The human body is immensely complex, and our knowledge and awareness of its complexity continues to grow.

One of the most disquieting discoveries in recent years concerns the possible roles of environmental chemicals on endocrine systems. Endocrine systems are present not only in humans but in "higher" animals such as birds, fish, and mammals. Endocrine systems coordinate and regulate many important body functions such as growth and maturation, behaviour, reproduction and embryo development. They do this by making and releasing hormones which act as "chemical messengers." Certain tissues in the body have very specific receptors for the hormones. By interacting with these receptors, the hormones trigger responses.

Several organs within the human body make up the endocrine system. These organs include the ovary, testes, thyroid and adrenal glands, pancreas, pituitary, as well as the placenta, liver, kidneys and cells of the gastrointestinal tract. Understanding the role of these organs in the normal functioning of the body gives us some indication of the types of problems that might occur when proper endocrine function is disrupted. Moreover, many of these organs influence each other’s activities, producing very complex interactions and making the effect of disruptors exceedingly difficult to identify or predict.

Among the hormones ("chemical messengers") operating within the endocrine system are estrogen (a female sex hormone produced by the ovaries); thyroid hormone (influencing the function of virtually every cell in the body); and ACTH (produced by the pituitary gland to influence the release of adrenalin from the adrenal gland).

Endocrine systems can be affected by certain substances outside of the body, both naturally-occurring and artificial. By interfering with the normal communication between the messenger and the cell receptors, the chemical message is misinterpreted, generating abnormal response(s) in the body.

Substances can disrupt the normal function of endocrine systems in three different ways.

One, they can mimic a natural hormone, and lock onto a receptor within the cell. The disruptor may give a signal stronger than the natural hormone or at the wrong time. In some cases even very small amounts of a disruptor may have a detectable effect.

Two, they can bind to a receptor within a cell, and prevent the correct hormone from binding. The normal signal then fails to occur and the body fails to respond properly.

Three, disruptors can interfere with or block the way natural hormones and receptors are made or controlled. This interference or blockage may occur only if relatively large doses of the substance are present.

Wide and varied distribution of suspected substances

The number of substances believed to act as endocrine disruptors is wide and varied, including both natural and synthetic materials. Concern arises because potential endocrine disruptors may be present in the environment, unrecognized but possibly able to cause effects at low concentrations.

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 control fertility and to treat cancer, psychiatric disorders and other medical conditions. Natural substances, such as sex hormones or phytoestrogens, can become concentrated in industrial, agricultural and municipal wastes. Exposure to these wastes may produce reactions in humans, wildlife, fish or birds.

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 1)

SOURCE: ENVIRONMENT CANADA – "Endocrine Disrupting Substances in the Environment", 1999

Canada is considered a world leader in studying the distribution and effects of endocrine disruptors on humans and wildlife. While much research has been focused on persistent substances, such as PCB’s and DDT, a shift has been made towards substances not so highly persistent but widespread in the environment. These include materials found in industrial and municipal effluents, agricultural runoff, natural estrogens in plants, and specific chemicals such as alkylphenols, tributyltin and pesticide ingredients.

A reliable source for chemical data and regulatory information

ChemAdvisor is a database of over 100,000 chemicals, which includes current regulatory and advisory data and covers key health and safety and environmental jurisdictions. Chemical regulatory information can be accessed by chemical name, synonym, and CAS number in seconds. The program includes options for flexible viewing, printing or saving data according to your needs. Exceptionally user-friendly, ChemAdvisor provides on-screen help and pull-down menus to guide you through search and retrieval functions.

Potential endocrine disruptor substances identified by organizations such as the U.S. Environmental Protection Agency and Japan’s Environment Agency are identified in the The Chemical Advisor® CD-ROM.

For more information on The Chemical Advisor® and endocrine disruptor research and findings, contact the CCOHS Inquiries Service or Client Services.

Inquiries: 1-800-668-4284 (Canada), 905-572-4400 or via e-mail at: inquiries@ccohs.ca.

Client Services: 1-800-668-4284 (Canada and US), 905-570-8094 or via e-mail at: clientservices@ccohs.ca