How Radon Causes Lung Cancer

Radon Gas is the Most Potent Carcinogen in your Home

You cannot see radon gas. And you cannot smell it or taste it. But it may be a problem in your home. As the only gas in the decay chains of radioactive heavy metals, radon and its floating radioactive products can easily get into human body by inhalation. Whenever you breathe in air containing radon, it increases your risk of getting lung cancer. The National Academy of Sciences and the Environment Protection Agency (2003) estimate that in the U.S., radon in homes causes 21,100 lung cancer deaths each year.

Radiation is called the "complete carcinogen" because, unlike chemical carcinogens, it alone can initiate, promote and propagate cancer. The primary site of radioactive exposure to most people is their home. The average person receives a higher radiation dose from radon at home than from all other natural or man-made sources combined.

Radon is a proven and very potent "Class A" carcinogen. Safety limits on toxins or carcinogens in food or water are set at levels thousand times less lethal than what is the risk from radon in an average American home. "Radon in homes causes more deaths than fires, drownings and airplane crashes combined." (EPA)

The Lung Cancer Crisis

After smoking "radon is the second leading cause of lung cancer." (Surgeon General) Among non-smokers, radon is the No. 1 cause of lung cancer deaths.

Lung cancer is the leading cancer killer of all Americans, both men and women, claiming 160,000 lives every year - more than breast cancer, prostate cancer, and colorectal cancer combined. Over 171,000 new lung cancers are diagnosed in the U.S. each year.

The leading three causes of cancer deaths
Men Women
Lung cancer 33% Lung cancer 24%
Prostate cancer 12% Breast cancer 18%
Colorectal cancer 10% Colorectal cancer 11%

Lung cancer is the deadliest of all cancers – its 5-year survival rate is only 10 to 14 percent. By the time people develop symptoms (shortness of breath, coughing, bloody sputum), the cancer has grown to the size of an orange or has spread to other organs. While the death rates for many types of cancer have been declining during the last 60 years, the age-adjusted incidence and mortality rates for lung cancer have been rising.

There is a lung cancer crisis, particularly among women. Lung cancer deaths have increased by 20% among men during the past two decades but by 150% among women, and in the 1990's alone, lung cancer deaths of white females have increased 60%.

Children Are More Susceptible to Radon

Children are known to be more radiosensitive than adults. Analysis of Hiroshima victims showed a higher incidence of lung cancer among those who were exposed to the radiation blast as children. A single x-ray to the abdomen of a pregnant woman in the first six weeks of pregnancy leads to a 50 percent increase in cancer and leukemia risks to the child. The gamma rays emitted by radon progeny are far more energetic than x-rays but the emitted alpha and beta particles are even more harmful.

Radiation risk to embryos is higher than to children, which in turn is higher than to adults. Children are more susceptible to radon-induced cancer due to their rapidly dividing cells and higher breathing rates. It is compounded by their heavier exposure to radon by spending more time inside the house and/or in the basement.
(Source: Dr. Gordon Edwards - Estimating Lung Cancers)

Recent research in Europe confirms that radon is much more harmful to children than to adults. Lung cancer incidence as a result of radon exposure is estimated to be about ten times higher for people exposed at the age of about 15 than at about 50.

However, the onset of lung cancer takes decades. EPA has not found convincing epidemiologic evidence of increased risks to children (except to the smallest ones) and its radon guidelines for homeowners are thus based solely on the lung cancer risks to adults.

Radioactive Lining of the Lungs

After radon gas is inhaled, it readily dissolves in the blood and circulates through the body, organs, and tissues, until it is again exhaled through the lungs or skin. Equilibrium is established between the ambient and the internal radon concentrations. Since the radioactive half time of Radon-222 is 3.8 days, most radon atoms harmlessly leave the body before they can disintegrate.

The problem is not radon, but rather the radioactive particles it produces. As radon atoms undergo radioactive decay, they disintegrate into radiation and radon progeny ("daughters") - solid heavy metal particles of lead, polonium, and bismuth. These minute, electrically charged and chemically active particles float in the air, and when breathed in, some (less than 1%) get trapped permanently in the airways. The accumulated radioactivity in the airways is proportional to the radon level - at the 4 pCi/L level, about 600,000 radioactive particles get trapped in the lungs every hour.

The deposition in the lungs depends on whether the particles are attached to airborne dust or smoke, or unattached. Unattached daughters lodge deeper in the lung, which explains the severity and the type of radon-induced deep-lung cancers in non-smokers.

