Organophosphates and ADHD: The Link Is, At Best, Unclear
May 25th, 2010
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Recently, a study published in the Journal Pediatrics has been getting a huge amount of press for indicating a possible relationship between organophosphate levels and ADHD (but interestingly NOT ADD.) Organophosphates are commonly used as pesticides and trace levels are found in a minority of food in the US. Most fruit and vegitables sold in the US do not have levels of organophosphates that are high enough to be detected by standard analytical methods, but up to 25-33% do have detectable, albeit small, amounts. Thus many people do have small but detectable amounts of these compounds in their bodies.
Organophosphates can be quite dangerous to humans and their application may require protective measures, however they tend to break down fairly quickly and when used properly the amount that remains in the end product is small and has never been conclusively linked to any health effects. Their relatively short time to breakdown has lead to their widespread adoption. Organochloride insecticides, such as DDT tend to present less danger of acute toxicity to humans, but may linger in the environment longer than organophosphates.
The study raises some interesting questions, but the way it is being reported makes it sound like it has presented far more conclusive evidence than it really has. It is already being used by “organic” agriculture groups as proof of the superiority of organic products. It is also causing a lot of fear and confusion for parents. Even personal injury attorneys are already all over it! The news reports indicate that higher body burdens of organophosphates are linked to ADHD , but in reality the study’s data and conclusions are far less black and white.
Thankfully, you can download the entire study in PDF format for FREE here.
Issues with the study:
- Assessment of which children had ADHD was determined by a phone interview with parents using questions about their children based on (DSM-IV) criteria. This introduces the very strong possibility that the diagnosis could be influenced by parental bias (how the parents view their children, amount of time spend with their children, cultural background.) Clinical diagnosis of ADHD is normally done by a professional after personally interviewing the child and parents as well as reports from teachers. Coming to a diagnosis often involves more than one session. Thus, these criteria are, at best, considerably less reliable.
- A large proportion of the children (both those who were evaluated as non-ADHD and ADHD) were bellow the detection limits for dialkyl phosphates. Because of this, the researchers focused on the matabolite with the highest concentration, dimethyl thiophosphate. This is the only chemical matabolite which showed a correspondence of any type to ADHD.
- Diethyl alkylphosphate and other organophosphate matabolites concentrations had no apparent association with ADHD. Only the compound dimethyl thiophosphate appeared to have a significant association with ADHD. This is a bit unexpected since exposure to organophosphate compounds in general should produce an increase in all metabolites and the compounds are similar – although not identical.
- The study attempted to account for possible bias by adjusting the prevalence of ADHD for other demographic factors such as age of mother at birth, income level and creatinine levels (which could influence the amount of organophosphate metabolites excreted.) However, it’s not entirely clear whether these adjustments could have introduced their own bias.
- The number of test subjects was fairly small. A total of 1139 test subjects were included of which 119 were classified as having ADD or ADHD. 30 of the subjects were medicated for ADD/ADHD, indicating that they had been independently diagnosed by a doctor. However, only one of the 30 on medication was evaluated as ADD/ADHD by the study interview criteria. The other 29 were considered non-ADD/ADHD. This is very significant since it calls into question the accuracy of the diagnostic method of the study. The authors chalk this up to the symptoms being controlled by medication, but that is, at best, questionable, since medications are usually not continuously on such medications.
- Higher concentrations of organophosphates were found in children who were categorized as “Hyperactive/Impulsive” or “combined Inattentive and Hyperactive/Impulsive” but were NOT present or not as pronounced in children who were only categorized as “Inattentive.” In other words, the apparent coloration was limited to ADHD and not to the very related condition ADD. It thus appears that hyperactivity was the deciding factor (NOT attention.) This could imply that the levels were influenced more by the level of physical activity of the children or their general behavior and activities.
- The levels of organophosphate metabolites for most subjects was relatively low (nanomoles per liter) but the variance from the lowest to the highest measured levels was enormous. Thus a few high results would strongly influence the average of a group
- A ten fold increase in organophosphate concentrations corresponds to only a 55 to 72% increase in ADHD diagnosis. This is not very large, especially given the size of the study group.
