In other modules, we've discussed the many health risks that are associated with our environment. But we haven't really talked about is how we can methodically and systematically compare those health risks in an objective way. In this module, we'll be exploring this concept of risk assessment which is designed to allow us to make those evaluations. First, what is risk? In public health, we define risk as the probability of adverse health effects from exposure to some hazard. Those adverse health effects could be things like injuries or disease, all the way up to death. Now, we have to understand that risk is a function of a couple of things. One is the potential of someone to be exposed. The second is the characteristics of that exposed individual or population. The third is the likelihood of occurrence of both the exposure and the associated health impacts. Now, it's important to understand that risk impacts many aspects of our life. So there are risks that are taken in commerce, in politics. We talk about risk with regards to population health but also individual risk factors. There's risk associated with social development and economic development, and stability. But our notions of risk are also influenced by many things. This can include political influences, influences from the media, just general perceptions of risk at a public level. We have to think about bureaucratic imperatives. So an agency that regulates a particular risk might have a much different take on that risk than another agency not responsible for those regulations. Our risk perceptions are also influenced by legal and economic factors, and by science, and finally by ethics. Risk assessment as I mentioned earlier is a scientific approach for evaluating the potential from harm for environmental hazards. The goal of a risk assessment is for us to be able to answer a number of questions, how harmful is this risk, how important a priority should it be, what hazards are out there that are of greatest concern to us, and what's the comparative risk between different hazards. The goal here is really for us to do risk assessment and provide pertinent risk-related, and evidence-based information to all the involved parties. That's going to include risk manager whose job professionally focuses on understanding and reducing risk. Policymakers who may pass laws that are designed to address risk. Regulatory agencies who pass regulations to specifically limit risk. Then, of course, the public in general. How do we actually measure risk well risk is quantitatively expressed in values that range from zero. Basically, harm will absolutely not occur all the way up to one. In other words, harm is absolutely going to occur. We typically express risk either as a whole number or as a fraction. I'll give you some examples here. So the risk of death after exposure to more than 5,000 rems, a unit of exposure of radiation, is one. Meaning, everybody who has that exposure or greater is going to die. Now, that's an extreme example, fairly unusual, but it is an example nevertheless. We could also describe risks. So for example, if we have one case of asthma among 10,000 children, the risk becomes one divided by 10,000 or 0.0001. If we put that in scientific notation as we often do in risk assessment, that would be a risk of 1 times 10_-4. We might talk about a risk of one case of cancer in a million people. So that's one divided by a million or 1 times 10_-6 in scientific notation. Our numbers are often not that whole and rounds, so we might describe one case of lung disease per 770 workers. So 1 divided by 770 is the same as 1.3 divided by 1,000 or 1.3 times 10_-3 in scientific notation. So we have this common unit that we can report risk and we can also express risk over different time periods. We might talk about risk over a day, or a week, or a month, or a year, decades, even all the way out to a lifetime. The great thing about risk assessment is it really is intended to let us compare apples to apples. We can move from qualitative or more subjective judgments of risk to quantitative and hopefully less biased assessments. We need to understand that some risks have a dread factor associated with them. These risks can be viewed as uncontrollable, were catastrophic or involuntary, and example here might be a nuclear reactor accident. However, many risks have more of an unknown factor to them, so the impacts are not observable or may be completely unknown to those exposed. This might be a new risk that's simply never existed before in human experience, or it might be a risk that it has a delayed impact. An example here might be the use of DNA technology, which has a lot of unknowns attached to it. I'm going to spend the next minute or two talking to you about the graphic shown here on the right. So this is now somewhat old graphic from 2003, but I think it's still quite compelling. Let's dig into it. So on the right-hand side of the image here, we're looking at risks that are more commonly associated with greater fear in the public, but actually have a lower associated or quantitative risks. So at the very far right of the image here, you can see shark attacks. Your risk of being injured by a shark is about one in six million times that you enter the ocean, and your risk of dying is about one in 578 million. So that's a very low risk, but it's something that many of us get quite concerned about when we're bathing in the ocean. We could also think about your risk, for example, of West Nile virus, or your risk of snake bite, or some of these other incidents that have this dread and fear factor, but are unlikely to happen to you. On the left-hand side of the graph here, we're looking at things that are actually more risky for us, an objective basis but that we fear less. So at the far left here, we're looking at skin cancer. Your odds of getting skin cancer are one in 200, and your odds of dying in skin cancer are one in 29,500 people. So that's incredibly more risky compared to a shark attack, but it's something that probably most of us don't fear as much. Likewise, things like food poisoning and bicycle injuries, and getting hurt by your lawn mower, these are things that are much more likely to impact you but they have less dread and less fear associated with them. So risk assessment, lets us move away from this sort of dread factor and start to objectively quantify what is the actual risk to you from these various incidents. Finally, I'd like to wrap up on a high note, in that there are four agencies that are responsible for regulating risk for individuals here in the United States. Let's see which they are. The first is the Environmental Protection Agency, which is responsible for regulating hazards and risks in our air, water, waste, and also regulates pesticides specifically used for food production. Second, we have the Food and Drug Administration, which regulates hazards from food and drugs. No surprise there. Third, we have OSHA, the Occupational Safety and Health Administration who regulate safety and health hazards that specifically occur in workplaces. Fourth, we have an agency you may not have heard of before, the Consumer Product Safety Commission or CPSC. Now, this agency is responsible for regulating hazards and risks from consumer products. Hopefully, this module has given you a better understanding of why risk assessment is so useful and so important, and set us up for other modules where we'll look at the actual steps that go into conducting a risk assessment.
