Study Finds Link Between Plastics Chemical, Disease
Water bottles made with the controversial carbonate plastic bisphenol A, or BPA - Water bottles made with the controversial carbonate plastic bisphenol A, or BPA. (David McNew/Getty Images)
A new study could change the debate over the safety of bisphenol A, a compound found in many plastics.
It suggests that there is an association between higher exposures to BPA and the development of heart disease and diabetes.
The study, appearing in this week's Journal of the American Medical Association, finds that adults with the highest levels of BPA in their urine were more than twice as likely to report having diabetes or heart disease — compared with adults with the lowest levels of the chemical in their urine.
(David McNew/Getty Images)
Though it brings up new possible human health risks, the study, which is being discussed today at a meeting of the Food and Drug Administration's science advisory board, offers no conclusive answers. It does not prove a cause and effect between use of plastic food containers and the development of diabetes or heart disease.
"We don't have a lot of evidence in people about the effects of BPA. This is one of the first studies, and it finds something disturbing. It's suggesting there may be harm in adults, which we didn't really believe based on the animal studies," says David Schardt, a staff scientist with the Center for Science in the Public Interest.
The study uses data drawn from the National Health and Nutrition Examination Survey — a survey conducted by the federal government — isolating a group of adults between the ages of 18 and 74 who are representative of the U.S. population at large. The survey asked a series of health-related questions, and participants provided a urine sample. Researchers then tested the urine samples for a range of compounds, including bisphenol A.
(David McNew/Getty Images)
"We were interested in diseases of the 50 and older age group and that's originally what we looked at. And then we realized that these associations went into the larger adult populations. And it just turned out that these signals were exceptionally strong and exceptionally robust," says David Melzer, the study's director and professor of epidemiology and public health at Peninsula Medical School in England.
The researchers adjusted for things like weight and smoking, but the association between high BPA urine levels and likelihood of having the diseases held.
"If you could take two individuals with same sex, race, age, ethnicity, body build, cigarette smoking status, and had one individual that [had] low levels of BPA and one individual that had high levels of BPA, the individual with high levels of BPA would be more likely to also report being a diabetic or having cardiovascular disease history," says Ken Portier, a statistician with the American Cancer Society and an expert at interpreting these kinds of snapshot-in-time studies.
Portier says the findings are certainly strong enough to merit follow-up, and the next step might be to look at another group of the survey participants and see if the associations hold up.
Melzer is scheduled to discuss his findings today at a Food and Drug Administration meeting where the agency has issued a draft proposal on bisphenol A.
At this time, the FDA finds the current level of exposure to BPA through food containers safe.
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Where is BPA found?
The National Toxicology Program says the main source of human exposure to bisphenol A, or BPA, is the tiny amounts that leach from Nalgene-type polycarbonate water bottles and from metal cans — that could include canned vegetables and fruits — lined with an epoxy resin that contains BPA. The chemical is also found in baby bottles, tableware and food storage containers.
Does BPA cause health problems?
Studies about the effects of BPA have been conflicting. Some animal studies have suggested a link between BPA and effects on the brain, behavior and the prostate gland — and raised concerns about the effects of exposure on the developing fetus and young children. But there are no conclusive studies linking BPA to human health problems.
It's also unclear what determines how much leaching occurs. It may depend on the temperature of the liquid or bottle or how the plastic is reused.
What should I avoid?
To minimize exposure to BPA, the National Toxicology Program recommends that people avoid microwaving plastic food containers or washing them in the dishwasher with harsh detergents. Repeated exposure to high temperatures and harsh cleaning agents can deteriorate the plastic and release BPA.
Additionally, some sources, such as NTP, have advised consumers to avoid hard, clear plastic containers with the No. 7 on the bottom. While the chemical industry maintains that plastic bottles contain little BPA and leach trace amounts too low to be harmful to humans, some companies have voluntarily elected to sell BPA-free products. Nalgene sells BPA-free water bottles, and retailers such as Toys R Us and Wal-Mart offer baby bottles and other children's products that are BPA-free.
— Kathleen Masterson
MADELEINE BRAND, host:
This is Day to Day. I'm Madeleine Brand.
ALEX COHEN, host:
And I'm Alex Cohen. Today, a panel of scientists gathered at the Food and Drug Administration is looking into the controversy over Bisphenol A. That's the organic compound found in all sorts of things, including the plastic used in some brands of water bottles. Recent studies have linked Bisphenol A to cancer and obesity. A new study published this morning by the journal of the American Medical Association suggests that people exposed to lots of it are more likely to be diagnosed with diabetes and heart disease. NPR's Allison Aubrey reports.
ALLISON AUBREY: The very first point to make in a story about the possible risks linked to the plastics compound Bisphenol A is that this latest study offers no conclusive answers. It does not prove a cause and effect between some of the microwave dinner trays we've all eaten out of and development of diabetes or heart disease. What the research does do is help scientists understand how this chemical may work in the human body. David Schardt is a staff scientist with the Center for Science in the Public Interest.
Mr. DAVID SCHARDT (Senior Nutritionist, Center for Science in the Public Interest): We don't have a lot of evidence in people about the effects of BPA. This is one of the first studies, and it finds something disturbing. It's suggesting that there may be harm in adults, which we didn't really believe based on the animal studies.
AUBREY: The study published today draws on a survey done by the federal government called the National Health and Nutrition Examination Survey. Basically, researchers identify a group of adults between 18 and 74 who are representative of the U.S. population at large. It asks a series of health-related questions, including which diseases people have been diagnosed with.
A few years ago, participants in this survey also agreed to a urine sample, and researchers tested for a range of compounds, including Bisphenol A. The analysis published today finds that the adults with the highest levels of BPA in their urine were more than twice as likely to report having diabetes or heart disease, compared to adults with the lowest levels of the chemical in their urine.
Researcher David Melzer of the Peninsula Medical School in England directed the study. He says his team never anticipated these associations with these major diseases.
Dr. DAVID MELZER (Epidemiology and Public Health, Peninsula Medical School, Exeter, England): The whole study is surprising in one sense, in that we are interested in the diseases of the 50-and-over age group, and that's originally what we looked at. And then we realized that these associations went into the wider adult populations. And, you know, it just turned out that these signals were just exceptionally strong and exceptionally robust.
AUBREY: Strong and robust, even when his team adjusted for things like weight and smoking. Now, to get a reality check on what these findings mean, we called Ken Portier. He's a statistician with the American Cancer Society and an expert at interpreting these kinds of association studies. We reached him on his cell phone.
I'm wondering if you might help us interpret these findings. What does Dr. Melzer mean when he says that these signals between the diseases he looked at and the plastics exposure are very strong and robust?
Mr. KEN PORTIER (Program Director, Statistics, American Cancer Society): Well, one way of looking at it would be, if you could take two individuals with the same sex, the same age, race ethnicity, level of education, income, body build and cigarette smoking status, and you had one individual that had low levels of BPA and one individual had high levels of BPA, the individual with high levels of BPA would be more likely to also report being a diabetic or having a cardiovascular disease history.
AUBREY: And, of course, that doesn't mean that BPA caused it. It just means there's an association there.
Mr. PORTIER: Correct.
AUBREY: Portier says the findings are certainly strong enough to follow up on. The next step might be to look at another group of the survey participants to see if the associations hold up. David Melzer is scheduled to discuss his findings today at a Food and Drug Administration meeting. The agency has issued a draft proposal on Bisphenol A. It finds that current level of exposure to BPA through food containers is thought to be safe. Allison Aubrey, NPR News, Washington. Transcript provided by NPR, Copyright National Public Radio.
