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(Last updated 3/3/05)



COLUMBUS, Ohio – Scientists at Ohio State University and Battelle are developing a comprehensive statistical model of how potentially harmful metals in the environment find their way into the human body.

The project is part of a new joint effort by the Environmental Protection Agency (EPA) and the American Chemistry Council (ACC) to fund research that helps gauge people’s exposure to chemicals in everyday life.

Their model could go a long way toward helping officials make better assessments of public health risk, especially in cases where information is limited.

The ACC is providing $450,000 for the three-year project; the university and Battelle are together adding an additional $345,000 in internal funds.

“This research not only makes use of the special talents represented in the College of Mathematical and Physical Sciences, it is the first major joint effort between our College and researchers at Battelle,” said Richard Freeman, dean and distinguished professor of mathematical and physical sciences at Ohio State. “We are very pleased to be a part of this important collaborative effort.”

Chiefly, the model will draw connections from different sets of data collected in the 1990s during environmental health studies in Ohio and other Great Lakes states, as well as in Arizona. The primary study was part of the EPA’s National Human Exposure Assessment Survey (NHEXAS), which studied more than 500 volunteers and measured the presence of toxic substances, including four metals -- arsenic, lead, cadmium, and chromium -- in the volunteers’ bodies and the environment.

The model will build a picture of how the metals entered the environment and how people came into contact with them. Environmental agencies can then use the model to determine where intervention is most likely to be of benefit.

Today, doctors can test for chemicals called biomarkers in body fluids and tissues to discover who has been exposed to a toxic substance. But biomarkers don’t necessarily give clues as to how a substance was transported –- through food, water, air, or even skin contact –- or clues to the original source of the substance in the environment.

It’s a long road from source to biomarker, explained Noel Cressie, professor of statistics and director of the Program in Spatial Statistics and Environmental Sciences at Ohio State.

And while scientists know more than ever about the individual steps along the way -- the geology, chemistry, and biology involved -- nobody has ever connected all the steps together with a single statistical model for most of these metals.

Cressie leads the project team, which includes Ohio State colleagues Catherine Calder, Peter Craigmile, and Tom Santner, and students Jim Zhang and Crystal Dong; and Battelle scientists Nancy McMillan, Bruce Buxton, Michele Morara, and Greg Young.

Their model could go a long way toward helping officials make better assessments of public health risk, especially in cases where information is limited.

Where information is missing from NHEXAS and other data sources, the scientists will use a statistical technique called Bayesian analysis to make educated guesses to fill in the gaps.

“We can make inferences where we have no direct measurements at all,” Cressie said.

For instance, if the data doesn’t include a direct measure of how arsenic spreads through the air, the scientists could draw on knowledge from outside experts on airborne arsenic. Then they will use software that was recently developed at Battelle to test different aspects of the model.

The new software is particularly efficient at running the complex computer simulations required for a Bayesian analysis, McMillan explained. The scientists will be able to program their simulations quickly, and get results in hours instead of days.

“At the end of the day, we’ll be able to ask ‘what if’ questions,” she said. “If we change the sources, what happens to the biomarkers?”

That’s just the kind of question that the EPA wants to answer when it’s evaluating public health risks or setting new emissions standards. And the ACC, an association of chemical companies, can also use that information to address public health policy issues and identify research priorities.

Once the model is complete, the scientists will be able to draw statistical connections between different kinds of exposure.

For example, if a certain number of people in a town have both lead and arsenic biomarkers measured in their blood, and later one of the townsfolk is found to have biomarkers for lead, the model can calculate the likelihood that he has also been exposed to arsenic.

“And along the way we could get some new ideas on how arsenic exposure happens,” McMillan added.

McMillan, who earned her doctoral degree in statistics at Ohio State, said that she and her Battelle colleagues had already been working with Cressie’s group before the EPA and ACC announced the new funding opportunity in 2003.

Just as Ohio State and Battelle signed a Memorandum of Understanding (MOU) in November 2004 to formalize their frequent research collaboration, the EPA and ACC recently signed an MOU of their own, to “engage the best scientists in the research community to promote improvements in the quantity and quality of data for use in human health and ecological risk assessment.”

The Ohio State/Battelle project is among the first funded through this new collaboration. The funding comes from the ACC’s Long-Range Research Initiative (LRI).

The ACC will fund one other project, at Harvard University. The EPA will fund three projects through its Science to Achieve Results Program.

“Both EPA and ACC are intent on improving the scientific foundation for evaluating human exposure data,” said Tina Bahadori, a senior scientist with ACC’s LRI. “The research projects will build on existing human exposure databases by taking high-quality data to the next step of interpretation, thereby advancing the field of exposure science.”


Contact: Noel Cressie, (614) 292-5194; cressie.1@osu.edu
Nancy McMillan, (614) 424-4611; mcmillann@battelle.org

Written by Pam Frost Gorder, (614) 292-9475; Gorder.1@osu.edu