Chemical Health Effects from Combustion of Natural Gas at Compressor Stations
By Wolf Eagle Environmental
Wolf Eagle Environmental has performed numerous emission tests near gas wells sites/ compression stations in the Barnett Shale geologic formation. Many of the sites tested by Wolf Eagle Environmental were confirmed through laboratory results to contain fugitive air emissions in levels that exceed Texas Commission on Environmental Quality (TCEQ) Effects Screening Level’s (ESLs). ESLs are based on data concerning health effects, odor/nuisance potential, and effects on vegetation. Many of the chemicals identified include known and suspected carcinogens, neurotoxins and reproductive toxins. They include primary compounds and their associated chemicals formed from the process of metabolism, commonly called metabolites.
Benzene – CAS Number 71432
The most important toxic effect of benzene is hematopoietic toxicity. Chronic exposure to benzene has been shown to lead to bone marrow damage, initially manifesting as anemia (reduced level of oxygen carrying pigment hemoglobin in blood), leucopenia (decreased total number of white blood cells in the blood) and thrombocytopenia (reduction in the number of platelet cells in blood) often with resultant marrow aplasia (incomplete or reduced growth or development), pancytopenia that can progress to myelogenous leukemia and death. Medical research indicates and supports Acute myelogenous leukemia (AML) and Acute Lymphocytic Leukemia (ALL) strongly correlated to high benzene exposures in humans. Benzene is often seen in the common acronym of BTEX (Benzene, Toluene, Ethylbenzene and Xylene). These compounds are some of the volatile organic compounds (VOCs) found in the oil and gas industry. Many of the BTEX chemicals were the first to be identified by EPA as “known human carcinogens” with harmful effects on the central nervous system.
Toluene – CAS Number 108883
The Central Nervous System (CNS) is the primary target for toluene toxicity in both humans and animals. CNS depression and death have occurred at higher levels of exposure. Symptoms include drowsiness, ataxia(lack of coordination, balance and gait, limb, eye movement or speech), tremors, nystagmus (involuntary eye movements) and cerebral atrophy. Neurobehavioral effects have been observed in occupationally exposed workers. Chronic inhalation of humans to toluene causes irritation of the upper respiratory tract and eyes, sore throat, dizziness, headaches and difficulty with sleep. Although toluene is classified as a Group D chemical, carcinogenicity reproductive and developmental effects including CNS dysfunction, attention deficits, and minor craniofacial and limb anomalies along with developmental delay have been recorded.
Xylenes – CAS Number 1330207 (m&p-) and 95476 (o-)
Xylene is a member of the common acronym BTEX due to its association with the other aromatic hydrocarbons. The primary uses of Xylenes industrially are as solvents and synthetic intermediates. The toxicity of BTEX and other aromatic solvents are similar. Xylenes are absorbed readily in the lungs and GI tract and quickly distributed to tissues through blood flow. There is evidence that chronic occupational exposure to Xylenes is associated with neurological effects. The m, o and p isomers of Xylenes vary somewhat in their capacity to affect different organs and have been associated with kidney injury and renal carcinomas.
Formaldehyde – CAS Number 50000
High concentrations of formaldehyde are identified as potential emissions at natural gas facilities.Formaldehyde is considered a suspected human carcinogen linked to nasal and lung cancer. It is also a suspected toxicant to the gastrointestinal tract, liver, immune system, reproductive system, respiratory system, and immune system. In concentrations of 25 to 30 ppm cause severe respiratory tract injury leading to pulmonary edema and pneumonitis. Formaldehyde can be fatal in high concentrations.
Carbon Dioxide – CAS Number 124389
Carbon dioxide is a major contributor to fugitive emissions from compressor stations. Although carbon dioxide is not considered a carcinogen it is considered a contributor to ozone and a major greenhouse gas (GHG) and an aphyxiant. It also has adverse health effects in higher concentrations affecting respiratory function and causes excitation followed by depression of the central nervous system. High concentrations of CO2 can displace oxygen in the air, resulting in lower oxygen concentrations for breathing. Therefore, effects of oxygen deficiency may be combined with effects of CO2 toxicity. Volunteers exposed to 7.5% CO2 for 15 minutes experienced inability to breathe (dyspnea) increased pulse rate, headache, dizziness, sweating, disorientation and visual distortion. Exposure to 6% for several minutes or 30% for 20-30 seconds affected the heart as evidence by altered electrocardiograms. Concentrations greater than 10% have caused difficulty in breathing, impaired hearing, nausea, vomiting, a strangling sensation, sweating, stupor within several minutes and loss of consciousness within 15 minutes.
Other Chemicals identified as fugitive air emissions from gas wells/compressor stations include:
Carbon Tetrachloride – High levels of carbon tetrachloride have resulted in damage to the liver (swollen, tenderness, changes to enzyme levels and jaundice) and kidneys (nephritis, nephrosis, proteinuria) in humans. Pulmonary edema (fluid in the lungs) has been observed in human exposed to high levels of carbon tetrachloride but his is believed to be due to injury to the kidneys rather than direct action of carbon tetrachloride on lung tissues.
Pyrene–a polycyclic aromatic hydrocarbon (PAH) with unknown long term health effects. Acute exposure to high levels showed a decrease in the weight of the kidney and an increase in the weight of the liver as well as slight changes in the blood. A number of PAHs have caused tumors inlaboratory animals that were exposed to PAHs through their food, from breathing
contaminated air and when it was applied to their skin. When pregnant mice ate high doses
of a PAH (benzo(a)pyrene) they experienced reproductive problems. In addition, the
offspring of the pregnant mice showed birth defects and a decrease in their body weight. Effects on humans have not been confirmed by laboratory tests.
