ADHD “is a complex disorder so there are likely many risk factors. We are still far from understanding its etiology and relationship to environmental chemicals,” she said.
Attention-deficit symptoms were three times more frequent among the Inuit children with high mercury exposure than among their classmates with the lowest exposures, according to the study.
Nunavik children are highly exposed to mercury mostly from eating beluga whale meat. Methylmercury accumulates in large fish and marine mammals near the top of food chains.
Such high mercury levels are rare among non-Arctic populations
“We think that there’s not likely to be a significant proportion of the U.S. or Canada population exposed to the mercury levels where we’ve seen these effects,” Muckle said. But she cautioned that some segments of the population, particularly Asian communities, who eat large quantities of albacore tuna, swordfish and other large predator fish could be equally exposed.
In contrast, the lead levels associated with ADHD symptoms in the Nunavik children are considered low. They are roughly the same as average levels in U.S. children.
Previous studies of U.S. children have linked lead exposure to ADHD.
“Regardless of the population, there are effects [from lead],” Muckle said. “This is another confirmation that really low exposure to lead is associated with greater behavioral difficulties in schools.”
Lead shot used by hunters was identified through isotopes as the source in the Inuit kids. In U.S. kids, lead is mostly from old peeling paint and contaminated soil.
“It almost doesn’t matter what the source is,” Lanphear said. “It looks like lead is associated with certain effects whether it’s from paint or it’s from lead shot.”
The amounts of lead linked to hyperactivity symptoms were far below the advisory level (5 micrograms per deciliter in blood) recently set by the CDC. About half a million U.S. children between the ages of 1 and 5 exceed that level.
“A notable result of this study is that ADHD-type symptoms were found in kids with lead exposures far below the current health-based guidelines. It really reinforces that we need to rethink the guidelines if we’re finding effects at levels that are one-third or half of the current guidelines,” said Glenys Webster, a postdoctoral fellow at Simon Fraser University who studies prenatal exposure to contaminants. She was not involved in the study.
The research uncovered some important differences between lead and mercury.
For lead, the ADHD effects were linked to post-natal exposures – what the children themselves were exposed to. For mercury, it was their exposures via their pregnant mothers, detected in cord blood collected at birth.
One possible reason that lead was connected to hyperactivity and mercury to attention deficits may be that mercury exposure comes during rapid brain growth in the womb, while lead exposures come when the brain is more robust, Muckle said.
Lanphear said the scientists “did a nice job” of factoring in other influences on brain development, including nutrients from fish and smoking. One weakness of the study, he said, is that there was no information on the parents’ rates of ADHD, so the study could not factor in a potential genetic role.
The children in the study were not actually diagnosed by psychiatrists but Lanphear said teacher surveys are a “validated approach” to check for ADHD symptoms. A child is typically diagnosed with ADHD using the surveys at both school and at home.
Funded by the U.S. and Canada governments, the study is part of a two-decade investigation of children in Nunavik, who are exposed to some of the world’s highest levels of mercury and industrial chemicals called PCBs or polychlorinated biphenyls. The children have been studied for the effects of contaminants since they were born between 1993 and 1996.
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7 Comments
Add CommentMy personal bet is on the use of ultrasounds on pregnant mothers, which has become a standard practice over the last 25 years or so.
Reply | Report Abuse | Link to thisMy English is not that good, so I may make some mistakes when trying to understand its contents. If it is true, the statistics at the beginning comes from questionnaire. Do scientists acquire other kind of data such as medical results and the like?
Reply | Report Abuse | Link to thisI agree with the statement that toxic chemicals such as lead or mercury can be found in fishes and these chemicals really do harm to human health, especially to children. And I wonder whether children who eat fish which contains mercury or lead, regardless of the amount, are sure to suffer from attention deficit?
"In the United States, one of every 10 children has been diagnosed with ADHD, according to the U.S. Centers for Disease Control and Prevention."
Reply | Report Abuse | Link to thisSeriously, how many of those children have parents that do not have patience? How many of those children are "status children," children that were born simply because the mother or father wanted to be the center of attention? I am tired of reading and hearing about people that have kids and then do not want to be bothered to teach the child right from wrong. Or the parent did not know that the kid would be more work than just a show they thought they could take out of a corner to show off to people!
