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Air Emissions from Natural Gas Operations

Questions and answers about air emissions from natural gas operations, including their effects on human health and how the TCEQ is monitoring for them.
Many different chemicals (mostly methane, ethane, propane, butane, etc.) are associated with air emissions from natural gas operations. The chemical benzene is considered to be the primary risk driver.
The TCEQ has conducted extensive air monitoring to characterize air emissions from natural gas operations. In general, problems identified during short-term investigations were sporadic and were almost exclusively related to odor issues. Long-term air monitoring has not shown any chemical at levels of health concern.
The major components of emissions from natural gas operations (e.g., methane, ethane, propane) are not considered toxic; however, these gases can pose an asphyxiation hazard at very high concentrations in an enclosed environment, as would be the case after a gas leak in your home. We do not routinely monitor for methane, but we do for ethane and propane.

With respect to benzene, the main risk driver associated with air emissions from natural gas operations, typical long-term outdoor benzene levels near natural gas operations are from 0.2 to 0.3 parts per billion (ppb). Higher benzene concentrations can be found in very large industrial areas (like the Houston Ship Channel area) where annual average benzene concentrations at TCEQ air monitors are near 1.0 ppb. Indoor benzene levels are typically higher, ranging from about 3 to 4 ppb; a smoker’s home or a bar can have levels of about 7 ppb, because benzene is in cigarette smoke.

Hydrogen Sulfide
Hydrogen sulfide gas may be associated with emissions from natural gas operations in some areas of the state and, when present, may be found at higher concentrations than in other areas. Facilities with hydrogen sulfide emissions must meet state regulations to ensure adequate protection of human health.
All air-monitoring data collected by the TCEQ in the state is accessible on the TCEQ Web page. The TCEQ Oil and Gas Web page has information on air monitoring conducted in areas with oil and gas development and production. If you need help interpreting the results e-mail us at or give us a call—toll-free at 877-992-8370 or local at 512-239-3900.
Generally, this process is driven by complaints and findings during TCEQ investigations.
Some chemicals associated with air emissions from natural gas operations are odorous. Sulfur-based compounds can cause a rotten-egg odor. There may be diesel or gasoline-like odors as well. You may contact your TCEQ regional office if you’d like to file an environmental complaint.
for information on what kinds of equipment or operations can cause the odors you are experiencing.
Not necessarily. Many chemicals can be smelled at much lower concentrations than the concentrations expected to cause adverse health effects.
Health and safety
Odorous levels of some chemicals, including sulfur-based compounds and some volatile organic compounds, may give you a headache or make you feel sick to your stomach. At very high concentrations, some chemicals associated with natural gas operations can cause different types of health effects including problems with the kidney, liver, or nervous system. Daily, long-term exposure (i.e., for years) to very high concentrations of benzene is associated with acute myelogenous leukemia. We haven’t monitored short-term chemical concentrations that would be expected to cause short-term health effects.
We use Air Monitoring Comparison Values (AMCVs) to evaluate risk from monitored concentrations of chemicals associated with air emissions from natural gas operations. We look at both short-term and long-term exposure scenarios.
Short-term AMCVs are used to evaluate chemical concentrations measured in short-term air-monitoring samples (preferably one-hour sample durations) for the potential to cause acute adverse health effects or odor. Long-term AMCVs are used to evaluate chemical concentrations measured in long-term monitoring samples that have been averaged for at least 12 months for the potential to cause chronic health effects.
AMCVs are set to protect sensitive people including children, the elderly, and people with pre-existing health conditions like asthma. Generally, we do not have enough information to predict what concentrations of chemicals might affect people with multiple chemical sensitivity.
We would recommend that you work with the family member’s physician to determine if he or she is being exposed to anything in the environment that might affect that condition. You can also contact your regional office if you are concerned about potential emissions from the facility.
Visit our Environmental Complaint Web page.