Environmental Influences on Human Development (Part II) Flashcards
Have a direct positive affect on nervous system development
Omega-3 fatty acids
Fish that is low in mercury and high in omega 3’s
Salmon
Which has more mercury, solid white or chunk light tuna?
Solid white (by 4x)
Cognitive defects in children are the main points of concern when dealing with
Mercury poisoning
Leads to upregulation of calcium transporters in the intestine, thereby facilitating the uptake of other divalent cations such as cadmium or lead
Calcium deficiency
Interferes with the development of the nervous system both before and after birth
Methylmercury
The effects of methylmercury are mediated by impacts at the molecular level, including microtubulin synthesis and attachment in the
Central nervous system
Accumulate in fish, and people who consume large quantities of fish on a daily basis, also expose their infants to developmental delay and lowered cognitive
performance
Polychlorinated Biphenyls (PCBs)
In the case of PCB’s, the major impact occurs from
Prenatal exposure
Led to a 9-13% decrease in gestation duration
-Indirectly lead to intrauterine growth retardation
PCBs
Until the 1960’s it was assumed that the placenta guarded against
Toxic substances
Associated with reduced intelligence, poorer school performance, and higher delinquency
Elevated lead levels
Early exposure to lead has a similar effect to early exposure to
Mercury
The most severe result of lead poisoning on a fetus is
Encephalopathy (leads to death)
Due to lead laws that took lead out of paint and out of gasoline, lead levels in the U.S. population have dramatically
Decreased
Who is still at risk for led poisoning?
Children from low SES neighborhoods
Dust and chips from old indoor lead paint, lead plumbing, and lead from parents work clothing are risk factors for
Children lead exposure
If you are living in a house built before 1978, you may have
Lead paint
about how many lead poisoning cases are seen in NJ preschools each year?
1000 cases per year
Are at risk for lead poisoning because they touch a lot of things and then stick their hands in their mouths
Children
Public health action should be prompted for children who’s blood lead levels are
Above 5 ug/dl
Lead exposure below 5 ug/dl has still been associated with lower
Cognitive development
What is the mean IQ?
100 +/- 15
A major risk fator for ADHD in the US
Blood lead levels (BLLs) above 2 ug/dL
The mean IQ for math and reading scores drop significantly with BLL of
Greater than 3.0 ug/dL
A “sink” for lead and other household contaminants including allergens
Carpets
Exterior paint has the highest levels of
Lead
Because of their hand to mouth behavior, children less than 2 years old are at the greatest risk for
Lead poisoning
In an inner city study, cleaning significantly reduced blood lead in children, but only for those in
Uncarpeted homes
Pass through the placenta and blood brain barrier
Pesticides
Inhibit acetylcholinesterase (AChE) allowing acetylcholine to build up at neuronal junctions
-ex: nerve gas Sarin
Organophosphate pesticides
Disrupts cell replication, differentiation, synaptogenesis, and axogenesis
AChE inhibition
Fetuses and young children are more susceptible to
Pesticides
Why are pesticides more dangerous to fetuses and young children?
- ) Rapid brain development
2. ) Lower levels of detoxifying enzymes
Several groups of pesticides, most notably the organophosphates, operate by inhibiting the critical enzyme
Acetylcholinesterase (AChE)
Although the acute toxicity of the organophosphates is unquestioned, controversy has surrounded the issue of
Chronic low level exposure
Daily exposure to pesticides in human populations is likely to be without appreciable risk of deleterious effects during a
Lifetime
Concluded that the body of evidence on low-level pesticide exposure does not warrant revision of risk assessment
USEPA
Although not all neurobehavioral functions are
effected, some show the dramatic effects of pesticide exposure on maturation of
Cognitive function
Early pesticide exposure has also been linked to
-stronger association in boys than in girls
ADHD
Do not persist in human tissue, i.e. they have a short half-life
Organophosphate pesticides (OPs)
What is the metric for organophosphate pesticide exposure?
Organophosphate dialkylphosphate (DAP) in urine or parental blood
The Columbia Center for Children’s Environmental Health: New York City Birth Cohort study on OPs showed that umbilical cord concentration of OPs was associated with
Birth weight and length discrepancies between highest and lowest exposure groups
The CHAMACOS and Mt. Sinai birth cohorts showed that DAPs in maternal urine were associated with
abnormal reflexes in neonates
The CHAMACOS and Mt. Sinai birth cohorts showed that DAPs in maternal urine resulted in decreased
Bayley mental development scores at 24 months
DAPS in 24 month old children from CHAMACOS positively associated with
Mental development
Columbia cohort in NYC showed a negative association between chlorpyrifos in cord plasma and motor and metal development evident at
36 months (not 12 or 24)
Maternal reports of pervasive developmental disorder associated with maternal DAPs in CHAMACOS and Columbia cohorts at
24 and 36 months
There is an increasing vocabulary and sentence complexity by
Age 3
Have an increased attention span and can solve simple puzzles
Three year olds
The memory capacity by age 5 is
Four numbers in a row
The memory capacity by age 10 is
Six numbers in a row
Tests memory in children
-“Tell me as many objects as you can remember”
McCarthy Test
Even a small decrease in the average IQ can have a drastic effect because it shifts more people into the qualification of
Mildly retarded
There is a stronger association between prenatal OP exposure and ADHD for
Boys and 5 year olds (vs 3.5 year olds)
The impaired development due to prenatal OP exposure becomes more apparent with
Age
Showed that parental reports of ADHD were associated with higher urinary OP metabolite levels in children
National Health and Nutrition Examination Survey (NHANES)
The Colombia cohort (residential exposure) follow up at 7 years showed that for each standard increase in chlorpyrifos exposure, what happened?
- ) IQ declined by 1.4%
2. ) Working memory declined by 2.8%
The CHAMACOS cohort (agricultural exposure) follow up at 7 years showed that average maternal DAP concentrations were associated with poorer scores for working memory, processing speed, verbal comprehension, perceptual reasoning and
Full scale IQ
In the CHAMACOS cohort (agricultural study) the average IQ deficit was
7 points
An enzyme in metabolism of OP pesticides
PON1
The Mt. Sinai cohort (residential exposure) showed that in 6-9 year old children of mothers with the PON1
192QQ genotype, increasing maternal urinary DAP
exposure was associated with
Decline in overall IQ and perceptual reasoning
Reviewed experimental toxicology and epidemiology studies to determine risk assessment of OPs in 2012
FIFRA Scientific Advisory Panel
The FIFRA Scientific Advisory Panel determined that the primary mode of action or adverse outcome pathway for OPs was
AChE inhibiton
Using AChE inhibition as biomarker of effect is thought to be protective of downstream
Cholinergic effects
Said that for OPs, data are not sufficient to establish causal pathways leading to adverse outcomes on the developing brain
FIFRA Scientific Advisory Panel
Human windows of susceptibility for prenatal exposure of OPs is
Not yet determined
The Columbia, Mt. Sinai, and CHAMCOS birth cohorts are almost exclusively from minority and poor cohorts because they represent the
Highest risk for OP exposure
New drugs undergo FDA scrutiny through the multistage drug development
Process
Considered innocent until proven guilty/harmful
Industrial chemicals
Should be demonstrably safer than waiting until they are proven devastating
New Chemicals
