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Do you ever look around, possibly at the political process in our country, and ask yourself “is everyone brain-dead”? Contrary to what one would think when looking at the advances in technology our overall IQ is dropping as the decades go by, not going up! Those alive during the Victorian era actually had higher overall IQ than we do. [i] While that may explain a lot, one still has to ask what the cause could be.
During the last few decades our environmental burden has continued to increase. During the same time new illnesses that are clearly associated with environmental overload, like chemical sensitivity, have appeared. Other illness that are strongly associated with environmental overload, such as ADHD, allergies, asthma, autoimmunity, autism, T2DM, obesity and Parkinsonism have begun to increase dramatically.
The main body systems affected by environmental burden include the immune, neurological, endocrine and cardiovascular systems. Multiple toxicants that we are all commonly exposed to during daily living have been associated with damage to all of these systems.
Cognitive decline has been linked to both prenatal exposure and exposure in daily life. The major prenatal exposure that have been directly associated with neuroinflammation and loss of cognition are:
1. Organophosphate pesticides
In utero exposure to organophosphate pesticides, primarily through diet, has been associated with slower motor speed and worse motor coordination, visuospatial performance and visual memory when the children reached the age of 6-8. [This translated to a developmental delay equivalent to 1.5 - 2 years. [ii] Maternal use of personal care products, especially fragrances and nail polish have higher levels of plasticizers in their blood and urine. Those moms have kids with lower IQs by the age of 7! [iii] Moms eating high mercury fish when they are pregnant, and who then have high blood methyl mercury (levels fairly common for frequent fish eaters - nothing that far out of normal) are FOUR TIMES more likely to have a child with an IQ less than 80! Study The sad thing is that many women consume more fish during pregnancy to make a smarter child (because fish oil does that). [iv]
The major “post-natal” or daily life exposures that reduce our cognitive power along with increasing neuroinflammation are primarily:
1. Vehicular exhaust (urban air pollution)
A group of Spanish researchers led by Lillian Calderón-Garcidueñas have done a number of studies in the metropolitan area of Mexico City regarding cognition and air pollution. They have found that children exposed to higher levels of vehicular exhaust (especially PM2.5) have more problems with memory and attentiveness.[v] Children in Mexico City with no other risk factors for cognitive deficits except living in polluted areas exhibited clear cognitive deficiencies and neuroinflammation.[vi] [vii] The same relationship between vehicular exhaust and cognitive function has been found in men whose average age is 71.[viii] Those men with the highest level of traffic exposure had a mental decline that equaled 1.9 years of aging. Women between the ages of 70 – 81 with higher long-term exposure to PM2.5 and PM 2.5-10 exhibited a cognitive decline equivalent to 2 years of aging.[ix]
With indoor and outdoor exposures to vehicular exhaust being the greatest factor in neuroinflammation and cognitive decline, the second greatest factor is lead. Even though the blood lead level is lower in the United States than it has been in decades, lead remains in the environment and is still associated with cognitive decline in children and adults.
It has been shown repeatedly that children’s blood lead levels (BLL) below the current CDC level of <5 ug/dl are still capable of reducing children’s IQ levels.[x] [xi] [xii] Italian adolescents with BLL’s above 1.71 ug/dl lose 1 IQ point for each 0.19 ug/dl increase in BLL , with each doubling of the BLL equated to a 2.4 pt. reduction in IQ.[xiii] Not surprisingly lead-associated decline of cognitive function in children has been shown to persist into adulthood[xiv], giving the current state of municipal water lead contamination the potential for grave consequences amongst future adults in those areas.
Cumulative lead burden in adults, assessed via bone lead fluoroscopic assessment, has been associated with decreased cognition[xv] while BLLs have been shown no association.[xvi] Increasing levels of tibial lead were inversely related to impaired language, processing speed, eye-hand coordination, executive functioning, verbal memory, verbal learning and visual memory.[xvii] As the tibial lead concentration rose, hand-eye coordination diminished. Women in the Nurses’ Health Study also showed increased cognitive decline with increasing tibial lead levels.[xviii] Every 1-standard deviation jump in tibial lead was associated with a functional decline equivalent to 0.33 years of aging. Computerized neurobehavioral testing, easily done in a clinical setting, show clear cognitive declines associated with bone lead burden[xix], but shows no correlation with BLLs.[xx] Since bone lead measurement is unavailable to clinicians a lead mobilization test should be done in order to gain information on total body lead burden.
[i] Woodley MA, te Nijenhuis J, Murphy R, Were the Victorians cleverer than us? The decline in general intelligence estimated from a meta-analysis of the slowing of simple reaction time. Intelligence 2013;41(4):843-850.
[ii] Harari R, Julvez J, Murata K, Barr D, Bellinger DC, Debes F, Grandjean P. Neurobehavioral deficits and increased blood pressure in school-age children prenatally exposed to pesticides. Environ Health Perspect. 2010 Jun;118(6):890-6. PubMed PMID: 20185383.
[iii] Factor-Litvak P, Insel B, Calafat AM, Liu X, Perera F, Rauh VA, Whyatt RM. Persistent Associations between Maternal Prenatal Exposure to Phthalates on Child IQ at Age 7 Years. PLoS One. 2014 Dec 10;9(12):e114003. PubMed PMID: 25493564.
[iv] Jacobson JL, Muckle G, Ayotte P, Dewailly É, Jacobson SW. Relation of Prenatal Methylmercury Exposure from Environmental Sources to Childhood IQ. Environ Health Perspect. 2015 Aug;123(8):827-33. PubMed PMID:25757069.
