By Cat Holmes
University of Georgia
People are growing more concerned over the effects on people of chemicals in the environment, said Jeff Fisher, head of the environmental health sciences department in the UGA College of Agricultural and Environmental Sciences.
This has created a climate ripe for the use of pharmacokinetic modeling, which can predict the ways human bodies interact with chemicals, he said.
"Pharmacokinetic models predict things. But there must be real laboratory data to see if the simulations are correct," said James Bruckner, a toxicologist in the UGA College of Pharmacy. "I do experiments with animals. That data and human data are used to construct the models."
Fisher said federal agencies have begun to use pharmacokinetic models to address issues they don't have data on and to extrapolate to low doses for "what-if" exposure scenarios.
"Eventually," he said, "such models could be used in risk-assessment policy and to set federal exposure standards."
Some of the pharmacokinetic models Fisher and Bruckner create will address certain chemicals' effects on children. Testing children's chemical sensitivity poses serious problems.
"How can you give a potentially toxic or carcinogenic substance to a child for whom there is no benefit in order to conduct research?" Bruckner said. "Pharmacokinetic modeling is an obvious answer."
A $750,000 EPA grant will allow the two scientists to examine the pharmacokinetics of pyrethroids, a commonly used pesticide, on the human body as it matures.
Another grant allows them to study the metabolism of two common solvents, trichloroethylene and methylene chloride, from birth to maturity. It's funded by the Agency for Toxic Substances and Disease Registry (ATSDR) of the Centers for Disease Control at $25,000 a year.
"We're investigating whether the risk is greater when the chemicals are found together," Fisher said.
Trichloroethylene figures largely in two other grants totaling $1.8 million. These were awarded as part of a larger research effort through the Medical University of South Carolina on behalf of the Department of Energy.
A number of studies have tested whether trichloroethylene can cause cancer. But the doses given the research animals were very high, Fisher said. He and Bruckner hope to find out whether low-level exposures cause cancer.
A lot of money is riding on the answer.
"It's a matter of whether you want to spend $100 million to clean up each site," Bruckner said. "I was just out in California, where they're spending $20 million a year now to pump water with a really low level of trichloroethylene into the San Francisco Bay, and there's a water shortage. The question is, 'Is it necessary?'"
With another ATSDR grant, for $500,000, Fisher and Bruckner will study how perchlorate, a common groundwater contaminant, and PCBs interact on the thyroid gland.
Perchlorate, a solid rocket oxidizer also used in air bags, bazookas and fireworks, is known to inhibit the thyroid's uptake of iodine. There is also some fear, Bruckner said, that it might cause thyroid cancer.
Finally, the scientists got a three-year, $750,000 U.S. Air Force grant to test a relatively new, widely used jet fuel called JP-8. For a few years now, there have been complaints of dermatitis, dizziness and shortness of breath from people exposed to the fuel.
"It's a huge mixture made of hundreds of hydrocarbons," Fisher said. "There hasn't been a lot of toxicology work done on these bigger molecules. Animal studies show inhibition of immune function, lung injury and contact dermatitis."
A pharmacokinetic model, he said, could provide a way to understand the occupational and community health risks.<
(Cat Holmes was a science writer with the University of Georgia College of Agricultural and Environmental Sciences.)