Radon Gas: Mechanisms, Effects, & Solutions

Abstract

This paper discusses radon gas, which is produced as a byproduct of the natural decomposition of uranium in rocks, soil, and water. Gas build-up in enclosed dwellings such as houses, apartment and office buildings, factories, and schools is a major concern in many parts of the country. Human exposure to high concentrations of this gas for extended periods of time can be extremely damaging to health. Lung cancer has the highest mortality rate of any cancer, and it is estimated that 15% of all cases of lung cancer in the United States result from exposure to radon gas. The government has taken steps to mitigate this problem, but the problem still persists. There are simple and inexpensive methods to drastically reduce the risks of radon gas exposure, and pursuing such mitigation could play a significant role in drastic reduction of lung cancer prevalence.

TABLE OF CONTENTS

INTRODUCTION 4

ENVIRONMENTAL MECHANISMS 4

BIOLOGICAL MECHANISMS 7

DISEASES & EPIDEMIOLOGY 9

LEGISLATION, POLICY, & RESEARCH 11

PREVENTATIVE MEASURES 13

CONCLUSION 15

REFERENCES 16

Radon Gas: Mechanisms, Effects, & Solutions

Introduction

Over 171,000 new cases of lung cancer are diagnosed annually in the United States, and nearly 130,000 people die of this disease every year. (Field, 2000) There is no other cancer that kills more often than this one, and what makes these deaths even more regrettable is the fact that most of them could have been avoided had irresponsible lifestyle choices not been made. While cigarette smoke is by far the leading cause of lung cancer, there is also another harmful carcinogen that plays an important role in the prevalence of this disease.

Radon is a natural radioactive gas that emanates from the ground into the air. This carcinogen is present in the environment worldwide, and its concentration depends on the highly variable uranium content of the soil. (Radon, 2005) It is produced as a byproduct of the natural decomposition of uranium in rocks, soil, and water. While the gas is relatively harmless in the outdoors, the real problem is the carcinogenic effects of gas build-up in buildings, factories, schools, and residential dwellings. The human senses are incapable of detecting the presence of this carcinogen, so one may endure long periods of high exposure without even being aware of it.

Radon gas is the second-leading cause of lung cancer and the leading cause in people who have never smoked. (Field, 2000) Nevertheless, it is entirely possible to prevent the risks related to radon gas exposure though mitigation.

Environmental Mechanisms

Radon gas is produced during the natural disintegration of uranium, a radioactive heavy metal that is found in abundance throughout the Earth's crust. (Radon, 2005) Therefore, it can be detected in nearly all rocks and soil, and also the ground water that comes into contact with them. If one were to dig up the top six feet of an acre of land, 50 pounds of uranium could be extracted from the unearthed soil, on average. (Krewski, 1999) As the case in all radioactive heavy metals, uranium disintegrates into lighter and lighter radioactive heavy metals until it ends up as stable, non-radioactive lead. This radioactive decay is absolutely essential because it heats up the Earth's core, producing half of the heat that is necessary for life on this planet to continue. While heat is a necessary byproduct of the conversion of uranium to lead, the process also involves the release of other more harmful byproducts. The abundance of uranium in the Earth's crust coupled with the fact that uranium has a half-life of 4.5 billion years means the amount of uranium on Earth will never dwindle, and therefore, neither will the levels of radon gas produced as a byproduct. This gas is also the heaviest known on Earth and is nine times heavier than air, so it tends to stay low to the ground.

Most types of soil only contain 1 to 3 parts per million (ppm) of uranium. However, some rocks like granite, shale, volcanic rock, and sedimentary rocks may have uranium levels as high as 100 ppm. (Krewski, 1999) As the uranium in these rocks disintegrates and produces alpha particles and radon gas, 10 to 50% of these particles and gas escape from the rocks and enter the underground "soil gas," which also contains moisture and biological decay from decomposition of fecal matter and deceased life forms.

The American unit of measurement employed in measuring radon gas content is the picoCurie (pCi). (Radon, 2005) One Curie (Ci) is measured as 37 billion disintegrations per second, and a picoCurie is one-trillionth of a Curie. The international unit of measurement for this gas is called a Bequerel per cubic meter (Bq/cm3), which equals one disintegration per second. Therefore, one picoCurie is equal to 37 Bequerels per cubic meter. However, it is easiest to use the picoCurie as the unit of measurement. (Radon, 2005)

The typical soil gas content of radon gas in the United States is between 200 and 2000 pCi per liter. (Krewski, 1999) Typically, the decomposition of uranium in one square foot of soil emits 130 pCi of radon gas per hour. This gas can be released directly into the air or move through underground pathways. The gas that moves underground usually turns into a solid after a few feet of travel, but it may travel even further among certain types of rocks and soil, particularly dry soil. Additionally, the gas is very soluble in water, meaning that it can travel much father if it enters underground water streams. Therefore, the network that distributes radon gas under the ground can be quite unpredictable, which explains why places with low uranium content in the soil can still have higher levels of radon gas.

Just like any other gas, radon gas follows a pressure gradient and moves from places of higher pressure to those of lower pressure. (Radon, 2005) The air pressure inside a building or house is lower than the pressure in the soil directly underneath the house. Indoor appliances like furnaces, hot water heaters, fans, and fireplaces also serve to lower