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Apr 3, 2009 06:25 PM | 13
There are some 82,000 chemicals used commercially in the U.S., but only a fraction have been tested to make sure they're safe and just five are regulated by the U.S. Environmental Protection Agency (EPA), according to congressional investigators. But a government scientist says there's no guarantee testing actually rules out health risks anyway.
The basic premise of safety testing for chemicals is that anything can kill you in high enough doses (even too much water too fast can be lethal). The goal is to find safe levels that cause no harm. But new research suggests that some chemicals may be more dangerous than previously believed at low levels when acting in concert with other chemicals.
"Some chemicals may act in an additive fashion," Linda Birnbaum said this week at a conference held at the Columbia Center for Children's Environmental Health at Columbia University. "When we look one compound at a time, we may miss the boat."
Birnbaum, director of both the National Institute for Environmental Health Sciences (NIEHS) and the National Toxicology Program in Washington, D.C., noted that some chemicals, such as those that mimic human hormones, may combine with other hormonelike chemicals at low doses to produce big effects.
For example, bisphenol A (BPA), a primary component of some plastics, reacts with cells in the same way as the female hormone estrogen and could be acting synergistically with other pseudoestrogens in the bloodstream to produce heart disease, diabetes or liver failure. Such effects have been observed in animal studies in the lab as well as in frogs in the field for chemicals ranging from the phthalates (used to help perfumes scent linger and make plastics soft) to ubiquitous herbicides like atrazine, linked to malformation in frogs.
In fact, Birnbaum says, there may be no safe dose of certain compounds. For example, lead, a potent neurotoxicant, has been disappearing from the bloodstreams of American children since the 1970s when it was phased out of gasoline and paint. But some children are still exposed to low levels from old, peeling paint and its effects on intelligence and behavior can still be seen. "There is no safe level of lead," Birnbaum noted.
The issue of additive or low dose effects is complex, she added; human hormone levels vary from person to person as a result of inherent genetic differences, differences in genetic expression as well as different environmental exposures.
"Endocrine disruptors are a subtle challenge," Birnbaum said. "What is normal for me may not be normal for you. We all have our own normal." (NIEHS plans to begin testing a wider variety of strains of mice, rather than just a few breeds to more closely match the genetic diversity of humanity.)
Among health issues that some advocates have linked to chemical exposures: early pubescence in girls (BPA hastens the onset of pubescence in juvenile rats); asthma (car and truck exhaust can induce or worsen lung inflammation), and genital malformation (phthalates have been linked to lower sperm count and deformed penises in rats). The rise in autism is also believed by some to be at least partially linked to an environmental cause; NIEHS began in 2006 a study of mothers of autistic children who are pregnant again to see if there is any association with particular environmental exposures.
"Most people still consider their hormones as a private, innate part of their bodies," Sandra Steingraber, a biologist at Ithaca College, said at the conference,"not as a tuning fork that responds to messages streaming in from the environment. Small chemical doses can interfere with hormone levels."
Image: © iStockphoto.com / Amanda Rhode
Tags:
chemicals,
asthma,
low dose effects,
BPA,
endocrine disruptors,
phthalates,
environment
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13 Comments
Add CommentReporting on issues about potential endocrine disrupters is fraught with overstatements and errors. In some cases like bisphenol A, this is not surprising, since there are so many conflicting reports. However, several government agencies have held FACA meetings of Expert Panels that are free of any conflict of interest and these Panels have evaluated all the studies on BPA. For example, the National Toxicology Program's position statement on BPA concluded that there was limited evidence for low dose effects of BPA on human health. In addtion, in contrast to you statement "Among health issues that some advocates have linked to chemical exposures: early pubescence in girls (BPA hastens the onset of pubescence in juvenile rats); " the scienfitic literature does not indicate that BPA accelerates puberty in rats or mice.
Reply | Report Abuse | Link to thisWhat a way to stoke up the panic. Not much better than the anti-science Bush.
Reply | Report Abuse | Link to thisWhat testing model would you suggest for chemicals?
Reply | Report Abuse | Link to thisBirnbaum seems to be a smart man- director of both programs, and has stated plainly "There is no safe level of lead," if that is true, then why is there still lead in women's cosmetics, red lipsticks mainly? And how can these companies justify it's use in their products?
Reply | Report Abuse | Link to thisThis is old news. People disabled with MCS (Multiple Chemical Sensitivities) have been trying to make our government understand this for years. Only slight, almost imperceptible levels of chemicals can set off a reaction ranging from mild to deadly. The synergistic properties of chemicals are NEVER tested. And, because our technology has not caught up with being able to test for it, they tell the victims its all in their heads. Germany has led the way on this front, especially for victims of MCS. They just passed a law banning anyone from even hinting MCS is a psychogenic disease. We need more done here in the US. Corporate greed, plain and simple with our government too weak to do anything.
