Реферат: Radon In New Jersey Essay Research Paper
Radon In New Jersey Essay, Research Paper
RADON IN NEW JERSEY
From the beginning, life has evolved in the presence of natural background ionizing radiation. There are three principal types and sources of radiation that occur on earth. The first of which are cosmic rays, which impinge on the Earth from outer space. The second is from terrestrial radiation, which are released by the disintegration of radium, thorium, uranium, and other radioactive minerals in the Earth s crust. Finally, there is internal radiation, which are emitted by the disintegration of potassium-40, carbon-14, and other radioactive isotopes that are normally present within living cells.
There is an average total dose of radiation received from all three sources by a person residing at sea level, which is approximately .91 mSv per year1. However, a dose twice this size may be received by a person residing at a higher elevation where cosmic rays are more intense. A person living in a geographic region where the radium content of the soil is relatively high can also receive twice the dose of .91 mSv per year. In the latter form is what this paper is going to be concerned with. Radon a chemical element is a heavy, radioactive, noble gas. It is generated by the radioactive decay of radium. It is a colorless, odorless, tasteless gas, seven and a half times heavier than air and more than one hundred times heavier that hydrogen.
Radon is rare in nature because its isotopes are all short-lived and because radium, its source, is a scarce element. The atmosphere contains traces of radon near the ground as a result of seepage from soil and rocks, all of which contain minute quantities of radium. Radium consequently, occurs as a natural decay product of uranium present in various types of rocks.
By the late 1980 s, naturally occurring radon gas had come to be recognized as a potentially serious health hazard. The gas, arising from soil and rocks, seeps through the foundations, basements, or piping of buildings and can accumulate in the air of houses that are poorly ventilated. Exposure to high concentrations of this gas over the course of many years can greatly increase the risk of developing lung cancer. Radon is believed to be the single most important cause of lung cancer among non-smokers in the United States. Radon levels are highest in homes built over geological formations that contain uranium mineral deposits. Many homes in northern and central New Jersey are built on these types of formations.
Radon s health effects are primarily caused by alpha particle emissions of the radon decay products, polonium-218 and polonium-214. This radioactive disintegration in the air inside homes is of little concern because the emitted alpha particles are unable to penetrate the skin. There is not as good of protection in the lungs, and the alpha particles emitted inside the air passage in the lungs by some of the disintegrating decay products are sufficiently powerful to penetrate the epithelium and damage a layer of sensitive cells called basal epithelial cells. This damage can sometimes lead to lung cancer.
It is difficult to give precise information on the cancer risks from radon contamination in indoor air. It is apparent in studies of underground miners that high concentrations of radon in the air increase the chances of developing lung cancer.2 Exposure to large amounts of radon appears to increase the cancer risk. Quantification of the risk associated with indoor exposure to concentrations of radon that are lower than those found in the mine studies depends on what assumptions are made about the relationship between the dose of radiation received and the incident rate of cancer in those who receive the dose. Age and sex differences and other factors, especially smoking also influence the actual risk. A recent epidemiological study of household exposure risks appears to be reasonable. Estimates for radon deaths for the United States range between 5,000 and 20,000 deaths per year. This is about ten percent of the cancer deaths attributed to smoking.3
On the basis of risk assessments, as well as consideration of the technological feasibility of reducing indoor radon levels, the U.S. Environmental Protection Agency recommends that remedial action be taken to lower elevated indoor radon levels to an annual average level of below 4 picocuries per liter (pCi/l) of air. Lifetime exposure at this level could result in one to five cases of lung cancer in every one hundred people exposed, clearly a significant health risk.
Elevated levels of indoor radon were originally discovered in homes situated on the Reading Prong, a large geological feature spanning much of northern and central New Jersey. There is a potential major impact on the health of several millions of New Jersey residents exposed to radon. The problem is much greater than originally expected. Lowest floor radon test results exceeding 4 pCi/l were found in all parts of the state, as far south as Vineland, in Cumberland County, and as far north as Alpine, along the Palisades. In six counties; Hunterdon, Sussex, Warren, Morris, Somerset, and Mercer, the average radon values exceeded 4 pCi/l. In all but Atlantic County, at least one sample exceeded this value.
