THE POLLUTION INSIDE US
Toxicologists examine the chemicals of modern life.
By: Peg Herring, Oregon’s Agricultural Progress

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.

Man-made and naturally occurring chemicals pervade modern life. Here are a few that have been linked to human health problems.

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.

Man-made and naturally occurring chemicals pervade modern life. Here are a few that have been linked to human health problems.

“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.”

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.

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.

Robert Tanguay, an OSU molecular toxicologist, has pioneered the use of zebrafish in toxicology. He uses what is called “high-throughput” screening—the rapid testing of lots of samples—to fill the gaps in existing toxicity data. He 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.”

Read the full article at Oregon’s Agricultural Progress

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