EDCs – Disrupting the Cycles of Life
Endocrine Disrupting Chemicals (EDCs) are now recognised as an urgent environmental threat to human health worldwide. Common EDCs such as Bisphenol A (BPA), Per- and polyfluoroalkyl substances (PFAS), and phthalates are found in numerous household items – from food containers to fabrics, and electronics to toys. Yet these everyday substances are also well known for their hormone alteration properties – leaching into the environment to interfere with the endocrine system by mimicking, blocking and otherwise disturbing hormone function.
The link between reproductive failure and toxic chemicals – in particular the pesticide dichlorodiphenyltrichloroethane (DDT) – was first made in the 1960s. Since then, a growing body of research has advanced global understanding of EDCs and their harmful effects on humans – and led to substantially increased scrutiny from scientific and health organisations across the world.
A recent report by the Endocrine Society made a ‘conservative estimate’ that more than 1,000 chemicals registered for production and use today may be EDCs. The US Food and Drug Administration-initiated Endocrine Disruptor Knowledge Base project has also recorded more than 1800 chemicals that disrupt at least one of three endocrine pathways (oestrogen, androgen, and thyroid). Kahn et al. report, meanwhile, that 320 of 575 chemicals screened on the orders of the European Commission showed evidence or potential evidence for endocrine disruption. Phthalates, for example, can produce oestrogen-like effects that interfere with endocrine function in the testis – reducing semen and sperm and sperm motility, producing abnormal sperm morphology and, in serious cases, testicular cancer. There is also strong evidence for a link between PFAS and a wide range of diseases, including child and adult obesity, gestational diabetes, reduced birthweight, endometriosis and breast cancer. Cases of IQ loss and intellectual disability have also been associated with prenatal exposure to both organophosphate pesticides and polybrominated diphenyl ethers (PBDEs) commonly used as flame retardants.
Research has also confirmed that EDCs’ ability to interfere with the endocrine system is not just a threat to the health of humans who are alive now. The endocrine glands and the hormones they produce are vital in enabling our bodies to adapt to their environments, but also to reproduction and the normal body and brain development of coming generations. Therefore, whilst mature individuals may suffer personal body burdens and increased mortality risks as a result of EDC exposure, foetal and infant endocrine systems are also vulnerable to their effects. For example, girls exposed to the anti-miscarriage drug diethylstilbestrol (DES) in the womb often develop reproductive tract malformations. Moreover, some go on to contract rare reproductive cancers in adolescence that are normally seen only in postmenopausal women.
Also concerning for our future health is the ability of EDCs to act on germ cells in the foetus, meaning that the endocrine systems of three generations are exposed at the same time. EDCs have been demonstrated to cause epigenetic modifications to how DNA is turned into proteins, and these can also be inherited over one or more generations. Indeed, some of the epigenetic changes that EDCs make to germ cells are thought to be permanent and heritable by great-great-grandchildren, and beyond.
The heavy toll that EDCs take on public health in terms of disease, disability and healthcare costs has led to gradually increasing scrutiny and regulation of EDCs across the globe – a process that is only likely to gather pace in years to come. In 1999, the European Union (EU) took steps to prioritise substances for further evaluation as EDCs, monitor EDC exposures and effects, as well as developing and validating new testing methods. As Kassotis et al., report, European consumer, health, and environmental protection regulations were then amended progressively to account for EDCs while, in 2018, the EU also pledged to ensure its regulations regarding EDCs remained state-of-the-art. Regulators in America, meanwhile, have faced calls to abandon their risk-based approach to EDCs and adopt the more cautious precautionary principle employed by the EU.
The scientific consensus is, meanwhile, that much work remains to be done on testing – and on the wider regulatory framework – in order to minimise human exposure to EDCs. In 2012, The World Health Organisation and the United Nations Environment Programme issued a report recommending improved testing and reduced exposures to endocrine disruptors. This report was also endorsed by more than 100 countries at the 4th International Conference on Chemicals Management in 2015. The EU’s 2018 statement also described reliable testing to identify EDCs as an “area where science has significantly progressed but needs to advance further”, and pledged to support further research. Finally, the European Parliament commissioned its own scientific study, published in 2019, which called for further research on the effects of endocrine disruptors and the development of alternatives to them.
Research into the effects and suitability of EDCs is such a rapidly-developing field that laboratory scientists are likely to find themselves working to evaluate a new generation of chemicals, themselves intended to provide alternatives to some particularly unsuitable endocrine disruptors. In a review last year of recent literature, Kahn et. al identified a number of new exposure outcomes with substantial human evidence – including “effects on human health due to replacements of EDCs by compounds that have had little testing.” They included the neurodevelopmental effects of pyrethroids - a replacement for organophosphate pesticides – and organophosphate flame retardants (OPFRs), which are used as substitutes for BFR (brominated flame retardant) versions. The Kahn review also raised concerns about the metabolic effects of bisphenol S and other BPA analogues, novel short-chain PFAS, and the reproductive effects of substituting diisononyl phthalate for Di(2-ethylhexyl)phthalate (DEHP).
Finally, increased focus on the epigenetic effects of EDCs may also have positive consequences for the development of novel therapeutics. Writing earlier this year, Shi et al. raised the prospect of manipulating epigenetic mutations in order to prevent or treat disease. Since epigenetics are reversible, there may therefore be potential in reversing disease-related epigenetic changes via the development of new molecularly targeted drugs.
TRC offers a wide range of EDC and other toxin standards, as well as their metabolites and isotope labelled alternatives, to support your laboratory’s analytical testing.
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