What is the average radiation exposure from radon

Radon is a colourless, odourless radioactive gas. It is formed by the radioactive decay of the small amounts of uranium that occur naturally in all rocks and soils. Radioactive elements decay and emit radiation. Any exposure to this type of radiation is a risk to health - radiation is a form of energy and can cause damage in living tissues increasing the risk of cancer. Radon is everywhere; formed from the uranium in all rocks and soils.

Outdoors everywhere and indoors in many areas the radon levels are low and the risk to health is small. The darker the colour on the radon maps , the greater the chance of a high radon level in a building. However not all buildings, even in the darkest areas, have high levels. The amount of radon is measured in becquerels per cubic metre of air Bq m The average level in UK homes is 20 Bq m For levels below Bq m -3 , your individual risk remains relatively low and not a cause for concern.

According to the EPA, the average indoor radon level is about 1. People should take action to lower radon levels in the home if the level is 4.

The EPA estimates that nearly 1 out of every 15 homes in the United States has elevated radon levels. Outdoors, radon generally disperses and does not reach high levels. Average levels of radon outdoors, according to the EPA, are about 0. In the workplace, people working underground, such as some types of miners, are among the most likely to be exposed to high levels of radon.

High death rates from lung problems among miners in some parts of the world were first noted hundreds of years ago, long before people knew what radon was. Studies of radon-exposed miners during the s and s confirmed the link between radon exposure and lung cancer.

Higher levels of radon exposure are also more likely for people who work in uranium processing factories or who come in contact with phosphate fertilizers, which may have high levels of radium an element that can break down into radon. Being exposed to radon for a long period of time can lead to lung cancer. Radon gas in the air breaks down into tiny radioactive elements radon progeny that can lodge in the lining of the lungs, where they can give off radiation.

This radiation can damage lung cells and eventually lead to lung cancer. Cigarette smoking is by far the most common cause of lung cancer in the United States, but radon is the second leading cause.

Scientists estimate that about 20, lung cancer deaths per year are related to radon. Exposure to the combination of radon gas and cigarette smoke creates a greater risk for lung cancer than either factor alone.

Most radon-related lung cancers develop in people who smoke. However, radon is also thought to cause a significant number of lung cancer deaths among people who don't smoke in the United States each year. Some studies have suggested that radon exposure may be linked to other types of cancer as well, such as childhood leukemia.

But the evidence for such links has been mixed and not nearly as strong as it is for lung cancer. Because radon and its progeny are absorbed mainly by inhaling, and because the radiation they give off travels only a short distance, it is unlikely that radon would affect other tissues in the body. The evidence that radon causes lung cancer comes from studies in people and studies done in the lab.

These studies also show that the overall risk of lung cancer from radon is even higher in people who smoke and people who used to smoke.

Some long term studies of uranium miners have found that they had higher risks of certain other cancers. They may instead be linked to uranium dust or other exposures in the mines. Studies in lab animals have also shown an increased risk of lung cancer with exposure to radon. These studies revealed that breathing in radon and its progeny increases the risk of lung tumors.

The risk is higher if the animal breathes in both cigarette smoke and radon. In some animals, the risk of certain other cancers was also increased.

In lab studies using human cells, radon and its progeny have also been shown to cause damage to chromosomes packets of DNA and other types of cellular damage. These types of changes are often seen in cancer cells. Several national and international agencies study different substances in the environment to determine if they can cause cancer.

A substance that causes cancer or helps cancer grow is called a carcinogen. The American Cancer Society looks to these organizations to evaluate the risks based on evidence from laboratory, animal, and human research studies. Based on animal and human evidence, several expert agencies have evaluated the cancer-causing potential of radon. One of its goals is to identify causes of cancer. The EPA lists radon as the second leading cause of lung cancer and the number one cause of lung cancer among people who don't smoke, estimating it is responsible for about 20, lung cancer deaths every year.

Other Cancers: Publication [1] paragraph A becquerel is a measure of radioactivity. One becquerel Bq is equal to one radioactive decay per second. This is the sum of the alpha particle decay energy of all the short-lived progeny of radon in a volume of air. The SI unit is joule per cubic metre J m Publication 65 [2] paragraphs The potential alpha energy … of an atom in the decay chain of radon is the total alpha energy emitted during the decay of this atom to stable Pb….

Next, by visiting the selected homes and buildings and after adequate briefing of the dwellers and gaining their consent and filling the questionnaires, the CR39 detectors were installed at the desirable locations based on the U. After collection, the detectors were placed in a water bath that contained 6. Then, they were rinsed with distilled water and dried. Table 1 shows that the mean and standard deviation SD of the concentration of radon gas in the sampled buildings in the City of Shiraz were The concentration of radon gas in residential homes Table 1 indicates that the concentration of radon gas in old buildings in the city of Shiraz was greater than it was in new buildings.

