Weird place on Earth Mono Lake in eastern California is where researchers found a type of bacteria that appears to break the rules for how we think life should survive. Credit: NASA image gallery

You may not know phosphorus when you see it, but your body does. Phosphorus is a sturdy workhorse element. In DNA molecules, phosphorus helps support the whole double helix. Within cells, energy shows up as ATP — and the “P” stands for phosphorus (specifically, phosphate, a form of phosphorus).

All life as we know it, in other words, depends on phosphorus. For that reason, scientists around the world were shocked December 2 when a team of scientists announced finding life forms that didn’t necessarily depend on this all-important element. In laboratory tests, the scientists grew bacteria that were able to use arsenic — a different element with similar chemistry — in the place of phosphorus.

It’s a surprising discovery because living organisms have never been found without all six of the ingredients crucial to life: carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur (all together known as CHNOPS). Arsenic, though, is a potentially fatal poison.

Many scientists say they would like to see more evidence that the research team did in fact observe life forms using arsenic instead of phosphorus.

“This is an amazing result, a striking, very important and astonishing result — if true,” Alan Schwartz told Science News. Schwartz researches chemistry at Radboud University Nijmegen in the Netherlands. “I’m even more skeptical than usual, because of the implications. But it is fascinating work.”

The bacteria came from Mono Lake, a lake in eastern California that is well known for its unusual population of living organisms, including shrimp and algae. The lake doesn’t drain, so the only way for water to leave is through evaporation. As a result, the lake is much saltier than the ocean.

An up-close picture of the bacteria GFAJ-1 grown on arsenic. Credit: Jodi Switzer Blum, NASA

Several researchers had been studying a number of tiny organisms that lived in Mono Lake mud. Astrobiologists study life in the universe and want to know how it started, how it has changed, and what will happen to life in the future. They also want to know whether life exists on other planets and if so, what it might look like. Many astrobiologists study what lives in Earth’s strangest places, such as Mono Lake, as a way to understand the possibilities for life.

The study was led by Felisa Wolfe-Simon of NASA’s Astrobiology Institute and the U.S. Geological Survey in Menlo Park, Calif. She and her team removed organisms from the Mono samples and grew those bacteria in the lab. The scientists fed the microbes with sugar and vitamins — but left out phosphate. Then they changed the diet again, and gave the microbes arsenate, which is a form of arsenic.

In one type of bacteria, called GFAJ-1, the researchers observed that arsenic wasn’t fatal. The bacteria continued to grow, though not as fast as if they’d had phosphorus. After studying these bacteria, Wolfe-Simon and her team concluded that the organisms had begun to make use of the arsenic the way they usually used phosphorus. The researchers suggest that arsenic was being used as a building block in the bacteria’s DNA.

“This microbe, if we are correct, has solved the challenge of being alive in a different way,” Wolfe-Simon told Science News.

If the scientists are right, then “life as we know it” may not include all the life that actually is possible. For astrobiologists, that conclusion suggests that life on other planets may not necessarily look like life on Earth.

It’s possible that follow-up studies will show that the researchers were mistaken. Wolfe-Simon and her team could not get rid of all the phosphorus when they were growing the bacteria. Some scientists say minute amounts might be enough to keep the microbes alive. It’s possible that, in the experiment, the bacterium GFAJ-1 was still getting small amounts of phosphate.

Can life exist using poison instead of phosphorus? Life of a different type is an exciting prospect, so stay tuned to see how the scientific community reacts. Next up, scientists will want to know how, exactly, the arsenic substitution works.

POWER WORDS

arsenic A highly poisonous metallic element having three allotropic forms, yellow, black and gray, of which the brittle, crystalline gray is the most common. Used in insecticides.

phosphorus A highly reactive, nonmetallic element occurring naturally in phosphates.

DNA A nucleic acid that carries the genetic information in the cell. DNA consists of two long chains of nucleotides twisted into a double helix and joined by hydrogen bonds between the bases.

molecule A group of like or of different atoms held together by chemical forces.

microbe A minute life form; a microorganism, especially a bacterium that causes disease.

bacterium A life form that is a single cell and too small to see without using a microscope. Bacteria (plural of bacterium) live in almost every environment on Earth, including very cold places, very warm places, in all types of water, in the air, even on and in plants and animals. These microorganisms can also cause disease in plants and animals.

Tiny red flecks — rayon fibers — will soon identify the only BPA-free thermal-printed store receipts in North America. Credit: Appleton

Appleton Paper, a company in Wisconsin, makes the kind of paper used for sales receipts. Starting in the first two weeks of November, the company’s receipt paper comes with something new — tiny flakes of red fibers on the back. Next time you come across a receipt, flip it over and see whether you can see red.

If you do, rest easy — because Appleton’s receipts do not contain bisphenol A (BPA), a chemical that has been in the news. Recent studies show BPA could be hazardous to your health. BPA is called a hormone disruptor, which means it enters the body and acts like a hormone, a chemical that can control body processes. When BPA acts like hormones, the body’s real hormones may have trouble doing their job.

Studies have turned up a link between BPA and heart disease, and exposure to the chemical might make a person more likely to develop diseases such as diabetes. In roundworms, which are often used in the laboratory as a model for humans, BPA interferes with reproduction. That could mean bad news for human reproduction, too.

