deechee
04-18-2008, 10:30 AM
The majority of you seem to have the ability to question politics and how they are reported in the media (moguls) so why not question science and interpretation of those results? How often are poll results skewed? How often has someone told you something you know is not true?
I think a number of you should read this article: (also included below)
http://www.elfe.net/e/Story.asp?SectionID=2&ContentID=1043&qReturnPg=/e/default.asp&s=090JAA
Its written by Joe Schwarcz, a well-respected local chemist who teaches at McGill University and runs a series of programs for children and adults.
Science is around our lives everywhere. Do you think the meat you buy at the grocery would last as long as does without the plastic shrink wrap? Do you realize most of your fruits and vegetables have some kind of genetic engineering/cross-breeding? When was the last time you ate an heirloom tomato?
I doubt I'll ever use a Sigg bottle while riding. I'm not able to unsrew the cap everytime I want to drink, and I can't squeeze the bottle? I have to tilt it all the way up to drink? And tell me, how clean are you getting that bottle? With the wide mouth plastic bottles I can stick in brushes and really scrub it. Are you sure your opaque bottle is clean inside? Is that pipe brush really getting through to the bottom? I like verifying my bottles are fungus free before filling them.
I'm copy-pasting from my cache:
Bisphenol A - 'A little learning is a dangerous thing'
Saturday, February 16, 2008
What did Alexander Pope say? "A little learning is a dangerous thing; Drink deep, or taste not the Pierian spring; There shallow thoughts intoxicate the brain; And drinking largely sobers us again." But the poet never had to think about drinking spring water out of a polycarbonate bottle, did he?
Bisphenol A (BPA), a chemical that can leach out of polycarbonate bottles, is clearly the "toxin du jour." Environmental organizations label it as a clear threat to our health and some politicians have even begun to clamour to ban any substance that can release BPA.
The current media focus on BPA was stimulated by a couple of studies that measured the amount of this chemical that leached into water stored in polycarbonate bottles. Such studies are motivated by one of the well-established chemical characteristics of BPA, namely that it has hormone-like effects. And since hormones can be physiologically active at very small doses, the potential effects of BPA certainly merit investigation, especially given that some hormone-driven cancers appear to be increasing.
Of course, before we attempt to evaluate the meaning of the amount of BPA leaching out of bottles, we have to have some idea of the dose at which the chemical presents a hazard. Although there is no universal agreement on what is a safe intake, there is a consensus among regulatory agencies that rodents treated with five milligrams of BPA per kilogram of body weight do not experience adverse effects. This is referred to as the "no observed adverse effect level," or NOAEL. Building in a safety factor of 100, these agencies have proposed a Tolerable Daily Intake (TDI) for humans of 0.05 milligrams per kg .
Let's get back to the bottles, and consider worst case scenarios. We'll focus on baby bottles, because if BPA presents a risk, it is expected to be most significant during the developmental stage. In the most recent study, the maximum amount of BPA that leached into water from a polycarbonate bottle was eight nanograms per millilitre. Let's assume a baby were to drink a litre of this water. One milligram is a million nanograms, so the total intake would be 0.008 milligrams. If the baby weighs 5 kg (11 pounds), we have an intake of 0.0016 mg per kg of body weight. This is about one-thirtieth the TDI and one three-thousandth the "no observable adverse effect level," in test animals.
That's theory. What about measuring how much BPA we are actually exposed to? That's been done. The Centres for Disease Control in the U.S. sampled urine from more than 2,000 people age 6 to 85 and found an average of about 2.7 nanograms per mL. Since bisphenol A does not accumulate in the body, the urinary output can be used to estimate the amount taken in through food and water. This calculates to 50 nanograms per kg of body weight. And how does that compare with the TDI? It is 1,000 times less. And 100,000 times less than the dose that causes no effect in test animals. Some researchers argue that the calculation of oral intake based on urinary output is flawed and that if one goes by studies in animals the value should be at least 100 times greater. Even if we accept this argument, we are still looking at an intake that is a thousand times less than the dose that causes no effect in test animals. So there seems to be a significant safety factor here, even if one argues about the exact value of the NOAEL.