- MOST IMPORTANTLY: This study was based on one and only one collected blood and urine sample. The subjects of the study were each given a single examination during which blood and urine were collected for analysis. This measure represents only very recent exposure, since these compounds clear the body in three to six days at most. A single recent exposure to organophosphates could easily skew the analysis dramatically. The authors of the study assumed that the single analysis would be a good representation of general lifetime exposure. This is a huge, even enormous assumption.
All things considered, I’d have to come to the conclusion that this study does not yeild enough data to draw any solid conclusions. The hypothysis is interesting and may very well be valid, but the study does not lend much evidence to it. The fact that the levels were measured only once is a huge red flag. One would expect chronic exposure, especially at an early age would be the deciding factor, especially given that the symptoms would predate the analysis given. It’s simply too big a presumption to take these single levels as a representation of exposure.
Furthermore, the data on hyperactivity and concentration levels makes for a very plausible argument that the levels could be related to behavior and activity (rather than the other way around.) The authors do, however acknowledge this, stating :
Given the cross-sectional nature of our analysis,we cannot rule out the possibility that children with ADHD engage in behaviors that expose them to
higher levels of organophosphates. If this were the case,however,we would have expected to see higher levels of urinary DEAP metabolites as well, which was not the case.
While exposure to organophosphates should, at least in theory, increase both dimethyl alkylphosphate and diethyl alkylphosphates, one could just as easily turn this statement around and say that if children with high food or environmental exposure to diethyl alkylphosphates should also show higher levels of dimethyl alkylphosphates or that the association with one should hold true for the other. Of course, these chemicals are similar but not identical, so the possibility remains that the levels are explainable due to behavior.
A few plausible explanations:
Hyperactive children may drink more fluids due to their high physical activity. This could lead to a difference in levels excreted and urine composition.- Hyperactive children may spend more time outdoors playing on the ground and grass and may thus be more exposed to organophosphate compounds.
- Hyperactive children may have a greater tendency to put things in their mouth.
- Parents who categorize their children as hyperactive may be more involved in observing their children and concerning themselves with the health of their children. These parents may tend to feed their children more fresh vegetables.
- Hyperactive children may not sleep as much, or conversely may sleep more because of the amount of daily activity they get. This could influence body chemistry and rates of excretion.
Thus, this study is far from conclusive and is really not of enough significance to warrant major coverage in the mainstream press.
This entry was posted on Tuesday, May 25th, 2010 at 11:22 pm and is filed under Agriculture, Bad Science, Good Science, Misc, media. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
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May 26th, 2010 at 1:15 am
I’m having metabolite confusion.
What’s the distinction here? I see DMAP’s versus DMAP’s.
I’m also not following the logic of the causality argument.
Is it the researchers’ contention that the ratios of metabolites in the urine will vary depending upon whether organophosphate exposure is the cause or the effect?
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May 26th, 2010 at 3:27 am
note re diagnostic criteria: AFAIK (not in the ADHD-research-business myself, but my wife is) DSM-IV criteria for an ADHD-diagnose are that the child shows symptoms in at least two different settings (the 3 usual settings are school, home and freetime-outside-the-home). Not that this calls for observational data from at least TWO INDEPENDENT observers (usually parents vs teachers). ONLY if BOTH report behaviour linked with ADHD will children be diagnosed with ADHD.
At least that’s what I overheard at the dinnertable
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May 26th, 2010 at 4:00 am
Shafe said:
typeo corrected
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May 26th, 2010 at 6:31 am
Great critical look at an interesting study. Thanks much, doc
.
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May 26th, 2010 at 6:42 am
Nice review of the study and the medias response.
This single study with its possible problems would have never made it into the MSM if someone didn’t have an agenda. The results are interesting but this study is nothing more than a curiosity until further longer term studies replicate the results.
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May 26th, 2010 at 8:11 am
this study is a disgrace at every level, and in more rational times would have failed as a high school term project. Fundamental design flaws like the ones pointed out in the article should have been cause for this paper to have been rejected during peer-review, proving once again that the academic review system is very, very flawed.
