The endocrine system participates in the control and regulation of numerous physiological functions of the organism such as reproduction, immunity, metabolism and behavior.
It consists of three main components that are connected to each other: glands (located in various parts of the body that produce hormones), hormones (circulate in the body and affect the function of organs and tissues) and receptors (they bind hormones and are present on the cells).
Hormonal balance is essential for maintaining the functioning of the organism, for example estrogen and testosterone promote correct sexual development and regulate the passage to puberty; thyroid hormones control development and metabolism.
Endocrine disruptors are chemicals that can alter normal hormone balance by turning on, off or changing the signals sent by hormones, causing adverse effects in an organism, its offspring or a sub-group of the population.
Furthermore, the same endocrine disruptor can cause different effects in relation to sex, hence the need to evaluate them separately in males and females, also in terms of greater or lesser vulnerability.
Substances with endocrine disruptive characteristics
Substances with characteristics of endocrine disruptors are many and can be divided into several classes:
- natural chemicals, including toxins produced by plants (phytoestrogens) and some types of fungi
- synthetic chemicals, Which:
- pesticides (insecticides, fungicides)
- medical and consumer products (example, additives in plastics such as phthalates and bisphenol A)
- industrial products (for example, polychlorinated biphenyls, perfluorinated, polybromo diphenyl ethers)
- combustion products (e.g. dioxins)
- trace elements (mercury, arsenic)
- pharmaceutical products, as contraceptives and treatments for cancers that respond to hormone therapies
Examples of Endocrine Disruptors
Examples of chemicals with endocrine disruptive characteristics include:
- industrial products (perfluorinated, polychlorinated biphenyls)
- additives in plastics (phthalates and bisphenol A)
- regulated substances used in agriculture for plant protection (pesticides)
Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid ammonium salt (PFOA) are the chemical compounds present in the environment. They are used in industrial processes and consumer goods (carpets and coatings in water-repellent and stain-resistant fabric), paper products for food use, some paints for floors.
Polybromodiphenyl ethers (PBDE) are industrially produced chemicals used mainly as flame retardants, in order to make products less flammable. They are included in the list of persistent organic pollutants (POPs) because they tend to accumulate in the fatty tissues of organisms. They can be used in the manufacture of furniture, curtains, carpets, polyurethane foam padding.
Diethylhexylphthalate (DEHP) is a plasticizer belonging to the family of phthalates mainly used to make the polyvinyl chloride (PVC). It is a pollutant possibly present in disposable plastics, trays, films, transport packaging. PVC is used for floors and wall coverings.
The Bisphenol A (BPA) it is a precursor compound of some plastic materials and chemical additives. It is used in food-grade containers and epoxy resins (the inner lining in most food and beverage cans). The uses of BPA range from polycarbonate plastics used for bottles and food containers, to thermal paper for receipts and dental devices.
The Chlorpyrifos (CPF) is a widely used organophosphorus pesticide for both agricultural and domestic use, albeit with limitations; is a known inhibitor of acetylcholinesterase, an enzyme that controls neurotransmitter levels acetylcholine in the central and peripheral nervous system. CPF has the ability to act as an endocrine disruptor by acting at the level of the thyroid gland and producing oxytocin and vasopressin, two neuroendocrine regulators synthesized in the "area of the brain called hypothalamus. These alterations are observed at doses of CPF below the toxicity threshold for the nervous system.
Effects on health
Endocrine disruptors can act through several mechanisms:
- mimic the biological activity of the hormone naturally present in nature, the binding of this substance to the receptor present on the cell can induce the cellular response at the wrong time or in excessive quantities (agonistic effect)
- bind to the cell receptor but without activating it, preventing the physiological link between this and the hormone (antagonistic effect)
- bind to transport proteins present in the bloodstream, making them inaccessible to the hormone, whose circulating levels therefore increase
- interfere with metabolic processes, modifying the synthesis rate and / or the physiological degradation rate of hormones
Some typical aspects characterize endocrine disruptors:
- they cause effects even at lower doses than those that cause general toxicity, effects on tissue or an organ, etc.