Reply | Report Abuse | Link to thisReporting on the possible effects of chemical and other man made hazards in our environment brings to the fore all the special interest groups who gain financially from the problem.
Reply | Report Abuse | Link to thisMy parents generation will probably be the last with increased life spans. Cancer has reached epidemic proportions and its causes surround us. We of the baby boom generation have lived through the atomic testing era and greatly increased radiation levels will take their toll. Today our planet shines brighter than the sun in the microwave spectrum. Children growing up in this environment will pay a price.
People believe successful business people are highly intelligent and will act in the interest of our species. This is not my experience. To be a successful business leader you need to be scheming, crafty, deceitful, self serving, have an average IQ and no ethics.
With such people in control of the world, our species has little chance of surviving.
Getting back to the point we need to study the impact of chemicals, radiation, microwaves and other artificially created phenomenon we introduce into our environment thoroughly.
We will find it exceptionally difficult to prove the cumulative effects of interactions between chemicals. To do so, we must test chemicals two by two at different doses until we get a definite result. But in the real world, chemicals react two by two amid thousands of others, where the number of possible combinations is colossal. If it were for producers to provide the burden of proof of innocuity, no new products would come onto the market!
Reply | Report Abuse | Link to thisI'm a social scientist, and not a chemist. What I understand is the precautionary principle. Would that be such a bad place to start?
Reply | Report Abuse | Link to this"They just passed a law banning anyone from even hinting MCS is a psychogenic disease."
Reply | Report Abuse | Link to thisI am horrified that you would suggest this is some sort of progress. If, in fact, MCS is a non-psychogenic disease, it is for Medical Professionals to decide- NOT legislators. And even so, illegalizing speech is barbaric, even if it is barbaric speech. Shame on Germany if this is true.
I am amazed that SciAm would go the "sensationalistic headline" route. I thought you were about science, not knee-jerk reactions.
Reply | Report Abuse | Link to this"Are some chemicals MORE dangerous at low levels." The word "more" is a comparative term - and yet no comparison was made. I came here expecting an article that explained that exposure to some chemicals at low levels were more dangerous than they are at higher levels.
I can understand the desire to keep headlines brief, but how about maintaining accuracy while you're at it? An even briefer headline is even more accurate: "Are some chemicals dangerous at low levels"
Brian Jones:
Reply | Report Abuse | Link to thisI was wondering which comment you are responding to since your comment did not seem relevant to any existing comment so I clicked on comment to find you are responding to my comment. I hope I am right.
I am aware of multiple chemical sensitivity, but do not suffer it, I would never support banning any discussion or research into it. I believe in free speech, even if the opinions expressed are totally unacceptable to me.
Please inform me where I have supported this concept in my comment. I do support calls for more work done on the impact of chemicals at low concentrations. After all I have been an industrial chemist and engineer since 1970 and have been exposed to a multitude of chemicals.
Brian Jones - "psychogenic" is just a way of rationalizing beating up on a portion of the human population with impunity. I think that falls under hate speech.
Reply | Report Abuse | Link to thisResearch into understanding the workings of antabuse shows that people differ in their ability to metabolize alcohol - which is one reason why some get drunk easier than others. The irony is a French-Canadian alcoholic found this out before the scientists - she figured out how to get drunk (but not violently ill) while on court ordered antabuse.
MCS is an umbrella term but one thing that most of the products that affect us are products that solvent abusers get high on - except perfume - they say that the high is not that good and the after effects are not worth it so they tend to leave perfume alone and focus on the air fresheners and lysol etc. Having MCS means that you don't have to go to the bar any more because you get wasted grocery shopping. It seems to also involve metabolizing damage because every time it took me over two days to recover from a (albeit bigger than usual) exposure, it took less to get me wasted next time.
Innocent until proven guilty is a good policy for people but not for chemicals - and that is the present policy. And those who test the chemicals BEFORE they hit the market should be at arms length from the chemical company.
Brian Jones - "psychogenic" is just a way of rationalizing beating up on a portion of the human population with impunity. I think that falls under hate speech.
Reply | Report Abuse | Link to thisResearch into understanding the workings of antabuse shows that people differ in their ability to metabolize alcohol - which is one reason why some get drunk easier than others. The irony is a French-Canadian alcoholic found this out before the scientists - she figured out how to get drunk (but not violently ill) while on court ordered antabuse.
MCS is an umbrella term but one thing that most of the products that affect us are products that solvent abusers get high on - except perfume - they say that the high is not that good and the after effects are not worth it so they tend to leave perfume alone and focus on the air fresheners and lysol etc. Having MCS means that you don't have to go to the bar any more because you get wasted grocery shopping. It seems to also involve metabolizing damage because every time it took me over two days to recover from a (albeit bigger than usual) exposure, it took less to get me wasted next time.
Innocent until proven guilty is a good policy for people but not for chemicals - and that is the present policy. And those who test the chemicals BEFORE they hit the market should be at arms length from the chemical company.