Hello, I'm Dr. Ken Spaeth, I'm Chief of Occupational and Environmental Medicine at Northwell Health, and I will be presenting board review section on environmental health. It's a broad topic with a lot of categories to cover, and I will try to highlight those aspects that will be most useful and relevant for your exam. Like any clinical evaluation, a good history is central, and that includes an environmental history. This information comes from the ATSDR, which is part of the CDC and their recommendations in how to do an evaluation on environmental history. I mentioned ATSDR. There are any number of agencies within the federal government whose role overlaps with environmental health, but a key distinction among them is that some have regulatory power and some are simply advisory. It would be important to be clear on which agencies have regulatory power and which do not. Examples are listed here. Of the federal agencies with a regulatory power, the environmental protection agencies among the most important in regards to environmental health. They have a wide range of responsibilities, but these include hazard assessments and risk assessments. One of the most important pieces of legislation passed by Congress is the Toxic Substances Control Act, or TSCA. This legislation provides the EPA an important framework in how it goes about protecting the public in regards to environmental health. The components are detailed here. Another important piece of legislation passed by Congress is the Superfund Amendments and Reauthorization Act, or SARA. This piece of legislation not only provides additional guidelines for the EPA, but it also does something else, which is it created the ATSDR, the Agency for Toxic Substances and Disease Registry, part of the CDC. That's important because the ATSDR's primary focus is the evaluation and assessment of communities where toxic exposures have occurred. Question, which of the following is regulated by the Toxic Substances Control Act? And the correct answer is C. A, B, and D are incorrect because they are either regulated by other pieces of legislation or not at all. We will now focus on a number of specific environmental hazards. We'll begin with lead, which is an example of a compound that is under the auspices of the TSCA legislation and is one of the most well-studied environmental health hazards in existence. For most, the issue is a result of one of several sources. Older buildings with lead paint, soil that's contaminated, water that's contaminated, paint itself, or contamination of dietary supplements. It's important to note that lead paint continues to be the most important source of lead exposure in children. Arguably, one of the most important public health lessons learned has been that there is no such thing as a safe level of lead. And over the decades, that understanding has evolved. The consequence of this evolution has meant public health harm at a very substantial level. You can see that as the ban on lead set in, sometime in the early 80s, lead levels dropped off markedly. In regards to screening for lead in children, the current standard is that any value above 3.5 micrograms per deciliter is considered elevated. However, bear in mind that while the CDC makes recommendations for screening, how that is handled is really a local issue, so it varies considerably state by state and even pediatrician by pediatrician. The numbers you see on this page are more for giving you a frame of reference for trends. I don't think it's necessary to memorize the particular values, but I do think it's important to understand the trend that you see from lower exposure levels to higher exposure levels, to higher exposure levels, how clinical manifestations tend to present. This slide characterizes what I refer to as the clinical pearls for evaluation of lead in adults. These are high yield pieces of information. I would also add that the image on the slide demonstrates classic finding of lead toxicity, which is basophilic stippling. The clinical pearls for pediatric evaluation of lead exposure covers a lot of information, and you can see the slide has a lot of detail. This is generally a high yield topic, so I would be sure to be familiar with it in preparing for the test. I've also put a link here to the Pediatric Environmental Health Services Unit, which is a ATSDR-funded regional expertise throughout the country, and they have very good information about pediatric lead exposure. I've included here classic symptoms, the workup recommendations, and treatment. One thing I will note in this in thinking about pediatric exposures versus adult exposures with lead, neurocognitive effects in the form of IQ loss are the classic and most important considerations in children. This is less of an issue in adults, but it's considered the most important in children. Let's now switch to mercury, which, like lead, is also a heavy metal and, like lead, is also infamous for being a neurotoxicant, although, as you can see, it can cause harm to other parts of the body. There are different forms of mercury, and there are slightly different toxicological considerations for the different forms. In the United States, the most important exposure source is through fish in the form of organic mercury. As a result of that, both FDA and the EPA have made recommendations about the types and amounts of fish that pregnant women should consume, and in doing so, they are trying to balance the benefits for the developing fetus of the omega-3 fatty acids found in fish, but weighing that against the potential harm from mercury toxicity. The clinical pearls for mercury exposure in a patient would include knowing the distinction between acute exposure and its manifestations versus chronic exposure and its manifestations. There are also differences in how to evaluate biomarkers for the different types of mercury forms. So, for organic mercury, the type found in fish, blood testing is appropriate. For inorganic forms, urine is appropriate. If there's uncertainty, do both. Chelation is a clinical judgment typically reserved for higher level exposures, such as 100 or above. There is flexibility and recommendations regarding chelation for those reaching levels of 75 or higher if they're clinically symptomatic. In one of the most harmful events in modern public health, the misconceptions about the presence of mercury in vaccines has had a significant impact on vaccination compliance. I've put some information here to review the history