In this module, I'm going to describe to you a physical hazard. What if I told you that there was an invisible and odorless hazard to which many millions of Americans are exposed and that this particular hazard is the second leading cause of lung cancer in America. What if I also went on to tell you that this is something that's easily measured and easily controlled. Well, hopefully that's got your attention. Let's go ahead and move forward and I'm going to tell you a little bit more about radon. So what is radon? Radon is actually a naturally occurring radioactive gas? As I said, it's colorless. It's odorless. It's tasteless. It's actually the heaviest gas that occurs in nature. Where does it come from? Well, actually it comes from radioactive decay of uranium that's below our feet in soil and rock and groundwater. And as you can see in the image here as the radon gas is emitted, it tends to travel upwards towards the air in the atmosphere. The problem is as it does that, it emits ionizing radiation and so radon and uranium will decay into different radioactive isotopes or daughters as they're known. The key issue with radon is that it's everywhere potentially. There's a lot of variation in how much of it is present in different parts of the United States or in the state of Michigan as you see here and that variation is due to differences in geology and soil composition. So we're looking at a map of the state of Michigan here and you'll see the map is actually color coded. So the dark green counties on this map are counties in which at least one quarter or 25% of homes are equal to or expected to exceed the recommended guideline of 4 picocuries per liter. So that's a measure of a radiation concentration per a liter of air in this case. So dark green are the most heavily or highly exposed counties, like green are less exposed. And then the yellowish color is the lowest concentration counties. So 1 to 9% of homes above this guideline. So if we zoom in here and look at Washtenaw County where we are here at the University of Michigan in Ann Arbor, or you can see that about 38% of homes are tested above this 4 picocuries per liter guideline. Now we can also zoom out and look at this at the national level and again due to variations in geology and soil composition. We have actually tremendous differences overall in the United States about one in fifteen homes are in the highest radon level category. So this map is also color coded but the codes have a slightly different meaning the darkest red color on the map here are counties where the average indoor radon level is above that guideline of 4 picocuries per liter. The lighter red is counties with an average indoor concentration of 2 to 4 picocuries per liter and the yellowish color is counties that are below to picocuries per liter on average. So again, you can see that there's a substantial amount of variation geographically here where Southeast Michigan is very much in the the highest exposure zone, much of the upper plains and Intermountain West and also some of the East Coast particularly the Northeast have again areas with the highest concentrations of radon. Why are we worried about radon? Well, it turns out that radon as it decays emits a type of radiation called an alpha particle. And alpha particles are very powerful, but they're also very easily stopped. They can be stopped for example by a single sheet of paper or by a dead layer of skin on the outside of your body. The problem becomes if you inhale these alpha particles as radon emits, and they get into your lungs and now they're in very close contact with extremely sensitive tissues your lung cells. So you end up getting now a radiation of your airways and this unfortunately can lead to cancer. So the EPA has declared radon to be a class a carcinogen. This is a substance that's known to cause cancer in humans. As I said earlier, radon is the second leading cause of lung cancer in the US. I probably don't have to ask you what the first is but let's just acknowledge it, it's tobacco smoking. The US EPA estimates that there's about a 157,000 lung cancer deaths that occurred in the US in 1995, of which about 21,000 or 13% were related to radon. One of the problems with radon is unfortunately after your exposed, there aren't any warning symptoms or signs that you've been exposed. So how bad is radon exposure? It turns out the radon causes far more deaths than other events that are more commonly viewed as risky. So as I said about 21,000 deaths from radon in 1995, that's far more than were killed by drunk driving or by falls in homes or by people drowning or by people dying in home fires. And there's one particular subset of the population that is extremely at risk from radon and that's smokers. So smokers turn out to be 9 times more likely to get lung cancer from radon than non-smokers and in fact radon accounts for about 1 in 4 lung cancer deaths among smokers. What exposure standards do we have to protect us from radon? It turns out there's no known safe level of radon as I've already mentioned, radon is quantified using this unit of picocuries per liter. So that's a representation of the concentration of radiation in a liter of air or water. Now the EPA has done surveys of homes around