A possible reason may have been the small number of samples that we obtained. Table 1 indicates that the concentration of radon gas in the bedroom was greater than the concentration in the living room. Table 1 indicates that the mean concentration and SD of radon gas at the ground floor were greater than they were on the second floor and above. The results of the Mann-Whitney Statistical Test showed that the concentration of the radon gas differed depending on the floor that was sampled i.

Table 1 indicates that the average concentration and SD of radon gas in buildings that used blocks and cement were greater than they were in buildings that used brick and cement. This means that the type of materials used had no effect on the concentration of radon gas. However, as Table 1 shows, in this study, there were far fewer buildings constructed with block and cement i. Perhaps if the number of samples were greater, the difference in the concentrations might become statistically significant.

Table 1 indicates that the maximum concentration of radon gas occurred in the buildings with ceramic flooring. According to the results obtained from the mean concentration of radon gas in the residential units, the annual mean dosage in mSv per year by the residents in the City of Shiraz due to indoor radon was determined using the UNSCEAR model 33 :.

According to the results obtained, the average annual effective dose of radon gas in residential homes for the residents in the City of Shiraz was 1. In recent years, natural exposure to radon gas and its decay products in residential homes has become a global problem and has raised concerns as a result of their negative impact on human health. The average concentration of radon gas in residential homes in the City of Shiraz was A comparison of the results in the present study and the results of other studies on the measurement of the concentration of radon gas is given in Table 2.

Since the results of the present study indicated that 49 out of the households that were studied had at least one person smoking cigarettes, the risk of lung cancer will increase, and it is necessary to educate and inform the people through the responsible organizations in the City of Shiraz. The average concentration of radon gas in this study was less than the average reported by Haddad 24 , which was a study conducted in Shiraz between and on homes in two consecutive six-month periods.

The difference in the concentration of radon gas was due to the difference between the sampled homes, the number of samples, as well as the sampled floors. The U. However, according to the results of the present study, the average concentration of radon gas in all measured samples was lower than this value.

The average concentration of this gas reported in various cities were quite different, e. Therefore, by boosting the allocations and increasing the level of public awareness concerning the hazards of radon gas, it is recommended that more precise studies be conducted to determine the parameters that influence the penetration of radon gas into the buildings.

Therefore, due to the fact that radon gas has been proven to be the second cause of lung cancer around the world, it is necessary to take relevant measures to reduce radon in homes that have radon concentrations higher than the world standard.

The results of a study conducted by Molavi in on apartments in Mashhad showed that, in According to the U. The concentrations of radon gas in the indoor air of However, On average, in the U. The average annual dose received by every person from natural sources is 2.

However, it is noteworthy that parts of the city of Ramsar are situated in northern Iran, and they have the highest rate of natural radioactivity in the world as a result of the hot springs that contain radium The studies by Yousefi et al. EPA standard. The Danish Ministry of Health has announced that 4. The levels of radon in buildings change substantially with the passage of time and the aging of the used materials The average annual effective doses resulting from the radon gas in old and new buildings in the City of Shiraz were 1.

The dose received in the old buildings is higher than the doses received in the new buildings that are attributable to radon gas 1. The concentrations of radon gas in the newly-built buildings in the City of Shiraz were less than the maximum acceptable concentration set by the ICRP. A study by Haddad 22 in the City of Yazd suggested that the concentration of radon gas in old buildings is higher than that in new buildings. Measurement of the concentration of radon gas should be made at a point in the building that is regularly used by the residents and located at the lowest level, e.

The results of the present study indicated that the concentration of radon gas in the bedroom was higher than the concentration in the living room.

The results of the study by Yousefi et al. EPA has proposed that, for all buildings, the amounts of radon gas must be measured on the floors below the third floor The results show that the average annual effective doses of radon for residents living on the ground floor and above the first floor in the City of Shiraz were 1.

Therefore, the dose received at the ground floor is equal to the dose intake attributable to radon gas 1. Radon gas has a density of 9. So, the concentrations of radon gas in the basement and on the ground floor are higher than the concentrations on other floors Therefore, as one moves to the higher floors, the concentrations of radon gas are reduced significantly, and, consequently, the dosage received by the residents of such buildings are reduced.

The amount of gas in the indoor air of the homes located on the third floor is significantly different than the amount in the basement of the building. The basement of the buildings contained the highest concentration of the gas People inside their homes are protected from too much radiation of radioactive materials that are emitted from the outside environment.

But the construction materials are an important source of radon inside these places, and, among them, the materials that were extracted from the Earth are the most important 23 , The annual effective dosages in homes that were built with bricks and cement or with blocks and cement were 1.