Potential link between pesticides and ADHD

A study indicates a possible link between a pesticide and ADHD.

There's evidence -- but not proof -- of a link between a commonly used household pesticide and attention deficit hyperactivity disorder (ADHD) in children and young teens, according to a new study.

Specifically, researchers found an association between exposure to pyrethroid pesticides and ADHD, as well as ADHD symptoms such as hyperactivity and impulsivity.

The link between the pesticides and ADHD was stronger in boys than in girls, according to the findings published online in the journalEnvironmental Health.

However, researchers only found an association between pesticides and ADHD. The study did not prove a cause-and-effect relationship.

Pyrethroid pesticides -- considered safer than organophosphate pesticides -- are the most widely used pesticides for home and public health pest control, and their use in agriculture is increasing, according to the researchers.

"Given the growing use of pyrethroid pesticides and the perception that they may represent a safe alternative, our findings may be of considerable public health importance," study corresponding author Dr. Tanya Froehlich, a developmental pediatrician at Cincinnati Children's Hospital Medical Center, said in a hospital news release.

She and her colleagues analyzed data from nearly 700 children between the ages of 8 and 15. The children had taken part in the 2000-2001 National Health and Nutrition Examination Survey. The researchers looked at levels of 3-PBA -- a chemical indicator of exposure to pyrethroids -- in the children's urine.

Boys with detectable levels of 3-PBA in their urine were three times more likely to have ADHD than those without detectable 3-PBA. For every 10-fold increase in 3-PBA levels in boys, there was a 50 percent increased risk for hyperactivity and impulsivity -- both symptoms of ADHD.

In girls, levels of 3-PBA were not associated with increased risk of ADHD or symptoms of the disorder.

"Our study assessed pyrethroid exposure using 3-PBA concentrations in a single urine sample," Froehlich said. But because these chemicals don't stay in the body for long, she suggested that future studies need to take multiple measurements over time. Such studies would need to be done before "we can say definitively whether our results have public health ramifications," she said.

Previous studies have found that pyrethroid exposure increases hyperactivity, impulsivity and abnormalities in the dopamine system in male mice, according to the researchers. Dopamine is a brain chemical believed to play a role in many activities, including those that govern ADHD, the researchers said.

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Autism Risk Higher Near Pesticide-Treated Fields

Another interesting epidemiological study about the link between pesticide exposure in pregnancy and developmental delays - not just autism. -JR

Autism Risk Higher Near Pesticide-Treated Fields

Babies whose moms lived within a mile of crops treated with widely used pesticides were more likely to develop autism, according to new research 

Jun 23, 2014 |By Lindsey Konkel and Environmental Health News 

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....Babies whose moms lived within a mile of crops treated with widely used pesticides were more likely to develop autism, according to new research. 

The study of 970 children, born in farm-rich areas of Northern California, is part of the largest project to date that is exploring links between autism and environmental exposures.

The University of California, Davis research – which used women’s addresses to determine their proximity to insecticide-treated fields – is the third project to link prenatal pesticide exposures to autism and related disorders.

“The weight of evidence is beginning to suggest that mothers’ exposures during pregnancy may play a role in the development of autism spectrum disorders,” said Kim Harley, an environmental health researcher at the University of California, Berkeley who was not involved in the new study.

 

When women in the second trimester lived near fields treated with chlorpyrifos – the most commonly applied organophosphate pesticide – their children were 3.3 times more likely to have autism, according to the study. 
Credit: Wonderlane via Flickr

One in every 68 U.S. children has been identified with an autism spectrum disorder—a group of neurodevelopmental disorders characterized by difficulties with social interactions, according to the Centers for Disease Control and Prevention.

“This study does not show that pesticides are likely to cause autism, though it suggests that exposure to farming chemicals during pregnancy is probably not a good thing,” said Dr. Bennett Leventhal, a child psychiatrist at University of California, San Francisco who studies autistic children. He did not participate in the new study.....

The biggest known contributor to autism risk is having a family member with it. Siblings of a child with autism are 35 times more likely to develop it than those without an autistic brother or sister, according to the National Institutes of Health.

By comparison, in the new study, children with mothers who lived less than one mile from fields treated with organophosphate pesticides during pregnancy were about 60 percent more likely to have autism than children whose mothers did not live close to treated fields. Most of the women lived in the Sacramento Valley.

The study also reported an increased risk of developmental delays, but not autism, in kids whose moms lived near fields where carbamates, including methomyl and Sevin, were applied.

The researchers said that pesticides could impair brain development and signaling in a way that affects social interactions, learning and behavior.

Previous studies have also linked pesticide use in California to autism spectrum disorders.

In 2007, Harley and her colleagues found a two-fold increase in pervasive developmental disorders (the larger group to which autism belongs) among 531 children in California’s Salinas Valley whose mothers’ urine had higher levels of organophosphate pesticides.

Another study from 2007 found that mothers who lived near fields with the highest applications of two now-banned pesticides – endosulfan and dicofol – were six times more likely to have kids with autism spectrum disorders.

Neurobehavioral effects of developmental toxicity - What's in your garden?

Lancet Neurol. 2014 Mar;13(3):330-8. doi: 10.1016/S1474-4422(13)70278-3. Epub 2014 Feb 17.

