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What's so drastic about plastic?

Yesterday I had some cheese that had been wrapped in plastic. The berries I put on top of my steel-cut oats in the morning came in a plastic box. I also ate yogurt from a plastic container, had some canned peas and drank a glass of water from one of those five gallon carboys perched atop a cooler. (Actually, it wasn't really a 'glass' of water. It was a 'clear polystyrene' of water.) I warmed up my mother-in-law's wonderful cholent (bean stew) in a Tupperware container in the microwave. And, oh yeah, I also showered twice. Once in the morning, and once after working out in the gym.

These seem to be pretty benign activities, but Fred vom Saal, a noted researcher in reproductive biology at the University of Missouri would disagree with that view. He is highly suspicious of chemicals that can leach out of plastics and goes as far as avoiding all canned foods because of concerns about the protective plastic layer that lines the inside, vom Saal worries about compounds which may interfere with the activity of hormones, the so called 'endocrine disrupters.' He says these even show up in our shower water, probably as a result of leaching from plastics in landfills, ready to be absorbed through the skin.

Professor vom Saal is no academic slouch. He earned a PhD from Rutgers University, spent a couple of years in the Peace Corps teaching biology, and carried out postdoctoral research at the University of Texas before taking up his post at the University of Missouri. But when Dow Chemical, Shell Oil or General Electric are making up a guest list for company picnics, vom Saal's name will not be on it. That's because, as he himself says, in 1995 he "stepped on an elephant's toe." Until 1990, vom Saal had been studying the effects of fluctuations of naturally occurring hormones on mice fetuses. In response to his publications, he received a phone call from Theo Colborn, a scientist at the Wildlife Fund in Washington, D.C. who had detected gender ambiguities in animals in the wild and suspected that perhaps some hormone mimicking chemicals had found their way into the environment, yore Saal then began to test substances off the laboratory shelf to see if any would indeed act as hormones, and discovered that a compound called bisphenol A did just that. He didn't realize at the time that this chemical was made industrially to the tune of some two billion pounds a year, and that it was used in the manufacture of substances ranging from baby bottles and dental sealants to the linings of food cans.

In an experiment that Changed his professional life, vom Saal treated mice with fantastically small amounts of bisphenol A and noticed that this resulted in enlarged prostate glands in the fetus. He presented his results at a conference and obviously triggered the interest of bisphenol A manufacturers. And so began an era of accusations and counter-accusations. The plastics industry maintained that effects at such low levels ran counter to accepted principles of toxicology. Bisphenol A had been thoroughly tested in animals at doses much higher than vom Saal without adverse effects. How could much smaller doses then produce the claimed results? vom Saal retorted that there were flaws in the concept that adverse effects are directly proportional to the dose, and that in the case of hormone-like chemicals, a tiny dose in the fetus could cause effects unlike any seen in adults even at higher doses.

In response to this, industry researchers tried to reproduce vom Saal's original experiments without any success and raised questions about the credibility of the work. vom Saal in turn questions the reliability of the industry's studies. Now a chance finding at Case Western Reserve University in Ohio has brought the allegations that have been flying back and forth in the scientific literature to the attention of the public.

Patricia Hunt was studying reproduction in mice when she noted an increase in abnormalities in developing egg cells.

Weeks of research did not reveal a cause. But then Hunt noticed that the clear plastic cages that the animals were kept in "looked a little worse for wear." It seems the technician in charge of the animals had used a new alkaline detergent to clean the cages, resulting in bisphenol A leaching out.

Hunt then deliberately exposed her mice to low doses of bisphenol A and found the same abnormalities. This is certainly a noteworthy scientific find because such chromosomal changes, were they to be found in humans, could cause Down's syndrome and miscarriage. But, and a very important but, this study did not show that this could occur in humans and the researchers did not examine any health effects on the animals. Hunt herself says she has no idea about the relevance of this finding to humans.

Bisphenol A producers say they have a pretty good idea of what the relevance is. Practically none. They cite published studies in which two generations of animals have been treated with both higher and lower levels of bisphenol A than in the Hunt study. There was no effect. They also point out that that polycarbonate baby bottles, which have been attacked as sources of bisphenol A, have been thoroughly studied, including after repeated filling and heating. No BPA at the remarkably low detection limit of five parts per billion was found. This is of no comfort to yam Saal who maintains that levels that defy laboratory detection can still cause an effect in animals. Others, such as world renowned toxicologist Stephen Safe of Texas A&M University, don't buy this argument. While admitting that endocrine disruption is certainly a concern, Safe points out that synthetic hormone mimics contribute less than 1/1000th of one per cent of the amount of estrogenic compounds that people consume in their diets, Natural hormone mimics in foods, found in a variety of grains, fruits and vegetables, are far more prevalent, Furthermore, there is no scientific evidence to suggest the body somehow handles these differently from synthetics, And on it goes.

So where do the dueling scientists leave the public? Confused. On the one hand, we have some researchers suggesting that hormone mimics may be responsible for an increase in prostate and breast cancer in humans, and on the other hand, many scientists maintain there is no evidence for this at all.

What do I make of it? If we start worrying about chemicals at concentrations of a few ppbs, we'll be subject to 'paralysis through analysis' and driven to despair. We are exposed to hundreds of thousands of compounds, both natural and synthetic, at such levels. It is impossible to know the consequences of such exposure. So I think I'll concentrate on things we know really matter, such as eating more fruits and vegetables (wrapped in plastic or not) and exercising. And I'll continue to take showers after my workouts. But if I ever have pet mice, I won't use caustic detergents to clean their polycarbonate cages.

Joe Schwarcz, MCIC, is the director of McGill University's Office for Science and Society. You can contact him at joe.schwarcz@mcgill.ca
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Title Annotation:researcher Fred vom Saal is concerned about the chemicals that can leach out of plastics; Chemfusion
Author:Schwarcz, Joe
Publication:Canadian Chemical News
Geographic Code:1CANA
Date:Jul 1, 2003
Words:1197
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