Microplastics from Texas Bays Are Washed Out to Sea, New Study Says

The first study of microplastics in Texas coastal sediment was funded through a local environmental activist’s landmark legal victory over plastic pollution, one of many such research projects.

A recent study found surprisingly low levels of harmful microplastics in the sediments of Texas bays that are notorious for plastic pollution. This led researchers from the University of Texas at Austin to conclude the microplastics were being swept out to sea. 

“They move around much easier than we thought,“ said study co-author Cornel Olariu, a research associate professor at UT’s Jackson School of Geosciences, in a May 14 news release. “They’re a threat to everything up to us.”

The fine-grained plastic particles absorb chemicals and can accumulate in wildlife and humans. Previous research has identified health impacts from microplastic accumulation including genetic damage, neurological effects and cancer risk. 

The Texas study focused on the Matagorda Bay system, where two major plastics manufacturers operate Formosa Plastics and Dow Chemical. The bay system has high documented levels of pollution from plastic nurdles—granular pellets that float on the water. 

Microplastic, or plastic powder, comes from many sources. It can be released directly from manufacturing plants or be slowly produced as floating nurdles break up. It washes down rivers alongside other plastic trash and it rubs off plastic fishing nets that are used in the bay.

Researchers on Matagorda Bay took 122 samples of bay sediments to test for microplastic grains and fibers. It was the first time such measurements have been taken in Texas bay sediments, the study said. 

The samples showed levels that were hundreds or thousands of times lower than other documented bayside environments.

“It is surprising there are not more microplastics present in the sediment,” the study said. “The wind regime, shallow water, and permanent connection to the Gulf of Mexico lead to the high flushing rate of fine-grained material and microplastics out of the bay during storm events.”

The research drew funding from the Matagorda Bay Mitigation Trust, a fund established in 2019 by a historic settlement agreement between Formosa Plastics, which operates a 2,500-acre complex on the bay system, and Diane Wilson, a local shrimper who sued the company over its prolific plastic pollution. 

“It’s getting to be really well known as an avenue to do scientific research,” Wilson said. “I’m getting calls from all kinds of people.”

The fund began with $50 million in 2019 and has since received an additional $29 million in ongoing pollution penalty payments from Formosa. 

The fund has put millions of dollars into scientific research on the Matagorda Bay system. One study, published in January, examined the toxicity of microplastics to fish and shellfish. Another is examining the impacts of microplastics on microscopic lifeforms, and another is measuring concentrations of toxic PFAS chemicals in the bay.  

The University of Texas sediment study was published in March in the journal Environmental Science and Technology.

Its findings defied expectations, given the large volumes of plastic pellet pollution documented by Wilson and others. The researchers credited it to differences in buoyancy. While plastic pellets float to the surface, the grains of plastic powder are often suspended within the water column. That makes them more susceptible to disturbance by seasonal storms and capture by regular currents that run out to sea. 

“Given that plastic pollution ultimately enters the Gulf of Mexico, this system should be the focus of future research,” the study reported. 

Cover photo:  Diane Wilson holds a bottle with PVC plastic powder, a type of microplastic, collected in the Matagorda Bay system in December 2024. Credit: Dylan Baddour/Inside Climate News