Endocrine disruptors, the invisible chemicals that trigger disease

Humans are widely exposed to endocrine disruptors, compounds that can mimic the body’s natural hormones and impact health. These chemicals — which are invisible to the naked eye yet pervasive in the environment and everyday products — can interfere with the endocrine system from before birth, influencing reproductive health and contributing to various diseases, including cancer, diabetes, obesity, and attention deficit hyperactivity disorder (ADHD). Recent research suggests that early exposure to certain disruptors may lead to an earlier onset of puberty.

The scientific community is increasingly concerned about human exposure to these chemicals, particularly because they are ubiquitous — found in cosmetics, personal hygiene products, and food packaging — making it challenging to completely avoid them. “Research is focused on two key areas: the mechanisms by which these contaminants interfere with hormone receptors and the extent of human exposure to these compounds. The existing evidence is more than sufficient to warrant preventive intervention,” warns Nicolás Olea, a professor at the University of Granada in Spain and a physician at the city’s Clinical Hospital. Pesticides, heavy metals, bisphenol A, and parabens are among the most well-known and studied disruptors.

If natural hormones serve as messengers — substances that travel through the bloodstream to connect transmitters with receptors, such as the ovaries and breasts —endocrine disruptors interfere with this entire communication network. They mimic the role of natural molecules responsible for signaling and facilitating dialogue between cells and organs. These chemicals can disrupt any part of the communication process, whether by altering hormone transport, blocking receptors, or distorting the growth of hormone-producing cells. “They can affect hormone synthesis, transport, and binding to receptors, thereby increasing or decreasing hormonal activity. While the most common effect is interference with the receptor, they act like hackers of the messages [that hormones convey],” Olea explains.

Over 2,000 chemicals have been identified as capable of interfering with endocrine processes and affecting health. However, according to the researcher from the University of Granada, this may be just “the tip of the iceberg.” “The hormonal systems that have been studied are limited [estrogenic, androgenic, thyroid, etc.]. We suspect there are endocrine disruptors related to vitamin D, which is actually a hormone. But we don’t yet know which substances compete with and interfere in that system,” reflects Olea, who is also a member of the think tank ALIMENTTA.

Martine Vrijheid, director of ISGlobal’s Environment and Health Throughout Life Program, highlights a glimmer of hope amidst this grim outlook for human health: “Overall, the concentrations of these chemicals found in blood samples appear to be very low. However, we need better information on the health effects of even low-level exposure.”

Among the most concerning endocrine disruptors are polybrominated compounds, which serve as flame retardants and are commonly found in many synthetic products and textiles. “People are generally exposed to these indoors, and they are linked to thyroid problems,” explains Olea. Other chemicals of concern include phthalates and phenols, which are also associated with infertility in adults and developmental issues such as growth retardation and ADHD in children.

Scientists are also worried about perfluorinated chemicals (PFAS), known for their ability to repel water and oil while resisting extreme temperatures. “These are concerning because they are not only endocrine disruptors, but also classified as ‘forever chemicals,’ meaning they are highly persistent in the environment and in the human body,” explains Vrijheid. These chemicals can negatively impact the immune system, cause liver toxicity, and harm reproductive health, including infertility. Additionally, they have been linked to diabetes and obesity, and evidence suggests they can affect brain function and neurodevelopment, as noted by the ISGlobal researcher.

Windows of vulnerability

Experts acknowledge the complexity of measuring the impact of each chemical, as the dose-response relationship is not linear; there is not always a proportional relationship between the exposure dose and the magnitude of the effect. Additionally, Olea notes that “there is a background within the organism.” While exposure to endocrine disruptors can occur at any stage of life, there are specific windows of heightened vulnerability.

The prenatal stage, during which the fetus is developing, is one of these critical periods. These chemicals can cross the maternal placenta and potentially interfere with the child’s long-term health. For instance, a study published in JAMA Pediatrics in 2018 found that prenatal exposure to various types of phthalates was associated with delays in language development in children.

The prepubertal stage is another critical window of vulnerability, as it is the time when the body prepares to initiate hormonal activity. A notable phenomenon associated, in part, with exposure to endocrine disruptors is the increasingly early onset of puberty. Research recently published in the journal Endocrinology suggests that musk ambrette — a common fragrance component in soaps, detergents, and creams — along with other synthetic nitro-musks, “could be contributing to the trend of earlier puberty.” The authors note: “Although our in vitro and in vivo data do not offer direct evidence supporting an effect on puberty, they represent a first step toward linking musk ambrette to the activity of the neuroreproductive axis during development. This possibility deserves further study.”

While the scientific findings are limited, this is not the first time such a hypothesis has been proposed. Anders Juul, a pediatric endocrinologist and clinical professor at the University of Copenhagen, told The Lancet that exposure to endocrine disruptors, coupled with increased fat mass, may be driving the “worrying trend toward earlier puberty.” He explained: “Environmental chemicals with hormone-like activities may promote the premature activation of the pituitary–gonadal hormone axis resulting in pubertal development and/or act directly to stimulate the breast gland with estrogenic or anti-androgenic activity.” However, in a recent meta-analysis, Juul was unable to establish a clear association between pubertal age and exposure to any individual chemical.

Chemical combinations

More research is needed, experts agree, to accurately assess the impact of these disruptors. Vrijheid emphasizes the importance of exploring the effects of chemical combinations. “While there are many studies on endocrine disruptors, most focus on a single chemical or perhaps a few from the same group. There are very few studies that analyze the effects of low exposure to multiple chemicals. We live in this chemical soup, and we have limited understanding of what happens when exposed to various endocrine disruptors simultaneously.” A study published last May suggested that exposure to a mixture of these hormonal disruptors is linked to poor metabolic health and contributes to the rising incidence of metabolic syndrome (obesity, diabetes, hypertension) throughout life.

Experts also express concern over the lack of information and clear guidelines for the public. “We could provide better advice on which products to avoid to reduce exposure, but this is challenging due to the insufficient information regarding which chemicals are used in which products. We need better labeling,” states Vrijheid. While individuals can take measures such as reducing their intake of processed or canned foods, thoroughly ventilating and cleaning their living spaces to minimize dust, or avoiding heating food in plastic containers in the microwave, a scientific review last year concluded that “policy which reduces or removes EDC [endocrine-disrupting compounds] in manufacturing and processing across multiple sectors, rather than individual behavior change, may have the greatest impact on population exposure.”

However, the pace of the industry complicates efforts to control the emergence of new disruptors. “When a chemical is banned, it is often replaced by 10 new ones, making it very difficult to keep track,” laments Vrijheid. The industry advances faster than science, and regulators are the slowest players in this scenario, adds Olea. He provides an example: “In 1995, we first published findings indicating that Bisphenol A was present in the coating of tin cans. It wasn’t removed from baby bottles until 2011, and it won’t be banned in the EU until December 31, 2024. Decision-making takes a long time.”

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