of it, but the most important thing to remember is that there is no scientific or epidemiological basis for concern that the presence of mercury in vaccines causes any harm. Let's talk now about arsenic, another heavy metal. And the most common sources of exposure are dietary because arsenic is naturally occurring and is found in the Earth's crust and soil and many areas of the world, including the United States. And it is readily taken up by many plants, including plants that are edible, such as rice. Drinking water contamination, particularly of private wells is a common occurrence and handling of treated wood or burning of treated wood can result in exposure. In regards to the clinical pearls for evaluating arsenic exposure, it's important to know the difference between acute exposure and chronic exposure in the ways that the clinical manifestations differ. Of note, chronic exposure puts the exposed individual at higher risk for a number of cancers as well as the development of neuropathy. A key piece that it's really important to understand is that testing for arsenic must be done through urine and it must be done through a fractionated urine test. And this is critical because it distinguishes organic versus inorganic forms of arsenic. Organic forms of arsenic are what are found in seafood. Organic forms of arsenic found in seafood are harmless. They are without harm or risk. Inorganic forms, the type found in dietary sources, other than seafood, such as rice, in treated wood, in issues of water contamination, this is the harmful form. A routine test does not distinguish organic versus inorganic arsenic in the urine. You must do fractionated to be able to distinguish you must do fractionated to be able to tell the difference. Alternatively, avoiding seafood for 72 to 96 hours prior to the test can render the complication irrelevant but that presumes that the patient will be compliant and that's not always a certainty. So it's preferable to rely on an order fractionated urine testing so as to be able to distinguish between the harmless organic forms and the harmful inorganic forms. For acute exposure, there are chelation options. It is less clear, however, if there's benefit for chelation in chronic settings where longstanding exposure has resulted in things like neuropathy because the damage does not seem to be reversible. As always in environmental exposures, the most important intervention is ending the exposure. That is another important broad point to remember. Removal or stoppage of exposure is the most important intervention in environmental health. One of the most well-known and infamous case studies in public health involved arsenic exposure in Bangladesh. In an effort to control outbreaks of cholera, public health activists went in and attempted to put in tube wells which are ways of accessing drinking water from deeper down in the ground, thereby circumventing the likely exposures to cholera. However, in doing that, arsenic in the earth's crust and soil was tapped into. As a consequence, many of the wells that were built resulted in arsenic contamination at very high levels. The consequence of this was high numbers of individuals in Bangladesh experiencing chronic arsenic toxicity. Question, which fish species has the highest level of mercury per serving? And the answer is, the answer is A, swordfish. And this has to do with something I mentioned earlier, which is that mercury bioaccumulates in the food chain, which is to say that when consumed by microbes and small species, the concentrations are lower. But as higher species consume the lower species, there is a bioaccumulation that occurs so that by the time one reaches the highest parts of the food chain, such as swordfish and other predatory fish, the levels can become significantly high. By the way, the cartoon on this page reflects something that you should be familiar with. All fish species are contaminated with mercury. The only issue is to what extent and this reflects back to what we just discussed, which is that as you go through the food chain, the higher you go, the higher the concentrations. And so in general, it's always preferable from a mercury exposure standpoint to choose fish species that are on the lower end of the food chain. Let's now switch topics to discuss pesticides. Pesticide regulation is the purview predominantly of the EPA. And there are very strict parameters for how things like testing and labeling of pesticides must be done. Pesticide residue in food falls under the purview of the Food and Drug Administration. An important thing to understand is that when it comes to labeling of pesticides, there are two primary categories. The first is for the active ingredients. And that is typically what we focus on when evaluating exposed individuals. As you can see, there are specific parameters for labeling of the active ingredient. The other important category beyond active ingredient is the inert ingredients. And from an environmental medicine standpoint, something very important to recognize is that inert does not mean safe. The distinction of active versus inert is a regulatory distinction. It is not a toxicological distinction. So there are potential health effects that can result from the inert ingredients as well. If you look at the list of examples of substances that are in pesticides but fall under the inert category, you can begin to appreciate how some of these may indeed carry their own toxicity. It's worth pointing out that the term pesticide is very broad and can mean a lot of different things from rodenticides to herbicides to fungicides to, of course, insecticides. But remember that regardless of the category of pesticide, these are intrinsically toxic to living things. There's relatively little in the way of species-specific pesticides. There are some, but for the most part, what's toxic to one species is often toxic to other species. Now, the exact mechanism of toxicity may be different, and the role of the inert ingredients may be different. But there is much in the way of overlap in terms of toxicity. And that's partly why the application and subsequent exposure to pesticides is such a major public health issue. Pesticide exposure results from any number of different scenarios, as you can see. The important point is that pesticide exposure still represents a substantial public health problem both environmentally, occupationally, and even in terms of consumer use. One class of pesticides, the cholinesterase