Rather then getting worked up over the non-results of this study, the popular press needs to be asking if nonsense like this is a good use of public funds, and that perhaps the process of awarding research grands needs to be looked at by those from the outside, with a view to tightening acceptance criteria for financial support.
Part of the problem is that there was a time in science when there was no stigma attached to finding and publishing research that found nothing. Now for some reason, the pressure to come up with some result, no matter how flimsy, seems to be the driving force in research. It’s time to start reinforcing the idea that science progresses as much by non-results, (as it eliminates possibilities) as it does by positive findings. It would seem the concept is lost on the younger generation of researchers.
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May 26th, 2010 at 8:35 am
DV82XL said:
I’m sure you do realise that what you have written here is clearly flawed. A negative result is a negative result and you can use it to eliminate possibilities. A non-result (by which I presume you mean something entirely inconclusive) by definition doesn’t provide you with information from which you can eliminate or highlight any factors.
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May 26th, 2010 at 8:46 am
I stand corrected. Not finished my morning coffee. I meant to write negative for non.
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May 26th, 2010 at 8:48 am
To clarify, you were perhaps trying to make the point that these researchers are too quick to draw a conclusion rather than simply publishing a paper saying “We have no idea whether it has an effect or not”.
A valid point in many ways.
But, given their frankly shocking research methods, you’d have to imagine that the publishers of the study felt justified in the way they’d gone about the research (because otherwise they wouldn’t have published) and saw a connection. Not an enormous one perhaps, not one which is entirely definitive but one which is noticable in their data.
That the researchers should have been taken to court for crimes against science is besides the point to some extent. The “crime” is not the conclusion, it’s the research behind that percentage.
Given the difficulty in proving an absolute negative, you’ve got to be very thorough with your research to come down on the side of “it makes no damn difference” and be sure of it. It’s much easier to justify positive conclusions – and almost impossible to justify negative conclusions on percentages which go against you.
On the plus side, at least they didn’t say that the MMR vaccine would give your kids ADHD.
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May 26th, 2010 at 9:01 am
I’mnotreallyhere said:
Yes, and there was a time people did this
I’mnotreallyhere said:
Publishers of science journals charge the author(s) a good chunk of money to publish, it comes out out of the grant, or the institution they work for pays. It is not in the publishers interest to reject anything other that blatant fraud. Peer-reviewers get payed for reading others papers by the publisher. Guess what happens to those reviewers that reject too many papers, thus costing the publishers revenue?
I’mnotreallyhere said:
That is just too damn bad, and is not an excuse for showing positive correlation, and then using weasel-worded conclusions to cover your butt. The real point is that this paper should never have made it past the gate-keepers to begin with, and if the system were working properly, these clowns would never have floated it in the first place.
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May 26th, 2010 at 10:18 am
That’s a little harsh.
Why? The study contributes to our knowledge of the topic, and it freely admits to its design limitations in the discussion. Yes, a prospective study with multiple fluid samples and better psychiatric screening would have been preferred — the authors freely admit this. Just because the study design isn’t powerful enough to yield a definitive result is no reason to reject it.
In science, if you have some reason to suspect a causal relationship between A and B, you don’t jump straight to a multi-million dollar prospective study. You start with a small cross-sectional study, like this one. If the results are consistent with your hypothesis, as they are in this case, THEN you conduct the larger study.
But this study didn’t find nothing, it found something. It reported that something. It made a reasonable conclusion, which is that “Developmental exposure to organophosphates MIGHT have persistent effects on multiple neural systems that MAY underlie ADHD…” (emphasis mine).
Also, I’m not sure why everyone here is so upset about this. If future studies confirm a relationship between organophosphates and psychiatric disease, that’s no reason to turn to organic farming. You can easily and effectively remove pesticides from produce simply by washing it with water. If the popular media presents the false dilemma fallacy of the organic food industry as fact (either eat organic or get ADHD) that’s the fault of the popular media, not the study’s authors.
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May 26th, 2010 at 10:33 am
Benjamin Kay said:
The whole point is that the study was so badly done that it did not find anything that wasn’t lost in the statistical noise from the poor design, and poor analysis. That’s the issue here.