In three separate studies last year, conducted all over the world, researchers discovered BPA in cash register and ATM receipts. Worse yet, further studies showed that the BPA rubs off easily onto a person’s hand. A recent report from the French government says this BPA is quickly absorbed into the skin and then the bloodstream.

“I won’t touch receipts now,” Frederick vom Saal told Science News. He is a scientist at the University of Missouri in Columbia who investigated receipts as part of a study by the nonprofit Environmental Working Group. He is now working on a study that looks not only at how BPA travels from receipt to skin, but also at how much of that BPA later turns up in a person’s urine or blood.

A recent study of pregnant American women found that cashiers, who work with receipts all day, have higher levels of BPA in their blood and urine. Since BPA passes so easily into the body, it may also pass easily into the fetus, which means a mother’s BPA exposure could be hazardous to her children.

Receipts are not the only source of BPA — far from it. BPA is used in the production of plastic. Plastic is everywhere, which means BPA is all around us. The BPA travels from the plastic into the body when the plastic is heated — in a dishwasher or microwave, for example — or when it is scratched.

In addition to water bottles and other containers, plastic shows up in places you wouldn’t expect: bike helmets, telephones, computers. As a quick example, consider a typical automobile: plastic is used in the seats, dashboard, parts of the body and some engine parts.

BPA is in receipts and in plastic, and a recent study turned up BPA in yet another alarming source: food. In a recent study, scientists in Texas tested 31 types of canned foods or foods packaged in plastic. They discovered measurable amounts of BPA in 60 percent of the food products.

The Environmental Protection Agency recommends people consume no more than 50 micrograms of BPA per kilogram (2.2 pounds) of body weight. The food-based BPA measured by the Texas scientists is far below that guideline.

Scientists are still trying to determine both the real risks of BPA, and how much of the chemical is too much. To be on the safe side, check your receipts — and your plastic.

POWER WORDS (from the Yahoo! Kids Dictionary and the National Institutes of Health)

plasticizer Any of various substances added to plastics or other materials to make or keep them soft or pliable.

plastic Any of various organic compounds produced by polymerization, and capable of being molded, extruded, cast into various shapes and films, or drawn into filaments used as textile fibers.

BPA A chemical produced in large quantities for use primarily in the production of plastics.

hormone A substance produced by one tissue that travels through the bloodstream to another tissue to effect physiological activity, such as growth or metabolism.

Diet fads come and go, but in the end, there’s really only one rule for losing weight: Burn more energy than you consume. In April, scientists from California reported on a chemical that might help people burn fat. It’s called dihydrocapsiate, it comes from a pepper, and in a recent study it was shown to boost the body’s energy burn.

Its name, dihydrocapsiate (di-HI-droh-CAP-see-ate), isn’t easy to say. And Peter Piper never picked it. But it might be easy to find: It is a chemical cousin of capsaicin (kap-SAY-sin), the chemical that makes chili peppers so hot. But unlike its fiery family members, dihydrocapsiate won’t send you running for a glass of water if you eat it. In fact, you won’t even know it’s in your body.

Painful foods — like the ones that contain capsaicin — stimulate pain receptors in the mouth. Once stimulated by a fiery food, these pain receptors signal nerves, which send a message to the brain. Dihydrocapsiate, however, is too big to fit into the receptors and tickle those nerve endings, which means it enters and passes through the body without causing pain.

The main compound that gives peppers (pictured are red savina habaneros of New Mexico) their sting has a close cousin that may burn body fat without irritating the mouth or stomach.

NSF; Chile Pepper Institute

David Heber, a scientist at the University of California, Los Angeles reported on the dihydrocapsiate research in April during a meeting of scientists who study nutrition. He and his colleagues tested the chemical on 33 obese men and women. For four weeks, these volunteers consumed only 800 calories per day, and all of those calories came from a nutritious liquid, instead of from solid foods. These liquids did not contain any fat.

At every meal, the participants were also given pills. People in one group received pills that didn’t do anything. Drugs that don’t do anything are called placebos, and they help experimenters figure out whether the drug being tested really works. Other participants were given a small dose of dihydrocapsiate. Finally, other participants were given a high dose of dihydrocapsiate.

All of the pills looked the same, so neither the participants nor the doctors knew who had consumed placebos and who had consumed the pepper chemical.

After the end of the dihydrocapsiate-enhanced (or placebo-“enhanced”) diet, the scientists determined how much fat the participants were burning.

The scientists observed that not everyone burned the same amount of fat. People who were given high doses of dihydrocapsiate were burning more body fat than people who had been given placebos, UCLA’s Heber says. So much more, he says, that the people taking high doses of dihydrocapsiate may have been losing one more pound per month than the people taking placebos. But that’s a guess: The scientists didn’t measure that number, so they don’t know for sure.

Heber and his team think that the pepper chemical works by attaching itself to another type of receptor, this one in a person’s gut. This receptor helps send a message to the brain, which then starts a process that causes a body to burn, burn, burn calories. This process is the same that, when triggered by capsaicin, causes some people to sweat while they eat hot foods. The scientists say that capsaicin could have the same effect as the dihydrocapsiate, but capsaicin causes intense pain to a person’s mouth and gut.

