Labor History: Fatal Explosion at IMC Fertilizer Plant Exposed Preventable Hazards, Human Toll of Unsafe Work Practices

May 1, 1991 – A failed waste-gas vent compressor ignited a fatal explosion at a nitropara­ffin plant in Sterlington, LA, killing eight employees and injuring 120 people, including 42 workers and over 70 residents nearby. Union o­fficials and inspectors identified a history of safety issues at the ammonia fertilizer plant, and workers represented by the Oil, Chemical and Atomic Workers International Union (OCAW) Local 4-786 reported safety concerns before the blast. The reports were left unfixed, and the blast hurled debris nearly a mile from the plant, causing extensive damage to the facility and harming the surrounding community.

The disaster at the plant, owned by the ANGUS Chemical Company and operated by the International Minerals and Chemicals (IMC) Fertilizer Group, exposed systemic failures of safety procedures, preventable hazards, and the human toll of unsafe work practices. The explosion was caused by unprotected piping and a lack of safety systems. During its investigation, the Occupational Safety and Health Administration (OSHA) asserted that more than 200 employees were exposed to fire and explosion risks due to the improper safety practices.

Following the disaster, OCAW acted as a watchdog, increasing its involvement in the OSHA investigation and inspection process, which led to record OSHA penalties of about $10 million for each company—the largest fines OSHA had ever levied at the time. However, OCAW denounced the settlement terms, calling it a “sweetheart deal” that allowed the companies to settle without admitting guilt, viewing the terms as insufficient for a disaster that harmed so many workers and the community. The union pushed for stricter safety reforms, resulting in the implementation of key measures, including more detailed inspections, identification of hazardous locations, provision of protective gear, enhanced evacuation planning, installation of explosion-mitigation systems, and the inclusion of workers in the process.

In the years that followed, OCAW used the plant disaster as an example to advocate for stronger OSHA oversight and to highlight specific failures in OSHA-mandated protocols designed to prevent catastrophic incidents. Criticisms of its oversight, enforcement, and settlement practices led OSHA to implement significant operational reforms throughout the 1990s. However, until OSHA was created, no formal, enforceable standards for workplace safety and health had even existed. OSHA set the baseline standard for protecting workers on the job.

Congress formed OSHA in 1971 after passing the Williams-Steiger Occupational Safety and Health Act in 1970. Tony Mazzocchi, an OCAW labor leader, helped lead the fight to pass the act. He laid bare how handling dangerous chemicals without proper safety protocols increases occupational injuries, diseases, and deaths. He organized public meetings for OCAW, other union members, and scientists to testify about those dangers to workers’ safety and health. The heavy media coverage and pressure from labor unions and workers compelled Congress to pass the act. Since its passage, workplace injuries have fallen from 10.9 cases per 100 workers in 1972 to about 2.3 cases per 100 workers in 2025. Workplace deaths have also plummeted from around 14,000 annually in 1972 to 5,283 in 2025, while the size of the U.S. workforce has more than doubled in that time.

Corporations have often tried to repeal OSHA, prioritizing profits over safety. However, the incident at the IMC plant, and many others like it, reinforce why workplace safety regulations exist, and how OSHA protections, paired with safety provisions in collective bargaining agreements, help keep workers safe on the job.