By Cat Holmes
University of
Georgia

Two University of Georgia scientists have been awarded
$4.1
million in grants to conduct research and create
mathematical
models that help predict the risks of chemicals in the
environment. With the models, scientists could avoid having
to
test thousands of combinations and doses on humans.

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.<