It is assumed that the distribution of radon concentrations across the state would tend to follow radium distribution as determined by underlying geology. Accordingly, the state is divided into six geologic provinces. The six provinces are; the Highlands, the Valley and Ridge, the Northern Piedmont, the Southern Piedmont, the Inner Coastal Plain, and the Outer Coastal Plain. The Highlands encompasses the area of the Reading Prong. Immediately northwest of the Highlands is the Valley and Ridge, and immediately to the south is the Southern Piedmont. While geologic considerations indicated that elevated radon would most likely to occur in the Highlands, certain rock types in the Valley and Ridge and in the Southern Piedmont were also known to have higher than average radium concentrations.4
There are ways in today s society of controlling indoor radon in these contaminated New Jersey homes. Elevated radon levels could be produced in houses by the entry of soil gas containing radon through openings in the concrete basement structures and could be reduced by reducing the soil gas flows. As the radon supply by diffusion through concrete was negligible compared to supply via soil gas, epoxy diffusion barriers against soil gas.5
There are four methods of controlling radon. The first is source removal, which is practicable only in cases where the source has been introduced into the local environment by man s actions. The second is to increase the resistance of the building fabric to soil gas entry, generally called sealing. The third is to increase the rate of removal of radon from the building by increasing the structure ventilation rate. Finally, the fourth method is to reduce the soil gas flow by reducing the pressure differential between the building and the soil. The last category generally is called soil ventilation.
Soil ventilation is typically the most important one for the case of high radon concentrations occurring from ordinary soil and rock. Often it has to be supplemented by sealing. The source removal is not pertenant to New Jersey s radon problems because the radon is a naturally occurring event. New Jersey homes have to be sealed to protect the homes from soil gas entry. The major problem with the basements in today s homes is that there is a space between the walls of the basement and the floor. The walls are built first and then concrete is poured in to make the floor. As the floor sets, the floor shrinks away from the walls leaving the gap for soil gas entry. This sealing can take care much of the problem but it can not be the only thing.
Increasing ventilation flow rate in a building to reduce the radon concentration is the simplest method of all and has the advantage that it requires no knowledge of foundation construction, soil conditions, or identification of entry routes. Ventilation can lead to a problem because it can get very expensive. In North and Central New Jersey, where the temperature is cold in the winter and hot in the summer, ventilation can be very expensive. The energy cost, and the equipment available suitable for house use can be very costly.
The collection system is an extremely effective method. The subsoil collection system must produce slightly subatmospheric pressures in the soil adjacent to each wall and the floor. This can be achieved by excavation around the building perimeter to install a perforated pipe and cutting the basement floor or slab, installing perforated pipes in the subfloor fill, and patching the floor. If an exhaust fan is used, it cuts the cost of the collection system considerably. In many cases, the collection network can be dispensed with entirely, and the existing structure utilized to control the airflow.6
When an area is identified as having elevated indoor radon levels, the housing resale and construction market is disrupted. Purchasers ask for a radon measurement before buying a home, and buildings with high concentrations become virtually impossible to sell. Given this, there are considerable financial incentives for homeowners to carry out mitigation work in their homes and for builders to produce houses with low radon levels.
In conclusion, the radon problem in New Jersey is not just a problem in the northwest every region in New Jersey has a problem with radon. The problem involves all buildings, homes, and places of business. It is not just an overly protective cause to get rid of radon. It causes serious health risks; seven per thousand causes of cancer are attributed to radon in northern New Jersey. While in Warren County twelve per thousand cases of cancer are attributed to radon. There are great methods of controlling indoor radon through extensive ways of protection and removal. Every home in New Jersey can attain a reading of less than 4 pCi/l with these ways of protection and removal.
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