Humans endocrine disruptor effects

Toxicology Bisphenol A can be released during thermal decomposition of epoxides above 250 °C, which can cause photosensitisation of the skin. Bisphenol A is not genotoxic in vivo, however, weak oestrogenic effects are observed in vitro. Some endocrine disruptor effects in animals and human cancer cells can occur at low levels (2-5 ppb). It has been claimed that these effects lead to health problems, mainly in men, of a lowered sperm count and infertile sperm. 

The broad spectrum of chemical classes shown to have endocrine disruptor effects, and a VcU iety of excunple chemiccds, cire presented in table 11.1. Affected species and specific effects noted for several specific chemicals are shown in table 11.2. The unique trciit of endocrine disruption is that many of these effects can occur at concentrations below those previously assumed to pose no risk to human health or the environment. 

Recently, attention has focused on the potential hazardous effects of certain chemicals on the endocrine system because of the abihty of these chemicals to mimic or block endogenous hormones, or otherwise interfere with the normal function of the endocrine system. Chemicals with this type of activity are most commonly referred to as endocrine disruptors. Some scientists believe that chemicals with the ability to disrupt the endocrine system are a potential threat to the health of humans, aquatic animals, and wildlife. Others believe that endocrine disrupting chemicals do not pose a significant health risk, particularly in light of the fact that hormone mimics exist in the natural environment. Examples of natural hormone mimics are the isoflavinoid phytoestrogens (Adlercreutz 1995 Livingston 1978 Mayr et al. 1992). 

Depending upon the circumstance and desired effects, endocrine-disrupting chemicals can be either good or bad. The endocrine system is a finely balanced system responsible for fertility and many of the feminine and masculine traits we are all familiar with. Endocrine disruptors are used by millions of women in the form of the pill to control fertility. Chemicals in birth control pills subtly manipulate the endocrine system to reduce fertility. Unfortunately, we now know that many chemicals are capable of influencing the endocrine systems. When these chemicals, such as DDT and TCDD, are released into the environment, they reduce the fertility of wildlife. Exposure to endocrine disruptors is linked to decreased fertility in shellfish, fish, birds, and mammals. Endocrine disruptors such as nonylphenol have been shown to feminize male fish, interfering with reproduction. Some studies have also linked exposure to endocrine disruptors to decreases in human male sperm count. Ironically, urinary metabolites of the birth control pill as well as the female hormone estrogen pass through waste treatment plants and are released into the aquatic environment, where even small concentrations cause feminization of male fish. 

Careful research has weakened assertions that environmental chemicals are endocrine disruptors and major causes of cancer. Environmental organizations still tout the risks to raise the public s awareness—they say—and to solicit contributions. Government officials, in charge of programs to investigate the risks, continue to provide funds to scientists who look for evidence to support the assertions and to programs that test chemicals for effects that have little, at best, and more likely, no, relationship to human health. Environmental organizations publicity and gov-... 

Most POPs are readily absorbed (via the digestive system and inhalation) and accumulate in fatty tissue, including brain and adipose tissue and human milk. These substances can induce neurological effects and cause altered functioning of the nervous system as well as acting as endocrine disruptors. 

Administration of 2,3,7,8-TCDD to animals results in a wide range of endocrine responses which are not only species-dependent, but also exhibit variability within species. Endocrine effects observed in humans have not been limited to thyroid effects and diabetes alterations in levels of reproductive hormones, as summarized in the sections on reproductive effects have also been observed. The wide array of endocrine effects induced by CDDs and structurally-related chemicals has triggered increased interest within the scientific community and the term endocrine disruptors is currently being used to describe some members of this class of chemicals. The available information suggests that CDDs may cause adverse endocrine effects in humans. 

Fluman impact assessments of the effects of chemical exposures through food, personal care products, drinking water, or air have traditionally focused on single substances. Yet, detrimental human health effects due to individual environmental pollutants have normally not been demonstrated at exposure levels encountered in industrialized societies. While it may be artificial to reduce human impact assessments to single chemicals, there are indications that combinations of chemicals may play a cumulative role. Recent findings from the area of endocrine disruptors may illustrate the point. 

