During this presentation, we will discuss and review the assessment of physical hazards. Topics we will cover during this presentation include ergonomics, vibration, ionizing and non-ionizing radiation, noise, high and low temperature, and high and low pressure. So let's start with a review question. A 50-year-old mechanic plans to lift a 100-pound wheelbase two feet off of a horizontal worktable. The RWL, or recommended weight limit, as determined by the NIOSH lifting equation, will calculate the maximum weight that this worker can lift safely. Is this a true statement or a false statement? The answer is that this is a false statement, and we will review the basis for this answer as we go through the slide presentation together. The scope of ergonomic stressors is broad and includes the following, repetition of a task, static exertion, for example, holding an object over your head or grasping something continuously, applying force, for example, pushing an object, localized contact or pressure, for example, leaning on your elbow, posture, which can encompass a variety of postures, including but not limited to standing or sitting or squatting, vibration hazard, for example, when using vibrating tools such as a jackhammer, as well as cold temperature. The following are key determinants for ergonomic evaluations. We need to know the purpose of the job, that is, what is the desired outcome of the task. We need to know a description of the task, for example, assembly of a given object or quality checking objects. We need to be aware of production standards. For example, is the desired object of a certain size or of a certain number or quality? We need to be familiar with work objects, things that would be manipulated by the employee that can include tools and equipment used by the employee in the task. We need to know the configuration of any workstation used by the employee. We need to be aware of work methods or processes used to accomplish the desired task, and we need to be aware of the environment in which the employee is working. For example, is this an indoor or outdoor environment? Is this an enclosed environment or an open environment? This slide illustrates some of the tools we can use to assess mechanical stressors during an ergonomic evaluation. To prepare, we can certainly do background research, including a review of pertinent literature. We should interview personnel, including workers, supervisors, and occupational health personnel to become aware of processes, quality, and production standards, as well as any trends in reported musculoskeletal disorders that could be related to exposure to ergonomic stressors. We definitely would be observing the tasks at hand, and we can record our observations directly via taking notes. We can record and view videos, and we can take photos. Generally, all three of these methods would be used currently in order to perform an ergonomics evaluation. We can perform calculations based on our measurements, and we can certainly use instruments, including accelerometers, goniometers, and other instruments, and a goniometer is illustrated here on this slide on the right side. Potential components of an ergonomics program include recognition of the problem, performance of a job analysis with the goals of identifying and evaluating causative factors, worker involvement, injury reporting of potential work-related musculoskeletal disorders, abbreviated here as WRMSDs, and provision of appropriate health care, including evaluation and treatment for any work-related musculoskeletal disorders that are noted. Examples of ergonomic controls include those in our usual hierarchy, beginning with most effective or engineering controls, which can include vibration-reducing seats, vibration-reducing tools. When we think about vibration-reducing seats, we could think about the seats on commercial buses where you have that accordion-pleated type apparatus underneath the driver's seat that absorbs the axial stress from hitting bumps in the road. We can also mount tools on the ceiling or in other areas so that they are easily accessed by employees. We can implement engineering controls into overall workstation design. And when we think about health care, to the right here, you see an example of a teddy bear in lieu of a patient being lifted by an overhead hoist. So for our bariatric or morbidly obese patients, this can reduce the lifting hazard on our health care workers. When we look at administrative controls or the next effective in our hierarchy, we can use rules or policies to have a work rotation for repetitive tasks to reduce the time that any one worker is exposed to a given task. We can restrict work during cold temperatures where vasoconstriction could put employees at higher risk of musculoskeletal injury. We could also implement lifting teams in health care settings, although as our patient population grows larger, so to speak, with the obesity epidemic in the United States, this is becoming rather impractical. Our third line of defense, as you know, when it comes to industrial controls is personal protective equipment. In this category, we have tools such as vibration dampening tools and vibration dampening personal protective equipment, such as vibration absorbing or dampening gloves. Let's go back to our introductory question and talk a little bit about the NIOSH lifting equation. The NIOSH lifting equation is a theoretical equation that takes into account the weight of an object that should be lifted by a worker, in addition to several other variables involved in lifting tasks that could contribute to the risk of injury. So for example, if a worker is to lift something very frequently or to lift loads located far away from the body, there would be an increased risk of injury. This equation adjusts weight downward from a baseline weight, also referred to as the load constant of 51 pounds, down to