Since the human is not a giant rat, the possibility exists that we are more sensitive to hormone disrupting chemicals than rodents. But if that is the case, we have a lot more to worry about than just BPA. Remember the joke about the drunk who was walking back and forth below a street lamp? What did you lose, he was asked? My keys, came the reply. Did you drop them here? No, he answered, but this is the only place where there is light!
Right now, the light is being cast on bisphenol A, while numerous hormone-like substances lurk in the arkness.
Take lavender-scented soaps and lotions, for example. These have been linked with breast growth in young boys. It turns out lavender oil activates estrogen regulating genes in human breast cells. Alfalfa sprout extracts display increased breast cancer cell proliferation above levels seen with estradiol, an estrogen. Soybeans contain natural estrogenic compounds, and so does milk. Milk represents a far greater estrogenic exposure than we experience from BPA. Our average daily intake of estrogens through milk is about 370 nanograms, 20 times greater than the amount of BPA found in a litre of water consumed from a polycarbonate baby bottle. Nobody suggests banning milk even though it contains a good dose of estrogenic compounds. Neither should they.
That's not all. Nonylphenol, an ingredient in numerous detergents, is estrogenic. It ends up in sewage, along with natural estrogens and birth control pill remnants excreted by women. Sewage treatment plants do not remove these substances and they can end up in surface water as well as in ground water when sewage sludge is spread on fields as fertilizer.
We are awash in a sea of both natural and synthetic hormone disrupting substances and it is unrealistic to accuse a specific one of being the devil. This does not mean we should be cavalier about hormone-like substances in the environment.
Even though there is no evidence that at the levels encountered, BPA is a risk to humans, we can't rule out the possibility that babies may not excrete BPA as efficiently as adults, or that the chemical might have a synergistic effect when combined with other endocrine disrupting substances. Baby bottles made of glass or other plastics are available, and it seems a good idea to search for viable alternatives to the epoxy lining in canned foods. But panic over drinking from polycarbonate bottles is unwarranted, and talk of banning polycarbonate plastics is naive.
Joe Schwarcz is director of McGill University's Office for Science and Society
(www.OSS.McGill.ca).
He can be heard every Sunday from 3-4 p.m. on CJAD.
joe.schwarcz@mcgill.ca
© The Gazette (Montreal) 2008
Copyright © 2008 CanWest Interactive, a division of CanWest MediaWorks Publications, Inc.. All rights reserved.
I think a number of you should read this article: (also included below)
http://www.elfe.net/e/Story.asp?SectionID=2&ContentID=1043&qReturnPg=/e/default.asp&s=090JAA
Its written by Joe Schwarcz, a well-respected local chemist who teaches at McGill University and runs a series of programs for children and adults.
Science is around our lives everywhere. Do you think the meat you buy at the grocery would last as long as does without the plastic shrink wrap? Do you realize most of your fruits and vegetables have some kind of genetic engineering/cross-breeding? When was the last time you ate an heirloom tomato?
I doubt I'll ever use a Sigg bottle while riding. I'm not able to unsrew the cap everytime I want to drink, and I can't squeeze the bottle? I have to tilt it all the way up to drink? And tell me, how clean are you getting that bottle? With the wide mouth plastic bottles I can stick in brushes and really scrub it. Are you sure your opaque bottle is clean inside? Is that pipe brush really getting through to the bottom? I like verifying my bottles are fungus free before filling them.
I'm copy-pasting from my cache:
Bisphenol A - 'A little learning is a dangerous thing'
Saturday, February 16, 2008
What did Alexander Pope say? "A little learning is a dangerous thing; Drink deep, or taste not the Pierian spring; There shallow thoughts intoxicate the brain; And drinking largely sobers us again." But the poet never had to think about drinking spring water out of a polycarbonate bottle, did he?
Bisphenol A (BPA), a chemical that can leach out of polycarbonate bottles, is clearly the "toxin du jour." Environmental organizations label it as a clear threat to our health and some politicians have even begun to clamour to ban any substance that can release BPA.
The current media focus on BPA was stimulated by a couple of studies that measured the amount of this chemical that leached into water stored in polycarbonate bottles. Such studies are motivated by one of the well-established chemical characteristics of BPA, namely that it has hormone-like effects. And since hormones can be physiologically active at very small doses, the potential effects of BPA certainly merit investigation, especially given that some hormone-driven cancers appear to be increasing.
