A new study reaffirming a higher rate of birth defects in the area has been handed to a federal agency to investigate whether refineries and chemical plants have played a role.

The follow-up study, released in December, found that birth defects are higher in Corpus Christi compared to the state even after the state researcher controlled for characteristics such as age, race and ethnicity that can sway the rates. Similar studies in the past also have found high birth defect rates in the area.

While this study is more comprehensive than ones in the past, the study can't say that elevated rates of birth defects are caused by local industries. That's because other risk factors for birth defects, such as diabetes and poverty, can't be ruled out, said Peter Langlois, a senior epidemiologist for the birth defects epidemiology and surveillance branch of the Department of State Health Services.

Instead, Langlois identified 63 elevated birth defects for a federal agency to explore whether potential links exist between these and local industry. While some of the elevated birth defects have been scientifically tied to chemicals released by chemical plants and refineries — solvents such as benzene are known to cause spina bifida, a birth defect in which the spinal cord, or its coverings, do not completely develop — these birth defects also are elevated among babies born to mothers who are poor, minorities, or have diabetes or other health complications.

Officials with the federal Agency for Toxic Substances and Disease Registry could not immediately be reached for comment Thursday.

At the request of the area residents concerned about their health, the federal agency has been conducting a public health assessment about industry's potential effect on the health of residents living in Refinery Row, or the fence-line neighborhoods of Dona Park and Hilcrest near the petroleum refineries.

The agency announced in January that it had found no evidence of widespread exposure to cancer-causing benzene and other volatile organic compounds in the air, or in blood and urine samples collected from refinery row residents.

Environmental activist Suzie Canales, who has criticized the federal blood, urine and air study for being too narrow, said she wants a more extensive study on the heels of Langlois' December study. While the study stops short of determining a cause, it's clear that Corpus Christi has a problem with birth defects, she said.

"This should be a wake-up call for all of us," Canales said.

She said she wants researchers to interview families and draw cord blood from a sample set of babies across the region to more accurately gauge a possible connection between birth defects and environmental factors.

Canales has requested support from elected officials, including state Sen. Juan "Chuy" Hinojosa, D-McAllen.

His staff said they have received a copy of the study but have not yet moved forward with it.

"It's in the beginning stages right now," said media relations coordinator Daniela Santoni.

Langlois looked at nine years' worth of data and found that birth defects were 74 percent higher in the three-county region of Nueces, San Patricio and Kleberg counties than in the rest of the state. He also compared the Corpus Christi region against other counties in the Children's Outreach Heart Program, where children are regularly screened for cardiovascular birth defects and found birth defects to be 75 percent higher.

Severe birth defects, or cases in which the baby died or required surgery, were 39 percent higher in the area than statewide, Langlois found.

He said that, while he was able to control from some risk factors, he was unable to accurately determine other risk factors that could influence results, such as mothers' income levels or how many had diabetes, which is commonly underreported on birth certificates, he said.