Poisonous hydrogen sulfide gas is known in the oil industry for its ability to kill quickly, but less attention has been paid to those community members breathing in lower levels of the gas in their daily lives. The Examination teamed up with the Houston Chronicle to investigate how H2S is affecting Texans. 

Here's what to know about how the gas can affect you. 

What is H2S? 

Sometimes called “sour gas,” H2S forms underground as plants and organisms decay, and can get released into the air during oil production or when it escapes from aging or improperly sealed storage tanks. The Permian Basin of West Texas and other oil-rich regions around the world are naturally saturated with hydrogen sulfide, and it can be spread by fracking and injecting water to push out more oil. The gas also plagues other industries.

Is hydrogen sulfide gas deadly?

Yes, at high levels, hydrogen sulfide can quickly knock you down, causing you to lose consciousness, stop breathing and die. Texas regulations were tightened after a 1975 leak killed nine people. The gas occasionally kills oil-field workers whose jobs require them to be close to the tanks and wells. In 2019, a worker and his wife, who had gone looking for him, were killed in a cloud of H2S inside an Odessa facility, leading to an ongoing criminal case against the oil company. Many oil-field workers keep H2S monitors on them to alert them to high levels of the gas, which has a strong smell similar to rotten eggs. 

Can non-lethal levels of hydrogen sulfide make you sick?

According to the U.S. Centers for Disease Control and Prevention, exposure at lower levels can irritate the eyes and respiratory system, and can cause convulsions, dizziness and insomnia. Some Texans living near facilities leaking the gas describe nausea, headaches, coughing, asthma and rashes. Chronic exposure to very low concentrations has been linked to neurological, respiratory and other health problems. Reported effects of chronic exposure include fatigue, incoordination, poor memory, hallucinations, personality changes, shortness of breath and increased visits to the emergency room, according to an Environmental Protection Agency toxicologist’s report.

Can you smell hydrogen sulfide?

Yes, hydrogen sulfide is known for its telltale rotten egg smell. However, exposure to high levels of H2S, or lower levels for extended periods of time, can cause people to lose their ability to smell it, so relying on smell alone is not advised.

What are the limits for H2S in the air?

The United States doesn’t have national air quality standards for H2S. Under pressure from the oil industry, the EPA took the gas off its list of “hazardous air pollutants” decades ago, leaving regulation to the states. Texas’ limit for residential areas is 0.08 parts per million averaged over 30 minutes.

Where are the H2S hotspots located?

The Houston Chronicle and The Examination mapped for the first time more than 54,000 wells in Texas that, according to state records, are part of oil and gas operations that have tested for high concentrations of H2S. The levels would be “immediately dangerous to life or health,” if the gas were to leak and people were to be exposed directly. 

How is H2S regulated in Texas?

The Texas Commission on Environmental Quality regulates air quality, while the Railroad Commission of Texas oversees the oil and gas industry. 

These agencies are supposed to enforce regulations designed to protect residents who live near oil and gas facilities. Yet, some residents have struggled for years to get state officials to help when these facilities repeatedly leaked poisonous gasses in their communities.

How are schools located near oil wells monitored for H2S in Texas?

Dozens of schools are located near H2S hotspots, but there isn’t a uniform system for monitoring them. The Texas Commission on Environmental Quality does continuous H2S monitoring at only one school in the Permian Basin. Though H2S levels have gone over the state limit there, the school principal said he wasn’t informed. Another school has its own H2S alarm system, though school officials don’t know what levels it has detected. Railroad Commission inspectors frequently checked on storage tanks located near another school, repeatedly finding H2S leaking there.

How can I report an H2S-related complaint in Texas?

Can I detect H2S levels myself?

Basic portable H2S monitors, which have alarms for when gas levels are high enough that you should leave the area, can be used for personal protection and can be purchased for under $100. More expensive monitors can detect lower levels and track H2S concentrations over time.

Where else is H2S a problem? 

The gas affects workers and communities in other oil-rich regions around the world, from Canada to Iraq to Kazakhstan. It also plagues other industries, such as paper mills, and can build up in any storage area with decaying material like manure or sewage.

What are the key findings of the investigation?

Gas leaks from oil and wastewater tanks near homes and schools in Texas

An estimated 78,000 people live near oil and gas operations that have tested for high concentrations of H2S, according to an analysis by the Houston Chronicle and The Examination. The gas concentrations are high enough to be “immediately dangerous to life or health,” if the gas were to leak and people were exposed directly.

Dozens of schools are nearby too. Regulators measured H2S at levels above the state limit at one school, but the principal said he wasn’t told. State investigators have documented repeated H2S leaks from storage tanks near other schools.

Texas regulators downplay the risk

The state has a limit for hydrogen sulfide in the air, but regulators broadly disregard it, downplaying the health threats. There are only three sites in the Permian Basin, the highest producing oil field in the United States, where the state continuously tests the air for hydrogen sulfide. At two of them, gas levels exceeded the state limit 1,590 times since the state started measuring in 2020. 

The Railroad Commission of Texas, which regulates the oil industry, doesn’t map storage tanks or the locations of dangerous hydrogen sulfide concentrations.

Nearby residents struggle to get help

When Texas inspectors find the gas venting into the air, companies seldom face penalties. Instead of making repeat offenders upgrade their facilities, inspectors return to the same leaking oil tanks again and again as problems persist for years. State inspectors and analysts repeatedly fled one neighborhood that was being investigated for H2S when gas was detected at alarming levels, including in 2022. But the problem persists — an H2S monitor placed by a reporter in one family’s yard detected the gas frequently soaring past the official state limit this spring.

State environmental agency hasn’t updated its watch list in years

The Texas Commission on Environmental Quality said it uses its Air Pollutant Watch List to focus resources on areas with “elevated concentrations of air toxics,” but the agency hasn’t added to that list since 2007, ignoring the shale boom that brought an explosion of oil and gas activity across the state. The list doesn’t include any site in the Permian Basin. Meanwhile, increased oil production has boosted the population in the region, bringing more people to live close to wells and storage tanks.

Texas H2S rule needs more teeth, some say

The state’s H2S regulations were tightened after an oilfield leak of hydrogen sulfide killed nine people in Denver City in 1975. Known as Rule 36, the regulations require energy companies operating in high-H2S areas to measure concentrations, train their employees, put up warning signs and, in some cases, monitor for leaks. A retired regulator said the rule should be updated to include "some teeth and some muscle" so that residents are better protected.