inhibitor pesticides, such as carbamates and organophosphates, function by poisoning acetylcholinesterase. And in doing so, acetylcholine accumulates in the synaptic space. And as a result, there is ongoing stimulation of the nerve receptors. For cholinesterase inhibitor poisoning, the clinical pearls are as follows. It's primarily a clinical diagnosis. Blood testing is not particularly useful, which is why it's so important Blood testing is not particularly useful, which is why a clinical diagnosis is key based on exposure history, signs and symptoms, as listed here. Treatment, the mainstays of treatment are always atropine, benzodiazepines, and PAM. Another category of pesticides are the pyrethroids. These are relatively recent. They've been around for several decades and are derived from naturally occurring compounds. They are very common in consumer pesticide products and are, as a result, a common source of exposure toxicity in and as a result of consumer use. The clinical pearls for pyrethroid exposed individuals relate to the common clinical presentations, which include paresthesias, GI effects, respiratory effects, and neurological effects. Diagnosis is strictly clinical. There are no readily available tests for biomarkers, so it's a clinical judgment based on exposure history and symptoms. Treatment is supportive. As always, the most important intervention in environmental medicine is ending the exposure, so that includes decontamination efforts, but generally speaking, care is strictly supportive. Question, which one of the following does the EPA have oversight of regarding pesticides? The correct answer is B, collecting data to characterize potential health risks. Another topic is endocrine-disrupting chemicals. The number and types of chemicals that qualifies endocrine-disrupting is quite extensive. I've put some examples here, and exactly how they exert their harm is variable according to the particular compound. The pathophysiology varies according to the compound, but the broadest description is that exposure results in dysregulation of hormonal and or endocrine activities in the body. This may be at the receptor level. This may be disruption of or abnormal production of signaling chemicals, hormones, etc., but regardless of the specific details, the upshot is the same, which is that there's abnormalities found in endocrine function in the body. Interestingly, Paracelsus, hundreds of years ago, phrased that the dose makes the poison, and in toxicology, that is generally true, but there are exceptions, and endocrine-disrupting chemicals appear to be such an exception that their effect can happen at very low doses, sometimes to a greater degree than at even higher doses. Another topic, and one that has taken on timely relevance in recent years relating to air pollution, wildfires, etc., are the National Ambient Air Quality Standards as set forth by the Environmental Protection Agency under the legislation as mandated in the Clean Air Act. As you can see, these standards are intended to establish a basis for regulating outdoor air pollution. The regulation of outdoor air pollution focuses on what are called the criteria air pollutants, and I've listed those for you here. The arrows point to the most influential and arguably the most studied of the criteria air pollutants, PM2.5, or particulate matter 2.5, and ground-level ozone, as distinct from atmospheric ozone. The Air Quality Index was established to help the general population discern and understand air quality issues in their particular area. So, upon entering the website and inputting a zip code, the results indicate air quality standards or air quality assessments for that particular day in that particular area broken down by subpopulations. So, the color-coded metrics correspond to the degree of health risk posed, and as I mentioned earlier, the criteria pollutants are the primary inputs in calculating what the Air Quality Index is. The most heavily weighted are particulate matter 2.5 and ozone. The reason that PM2.5 is so important in the Air Quality Index is because decades of research have demonstrated that it causes a number of different health injuries, and I've listed some of these for you here. Of note, its contribution to cardiovascular disease, premature death, and cancers has been demonstrated to have increasing importance as we get more science on this. Its role in the general population seems to be more and more important. Remember that PM2.5 includes all particulate matter that is 2.5 microns or smaller. Another topic that is growing in importance and focus within public health, including environmental health, is climate change, sometimes referred to as the climate crisis. And simply put, the atmospheric temperatures are rising as a result of the trapping of heat because of increased presence of greenhouse gases, most notably carbon dioxide and methane, in the atmosphere, that has resulted largely from anthropogenic sources, human sources of combustion of fossil fuels. At this point, the data is overwhelming about the relationship between human sources of greenhouse gases and its effect on the climate. There really is no controversy, despite the clamoring of some loud outliers. The data is clear and the consensus in the scientific community is clear. I've put simple graphs here for you to look at, one reflecting carbon dioxide measurements, which through sampling of ice cores are able to be dated back hundreds of thousands of years. As you can see, the levels in the modern era, in the past hundred or so years, are markedly higher than any normal variation in Earth's history. You can see the global mean temperature since the 1800s has increased correspondingly. I would point out, too, that in the past hundred or so years, where accurate measures of Earth's average temperatures have been taken, 2023 has demonstrated among the hottest days and weeks ever recorded in human history. I mentioned greenhouse gases, the most important ones being carbon dioxide and methane. There are others, as I've listed for you here. The discussion of the subsequent health consequences resulting from the climate crisis is vast and complex, but I have summarized those for you here. There are many good sources for finding more information about the connection between the climate crisis and global public health effects. I put some resources for you here. If you're interested, I've summarized it in the bullet points that you can see. I would sum that up by