a recommended weight limit or RWL. Theoretically, the RWL is the weight of the load that nearly all workers could perform over a substantial period of time, for example, a work shift, without an increased risk of developing a work-related case of low back pain. The baseline weight or the load constant, 51 pounds or 23 kilograms, was established by NIOSH. So you can see that this equation really isn't practical or useful for weights over 51 pounds. Under ideal conditions, this equation determines the safe lifting weight for up to 75% of females and 90% of males. This slide illustrates the lifting equation along with the multipliers or modifiers that represent different facets of a lifting task. On this slide, we can see different illustrations of the types of ergonomic stressors included in the lifting equation. So for example, on the right side of the slide, you see the force multiplier, which could reflect the weight, the couplings multiplier or CM, which is used to express the type of handles or couplings that a worker is grasping, distance multipliers and vertical multipliers, both above the horizontal plane and from the floor to approximately waist level, and the horizontal multiplier measuring the distance from the center of the worker's body to the point at which the object is being lifted. On the left-hand side of this slide, you can also see a rotational degree of 90 degrees from where a worker needs to pick up an object to where the worker is releasing that object during a given task. So once you have your recommended weight limit or RWL, then you can use that to calculate the lifting index. And the lifting index is a ratio of your load weight or the actual weight that the worker would be manipulating divided by your RWL. So let's understand this better using the case. Here illustrated, we have a daycare worker who needs to lift a 20-pound kiddo up to a changing table. The recommended weight limit for this task, as calculated by you, is 40 pounds. What's the lifting index for this task? Well, the correct answer would be 0.5 because your actual weight or your load weight is 20 pounds, and your recommended weight limit or RWL is 40 pounds. So the correct answer is C. Occupational exposure to vibration can affect a part of the body, such as the upper extremity and or the entire body. And when we're talking about the entire body, we're generally talking about the axial skeleton. For segmental or hand-arm vibration, a hand-arm vibration syndrome has been described, and this has also been called vibration whitefinger or occupational Raynaud's disease. This consists of vasospastic and neuropathic symptoms that result from prolonged exposure to segmental vibration. Our usual hierarchy of controls, including engineering out the hazard or implementing use of a floor or other technology that absorbs the vibration, administrative controls, including limiting an individual worker's exposure to a particular tool or process, as well as personal protective equipment, which might include vibration-dampening or vibration-absorbing gloves. Workers that are at higher risk of exposure to total body vibration include operators of vehicles, such as buses and trucks, drilling apparatus or industrial machines, and jackhammers, such as the worker illustrated in the photo at the upper right-hand corner of this slide. This worker would actually be at risk of both total body vibration from the vibration of the jackhammer and its transmission to the axial spine, as well as hand-arm vibration from holding onto the tool. The same hierarchy of controls would be useful in reducing exposure to this hazard. And in the case of vehicle operators, vibration-dampening seats are one method of absorbing the stress on the axial spine. In addition, building surfaces and other tools that could be used to reduce the translation of the vibration to the axial spine might be helpful. Although the site is no longer being updated, the CDC still maintains a site for the NIOSH occupational dermatology slide library. This particular slide illustrates the skin blanching that is consistent with the condition of occupational rhinos or vibration whitefinger that we discussed on the previous slide. I've included a link to the slide library, as it is a valuable resource both for review and for your future teaching. And many of the slides that we'll show you during this course are from this repository. As we transition into the next part of our discussion of physical hazards to a discussion of occupational and environmental noise exposure, let's look at some typical activities and sound-producing machines like a power mower or a refrigerator and their corresponding sound pressure levels. Keep these levels in mind as we go through the rest of the presentation. You can see that listening to a personal stereo at maximum volume or even operating your own power mower can be associated with some significant noise exposure. When reviewing the information on this slide that describes some of the health effects of environmental noise exposure, you may want to toggle back to the previous slide where you'll remember that 110 decibels is a typical sound pressure level for a rock concert. And that although at 85 decibels, prolonged exposure to any noise at or above this level can cause gradual hearing loss. Remember that our backyard power mower can generate sound levels around 90 decibels. There are several tools and methods that can be used to measure ambient noise levels. We can use personal monitors called noise dosimeters, which are, and I'll date myself again here, like a little radio or a Sony Walkman that one would attach to an individual worker that would read and record sound pressure levels that most likely correspond with that worker's individual exposure. To measure the sound pressure levels in an area over time, we can design a monitoring strategy using sound level meters and then