By CHERYL HOGUE
We don't have a lot of information about many of the industrial chemicals that are in our air, water and soil, or those that are increasingly found in our blood.
This dearth of data often leaves audiences hanging when journalists report about pollution and biomonitoring. Too often, scientists just can't tell us what the presence of Chemical X in our bodies means.
This information is scarce in part because testing chemicals to see if they cause toxic effects — like cancer or birth defects — takes a long time and is expensive. For instance, an experiment to determine whether a substance can cause cancer in laboratory rodents costsbetween $2 million and $3 million and takes about two years to complete. The U.S. National Toxicology Program (NTP), a world leader intesting chemicals, has done studies on only about 2,500 substances over the past 30 years.
But the situation is starting to change. In February, two U.S. government research agencies agreed to collaborate on new testing methods that could revolutionize the field of toxicology. These new techniques are expected to help scientists learnwhy some chemicalsmake people sick.
Thecollaboration,betweentheNationalInstitutesofHealth(NIH)and theEnvironmentalProtectionAgency,shouldproduceheapsofinformation about tens of thousands of industrial chemicals.This, in turn, could lead to the regulation of more chemicals, invention of safer substitutes, and, ultimately, healthier people living in a healthier environment. It will also provide loads of newdata for environmental journalists to use in informing the public.
The federal effort is fundamentally changing how chemicals are tested for toxic effects. The new methods rely on human cells cultured in laboratory dishes and computer technology to rapidly assess what causes toxicity in those cells. The buzzword "highthroughput" is used to describe these new techniques. It means doing lots and lots of small-scale tests really fast.
This marks a big shift from past practice. For decades, toxicologists have studied the effects of chemicals by feeding or injecting laboratory animals – mainly rats and mice – with a range of doses of a substance.
Researchers look for effects in the animals, such as weight loss or a shorter life than their peers who didn't get exposed to the chemical (the "control" animals) or those in the experiment that got a smaller dose. At the end of study, researchers examine the animals' internal organs for possible problems. In some toxicology tests, rats or mice are given the chemicals and their offspring are studied for harmful effects.
These traditional toxicology studies on animals, sometimes called in vivo techniques, take years to complete and are extremely expensive. Animal welfare proponents find these studies abhorrent and lobby hard to stop them.
The new methods – called in vitro techniques – hold promise for screeningtensof thousandsofchemicals forpotentiallytoxiceffectsand for reducing the need to use animal testing. These procedures allow scientists to determine how genes, proteins and biological pathways are influenced, for good or for bad, by exposure to chemicals. This helps researchers to pinpoint the key steps in the development of diseases such as cancer.
The collaboration is designed to validate the new methods for toxicity testing. It will begin by focusing on chemicals that already tested through traditional means. NTP, located at the National Institute of Environmental Health Sciences in Research Triangle Park, N.C., and EPA are contributing traditional toxicity data on 2,800 chemicals to the project. The compounds include industrial chemicals and ingredients in pesticides, cosmetics, plastics and herbal supplements. Government researchers will use the new techniques to figure out why these substances are toxic. The effort will fine-tune the computerized tests and demonstrate that they are as good as, or perhaps better than, experimenting on rats and mice.
The National Human Genome Research Institute, part of NIH in Bethesda,Md., has the equipment to run the "high-throughput" tests. Until now, this NIH program has focused on testing compounds that could prevent development of diseases like diabetes or breast cancer. In the new program, the research institute will do the opposite by studying exactly how toxic chemicals disturb biochemical pathways and cause disease.
EPA expects to release the first comparisons of traditional toxicity tests and results from the new procedures to the public later this year.
Cheryl Hogue reports from Washington, D.C., for Chemical & Engineering News.
** From SEJ's quarterly newsletter SEJournal, Spring 2008 issue