Vinyl Chloride – The US Dept of Health and Human Services has determined that vinyl chloride is a known carcinogen. Brain cancer, lung cancer and some cancers of the blood may be connected with breathing vinyl chloride over long periods.
Phenanthrene – A polycyclic aromatic hydrocarbon (PAH) composed of 3 benzene rings. Phenanthrene is a toxic pollutant designated pursuant tosection 307(a)(1) of the Clean Water Act and is subjectto effluent limitations /Polynuclear aromatichydrocarbons [40 CFR 401.15 (7/1/87)] [366].
Fluoranthene – A polycyclic aromatic hydrocarbon (PAH) combination of a benzene ring and Naphthalene. Fluoranthene is found in many combustion products, along with other PAHs. Its presence is an indicator of less efficient or lower-temperature combustion. Fluoranthene is one of the U.S. Environmental Protection Agency's 16 priority pollutant PAHs and is a carcinogen.
Napththalene -Naphthalene (Naphthalin or antimite) is structurally composed of two benzene rings fused together. It is commonly found in mothballs and is known for its volatility and inflammable vapor. Napththalene in hydrogenated form is often used as low-volatility solvents in industrial operations. Exposure to large amounts of Napththalene may damage or destroy red blood cells and can lead to hemolytic anemia, often seen in children who have ingested mothballs. Symptoms related to low level exposures include fatigue, lack of appetite, restlessness and pale skin. Exposure to higher levels of Naphthalene may result in nausea, vomiting, diarrhea, blood in urine and jaundice. The International Agency for Research on Cancer (IARC) classifies Naphthalene as potentially carcinogenic to humans and animals. Acute exposures have also been correlated to cataracts in humans.
The process of compression of natural gas has the by-product of sulfides although not often illuminated. These compounds have been found to exist in geologic formations where sour gas is present. In addition, numerous fugitive air emissions tests conducted by Wolf Eagle has confirmed the presence of sulfide compounds in the Barnett Shale. These compounds are often seen in high concentrations and in levels which exceed TCEQ ESLs for Short-Term and Long-Term ESLs. Many of these chemicals are known for their capacity as neurotoxicants, degradative to muscle tissue and control, and as an asphyxiant. A few of the compounds are listed below:
Carbon disulfide** - CAS Number 75150 (carbon bisulfide, Dithiocarbonic anhydride)/Carbonyl Sulfide – CAS Number 463581
TCEQ has identified Carbon disulfide with a double asterisk (**) indicating the potential for disaster associated with this chemical. Carbon disulfide is used in the production of viscose rayon and cellophane, pesticides and used as a solubilizer for waxes and oils. It is a volatile colorless liquid associated with an “ether-like” odor and often combined with carbonyl sulfide in commercial use. Although it has a distinct and unpleasant odor the ESLs associated with this chemical are based on the adverse health effects rather than the noxious odor. It is highly flammable and highly reactive. At high concentrations may be life-threatening due to its central nervous system suppression. Physical signs of milder exposure may result in nerve damage to the lower-lateral leg and foot resulting in foot drags or mild limp.
Dimethyl disulphide – CAS Number 624920
The American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV) for Dimethyl disulphide is 0.5 ppm, 1.9 mg/m3 TWA, which is considerably lower than TCEQ limits. Health factors associated with exposure to Dimethyl disulphide include irritation of the respiratory system (nose, throat) as well as eye and skin irritation. Dimethyl disulphide is known to cause nausea and overall weakness. Vapor or air mixtures of Dimethyl disulphide above 24 °C may be explosive.
Methyl ethyl disulphide – CAS Number 20333395
Methyl ethyl disulphide, (methyldisulphanylethane) is known for its highly offensive odor. Although stable it is known to be highly flammable. Like Dimethyl disulphide, Methyl ethyl disuphide is a known eye and skin and respiratory irritant.
Trimethyl benzene, Diethyl benzene, Methyl-methylethyl benzene, Tetramethyl benzene, 1,2,4-Trimethyl benzene – CAS Numbers 25551137, 25340174, 25551137, 95932
It is an isomer in a family of aromatic hydrocarbon known for the capability as a solvent. These compounds present with an aromatic sweet odor and are known for their flammability and combustibility. They are also identified as hazardous and may contain similar adverse effects on humans as benzene.
Ethyl pyridine, 2-Methyl pyridine, and Diemethyl pyridine – CAS Numbers 536787, 109068, 5453678
These compounds are simple aromatic heterocyclic organic compounds used as a solvent and reagent. It is structurally similar to benzene and has a distinctive fish-like odor. It is highly reactive and is a precursor to numerous products (herbicides, insecticides, pharmaceuticals etc). Effects of acute pyridine exposure include dizziness, headache and nausea. It is currently being evaluated as a possible carcinogenic agent by government agencies.
Ethyl, methylethyl disulfide, Dimethyl trisulfide, Ethyl n-propyl disulphide
Although these compounds may vary in CAS Number they can be considered metabolites of the same basic chemical with the inference for use of similar Short-term and Long-term exceedences. This family of compounds is known both for its flammability and potential for offensive odor. They are known eye, skin and respiratory irritants with caution for respiratory exposures
Children exposed to the same levels of chemicals as adults may receive larger doses because they have greater lung surface area body weight ratios and increased minute volumes:weight ratios. In addition, they may be exposed to higher levels than adults in the same location because of their short stature and presence nearer to the ground. Chemicals with higher specific gravity than air (carbon dioxide, formaldehyde) can also provide an increased exposure to higher concentrations.
Occupational Safety and Health Administration (OSHA) standards often quoted are based on the ‘average’ male body weight and lung capacity with an eight (8) hour workweek exposure level. OSHA reference levels DO NOT incorporate exposure to sensitive populations including children and the elderly and ARE NOT comparable levels to residential exposures.
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