Dihydrocapsiate could help people lose weight, delivering the positive effects of hot peppers without the fiery side effects. In theory, the chemical could be consumed safely and help a 100-pound person burn an extra 160 calories per day.

Of course, it would be very easy to undo these sizzling effects with one slice of cake or a sugary soft drink. A chemical like dihydrocapsiate may help a person burn more than he consumes — but it can’t change a person’s eating habits.

“As I always say,” Heber told Science News, “a supplement doesn’t make up for diet.”

This story and other Science News for Kids features describing research in medicine and biology are supported with funding from The Lasker Foundation. The foundation and its programs are dedicated to the support of biomedical research toward conquering disease, improving human health and extending life.

Going Deeper:

Raloff, Jane. 2010. “Chili pepper holds hot prospects for painfree dieting,” Science News, April 27. Available at http://www.sciencenews.org/view/generic/id/58689/title/Science_%2B_the_Public__Chili_pepper_holds_hot_prospects_for_painfree_dieting

Picked a pepper? Find out how hot it is using the Scoville scale: http://www.chilliworld.com/FactFile/Scoville_Scale.asp

Sohn, Emily. 2006. “Hot pepper, hot spider,” Science News for Kids, November 15. http://sciencenewsforkids.org/articles/20061115/Note2.asp

Sohn, Emily. 2009. “Greener diet,” Science News for Kids, February 25. http://sciencenewsforkids.org/articles/20090225/Note2.asp

The village of Kuujjuaq, in northern Canada, is home to about 2,100 people.

No roads lead to Kuujjuaq. You can only get to this village, high in the Canadian Arctic, by boat or plane. The trees here are stunted and small, but the bears grow big. The 500 kids who live in Kuujjuaq (pronounced KOO-joo-ak) have unusual chores: they help their parents catch fish and hunt caribou to eat. This place might seem far away from the big problems of big cities, like water pollution and air pollution. But even here, people can’t escape those problems. Pretty little Kuujjuaq, with its blue skies and crystal clear waters, also has an invisible pollution problem that rivals any city.

Toxic chemicals have a surprising way of finding their way up here to the Arctic. They are gushed out of factories and cities thousands of miles away, and they travel to the Arctic like birds flying north for the summer. The birds go back home, but the chemicals stay.

Everyone in Kuujjuaq has the chemicals in their bodies. No one knows their full effects, but they may hurt children in a slow and silent way. They could cause babies to get sick a little more often. And they might even cause kids to do worse in school.

No one would have dreamed that people in such a clean and beautiful place could be hurt by pollution from thousands of miles away. Then, in 1989, some scientists made a discovery.

POPs around the world

Eric Dewailly, a doctor at Laval University in Québec, Canada, was studying chemicals called persistent organic pollutants, or POPs. These are chemicals that can hang around for a long time in people’s bodies or in the environment.

Dewailly and his team tested people in the cities of southern Québec (near the border with the United States) to see how much of these chemicals were in their bodies. Dewailly’s team wanted to compare this group with people in the Arctic. They reasoned that people in the Arctic lived far from pollution, and so would probably have lower levels of POPs in their bodies.

So the scientists went up to Nunavik, the remote, northern part of Québec which includes Kuujjuaq and 13 other native Inuit villages. When they tested people in Nunavik they were surprised. People there had five to ten times as much of these chemicals in their bodies as people living in polluted cities. Some of the chemicals came from as far away as Russia!

Scientists now understand why this happens. The POPs include hundreds of different chemicals. Some are used in electronic gadgets like TVs, or in the lights and electrical wiring of buildings. Some are used in paints or for making windows waterproof. Others are sprayed onto crops as pesticides. But POPs have one thing in common: They like to evaporate. Just as a puddle of water dries on a hot summer sidewalk, POPs turn slowly into vapor and drift into the air. Winds can carry them thousands of miles.

POPs travel in the air until they reach a cold place. Have you noticed that on a hot day, a glass of lemonade with ice cubes in it collects little drops of water on the outside? This is because water vapor, which is a gas in the air, “condenses” onto the cold glass and forms those droplets—the opposite of evaporating or drying. The same thing happens with POPs, says Knut Breivik, an environmental chemist at the Norwegian Institute of Air Research in the city of Kjeller.

“Things tend to evaporate in warmer regions and condense when it gets colder,” says Breivik. So when winds carry POPs into the Arctic or Antarctic parts of the world, cold temperatures cause them to condense onto plants or rocks or snow or oceans. And then they stay where they landed and build up over time.

10 million tons

Over the years, more than 10 million tons of POPs have probably floated through the skies to the Arctic. If those chemicals were piled on an area the size of a football field, the pile would rise 700 meters in the air—higher than the tallest building on Earth.

Since the chemicals are spread over the entire Arctic instead of a football field, there’s actually only a small amount in any one place. A swimming pool filled with Arctic Ocean water might contain only a single tiny raindrop of POPs. But these chemicals have a nasty habit of collecting inside animals and people, so even a little bit in the environment can end up causing problems.

