The Pollution Inside Us
Forty years ago, chemical pollution was the stuff that spewed from tailpipes, smokestacks, and sewers. Rivers burned, fish died, and forests withered under acid rain until Congress passed strict laws to curb the flood of manmade chemicals pouring into our waterways and atmosphere.
However, 40 years ago there was little consideration of the chemicals that we were pouring into our bodies. The chemicals we use to sanitize our hands, package our foods, and keep our beds from going up in flames have seeped into our bodies in ways that were unimaginable a generation ago. Today, we are marinating in antibacterials, hormone disruptors, and flame retardants.
“There are more than 80,000 man-made chemicals in existence today, and an estimated 2,000 new chemicals are introduced each year,” said Craig Marcus, a toxicologist at Oregon State University. “We encounter thousands of them every day, in food, kitchenware, furniture, household cleaners, and personal care products. And very few of them have been adequately tested for safety.”
It’s likely that you are harboring chemicals that were banned long ago, chemicals such as DDT that you received from your mother before you were born. It’s worth remembering that DDT was introduced as a solution to a different problem: ridding the environment of disease-carrying mosquitoes. Chemicals are introduced to solve problems; as it turns out, some can cause problems.
Marcus heads OSU’s Department of Environmental and Molecular Toxicology, where a team of scientists helps determine the risk chemicals pose to human health, as compounds mix in the environment and end up in our bodies.
These chemicals define modern life. They keep pans from sticking and armpits from stinking. We are literally doused with them. U.S. law requires testing such chemicals only if existing evidence suggests potential harm. Therefore, relatively few of the chemicals in use in the U.S. have been tested for toxicity, Marcus said. And even those tests don’t reveal much about how chemicals are released into the environment, how they are absorbed by humans, and especially what effect they have in combination. “That’s what we do here at OSU,” Marcus said. “Our research is highly collaborative and crosses many disciplines, so we are able to detect chemicals in real-world settings and test their toxicity. We work to make people’s lives better and safer by understanding the risks posed by chemical mixtures we encounter in everyday life.”
[caption caption="By using zebrafish, OSU toxicologist Robyn Tanguay can pinpoint the effect of particular chemicals at particular stages of development. Tanguay directs the Sinnhuber Aquatic Research Lab, where rapid testing of thousands of fish can quickly reveal evidence of toxicity. (Photo by Stephen Ward.)"][/caption]
Chemicals are not easy to see. Many have no noticeable smell or taste. Some transform into new compounds when exposed to elements in the environment. OSU toxicologist Kim Anderson has designed ingenious ways to detect trace amounts of chemicals in air and water and to assess their ability to enter living cells. Recently, her research team has designed a simple, wearable sensor that sniffs out chemicals surrounding you as you move through your day. Her wristband sensors look like the brightly colored silicone bracelets that support popular causes. In this case, the cause is your personal health.
As you move through your day, the wristband absorbs chemicals passively from the air around you—no need to extract blood samples or lug around heavy equipment. Its porous surface mimics a living cell, absorbing chemicals from the environment.
Back in the lab, Anderson’s team can extract compounds from the wristbands and screen them for as many as 1,200 chemicals, including flame-retardants, pesticides, nicotine, and a host of carcinogens on the Environmental Protection Agency’s priority list of hazardous substances.
Not surprisingly, the wristbands have many practical applications. Researchers are using them with preschool-age children and with roofers working with hot asphalt, to detect exposure to harmful substances. Lately, Anderson’s team has been working in Ohio with larger-scale environmental monitors to measure the impact hydraulic fracturing might have on the area’s air quality. Similar to the wristband samplers, the monitors contain material that passively absorbs chemicals in the air. Anderson has used these passive samplers with farmers in Africa and in the Gulf of Mexico where the effects of the 2010 oil spill continue to percolate through the environment.
Among the hundreds of compounds of concern, the OSU team is particularly interested in polycyclic aromatic hydrocarbons (PAH), potential carcinogens that result from many types of combustion, from wood stoves to automobile engines to coal-fired power plants.
PAHs are the focus of OSU’s Superfund Research Project, a 5-year, $15.4 million grant from the National Institute of Environmental Health Sciences. PAHs are found at many Superfund sites and in urban and rural settings around the world. The OSU researchers have discovered that PAHs can transform into new, potentially more toxic compounds when exposed over time to sunlight and air. Anderson’s team was the first to discover that relatively unknown oxygenated PAHs were in the Portland Harbor at similar concentrations to the parent material PAHs.
[caption caption="Staci Simonich, an OSU environmental chemist, has worked extensively in Beijing and elsewhere, studying the impact of air pollution on human health. Here she is training Chinese graduate student Wentao Wang to analyze air samples containing PAH, a common pollutant in smoky or industrialized areas. (Photo by Tiffany Woods.)"][/caption]
Staci Simonich has also been on the trail of shape-shifting PAHs. Simonich, an OSU analytical environmental chemist, has found both oxygenated and nitrated PAHs in air samples she’s collected from Native American smokehouses, the summit of Mount Bachelor, and the city of Beijing. Recently, she predicted the formation of high molecular-weight, nitrated PAH compounds that are even more toxic than the parent PAHs. The mutagenicity of some of these nitrated PAHs, such as those that might be produced by grilling meat, can be 400 times higher than the parent PAH compound. Mutagens are chemicals that can cause DNA damage in cells, which in turn can cause cancer.
Clearly, chemicals in combination may be more than the sum of their parts. So, testing the toxicity of chemical mixtures can be tricky. It requires a rapid process that can test a multitude of chemical exposures and produce results that are meaningful to human health. Enter zebrafish. These tiny aquarium fish can grow from a translucent egg to a recognizable fish in just five days, and they can quickly reveal how some chemicals affect biological processes at various stages of development. Zebrafish are central to the effort to assess thousands of commercially produced chemicals for a wide number of health effects.
