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Your Environment. Your Health.

Autism

Introduction

Photo of a child with autism

Join NIEHS in celebration of Autism Awareness Month in April

Check out our activities and highlights happening all month long!

April 2, 2019 • 2:00 p.m.
Join autism researchers during an upcoming Reddit Ask Me Anything to learn more about the environmental risk factors of autism spectrum disorder.
Submit your questions to Reddit Ask Science starting at 8:00 a.m.

April 24, 2019 • noon
Listen to a Partnerships for Environmental Public Health (PEPH) Webinar on autism by researchers from University of Pennsylvania and Kaiser Permanente.
Mark your calendars now!
Details to follow.

Autism

Autism, also known as autism spectrum disorder, is a broad range of conditions that affect communication and behavior, usually appearing by age 2. The Centers for Disease Control and Prevention (CDC) reports that autism affects 1 in 59 children.1

People with autism may have difficulty with communication and social interaction; restricted interests and repetitive behaviors; and inability to function effectively in school, work, and other areas of life. Although scientists are still trying to understand why some people develop autism and others don’t, risk factors may include:

  • A sibling with autism
  • Older parents
  • Certain genetic conditions, such as Down, fragile X, and Rett syndromes
  • Very low birth weight

What Causes Autism?

Studies indicate the rate of autism is rising, but causes are not well-understood. Scientists have found rare gene changes, or mutations, as well as small common genetic variations in people with autism, implying a genetic component. A growing area of research focuses on interaction of genetic and environmental factors. For example, a woman’s exposure to harmful contaminants during pregnancy may trigger a genetic mutation leading to autism in her child. No link has been found between autism and vaccines, including those containing thimerosal, a mercury-based compound.

What Environmental Factors May Be Associated With Autism?

Progress has been made toward understanding different environmental risk factors, and the clearest evidence involves events before and during birth, such as:

  • Advanced parental age at time of conception
  • Prenatal exposure to air pollution or certain pesticides
  • Maternal obesity, diabetes, or immune system disorders
  • Extreme prematurity or very low birth weight
  • Any birth difficulty leading to periods of oxygen deprivation to the baby’s brain

But these factors alone are unlikely to cause autism. Rather, they appear to increase a child’s risk for developing autism when combined with genetic factors.

What is NIEHS Doing?

NIEHS-funded researchers are primarily interested in risk factors related to gene and environment interaction. Key findings are grouped by topic below.

Air pollution – Researchers found early-life exposure to air pollution may be a risk factor for autism.

  • Children of mothers living near a freeway, and traffic-related pollution, during the third trimester of pregnancy were twice as likely to develop ASD. A distance of 1,014 feet, or a little less than 3.5 football fields, was considered near a freeway.2
  • Children with a mutation in a gene called MET, combined with high levels of exposure to air pollution, may have increased risk.3

Prenatal conditions and maternal factors – Problems with a mother’s immune system, certain metabolic conditions, or inflammation during pregnancy may be linked with higher autism risk for her children.

  • Some mothers of autistic children have antibodies, or proteins in the body that fight infection, that may interfere with their children’s brain development, possibly leading to autism.4
  • Maternal diabetes or obesity are linked to increased likelihood of having a child with autism or other developmental disability.5
  • Fever during pregnancy was associated with increased risk of autism for children.6

Metals, pesticides, and other contaminants – Prenatal and early childhood exposure to heavy metals, like mercury, lead, or arsenic; altered levels of essential metals like zinc or manganese; pesticides; and other contaminants cause concern.

  • For people in the Republic of Seychelles, fish consumption is high and a primary way they are exposed to mercury. But a study there found no association between this type of prenatal, dietary mercury exposure and autism.7
  • Researchers found that after adjusting for dietary and other mercury sources, children with autism had similar mercury levels in blood as those without.8
  • A study of twins used baby teeth to determine and compare levels of lead, manganese, and zinc in children with autism to their twin without the condition. Autistic children were low on manganese and zinc, metals essential to life, but had higher levels of lead, a harmful metal during specific developmental time periods studied.9
  • Researchers further found that altered zinc-copper cycles, which regulate metal metabolism in the body, are disrupted in ASD cases.10
  • Maternal exposure to insecticides during early pregnancy was associated with higher risk of autism in their children.11
  • Researchers are also studying contaminants such as Bisphenol A, phthalates, flame retardants, and polychlorinated biphenyls to see if they affect early brain development and possibly play a role in autism.

Nutrition – NIEHS-funded studies have found taking prenatal vitamins may help lower autism risk. Furthermore, research suggests taking vitamins and supplements might provide protective effects for those exposed to certain environmental contaminants during pregnancy.

