Bisphenol A-free plastics or BPA, which are widely considered food-safe, are in the news, on account of a new research that says some of the more than 50 BPA-free substitutes may cause ill effects in mice, particularly in reproductive cells. This has to be read in conjunction with the fact that over the past decade, concerns about the health effects of BPA have forced food and beverage companies to largely abandon the use of the common plastic in many household items. If the new results hold in further animal and human studies, they could upend efforts to mollify consumers’ health concerns over the plastics in food and beverage containers.
In 2003, while carrying out mouse studies unrelated to BPA, Patricia Hunt, a reproductive biologist at Washington State University in Pullman, and her colleagues found that the compound was leaching out of plastic cages housing female mice. The result was an increase in chromosomal abnormalities in the lab animals and their offspring. That finding, along with others in animals that suggested BPA “disrupts” estrogen hormone receptors, triggered an avalanche of studies that fingered the compound as interfering with meiosis, the process by which the number of chromosomes is cut in half and chromosomal segments are shuffled during the production of sperm and egg cells. The finding also led to new mouse cages, made of a more durable plastic called polysulfone.
But in recent studies, Hunt and her colleagues again noticed odd results in their mice, as reported in Current Biology. After months of work, the problem was traced to contamination from cages damaged by washing and other normal wear and tear. It was found that the damaged cages were leaching out compounds manufacturers often use to replace BPA, such as bisphenol S (BPS) and diphenyl sulfone. Though it does not contain BPS, it is estimated that polysulfone degraded to produce BPS and other BPA-like compounds. After getting the contamination under control, Hunt and her colleagues decided to test the effects of BPA alternatives directly. They fed pregnant female mice low doses of BPA, BPS, diphenyl sulfone, or a placebo. Compared with unexposed females, those exposed to BPA or its alternatives produced more protein markers of genetic damage during meiosis.
In previous studies, that kind of genetic damage has gone on to cause aneuploidy, an abnormal number of chromosomes that can trigger miscarriage in females and reduced sperm count in males. What’s more, in the current study Hunt and her colleagues showed that the effect lasts beyond the mothers and foetuses directly exposed to BPA and its alternatives. Genetic abnormalities persisted for two generations of male mice unexposed to BPA and its substitutes. Hunt and others suggest that the strong similarities in chemical structure between BPA and some of its alternatives mean that consumers may be wise to be wary of labels that tout “BPA-free” products. Hunt said more work was needed to determine if some replacement bisphenols were safer than others. There were dozens of such chemicals now in use. She also suspected other widely used and endocrine-disrupting chemicals, including parabens, phthalates, and flame retardants, may have similar ill effects on fertility. Hunt’s advice is simple: BPA-free or not, “plastic products that show physical signs of damage or aging cannot be considered safe.”