On Saturday, Nov. 15, a toxic chemical leak at a DuPont manufacturing plant outside of Houston killed four workers and hospitalized another, serving as another troubling example of the need for stronger chemical safety standards. The chemical involved in the leak, methyl mercaptan, can cause eye and lung irritation and can be fatal at high levels. Numerous other U.S. facilities use and store this chemical, including those featured in a new interactive map by the Center for Effective Government.

The DuPont Accident

Saturday’s incident occurred at a DuPont plant in La Porte, Texas (outside Houston), which uses methyl mercaptan to manufacture pesticides. The La Porte plant stores as much as 122,000 pounds of methyl mercaptan.

The chemical is also used at other facilities in a number of other processes, from refining jet fuel to plastic production. Methyl mercaptan is stored as a liquid but turns to gas when exposed to oxygen. The gas is colorless but can be readily identified by its rotten eggs smell. You’ve likely smelled it before, as it’s added to natural gas so that people can detect gas leaks in their homes.

In large amounts, however, methyl mercaptan can be deadly. The gas is heavier than air and spreads close to the ground, displacing oxygen. High levels of exposure can affect the central nervous system and cause unconsciousness or even death by asphyxiation. The gas is also extremely flammable and produces toxic fumes when burned.

The exact nature of the incident remains unclear, but reports have indicated that employees were responding to a leaking valve. The Chemical Safety Board, an independent federal agency, is currently investigating. The agency does not issue fines but instead reviews chemical accidents and makes suggestions for risk prevention and management. The agency noted that this is the first deadly methyl mercaptan incident they have investigated, and it raises many questions about how plants can prevent future fatalities. 

Mapping Chemical Risks

Following the DuPont accident, we mapped eighteen additional chemical facilities across ten states that use methyl mercaptan. Dots of incremental sizes identify the amount of methyl mercaptan stored onsite at these facilities.

click to open interactive map

While most of these facilities are chemical manufacturers that use methyl mercaptan in their processes, four of the facilities are railroad car service centers that clean train cars that carry hazardous substances. Other facilities include a petroleum refinery in Texas, two hazardous waste treatment centers (one in Ohio and one in Mississippi), and a plant that manages hazardous waste-derived fuels in Mississippi.

Eight of the 18 facilities using methyl mercaptan are in Texas, with four located in the greater Houston area (including DuPont’s La Porte plant). However, the plant storing the most methyl mercaptan is a Union Carbide chemical manufacturing plant in St. Charles, Louisiana, which stores up to 7.75 million pounds of the substance.

Additional facilities in the U.S. may also use methyl mercaptan but are not required to report it to the U.S. Environmental Protection Agency’s (EPA) Risk Management Program (RMP) because they fall below the 10,000-pound reporting threshold.

This map serves as an important tool for communities and their leaders to assess potential risks from an accident involving the release of methyl mercaptan. Users can locate facilities using this hazardous chemical and discover how many students go to school within these facilities’ danger zones. The map also provides links to additional information so users can follow up with facilities and insist they reduce risks by using the safest processes possible.

Methyl Mercaptan Not the Only Risky Chemical in La Porte

DuPont’s La Porte plant reports to EPA’s Risk Management Program (RMP). Nearly 13,000 other facilities report to RMP because they use or store large amounts of certain hazardous substances. Methyl mercaptan is just one of many chemicals regulated by RMP because of its high toxicity.

Despite the large amount of methyl mercaptan onsite at the La Porte plant, the chemical of most concern there is hydrofluoric acid. The plant holds enough of this toxic chemical that a leak could affect communities 25 miles away. This danger zone is home to 1.6 million residents and 580 schools (349,660 students). For more information on schools in chemical danger zones, visit our Kids in Danger Zones resources page.

Improving Chemical Safety

DuPont’s tragedy happened less than a month after EPA closed its comment period on improving chemical safety. Included in this “Request for Information” were many questions surrounding RMP facilities. They received around 100,000 comments from industry representatives, public interest groups, and the general public. The agency is currently reviewing these submissions and will likely announce any proposed rulemaking next spring.

One promising way to prevent chemical accidents is to require facilities to switch to safer chemical alternatives and technologies whenever feasible. Switching to less volatile or toxic chemicals and limiting the amount of chemicals stored on site reduces facilities’ danger zones, thus protecting workers and communities.

However, some industry representatives are opposed to safer alternative requirements and insist that they already have sufficient safety requirements in place. In response to our Kids in Danger Zones report in late September, the American Chemical Council released a statement highlighting their Responsible Care® program, which includes company-level policies for process safety, including managing potential risks and training employees to respond to them. DuPont, in fact, takes part in this program. However, while it is important for facilities to respond appropriately to accidents, more emphasis is needed on preventing accidents in the first place – and the most effective approach is to require safer alternatives.  

Unfortunately, accidents occur regularly at chemical plants. Some of these accidents cost lives or injure workers and community members. To effectively reduce these risks, EPA must move quickly to require that all RMP facilities use the safest technologies and chemicals available.