simply saying food and water access is put at risk, and the advent and spread of mosquito-borne diseases are also a major concern. What we've already seen quite clearly demonstrated, and this trend will continue, are the extreme weather events in the forms of droughts, storms, floods, etc. All of these things will potentially cause population-level crises and instability in the years to come. Question. The criteria pollutants regulated by the Clean Air Act include which one of the following? And the answer is ozone. The other answer choices are subject to various governmental regulations, but not as part of the Clean Air Act, nor as part of regulation of outdoor pollution. Indoor air quality, as opposed to outdoor air quality, which is tightly regulated as we've already discussed, indoor air quality is not well-regulated. In fact, there's relatively little that determines what is allowable or safe when it comes to indoor air. The literature and the science on indoor air quality includes a wide range of potential exposures and potential health issues. I've summarized what the literature points to as being among the most common issues with indoor air quality, but obviously issues can go well beyond what's on this slide. But these are the most common. So I've included the categories of diseases or symptoms, followed by a column for what the underlying causes are, followed by discussion in the notes column of exposure considerations and treatment considerations. At the bottom, I've also noted that the formerly used term of sick building syndrome has fallen out of favor and has been replaced by building-related illness. It's building-related symptoms if and until an underlying cause is identified. So if populations within a building are reporting symptoms, but no cause has yet been identified, it starts out as building-related symptoms. When the cause is identified, it becomes a building-related illness. So respiratory issues and fevers, until they are identified, may be characterized as building-related symptoms, but once, for example, Legionnaires is identified, it becomes a building-related illness as a result of exposure to Legionnaires. Focusing on a specific issue in indoor air quality is the issue of radon. There's a couple of things to note about radon, which is an important topic and one which you should be familiar with. As I mentioned in the slide, it's the second leading cause of lung cancer in the United States. It's also important to realize that it's a radioactive substance, and as a result, it's measured in picocuries per liter, and EPA has standards for what is acceptable. It's worth noting that while EPA has this standard, there is still risk even at levels below the standards that EPA has set. Generally the risks of environmental tobacco smoke are well known, but it is worth reemphasizing and are certainly fair game for the exam. So I put some important statistics here for you and some pieces of information about environmental tobacco smoke that you ought to be familiar with going into the test. So given that lung cancer is one of the most common cancers seen around the world, including the United States, and given that the contribution to lung cancer results extremely heavily, if not exclusively from environmental exposures, it's worth taking a minute to review what environmental exposures are capable of causing lung cancer, and I've listed those for you here. It's also worth remembering that cigarette smoke, while we typically associate it with lung cancer, is attributable to the causes of any number of other cancers beyond the lung. And I've listed those for you here. Also it's important to be aware of these. These often get forgotten about in thoughts and discussions of tobacco smoke, but they are a large public health burden and a direct result of environmental exposures in the form of tobacco smoke. Included in some of the discussion thus far related to carcinogens is this idea that there is a public health mechanism for identifying causes of cancer in the environment, and indeed there are, and it's important to be familiar with them. The most important is the International Agency for Research on Cancer, or IARC. IARC is the premier agency around the world that looks at environmental causes of cancer. They have a grading system, which I put for you here, and they assemble a panel of experts from around the world in various disciplines, including epidemiology and toxicology, to focus on a particular compound or substance or exposure or occupation, and to review the animal, experimental, epidemiological, toxicological literature, and arrive at a determination for what the relationship is between exposure and cancer. They have reviewed several hundred substances over the years and issue new ones on a fairly regular basis and updates to existing ones on a fairly regular basis. Similarly, EPA has a process for identifying carcinogens that's very similar, as does the National Toxicology Program. Another important area of environmental health is drinking water. In the United States, the Safe Drinking Water Act, passed by Congress, mandates that EPA oversee the safety of drinking water, and I put some basics for you here on the slide about the drinking water infrastructure in the United States. Needless to say, it's quite large, quite extensive, and as discussed in regards to outdoor air pollution, there are a number of standards in place that look at contaminants in water and set regulatory mechanisms in place. In addition to the water authorities and water systems throughout the country, which are under the auspices of EPA oversight, there are roughly 15 million homes in the United States that use their own private wells and are therefore outside of the EPA's regulatory purview. As a consequence, it's left to the individual homeowners to test for and identify potential contaminants in the well water. In determining how best to make drinking water safe, there are a number of parameters that must be met. So of course, the process for making the water safe must not pose any subsequent risks to humans, pets, or animals, and it must ensure that the taste and color of the water are acceptable. It also, of course, from practical considerations, must meet a number of requirements. It has to be financially feasible. It has to be easy to implement and maintain and put in place. And of course, it must be effective. It has to be able to destroy bacteria, viruses, and any amoebas that might be in the water and do