POPs tend to stick to the oils and fats in living things, so tiny ocean animals like plankton soak them up, just like a shirt soaks up a drop of spaghetti sauce. Those plankton are eaten by larger animals, which in turn are eaten by even larger animals.

Every time one animal eats another, more POPs enter the larger animal’s body. Animals can’t digest POPs. They take them in the front, but never poop or pee them out the back end. So the POPs collect and collect. The biggest animals, like sea birds, seals, and whales, have the most POPs in their bodies. And these animals are eaten by native Inuit people, who have lived and hunted in Nunavik and other parts of the Arctic for thousands of years.

Two teaspoons

By the time a boy growing up in Kuujjuaq turns five years old, he may have collected one or two little rain drops’ worth of POP chemicals in his body. That doesn’t sound like much—but it’s thousands of times more concentrated than these chemicals are in sea water. In fact, that little boy has as much of these chemicals in his 20-kilogram body as there would be in two and a half million kilograms of sea water—in other words, enough sea water to fill an Olympic swimming pool! Scientists are trying to understand how the chemicals affect kids.

Kids in Kuujjuaq play and joke around.

André Perron/Wikimedia Commons

Dewailly’s team has made many trips back to Nunavik to study the problem of POPs. In 1992 and 2004, they sailed in a ship to all 14 villages along the coast of Nunavik, including Kuujjuaq. The ship stopped at each village, and doctors took blood samples and examined people. They measured POPs in hundreds of newborn babies. Blood samples were taken again when the babies turned one year old. And these babies were studied for years as they grew, to find out how the POPs in their bodies affected them over time.

These studies have shown that POP chemicals affect the health of children in small but worrying ways. For one thing, these chemicals can weaken children’s immune systems, says Pierre Ayotte, a toxicologist who works with Dewailly at Laval University. “Then you’re less able to fight disease,” he says. Babies with the most POPs in their bodies had more ear infections and more infections in their lungs—not minor infections like colds or flu, but serious ones that affect breathing and can sometimes send you to the hospital.

Long division

These chemicals might even affect how well kids do in school. When the babies were 1 year old, the Laval University scientists gave them some tests. They tested how well the babies used their hands. They also tested how well the babies paid attention and learned when they were shown new toys. All of these tests were videotaped, and scientists carefully studied the videos afterward. What they saw surprised them.

Babies with high POPs levels weren’t quite as coordinated with their hands as other babies. They also didn’t pay attention quite as well when they were being shown new toys—they often stared away at other things. And during several hours of tests, these babies became upset and cried more often.

These were small differences. You wouldn’t notice them unless you watched the babies closely. But when the same babies were tested again at the age of 5, the ones with high POPs still did a little worse.

“At later ages you’re still at a disadvantage,” says Gina Muckle, a psychologist on the Laval University team that traveled to Nunavik to test the children. Muckle thinks that even small changes can affect how children do in school as they get older. They could affect how a child responds when taught something hard, like long division—whether they meet the challenge with a positive attitude, or get upset and discouraged. Or they could affect how a child responds to the stress of going to a new school—how well they make new friends, and whether they still do well in class during those awkward times. Little differences, over the years, could add up. “Those effects,” says Muckle, “are likely to be a real disadvantage overall during the life of the person.”

Still trickling

No one was happy to learn that POP chemicals were hurting people in the Arctic. But finding out about the problem gave the Inuit a chance to do something about it. In the 1990s, the United Nations held a meeting, called the Stockholm Convention, to discuss banning many POP chemicals. The Inuit sent people to the United Nations to tell how POPs had affected them. Since 1998, 140 countries have agreed to stop making many POP chemicals. As a result, levels of POPs in the Arctic are falling.

But it will take a long time for the problem to go away. For one thing, buildings around the world still contain many tons of POPs in their paint and wiring. Every day, a little bit of those chemicals turns into vapor and drifts outside. Eventually, it reaches the Arctic.

Researcher Sébastien Roy tests the quality of a lake’s water during the 2004 Nunavik Health Survey.

Isabelle Dubois/NRBHSS

Soil also contains huge amounts of POP chemicals—and the hot blast of a forest fire can send them into the air, just as a hot blow drier causes water to evaporate from your hair. Breivik found that major fires in 2004 and 2006 caused large amounts of POPs to go into the air and reach the Arctic. Many of these chemicals last for 100 years or longer.

Likely suspects

The other problem is that while hundreds of POP chemicals are known, there are probably others that scientists still don’t know about. “There are new compounds that are ending up in remote areas,” says Frank Wania, an environmental chemist at the University of Toronto in Scarborough.

Many POPs contain the element chlorine. But in the last few years, scientists like Wania have been surprised to find that two families of manmade chemicals, which contain the elements fluorine or bromine, have found their way into the Arctic. “We failed to recognize [them] until they were already accumulating in the Arctic,” says Wania—meaning that large amounts of them were turning up in seals, birds and people. By the time the chemicals were discovered and banned, the damage was done.

Scientists want to get ahead of the problem. Wania has surveyed 100,000 industrial chemicals. He was looking for chemicals—you could call them “hoppers,” “fliers” and “swimmers”—which might reach the Arctic. Out of those chemicals, he found 120 likely suspects that he plans to look at more closely.

