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The endocrine system consists of a series of organs. The classical endocrine organs in the body are:
The endocrine glands release certain chemicals called hormones. Hormones (so-called "chemical messengers") produced by endocrine glands enter the capillaries (and lymph vessels) of the blood circulatory system. They travel through the bloodstream to specific "receptors" in target organs or systems where they can trigger their biological effects.
Some examples of hormones released by the endocrine system are:
The endocrine system is important because it coordinates and regulates many essential body functions such as:
The endocrine system controls many functions of the body, both immediate reactions and life-long functions. The hormones stabilize or balance functions in the normal body. In turn, the levels of hormones produced in the body are influenced:
Any disruption to this balance can cause changes in the reproduction, development, growth, or behaviour that can affect an animal or human or their offspring or children.
When there is interference with the normal communication between the "messenger" hormone and the cell receptors:
Understanding the role of the endocrine system (and the hormones that they produce) in the normal functioning of the body gives us some indication of the types of problems that might occur when endocrine function is disrupted. Many of these organs influence each other's activities, producing very complex interactions and making the effect of the disruptors exceedingly difficult to identify or predict.
When the endocrine system is exposed to some substances, it may interact with them. These substances are referred to as “endocrine active substances”. When the interaction between the substance and endocrine system leads to “adverse effects”, the substances are called “endocrine disruptors”.
Endocrine disrupting substances interfere with the normal function of endocrine systems in a number of ways:
If a substance stimulates or inhibits the endocrine system, then increased or decreased amounts of hormone may be produced. In addition, small amounts of different endocrine disruptor chemicals may have a cumulative effect. In some cases, the by-products of the chemicals may have a greater harmful effect than the parent chemical.
The number of substances believed to act as endocrine disruptors is wide and varied. They can benatural and synthetic materials. For example:
Many plants and animals produce substances that can have endocrine effects. Some of the substances are toxic but certain effects have proven beneficial in some circumstances. For example, some "endocrine disruptors" have been used to:
Endocrine disruptors are found also in synthetic chemicals used as industrial solvents, lubricants, and their byproducts.
Synthetic chemicals suspected as endocrine disruptors may reach humans and animals in a variety of ways. Some, such as pesticides, are released intentionally. Others are by-products of industrial processes and waste disposal - these include dioxins and PCBs - or are discharged from industrial or municipal treatment systems (See Table below)
The table lists examples of sources, examples of the type of substances with endocrine-disrupting properties that could be present at the source, and the chemical group or type of product these substances belong to.
|Sources of potential endocrine disrupters||Chemical group or type of product the substances belong to:||Examples of Substances with potential endocrine disrupting properties that could be present to at the Source|
|Incineration, landfill||Polychlorinated Compounds (from industrial production or by-products of mostly banned substances)||Polychlorinated dioxins, polychlorinated biphenyls|
|Agricultural runoff / Atmospheric transport||Organochlorine Pesticides (found in insecticides, many now phased out)||DDT, dieldrin, lindane|
|Agricultural runoff||Pesticides currently in use||Atrazine, trifluralin, permethrin|
|Harbours||Organotins (found in antifoulants used to paint the hulls of ships)||Tributyltin|
|Industrial and municipal effluents||Alkylphenols (Surfactants - certain kinds of detergents used for removing oil - and their metabolites)||Nonylphenol|
|Industrial effluent||Phthalates (found in placticizers)||Dibutyl phthalate, butylbenzyl phthalate|
|Municipal effluent |
|Natural Hormones (Produced naturally by animals); synthetic steroids (found in contraceptives)||Estradiol, estrone, and testosterone; ethynyl estradiol|
|Pulp mill effluents||Phytoestrogens (found in plant material)||Isoflavones, lignans, coumestans|
|Consumer products||Cosmetics, personal care products, cleaners, plastics||Parabens, phthalates, glycol ethers, fragrances, cyclosiloxanes, bisphenol A (BPA)|
(Source: Endocrine Disruptors Update, 2000, Environment Canada, and Endocrine Disruptors and Asthma-Associated Chemicals in Consumer Products. R.E. Dodson, M. Nishioka, L.J. Standley, et all. (2012). « Environment Health Perspective ». Vol. 120, No. 7, pages 935-943)
The most prominent and well documented health concerns from exposure to endocrine disruptors are reproductive and developmental effects. Some of the disorders that have been seen in animal studies include:
No WHMIS health hazard class directly identifies endocrine disruptors. Endocrine disruptors that cause other health effects may be identified by the appropriate WHMIS health hazard classes.
If workers can be exposed to endocrine-disrupting substances, the employer should:
Before you handle endocrine-disrupting substances, make sure you have received:
Only use a hazardous product after you have been trained. Make sure you understand how to use, handle, and store it safely. If you have not been trained, let your supervisor know. If you don’t understand the instructions or need help, ask your supervisor.