The Glow of Ionizing Radiation

Most of the radiation dose to humans is not from radon itself but from the radon daughters, most notably Polonium-218 (radioactive half-life 3 minutes, alpha particles), and Po-214 (half-life 0.164 milliseconds, alpha), along with Bismuth-214 (half-life 19.7 minutes, beta). A half-life is the time period in which a half of the atoms decays into another element; the shorter the half-life, the more intense radiation. The radon daughter particles go through the decay chain of radioactive heavy metals until a half of the atoms finally reach the stable non-radioactive Lead-206 after more than 22 years.

At each step of the decay chain the radon progeny particles emit ionizing radiation - alpha and beta particles, and gamma rays. Ionizing radiation, which has enough power to knock out electrons from atoms and convert them to ions, kills or damages living cells, causing genetic mutations and cancer.

The inhaled radon daughter particles accumulate in the lungs and tracheobronchial tree, particularly in bifurcations. Since the bulky alpha particles cannot penetrate more than a fraction of a millimeter into the lung tissue before smashing into an atom, damage is concentrated on the epithelial cells in the immediate area. The result of such concentrated radiation is much more severe than if the radioactive dose was distributed throughout the whole body.

The radon daughters also emit beta particles and gamma rays that travel farther through the body. Beta particles travel up to 1 to 2 centimeters in human tissue. Most gamma rays, being more energetic than x-rays, pass through the body to the outside. Because the absorbed beta and gamma radiation is spread over a larger volume, it is less concentrated and less harmful. The concentrated ionizing radiation of heavy alpha particles is much more damaging and accounts for more than 85% of the damage to lungs.

The radon isotope Thoron (Rn-220) emanates from stones or building materials rich in thorium, which is as common as uranium. It undergoes similar radioactive decay and emits the same alpha, beta, and gamma radiation, but is much less common in indoor air (at most 20% of the total) because its half-life is only 56 seconds. Thoron is difficult to measure and is ignored in the NAS or EPA calculations.

A Single Radon Atom Can Cause Lung Cancer

Carcinogens cause random damage to the chromosomes and DNA molecules contained in the nucleus of the cell. Most of these cells are either killed or sterilized. However, in a very few cases, one of these damaged cells may survive the injury and still be capable of reproducing. Such a cell may begin to proliferate in an undifferentiated or "cancerous" manner. Most cancers are of monoclonal origin, that is, they originate from damage to a single cell.

Even a single alpha particle can cause major genomic changes to the cell's DNA, including mutation and transformation. Since these effects take place in a random manner at the cellular level, there is no such thing as a "harmless" dose. Even allowing for a substantial degree of cell repair, the passage of a single alpha particle has the potential to trigger cancerous growth of cells that it does not kill outright.

Alpha Particles from Radon Do Not Even Have to Hit the Cell

The Los Alamos National Laboratory researchers discovered in 1997 that alpha particles emitted by radon do not have to hit the nucleus of a cell to damage the cell's DNA, which resides in the nucleus. Moreover, the alpha particles do not even have to hit the cell - a bombardment of the surrounding medium produces chemical radicals inside the cells, which cause DNA damage.

This negates the widely held assumption that alpha particles cause genetic changes only through direct traversals of cell nuclei. Merely the interaction of alpha particles with the fluids that line the lungs damages the DNA of nearby cells. Exposure even to the lowest doses of alpha emission produces the very reactive chemicals within cells and their production increases with the alpha-particle dose. This confirms that radon is dangerous even at very low levels - there is no "safe" threshold. The research also suggests that radon may be disproportionately more harmful at lower concentrations.

A more recent study at Columbia University (2001) provides clear evidence that a single alpha particle can induce mutations and chromosome aberrations in cells that received no direct radiation exposure to their DNA. These results indicate the need to reassess the potential genotoxic effect of low dose radiation and suggest that the assumption of direct proportionality in radiation may significantly underestimate the risk of low-dose radiation.

Does Radon Cause Other Diseases?

It is generally assumed that inhaled radon gas is quickly exhaled and has little time during its circulation through the body to deposit its radioactive products in human organs, tissues, or bones. However, the story may be more complicated. Some scientists believe that radon dissolved in the blood may cause additional diseases beside lung cancer. In addition to the gas, one-third of the inhaled radon decay particles also pass through the lungs into the blood stream and then, get trapped. 

As we breathe in through the skin, the air also carries radon gas. Some studies suggest that the radiation dose to the basal layers of the skin is high with a consequent risk of skin cancer.

Radon gas is soluble in lipids and accumulates in lipid tissue throughout the body with the highest concentration in the brain, bone marrow, and nervous system. But none of its heavy metal daughters are soluble in the lipids and consequently, remain trapped in the brain and bones, where they continue to emit gamma radiation and alpha particles. Several studies indicate that radon also causes leukemia ("cancer of the blood") and other types of cancers.

