Scientists are putting together a growing list of synthetic chemicals, known as endocrine disruptors, which have gradually become widespread in our water, air, food and blood, and which have been linked to several troubling health effects.
Even in smaller doses, there's reason to suspect these "forever chemicals", which take ages to break down in the environment, could have long-lasting consequences for our health.
By messing with the glands that secrete and store our hormones, it's plausible that some household chemicals used in food, packaging, cosmetics, household goods, detergents, fabrics, electronics and pesticides - even those that have been phased out or banned - are impacting various aspects of our bodies and brains.
In 2015, an expert panel commissioned by the Endocrine Society identified 15 endocrine disrupting chemicals (EDCs) that are linked with health issues (not the same as causation, which is extremely challenging to establish). In 2017, the United Nations listed 45 known chemicals that are capable of interfering with hormone action.
Now, a team of researchers from the NYU School of Medicine, Duke University, New York University, and other institutions has published a landmark two-paper series on endocrine-disrupting chemicals in The Lancet Diabetes & Endocrinology.
The team aims "to expand on the previous report by identifying new exposure-outcome associations of concern, especially with regard to chemicals that were not widely researched several years ago, such as perfluoroalkyl and polyfluoroalkyl substances (PFAS) and polybrominated diphenyl ethers (PBDEs)."
Their up-to-date analysis of preliminary research reveals evidence is particularly strong when it comes to links between PFAS and obesity, diabetes, reduced birth weight, reduced semen quality, polycystic ovary syndrome, endometriosis, and breast cancer.
The link between PBDEs - widely used as flame retardants - and health issues isn't as strong as for PFAS, but the authors did find evidence these chemicals could be linked to reduced semen quality, polycystic ovarian syndrome, childhood obesity, impaired glucose intolerance, and reduced anogenital distance in boys.
What's more the authors say greater evidence has accumulated that prenatal exposure to bisphenols, organophosphate pesticides and flame retardants could be linked to cognitive issues like attention-deficit disorder, although - again - more research is needed.
At this point, it must be noted that most research on these chemicals is still in its infancy and a lot of it has been done on animal models, although the current analysis does include a number of studies in humans.
Many of the results gathered have been pretty mixed. While there are, for example, several notable studies on endometriosis and EDCs, the results they've produced are inconsistent; a similar issue affects the studies on male sperm, and direct causation is hard to establish.
However, endocrinologists' concern over these chemicals has been growing for decades, and the research is catching up.
"In reviewing hundreds of published studies, we have emphasised the many challenges in unravelling the complex relations of exposure to EDCs with disease and disability across the lifespan," the team writes.
The scientists argue there's now enough evidence for preemptive action, at least until we can ensure these chemicals are actually safe.
"Although systematic evaluation is needed of the probability and strength of these exposure-outcome relations, the growing evidence supports urgent action to reduce exposure to endocrine disrupting chemicals," the authors write.
The authors say their review strengthens the evidence for other EDCs previously listed, while also expanding evidence for new contributors to health issues; as a result, they argue regulating EDCs should be a UN 2030 sustainable development goal.
The US Environmental Protection Agency (EPA) was first warned of the possible health risks of PFAS in 2001. Since then, these chemicals have been found in the blood of nearly all Americans.
While the EPA has a safety threshold for these chemicals, they don't enforce the rules, and some scientists think the dose is not important.
It's important not to jump to conclusions, especially as there are predatory messages out there claiming that your tap water is no longer safe to drink. Not all "chemicals are bad" claims out there can be trusted, or need to be taken into account.
That said, the scientific debate over potential effects of these particular compounds is becoming increasingly robust, and the most radical dissent always appears to come from sources with vested financial interests in the various industries that use these chemicals.
"The past five years of research on EDCs have brought into sharp focus the substantial stakes involved for human health," the team writes.
"Although there are actions that individuals can take to reduce their exposure, the definitive way to make a difference on a population level is through regulation."
The papers were published in The Lancet Diabetes & Endocrinology here and here.