the United States and they've estimated that inside homes on average. The concentration is about 1.3 picocuries per liter, but of course, there's radon in outside air too, and the concentration there on average is about 0.4 picocuries per liter. So the US EPA has set an action level and I mentioned this number before of 4 picocuries per liter. Basically about ten times higher concentration inside homes. That's allowable compared to that average outside concentration. How do we measure rate on? Well, it turns out this is actually pretty easy to measure radon is a very heavy gas as I mentioned already. So what we're going to do is look at the lowest level of a home that you actually live in where that heavy gas is going to accumulate. And we can do two types of testing, their short-term testing which can last between two and 90 days. You can see an image here of a radon test kit that's good for a three to seven day test. This is basically just a charcoal tube that you open and put in the lowest level of your home that you live in. Leave it open for the test period duration and then you send it to a laboratory and they tell you how much radon was measured. So this is a great screening test to very quickly assess for exposure. We can also do a longer term test though that might last between three months and one full year. The idea here is that radiation actually can vary quite substantially by distance. In fact, your neighbor may have none and you may have a huge problem. But it also varies by season. It tends to be higher in the winter and lower in the summer. So with the long-term test of three months to a year we can get a more accurate idea of your long-term average level. Now, it turns out that January is National Radon Action month. So I would encourage you when January rolls around or before to do a test at your home and the great news is these test kits particularly. The short-term ones are probably available from your local government or public health department and they often cost only 10 to 15 dollars. So a very inexpensive test to assess your health risk. How do we actually get exposed to radon? How does it travel through the environment? Well, as I've mentioned already most of the exposure we're concerned about is either in homes or commercial buildings indoors in other words, and there's two primary issues. We're working with here one is the air pressure differential between gas in the ground and gas in the atmosphere. And the second is what's called a stack effect, which tends to make hotter are move upwards through a structure. You'll see in the image here, there's a couple of different pathways that are highlighted for how radon gets into and moves throughout our house. So we might have cavities or gaps in our walls. We might have cracks in the floor that the gas can travel through there are construction joints. For example, where walls meet or ceiling meets a wall. There might be cracks in the walls below ground level. For example in your basement. There can be gaps basically in the floors of your home that allow the radon to continue to spread. The gas can also move through cracks just in your wall and then you're going to have gaps potentially around the service pipes that enter and exit your home and also move within your home and the gas can follow those gaps as well. So the good news here in terms of how we can reduce radon exposure is there are many ways. In fact, if your home is built in a high radon zone according to the EPA, it has to include some radon features to start with. One is that the home is built on a gravel layer that's gas permeable. So that's underneath your foundation. It lets the rate on move very freely under your foundation and away from your home. And then on top of that gravel layer is a plastic sheet underneath the slab that your home sits on and that plastic. Is impermeable or impenetrable to radon on existing homes? We can do a couple things. So one is seal up cracks in basements and walls and another is to add what's called sub-slab suction. This basically means you drill a hole in your foundation and you hollow out some Earth underneath and then you have a fan connected to a pipe and the fan basically sucks radon from underneath your house and ejects it at the top of your house where it can safely degrade in the atmosphere. So I said, this is good news. And indeed it is these very simple controls which often only cost a few hundred dollars can actually reduce your radon exposures by up to ninety nine percent. It's also possible for you to have radon in your drinking water and here again, we have options. So there's sort of two approaches one is to treat the raid on contaminated water as it comes into your home sort of a single treatment approach that can be very effective. There are also so-called point-of-use approaches. This would be for example, putting a filter on your faucet, but that's a less effective and more expensive method. So again here we've got a hazard that many of us are exposed to. We know it can cause a very bad health outcome, but the good news is it's very easy to measure and it's very easy to correct if you find a problem. So this is an example of a hazard that has huge potential to harm people but that is very easily managed.