If this had been done with a large sample, if the subjects were independently diagnosed, if there had been a series of blood tests done over a year, if there had been soil samples taken at each of the subject’s residences, if a proper medical profile had been done for each subject, and had the study been carried out across a broad geographical area, then the results they got would have shown the posiblity of some relationship.
Given all of these flaws, some of which could have been corrected inexpensively, the study must be seen as useless. Note too that it would have been just as useless if they had found no correlation as well. We would be just as quick to condemn an industry funded survey done this poorly if it found nothing, and rightfully so.
There is just too much of this going on, and it’s not just that its a waste of time and funds, but these garbage studies are jumped on by the popular press, and blown all out of proportion. That’s the real problem, beyond the poor science.
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May 26th, 2010 at 11:01 am
DV82XL said:
I agree that this study is worse than worthless. The fact that the diagnosis was made by a phone interview and that a complete medical profile was not done is unacceptable, but even that pales in comparison to the most glaring and stunning aspect of the study, the fact that this is all based on a single sample analysis that represents only the body burden over a few days and then take the enormous leap to think this is meaningful in any way is really stunning.
I agree with Steve that there are numerous explanations that could account for this just as easily, if not just chalking it up to the random variations you’d expect to get in a relatively small sample and a single analysis done on one occasion.
DV82XL said:
That’s the problem, isn’t it? Well, there are at least a few high quality journals and at least a few editors who are aware of this and try to limit this problem. I am constantly finding myself thinking back to Sir John Maddox (former editor of the Journal Nature) who was one of the giants in the world of peer reviewed journals and who was a big activist when it came to tackling the problems in the world of scientific publishing.
Sir Maddox was a tireless advocate for high standards and did some things that would seem like heresy to some. For example, he turned the journal around to have them actually go out there and seek out studies of high quality and importance to publish and not charge an arm and a leg, as opposed to just letting deep pocketed researchers come to him with whatever they happened to have to publish.
The fact that he was at the top of such a prestigious journal obviously gave him some freedom that others might not have. The Journal Nature has such high circulation and is so highly regarded that it does not need to resort to prostituting itself to the highest bidder to make the bottom line and it has no problem with having many excellent reviewers.
We need more like Sir Maddox in the world of scientific journalism. The status quo, where all too many are not as proactive as they should be is just going to continue as long as there are not some pro-science managers who will take the bull by the horns as he did.
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May 26th, 2010 at 12:35 pm
An Actual Scientist said:
John Maddox was certainly an unsung hero of scientific journalism. Truly a sticky subject since it startles the lines between the world of media and publicity and science – two worlds that are often so incompatible.
I’m sure this paper would not be accepted in Nature even now. It would not be accepted in Science either and probably other very high quality journals. One thing that disgusts me is hearing of papers that are rejected by peer review in several journals before one accepts them. Often ones with flaws or dubious value where the authors seem to go down the totem pole until they hit one with standards low enough to take it.
Based on the amount of bad studies I’ve seen recently, I’m becoming more and more convinced that the world of peer reviewed academic journals needs a big shakeup. To put it bluntly, we have too many of them competing over too little talent and too many with questionable standards and review. We need to thin the flock and push the less high quality ones out of academia, as their noise is muddying the waters of good research.
What I would really really really love to see would be universities and research institutions start to seriously consider whether some of these journals may not be worth renewing their subscription to. Unfortunately, that’s a bit more complicated than it seems. Many subscribers don’t actually subscribe to each journal on its own. They pay for a big package deal to some broker or host that gets them subscriptions to hundreds of journals for one yearly rate along with archives and such. It would help if these subscription providers offered more al la carte options to add or remove journals from the package, but that is rare. These subscription packages are very very expensive, but still it is cheaper to buy in bulk than subscribe to each.
In any case, I do believe it could cause a real change in things if research librarians started to have more options and started to consider whether journals that publish a lot of crap and few valuable studies are really worth subscribing to. Of course, that’s just one aspect of the whole issue. Many journals are not very reliant on subscriptions.