All of this might seem like a lot of effort. But many scientists think it’s the right thing to do. It comes down to one question, says Muckle—whether we want children to be able to grow and learn to their full potential. “The environmental contaminants are certainly an issue,” she says. “As a society we need to take that into account.”

Going Deeper:

A polymer containing a color-changing molecule called a mechanophore turns red seconds before it snaps. The technology may one day allow damage to materials or structures to be easily spotted.

The color red often means danger — and by paying attention, accidents can be prevented. At railroad crossings, flashing red lights warn cars to stay back. A red light at a traffic intersection tells cars to stop, so they don’t run into other cars. And when a driver steps on the brakes, bright red taillights warn cars behind to slow down.

In the future, the color red also may help prevent danger at construction sites. Thanks to new work by engineers, bridge supports — or other kinds of materials — could one day contain a new kind of material that turns red before a structure collapses or falls apart.

The secret behind the color-changing material is a particular type of molecule. A molecule is a group of atoms held together by chemical bonds. Molecules come in all shapes and sizes, and make up everything you can see, touch or feel.
How a molecule behaves depends on what kinds of atoms it contains, and how they’re held together.

To get a rough picture of one way atoms are held together in a molecule, imagine you and your friends standing in a large circle, holding hands. Each person represents one atom, your clasped hands represent the bonds, and the entire circle represents a molecule.

The molecule being used to turn the material it’s in red is called a mechanophore. When one bond in the mechanophore molecule breaks, the rest of the molecule turns red. (Imagine your circle of friends again, and try to imagine that if two people let go, everyone turns bright red.)

When humans are injured, we bruise and our skin changes color. When a polymer containing a color-changing molecule called a mechanophore is about to break, it also produces a color. The process is similar. An injury breaks blood vessels under the surface

Kemter/iStockphoto

“It’s a really simple detection method,” says Nancy Sottos, one of the scientists who worked on the project. “We’re opening up this one bond, and it changes color.” Sottos works on the science of different kinds of materials at the Beckman Institute for Advanced Science and Technology at the University of Illinois at Urbana-Champaign.

Sottos and her team tested the color-changing molecule in two different kinds of polymers, long chains of similar atoms or molecules linked together. First, the team put the mechanophore into a stretchy, soft polymer — not so unlike a rubber band. When the researchers stretched the material, it turned bright red a few seconds before it snapped into two pieces. When they repeatedly stretched and relaxed the polymer, without breaking it, it started to turn red.

They also tested the molecule in beads of a brittle, glasslike polymer. When the beads were squeezed (but not hard enough to shatter), they turned red.

There is a way to get rid of the red color: light. When the scientists shone a bright light on the mechanophore, the broken bond was fixed — and the red danger sign disappeared. This “self-healing” may be a problem for engineers who want to use the color-changer in big construction projects that will be outside, in sunlight. And if bright light keeps the red hue from appearing, then the mechanophore’s warning system will be useless.

Sottos and her fellow scientists still have a lot of work to do before the color-changing molecules can be used outside the lab. If mechanophores can be used in the real world, she suggests employing them in a new kind of paint or even rollerblade wheels.

Going Deeper:

Scientists and regulators are looking into the safety of two chemicals found in many plastic products — including some kinds of baby bottles. Credit: iStockphoto

Try to count everything you use that’s made of plastic. I dare you.

Done yet? I didn’t think so.

Your list may include toys, yogurt containers and pens. But did you remember to include telephones, bike helmets, spatulas and shower curtains? How about straws, food wrappers, picture frames and the seat covers on your school bus?

Plastic is everywhere because plastic is an extremely useful material. It is cheap, strong and lightweight. What’s more, it can take on nearly any form or shape, from soft and stretchy to hard and glasslike.

Plastic, however, is far from perfect. It may even be bad for us, according to a growing body of research. Studies now suggest that toxic chemicals can get out of some types of plastic, get into our bodies, and cause a variety of health problems, including cancer, birth defects and attention deficit hyperactivity disorder (ADHD).

Fetuses and young children seem to be at greatest risk. And since babies tend to put plastic things (and everything else) in their mouths, many parents are worried.

Two types of chemicals in particular have raised special concern lately. They are called phthalates (pronounced thal’ ātz) and bisphenol (biz fē’ nawl) A, BPA for short. Not all plastic products contain them. But the ones that do are surrounded by controversy. That’s because experts disagree about how dangerous these chemicals are.

If you follow the news in coming months, you’ll notice more and more stories about phthalates and BPA. And as the research builds, it’s up to you to decide how plastic will fit into your life. So, what do you need to know to make smart choices about plastic?

From Bottle to Body

Plastic is a single word, but plastic isn’t just one thing. Think about how different a food wrapper is from a water bottle. What all plastics share in common are plasticizers — special chemicals that allow the material to be molded into nearly any shape or texture. Plasticizers are added to plastic during the manufacturing process.

Phthalates and BPA are two types of plasticizers that work in different ways. Phthalates add softness and squishiness to things like shampoo bottles, raincoats and rubber duckies. These molecules are also used in perfumes and makeup. BPA, on the other hand, gives a hard, clear, almost glasslike feel to products such as baby bottles, blender bowls and reusable, see-through Nalgene-brand water bottles (milky-colored, soft Nalgene bottles don’t contain BPA). BPA also appears in the lining of many food and soda cans, in DVDs and in other unexpected places.

