1. CHILDREN’S HEALTH
Environmental Chemical Exposures (ECE) and
Children’s Neurological Health Outcomes
Lila Rubenstein, MPH
UCSF/The John Merck Fund
December, 2013

2. Approximately 1 in 6 children in the US have
been diagnosed with a developmental disability
Source: Based on data from 2006–2008. Boyle et al. (2010)

3. The percentage of children with ADHD has
increased over 50% from 1997 to 2010
9.5%
12.5%
6.3%
9.5%
3.0%
6.2%
0.0%
5.0%
10.0%
15.0%
1999 2002 2005 2008
% of Children with ADHD Ages 5-17
Boys
All Children
Girls
Source: Centers for Disease Control and Prevention, National Center for Health Statistics, National Health Interview Survey (2013)

4. The percentage of children with autism has
increased tenfold from 1997 to 2010
0.1%
1.0%
0.0%
0.2%
0.4%
0.6%
0.8%
1.0%
1.2%
1.4%
1999 2002 2005 2008
% of Children with Autism Ages 5-17
Source: Centers for Disease Control and Prevention, National Center for Health Statistics, National Health Interview Survey (2013)

5. Children below the poverty line are more likely
to have intellectual disabilities
0.0% 1.0% 2.0%
All Races/Ethnicities
White
Black or African-American
Asian
Hispanic
Mexican
Puerto Rican
All Other Races
% of Children with Intellectual Disability by Race Ages 5-17
> Poverty Level
< Poverty Level
All Incomes
Source: Centers for Disease Control and Prevention, National Center for Health Statistics, National Health Interview Survey (2013)

6. • ADHD
• Autism
• Learning Disabilities
• Intellectual Disability &
Loss of IQ
• Conduct Disorders &
Behavioral Problems
• Cerebral Palsy
• Impairments in Vision and
Hearing
Illustration Credit: Terese Winslow, 2010
Neurological diseases/disorders associated with
environmental chemical exposures
Source: US EPA. America’s Children and the Environment, Third Edition. (2013)

7. Environmental contaminants linked to adverse
neurological outcomes
• Lead
• Methylmercury
• Polychlorinated biphenyls (PCBs)
• Organophosphate pesticides
• Polybrominated diphenyl ethers (PBDEs)
• Polycyclic aromatic hydrocarbons (PAHs)
• Arsenic
• Perchlorate
• Bisphenol A (BPA)
• Phthalates
Source: US EPA. America’s Children and the Environment, Third Edition. (2013)
Well-
studied
Not as
well-
studied

8. Environmental chemical exposures associated
with neurological diseases/disorders
Chemical
Compound
Associated Neurological Disease/Disorder
ADHD Autism
Learning
Disability
Intellectual
Disability
(Mental
Retardation)
Conduct
Disorders &
Behavioral
Problems
Cerebral
Palsy
Impairments
in Vision and
Hearing
Decrease in
IQ
Lead ✔ ✔ ✔ ✔ ✔
Methylmercury ✔ ✔ ✔ ✔
PCBs ✔ ✔ ✔
Organophosphate
Pesticides
✔ ✔
PBDEs ✔
PAHs ✔ ✔
Arsenic ✔ ✔
Perchlorate ✔
BPA ✔
Phthalates ✔ ✔ ✔
Source: US EPA. America’s Children and the Environment, Third Edition. (2013)

9. Understanding ADHD: affected neurological
functions
• ADHD is the most frequently
diagnosed childhood
neurobehavioral disorder
• Etiology of ADHD not well understood
• Research suggests causation involves genes of moderate effect
amplified by environmental factors
• Epidemiological studies show associations between environmental
chemical exposures and impaired neurological functions typically
seen in ADHD
• Further research may help clarify mechanisms by which children
develop ADHD

10. Examining the role of environmental chemicals in
ADHD: altered neurological functions
Chemical Compound
Associated Neurological Disease/Disorder
Attention Executive Functions (Information Processing Skills)
Alertness
Vigilance
Working
Memory
(Verbal and
Spatial)
Response
Inhibition
Cognitive
Flexibility
Planning
Lead ✔ ✔ ✔ ✔ ✔ ✔
Methylmercury ✔
PCBs ✔ ✔ ✔ ✔ ✔
Organophosphate
Pesticides
✔ ✔ ✔
PBDEs ✔
PAHs ✔
Arsenic Insufficient Data
Perchlorate Insufficient Data
BPA ✔
Phthalates ✔ ✔
Source: adapted from Aguiar et al. (2010), Eubig et al. (2010), and Symeonides et al. (2013)

11. The total annual costs of ADHD to the US
economy are estimated at $143 to $266 billion
Adults:
Loss of productivity & income
$87-$138 billion
Children:
Health care & education
$21-$44 Billion
Families:
Support services
$33-$43 billion
Source: Doshi et al. (2012)

12. Environmental chemicals may have a
significant impact on IQ at the population level
= 1,000,000 people
Source: Gilbert et al. (2004)

