Last year at Oxy’s La Porte plant, a midnight explosion and fire drew a major response by emergency personnel. More recently, some of the firefighting wastewater from the Ohio train fire, which contained toxic chemicals, was trucked back to a processing facility in Deer Park, Texas, which borders La Porte. And in 2012, a train carrying vinyl chloride — bound for the same plastics plant in New Jersey that was the destination of the Ohio train — derailed and plunged into a creek, releasing 23,000 gallons of the chemical and prompting evacuations of nearby homes.

OxyVinyls plans to spend $1.1 billion to expand and upgrade its La Porte plant, the company said in regulatory filings last year. Shintech, the world’s largest producer of PVC, and whose shipments also burned in the Ohio disaster, according to freight records, is spending more than $2 billion to build out its operations in Texas and Louisiana.

Oxy officials didn’t respond to several requests for comment.

Overall, chemicals companies have invested more than $100 billion in new or expanded plants since 2010, with another $99 billion in the works, according to a tally from the American Chemistry Council. Much of that investment has been in plastics.

As plastic production has proliferated, more hazardous materials have been on the move. According to data from the Association for American Railroads, rail shipments of chemicals used in plastic production grew by about a third over the past decade.