Recent flooding in Houston has sent crude oil and toxic chemicals into Texas waterways, and residents and experts say regulators are not doing enough to address the threat to public health and the environment.

Photographs taken by emergency management officials show oil slicks and other evidence of toxins spreading through the Sabine River on the Texas-Louisiana border from flooding in March, and new evidence is mounting that spills from oil wells and fracking sites increase when water levels rise.

Yet scientists and environmental groups say that the Railroad Commission of Texas, which regulates the state oil and gas industry, has yet to improve safety precautions.

Dr. Walter Tsou, a physician and past president of the American Public Health Association, told the El Paso Times on Monday that the risks of fracking fluid and other industry byproducts mixing in with groundwater was "a potential disaster."

"I'm sure it will get into the groundwater and streams and creeks," Tsou said of the photographs depicting downed tanks and plumes of oil. "In other areas, cattle that drank the fracking fluid actually died an hour after drinking it. There are potential carcinogens that can lead to leukemia, brain cancer, and other endocrine disruptors that can affect premature births. So it is not good to drink fracked wastewater."

Ken Kramer, water resources chairman of the Lone Star Chapter of the Sierra Club, added, "[The oil and gas companies are] looking after the fact at what might have happened. Because of that, it's pretty hard to figure out exactly what happened."

Meanwhile, Lon Burnham, a former Democratic state representative from Fort Worth, said regulators are incentivized to go easy on polluters who contribute a majority of the commission's campaign funds.

"They don't enforce," Burnham told the Times. "They don't fine. But they do whine about needing more money from the Legislature."