use that information to predict the expected noise exposure for a similarly exposed group of employees. Using noise mapping, we can locate different levels of noise from this data and we can use octave band analysis to take a large number of frequencies and analyze that so that the measurements more accurately reflect those noises in the sound pressure level range that is in our audible range for human hearing. To understand the physiology of noise-induced hearing loss, let's review the anatomy and mechanism of transmission of sound to the inner ear. The external ear canal functions as a type of funnel, collecting sound pressure waves and funneling them towards the tympanic membrane or eardrum. Vibration of the tympanic membrane is translated to vibration of the three ossicles, the auditory bones in this slide. That sound pressure wave is then conducted into the cochlea and the semicircular canals through the oval window, causing a motion of the hair cells that reside on the cochlea. These hair cells are based in nervous membranes and motion of the hair cells is translated into a neurochemical signal that ultimately results in the perception of sound through the auditory nerve. Disruption to the cochlea, the tympanic membrane, the ossicles, or the oval window can all result in a hearing loss. The hair cells in the cochlea are resting on a frequency-included basilar membrane. And what that means is that each hair cell and each point on that membrane corresponds to perception of a particular sound frequency. Again, when the cilia are moved, that is translated into a neurochemical signal. Noise-induced hearing loss is most frequently seen initially at the 4,000 hertz level. And in the next photos, I'll show illustrations which will help to cement your understanding of why we first see noise-induced hearing loss at this frequency. This first slide is the one of a pair that shows the hair cells as arranged in the cochlea. Note the hair cells on the right-hand side closest to the oval window. And as you look at these two slides, you might want to toggle between them. At the risk of dating myself, this slide illustrates your hair cells in your cochlea. And the next slide illustrates your hair cells in your cochlea on high-level occupational or environmental noise. And again, at the risk of dating myself, this slide illustrates the hair cells in the cilia on high-level occupational or environmental noise exposure. You can see by looking at this slide, and I do encourage you to toggle back and forth between the previous slide and this slide, that the hair cells ranging from the oval window, which on this slide is illustrated in the right lower quadrant, ranging up to where the little arrow is on the left-hand side of the slide, about just over halfway up the slide, you'll notice the absence of the cilia or hair cells. Unfortunately, once these cilia are damaged to the point where they disappear, then the perception ability for that mapped noise-level frequency is gone. It shouldn't be a surprise that the hair cells that map for the frequency of 4,000 hertz and higher are located nearest to the oval window. And so now you should understand why we often notice that 4,000 hertz notch on audiograms as the earliest sign of occupational or environmental exposure to loud noise. We're now going to transition into our discussion of ionizing and non-ionizing radiation hazards. Now this is a busy slide and I don't want it to be daunting. Let's walk through some of the information on this slide, which I hope as we go through the rest of this section of our presentation will help you to better understand the spectrum of radiation. Over on the left-hand side of the slide, we have the part of the radiation spectrum, the electromagnetic spectrum that includes non-ionizing radiation. Non-ionizing radiation, as you may remember from physics, has a longer wavelength and an extremely low frequency. So frequency is inversely proportional to wavelength. I like to look for simple ways to remember these concepts. So when I think about non-ionizing radiation and longer wavelengths, I think about overhead power lines and how they have those long dips in the wires. As we move over to the right-hand side of the slide, we have radiation of increasing energy and shorter wavelength. So we can see we're moving through the infrared spectrum, the visible light and ultraviolet spectrum through X-rays and gamma rays. And in upcoming slides, we'll talk about the different ways that non-ionizing and ionizing radiation can be hazardous with environmental or occupational exposures. Along the lower part of the slide are some examples of the different types of things that would generate these different types of radiation. So again, overhead power lines, radios, microwaves, radiant heat sources like an iron or a stove, arc welding, medical imaging studies and then radioactive sources, which could be used in medical imaging or in power generation or certainly as weapons. Let's start our discussion by talking about ionizing radiation. In the last bullet on this slide, I've stated that ionizing radiation or IR energy breaks chemical bonds. And that's important to understand that this is the way in which ionizing radiation can harm our tissues. This is a change brought on by physical effects on the DNA and hence the subsequent effects on our tissues. The different types of ionizing radiation include alpha particles, beta particles and gamma particles and their different characteristics are described on this slide. When thinking about appropriate personal protection for employees, we need to think about the different types of ionizing radiation particles. So for alpha particles, which are the lowest energy, these particles are stopped by intact skin. However, they can be a hazard when inhaled. Simply, we don't have skin inside our lungs. So for cases in which there is an inhalation