Widespread use of BPA and phthalates worries many scientists because both chemicals belong to a group called hormone disruptors. In the body they act like hormones. Hormones, such as estrogen and testosterone, are two of the body’s important messenger molecules. They can tell cells when to turn on or off the cells’ genetic material. That’s how hormones direct the complicated development of a fetus from just a few cells into an actual baby with arms, legs, ears and organs. They also control growth in all of us. They even control the changes at puberty that get our bodies ready to become adults.

When some other chemical imitates a hormone, though, our actual hormones can’t do what they need to do. That can cause all sorts of problems. In hundreds of experiments, animals exposed to hormone disruptors in the womb went on to develop breast cancer, early puberty, diabetes, obesity, behavioral problems and other health issues.

“What we know is that BPA and phthalates disrupt hormones, and that hormones are necessary for normal human development, brain development and reproductive development,” says David Wallinga, director of the Institute for Agriculture and Food Policy’s Food and Health Program in Minneapolis.

Especially worrisome, Wallinga says, is that just tiny doses of a hormone disruptor can have a big impact. That’s because hormones work at extremely low levels in the body, so it doesn’t take much to get in their way.

Most of us already have tiny amounts of hormone disruptors in our bodies. A recent study by the U. S. Centers for Disease Control and Prevention found traces of BPA in 93 percent of the more than 2,500 people tested in the United States.

How do these chemicals get into us? When plastic is heated in the microwave or dishwasher, chewed on or scratched, the chemicals can seep out of the plastic. Even though we can’t see these molecules, we eat them, drink them and breathe them in.

Scientists and parents are especially worried about young children, who tend to chew on everything, including plastic. BPA is a common ingredient in baby bottles, teething rings, sippy cups, baby-formula cans and other products specifically designed to go into the mouths of little kids. Kids are a cause of concern both because they are likely to be exposed to plastics more than adults and because their bodies are more sensitive to the risky chemicals. Hormones play a particularly important role in the developing bodies of both babies and fetuses.

The Debate Goes On

Despite the growing sense of worry, debates about what to do continue between those concerned about the chemicals, the plastics industry and the government agencies charged with deciding on what’s safe and what’s not. That’s because there’s still no proof that BPA and phthalates are making people sick. So far, most experiments have involved animals and cells growing in test tubes.

Bisphenol A, a chemical linked to health problems, can seep out of hard, clear plastic water bottles, like the one shown above. Metal and glass bottles may be a safer way to store drinking water! Credit: T. Siegfried

In humans, the strongest evidence of harm comes from associations: People who have been exposed unintentionally to BPA and phthalates seem to develop the same types of health problems as animals that are deliberately exposed. In science, though, you need to show that one event directly causes another. It’s not enough to just observe that chemical exposure and diseases happen to the same people: The two might just be a coincidence.

Yet, direct proof in humans may never come, Wallinga says. For ethical reasons, researchers can’t expose pregnant women to risky chemicals, then wait to see what happens.

Scientists have also had trouble repeating some of the studies that make these plasticizers look bad, says Steven Hentges, a chemist from the American Chemistry Council, a plastics-industry group in Arlington, Virginia. The group sponsors a number of websites, which compile news reports and studies showing that plasticizers are safe.

“Consumers would have to eat more than 500 pounds of food and beverages in contact with [BPA-containing plastic] every day of their lives to exceed exposure levels determined to be safe,” reads a fact sheet on one such site, called factsonplastic.org.

But one new study that was reported online in the Sept. 13 Science News, found that in human body fat, BPA suppresses a real hormone that normally protects people from heart attacks and type 2 diabetes. The amount of BPA that it took to do this was the same as what is found in most people’s blood. These values were well below values that the government has declared are safe.

That story also reported on a Spanish study that showed BPA — in amounts typical of what’s already found in people — can alter the body’s production of insulin, a hormone that breaks down sugars. This study was conducted in mice, not people. But its findings suggest BPA might help encourage the body’s development of diabetes, a life-threatening hormonal disease where the body can’t use sugar appropriately.

A story in the Oct. 11 Science News actually links BPA concentrations in people to heart disease, changes in liver function and type 2 diabetes.

After evaluating some data — but not all of these studies — many large governmental agencies have concluded that there still is nothing to worry about. In July, Europe’s food safety organization issued a statement saying that BPA-containing products are fine for everyone, including kids. In August, a draft (not final) report by the U.S. Food and Drug Administration came to similar conclusions.

But several large groups of well-known scientists have expressed concern about hormone disruptors in plastics. And some states and countries are taking action.

New Rules, New Products

Dozens of countries, including the European Union, Japan, Canada and Mexico have already banned phthalates from products made for children younger than 3. California and Washington State have done the same. And a number of other states are considering similar rules.

As for BPA, Canada became the first country to ban the chemical from baby bottles in April. A dozen states are considering it.

Even in places where it is legal to sell baby products that contain these chemicals, many major stores are stocking their shelves with versions that don’t contain them. Toys“R”Us and Wal-Mart are two examples. At the same time, more and more manufacturers are making BPA-free and phthalate-free versions of their products.