I’m also beginning to think that the way that journals are ranked for influence and prestige is in need of an overhaul. The Science Citation Index has been a pretty consistent method of determining influence, but I’m not sure that its methodology is valid. It seems like it could just lead to encouraging attention-getting papers that stir up a lot of talk and generate headlines, and that is absolutely not what should be encouraged.
Like so many forms of media, as the internet has gone mainstream and information distribution has changed, the world of academic journals finds itself at a crossroads. We shall see where things go.
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May 26th, 2010 at 2:57 pm
Thanks for this blog post. Some family members of mine jump at the bit regarding organic food and anything ADHD/ADD related. Had to point out the bull****.
Problem regarding media attention to reports such as this is even if it is poor science, the public doesn’t care. They’re response is ‘hey, just buy organic food, why take the risk, do the few extra cents really matter?’ When of course it’s the principle and its effects on all peer-reviewed studies that is the problem.
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May 26th, 2010 at 4:54 pm
There are a number of red flags here that just don’t seem to make sense. The fact that it’s one sample is obviously such a huge hole it invalidates the whole study, but what bothers me is that they drew the conclusion that because some organophosphate metabolites were higher this was related to the condition of ADHD and somehow this corresponded to more exposure but could not be from behavioral exposure? Where does that come from???
IF one child is exposed to more organophosphate insectacides in general, like across the spectrum, or just tends to eat more food with organophosphate residue, wouldn’t you expect all or at least more of the compounds to be higher?
The fact that there is only one suggests to me that it’s something else. It might be a difference in activity, metabolism or body chemistry. Perhaps hyperactive kids spend more time running around or drink more fluids or sleep more or less or something. That’s a better explanation because just chalking it up to higher environmental exposure is not consistent with the data. Then again, there is the other possibility which is that it’s just an error, a statistical fluke, a random freak thing. That’s surely possible with such limited data and small sample size.
Shafe said:
Does not make sense to me either. If it were just higher exposure in general, they should all be higher. The ratio would be altered by some things like how they are metabolized and most importantly what organophosphate we’re talking about. There are many. Oh, and by the way, they’re used for many things besides insecticides. They never even seem to consider that.
I’m bothered by this whole thing’s conclusion. They start off with a broad brush, saying that they’re considering all compounds then they focus on only one that is the only one that is shown as higher and then they step back again and basically ignore all the others and say that this is some kind of evidence of a whole class of chemicals all being to blame. That does not make sense! Then there’s this circular logic that this somehow can’t be caused by behavior but can by environment when they don’t explain why this chemical is significant or even offer a valid hypothesis.
Michael said:
Well according to the PDF I read, they used “modified” criteria that were based off the DSM-IV. So it was not actually the formal definition of how this is diagnosed, just one “based” on it.
They don’t say exactly what it is, but if it’s a phone interview I have to imagine it’s something like “Has your child ever been cited by a teacher for being unruly?” “Does your child have trouble sitting still on long car trips?” “Does your child struggle in one or more classes at school?”
It would have to be something like that. Since it’s all parental interview based, they’d have to try to spin the diagnostic criteria into something that could be turned into a single questionnaire to have parents answer. I mean, they’re pretty much relying on what a layperson observes to try to evaluate ADD and ADHD.
Carletes said:
Well, a few extra cents add up and so does the time which is spent shopping at boutiques and stuff for getting the same product (which may even be less safe all things considered). If your priorities are right, spend those few extra cents buying them savings bonds for college or paying for school supplies or tutoring or whatever.
Also, if you want your kids to eat healthy, the bigger concern needs to be caloric intake, excessive sugar and junk food. That’s the problem really for kids. They make all kinds of organic products now, including organic cookies and stuff. That is defeating the whole idea of trying to eat healthier! Use some common sense! If you load the kids up with organic, free-range friend chicken every night followed by a heaping helping of organically certified cookies, made of organic flour, cane sugar and no artificial flavors, the kids will be just as fat is if you stuff them with regular cookies and junk.