exposure and radon, which we'll discuss in a future slide is a good example of this, or if someone has alpha radiation exposure due to shrapnel, skin will not protect that individual from the health effects of that exposure. The next type of particles are beta particles. These have higher energy than alpha particles and can penetrate to the germinal layer of the skin. So clothing would be protective from beta particles. The highest level of energy is in gamma rays and x-rays. And as we know for this type of radiation, lead shielding is required to protect us from the health effects associated with this type of radiation exposure. Our understanding of the cancer risk related to occupational or environmental radiation exposure, and we're talking about ionizing radiation exposure here, is described by the linear no threshold model. Looking at the graph on the slide, we can see that the observed health effects tend to increase as the radiation dose increases. The dotted part of the slide is an extrapolation for low doses of exposure based upon data from disasters such as the Hiroshima disaster. Please remember that the word stochastic means that there is no threshold. This is the same type of model that we use for chemical carcinogens, where there is no safe level of exposure. There are several ways that we can measure potential exposure to ionizing radiation. For individual employees, we can use film badges, TLDs or thermoluminescence detectors, or pocket dosimeters to measure their individual exposure. And monitoring of such exposures is required by the Nuclear Regulatory Commission. For the purposes of board review and your practice, it's important to remember that OSHA does not regulate occupational exposure to radiation. That exposure is regulated by the Nuclear Regulatory Commission, or NRC. For measuring radiation that might be emitted by an object, we can use ionization chambers if we can put the object in the chamber, or for larger objects or for scanning an area, we can use a Geiger-Muller counter, often referred to as a Geiger counter. Several types of units can be used to express radiation exposure, and this can be confusing. So hopefully this slide will simplify things for you. A dose of radiation absorbed in tissue can be described as a gray or a rad, with one gray being equivalent to 100 rads. The dose equivalent allows comparison of different types of radiation. So these units are sieverts or rems, and one sievert is equivalent to 100 rems. When we want to compare the dose of radiation over the whole body, then we can use the gray, and one gray is equivalent to either 100 rems or one sievert. On exams, you might see grays or sieverts, or other units, and so hopefully this slide has cleared up the mud for you with respect to the different types of units. In general, the more radiation exposure, the higher the dose of radiation exposure, the more severe the potential health effects. Radon gas is a byproduct of the radioactive decay of uranium, and radon itself decays by alpha particle emission. So this is one of the substances that, again, would be stopped by intact skin, but if inhaled or in a injury situation where you had shrapnel, could be hazardous. Exposure to radon gas is actually the second leading cause of lung cancer in the United States. And as uranium is ubiquitous in many states' soil, and if you want to have a good reference about which states this is, you can think about the states where fracking is common because those same shale repositories would be high in uranium. So states like Pennsylvania, New York, New Jersey, some areas out west. So the EPA has a recommended guideline for exposure of four picocuries per liter of air. And for example, if you were to sell a home in a state that had high repositories of uranium, and hence radon, you would need to have a monitoring done of the lower level or basement of your house to make sure that exposures did not exceed the EPA threshold. As we know from industrial hygiene, dilution is the solution to pollution. So one way to reduce the concentration of radon and reduce exposure, for example, in a basement, is to ventilate it. Another way to reduce potential exposure would be to seal off the potential for radon gas to enter a lower level of a house or a basement by sealing the foundation. Radon has been covered by the Toxic Substances Control Act or TSCA since 1988. And that is kind of a fun fact because most of the substances that are covered by TSCA, as you likely recall from environmental health, are actually chemicals rather than a radiation agent. As our understanding of the health effects and risk of radiation exposure has no safe exposure level, the goal for controlling occupational exposure is abbreviated as ALARA, standing for as low as reasonably achievable. And this is even a regulatory requirement for radiation safety. As I mentioned before, occupational exposure to radiation is controlled by the Nuclear Regulatory Commission or NRC rather than the Occupational Safety and Health Administration or OSHA. The NRC has established the following occupational exposure limits for all workers and then lower limits, as you would expect, for pregnant workers. And those are listed on this slide. As information, for those of you who are studying for the first-time boards, which would include environmental health, you will also need to be aware of recommendations for exposure limits for the general public, which would actually be lower than those established for workers. This slide summarizes some of the actions that can be taken as well as the theory behind them to limit occupational radiation exposure. Certainly, the less time spent near radiation, the less potential exposure. One exception to this principle is if the exposure is internal, for example, by inhalation in the case of radon or via shrapnel in the case of many radioactive substances, the internal exposure