REACH introduces the concept of adequate control in EU chemical law. Traditionally, the term adequate control has been used to refer to good practice in the workplace. REACH now redefines adequate control in the form of risk management measures detailed in an exposure scenario necessary for the control of hazardous properties. Through a set of systematic procedures, risk management measures must be selected to reduce exposure below which adverse effects to human health or the environment are likely to occur (i.e., a DNEL, DMEL or PNEC). There is debate as to whether a concept of a safe level of exposure reduction, similar to adequate control, can apply to non-threshold carcinogens and mutagens, endocrine disruptors, persistent, bioaccumulative and toxic (PBT) or VPVB substances (e.g., [270]). Industry may need to demonstrate that exposure to these substances is always avoided or minimised, as specified in Annex I of the REACH Regulation. 

Endocrine disruptors are chemicals that cause adverse health effects in an animal or its offspring due to changes in hormone function. In recent years some scientists have concluded from a number of coincidental observations that certain chemicals in the environment may be interfering with the hormonal systems of animals and possibly of humans. These endocrine disruptors coidd be responsible for a range of dysfunctions that have been observed in the reproductive systems of humans and other animals. The effects in wildhfe have been well documented and can be reproduced experimentally. The human effects are more difficult to... 

For humans, except for cases where high levels of exposure have occurred (for example, in the therapeutic use of diethylstilboestrol), the data is inconsistent and inconclusive. Information on levels of exposure is lacking and there is no firm evidence for a Hnk between low level exposure and adverse health outcomes in the human population. For all the adverse health outcomes the evidence of association with environmental exposure to endocrine disruptors is weak (except in the case of minor effects on thyroid hormones, where evidence is moderate). In some cases, such as changes in sperm count, a possible connection is scientifically plausible. Further evidence is needed, and especially evidence that Hnks actual exposure levels in humans to effects. ... 

Classified as an endocrine disruptor and may cause adverse health effects in humans. 

Recently, the hazardous effects of endocrine disruptors (environmental hormones) such as bisphenol A and nonylphenol on the human body have been reported, and led to the initiation of many studies concerning the detection and structural determination of these compounds present in tiny amounts [57]. As one of the QSAR analyses of environmental hormones, the relationship between their biological activity and chemical hardness has been reported [16]. By applying these analytical methods, the molecular toxicity and estrogen-like activity of environmental hormones have been found... 

The effects of EDCs were first discovered in wildlife in the 1970s. It was found that extremely low concentration levels of these can have powerful deleterious effects on the reproduction of wildlife. Human effects were not studied until much later because most EDCs are neither mutagenic nor acutely toxic at the ambient concentrations found to have endocrine disruption effects on wildlife. It was also believed that effects on birds and turtles were not necessarily indicators of human toxicity. This, however, turned out to be exactly the case. Though toxic effects of chemicals are not always similar for different species of animals, they are just that for endocrine disruptors. The effects of EDCs on birds and amphibians are exactly analogous to those on humans. 

Not all scientists agree with this argument, though. There is evidence that some xenobiotic substances have clearly been identified as interfering with aiumal endocrine (hormonal) systems. These molecules are called endocrine disruptors . The effect in humans is more controversial and poorly imderstood. An internet search of this topic will yield many websites with opinions and facts in dispute. 

The effect of these compounds on human health has been a major cause of concern. Toxicity to humans depends on exact structure, but exposure is ubiquitous and involves a mixture of compounds, from fossil fuel and natural and anthropogenic burning and from food, mainly grilled or barbecued meat. In the broader environment, PAHs are endocrine disruptors and bind to the aryl hydrocarbon receptor. They have been shown to depress immune function in some wildlife. They may be responsible for reproductive disorders in aquatic organisms, especially in shellfish and sediment dwellers. 

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