so, allowing for a lot of variation in water temperature, composition, and even the extent and range of contaminant. Around the world, drinking water purification tends to fall into one of three categories. Chlorination as the process, ozonation, or UV radiation. In the United States, chlorination is the process that is predominant, and as you can see in the slide, there are reasons for that. And when it comes to keeping our drinking water free from microbes, you can see the breakdown of what's likely to be found in water, and of note, chlorination is effective against all of these, but less so against cryptosporidium. That requires improved filtration in order to remove the cryptosporidium from the drinking water. I've given you some data here to show the public health impact of waterborne diseases on the U.S. population. These trends have been fairly consistent over the years and would be useful to have a general understanding of the scope of the impact, not necessarily the precise figures, but a general sense of the scope of waterborne diseases. Here I've listed for you the most common microbial contaminants found in drinking water, as well as the more common chemical contaminants found in drinking water. Question, a key advantage of chlorination as a means of water disinfection includes which one of the following? The correct answer is B, D, like dog. D, like dog. There might be some temptation to pick A, but if you look back and review the discussion regarding chlorination, not all forms of microbes are eliminated. Specifically, cryptosporidium is more of a challenge using chlorination. In regard to chemical exposure, the EPA does have action levels set for many different chemicals. I've listed the more common ones here. Of these, I don't think you need to memorize them, but I would be familiar certainly with lead and benzene, and generally just the trend overall. This slide and the next slide refer to the lead contamination that occurred in Flint, Michigan, and which has subsequently become a case study in lead exposure in drinking water and also in environmental justice. I think it's useful for the purposes of the test to know the basics about what happens in Flint, so I've provided these for you on the next couple of slides. The purposes of the exam, it's also useful to know some information about the use of fluoride in the drinking water as a public health intervention to prevent dental disease. I've put the levels and some other facts related to fluoridation of the water, and I think it's fair game for the test, so I would be familiar with them. Drinking water quality is one of the major public health issues globally, and so I've given you some data about the public health burden in relation to drinking water and clean water access around the world. Given the significant public health burden globally in regard to water contamination, including as a source of infectious disease and diarrheal diseases, as well as drinking water contaminants, I put here some of the public health interventions that are promoted around the world as means of addressing particularly diarrheal diseases and the subsequent impact and the subsequent impact on childhood mortality and morbidity as a consequence of diarrheal diseases. Question. Which of the following is the recommended range for optimal concentration of fluoride in drinking water to prevent dental caries? The answer is C, 0.7 parts per million. As you can see in the characterizations provided by the CDC, the burden of foodborne outbreaks in the United States tend to link back to predominantly fruits as the source, and of course animal contact as another major source. Here I've provided a list of the microbes most responsible for illnesses, hospitalizations, and death, and you can see that the top five are for the most part repetitive in terms of their contribution. But be aware that norovirus is by far the biggest, has the biggest impact from a public health standpoint in terms of morbidity, far and away above any of the others. So in terms of illnesses, particularly in settings of restaurants or cruise ships, always think norovirus as the source of the outbreak. Here are some basic statistics about the relative contribution of microbes and some clinical pearls regarding clinical approaches to such agents. Question, the most common cause of foodborne outbreaks in the U.S. is which one of the following? The correct answer is norovirus. In the context of increased incidence of heat extreme events, it's particularly pertinent to have a discussion about heat-related illnesses, and we'll start by looking at populations at increased risk for morbidity and mortality related to extreme heat, as well as general strategies for prevention, and both of those are covered on this slide. So in regards to specific categories of heat-related illnesses, it's really a continuum on which symptoms increase or decrease in severity. And as a result, the treatments for these are specific to the severity of a particular sign or symptom. But the four basic types of heat-related illnesses on the continuum are identified here as heat stroke, heat exhaustion, heat injury, and heat syncope, each with their respective classic findings and some discussion of treatment. In contrast to heat-related illnesses, we'll have a discussion here of cold-related illnesses. Cold temperatures are also potentially harmful, causes of morbidity and mortality. And here too, there are subpopulations at increased risk. These are identified here as well as other risk factors and preventive strategies for cold-related health effects. On this slide, you'll find that the key cold-related clinical manifestations that are fair game for the test, hypothermia, frostbite, chillblains, and trench foot. I've given very brief descriptions of the clinical presentations in terms of classic findings, classic scenarios in which they're found, and clinical features, as well as treatment considerations for each. And it would be appropriate to familiarize yourselves with these in anticipation of the exam. On this slide, you see visuals of the dermatological findings associated with cold-related illnesses from chillblains, trench foot, and frostbite. And you can see that the difference can be understood in terms of the depth of tissue damage in the skin. Visuals are fair game for the test, so it would be useful, I think, to recognize the basics of how these images connect to the various temperature-related injuries. So another environmental