would then be determined by the half-life of the particular substance. The inverse square law, as exhibited here, relates exposure to the inverse square of the distance from the radioactive source. And this is an understanding that is best applied when the radiation source is emitting in a spherical method in all directions from the source. But it certainly makes sense that the farther away one is from the source, the lower the potential radiation exposure. A regular hierarchy of controls certainly applies to radiation exposure. And so the two methods above would really, with the exception of internal exposure, be considered administrative controls, specifically advising workers or requiring workers to spend less time near radiation and to be more distant from sources of radiation. As we discussed when we talked about the different types of ionizing radiation, different shielding can be protective corresponding to the type. And for review, I've listed them again on this slide. Let's transition to the next part of our discussion with a review question. We'll discuss the basis for the correct answer on the next few slides. There's been an accidental release of radiation at a nuclear power plant. You're called to advise regarding triage of a 50-year-old manager who presents with new onset seizures. What's the most likely prognosis for this worker? The correct answer to this question is choice C, death within a few hours to days. The information given includes the fact that this manager is suffering seizures. This is a sign of a very high exposure to radiation and this individual will likely succumb within a few hours to days. On this slide, I've summarized the three acute radiation syndromes in order of least serious to most serious. The hematopoietic syndrome corresponds with receiving a radiation dose between 0.7 and 10 gray. But certainly as with all things occupational and generally all things in medicine, our patients have not read the book, so to speak. So please be guided by the clinical situation and not necessarily by a given radiation dose. The primary cause of death in hematopoietic syndrome is the destruction of bone marrow resulting in a pancytopenia and resultant risk of infection and hemorrhage. Survival for these folks depends on the availability of appropriate medical treatment for anemia, infection and resulting hemorrhage. The gastrointestinal syndrome can appear in people who receive a dose greater than approximately 10 gray. These people experience the hematopoietic syndrome but in addition, experience great challenges due to fluid and electrolyte loss through the gastrointestinal system. Without treatment and even sometimes with the best treatment they can succumb within two weeks. The most severe acute radiation syndrome is the cardiovascular and central nervous system syndrome and occurs in people who've received greater than 50 gray of radiation exposure. These people experience both the risks of the hematopoietic as well as the gastrointestinal syndrome but in addition, due to the very high radiation dose, they experience central nervous system swelling, encephalitis and cardiovascular collapse and death usually occurs within three days due to these symptoms. In contrast with ionizing radiation that produces damage by breaking chemical bonds, non-ionizing radiation causes atoms to vibrate resulting in release of heat. Examples of non-ionizing radiation include radio waves, overhead power lines and microwaves. The health effects of non-ionizing radiation exposure are focused on the skin, vision and reproductive systems. It's important to remember that both ultraviolet A or UVA and ultraviolet B or UVB radiation increase the risk of developing skin cancer whether due to environmental or occupational exposures. UVA radiation exposure to the eye can result in the development of clouding of the lens or photochemical cataracts and again, this can be either due to environmental or occupational exposure. Photokeratitis or welder's flash is a temporary eye condition that generally resolves itself in a couple of days and is often experienced by novice welders. Exposure to lasers depends on the type of laser light. Lasers with visible spectrum light can cause photochemical and thermal injuries to the retina of the eye. Exposure to infrared lasers can cause corneal and retinal burns as well as clouding of the lens or cataracts and exposure to the skin can also cause skin burns. Male exposure to industrial strength microwave radiation has also been associated with impaired spermatogenesis due to the heating of the radiation as well as with cataracts in both males and females exposed. It's important to recognize that this is not microwave radiation emanating from a household microwave but industrial level radiation for example, that associated with large antennas. Studies of the health effects of extremely low frequency radiation such as that related to exposure to overhead power lines with as you remember, very long wavelengths have yielded only a modest or no association with childhood leukemias or brain cancers. However, other non-cancer outcomes have not been studied well. Based on this information, the International Agency for Research on Cancer or IARC has classified exposure to extremely low frequency radiation as a class IIb which is a probable carcinogen or in class III where there's insufficient information to determine whether this is a carcinogen. The term laser is an abbreviation for the technology light amplification by stimulated emission of radiation. We've already talked about some of the non-ionizing radiation or beam hazards of exposure to lasers. It's important to also recognize that due to the intense energy produced by these devices, there are also non-beam hazards including electrical and fire hazards. Lasers are used in a variety of industries and can be used to control interlocks, to guide