The use of natural gas in the home, as fuel for heating or cooking, is a health issue for healthy individuals and especially for people with environmental illnesses, allergies, and chemical sensitivities. The concentration of combustion products from natural gas appliances in indoor environments has wide-ranging health consequences. Furthermore, the natural gas itself causes adverse reactions in sensitive individuals.

Hydrogen sulfide (H2S) is a highly toxic compound present in some natural gas deposits. During its removal from the sales gas, the refinery process emits sulfur dioxide and hydrogen sulfide into the air. There is epidemiological evidence that this has adverse effects on children's respiratory systems.

Some natural gas deposits have a high concentration of hydrogen sulfide (H2S), which poses significant environmental and health concerns. Hydrogen sulfide is a colourless, highly toxic gas with a strong smell of rotten eggs (Gosselin et al 1984:198). It is produced naturally by decaying organic matter, and is also released from sewage sludge, oil refineries, liquid manure, sulphur hot springs, and natural gas.

Human toxicity of hydrogen sulfide: H2S is toxic in concentrations as low as 50 ppm, and concentrations of 0.1-0.2% are usually fatal within minutes (Gosselin et al 1984:199). Since the body has a mechanism for detoxifying sulfide, toxicity of H2S is related more to concentration than length of exposure (Gosselin 1984:199).

Although H2S has a strong odour, continual low level exposure leads to loss of the sense of smell. This makes it possible for humans to be unknowingly exposed to dangerous levels. Low level of H2S result in irritation of the eyes, nose and throat. Moderate levels can cause headache, dizziness, vomiting, as well as cough and difficulty in breathing. High levels can cause shock, convulsions, coma and death. Survivors of acute toxic exposure to H2S sometimes experience neurological dysfunction, such as amnesia, tremor, disturbance of equilibrium, or more serious brain damage, as well as persistent ill-health following exposure (Gosselin 1984:200). Although acute toxicity for higher concentrations of H2S is established, there are few studies on chronic low level exposure to H2S (Schechter 1989). This is a serious deficiency.

Accidental release of concentrated H2S may result from infrequent blowouts of natural gas wells which have high levels of H2S. Although the risk is low, the acute toxicity of H2S implies that this may have a serious affect on the health of nearby human populations.Radioactive radon and radium are present in natural gas. Radon is known to contribute to the development of lung cancer. Using natural gas as a fuel source in the home can increase the total concentration of indoor radon.

Naturally Occurring Radioactive Material (NORM) is found in soil, water, petroleum, natural gas, coal, lignite, phosphate, geothermal waste, wastewater, humans and animals . One of the most common NORMs is radon (Rn222), a colourless, odourless gas produced from Radium decay and a decay product of radioactive uranium. Ra226 has half life of 1,602 years, while radon has a short half-life of only 3.8 days, after which it emits 4 highly reactive "radon daughters".

Radon is commonly found in natural gas deposits, ground water and soil, and is a common indoor air contaminant in basements where it seeps through the foundation and is concentrated in enclosed spaces. Nova Scotians are already exposed to radon in soil and water. Because of the geology of Nova Scotia, it is highly likely that natural gas deposits off Sable Island also contain high levels of radium and radon. Household use of natural gas containing radon is a human health issue. When used in the home, natural gas may be a source of radon exposure because it is released upon burning . The levels of radon in gas in the home depends on the concentration of radon in the gas deposit as well as the distance of the source of gas from the home. The level of radon in sales gas decreases with distance from the natural gas deposit because of its short half-life of 3.8 days, when half will deposit as lead in the pipes before reaching the homes.

Sulfur-containing odourants are added to sales gas to enable leaks to be detected by scent. Although these odours are present at concentrations which are not considered toxic to most individuals, their odour can cause nausea and headaches in healthy individuals. The reaction to these odourants is likely to be much more severe in people with chemical sensitivities.

Because natural gas itself has no odour, small amounts of odourants are added to the sales gas so that gas leaks can be recognised before concentrations reach a dangerously flammable or explosive level (intended concentration is such that odour will be detected at approximately one-fifth of the lower flammability limit, or about 4-24 grams of odourant per km3 gas (Environment Canada 1984:30). These odourants are sulfur compounds, and include mercaptans (ethyl mercaptan (methanethiol), methyl mercaptan, isopropyl mercaptan, T-butyl mercaptan), thioesthers and thioaromatics (Environment Canada 1984:30). The potential toxicity of these odourants raises issues concerning the safety of the use of natural gas in homes, especially for people with multiple chemical sensitivities. Adequate testing on odourant toxicity has not been conducted using people with chemical sensitivity. This should be part of the impacts assessment of the proposed Sable pipeline project. AEHA-NS requests for funding for such testing were denied.

Mercaptans are a common air contaminant. They contain sulfur and are able to capture elemental mercury. Exposure to Mercaptan odours can cause nausea or headaches. In high concentrations, mercaptans can cause cold extremities and rapid pulse, and may induce unconsciousness with cyanosis (Sax and Lewis 1987:600), or even death (Gosselin et al 1984:116). Mercaptans are dangerous when heated to decomposition because they emit highly toxic SOx fumes. Furthermore, they will react with water, steam or acids to produce toxic and flammable vapours, and can react violently with oxidizing compounds.

Methanethiol (also known as methylmercaptan, mercaptomethane, thiomethyl alcohol) is a mercaptan gas which is commonly used as an odourant in natural gas. Its unpleasant odour is detectable by most people at 1 part in 140 million, however it may be detected at much smaller concentrations by highly sensitive individuals. Animal toxicological studies have shown that 0.16% methanethiol, 3.3% ethanethiol or 9.6% dimethyl-sulfide induce coma in 50% of rats exposed during a 15 minute period. However, the effects wear off after 30 minutes away from the gas. Human toxicity is proven through the case of a man found comatose within an hour after respiratory exposure to an unknown concentration of methane-thiol. The man experienced severe transient haemolytic anemia, and died 28 days after exposure, never recovering from the coma. It is suggested that methanethiol toxicity is similar to that of hydrogen sulfide.