10 April 2014 Bioscientifica Ltd
Human and rat testes respond differently to endocrine disrupting chemicals such as BPA in two thirds of all cases, according to a recent review. As human safety levels are extrapolated from rodent data, the study could lead to a re-evaluation of the acceptable daily intake for many endocrine disruptors. The review is published in a special April issue of the journal Reproduction dedicated to endocrine disruptors.
Endocrine disruptors (EDs) are compounds that interfere with animal hormone (or endocrine) systems in various ways. Sometimes, this can lead to developmental problems, including those of the reproductive system. Over the past four decades, human sperm counts have been markedly decreasing and the rate of testicular cancer rates has risen. Meanwhile, the occurance of undescended testicles and abnormally developed male urethras are also thought to be increasing. Evidence suggests that these male reproductive disorders are at least partially due to the effects of endocrine disrupting chemicals which are becoming increasingly concentrated and prevalent in the environment and that these EDs act on the testis during fetal development.
Suspected EDs include pesticides, flame retardants and chemicals found in plastic goods such as bisphenol A (BPA) – one of a group called phthalates.. Currently, the human health risk from exposure to a given endocrine disruptor is normally assessed using a rodent model. The observed safety threshold is then reduced by a factor of 100 to calculate safety levels for humans.
In a recent review, researchers from the French Institute of Health and Medical Research (INSERM), Atomic Energy Commission (CEA) and University of Paris-Diderot compared the effects of six potential EDs on the function of rat, mouse and human fetal testis at comparable stages of their development. They simulated normal testicular development in each of these species using a novel in vitro culture system called FeTA. They found that the response to these six potential EDs was similar in humans and rodents for only one third of analyses. Human testes were more than 100 times more susceptible to some compounds, including BPA, compared to in rodents. For other compounds different effects were seen between species. More recent studies have confirmed the findings using a different experimental approach.
Professor René Habert, who led the study, said: “Our work suggests that for some compounds, human and rat cells show different susceptibilities. For others, there appear to be fundamental differences in the way these compounds act in humans and rodents. We think that these differences between species are even more pronounced for reproductive functions. This means we really have to question how relevant animal data is to assessing risk in humans.”
The FeTA system is an extremely reliable system for studying testicular cell development across species. It is more efficient than in vivo methods and also avoids problems of cross-contamination. “Our work highlights the fact that we need to test the effects of potential endocrine disrupting chemicals in both rat and human cells to be able to accurately predict the risk,” said Professor Habert. “The FeTA system is a great tool for comparing effects of endocrine disruptors on testis development in different species. However, the limitation is that we cannot use it to study long-term effects, as testis development can only be maintained for up to ten days, depending on the species.”
The next stage for the research is to assess the risk of BPA substitutes, including BPS and BPF, in both human and rodents. The group is also investigating how these compounds interact with rodent and human cells at the molecular level to understand how differences between species arise. “We need to develop specific tools to study chemical toxicity in human reproductive cells; this will allow us to accurately assess safety thresholds for different compounds, and re-evaluate the acceptible daily intake levels to protect human health for some of them” said Professor Habert.
This article by Mike Roussell gives one pause to consider the bigger picture when it comes to what we put into our mouths. After all, that’s where the dynamic – eating, food, nutrition, health – begins.
Looking at what’s in our food can quickly become an exercise in getting depressed or getting invigorated. Awareness makes the difference. These six chemicals are a good starting place if you’re not sure about what’s in your food.
by Mike Roussell, SHAPE Diet Doctor, phD
These six chemicals may be causing weight gain. With obesity rates continuing to climb year after year without epic changes in the amount of calories we are eating, many wonder what else could be a contributing to this growing epidemic. Sedentary lifestyle? Definitely. Environmental toxins? Possibly.
Unfortunately the world we live in is chock-full of chemicals and compounds that can negatively impact our hormones. These six in particular could be helping to pad your waistline and while you may not be able to completely avoid them, there are easy ways to limit your contact.
