Exposure Science

Chemicals surround us: in the air, the water, our food, our clothes and our furniture. Which ones are dangerous? How much of them is dangerous? Watch as EPA scientists in Research Triangle Park use chemical toxicology tests to answer these questions.

RESEARCH TRIANGLE PARK — You can find a little bit of nature—a little bit of green heaven—during a spring walk in McCorkle Place. It’s one of the open, tree lined squares in the middle of the University of North Carolina Chapel Hill's campus. Flowers are blooming, trees are budding and the sun is shining as you walk along the brick sidewalks.     

But I’m not just here to take in the natural scenery. If you look around the the square, it only takes a second to find people interacting with all sorts of chemicals, in the midst of all that nature. Let's observe. 

There’s someone eating their lunch from a Styrofoam container as they walk through the area. There are plenty of people drinking from plastic water bottles. More than a few folks are sipping from coffee cups and soft drink cups. And I can’t forget to mention the countless cell phones and ear buds being used all around.

Chemicals, in plastics, clothes and other materials, are all around.   

“The fact is we’re exposed to chemicals on a daily basis,” says Rusty Thomas, who directs the division of the Environmental Protection Agency that tests the safety of chemicals found in the items we use everyday. “Chemicals are in the air we breathe, the water we drink, even the products we use daily in the home. But I think what not everybody appreciates is the potential health risk of many of those chemicals isn’t fully understood.” 

The labs of the National Center for Computational Toxicology, and the researchers tasked with testing many of the chemicals all around us, are here in Research Triangle Park. 

Federal law gives the EPA the authority to test, regulate and maintain an inventory of all of the chemicals used in commerce. The agency’s inventory lists about 75,000 chemicals. But there are different levels of scrutiny, depending on how the chemical is used. The computational toxicology division has testing information on about 8,000 chemicals in its library. 

“We’re tending to focus more on understanding the toxicity of single chemicals,” adds Thomas. “But we do have some research efforts on how they interact as well as mixtures, and how the combined effects of chemicals in that mixture may be of concern to the agency.”

The agency is using robotics and computational modeling to look at the link between the source of chemicals in the environment and negative outcomes. They are also studying the health risks a chemical poses. The new techniques allow researchers to assess the risks of large numbers of chemicals at one time and pinpoint those needing further review, rather than examining individual chemicals one at a time.

Steve Simmons, a research toxicologist at the EPA lab, is inserting a small tray with tiny compartments on it, into a large machine called a High-Throughput screener. The compartments hold small amounts of human cells in a growth medium. The machine injects trace amounts of a chemical to be tested onto the cells.

“We call this a concentration response test,” explains Simmons. “It allows us to see how the biological response changes with increasing or decreasing concentrations of the chemical. And what we are specifically looking for is how little of the chemical is needed to produce a measurable response.”

Weighing the potential toxicity of a chemical, testing human cell exposure and the process through which a chemical becomes harmful determines the possible health risk. 

“We determine what dose we need to be concerned about and then we compare the dose that may disrupt your hormones to the predicted exposure in the environment,” adds Thomas. “The difference between the two is how much we should be concerned.”

John Wambaugh, a research scientist with the EPA, gives this example.

“I’m wearing a t-shirt that is 100 percent cotton, but those are the fibers in the shirt that are all cotton,” says Wambaugh, as he pulls the corner of his t-shirt out from under the dress shirt he’s wearing. “But those fibers are treated with chemicals that keep it from catching on fire and I appreciate that. But as I’m wearing the shirt those chemicals are now all over my skin. We’ve tested chemicals like that.”

So let’s take one more stroll through McCorkle Place.

The chemicals used in the lawn care products, which people are walking on, are regulated differently than the chemicals in the shampoo people might have used in the morning. In addition, the chemicals in the food people are eating are closely monitored. But the chemicals we come in contact with every day, such as those in water bottles and clothing, do not get the same level of scrutiny. Manufacturers must submit a 90-day pre-manufacturing notice. It’s up to the EPA to determine if there is a problem.   

“And that’s why our work is so important,” says Thomas. “Most of the chemicals we study are not dangerous, but you have to check. If you find there’s a really low level of exposure, and it takes a lot to disrupt the hormone system, then you have little risk. But if you are exposed to a lot of the chemical, and it doesn’t take much to affect hormone system, then you are at great risk and we need to take action.”

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