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June 23, 2008

Q&A: Bisphenol A and Plastics

Concerns about the chemicals contained in many plastic bottles and containers leaves many consumers wondering if these products are safe to use. Lynn R. Goldman, MD, MPH, professor in the Johns Hopkins Bloomberg School of Public Health’s Department of Environmental Health Sciences, and Kellogg Schwab, PhD, associate professor and director of the School’s Center for Water and Health, separate fact from fiction.

Question: What is bisphenol A and where does it come from?

Goldman: Bisphenol A or BPA is one of the highest volume chemicals produced worldwide. Over six billion pounds are produced each year. BPA is a manmade chemical that is used in the production of many plastic-containing consumer products. These products include polycarbonate water bottles, epoxy-lined metal food cans and even some dental sealants. Trace amounts of residual BPA are often present in the final product as a result of the manufacturing process. Many scientific studies have shown that this residual BPA can be released from these types of products, particularly if the product is heated.

Question: Is exposure to BPA harmful?

Goldman: In the U.S., the Centers for Disease Control and Prevention (CDC) has monitored urine levels of BPA across the population and has confirmed that exposures are widespread throughout all age and racial groups. We don’t know enough to say whether these levels of BPA are harmful. However, recent studies indicate that current levels of exposure to BPA in early life may have long-term health consequences.

In laboratory animal studies, exposure to BPA in utero and during infancy was found to adversely affect brain development and behavior. Laboratory animal studies also showed that early life exposures may alter development of the prostate gland in males and the mammary gland in females, as well as trigger an earlier start to puberty in females. While this research is limited, these effects occurred at exposure levels to bisphenol A similar to those seen in humans, which led the U.S. National Toxicology Program (NTP) to posit that there is “some concern” about the risk of BPA exposure. Some studies have also shown that laboratory animals exposed to very high levels of bisphenol A during pregnancy have increased fetal death and reduced birth weight and reduced pup growth during infancy. The NTP was less concerned about these effects for two reasons. First, the amounts of BPA that have been found in humans are much lower. Second, human studies conducted to date have not found any evidence for reduced birth weight or other adverse birth outcomes with BPA exposures.

Question: Is it safe for people to drink out of plastic water bottles?

Schwab: Consumers should be more concerned with the initial quality of the drinking water inside a container than they should be about the composition of the container. Many people buy bottled water because they do not feel comfortable drinking tap water. The truth is that tap water in the United States is more highly regulated and monitored for quality compared to bottled water. Also, it is important to drink enough water and to remember that our requirements for water are greater in the heat and when we exercise.

Most single-use water bottles sold in the United States are made from BPA-free plastic, but some reusable containers are made from plastic containing BPA. Given a choice, a product absent of BPA should be considered. It is a good idea to bring water with you for long car trips and activities like sports and hiking. Since these water supplies are likely to be in hot vehicles and in the hot sun, BPA-free containers should be considered. Remember to clean reusable bottles between uses and let them dry upside down so they are ready the next time you need them.

Consumers should also consider the environment when purchasing bottled water. Single-use water bottles make a substantial contribution to our landfills. According to the U.S. Environmental Protection Agency, about 20 percent of disposable plastic water bottles are recycled. It also takes additional energy and resources to bottle water and ship it to store shelves. Thus it is probably wiser, environmentally, to drink water from the tap, from reusable containers.

Question: What about BPA in baby bottles, infant formulas and human milk?

Goldman: We know that the time of greatest sensitivity to BPA occurs in utero (passed directly from mother to baby) and during infancy and early childhood. By far, the highest estimated exposures are to infants who are fed liquid formula that has been packed in food cans with epoxy linings, and served in BPA-containing polycarbonate bottles. We also know that the metabolic pathways for eliminating BPA have not matured in newborns.

Given its many nutritional and immunologic benefits, human milk is considered to be the most appropriate food for nursing infants. The American Academy of Pediatrics recommends exclusive breastfeeding for approximately the first six months of life. Human milk also has much lower levels of BPA than all forms of infant formula.