hazard is noise. And I've tried to give you a sense of the range of decibels associated with various activities, and also how the range can affect hearing. Remember that the decibel scale is logarithmic, so this is a nonlinear increase. These increases are exponential, rather than linear, in going from one level of decibel to another. It's logarithmic, and therefore, can't be thought of in the same way a linear scale is thought of. This slide characterizes the health effects associated with loud noise. Some of this is intuitively obvious, including hearing loss. But please note on the right side of the slide are other health effects that have been identified through epidemiological studies in a consistent pattern, such that these health outcomes are also associated with environmental noise. In the topic of baromedicine, be aware that we will cover both barometric effects on health from increasing altitude and below sea level. And on this slide, you can see how a change of altitude and depth of sea level alters both the partial pressure of oxygen and nitrogen. And as a result, the health effects are quite different, but they too are on the spectrum of atmospheric pressure, from very low atmospheric pressure up at 40,000 feet above sea level to five atmospheres of pressure at 132 feet below sea level. And as elevation increases, there's a risk of hypoxia because of the low barometric pressure and subsequent decreased partial pressure. Hyperbaric environments can result in barotrauma under the circumstances in which one is below sea level. The depth of being submerged in the water can cause a spectrum, a continuum of injury. And I've described some of the key issues here and some of the key findings as well as key treatment considerations. You should be familiar with these for the purposes of the exam. In contrast to being immersed in the ocean at various depths is elevation above sea level at various heights. So again, it's a continuum of signs and symptoms. I have summarized these here for you simply with the usual characterizations and classifications, their clinical presentations, and essentially the primary treatment considerations for each of these. And you'll notice that most important of these is descent from that height to a lower elevation. That's the most ready-made answer for the most effective and most important treatment association. In consideration of travel medicine issues such as contraindications and relative contraindications for taking airplane flights, I've listed those for you here with a link at the bottom of the slide if there's interest in getting more detail on these. Again, I would have a general familiarity with these for the purposes of the exam. So on the topic of travel medicine, I've collected for you the summary of travel immunizations that you should consider fair game for the exam. I would point out that COVID has been a bit of a game changer in terms of these requirements. I suspect you will not get questions on travel requirements regarding COVID. That's an ever-moving target. Countries have regularly changed their policies over time, so it's not likely to be a reasonable question to be on the test, other than a very general comment that one should check the requirements for vaccines or proof of prior infection for entering to a country before making plans to travel there. That's good advice for any requirements for vaccines or infectious disease, but it's certainly the most reliable and fairest answer should anything come up regarding COVID, but I think that unlikely. What's on the slide should be covered or what's limited in terms of travel immunization questions because this is all fairly consistent and has been stable requirements for many years. Chronobiology is a topic that is fair game for the test as well, so I put some basics of it for you here and what the consensus is for treatments. As you can see, it's a series of behavioral and supplement-related interventions all of which are soft guidelines, but these are indeed used clinically, so they are worth being aware of and having some familiarity with. Question, a patient is attempting to ascend Cotopaxi on a trip to Ecuador. She calls from 14,000 feet via satellite phone reporting shortness of breath and headache. The most effective intervention is? The correct answer to this question would be to descend immediately. Switching topics to environmentally-related causes of public health disasters. Remember, there are several different categories. There are, of course, natural disasters in the world of public health and unnatural, and I've given some examples of those. And we talk about the effects of that running the gamut from acute to chronic, sometimes referred to as hot or cold, and there's other nomenclature, but the idea being that in the immediate aftermath, the consequences, both health-related and otherwise, are specific to the nature of the disaster, but over time, that evolves into a more chronic long-term consequence, both health-wise and in other ways. Thinking about disaster response, whether it's natural or unnatural, there is a public health infrastructure for managing and responding to such events, and I've laid out some of the agencies here. Obviously, the full extent of any agencies would depend on the specifics of that disaster, but these agencies would be and are regularly involved as part of the response. While the nuances of a specific response in the case of disasters, one of the staples is a principle, organizational principle, referred to as the incident command system, and I've given you a brief description of it here, and it's something you should be familiar with. As was alluded to already, the evolution of response following a disaster is something that needs to be understood in its most basic forms. So, to properly respond requires a needs assessment from a public health perspective to understand the implications and risks posed to all the populations who are at risk. That might include first responders, it might include local residents, but regardless, assessing the degree of risk is one of the, and the nature of the risk, is a critical first step. One of the lessons that's been learned as a result of disasters like the World Trade Center attacks on 9-11 the health implications of being exposed or put at risk during an event can extend well beyond the event itself. And so, ongoing monitoring and evaluation is critical. And so, the needs assessment that we spoke of is really the first step and