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 Natural Gas
  Natural gas in the home contributes a number of different pollutants. These include products that exist in the gas itself (odorants, gas hydrocarbons, heavy metals and radon), products of incomplete combustion (nitrogen dioxide, carbon monoxide, fine organic particulates, polycyclic aromatic hydrocarbons and a small amount of volatile organic compounds such as formaldehyde) and contaminates due to the supply line (PCBs, dioxin, tars, oils, and waxes).

The individual pollutants in natural gas have health implications as individual substances. In addition they may act in combination with each other and with other indoor pollutants. The toxic effects of which may be additive and compounding. Although the conventional human health toxicity of natural gas has been assumed to be low, many people with chemical sensitivities react extremely adversely in the presence of even minute traces of natural gas.

Natural gas pollutants can induce or worsen allergy, asthma and chemical sensitivity. Exposure compromises the immune system and increases the risk for asthma attacks, waking with shortness of breath and tingling sensations in the extremities. Clinical studies show that the use of natural gas in the homes, schools, work places or even in the neighborhoods of environmentally sensitive individuals can exacerbate illness and inhibit recovery.

Natural gas has been found to be one of the most important sources of indoor air pollution. In Canada Mortgage and Housing Corporation's (CMHC) Clean Air Guide (1993), natural gas appliances (gas water heaters, furnaces, unvented space heaters and cook stoves) are identified as significant contributors of chemical contamination in the home. CMCH recommends replacement of these with electrical appliances (CMHC 1993:12).


The main ingredients in natural gas are Methane (98.90%), Ethane (00.16%), Propane (0.02%), and Nitrogen (0.87%). Mercaptan for odor is added to natural gas (0.5% vol. of final gas mixture)

Methane - the main component of natural gas, is believed to have low conventional toxicity and is simply considered an asphyxiant. Inhalation of high concentrations of methane can cause symptoms ranging from a craving for fresh air, rapid and irregular breathing, headache, fatigue and exhaustion, to loss of consciousness, convulsions and death from hypoxemia.

Radon - some natural gas deposits contain radioactive radon, which is known to cause lung cancer. Radon can be transported into buildings which use natural gas. Using natural gas as a fuel source in the home can increase the total concentration of indoor radon.

Heavy Metals - Some natural gas deposits have been found to contain high concentrations of toxic heavy metals, including lead, copper, mercury, silver, and arsenic. These can be transported into homes serviced with natural gas, and have recently been shown to accumulate as organometallic compounds on the burners of gas stoves. The collection and subsequent analysis of oxide coatings on domestically used gas burners found high levels of lead, mercury, copper and silver, and some arsenic. These substances are highly toxic and have the potential to bio-accumulate in the body creating potential for both neurological damage and chronic health problems.

Sulfur-containing odorants (mercaptans, thioesters and thioaromatics) are added to sales gas so that leaks can be detected by smell. These odorants contribute in the development of chemical sensitivities. In higher doses, these odorants are known to be toxic to healthy individuals, but in natural gas are present in concentrations commonly considered to be below the toxic threshold but still able to be readily detected by smell. The toxicity is much lower for people with environmentally induced illness, chemical sensitivity, asthma and allergy. Individuals with Multiple Chemical Sensitivity have symptomatic reactions to compounds at least two orders of magnitude lower than the established threshold for acute health effects. It is known that mercaptan odors can cause nausea and headaches in healthy individuals.

Mercury - odor additives such as Mercaptin capture mercury. Because mercury is a sometimes a component of natural gas, it may become affixed to the mercaptans and breathed in with the odor, thereby potentially increasing one's burden of highly toxic mercury.

Other contaminates found in rather steady-state in natural gas include: benzene, toluene, benzo-a-pyrene and benz-a-anthracene. PCBs, tars, oils, waxes and other "plug-flow" type chemicals are sporadic and appear in the appliance flame at aperiodic times, as can be demonstrated by observing a gas appliance flame's colors.

Combustion By-Products

Carbon monoxide (CO) - is an odorless, tasteless and colorless gas is an asphyxiant, and binds to hemoglobin with about 200 times the affinity of oxygen, thereby reducing oxygen transport to the tissues.

Water vapor - generated by natural gas combustion can be a transport mechanism for fine particulates and pollutants, and can transport them readily to the lung alveoli.

Nitrogen dioxide (NO2) health effects include: reduced defense against infection, exacerbation of asthma, allergies and lung diseases, and respiratory tract inflammation with manifestations of respiratory symptoms and lung function. It is probable that NO2 exposure from natural gas appliances can both contribute to the development of chemical sensitization and allergy, as well as both cause and increase adverse reactions in already sensitive individuals.

Fine particulates and polycyclic aromatic hydrocarbons - have an adverse effect on respiration and certain of these compounds are known carcinogens. There is evidence that suggest that natural gas and hydrocarbons may act as hormone (endocrine) disruptors (Colborn et al 1996).

VOCs and formaldehyde - produced in small quantities from gas combustion. Know to elicit severe allergic reactions. VOCs are believed to be sensitizing agents, and is thought to be a contributing factor in the development of sick building syndrome and multiple chemical sensitivity.

Dioxin - polyvinyl chloride (PVC) or other material containing chlorine used in any pipe or other equipment for the transportation or distribution of natural gas may introduce chlorine into the gas supply and can potentially lead to the production of dioxins, furans and other potentially harmful compounds as products of combustion. Dioxin is a know carcinogen.

Web sites for further info:

www.geocities.com/RainForest/6847  (Allergy and Environmental Health Association)
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Revised: July 05, 2017.

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