If infant formula is needed, powered infant formula has lower levels of BPA than liquid formula. As a precaution, glass bottles or BPA-free plastic bottles can be used for bottle feeding. You should avoid using polycarbonate bottles that have the recycling code “7” on the bottom. (The code “7” includes a number of other plastics as well as polycarbonates.)  If you do use plastic bottles, do not heat them in the microwave and, after washing, allow them to cool off before adding formula.

Question: Water bottles aside, are plastic products for daily use a potential concern?

Goldman: We use plastics for many purposes. They are everywhere in our environment. If you are concerned about exposure to chemicals in plastics, a common sense approach would be to use alternatives when it is practical and safe. For instance, when cooking you may wish to use products made from inert materials like stainless steel or glass instead of plastic. It is also good advice to follow directions and to only use plastic products as they were intended by the manufacturer, particularly when cooking. Metal items and many plastic containers are not safe to use in a microwave oven. For microwaving, use glass or plastic containers that are labeled “microwave safe”.

Question: Are there concerns about cooking with plastics?

Schwab: Whenever you heat something you increase the likelihood of pulling chemicals out. This is the same process we use in the lab to extract chemicals from materials we want to analyze. Chemicals can be released from plastic packaging materials like the kinds used in some microwave meals. The same can occur with the use of polycarbonate plastic eating utensils.

Again, the best thing to do is to follow the directions and only use plastics that are specifically meant for cooking. Newer biodegradable products or stainless steel are good alternatives to polycarbonate plastic eating utensils.

Question: What are phthalates?

Schwab: There is another group of chemicals, called phthalates that are also associated with manufacture of plastics. Phthalates are sometimes added to plastics, like polyvinyl chloride or PVC, to make them flexible and less brittle. Although they are not typically found in plastics used for water bottles sold in the U.S., they used to be found in baby bottle nipples and teething toys. Phthalates are environmental contaminants that can exhibit hormone-like behavior by acting as endocrine disruptors in humans and animals. If you heat up plastics, you could increase the leaching of phthalates from the containers into water and food. Containers labeled “microwave safe” should have less leaching than other plastic containers.

Microwaving food in contact with plastic wrap is another potential source of exposure, but a few years ago manufacturers in the U.S. replaced PVC plastic wrap with low-density polyethylene (LDPE), which does not contain phthalates. Plastic wrap from other countries or marketed for commercial or non-food uses may still contain PVC.

The Food and Drug Administration has found that only small amounts of phthalates migrate from plastic containers and plastic wrap into food. However, you can reduce the potential for exposures by using glass containers or plastics that are known to be free of phthalates, as well as plastic wrap that are known to be phthalate-free. In any case, make sure that the plastic wrap is not in contact with the food (which can melt plastic onto the food).

The U.S. Department of Agriculture Food Safety Inspection Service (FSIS) has some helpful guidelines for cooking with plastics in microwave ovens.

Question: There are numerous emails warnings that claim dioxins can be released by freezing water in plastic bottles. Are they true?

Schwab: No, it’s a hoax. There is no truth to that myth.

Dioxins are organic environmental pollutants, which include 75 different chlorinated molecules of dibenzo-p-dioxin and 135 chlorinated dibenzofurans. Some polychlorinated biphenyls (PCBs) also are referred to as dioxin-like compounds.

Dioxins are formed in the environment by combustion, including wildfires and volcanic eruptions. Today scientists are concerned about the incineration of waste, particularly hospital waste, which contains large quantities of PVC and aromatic compounds that can serve as dioxin precursors. When dioxins are sent into the atmosphere they can become attached to particles and fall back to earth where they bind, or are taken up by fish and other animals. The dioxins get concentrated and stored in animal fat. People are exposed to them mostly from eating meat and fish rich in fat.

While dioxins are extremely toxic, there are no dioxins in plastics. In addition, freezing actually works against the release of chemicals. Chemicals do not diffuse as readily in cold temperatures, which would limit chemical release.--Tim Parsons

Public Affairs media contact: Tim Parsons at 410-955-6878 or tmparson@jhsph.edu.