the needs assessment that we spoke of is really an ongoing process for which there is adaptation and modification depending on the details of that particular disaster and how it unfolds over time. Question, which one of the following vaccines may be required for someone entering certain countries? The correct answer is C, yellow fever vaccine. The others, while they may be recommended, are currently not requirements for entry into any countries around the world. Question, the first step in a public health disaster response is, and the correct answer is C, completion of a needs assessment. And again, the idea is before interventions of any kind are offered, it's critical to understand what hazards and risks are posed to those present. One specific type of hazard and disaster would be biological, chemical, or radiological weapons that were used as part of a organized attack. Biological weapons are categorized as class A, class B, and class C. The classifications reflect the likelihood of use and or the degree of risk. For the purposes of the exam, you should focus only on class A, but have a general understanding of classes B and C. Biological agents, class A, are the likeliest agents to be used in the event of a biological attack. They have a variety of properties that make them high priority. For example, they may be easily transmitted through spread of aerosolized droplets, they may have high mortality rates or high morbidity rates. I've listed for you the six class A biological weapons that are currently recognized. You should be familiar with those, class or category B and C. Class B and C, I don't believe anyone would ever ask you about on an exam, but you should understand that generally speaking, these also could be used as weapons. However, they're less impactful either because of their lesser capacity to cause death or to spread readily. Category C is reserved for emerging threats. Newer viruses that come out that have the potential to be weaponized, but are not known to have been used or developed as weapons. This is a list of the primary class A bioterrorism agents, and I've categorized them by the agent, associated symptoms that are classically linked to these agents, the route of transmission, and incubation period as noted. Then post-exposure prophylaxis, that is to say what to give folks who may have had exposure, but are not symptomatic. And then the treatment for those who have become symptomatic. A classic question regarding the use of category A biological weapons is regarding the distinction in clinical presentation between smallpox and chickenpox. And as you can see, the presentation is easily distinguishable in regards to where in the body the rash presents. In smallpox, it's a centrifugal distribution, hands, feet, face, whereas chickenpox is largely truncal in predominance. Question, which of the following classes of medication increases the risk of hypothermia? Increases the risk of hypothermia? Answer is C, neuroleptics. For chemical agents, I've summarized the classes of chemical agents, the primary example of a chemical agent from that class, the key clinical features that would be fair game for asking about, and the treatments. Again, these are the most representative and the highest yield. So it would be advisable to be familiar with these. Remember that decontamination is always the first step. It's really an analog to what's already been discussed that the most important intervention with environmental exposures is ending the exposure. Decontamination is one means of doing that. And you can see there's hot zones, warm zones, and cold zones, and I've indicated how those can be thought of in terms of disaster response and what makes each zone different. Radiological or nuclear weapons can be thought of in terms of the source of the radiation and the degree of their capacity to cause injury. So I've listed for you five possible scenarios or devices and the implications for how each would be utilized. In regards to radiation injuries, I've broken down the kinds of exposure into the three main categories, which are alpha particles, beta particles, and gamma or X-rays, and indicated some of the distinctive features that apply to each one. You should be familiar with those and understand that what makes ionizing radiation such a hazard is its high energy waves are able to result in the breakage of chemical bonds. And it's clearly a dose response for which there's no threshold, meaning that low exposure yields low risk, high exposure yields high risk of developing cancer and or other health effects. And the three pieces of consideration for exposure are time, distance, and shielding. The greater the time, the worse the exposure. The shorter the distance, the worse the exposure, and the less shielding used, the worse the exposure. And conversely, the less time spent, the greater the distance and the greater the shielding, the better. This slide, I've tried to give a perspective on the extent to which grays of exposure, which is the international system of units that replaced RADs, and to try to give some scale or frame of reference to understand how much exposure correlates to the various kinds of injuries. Again, I would say you don't need to memorize the exact numbers because these are approximations and the exact numbers used in different textbooks may vary a little bit, but the overall scale of this is accurate. And so it would be prudent to understand the general ranges where these injuries can occur. Again, thinking about acute radiation syndrome, there are different phases that occur over a period of time. And I've laid those out for you with time frames as appropriate and the associated clinical features. In general, radiological weapons, such as dirty bombs that are improvised devices, are a threat as much because of any conventional detonation that's used to release them, as well as the dispersal of radiation or radioactive materials. The thinking on this is that the radiation will not likely pose major public health risk, but certainly from a mental health standpoint, it has potential for significant concern. And this is of note largely because radiological weapons, such as dirty bombs, which again are just improvised conventional explosives where radioactive material is attached in some way and thereby dispersed when the explosion occurs, are the easiest and likeliest type of scenario to occur and therefore are worth having some familiarity with both clinically and from a public