Robyn Tanguay, an OSU molecular toxicologist, has pioneered the use of zebrafish in toxicology. She uses what is called “high-throughput” screening—the rapid testing of lots of samples—to fill the gaps in existing toxicity data. She is part of one of the largest toxicology studies ever conducted on living organisms, screening 1,060 different compounds for 22 possible effects, using zebrafish.
“During early development, people and fish are more similar than at any other time in life,” said Tanguay. “Instead of testing individual cells in a dish, we can test the whole animal during its most critical time of development and follow it through its life.”
Within days of a chemical exposure, developing zebrafish can reveal physical abnormalities. Exposure to certain dioxins, for example, might show up as deformed vertebrae and skulls. Within a few months, fully mature zebrafish can be tested for behavioral responses to reveal how the brain, nervous system, and muscles might be affected by certain chemicals. Patterns that suggest a tendency toward diabetes or schizophrenia can be identified rapidly and repeatedly, directing further in-depth research. In this way, the zebrafish model reveals a chemical response from the whole organism, across the whole lifespan, at a population scale, almost in the wink of an eye.
“This is not incremental science,” Tanguay said. “I prefer to ask bigger, crazier questions and take the leap toward solving larger problems more quickly.”
The safety of man-made chemicals is certainly a very large problem. “Safety is not a concept we can easily define,” said Jeff Jenkins, an environmental chemist at OSU. “So we talk about risk.” His work communicates risk by evaluating exposure to chemicals used as pesticides. There are many kinds of pesticides and their potential for adverse effects on people and animals varies greatly depending on individual susceptibility and exposures. “Rivers flow, wind blows, exposures shift, and chemicals themselves redistribute and transform, creating an ever-shifting chemical environment,” Jenkins said. “Environmental chemists work with toxicologists to sort out all these variables to assess which exposures pose significant risk.”
[caption caption="A simple wristband passively absorbs environmental toxins encountered in everyday life. Developed by OSU toxicologist Kim Anderson, these wristbands provide a personalized account of the chemical mix in which we each live. (Photo by Stephen Ward.)"][/caption]
The ancient alchemists knew that dose makes the poison. “Toxicity increases with dose, and dose is related to exposure,” Jenkins said, “so we have to know what we’re being exposed to; and where, when, and how it’s changing in the environment.”
He looks around his OSU office, piled high with research papers and journal articles. He swipes a finger across the surface of a bookcase, and retrieves a small touch of dust. Chemical residues in the dust come from plastic-topped tables, upholstered chairs, even inkcovered paper. “There are likely to be hundreds of different chemicals in this tiny bit of dust,” he says, “however exposure is low and I believe the risk is likely to be trivial.”
Fluorochemicals probably make up some of the dust on Jenkins’s bookcase. They are used in stain-resistant upholstery, heat-resistant electronics, even dental floss. Fluorochemical bonds are the strongest bonds in nature; they resist breaking down in the environment, so they make durable products. But fluorochemical bonds don’t occur in nature; they are manufactured, and they have been made in large quantities since the 1950s.
Jennifer Field, an OSU analytic chemist, studies fluorochemicals and the pathways they take in the environment. “These chemical families have a long residence time in soil and groundwater, in landfills, and in water treatment plants,” she said. “They are bioaccumulating— in deep ocean organisms and in human blood—and they’re linked with health problems, including kidney, prostate, ovarian, and testicular cancer.”
One reason potentially toxic chemicals have become ubiquitous in modern life is that there were few tests in the 1950s that could detect effects on the molecular scale. Tested with the tools of the time, the chemicals seemed safe enough. Field has developed new analytical tools that provide deeper insight into fluorochemicals. “We provide these tools to the public, so they can be used to make decisions that will reduce risk,” Field said. She recognizes the value of having an interdisciplinary team to develop more powerful tools. “Because few chemicals exist in isolation, they can’t be studied in isolation. It takes a team of environmental chemists and toxicologists looking at the full spectrum to put the whole picture together,” she said.
At the far end of that spectrum are tiny, engineered nanoparticles. Stacey Harper investigates specific nanomaterial properties that might lead to unwanted health effects. “Nanomaterials are extremely diverse,” said Harper, who works at the crossroads of toxicology and engineering. She is on the frontier of developing methods to test the toxicity of some of the newest—and smallest—man-made materials. “Nanomaterials are dynamic, she said. “If you put them in a liquid, for example, they can agglomerate to form larger particles with very different features and behavior. Even the smallest variable—say, the precise way a technician uses the pipette—can affect the results of toxicity tests.”
The global nanomaterial industry is growing rapidly. The industry in the U.S. alone is predicted to surpass $6 billion by 2016, as new materials find applications in medicine, manufacturing, and personal care products. In order to understand the behavior of these new particles and assess their effect on living cells, Harper wants to know if toxicity is related to material properties such as size, shape, and surface characteristics.
Because she needs to test lots of repetitions in a very short time, Harper’s research combines the chemical measures of nanoparticles and the rapid toxicity testing using zebrafish. Her goal is to develop predictive models for classes of nanomaterials based on reliable, repeatable tests. “These tests make it possible to learn quickly what structural characteristics are likely to do harm, so they can be avoided in the design of safer nanoparticles and applications,” she said.
Assessing the toxicity of man-made materials, from super-strong carbon nanotubes to breathable waterproof raingear, is complicated. From discovery to analysis, OSU chemists and toxicologists are developing new tools to help people make better choices in the materials that form the basis of modern life. “No single researcher can do this; it requires collaborative, cross-disciplinary research,” said Harper. “It takes a community, and that’s the strength of OSU.”