### element:

Radon
* Comes from the earth through cracks in the foundation and from well water.
* Most radon enters the home through soil, but it can also come through well water.
* Some radon also stays in the water
  - can also enter homes through drinking water supplies
  - is always present because it is formed during the breakdown of uranium and radium
* affects only certain types of homes.
* are chemical elements
  - gases
  - noble gases
  - radioactive substances
* by-product of naturally occurring radium, which product of uranium
  - the decay of uranium and can travel for miles underground
* can be a problem in schools and workplaces, too.
* cancer causing, radioactive gas.
* cancer-causing gas produced by the breakdown of uranium in soil, rock, and water.
* cancer-causing, radioactive gas.
* carries radioactive particles that can cause lung cancer.
* causes lung cancer in people when they have been exposed to it for a period of time
  - no symptoms of irritation and no acute illness
  - thousands of deaths each year
* colorless and odorless gas
  - radioactive gas that is produced naturally in the soil
  - odorless, but radioactive, gas created by the natural breakdown of uranium
  - chemically-unreactive inert gas
  - gas at normal temperatures
  - odorless gas that is naturally emitted from the earth
* colorless, chemically unreactive inert gas, it is the densest gas known
  - odorless gas produced by the decay of elements in the soil
* colorless, odorless gas that is given off by rocks in the ground
  - occurs naturally and is found everywhere at very low levels
  - gas, a radioactive byproduct of radium
  - radioactive gas that is in every home
  - odorless, invisible gas that occurs naturally
* colorless, odorless, radioactive gas found in the earth's rock and soil
  - produced as a result of radium decay
* colorless, odorless, tasteless gas created when uranium in soil and rock breaks down
  - that naturally occurs in rocks, soil, water, and air
* comes from rocks, soil, and well water that contains uranium and radium
  - the natural breakdown of uranium in soil, rock and water
* comes from the natural decay of radioactive materials in rock and soil
  - uranium and radium that is found in nearly all soils
  - radioactive decay of naturally occurring uranium in the soil
* comes from the soil surrounding and beneath the home
  - beneath the house, especially soil that contains uranium
* common radioactive gas that is given off by soil and rocks.
* decay by-product of radium
  - product of radium, which in turn decay product of uranium
* easily enters homes through cracks and other openings in foundations.
* emits a particles
  - an alpha and mutates to polonium
* enters a building through cracks, dirt floors, drains, and porous concrete foundations.
* enters a home through cracks and holes in the foundation and can also be found in well water
  - in walls, basement floors, foundations and other openings
* enters homes through foundations and can build up to dangerous levels
  - small foundation cracks
  - the body through the respiratory system, and particles embed in the lungs
* enters the home from the ground through cracks and holes in the foundation
  - through cracks and openings in the foundation
* escapes harm- lessly into the air when water is being treated for use in a municipal system.
* exists in all types of homes.
* fluctuates daily and seasonally.
* includes atoms.
* is after smoking the second leading cause of lung cancer
  - an element
  - appreciably more soluble in organic liquids than in water
  - at the bottom of the column of noble gases
  - by far the greatest single source of radiation to the general public
* is colorless and the most dense gas known
  - at standard temperature and pressure and it is the most dense gas known
  - colorless, odorless, tasteless, and chemically inert
  - easy and inexpensive to detect
  - especially dangerous because it gas and can easily enter the lungs
  - highest in small buildings with basements and no balanced mechanical ventilation system
  - highly radioactive and has a short half-life
  - invisible, tasteless, and odorless
  - more common in some areas than others
  - most concentrated in the lowest level of the home
* is odorless and colorless
  - odorless, tasteless, and invisible
  - often more highly concentrated in basements, ground floors and first floor homes
  - present in indoor and outdoor air
* is present in some degree in all soil, groundwater and air
  - spring waters
  - varying quantities in the atmosphere and in soils around the world
  - radioactive and concentrates when it enters a building
* is second only to cigarette smoke in causing lung cancer
  - smoking as the leading cause of lung cancer death
* is second to smoking as a cause of lung cancer
  - the major cause of lung cancer deaths
* is soluble in water and in body fluids
  - organic events
  - underground streams can carry it long distances
  - tasteless, odorless and colorless
  - the by-product of uranium decomposing deep in the earth
* is the heaviest known gas, nine times heavier than air
  - noble gas and natural decay product in the uranium decay series
  - killer of underground miners or even inhabitants of granite cottages
  - largest contributor to our natural background radioactive exposure
* is the most potent environmental carcinogen to which the general public is exposed
  - studied of all carcinogens
  - only element in the series that is gas
  - radioactive decay product of uranium
* is the second leading cause of cancer
  - death from lung cancer in the United States
  - lung cancer behind smoking
  - lung cancer deaths in the United States, after smoking
  - lung cancer in the United States today
  - lung cancer in the United States, after smoking
  - lung cancer, after smoking
  - lung cancer, behind cigarette smoke
  - lung cancer, second only to smoking
* is the second-leading cause of lung cancer in the United States, just behind tobacco smoke
  - single largest source of radiation exposure
  - ubiquitous and can be found in all states and countries around the world
  - undetectable by human senses, and can only be measured by a special test
  - waived, as it is associated with groundwater
* lasts for several days before it begins to break down.
* likely causes more lung cancers than second hand tobacco smoke
  - is released to outdoor air before reaching home faucets
* member of the zero- valence elements that are called noble gases.
* monatomic gas, which has no colour, taste, or odour.
* moves into the disturbed zone and the gravel bed underneath from the surrounding soil.
* natural gas emitted from uranium
  - part of the earth's atmosphere
* natural radioactive gas emitted from the earth
  - formed by uranium decaying in the earth's soil
  - that seeps into buildings from the ground
* natural, radioactive decay product of radium, which is itself a decay product of uranium.
* occurs in places where there's a lot of uranium in the underlying rock
  - the environment mainly in the gaseous phase
  - naturally and radioactive gas
* occurs naturally in all soils
  - the soil and in high enough concentrations cause of lung cancer
  - when traces of uranium in Tennessee's rocks radioactively decays
* only affects certain kinds of homes
  - people who smoke
* quickly decays into so-called daughter particles
  - decays, emitting tiny radioactive particles
* seeps from the soil into homes in many parts of the country.
* travels into houses generally by a combination of diffusion and advection.
* well-know air pollutant today.