Our medical profession should be more involved in reporting lazy parents who would rather put their child on drugs than to educate themselves on how to be a better parent. I agree that some children may have behavioral issues, but again seriously every tenth child seems to be an extreme over-exaggerated diagnoses!
If you walked down the street and watched every ninth person give "downers" to the tenth person, you mostly likely would be appalled and demand that our government crackdown on illegal drug deals; however no one questions a parent that does not want to be bothered with the responsibility of being the center of a child's world. No, instead we allow the irresponsible parents to blame the oceans, the ground, the air, or other objects and people that are not meant to be responsible parents.
We, as a society, turn our heads away and condone lazy parents turning our medical professionals into their own personal drug dealers! It's illegal for a neighbor to give drugs to a child, simply so the child will sleep longer and the neighbor would not be bothered with the child. However, it is o.k. for a child's parent to drug the child for the same exact reason! Example of a typical lazy parent: "Little Johnny (or Suzie) always wants my attention! I can't watch my t.v. shows, talk on the phone, or play on the computer; because the kid keeps bothering me! I know I'll whine to the doctor that my child is too active and the doctor will give me medicine to sedate my child, that way I do not have to be responsible 24-hour/7-days a week for anyone but myself!"
Reply | Report Abuse | Link to thisOur medical professionals should take their own vitamins to get stronger backbones and report lazy parents to Child Welfare for endangering the health of a child; instead of giving into these spoiled-rotten, lazy, irresponsible adults! Lazy parents ARE endangering their child by giving them these drugs knowing the drug has side-effects and the parent not caring simply because the parent did not really want to be a care-giver in the first place!
Too many adults need a wake-up call to stop acting like over-grown, spoiled, whinny, annoying kids themselves! If you do not want the responsibility that comes with being a parent, THEN USE A CONDOMS AND OTHER BIRTH-CONTROL ITEMS! DON'T PUT YOUR KID ON DRUGS SIMPLY BECAUSE YOU DID NOT WANT TO TAKE BIRTH-CONTROL DRUGS YOURSELF!
(I wonder how many irresponsible parents are going to write back and try to justify their need to put their kid on drugs!)
Perhaps children who learn early to think for themselves are more likely to be seen as disruptive, therefore ADD, and more likely to take greater chances in playing with dangerous materials, such as mercury. Can one actually test for previous mercury poisoning?
Reply | Report Abuse | Link to thisI tend to see especially mental conditions in spectrums rather than categories and feel we all have some level of most symtoms.
I can appreciate what you wrote Daniel35; however does it really matter what age a child starts to "think for themselves"? It is eventually going to happen no matter what age they do. It is the responsibility of the parent(s) to know that their child will mature and know how to deal with the situation responsibly. To dope up a child simply because "mommy" and "daddy" do not what to be adults themselves and correct their child for doing something the child should not do is wrong on many levels! We, as a society, need to start holding parents more responsible for NOT correcting, teaching, or spending quality time with their child. We should be more serious about NOT condoning a parent that would rather constantly work over-time to buy non-essential items; such as a boat, jet-skis, motorcycle, fancy clothes shopping, fancy nails, etc. than spend time with their kid. Working over-time to put food on the table do to a bad economy is one thing, but to push a child aside so the parent can live a second childhood is not respectable behavior and we, as a society, need to start correcting the parents for their own childish attitudes. When we, as a society, stop condoning the spoiled adults, we will start to see more respectable behavior from their children. Until then we will continue down the path of social chaos such as; immature neighbors killing neighbors, illegal drug use, sky-rocketing fuel costs, and other social economic destruction. In movies and other media we discuss NOT indulging spoiled children; however we make the mistakes in real life by doing just that - we allow our court systems to give into bad behavior! People need to stop voting stupid and start noticing which judges do not use common-sense and instead indulge criminal behavior and vote those judges out of office. When we stop employing spoiled judges, we will start to see a huge change in the right direction of a better society. We will start to see adults thinking twice before making immature life choices themselves. That will then snowball into adults teaching their children to think twice before also making choices in life!
Reply | Report Abuse | Link to thisJust wondering: Way back in "my day" we played with mercury from broken thermometers, applying it to dimes to make them more shiney. We often washed grease off our hands with leaded gasoline. Did it take this long for some brilliant observer to discover ADD and associate it with lead and mercury? Where does ADD appear in my generation or, do scientists have another name for it...alzheimers, maybe?
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