Noble Gas: Indoor Air Pollutant Or Friend?

The noble gases are a group of chemical elements with similar properties. They are placed in group 18 of the periodic table and include helium, neon, argon, krypton, xenon, and radon. While they are present in the Earth's atmosphere, they only exist in trace amounts. However, human activities can introduce noble gases into the environment, leading to indoor air pollution. One example is the use of helium in balloons and airships, which can escape and contribute to air pollution. Additionally, radon, a radioactive noble gas, can be found in some building materials and is released into indoor air, posing health risks to occupants.

Argon is the third most abundant gas in the atmosphere

Air is a mixture of gases, most of which are naturally occurring. The dry composition of the atmosphere is made up of mostly nitrogen and oxygen, with fractional amounts of argon, carbon dioxide, and trace amounts of other gases, such as helium, neon, methane, krypton, and hydrogen. Nitrogen makes up about 78% of air, while oxygen makes up about 21%.

The discovery of argon is attributed to English physicist Lord Rayleigh and chemist Sir William Ramsay in 1894. They isolated argon from air contained in a test tube standing over a large quantity of weak alkali, with an electric spark sent across wires insulated by U-shaped glass tubes. Argon was also discovered independently by the French chemist Henri Moissan in 1895, though he failed in his attempts to react argon with fluorine.

Argon is an inert gas, meaning it is stable and does not react readily with other elements. This lack of chemical reactivity has been significant in the development of theories of atomic structure, as proposed by Danish physicist Niels Bohr in 1913. Bohr suggested that the outermost shell of noble gases always contains eight electrons, contributing to their stability.

While argon is naturally occurring and abundant in the atmosphere, it can also be present in indoor air as a result of human activities. Indoor air pollution, or poor indoor air quality, can be caused by the release of gases and particles from combustion sources such as gas stoves, tobacco smoke, and wood-burning. These sources can emit pollutants such as carbon monoxide, nitrogen dioxide, fine particles, polycyclic aromatic hydrocarbons (PAHs), and formaldehyde, which can have toxic effects on human health, particularly for vulnerable individuals such as young children and people with asthma or heart and lung diseases.

Radon is a radioactive noble gas

Radon (Rn) is a radioactive noble gas that is a member of the group 18 noble gases. It was first identified in 1900 by German chemist Friedrich E. Dorn and was established as a member of the noble-gas group in 1904. Radon is formed as a product of the radioactive decomposition of radium compounds. The nuclei of radium atoms spontaneously decay by emitting energy and particles, including radon atoms.

Radon is present in the Earth's atmosphere in very small amounts, and its major commercial source is the air, from which it is obtained by liquefaction and fractional distillation. It is also found in natural gas wells. Radon is a significant indoor air pollutant, and its presence in homes can have adverse health effects.

Radon is a colourless, odourless, and chemically unreactive gas. It is formed by the radioactive decay of radium, which is a naturally occurring element found in rocks and soil. Radon can accumulate in buildings and become a health hazard due to its radioactivity.

The gas can enter buildings through cracks in foundations, gaps around service pipes, and other openings. It can also be released from building materials such as concrete, which is made with natural materials such as granite. Radon can also be found in water, especially in areas with high levels of radon in the soil.

Radon exposure is the second leading cause of lung cancer after smoking. When radon gas is inhaled, it increases the risk of lung cancer due to its radioactive nature. Radon progeny, or decay products, can attach to airborne dust and be deposited in the lungs, emitting alpha radiation that damages lung tissue.

Carbon monoxide is a major indoor combustion pollutant

Noble gases are a group of chemical elements that have similar properties. They are called noble gases because they are inert and do not react readily with other elements. Noble gases include helium, neon, argon, krypton, xenon, and radon. They are present in the Earth's atmosphere but only in very small amounts.

Now, while noble gases are not considered indoor air pollutants, there are other gases that are. Carbon monoxide (CO) is a major indoor combustion pollutant and a known toxic gas. It is colourless, odourless, and tasteless, making it difficult to detect without a specialised detector. CO is produced by the incomplete combustion of carbon-containing fuels, such as wood, petrol, coal, natural gas, and kerosene. In homes, common sources of carbon monoxide include clogged chimneys, wood-burning fireplaces, gas burners, and heaters without proper safety features. Tobacco smoke and vehicle exhaust in attached garages can also be significant sources of indoor carbon monoxide exposure.