robotics, to line up welds, as well as for their mechanical cutting ability in soldering, brazing, cleaning, and cutting. And we use some of these features in medical applications as well. To protect workers from occupational exposure to laser energy, we use our regular hierarchy of controls. Examples of engineering controls include interlocked rooms, protective housing, viewing portals, and status lights to protect people from entering areas where lasers are energized. Administrative controls certainly include appropriate education and training, as well as policies and practices to teach workers and enforce that workers are not entering areas when lasers are energized. Personal protective equipment to protect the eyes from laser exposure includes appropriate eyewear. And because there are many different types of lasers, it's very important to consult with an industrial hygienist or safety professional to ensure that you've selected appropriate eyewear corresponding to the type of laser in use. When thinking about the potential for occupational heat stress, we need to not only consider the environmental conditions, including temperature and humidity, but also the heat generated by the worker, particularly the job demands of the task, as well as any personal protective equipment or other clothing that the worker will be wearing to perform their essential job functions. So an example would be the case of a firefighter who is not only working in an extremely hot environment to say the least, but in order to work in that environment has to wear layers of very occlusive clothing, which would lead to increased likelihood of heat stress. Some important questions that we can think about when we're assessing the risk of occupational heat stress include the amount of heat that the worker would be generating, how well the heat could be dissipated, and the factors of their external environment in which the worker is working, such as the environment of a firefighter or the environment of an agricultural worker working outdoors in the heat. To assess the risk for heat stress, we use an index called the wet bulb globe temperature. This takes into account multiple risk factors in the environment, including air temperature, humidity, airflow, and radiant heat, and is measured by a wet bulb globe thermometer or heat stress monitor. On the next two slides, I've summarized some key features of the heat-related illnesses. On this slide, we have two of the less severe heat-related illnesses, heat syncope, which consists of basically dizziness, syncope or swooning, and vasodilation. Quick recovery is the norm from heat syncope. Workers who experience heat cramps are often hyponatremic due to drinking fluids that don't have enough electrolytes in them, as well as a lack of acclimatization to work in heat. Heat cramps generally occur later in the day or after a work shift, and the body temperature of workers suffering from heat cramps is normal, and in addition to the local cramps, they generally do not experience overall constitutional symptoms, which might be signs of a more serious heat-related illness. The treatment for heat cramps is replacement of both fluid and electrolytes, as well as rest. Although this slide displays separate columns for heat exhaustion and heat stroke, it's important to always realize that our patients do not read medical textbooks, and that although we have distinguished between clammy and pale patients suffering from heat exhaustion and hot and dry patients suffering from heat stroke, that we should use our clinical acumen when evaluating an individual patient. In general, workers who suffer from heat exhaustion have both salt and water depletion. This can be either from inadequate intake of electrolytes or inadequate rehydration in general, and as opposed to folks who are merely suffering from heat cramps, those suffering from heat exhaustion do have systemic symptoms, which could include mental status changes, nausea, vomiting, and overall weakness. People suffering from heat exhaustion need medical care as well as removal from heat. Patients with heat stroke have failure of the mechanism in their body to manage heat and can no longer dissipate heat. They often have body temperatures over 40 degrees Celsius, mental status changes, and systemic symptoms, which might include loss of consciousness and psychosis. Consequences of heat stroke can include circulatory collapse, multi-organ system failure, rhabdomyolysis, acute renal failure, and elevated cardiac enzymes. And again, although in general, patients with heat stroke have stopped sweating and are hot and dry as opposed to patients with heat exhaustion, this is not absolute, and you should go by the clinical features of your patient's appearance when evaluating these patients. Patients suffering from heat stroke need immediate emergency and likely inpatient and perhaps ICU care. Although we certainly would rely on our usual hierarchy of controls to reduce occupational risk of heat-related illness, due to the fact that heat is generated externally in the environment, the majority of controls used are administrative, and these include employee training, rules and policies around frequent rehydration, worker self-limiting of exposure and self-assessment, as well as administrative tools such as rotating time outside or time indoors in a hot environment. This could include examples such as two-in-two-out used by firefighters to reduce their risk of many exposures, including heat. Certainly maintenance of a healthy lifestyle, including reduction of additional risk factors for heat-related illness, such as use of alcohol and maintenance of a healthy activity level, would reduce the risk of heat-related illness, but often those are beyond the control of the employer. There is no OSHA standard related to medical surveillance or pre-placement screening specifically to reduce the risk of