Of course, before we attempt to evaluate the meaning of the amount of BPA leaching out of bottles, we have to have some idea of the dose at which the chemical presents a hazard. Although there is no universal agreement on what is a safe intake, there is a consensus among regulatory agencies that rodents treated with five milligrams of BPA per kilogram of body weight do not experience adverse effects. This is referred to as the "no observed adverse effect level," or NOAEL. Building in a safety factor of 100, these agencies have proposed a Tolerable Daily Intake (TDI) for humans of 0.05 milligrams per kg .
Let's get back to the bottles, and consider worst case scenarios. We'll focus on baby bottles, because if BPA presents a risk, it is expected to be most significant during the developmental stage. In the most recent study, the maximum amount of BPA that leached into water from a polycarbonate bottle was eight nanograms per millilitre. Let's assume a baby were to drink a litre of this water. One milligram is a million nanograms, so the total intake would be 0.008 milligrams. If the baby weighs 5 kg (11 pounds), we have an intake of 0.0016 mg per kg of body weight. This is about one-thirtieth the TDI and one three-thousandth the "no observable adverse effect level," in test animals.
That's theory. What about measuring how much BPA we are actually exposed to? That's been done. The Centres for Disease Control in the U.S. sampled urine from more than 2,000 people age 6 to 85 and found an average of about 2.7 nanograms per mL. Since bisphenol A does not accumulate in the body, the urinary output can be used to estimate the amount taken in through food and water. This calculates to 50 nanograms per kg of body weight. And how does that compare with the TDI? It is 1,000 times less. And 100,000 times less than the dose that causes no effect in test animals. Some researchers argue that the calculation of oral intake based on urinary output is flawed and that if one goes by studies in animals the value should be at least 100 times greater. Even if we accept this argument, we are still looking at an intake that is a thousand times less than the dose that causes no effect in test animals. So there seems to be a significant safety factor here, even if one argues about the exact value of the NOAEL.
Since the human is not a giant rat, the possibility exists that we are more sensitive to hormone disrupting chemicals than rodents. But if that is the case, we have a lot more to worry about than just BPA. Remember the joke about the drunk who was walking back and forth below a street lamp? What did you lose, he was asked? My keys, came the reply. Did you drop them here? No, he answered, but this is the only place where there is light!
Right now, the light is being cast on bisphenol A, while numerous hormone-like substances lurk in the arkness.
Take lavender-scented soaps and lotions, for example. These have been linked with breast growth in young boys. It turns out lavender oil activates estrogen regulating genes in human breast cells. Alfalfa sprout extracts display increased breast cancer cell proliferation above levels seen with estradiol, an estrogen. Soybeans contain natural estrogenic compounds, and so does milk. Milk represents a far greater estrogenic exposure than we experience from BPA. Our average daily intake of estrogens through milk is about 370 nanograms, 20 times greater than the amount of BPA found in a litre of water consumed from a polycarbonate baby bottle. Nobody suggests banning milk even though it contains a good dose of estrogenic compounds. Neither should they.
That's not all. Nonylphenol, an ingredient in numerous detergents, is estrogenic. It ends up in sewage, along with natural estrogens and birth control pill remnants excreted by women. Sewage treatment plants do not remove these substances and they can end up in surface water as well as in ground water when sewage sludge is spread on fields as fertilizer.
We are awash in a sea of both natural and synthetic hormone disrupting substances and it is unrealistic to accuse a specific one of being the devil. This does not mean we should be cavalier about hormone-like substances in the environment.
Even though there is no evidence that at the levels encountered, BPA is a risk to humans, we can't rule out the possibility that babies may not excrete BPA as efficiently as adults, or that the chemical might have a synergistic effect when combined with other endocrine disrupting substances. Baby bottles made of glass or other plastics are available, and it seems a good idea to search for viable alternatives to the epoxy lining in canned foods. But panic over drinking from polycarbonate bottles is unwarranted, and talk of banning polycarbonate plastics is naive.
Joe Schwarcz is director of McGill University's Office for Science and Society
(www.OSS.McGill.ca).
He can be heard every Sunday from 3-4 p.m. on CJAD.
joe.schwarcz@mcgill.ca
© The Gazette (Montreal) 2008
Copyright © 2008 CanWest Interactive, a division of CanWest MediaWorks Publications, Inc.. All rights reserved.