17 February 2008
Hormones Gone Wild
By Rusty Rockets
The human endocrine system is an important physiological network comprised of glands and blood vessels that produce and transport chemical messengers known as hormones around the body. These hormones are essential to the regulation of tissue function, growth and development, metabolism, and mood. Knowing this, it's easy to appreciate the potential destructive effect on the body should this crucial system ever be disrupted. This is why scientists are becoming increasingly worried about the chemicals known as "endocrine disruptors" that are found in everyday hygiene and cosmetic products.
It's not the presence of endocrine disrupting substances (EDS) in our shampoos, toothpastes, anti-bacterial soaps, beauty products, and, subsequently, our waterways that is causing controversy. Rather, it is whether or not the levels of EDS we are exposed to are high enough to have any effect.
There have been studies that have identified adverse biological effects from EDS in animals, but whether this data can be transferred to humans has been hotly debated by the science community. Who is right, and are we exposing ourselves to any number of serious health problems just for the sake of a glowing smile and bacteria-free hands?
EDS are exogenous (from outside the body) substances that not only act just like hormones found in the endocrine system (endogenous hormones), but also disrupt their normal physiologic function. So what are some of the EDS under suspicion? The National Institute of Environmental Health Sciences (NIEHS) lists some chemicals that include a number of the usual suspects. Known endocrine disruptors include diethylstilbesterol (the drug DES), dioxin and dioxin like compounds, PCBs and DDT. Based on animal studies, some other suspect chemicals include Bisphenol A and various pesticides and plasticizers.
Many scientists claim that even low-level exposure is enough to wreak havoc on any number of hormone-related processes by interacting directly with our hormone receptors; which can lead to cancer, reproductive failure and developmental anomalies. They justify their claims by drawing attention to the fact that endogenous hormones naturally occur at quite small concentrations in the body, so it follows that only small concentrations of exogenous endocrine disruptors are needed to be harmful. If their theory is correct, it makes hormonally active endocrine disruptors much more potent than other types of toxic substances.
One particular antibacterial compound called triclocarban (also known as TCC or 3,4,4'-trichlorocarbanilide), used to enhance the efficiency of bath soaps and other products, has been under close scrutiny by researchers for a number of years now. A University of California Davis study released in December of 2007 showed that soap containing triclocarban altered the hormonal activity in rats and in human cells in the laboratory.
In the UC Davis study, the researchers identified a mechanism by which the EDS interact with endogenous hormones in ways not previously reported. They discovered that triclocarban increases gene expression normally regulated by testosterone, which led to abnormal prostate gland enlargement in rats that were fed triclocarban. This is an important new finding, as EDS were previously thought to only decrease, or block, hormonal activity.
Triclocarban and other hormonally active substances are worryingly ubiquitous; found in a myriad of everyday household products such as body washes, bar soaps, wipes, cleansing lotions and detergents. The NIEHS reports that as well as personal hygiene products, EDS can also be found in plastic bottles, metal food cans, detergents, flame retardants, floor coverings, food, toys, cosmetics and household pesticides.
One author of the UC Davis study speculates that regular exposure to EDS may even explain some reproductive problems. "This finding may eventually lead to an explanation for some rises in some previously described reproductive problems that have been difficult to understand," said Bill Lasley, a UC Davis expert on reproductive toxicology and professor emeritus of veterinary medicine.
Lasley states, however, that more testing on EDS is required before links can be made with any certainty, adding that the study should not be used as a guide on whether or not to use products containing triclocarban. "Our mothers taught us to wash our hands well before the advent of antimicrobial soaps, and that practice alone prevents the spread of disease."
There are other common substances used in antibacterial soaps that not only cause problems for the user, but also for the environment. Triclosan is a very common disinfectant used in antibacterial soaps that has been shown to produce a dioxin when exposed to sunlight. While the resultant dioxin is claimed to be of a very low-level, benign form, researchers argue that it nonetheless gets into wastewater that is eventually treated with chlorine. Once treated with chlorine the triclosan derived dioxin transforms into a much more toxic species of dioxin.
"Repeated exposure to chlorine, perhaps in water treatment facilities, could chlorinate triclosan. After chlorinated triclosan is discharged from the facility, sunlight could convert it into more toxic dioxins. Such a process could be a source of highly toxic dioxin in the environment," says Kristopher McNeill, an assistant professor of chemistry at University of Minnesota. "The disappearance of a pollutant such as triclosan doesn't necessarily mean an environmental threat has been removed," added co-researcher William Arnold. "It may just have been converted into another threat."
The fact that such complex and long-term chain reactions can ultimately result in dioxin - a powerful endocrine disrupting substance - appearing in the environment shows how difficult it is to keep track of these chameleon-like chemicals, let alone what specific effects they may have on humans.
The difficulties involved in demonstrating endocrine disruption in humans from specific products mean that it is unlikely we will get government warnings on bars of soap anytime soon. But the science behind EDS research is sound, and nobody seems to doubt the harmful effects that high levels of EDS can have on humans. Whether health authorities continue washing their hands of the problem remains to be seen.
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