heat-related illness. However, when evaluating employees with a high occupational risk of heat stress, you can certainly design pre-placement screenings to identify workers who might be at higher risk to target education towards them. Let's pause here for another review question. A 55-year-old obese electrical lineman with a history of non-insulin-dependent diabetes and hypertension is called to restore downed power lines after an ice storm. Which of the following is he at increased risk for? A, frostbite, B, Raynaud's syndrome, C, hypothermia, or D, all of the above? The correct answer to this question, as you've likely surmised, is D, all of the above. Due to his underlying health conditions, this gentleman is at increased risk of cold-related peripheral illness, including frostbite, Raynaud's syndrome, as well as systemic hypothermia due to the fact that he is working outside. If this particular person is not a usual lineman working outside and perhaps has been called in due to a storm from his usual office job, then he would be at even increased risk of hypothermia due to a lack of acclimatization. While we use the wet bulb globe temperature as an index of heat stress, for cold stress, we use the wind chill index, which incorporates the temperature and the wind speed. We define hypothermia as a core temperature less than 95 degrees Fahrenheit or 35 degrees Celsius. Higher hypothermia is defined as a core temperature less than 86 degrees Fahrenheit or 30 degrees Celsius. And at this level of hypothermia, respirations and even a peripheral pulse may not be observed. Treatment for hypothermia includes aggressive re-warming, which might include measures such as warm peritoneal lavage or even extracorporeal membrane oxygenation or ECMO via cardiac bypass. For those of us who remember our advanced life support, you're not dead until you are warm and dead. And there are many stories, thankfully, of people who have experienced even very severe hypothermia and do survive upon re-warming and resuscitation. Workers exposed to cold stress are also at risk of peripheral disorders. These can include non-freezing tissue injuries, such as chill blaine, trench foot, which is due to prolonged exposure to wet conditions, such as having wet socks inside boots during prolonged exposure outside. Trench foot can also have long-lasting painful sequelae, including chronic foot pain. Frost snip is a partial freezing of the peripheral tissues due to cold exposure, whereas frost bite is a full thickness freezing of tissue, often occurring on the nose, tips of the ears, fingertips, and distal phalanges on the feet due to prolonged exposure to cold. Consequences of frost bite can include gangrene and infection, and treatment may require amputation to remove affected tissues. As with heat-related illnesses, the main way to prevent cold-related illnesses in workers is through education and training, both on preventive measures as well as early signs of cold-related illnesses. It's important to emphasize hygiene practices, such as drinking warm, sweet, non-caffeinated drinks, for example, hot cocoa, and to replace wet clothing with dry clothing when needed. Although alcoholic beverages may make people feel warm due to the peripheral vasodilation, not only are they not safe for people performing safety-sensitive duties and inappropriate for use at work, but they would actually put people at greater risk of cold-related illness due to the vasodilation and shunting of blood to the periphery. Specific prevention and control measures according to our hierarchy of controls would include engineering controls, such as insulated cabs in outdoor vehicles, insulation of buildings, administrative controls in addition to education and training, such as rotation of shifts and work hours to limit exposure to extreme cold, and use of personal protective equipment, including hats, gloves, and other measures to keep workers warm and dry. Transitioning to our next discussion of hypo- and hyperbaric conditions, let's review this case. Which of the following conditions would preclude qualification as a professional salvage diver? Would it be the need for corrective vision lenses, a history of remote knee replacement, recent sinus surgery, or skin conditions such as psoriasis? The correct answer to this question is C, recent sinus surgery, because this could put a diver at risk of inability to acclimate to depth. We'll begin this next part of our discussion talking about depth or hyperbaric environments, and then move on to altitude or hypobaric environments. Remember that for every 33-foot increase in depth, atmospheric pressure increases by one atmosphere. At standard temperature and pressure, or sea level, we're exposed to one atmosphere of pressure. So at 33 feet of depth, a diver would be exposed to two atmospheres of pressure. At depth, nitrogen partial pressure increases, and nitrogen dissolves into the blood to a point where it reaches equilibrium. If a diver ascends too rapidly from depth, the nitrogen does not have time to re-equilibrate, and then can dissolve out of the blood into bubbles, which can cause decompression sickness, affecting the joints, tissues, and at worst, the central nervous system. When nitrogen cannot equilibrate due to rapid ascent from depth, decompression sickness can occur. Three types of decompression sickness are illustrated on this slide. The least severe, or the bends, affect large joints, such as the hips and the shoulders, and are often viewed as a nuisance by professional salvage or caisson divers. The chokes, or pulmonary complications, are fortunately rare, however, can be life-threatening, not only because of the medical complications of the condition itself, but because as divers need to be self-responsible to return to their point of origin, a diver suffering from the chokes may not be able to seek buddy care or get him or herself back