Researchers at the University of North Dakota discovered that the presence of radioactive radon daughters in the brains of non-smoking persons with Alzheimer’s and Parkinson’s disease was 10 times (!) greater than it was in the brains of persons with no previous evidence of neurological disorders. Interestingly, the geographic distribution of Parkinson’s disease mortality is considerably higher in states with a greater radon potential.

Animals exposed to high concentrations of radon progeny display beside lung carcinoma emphysema, pulmonary fibrosis, and a shortened life span.

Nevertheless, the risk of other cancers or diseases is much lower than that of lung cancer. The National Academy of Sciences estimates that radon ingested with water causes about 20 stomach cancer deaths per year, which is 1,000 times fewer than from lung cancer. Since the radiation dose to other organs is much smaller than from radon decay products deposited in the bronchial epithelium, ICRP estimates the cancer risk to other organs at about 2% of the lung cancer risk.

Possible Genetic Damage

Ionizing radiation causes random damage to the chromosomes and DNA molecules contained in the nucleus of the cell, including genetic mutations that may affect future generations. Substances having a carcinogenic effect also have genetic and teratogenic effects. Damage to the DNA of reproductive cell, e.g. gamma irradiation of sperm, can lead to genetic deficiencies in the offspring, and if an embryonic cell is damaged, the normal development of the fetus can be disrupted.

In areas of high natural background radiation, an increased frequency of chromosome aberrations has been observed. "Any individual dose, however small, is able to produce gross malignancies and deformities if it is administered to a sufficiently large population."
(Source: Dr. Gordon Edwards - Estimating Lung Cancers)

Lung Cancer Treatments

Lung cancers start in bronchial tubes and lungs. The danger of a destructive spread of cancer is acute, because lungs are connected to other organs of the body by a complex network of blood vessels. Lung cancer often spreads to the larynx, liver, brain, bones and kidneys.

Without surgery, this condition is currently considered incurable. Surgery to remove all of the lung (pneumonectomy) or part of the lung (lobectomy) may be recommended if the cancer is at an early stage. Only 25% of tumors can be removed surgically. However, symptoms can be relieved or controlled. Radiation treatment and anticancer drugs to stop the spread of the tumor or destroy cancerous cells may be recommended.

The survival rate after 5 years is only 10 to 14 percent. Lung cancer causes more deaths than any other form of cancer and its incidence is increasing.

When Can a Person Exposed to Radon Finally Relax?

Never, unless already well advanced in age. The most intense radiation from radon progeny occurs during the first hours, when polonium and bismuth quickly decay into radioactive Lead-210. But then follows a much slower decay through bismuth, polonium and lead radionuclides into stable Lead-206. The total half-life of these nuclides is over 22 years. If a person has been exposed to radon, 75 percent of the radon progeny in lungs will become "harmless" lead particles after 44 years.

When an alpha particle damages a cell to make it cancerous, the onset of lung cancer takes a minimum of 5 years but most often 15 to 25 years, and even longer. The decades-long decay of radon progeny and the slow onset of cancer make it almost impossible to measure the increase in death rates caused by radon in a mobile population. Therefore, most lung cancer studies are based on the thousands of miners exposed to radon or on extensive animal, cellular and radiological research.

Only few people exposed to radon will develop lung cancer. However, once exposed to radon, the lung cancer risk lasts for one's lifetime. Children and young people naturally have a higher risk of developing lung cancer during their lifetime.

Minimize the Radon Level in Your Home!

Many of the 21,000 lung cancer deaths caused by radon in the U.S. each year are preventable. The "action" and "consider action" limits of 4 or 2 pCi/L are merely cost/benefit guidelines - EPA has left the radon mitigation decision and responsibility up to the individual homeowner. EPA has warns the public: "Any radon exposure has some risk of causing lung cancer. The lower the radon level in your home, the lower your family's risk of lung cancer."

You should always try to reduce the radon level in you home to a practical minimum. The target of the U.S. Radon Abatement Act is the natural level outdoors (average 0.4 pCi/L). Whether you current level is 30 or 3 pCi/L, or if a mitigation system is already installed, reducing radon in your home by 90 or 50 percent will reduce the risk to your family by 90 or 50 percent.

RadonSeal penetrating concrete sealer has made radon mitigation simple and affordable for homeowners. Many achieve radon levels below 2 pCi/L or, when starting at below 4 pCi/L, reduce radon by at least 50%. Moreover, homeowners can avoid the unsightly piping and energy losses of a fan system, as well as a plume of heavy radioactive gas.

... Julia was diagnosed with terminal lung cancer in September of 2003. She had never smoked a cigarette in her life, but she found out too late she and her husband Jack had been living in elevated radon concentrations for nearly 19 years... Read real-life stories about radon in homes and lung cancer.