health standpoint and make them fair game for questions on the exam. Once again, decontamination is always the first step. Exactly how this is to be done will vary according to the details of the nature of the exposure, but it is always the right answer when asked about the first step. Understanding the exposure risk allows first responders and medical personnel to don the appropriate gear and handle themselves and any potentially contaminated material safely and appropriately. Management of acute radiation syndrome is largely supportive as described here. The only real preventive strategy are potassium iodine tablets in the event of a thermonuclear blast. That's the only appropriate use of potassium iodine tablets. They have to be consumed within 12 hours, and the only thing that offers prevention of is thyroid cancer. Now, thyroid cancer is high risk in the event of thermonuclear release, as we saw in Chernobyl and Hiroshima and Nagasaki. However, again, the other cancers that are at high risk will not be mitigated by taking potassium iodine tablets. Only thyroid cancer will be affected by that. And again, that's only appropriate if there's been some sort of thermonuclear reaction. It would not, for example, be useful with a dirty bomb. Non-ionizing radiation are forms of radiation on the electromagnetic frequency that are not powerful enough to cause breakage of bonds within molecular structures. However, that is not to say they can't cause some harm, but they are not likely to cause cancerous effects. I've listed here for you the associated health effects resulting from forms of non-ionizing radiation. Briefly, I think everyone is familiar with the attacks on the World Trade Center on 9-11-2001. I've summarized for you the nature of the dust and smoke, some of the key components there, and also the common health effects seen in first responders, rescue and recovery personnel, and also in the residents from that area, as well as those present in the first hours, days, and weeks. Question. Regarding chemical weapons, what is the most important intervention in managing victims of a chemical attack or exposure? The right answer is always going to be decontamination. No matter what type of chemical weapon, the correct answer is decontamination has got to be the first step. As yet another example of how broad the category is of environmental health, it's worth having some familiarity with the built environment. And the built environment has to do with urban or suburban and even rural development patterns and structures, the way land is used, and the way those living and working there interface with the land. So things like green space, mixed zoning to encourage walking versus requiring cars, as is often the case in suburbs, all of these have public health implications, which are recognized, I would say, in the past 15, 20 years as an important public health. As an example of the public health implications of the built environment, we know, for example, that data suggests that in areas where there are more green spaces for physical activity to be performed, in areas where there's mixed zoning of residential and commercial, there are better outcomes in terms of BMI, things like hypertension, cardiovascular events, et cetera, largely as a function of the built environment and the associated lifestyle. When assessing environmental health risks, standard methodology is to engage in what's called a risk assessment. This has been developed and put forth by a number of public health agencies, most notably the EPA and the Center for Disease Control via the ATSDR. And as you can see, there are four parts, and I would familiarize yourself with the four parts, and the subsequent slides define each part and give some explanation as to how to think about them. The first step in a risk assessment is hazard identification, which is explained here. Two important concepts that relate to a risk assessment, toxicokinetics and toxicodynamics. One mnemonic for remembering toxicokinetics is toxicokinetics are what the body does to the contaminant. Toxicodynamics, in contrast, are what the contaminant does to the body. Dose-response relationship is another key piece in the risk assessment process as explained here. One benchmark for helping to understand dose-response is the reference dose. This is used for helping to estimate the likelihood of developing non-cancer health effects. It's a commonly used benchmark by EPA when doing such risk assessments and likewise by CDC under such circumstances. An important concept to understand as part of the risk assessment process is the dose-response. I've mentioned it already, but it warrants some more discussion. So for example, an important concept to understand in regards to dose-response when evaluating exposure to a carcinogen is the dose-response is thought of as having no threshold value, meaning that even the tiniest amount of exposure carries with it some degree of risk, even if it's quite low. And that risk increases as the dose increases. In other words, as the exposure increases, the likelihood of developing the respective cancer increases. In contrast to carcinogens, exposure to non-carcinogenic substances is thought of as having a threshold. Below the threshold, the likelihood of health effects is thought of as extremely low. Above the threshold, the risk of developing health effects is considered significant. The final step in a risk assessment is combining the data and understanding gathered through the previous three steps, the hazard identification, the dose-response component, and the exposure assessment piece, and ultimately arriving at a characterization of the risk. Once a risk assessment is completed, the next steps are to determine essentially a response plan. How to deal with the apparent risk and what strategies can be used to mitigate, reduce the risk, protect the health of the public. One key piece, of course, is risk communication. How to communicate effectively to the lay public the extent of the risk, the findings from the risk characterization, the data and conclusions from the risk assessment, and be able to package it and present it in ways that will appropriately characterize the risk and convey appropriate preventive strategies to the public. I want to thank you all for enrolling in the course and for your time today. I hope it was informative and helpful. Thank you again and best of luck on the exam. Study hard.

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