[v] Basagaña X, Esnaola M, Rivas I, Amato F, Alvarez-Pedrerol M, Forns J, López-Vicente M, Pujol J, Nieuwenhuijsen M, Querol X, Sunyer J. Neurodevelopmental Deceleration by Urban Fine Particles from Different Emission Sources: A Longitudinal Observational Study. Environ Health Perspect. 2016 Oct;124(10):1630-1636. PubMed PMID: 27128166.
[vi] Calderón-Garcidueñas L, Mora-Tiscareño A, Ontiveros E, Gómez-Garza G,
Barragán-Mejía G, Broadway J, Chapman S, Valencia-Salazar G, Jewells V, Maronpot RR, Henríquez-Roldán C, Pérez-Guillé B, Torres-Jardón R, Herrit L, Brooks D, Osnaya-Brizuela N, Monroy ME, González-Maciel A, Reynoso-Robles R, Villarreal-Calderon R, Solt AC, Engle RW. Air pollution, cognitive deficits and brain abnormalities: a pilot study with children and dogs. Brain Cogn. 2008 Nov;68(2):117-27. PubMed PMID: 18550243.
[vii] Calderón-Garcidueñas L, Villarreal-Calderon R, Valencia-Salazar G, Henríquez-Roldán C, Gutiérrez-Castrellón P, Torres-Jardón R, Osnaya-Brizuela N, Romero L, Torres-Jardón R, Solt A, Reed W. Systemic inflammation, endothelial dysfunction, and activation in clinically healthy children exposed to air pollutants. Inhal Toxicol. 2008 Mar;20(5):499-506. PubMed PMID: 18368620.
[viii] Power MC, Weisskopf MG, Alexeeff SE, Coull BA, Spiro A 3rd, Schwartz J. Traffic-related air pollution and cognitive function in a cohort of older men. Environ Health Perspect. 2011 May;119(5):682-7. PubMed PMID: 21172758.
[ix] Weuve J, Puett RC, Schwartz J, Yanosky JD, Laden F, Grodstein F. Exposure to particulate air pollution and cognitive decline in older women. Arch Intern Med. 2012 Feb 13;172(3):219-27. doi: 10.1001/archinternmed.2011.683. PubMed PMID: 22332151.
[x] Canfield RL, Henderson CR Jr, Cory-Slechta DA, Cox C, Jusko TA, Lanphear BP. Intellectual impairment in children with blood lead concentrations below 10 microg per deciliter. N Engl J Med. 2003;348(16):1517-26. PubMed PMID:12700371.
[xi] Jusko TA, Henderson CR, Lanphear BP, Cory-Slechta DA, Parsons PJ, Canfield RL. Blood lead concentrations < 10 microg/dL and child intelligence at 6 years of age. Environ Health Perspect. 2008;116(2):243-8. PubMed PMID: 18288325.
[xii] Lanphear BP, Hornung R, Khoury J, Yolton K, Baghurst P, Bellinger DC, Canfield RL, Dietrich KN, Bornschein R, Greene T, Rothenberg SJ, Needleman HL, Schnaas L, Wasserman G, Graziano J, Roberts R. Low-level environmental lead exposure and children's intellectual function: an international pooled analysis. Environ Health Perspect. 2005 Jul;113(7):894-9. PubMed PMID: 16002379.
[xiii] Lucchini RG, Zoni S, Guazzetti S, Bontempi E, Micheletti S, Broberg K, Parrinello G, Smith DR. Inverse association of intellectual function with very low blood lead but not with manganese exposure in Italian adolescents. Environ Res. 2012 Oct;118:65-71. PubMed PMID: 22925625.
[xiv] Mazumdar M, Bellinger DC, Gregas M, Abanilla K, Bacic J, Needleman HL. Low-level environmental lead exposure in childhood and adult intellectual function: a follow-up study. Environ Health. 2011 Mar 30;10:24. PubMed PMID: 21450073.
[xv] Shih RA, Glass TA, Bandeen-Roche K, Carlson MC, Bolla KI, Todd AC, Schwartz BS. Environmental lead exposure and cognitive function in community-dwelling older adults. Neurology. 2006;67(9):1556-62. PubMed PMID: 16971698.
[xvi] van Wijngaarden E, Winters PC, Cory-Slechta DA. Blood lead levels in relation to cognitive function in older U.S. adults. Neurotoxicology. 2011;32(1):110-5. PubMed PMID: 21093481.
[xvii] Bandeen-Roche K, Glass TA, Bolla KI, Todd AC, Schwartz BS. Cumulative lead dose and cognitive function in older adults. Epidemiology. 2009;20(6):831-9. PubMed PMID: 19752734.
[xviii] Power MC, Korrick S, Tchetgen Tchetgen EJ, Nie LH, Grodstein F, Hu H, Weuve J, Schwartz J, Weisskopf MG. Lead exposure and rate of change in cognitive function in older women. Environ Res. 2014;129:69-75.PubMed PMID: 24529005.
[xix] Dorsey CD, Lee BK, Bolla KI, Weaver VM, Lee SS, Lee GS, Todd AC, Shi W,Schwartz BS. Comparison of patella lead with blood lead and tibia lead and their associations with neurobehavioral test scores. J Occup Environ Med. 2006;48(5):489-96. PubMed PMID: 16688005.
[xx] Krieg EF Jr, Chrislip DW, Crespo CJ, Brightwell WS, Ehrenberg RL, Otto DA. The relationship between blood lead levels and neurobehavioral test performance in NHANES III and related occupational studies. Public Health Rep. 2005;120(3):240-51. PubMed PMID: 16134563.