Oh yeah, and also, I don’t have anything against the internet or television or anything, but people need to get their kids to go outside and ride their bikes, build forts in the woods, climb trees, play tag or whatever and all that other outside kind of stuff that kids used to do not so long ago. I mean, they will end up scraping their knees and stuff every once in a while, but if your kid spends more than an hour every day watching Sponge Bob Square Pants, you’re failing as a parent
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May 27th, 2010 at 8:31 pm
Where have you been, Chem Geek? I have not seen your spirited commentary in a while
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May 28th, 2010 at 11:50 pm
ADHD is only the tip of the iceburg that chemicals cause. The president announced his scientists discovered cancer is being cuased by industrial chemicals. Factory farms have destroyed our health. I feed my children only organic. It is better for them in every way. It is why they are so healthy and everyone else is sick. I feel bad for the masses fed by corporations with the nasty chemicals and radiation they put in the food. Our food needs to be alive and not dead. We are alive. Dead food makes for dead cells and then you die completely. You are what you eat. Please learn before it is too late. Organc all the way. Pestasides don’t know when to stop killing. They are concentrated evil in a bottle. Go to your bookstore and buy some natural health books to change your life for the better!
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May 29th, 2010 at 5:36 pm
Sundancer,
In the words of Teh Internets, You Fail Biology Forever.
You propose “Dead food makes for dead cells and then you die completely.”
Interesting. I had a few small abrasions on my hand earlier this week. Yet they have healed, even though I eat some of the deadest food ever (tunafish sandwiches, ramen noodles, and peanut butter and jelly sandwichs- non of which is ‘organically grown’). Yet my body still seems to heal right on up- replacing scabs with living tissue.
Now, either I am becoming a zombie, or you are wrong. I’ll go with you being wrong. Unless I really am becoming a zombie.
And correct me if I’m wrong, but doesn’t pretty much everybody “die completely”? Except zombies, of course.
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May 29th, 2010 at 6:05 pm
Sometimes it takes a hard lesson to teach these idiots the error of their ways. When I was newly married, we lived in a fourplex for the first six months while we worked on the place we were going to move to. One of the other tenants was a woman with these ideas. Among the stupidest, was feeding her two-year old raw milk, under the theory that pasteurization robbed the milk of nutrients. If fact it was a bit of a fad in Quebec at the time, driven by this one person from the country with all sorts of strange ideas about food.
At any rate, the kid got a dose of meningitis, that they traced to the milk. The kid survived and the father sued for custody, (they were not living together) but the mother was a changed person after that, and we didn’t hear squat about healthy eating from her, for the rest of the time we were there.
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May 29th, 2010 at 10:08 pm
When I was a young child, there was a small dairy farm not far from me which made ice cream onsite. It was very good icecream that was made on the premises and my family went there on several occasions and had some of it without incident. Then on one occasion the whole family stopped in there and got ice cream cones, but a couple of hours later we all were very sick. Nothing like meningitis, but a lot of material being expelled from both ends of the digestive tract. We were just lucky the previous owners of the house had put on an addition with an extra bathroom, so the house had three of them. I don’t know what would have happened if we had had one less restroom… Yeah, it was that bad.
Anyway, we came to find out that the farm didn’t pasteurize the milk that went into their products. Apparently they felt it altered the flavor or nutrition or something. I don’t even know if it was legal for them to sell it like that, but they did anyway and somehow no health inspector had made trouble at the time.
Suffice to say, we did not go back there again.
That is a big issue with these things. Chances are there won’t be a problem most of the time, but it only takes one incident to ruin your whole day… or even life.
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May 30th, 2010 at 2:01 am
Yeah, speaking of things we take for granted…. In many parts of the world that’ll happen to you if you drink the tap water.
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August 20th, 2010 at 11:46 am
I would like to know what you mean by “standard analytical methods”.
Are you talking about EPA methods? If so, what are the detection limits that you are talking about when you say “25-33% do have detectable, albeit small, amounts”
What is a “small amount”? (anything that the instrument can’t see?! or anything that couldn’t possible affect a “small” (read: child’s) neurology?)
After I wrote the question above, I googled and found a laboratory on line-one that specializes in analyses of environmental residue: their detection limit is 50 ppb (parts per billion) for these pesticides. This means that anything under 50 ppb would not necessarily be “detectable” or seen by the instrument.