1. Atrazine: According to the Environmental Protection Agency, atrazine is one of the most widely used herbicides in the United States. It’s commonly used on corn, sugarcane, sorghum, and in some areas on grass lawns. Atrazine disrupts normal cellular mitochondrial function and has been shown to cause insulin resistance in animals.
The EPA last thoroughly examined the health effects of atrazine in 2003, deeming it safe, but since that time 150 new studies have been published, in addition to documentation about the presence of atrazine in drinking water, prompting the agency to actively monitor our water supply. You can minimize your exposure to atrazine by buying organic produce, particularly corn.
2. Bisphenol-A (BPA): Traditionally used worldwide in plastics used for food and drink storage, BPA has long been known to mimic estrogen and has been associated with impaired reproductive function, but it’s also an obesogen. A 2012 study published in the International Journal of Obesity found that BPA is responsible for starting a biochemical cascade within fat cells that increases inflammation and promotes fat-cell growth. Anytime you purchase canned goods or food in plastic containers (including bottled water), be sure the product is labeled as “BPA free.”
3. Mercury: Another reason to avoid high-fructose corn syrup (as if you need one): The processing used to make this sweetener leaves small amounts of mercury in the syrup. That may seem inconsequential, but at the rate Americans consume high fructose corn syrup, the added mercury could be a problem. Even if you eliminate HFCS from your diet, canned tuna-a staple in many healthy lunches-can also contain mercury. As long as you stick to no more than three cans of tuna a week, you should be fine. It’s also a good idea to avoid chunk white tuna, which has more than double the mercury of chunk light tuna.
4. Triclosan: Hand sanitizers, soaps, and toothpastes often add triclosan for its antibacterial properties. However, animal studies have shown that this chemical negatively impacts thyroid function. The FDA is currently reviewing all available safety and effectiveness data on triclosan, including information concerning bacterial resistance and endocrine disruption. For now, the FDA considers the chemical safe, but further research needs to be done to determine if and at what dosage triclosan decreases thyroid hormone levels in humans. If you would rather take action now, check the labels of your hand sanitizer, soaps, and toothpaste to be sure triclosan isn’t listed.
5. Phthalates: These chemicals are added to plastics to in order to improve their durability, flexibility, and transparency and are also found in pacifiers, children’s toys, and personal care products such as soap, shampoo, hair spray, and nail polish. Korean researchers found higher levels of phthalates in obese children than in healthy-weight kids, with those levels correlating to both BMI and body mass. Scientists at the Children’s Environmental Health Center at Mount Sinai Medical Center in New York found a similar relationship between phthalate levels and weight in young girls. In addition to buying phthalate-free baby products and toys (Evenflo, Gerber, and Lego have all said they will stop using phthalates), you can search the Environmental Working Group’s database to check if your bath and beauty products contain any toxins.
6. Tributyltin: While tributyltin is used in an anti-fungal compound on food crops, its primary use is in paints and stains used on boats where it serves to prevent bacterial growth. Animal studies have shown that exposure to this chemical can accelerate the growth of fat cells in newborns. Unfortunately, tributyltin has been found in household dust, making our exposure to it more widespread than initially thought.
Our regulatory agencies all allow these six chemicals to be widely used. This is in spite of any research that shows there are or may be detrimental effects on humans. That opens a whole series of questions and debates that mostly seem to be designed around how to keep these chemicals legal to use instead of what makes Jack and Jill healthy.
Remember when they discovered perchlorate had contaminated drinking water? Perchlorate is a salt used in rocket fuel and explosives and is known to disrupt thyroid function. When plumes of this toxin were traced back to rocket fuel manufacturing sites that dumped the stuff on the ground (cutting edge environmental practice in the 50’s and 60’s), the debate quickly became how much is allowable in our drinking water.
Thyroid damage be damned. It’s rocket fuel in our drinking water. It’s still about how much is ok for us to drink. It’s not rocket science. It’s mos assuredly not about how to clean it up. We’re the guinea pigs here. Anyone else find this disturbing?
Playing the ‘Is It Healthy?” Game is about paying attention to what you put into your mouth.