Bisphenols are a group of industrial chemicals used widely in the manufacturing of plastics and resins. Bisphenol A (BPA) is the most well-known compound, but similar chemicals like Bisphenol S (BPS) and Bisphenol F (BPF) are also common. These compounds are classified as endocrine-disrupting chemicals (EDCs) because they interfere with the body’s natural systems. Research shows that exposure to these chemicals, even at low levels, may pose a risk to human health. Understanding their sources and biological effects is the first step toward minimizing potential harm.
Understanding Bisphenol Compounds and Sources
Bisphenol A (BPA) has been extensively used since the 1960s to create hard, clear polycarbonate plastics and epoxy resins. Polycarbonate plastics are used in many common items, including reusable water bottles, food storage containers, and eyeglass lenses.
Epoxy resins containing BPA are frequently used as protective coatings, particularly to line the inside of metal food and beverage cans to prevent corrosion. The chemical is not permanently locked into these products, meaning small amounts can leach into food and liquids, especially when heated. Dietary ingestion is considered the main route of human exposure.
As concern about BPA grew, manufacturers began substituting it with chemical relatives like BPS and BPF in products labeled “BPA-free.” BPS is notably used as a developer in thermal paper, such as grocery and ATM receipts, allowing for skin absorption upon handling. BPF is utilized in specialized epoxy resins for coatings requiring increased thickness and durability. These substitutes are chemically similar to BPA and are also considered endocrine-disrupting chemicals.
How Bisphenols Affect the Endocrine System
Bisphenols interfere with the body’s endocrine system, which is responsible for producing and regulating hormones. These chemicals possess a structure similar to the natural hormone estrogen, allowing them to interact with estrogen receptors. They act as xenoestrogens, meaning they mimic estrogen and either weakly activate or block the receptor, thereby disrupting normal hormone signaling.
Bisphenols can also disrupt the functions of other hormones, including thyroid hormones. Thyroid hormones are important for metabolic rate, growth, and neurological development. Bisphenols may interfere with the synthesis, transport, and metabolism of these hormones, potentially altering gene expression and signal transduction pathways.
The effect of low-dose exposure is a concern, particularly during critical developmental periods like gestation and early childhood. Even minute concentrations can disrupt the delicate balance of hormone signaling, which orchestrates complex processes like cellular proliferation and differentiation. This disruption can initiate epigenetic changes, which are alterations in how genes are expressed without changing the underlying DNA sequence.
Documented Health Outcomes of Exposure
Exposure to bisphenols is linked to adverse health outcomes, with much of the data focused on Bisphenol A. Because of their hormone-disrupting properties, reproductive and developmental health are primary areas of concern. In males, exposure is associated with reduced sperm quality and fertility, while in females, it is linked to conditions like polycystic ovary syndrome (PCOS) and endometriosis.
Developmental exposure, especially during gestation, is concerning because it can affect the fetus. Studies suggest bisphenol exposure may lead to alterations in reproductive tract development and changes in the onset of puberty, sometimes indicating accelerated puberty. Furthermore, bisphenols have been identified as obesogens, meaning they promote fat cell development and correlate with metabolic disorders.
Evidence points to an association between bisphenol exposure and metabolic dysfunction, including increased risk of obesity, insulin resistance, and type 2 diabetes. Bisphenols impair cellular function, leading to metabolic syndrome by disrupting the processes that regulate glucose and lipid metabolism. Neurological effects are also documented, with elevated prenatal exposure linked to adverse behavioral outcomes in children, such as anxiety, hyperactivity, and cognitive deficits.
Strategies for Minimizing Exposure
Reducing exposure to bisphenols requires practical changes in how food is stored and handled, as food and drink packaging are the primary sources of exposure.
Individuals can minimize exposure by:
- Prioritizing fresh, frozen, or dried foods over canned goods, as can linings often contain bisphenol-based epoxy resins.
- Avoiding heating plastic containers, as warmer temperatures significantly increase the rate at which bisphenols leach into food.
- Using glass, ceramic, or stainless steel for storing and heating food and beverages instead of plastic.
- Selecting glass bottles or BPA-free plastics (codes 1, 2, 4, 5, or 6) for infant feeding supplies.
- Minimizing contact with thermal receipt paper, which contains high concentrations of bisphenols absorbed through the skin.
- Washing hands after handling thermal paper and avoiding alcohol-based hand sanitizers immediately beforehand, as they increase skin absorption.