Does that mean it’s inconsequential and a therefore by definition a “small” concentration and therefore wouldn’t have neurological effects?
I am not saying that the science of the original research isn’t flawed, but your statements are misleading regarding what we can and cannot see (and what that MEANS) using laboratory instrumentation.
A Canadian laboratory has developed a method to see pharmaceuticals at low parts per trillion concentrations. They are the only lab that can run the whole EPA list (about 73 analytes) of personal care products and pharmaceuticals. If a lab in the US runs a water sample and it shows no concentrations of pharmacueticals or PCPs, does that mean they are not there? or does it mean that the detection limit is too high?
Maybe pull your head out and realize that just because we can’t see it on a lab report doesn’t mean that it isn’t there and wouldn’t have a neurological effect. Your use of the word “small” is completely unscientific and quite misleading.
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August 20th, 2010 at 12:38 pm
buffy the vampire slayer said:
Who needs to pull their head out is you.
Off the shelf equipment can be set up to detect the presence of a single molecule in a diluent of any given size, detection limits in modern chemical analysis as set by need, not by lack of technique. You do not pay for resolution you do not need.
Also given any sample of water other than ultra pure grades, One can find at least one molecule or atom of just about everything, however the presence of something does not mean that it has some biological effect, because the same can be said for everything else we ingest, including the air we breath.
Finally asserting that it is unknown if trace at these low levels is potentially harmful, is only an echo of the thoroughly discredited LNT, which at any rate is not applicable to these substances.
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August 20th, 2010 at 2:28 pm
buffy the vampire slayer said:
For general purpose analysis of mixed organic material, the standard method that is most widely used has become gas chromatography/mass spectrometry. For more specialized circumstances or when the most minuscule traces need to be found this may be combined with other methods such as laser infrared spectroscopy, various types of florescence spectroscopy and micro infrared spectroscopy or electrophoresis.
For organic compounds, things like organochlorides and organophosphates, a reasonable analytic setup can easily part per billion. High end research establishments can detect tiny fractions of a part per trillion.
buffy the vampire slayer said:
Depends on the instrument.
buffy the vampire slayer said:
Actually, a “small” child is gargantuan by molecular standards. There are more atoms in your body than there are grains of sand on every beach in the world. A tiny infant still has more than 10 ^20 atoms in their body.
This is a number so enormous that we, as humans, can’t really even wrap our minds around how vast it is. We’re evolved to relate to quantities that we might encounter in daily life, but this number is many orders of magnitude beyond any practical reality you could ever hope to experience.
buffy the vampire slayer said:
Do you have evidence to show otherwise?
50 ppb would mean one part for every 20 million. That is like one car out of all the private passenger cars in the state of California.
So now here’s the analogy: There’s a car malfunctioning in California. Just one car. It’s in some random location – probably not on a major bridge or anywhere, just somewhere in the state. It could be San Fransisco, it could be Oakland, Los Angles, Thousand Oaks, Berkeley, Pasadena, San Diego, Hollywood, Fresno, Death Valley, Yosemite National Park or it could be in any of the suburbs.
Now I tell you that because of this one malfunctioning car there has been a significant disruption to the traffic in the whole state. The Highways of Los Angles are at a standstill (even more so than normal) the coastal highway is not moving, the highway border crossings to Mexico are all in a state of chaos. People are stranded on the Oakland Bay Bridge and the Golden Gate. Cars are boxed in to their spaces in the parking garages at LAX. The Port of Long Beach can’t get trucks to come in and out.
Sounds a bit ridiculous doesn’t it?
buffy the vampire slayer said:
I’m sorry. I understand that you get offended when people start using the word “small” and that this is a very sore subject for you. At least, that’s what your last girlfriend told me.
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August 20th, 2010 at 4:02 pm
drbuzz0 said:
Ugh – someone get me the brain bleach!
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August 21st, 2010 at 5:43 am
Matthew said:
That’s what she said!
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August 21st, 2010 at 9:55 am
Matthew said:
Give this a shot
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August 21st, 2010 at 11:59 am
drbuzz0 said:
((chuckle))
Someone had to say it, eh?
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