- they can give different responses at different doses, that is, the severity of the effect does not necessarily increase as the dose increases
- more pronounced effect depending on the period of life in which the organism is exposed, for example in critical periods in which the endocrine system plays a key role such as pregnancy, development, growth
- appearance of the effects even in periods of life other than those in which the exposure occurred, for example, for exposure during fetal life, effects could occur in the period of puberty
- transmission of the effect also to future generations
- exposure of the population to various chemicals whose blending effect is still little known
Numerous experimental studies and epidemiological studies highlight the effects of endocrine disruptors on health related to:
- structure and function of the organs of the reproductive system:
- female, pubertal development, cycle irregularity, impaired fertility, infertility, polycystic ovary syndrome, endometriosis, premature birth, breast cancer
- male, hypospadias (malformation of the urogenital tract), cryptorchidism (failure of one or both testicles to descend into the scrotal sac), poor semen quality, prostate cancer
- thyroid homeostasis
- immune system
- neuro-endocrine system, neurodevelopment and behavior
- metabolism and metabolic syndrome (obesity, diabetes and cardiovascular diseases)
- energy control
The population and the environment can be exposed to endocrine disruptors derived from various sources.
Uncontrolled industrial production processes, incorrect industrial and domestic disposal and discharges, non-compliant waste disposal plants can lead to the release of endocrine disruptors into the environment.
The use of pesticides and the release of chemicals from commonly used materials and products contribute to the daily exposure of the population.
Endocrine disruptors can be found in foods which, therefore, represent an "additional (for some compounds the main) route of exposure.
The more endocrine disruptors are able to persist in the environment, the more prolonged is the exposure of the population, also in consideration of the fact that persistent substances are able to accumulate in organisms.
For some of them, some precautions have been indicated to be put into practice in daily life in order to limit the exposure of adults and children.
Since 1999 the European Commission has adopted the community strategy for endocrine disruptors, updated in 2012 and soon to be revised.
In 2018, the Commission reaffirmed its commitment to minimize the exposure of citizens and the environment to endocrine disruptors.
The objective of the European Community policy is to limit the exposure of the population and the environment to endocrine disruptors by intervening at the legislative level, developing criteria for the identification of EDs, including substances of concern including endocrine disruptors in the list of substances candidates for revision or replacement ("REACH regulation"), promoting scientific research actions.
To date, 320 substances have been identified that cause obvious or potential effects on the endocrine system and some of them are already in place with restrictions.
In fact, numerous regulations concern endocrine disruptors with specific regulations concerning pesticides, biocides, medical devices, water, including a directive on drinking water (under development), chemicals in general ("REACH regulation").
As regards materials in contact with food products, cosmetics, toys and the protection of workers in the workplace, substances with endocrine disrupting properties have been subjected to regulation on a case-by-case basis.
The "Organization for Economic Cooperation and Development (OECD) has defined guidelines for specific investigation methods (in vitro and in vivo tests) and internationally accepted for the identification and evaluation of endocrine disruptors.
In 2018, the European Chemical Agency (ECHA) and the European Food Safety Authority (EFSA) drafted the Guideline for the identification of endocrine disruptors in the field of biocides. and plant protection products.
European life persuaded project (ISS). Ten practical tips to reduce exposure to plasticizers for children and adults
Ministry of the environment and the protection of the territory and the sea. Know, reduce, prevent endocrine disruptors: a decalogue for citizens
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Organization for Economic Co-operation and Development (OECD). Revised Guidance Document 150 on Standardized Test Guidelines for Evaluating Chemicals for Endocrine Disruption. OECD Publishing: Paris, 2018 (OECD Series on Testing and Assessment)
European Commission. Endocrine Disruptors (English)
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European Commission. Endocrine disruptors. Overview
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