to the surface successfully. The most severe decompression illness is neurologic, and can affect the brain and spinal cord, and can certainly affect a diver's ability to both ascend and access definitive care. Let's pause for a review question. Here we have a scenario where a man is diving on one day, on Tuesday, to 120 feet, and then attempts to hike to the top of a volcano, and for your information, Haleakalos, just over 10,000 feet in height, the following morning. He becomes short of breath. What is the treatment? Well, let's review the choices. What we have here is the scenario of acute mountain sickness, or altitude-related illness, especially in someone who's violated what we would call the fly-dive or the dive-fly interval. So when we think about acute mountain sickness or altitude-related illness, what is the treatment? Certainly, choice A, oral steroids and oxygen, might be an appropriate response if we were asking for treatment after recognition of this syndrome. But that isn't the only thing that needs to happen. Diamox or acetazolamide is used to prevent altitude-related illness. Propranolol is really just a medication I threw in there as a distractor. And the correct choice here is choice B, descent. In order to resolve this gentleman's syndrome or symptoms, he needs to descend back to sea level to remove the altitude-related stress. In a serious circumstance, treatment might include oral steroids and oxygen, as I mentioned, but the definitive treatment is descent. And so choice B is the correct answer to this question. Occupations exposed to the stress of hypobaric or low-pressure environments include workers who work at altitude or in space, including climbers, high-altitude miners, and flight crew. Whereas we noted that there is one atmosphere of increased pressure at 33 feet of depth in our prior discussion, at 18,000 feet above sea level, abbreviated as ASL, atmospheric pressure halves to half an atmosphere. At 30,000 feet above sea level, atmospheric pressure is just over a quarter of an atmosphere. This slide summarizes a general framework for thinking about the health effects at altitude. As altitude increases, total pressure is reduced, oxygen partial pressure is reduced, and temperature is reduced. These changes result in an increased risk of decompression syndrome, or DCS, effects of low pressure on gas-containing body cavities, hypoxia due to low oxygen partial pressure, and exposure to cold due to a reduction in temperature at altitude. To better understand the physiology of changes that occur at altitude, we'll remember Boyle's Law from college and high school chemistry. Boyle's Law states that the volume of gas is inversely proportional to its pressure. Therefore, as we ascend and pressure decreases, trapped gas in the body can expand. Several places in the body where this can happen include the inner ear, our sinuses, and the gastrointestinal system. In addition to discomfort related to expansion of trapped gases in the body, health effects of hypobaric or low-pressure exposure, as might occur at altitude, include altitude-related hypoxia, acute mountain sickness, high-altitude pulmonary edema, and high-altitude cerebral edema. Rapid exposure to low pressure or decompression can cause acute hypoxia and decompression illness, which is similar to that which can occur rising from depth. The inner ear is particularly sensitive to barotrauma from rapid changes in pressure, including rapid loss of pressure. Signs and symptoms experienced by workers and others climbing or working at altitude can be subjective and or objective. I'm not going to read each of these on the slide here for you. However, I'd like to point out that many of the subjective and certainly some of the objective findings could be safety impairing and can certainly otherwise impair a worker or climber's situational awareness, which at height could be particularly dangerous given the conditions that the worker is otherwise having to combat at altitude. These would include, but certainly wouldn't be limited to, nausea, dizziness, euphoria and confusion, visual changes, some of which we'll talk about on an upcoming slide, as well as poor judgment and muscle incoordination. So again, anticipatory guidance about safe climbing and safe ascent are very important to reduce the risk of altitude-induced illness. Although we've mainly been focusing on the pulmonary and central nervous system effects of altitude in general, it's important to recognize that one of the first senses to be affected by hypoxia is vision, particularly diminished night vision. This can be in effect as early as 5,000 feet above sea level and at 3,000 meters or around 9,000 feet. Daytime vision would still be intact, but there is some beginning impairment of nighttime vision. At 5,000 meters or 15,000 feet, there can be up to 40% loss of night vision. This is particularly important if we appreciate the scenario of those who are working overnight, for example, high-altitude miners, as well as those who might be climbing recreationally to reach a summit or occupationally to reach a summit by sunrise. Prevention of acute mountain sickness or altitude-related illness is through administrative controls. Specifically, climbers should not ascend more than 3,000 feet per day once they've reached an altitude of 10,000 feet. Medications such as Diamox or acetazolamide may be used to reduce the risk of acute mountain sickness, but are not a substitute for a slow ascent. Treatment of acute mountain sickness includes descent, and then other medications such as dexamethasone or administered supplemental oxygen may be used to reduce the symptoms of acute mountain sickness. But again, the most important part of treatment would be descent.

physical hazards

ergonomics

vibration

ionizing radiation

non-ionizing radiation

noise

high temperature

low temperature

high pressure

low pressure