Science of toxicology coming of age

March 06, 1995|By Douglas Birch | Douglas Birch,Sun Staff Writer

It's a risky world out there, what with ozone in our air, chlorine in our water, asbestos in our schools and naturally occurring radon gas in our homes. And nobody knows that better than about 4,000 scientists in Baltimore this week for a meeting of the Society of Toxicology.

The researchers study those hazards and help test the safety of new drugs, food additives and cosmetics.

Government regulators use their studies to decide which chemicals to approve and which to curb or ban -- decisions that can save lives or, if the threat is grossly overestimated, waste billions of dollars.

"Toxicology is clearly coming of age in terms of a science that's having an important impact on society," said Dr. Roger O. McClellan, a former president of the society, which is meeting at the Baltimore Convention Center.

But it still can be a frustratingly inexact science. Several years ago, studies suggested that putting chlorine in drinking water could cause cancer.

Scientists estimated people who shower daily have a one-in-10,000 chance of contracting a fatal cancer from exposure to chloroform, a chemical produced when chlorine mixes with tap water and air.

The estimates were based on pumping doses of chloroform into the stomachs of rats and mice over about two years, Dr. McClellan said.

Scientists assumed that cancers were triggered when the chloroform damaged the rodent's genes, causing the affected cells to divide and grow uncontrollably, the way most cancer-causing agents are thought to work.

But a new study suggests that chloroform does not cause changes in genes, Dr. McClellan said.

It destroyed massive numbers of the rodent's liver cells, causing the production of new cells to replace them.

The more cells produced, the higher the likelihood that one of them would contain a genetic error leading to cancer, he said.

Substances that cause cancer at high doses in laboratory animals are assumed to produce cancer at low doses in at least some humans.

At this week's meeting, toxicologists also will discuss the links between airborne grit and disease and the effects of the industrial pollutant dioxin on human health, among other things.

Yesterday's opening session was picketed by about 20 members of PETA, People for the Ethical Treatment of Animals, the Rockville-based animal rights group.

PETA activists criticized the toxicologists as "mad scientists," saying animal tests are cruel, outdated and ineffective.

Several scientists were just as critical of the protesters.

Animal tests are crucial to help screen new drugs, said Patricia Frank, a Midwestern-based consultant to the pharmaceutical industry.

"Can you imagine if we took a drug that we thought was going to work and just pumped it into people?" she asked. "They'd be dropping like flies."

At yesterday's meeting, scientists discussed alternatives to animal testing, including using computer models that mimic human biology.

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