If you want to know what’s in the plastics you eat and drink out of, look for the small number that’s usually etched into the bottom of the product. In food and drink containers, the numbers 1, 2, 4, and 5 are free of BPA and phthalates. But avoid microwaving even these plastics —or reusing them.(To learn more about safety and plastics, visit healthylegacy.org.

If you’re concerned, wood, glass and cloth make good alternatives to plastic. Or you can buy plastic toys made in countries that have bans on certain plasticizers.

“I have two rubber duckies sitting on my desk,” says Lindsay Dahl, project coordinator at Healthy Legacy, an advocacy group that opposes toxic chemicals in everyday products. “One has phthalates. One doesn’t. The one that does is sold in the United States. The one that doesn’t is sold in Europe.”

When in doubt, call the company to ask about what’s in their plastics. While you’re on the phone, tell them what you think about the issue. They might be interested to know that kids are keeping an eye on them.

Teacher’s Question Sheet: Our Plastic World

SCIENCE

Before reading:

1. What do you own that’s made out of plastic?

2. Why do you think those items were not made out of some other substance — such as wood, glass, or metal?

3. What do you think the advantages are of something being made out of plastic?

During reading:

1. What is plastic? Why might some types pose a health concern?

2. What is a plasticizer? How does it work?

3. What are hormones and how can a building block of plastics resemble a hormone?

4. How strong is the evidence that ingredients of plastics might affect health?

5. Are all members of the population at similar risk from plastics’ ingredients? Why or why not?

After Reading

1. Now that you know there are potential risks from using plastics — but that the human risks have not been proven yet — how important do you think it would be to avoid using plastic items?

2. For which plastic items in your home or school do you think there might be good substitutes? For which can you think of no substitutes?

3. Plastic baby bottles have been considered a potentially big concern. Moms used to use glass bottles. What are at least three reasons why modern moms might prefer plastic?

4. The author says these junk pieces travel at breakneck speed. Do you think that would make them more or less of a danger to astronauts in orbit?

5. If you think plastic items may pose a health risk, what should we do with all of those that are in our homes? How would you discard them? What might be the best way to ensure that plastic trash doesn’t become a hazard in the trash?

6. Do you think plastic trash in lakes and streams would pose a risk to fish and other aquatic life? Why or why not?

SOCIAL STUDIES

1. How has the widespread availability of plastics in the last 50 years changed society? To figure out, imagine a world where all of today’s plastics were instead made of wood, rubber, metal, stone or glass.

2. What features of plastic make them better than wood, rubber, metal, stone or glass? Hint: Compare the cost, weight and flexibility of plastic items against similar materials made from wood, rubber, metal, stone or glass.

3. If plastics were totally nontoxic, that is posed no health risk, what aspects of plastic items might make less desirable than similar items made from other materials?

LANGUAGE ARTS

1. Write a short essay on why plastic baby bottles are better or worse for today’s infants. Imagine having to explain to your mom or a neighbor — someone who knows nothing about the science plastics — why concerns have been raised about the safety of plastics. Explain why you think this mom should or should not be concerned about these new studies.

2. Imagine a world in which all plastics were banned. Describe in a 10 sentences or less how this would change your environment? Hint: Consider what things in your bedroom, your game room, your kitchen and your yard might be different.

3. Hold a classroom debate on the value of keeping plastics. Let one group argue persuasively that any benefits they pose would outweigh their risks. Let the other group argue that their potential risks outweigh the benefits.

Most kids already have a ton of energy, but kids who drink a lot of cola often end up even more wired than usual. The soda’s high sugar content is partly to blame, but cola also usually includes an energy-sparking chemical called caffeine.

Drinking caffeinated soda can give kids a burst of hyperactive energy.

iStockphoto.com

Like cola, coffee is full of caffeine. That’s why many adults drink it first thing in the morning to help them wake up. The chemical is also naturally found in tea, chocolate, and hot cocoa. Because people crave the caffeine kick—and may even become addicted to it—food manufacturers add the chemical to many other sodas as well as to energy drinks and snacks.

Parents and teachers usually try to keep kids away from caffeine. But is this chemical actually bad for your health? The answer is complicated.

Good caffeine, bad caffeine

First the plus side. Some studies have shown that caffeine might help people respond to things more quickly and even run longer. Scientists have also recently found evidence that caffeinated coffee and tea can help protect the heart, brain, and other organs from disease.

On the other hand, too much caffeine can make people anxious and unable to sleep. A 2003 survey of more than 200 students in grades seven through nine found that kids who drank a 16-ounce bottle of cola slept less, woke up more often, and felt more tired the next day than kids who drank less caffeine. This is worrisome because sleeping well is an important part of staying healthy (See “Getting Enough Sleep”).

Caffeine can also raise your blood pressure, increase your heart rate, and make you feel more stressed, which may eventually lead to heart disease and other health problems.

“If you feel a lot of pressure at school, caffeine is going to make you feel even more anxious,” says Jim Lane, a psychologist at Duke University Medical Center in Durham, N.C.

Roasted coffee beans, like these, are ground and brewed into steaming cups of coffee. The fragrant beverage is the main source of caffeine for most adults.

