards and recommendations out there don't really account for individual variability. We don't know what the impact of short versus long-term or intermittent versus continuous elevated temperatures are. We don't know if there are acceptable durations of different heat intensities. And in our pilot, we saw that core body temperatures exceeded 38 degrees Celsius several times for short periods of time. And so we need more information on what the impact of these different patterns of heat exposure are. So our research aims to evaluate several objectives. First, we want to better characterize what core body temperature patterns actually look like in mining. For instance, how often during a shift do miners reach certain core body temperatures and for how long? And are current standards relevant given the patterns that we see in mining? So we'll approach this objective by mapping out core body temperatures among miners when they're doing their normal tasks and their normal shifts. We want to know if their body temperature fluctuates or if the temperature remains elevated for long periods. We also want to look at how heat exposure affects worker cognitive performance, given that this is likely a contributory factor to the association between heat exposure and injuries. Can we predict when heat begins to affect performance so that we can prevent the more adverse outcomes associated with heat strain? And we will also want to look at how individual variability plays a role in the physiologic and cognitive effects of heat. We're approaching these study objectives through a dual arm study that involves both an environmental chamber component and a field component. And in both components, we will monitor heart rate and core body temperature. In the environmental chamber, participants will complete exercise followed by cognitive tests at normal and elevated core body temperatures. In the field, participants will conduct their normal tests while on shift and will complete a brief cognitive assessment using a smartphone app when their core body temperatures are normal, and again when they're elevated. We'll use the results of this study to provide guidance on how best to monitor miners for the adverse impacts of heat strain on cognitive function, as well as determine future directions for NIOSH mining heat strain research. So in summary, heat strain is an important issue in mining and can not only lead to heat illness, but other adverse outcomes such as injuries. And we're conducting research on the effects of heat strain on cognitive performance so that we can provide guidance on monitoring workers. Our research will also provide information on common patterns of heat strain seen in miners so that that will help us focus our future heat strain research. And if any of you work with any mines that might be interested in this, please feel free to reach out. For your awareness, we do have six different fact sheets available on different aspects of heat strain, and they're available at the website provided here. And they're not just mining focused, so you can use them for other industries as well. Thank you for your attention. Thank you very much, Dr. Nolan. We have a few minutes to take some of the questions from the chat box. I saw that there was one question for me, actually. What do you recommend as the best way to measure temperature in firefighters who are at an active fire scene? One of the standards I didn't get a chance to quote from was NFPA standard 1584, which actually focuses on the rehab process during fire suppression events. And in short, it's important to remember with heat stroke, as we said, it's a clinical diagnosis. It really doesn't matter what their temperature was. If they're showing symptoms, you treat them as such regardless. That also is compounded by the fact that it's really hard to get a good oral temperature, especially when you're trying to force cool liquids down them. You're not going to get an accurate temperature. So panic has its own limitations as far as accuracy. And really, as far as the NFPA standard goes, they're just, you know, just look at your vitals, your heart rate, your blood pressure, pulse ox. And as you normalize their body temperature, those vitals will normalize as well. So, unfortunately, there really isn't a good way to get an accurate body temperature on them. You know, if they're sick enough and they have heat stroke and they're going to the ER, as soon as they get to the ER, they're going to have a rectal temp done. And that's not happening anywhere other than the ER. So, really, the best way to measure how successful you are with cooling the firefighter is looking at their other vitals, such as the heart rate and the blood pressure and pulse ox. I do not see any other questions. Are there any other? If there's any questions in the room, we do have a microphone up at the front. Hi. Thank you. My name is Dr. Andrew Jeremijenko. I'm from Australia, so we have a lot of people working in very hot environments in the northwest of Australia. We are actually very good at studies, and I was actually impressed by the numbers of AKI that you identified that were heat-related. I am looking at wearable technologies. There's obviously all sweat monitors out there, but we're looking at a microneedle that measures impedance. To look at dehydration intracellularly and extracellularly. It's hard words to say. I'm just wondering, have you thought or have any of the researchers there thought about using that sort of wearable tech to measure things like hydration and interplay? There is some wearable technology that's being studied now dealing with heart rate, pulse, blood pressure. But we're talking about actually the actual biochemical impedance through skin needles. Okay. I know nothing of that. We've not found it in our research. All right. And the researchers can't hear me? Sir? Dr. Eisenberg, as far as the prior studies I've looked at doing heat stress and rhabdom with firefighters, we actually had them do ingested core body temperature sensors each day. Wear a heart rate strap around their chest. The problem with a lot of these wearable tech, especially when you're looking with firefighters, they are brutal on any tech they wear. We actually had to change out the heart rate monitor straps because they were getting stretched and pulled so much you weren't getting good contact with the skin by virtue of the types of exertion that they were doing. So it creates a challenge on finding what can work well in that particular workforce. But it's an interesting idea you bring up. So thank you very much. By the way, for the blood work, we actually use the Piccolo Express. It does, on a finger stick of blood, three to six drops of blood, it runs a cartridge that does a full basic metabolic panel as well as serum creatinine kinase. And the BMP also gives you the numbers that you need to calculate your serum osmolarity as well as your bu and creatinine. So we use that both for the rhabdo check and for the hydration status. So that was a nice sort of way to get those numbers for us. Thank you. Okay. And this is Aaron Tustin. I'll just comment briefly because you mentioned my AKI study. I'm not really an expert on wearable technologies. That's not really my area. So I can't really comment too much on that. But since you mentioned dehydration, I would say that to me it seems like a good idea to try to measure hydration or dehydration status because actually something I didn't mention in my talk. But in the 22 cases of heat-related AKI for which we had medical records, the treating clinicians diagnosed all 22 of those workers with dehydration as well as AKI. So I wouldn't really say that these were objective diagnoses necessarily based on much subjective information. But it does seem like dehydration, at least in our study, was closely associated with the development of AKI. So if there were some validated way to measure hydration status in real time, that could be useful. All right. Thank you. Ma'am. Good afternoon. I think this question is for Dr. Tustin. Okay. Austin, you're up. Yes. Or Aaron, I mean. It's a quick question. I will say that. What does capture and recapture analysis mean in your statistics session? You have that in one of your slides. Thank you. Yeah, thanks for that question. Sorry if I didn't go into too much detail about that. But the terminology capture and recapture originally comes from kind of biology or ecology studies of populations of animals where they would capture certain animals and tag them and release them. And then later, if you go out and, again, capture a random sample of animals in the same area and figure out how many of them had tags on them, you can kind of figure out the size of the entire population. Eventually, that terminology got adapted to epidemiology. So as far as epidemiologists are concerned, it refers to a study where you have two different databases that are both trying to measure the same outcome. So for our study, we had two different databases that were trying to ascertain cases of acute kidney injury. So we're kind of capturing outcomes in one database. And then we're looking in the second database, which is kind of the recapture database. And we're trying to figure out how many of the cases are also in the second database. And so by doing that, I can send you some articles if you contact me. But by doing that, you can ascertain kind of how complete your databases are just using some simple mathematical and statistical techniques. Any other questions? Okay. Well, we thank all of you for being here and for those online. Have a good lunch. Thank you, Judy and Aaron.

Dr. Timothy Butler

heat-related illnesses

firefighters

occupational exposure to heat

prevention guidance

acclimatization protocols

work-rest cycles

engineering controls

administrative controls

heat stress prevention program

signs and symptoms

heat strain