Last week, hard plastic baby and water bottles were not considered harmful.
Now, in the eyes of many users, they are toxic. Yesterday,
So how dangerous are these bottles? And what should consumers do about the risk?
"The truthful answer is that nobody knows" their full health impact yet, said David Ozonoff, a professor of environmental health at the Boston University School of Public Health. "And because we don't know, it's prudent to avoid something that is avoidable."
At the heart of the debate is an odorless, tasteless chemical called bisphenol A that is one of the most commonly used synthetic compounds. It is used to line most canned goods, from soups to soft drinks, to prevent corrosion. It helps make sunglasses and compact discs durable. And it strengthens virtually all transparent, light weight hard plastic baby and water bottles. The chemical has been used for decades, and millions of pounds are produced in the United States each year.
Animal studies have linked exposure to small amounts of bisphenol A to reproductive problems and possible cancers later in life, though the level of risk is unknown. A small body of research suggests that exposure to the chemical in the uterus could contribute to later obesity.
But chemicals that harm animals are not always bad for humans, particularly in the small amounts to which most people are exposed. Industry representatives say no study has proved a link between bisphenol A and health problems in humans.
Still, the US National Toxicology Program, part of the Department of Health and Human Services, last week released a draft report on the chemical, saying there was "some concern for neural and behavioral effects in fetuses, infants, and children at current human exposures." A few days later, Wal-Mart said it would stop selling baby bottles made with bisphenol A by next year and replace them with a bottle free of the chemical. Nalgene, the maker of the durable and ubiquitous hiking bottle whose parent company, Thermo Fisher Scientific Inc., is based in Waltham, also said it would replace its bisphenol A bottles in stores.
Last Friday, Health Canada delivered another blow, announcing that the compound was potentially harmful to people, especially newborns and infants. If no new scientific evidence is brought forward in the next 60 days, officials announced they would ban it from all baby bottles in the country.
"We have concluded that it is better to be safe than sorry," Tony Clement, the Canadian health minister, told reporters.
Even before the latest news, environmental websites and parent blogs were aflutter about bisphenol A, debating its dangers and whether it was better to use glass bottles even though they break easily, or how to find bisphenol A-free bottles. They are sold on the Internet but tend to cost more. Baby bottles are of particular concern because more bisphenol A is released when milk or formula is heated in them.
Heather Kane, a Westborough parent of a two- and a five-year-old, mostly uses aluminum bottles instead of plastic. But she said it can be difficult for parents to find alternatives because most are sold only on the Internet and take time to seek out and buy. While that is changing, she questions why stores are not acting more forcefully.
"What I find absurd is that Wal-Mart and these other stores are taking them off the shelves at some future date, but if the bottles are so dangerous, why don't they take them off now?" she said in a phone interview.
A recent study by the US Centers for Disease Control and Prevention estimated that about 93 percent of the US population had bisphenol A in their body. Infants and young children had higher levels than adults. Scientists are most concerned about early development because it is a critical time in determining long-term health. Both the US Toxicology Program and Canadian reviews said there appeared to be a negligible effect from bisphenol A on adults.
"These experiments have been going on for a long time . . . that show exposure in utero could produce alterations in several parts of the reproductive process, and increased risk" of certain cancers, said Ana Soto, a Tufts University professor who studies the effect of endocrine disrupters such as bisphenol A on development. She believes adults should phase out exposure to bisphenol A.
Industry representatives vehemently disagree and say even the proposed Canadian ban in baby bottles is based on the precautionary principle, not hard data that show bisphenol A is dangerous.
"We agree with the scientific and government bodies worldwide who have reviewed the science and support the conclusion that low levels of bisphenol A is not a risk to public health," said Steven Hentges, executive director of the polycarbonate/BPA global group of the American Chemistry Council, which represents chemical manufacturers. The only thing that the chemical industry and scientists agree on is that more studies are needed.
So what should parents do?
"If it is easy for people to reduce their exposure to some sources," such as using a water bottle without bisphenol A, "and if the substitute is not likely to present significant risks itself, then why not?" said James Hammitt, professor of economics and decision sciences at Harvard University, in an e-mail.
Just because studies may fail to provide clear evidence of harmful effects, he wrote, does not mean that the chemical is not harmful under some conditions.
Beth Daley can be reached by email at email@example.com