Introduction
Radon

Air pollution is all around us.  Almost every new technological advance that we have produces some form of air pollutant.  Internal combustion engines in cars emit carbon dioxide, nitrous oxides, and carbon monoxide, just to name a few. When we think about air pollution, we often only consider those sources that are outside of our homes.  However, air inside our homes is constantly being polluted, as well.  The plastics in computers, televisions, and stereos emit volatile organic compounds.  Cleaners that are used in the bathroom and kitchen emit substances like ammonia and chlorine gas.  In the past, we did not worry too much about these indoor pollutants.  However, we have begun to make our homes more air tight as we try to increase their energy efficiency.  This traps these pollutants inside our homes and raises the levels of toxicity in our homes to greater than that found outside our homes.

Some of the lethal stuff in our home is not produced artificially.  Radon gas is a radioactive substance that enters our homes naturally through the floor.  Unlike the pollutants that we trap in our house, radon poses no chemical threat, as it is a noble gas and does not react with other substance.  Radon's lethality lies in the fact that it is a gas that can be taken into our bodies where it can undergo radioactive decay, thus exposing us to ionizing radiation.

The ultimate source of rado is uranium-238, which is found naturally in rocks and soil within the Earth's crust.  Uranium-238 is a long-lived radioactive substance that has a half life of about 4.5 billion years.  After the uranium-238 does decay, it does not just disappear.  It decays into other radioactive substances (called daughter products) that also decay into other radioactive substances. The end result of this entire decay process is lead-206, which is the first stable isotope that in the decay chain.  However, before it reaches lead-206, it becomes radon-222.  The unique thing about radon-222 is that it is the only gaseous substance in the entire decay chain.  Thus, while it is decaying from uranium-238 down to radon-222, the isotope is always a solid, which means that it remains in the Earth.  When it finally reaches radon-222, it becomes a non-reactive gas, which floats up through the crust.  If a home happens to be at the surface where it exits the crust, then the radon-222 will enter the home.

Radon in Your Home

With the airtightness of new homes, the radon-222 is effectively trapped.  This isotope has a relatively short half-life of about 4 days.  When it decays, it decays via alpha particle emission.  An alpha particle is the same thing as a helium nucleus, which means that it is fairly large, and it is very positively charged.  The problems start when the radon-222 that is trapped in the house is breathed in by one of the home's inhabitants.  If the radon-222 undergoes decay while inside the body, it has no way of getting through all of the material in the body (alpha particles can be blocked by several pieces of paper they are so large).  This means that this ionizing radiation will be absorbed by some part of the body, with the most likely candidate being the lungs.  The only known health effect of radon is the increase in chances of contracting lung cancer. Scientists put the number of deaths due to lung cancer caused by radon exposure each year at  between 7,000 and 30,000 people¹ .


Since we know that radon exposure can cause lung cancer, it would seem that we would also know how to prevent it.  However, the situation is not so simple.  There is a growing body of evidence that we all need some exposure to radioactive substances, i.e. if we were to seal ourselves off completely from radioactive substances, it would do more harm than good.  Furthermore, not everyone is at extreme risk due to radon gas.  Different areas of the U.S. have different levels of uranium-238 in the ground, which corresponds to different levels of radon gas at the surface.  If you live in one of the areas that does not have high radon levels, you probably do not need to worry about radon gas in your home.  There is also evidence that lifestyles can effect your chances of contracting lung cancer if you live in a high radon zone.  Some studies have shown that smokers are much more likely to contract lung cancer than non-smokers if they are exposed to high levels of radon gas².  Considering the cost of remediating the problem of radon gas in the home, one does not just want to jump and do it if the risk are not there for them to contract lung cancer.

The websites below present information on radon gas in homes and on the effects of radiation in humans.

Radon Information

American Association of Radon Scientists and Technologists
EPA
University of Michigan

Radiation and Health Physics

Estimating Your Yearly Dosage (LANL)
Radiation and Life (Uranium Information Centre)

After reading through these and any other sites that you might find, answer the following questions

1 U.S. Environmental Protection Agency, http://www.epa.gov/iaq/radon/radonqa1.html, March 1, 2002
2 National Safety Council, http://www.nsc.org/ehc/radon/public.htm, March 1, 2002