The danger of carbon monoxide lies in its ability to deprive the body of oxygen. When inhaled, CO binds to red blood cells, taking the place of oxygen and forming carboxyhaemoglobin. This reduces the blood's ability to carry oxygen to vital organs and tissues, resulting in hypoxia or oxygen deprivation. Prolonged exposure to high levels of carbon monoxide can lead to serious health issues and even death. Symptoms of carbon monoxide poisoning include headaches, fatigue, dizziness, confusion, and in severe cases, unconsciousness and death.

The health risks associated with carbon monoxide have led to the implementation of safety measures and regulations. For instance, California's Carbon Monoxide Poisoning Prevention Act of 2010 mandates the installation of approved carbon monoxide detectors or alarms in dwellings with fuel-burning appliances or attached garages. Similar requirements have been extended to care facilities and day care centres, highlighting the importance of monitoring and mitigating carbon monoxide levels in indoor environments.

To minimise the risk of carbon monoxide poisoning, it is crucial to ensure proper ventilation in indoor spaces, particularly when using combustion appliances or burning fuels. Regular maintenance of fuel-burning equipment and ventilation systems is essential to prevent the build-up of carbon monoxide. Additionally, the use of carbon monoxide detectors can provide early warning of elevated CO levels, allowing occupants to take necessary actions to ventilate the area or evacuate if necessary.

Cooking emissions are linked to respiratory disease

Cooking emissions have been linked to a range of respiratory issues. The World Health Organization (WHO) estimates that one-third of the world's population, or 2.1 billion people, use cooking methods that may be detrimental to their health. The emission of particulate matter (PM) is a byproduct of any cooking method, but some methods produce more particles than others.

Gas stoves, for example, emit higher levels of nitrogen oxide (NOx) than electric stoves. Exposure to high levels of NOx can lead to chronic lung disease, severe asthma symptoms, and respiratory illnesses, especially in vulnerable individuals such as young children. Gas stoves that are not properly ventilated are a significant source of particulate matter. However, using an electric stove does not eliminate the need for ventilation, as proper ventilation is always essential to minimising indoor air pollution.

The type of cooking and the ingredients used also influence the concentration and chemical properties of emissions. Frying and grilling meat at high temperatures produce harmful organic compounds, including aldehydes, ketones, acids, and polymerized fats. Aldehydes, such as formaldehyde, acetaldehyde, and acrolein, can cause local irritation in the airways when inhaled. These compounds are formed from the destruction of sugars and fats and the pyrolysis of proteins and amino acids during the cooking process at high temperatures.

Kitchen workers are at a particularly high risk of exposure to these cooking fumes, which are associated with an increased prevalence of respiratory symptoms such as wheezing, shortness of breath, chest tightness, chronic cough, phlegm, and chronic bronchitis. Additionally, studies have shown that exposure to cooking fumes can lead to an acute reversible decrease in lung functional capacity.

To mitigate these risks, it is essential to ensure proper ventilation in the kitchen. Using an extractor fan or a high-efficiency range hood to vent pollutants outdoors is recommended. Opening a window can also help clear pollutants and protect against short- and long-term health effects from cooking activities.

Nitrogen dioxide is a gaseous pollutant and a component of smog

Nitrogen dioxide, or NO2, is a gaseous air pollutant composed of nitrogen and oxygen. It is a member of the nitrogen oxides group of gases, commonly referred to as NOx. NO2 is formed when fossil fuels such as coal, oil, methane gas, or diesel are burned at high temperatures. It is also produced during the burning of natural gas (methane) both outdoors and indoors.

Nitrogen dioxide is a significant indoor and outdoor air pollutant. It is one of six widespread air pollutants for which there are national air quality standards to limit their levels in the outdoor air. Monitors have shown that the highest concentrations of outdoor NO2 are in large urban regions. Levels are higher on or near heavily travelled roadways. Those who live near emission sources are at a higher risk of health impacts from nitrogen dioxide pollution.

NO2 is a pungent, reddish-brown gas that contributes to the reddish-brown haze characteristic of smoggy air. It has a pungent smell and is harmful to human health. Scientific evidence suggests that exposure to NO2 could likely cause asthma in children. It is closely linked to asthma and other respiratory conditions, and can cause a range of harmful effects on the lungs. NO2 is also an important precursor of ozone, a major component of smog.

Ozone is formed from photochemical reactions with pollutants such as volatile organic compounds, carbon monoxide, and nitrogen oxides emitted from vehicles and industry. Due to the photochemical nature of ozone, the highest levels are seen during periods of sunny weather. Nitrogen dioxide contributes to the formation of several other air pollutants, including ozone, nitric acid, and nitrate-containing particles.

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