13. Aggregate Loss of IQ Points in Population
(0- to 5-year old US children)
Pre-term birth and lead exposure appear to
result in the highest total loss of IQ points
Source: Bellinger et al. (2012): PT Birth = pre-term birth, OP = organophosphate pesticides
34,031,025
7,109,899
16,799,400
284,580
16,899,488
22,947,450
0
5,000,000
10,000,000
15,000,000
20,000,000
25,000,000
30,000,000
35,000,000
40,000,000
PT Birth Autism ADHD Mercury OP Lead
Medical Risks Chemical Risks

14. Precursors can help clarify the role of ECEs and the
etiology of neurodevelopmental diseases
• Birth Weight: Normal birth weight (NBW) individuals favor a
higher mean IQ score than those born at a low birth weight
(LBW)
• Preterm birth: Higher mean term born individuals have higher
observed cognitive scores than lower mean term born individuals
Source: Kormos et al. (2013); Bhutta et al. (2002),

15. Children are potentially more sensitive to ECEs
during the first 1,000 days of life
Chemical
Compound
Critical Window
Pre-natal First 6 mths 6 mths – 1 yr 1-5 years 5-7 years Late childhood
Lead ✔ ✔ ✔ ✔ (early
childhood)
✔
Methylmercury ✔ (may cause adverse effects at any point, exposure in utero and early childhood may
pose the greatest risk)
PCBs ✔ ✔
Organophosphate
Pesticides
✔ ✔ ✔ ✔
PBDEs ✔ (based on
animal
studies)
✔ (based on
animal
studies)
PAHs ✔ (based on
animal
studies, 1st
trimester)
Arsenic Unclear, but evidence suggests 1st trimester, and that duration may be more important
than critical windows of exposure
Perchlorate
BPA
Phthalates
Insufficient research

16. Chemical
Compound
Sources and Routes of Exposure
Lead
Methylmercury
PCBs
Organophosphate
Pesticides
PBDEs
Environmental chemicals: common sources and
routes of exposure
Chemical
Compound
Sources and Routes of Exposure
PAHs
Arsenic
Perchlorate
BPA
Phthalates
Fruits & vegetables
Fish
Breast milk
Schools (Dust in air)
Industrial pollution
Fish Poultry
Water Food
Water
Canned Foods Plastic
Beauty
Products
Furniture Food Children’s
Toys
Food
Receipts
Fish Shellfish
Water Paint Pottery Traffic Tobacco smoke
Breast milk

17. Areas for further research
• Limited epidemiological studies for some environmental chemicals
including organophosphate pesticides, PBDEs, phthalates, BPA,
PAHs, arsenic, and perchlorate
(EPA, 2013)
• US data showing changes in the prevalence of developmental
disabilities are scarce (Boyle, 2011)
• More research is needed to understand:
• Causes of learning disabilities (EPA, 2013)
• Magnitude of effect of pre-term birth on cognitive and behavioral
outcomes at school age (Bhutta, 2002)
• Human health effects of low-level, chronic exposure to
organophosphate pesticides (Mackenzie, 2010)
• Full range of effects of arsenic on intellectual development in children
(Smith, 2009)

18. Works Cited
1. Aguiar, A., Eubig, P. A. & Schantz, S. L. Attention Deficit/Hyperactivity Disorder: A Focused Overview for Children’s
Environmental Health Researchers. Environ Health Perspect 118, 1646–1653 (2010).
2. Axelrad, D. Environmental Contaminants and Attention-Deficity/Hyperactivity Disorder. (2008).
3. Bellinger, D. C. A Strategy for Comparing the Contributions of Environmental Chemicals and Other Risk Factors to
Neurodevelopment of Children. Environ Health Perspect 120, 501–507 (2012).
4. Bhutta AT, Cleves MA, Casey PH, Cradock MM & Anand KS. Cognitive and behavioral outcomes of school-aged children
who were born preterm: A meta-analysis. JAMA 288, 728–737 (2002).
5. Boyle, C. A. et al. Trends in the Prevalence of Developmental Disabilities in US Children, 1997–2008. Pediatrics 127,
1034–1042 (2011).
6. Doshi, J. A. et al. Economic impact of childhood and adult attention-deficit/hyperactivity disorder in the United States.
Journal of the American Academy of Child & Adolescent Psychiatry 51, 990–1002. e2 (2012).
7. Gilbert, S. G. & Weiss, B. A rationale for lowering the blood lead action level from 10 to 2 g/dL. Neurotoxicology 27, 693–
701 (2006).
8. Greer, M. A., Goodman, G., Pleus, R. C. & Greer, S. E. Health effects assessment for environmental perchlorate
contamination: the dose response for inhibition of thyroidal radioiodine uptake in humans. Environ Health Perspect 110,
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11. Mackenzie Ross, S. J. et al. Neuropsychological and psychiatric functioning in sheep farmers exposed to low levels of
organophosphate pesticides. Neurotoxicology and Teratology 32, 452–459 (2010).
12. Rice, D. & Barone, S. Critical periods of vulnerability for the developing nervous system: evidence from humans and
animal models. Environ Health Perspect 108, 511–533 (2000).
13. Smith, A. H. & Steinmaus, C. M. Health Effects of Arsenic and Chromium in Drinking Water: Recent Human Findings. Annu
Rev Public Health 30, 107–122 (2009).
14. US EPA. America’s Children and the Environment, Third Edition. (2013). at http://www.epa.gov/ace/pdfs/ACE3_2013.pdf