Neurobehavioural effects of developmental toxicity.

Grandjean P1, Landrigan PJ2.

Author information

Industrial chemicals known to be toxic to the human nervous system in 2006 and 2013, according to chemical group  

	Number known in 2006	Number known in 2013	Identified since 2006
Metals and inorganic compounds	25	26	Hydrogen phosphide82
Organic solvents	39*	40	Ethyl chloride83
Pesticides	92	101	Acetamiprid,84 amitraz,85 avermectin,86 emamectin,87 fipronil (Termidor),88 glyphosate,89 hexaconazole,90 imidacloprid,91tetramethylenedisulfotetramine92
Other organic compounds	46	47	1,3-butadiene93
Total	202*	214	12 new substances

Industrial chemicals known to cause developmental neurotoxicity in human beings in 2006 and 2013, according to chemical group

	Known in 2006	Newly identified
Metals and inorganic compounds	Arsenic and arsenic compounds, lead, and methylmercury	Fluoride and manganese
Organic solvents	(Ethanol) toluene	Tetrachloroethylene
Pesticides	None	Chlorpyrifos and DDT/DDE
Other organic compounds	Polychlorinated biphenyls	Brominated diphenyl ethers
Total	6*	6

DDT=dichlorodiphenyltrichloroethane. DDE=dichlorodiphenyldichloroethylene.

*

Including ethanol.

Panel. 

Recommendations for an international clearinghouse on neurotoxicity

The main purpose of this agency would be to promote optimum brain health, not just avoidance of neurological disease, by inspiring, facilitating, and coordinating research and public policies that aim to protect brain development during the most sensitive life stages. The main efforts would aim to:

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Screen industrial chemicals present in human exposures for neurotoxic effects so that hazardous substances can be identified for tighter control

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Stimulate and coordinate new research to understand how toxic chemicals interfere with brain development and how best to prevent long-term dysfunctions and deficits

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Function as a clearinghouse for research data and strategies by gathering and assessing documentation about brain toxicity and stimulating international collaboration on research and prevention

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Promote policy development aimed at protecting vulnerable populations against chemicals that are toxic to the brain without needing unrealistic amounts of scientific proof

Abstract

Neurodevelopmental disabilities, including autism, attention-deficit hyperactivity disorder, dyslexia, and other cognitive impairments, affect millions of children worldwide, and some diagnoses seem to be increasing in frequency. Industrial chemicals that injure the developing brain are among the known causes for this rise in prevalence. In 2006, we did a systematic review and identified five industrial chemicals as developmental neurotoxicants: lead, methylmercury, polychlorinated biphenyls, arsenic, and toluene. Since 2006, epidemiological studies have documented six additional developmental neurotoxicants-manganese, fluoride, chlorpyrifos, dichlorodiphenyltrichloroethane, tetrachloroethylene, and the polybrominated diphenyl ethers. We postulate that even more neurotoxicants remain undiscovered. To control the pandemic of developmental neurotoxicity, we propose a global prevention strategy. Untested chemicals should not be presumed to be safe to brain development, and chemicals in existing use and all new chemicals must therefore be tested for developmental neurotoxicity. To coordinate these efforts and to accelerate translation of science into prevention, we propose the urgent formation of a new international clearinghouse.

Potential causes of ADD and ADHD

This article discusses possible causes of ADD and ADHD compiled from different sources. Causes include genetic factors, premature birth, and other complications. ADD/ ADHD is a complex illness with few simple solutions. JR

A study in the British Medical Journal, Lancet, has reported for the first time, direct evidence of a genetic link with ADHD. Another study published in the medical journal, Pediatrics, has suggested that increased exposure to pesticides may also be linked to ADHD. Other causes may include premature birth, complications during childbirth such as hypoxia (lack of oxygen), and prolonged exposure to anesthesia at early ages.

The study on the genetic link with ADHD, even more so, makes it increasingly clear that ADHD is not caused by bad parenting or high sugar diets. There has been too much misunderstanding about the causes of ADHD with the child and the parents being unfairly stigmatised. Misconceptions such as if the parents did a better job of parenting or if the child tried harded and wasn't lazy, then the child would not have ADHD. These are all misconceptions that only do harm to the child's self esteem as well as the parents' self esteem.

It needs to be understood that ADHD or ADD is a neurophysiologic disorder, not a result of parenting.....

The most important point is that early intervention for the child's ADHD or ADD is likely to produce the best clinical outcome. Parenting a child with ADD or ADHD is a much more challenging child rearing experience than parenting a child without ADHD or ADD. Normal parenting methods frequently are not adequate as the parents are likely to experience increased frustrations with normal parenting methods not having the impact that they desire. 

The child is more vulnerable to developing low self esteem as they feel they are not as smart as their peers, or that it will never get better for them academically,or why try hard if it doesn't make a difference. If they are impulsive, then they will trigger a lot of disapproval from adults and may get rejected by peers.

Neurologically, the ADHD or ADD child's concentration or attentional system is underfunctioning so they are unable to successfully meet their academic and even sometimes day to day challenges. When their self esteem suffers, the parent's self esteem may also suffer. Again, the earliest intervention can produce the best clinical outcome and prevent psychological problems as they get older.

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