Wikipedia

Love it or hate it, caffeine is hard to avoid. Coffee shops crowd city streets and malls. Vending machines offer caffeinated sodas in schools. And even though caffeine-free versions of coffee, tea, and cola are widely available, more than 80 percent of adults consume caffeine regularly in North America, according to a 2004 study, mostly in the form of coffee. And kids today are drinking more and more soda, caffeinated or not.

Some 30 percent of 8-to-13-year-olds surveyed by researchers at the University of Minnesota said that they drink soft drinks every day, according to a study published last year. And more probably would if they could: 95 percent of kids in the survey said they “like” or “strongly like” the taste of soda.

You’re feeling sleepy . . . NOT!

Caffeine works by blocking the effects of a sleep-inducing substance produced by your body called adenosine. The substance accumulates inside you throughout the day.

As adenosine levels rise, you become calm and drowsy. Later, as you sleep, adenosine levels drop. When you wake up, the cycle starts again. By not allowing adenosine to build up, caffeine keeps you feeling fired up—as if you’re ready to face a tiger attack.

Human brains aren’t the only ones that feel the effects of caffeine. These images show how an extreme amount caffeine affects the brain of a tiny creature. In this case, the top picture shows how a spider spins its web before caffeine and after (bottom).

NASA; Wikipedia

Caffeine raises the amount of sugar in your bloodstream, even if there is no sugar in your caffeinated drink. That’s what gives you extra energy. The chemical also increases your blood pressure, which may make you feel as if your chest is pounding. But if you consume too much caffeine, you will probably feel nervous and sick.

Caffeine claims for brains

People say they like caffeine because it makes them feel alert. In experiments, people who are given caffeine say they feel more awake than do people who have been given a caffeinefree pill or beverage instead, says psychologist Peter Rogers of the University of Bristol in England.

The caffeine in cola beverages like this one affects your brain and nervous system in ways that have nothing to do with sugar or other ingredients.

National Cancer Institute/Wikipedia

In other studies, caffeine appears to shorten reaction times: People press a button more quickly after seeing a symbol appear on a computer screen after they’ve had some caffeine.

On the basis of such findings, it’s tempting to conclude that caffeine helps people respond more quickly and pay better attention. However, says Rogers, there is another, more likely, conclusion.

Studies show that the people who do better on tests after taking caffeine tend to be regular caffeine users already. In other words, they are probably addicted to the chemical.

Taking caffeine away from habitual users causes them to have symptoms of withdrawal, such as headaches and sleepiness. It also slows their reaction times. So, when these people are given their daily dose of caffeine, they feel better and perform better on reaction-time tests than they do without it.

Coffee and other caffeinated beverages can be addictive, even for children.

iStockphoto.com

People who aren’t addicted, on the other hand, may feel jittery and more awake after taking caffeine, but the chemical doesn’t improve their performance on reaction-time tests. And regular caffeine users who get caffeine before the tests aren’t any more alert or quicker to react than people who don’t normally use the chemical and haven’t taken any.

Giving athletes a jolt

Caffeine has become popular with exercisers looking for an extra boost of energy. Research shows, however, that caffeine helps only athletes who are already in top condition and only when they are pushing themselves as hard as possible, says Terry Graham, a caffeine researcher at the University of Guelph in Canada.

In one study, Graham challenged nine runners to run on a treadmill at a very fast pace. On average, these athletes were able to run for about 32 minutes without caffeine. With caffeine in their systems, they ran 7 to 10 minutes longer.

Athletes often take caffeine for an extra boost of energy. But the chemical doesn’t necessarily make them faster or stronger.

iStockphoto.com

Though caffeine may help the performance of world-class athletes, it may harm the health of people who are overweight. Graham’s other research has shown that caffeine interferes with the body’s ability to process sugars, which may lead to a disease called type 2 diabetes.

Kids, who tend to be smaller than adults, feel the various effects of caffeine more strongly than adults do. And just like adults, kids and teens can become addicted to the chemical.

A can of caffeinated soda every now and then is probably OK, nutritionists say, but sip carefully!

The following list shows how many milligrams (mg) of caffeine are contained in some popular products. All beverages refer to an 8-ounce (1-cup) serving, unless otherwise noted.

Regular brewed coffee: 135 mg
Red Bull (8.5 oz): 80 mg
Black tea: 40-70 mg
Java Water: 62 mg
Starbucks Coffee Ice cream (1 cup): 40-60 mg
Espresso (1 oz): 30-50 mg
Green tea: 25-40 mg
Mountain Dew and Diet Mountain Dew: 37 mg
Diet Coke: 34 mg
Hershey’s Special Dark Chocolate Bar (1 bar – 1.5 oz): 31 mg
Pepsi: 28 mg
Diet Pepsi: 27 mg
Coca-Cola Classic: 26 mg
Snapple Iced Tea: 24 mg
Jolt gum (1 piece): 20 mg
Hershey’s Milk Chocolate Bar (1 bar – 1.5 oz): 10 mg
Hot cocoa: 5 mg
Chocolate milk: 5 mg
Decaffeinated coffee: 5 mg
Decaffeinated black tea: 4 mg

Going Deeper:

Additional Information

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Word Find: Feel the Buzz