  • Women were less likely to have a child with autism if they took a daily prenatal vitamin during the three months before and first month of pregnancy, compared to women not taking vitamins. This finding was more evident in women and children with genetic variants that made them more susceptible to developing autism.12
  • Folic acid is a source of the protective effects of prenatal vitamins. Women who took the daily recommended dosage during the first month of pregnancy had a reduced risk of having a child with autism.13
  • Pregnant mothers who used multivitamins, with or without additional iron or folic acid, were less likely to have a child with autism and intellectual disability.14
  • Folic acid intake during early pregnancy may reduce the risk of having a child with autism for those women with high exposure to air pollution15, and pesticides.16
  • Maternal prenatal vitamin intake during the first month of pregnancy may also reduce ASD recurrence in siblings of children with ASD in high-risk families.17

Notable NIEHS-funded, large-scale studies – NIEHS-funded scientists are working to better understand the environmental contributors to ASD through their continued work on the Childhood Autism Risk from Genetics and the Environment (CHARGE) study, the Markers of Autism Risk in Babies - Learning Early Signs (MARBLES) study, and The Early Autism Risk Longitudinal Investigation (EARLI) study.  

CHARGE, with more than 1,800 children enrolled, seeks to clarify the roles of genetics and environmental exposures in autism. Results indicate a variety of exposures may be associated with increased risk, including pesticides, air pollution, and maternal metabolic or immune conditions

MARBLES, with more than 400 mother-child pairs, is a unique study in that it obtains information about how exposures before, during, and after pregnancy may contribute to autism. Recent research explores the effect that prenatal exposure to phthalates and prenatal vitamins may have on autism development.18

EARLI is another study that enrolls and follows a large group of pregnant mothers of children with autism. The newborn child is subsequently followed through three years of age. The EARLI Study examines possible environmental risk factors for autism and interplay between environmental factors and genetic susceptibility. One recent study looked at DNA methylation changes, including sex-specific-related changes associated with prenatal air pollutant exposures.

Federal Collaboration

Interagency Autism Coordinating Committee (IACC) – IAAC is a federal advisory committee that coordinates federal efforts and provides advice to the secretary of the U.S. Department of Health and Human Services on issues related to autism spectrum disorder. NIEHS partners with members of IACC to summarize advances in autism research and participate in strategic planning for research needs. The committee works closely with the public, to hear their concerns and recommendations for research.

Further Reading

Stories from the Environmental Factor (NIEHS Newsletter)

Press Releases

Additional Resources

Related Health Topics


  1. CDC (U.S. Centers for Disease Control and Prevention) 2018. Data and Statistics on Autism Spectrum Disorder. [accessed 7 March 2019]. [Available CDC (U.S. Centers for Disease Control and Prevention) 2018. Data and Statistics on Autism Spectrum Disorder. [accessed 7 March 2019].]
  2. Volk HE, Hertz-Picciotto I, Delwiche L, Lurmann F, McConnell R. 2011. Residential proximity to freeways and autism in the CHARGE study. Environ Health Perspect 119(6):873-877. [Abstract Volk HE, Hertz-Picciotto I, Delwiche L, Lurmann F, McConnell R. 2011. Residential proximity to freeways and autism in the CHARGE study. Environ Health Perspect 119(6):873-877.]
  3. Volk HE, Kerin T, Lurmann F, Hertz-Picciotto I, McConnell R, Campbell DB. 2014. Autism spectrum disorder: interaction of air pollution with the MET receptor tyrosine kinase gene. Epidemiology 25(1):44-47. [Abstract Volk HE, Kerin T, Lurmann F, Hertz-Picciotto I, McConnell R, Campbell DB. 2014. Autism spectrum disorder: interaction of air pollution with the MET receptor tyrosine kinase gene. Epidemiology 25(1):44-47.]
  4. Jones KL, Van D Water J. 2018. Maternal autoantibody related autism: mechanisms and pathways. Mol Psychiatry. 24(2):252-265. [Abstract Jones KL, Van D Water J. 2018. Maternal autoantibody related autism: mechanisms and pathways. Mol Psychiatry. 24(2):252-265.]
  5. Krakowiak P, Walker CK, Bremer AA, Baker AS, Ozonoff S, Hansen RL, Hertz-Picciotto I. 2012. Maternal metabolic conditions and risk for autism and other neurodevelopmental disorders. Pediatrics 129(5):e1121-e1128. [Abstract Krakowiak P, Walker CK, Bremer AA, Baker AS, Ozonoff S, Hansen RL, Hertz-Picciotto I. 2012. Maternal metabolic conditions and risk for autism and other neurodevelopmental disorders. Pediatrics 129(5):e1121-e1128.]
  6. Brucato M, Ladd-Acosta C, Li M, Caruso D, Hong X, Kaczaniuk J, Stuart EA, Fallin MD, Wang X. 2017. Prenatal exposure to fever is associated with autism spectrum disorder in the Boston birth cohort. Autism Res 10(11):1878-1890. [Abstract Brucato M, Ladd-Acosta C, Li M, Caruso D, Hong X, Kaczaniuk J, Stuart EA, Fallin MD, Wang X. 2017. Prenatal exposure to fever is associated with autism spectrum disorder in the Boston birth cohort. Autism Res 10(11):1878-1890.]
  7. Van Wijngaarden E, Davidson PW, Smith TH, Evans K, Yost K, Love T, Thurston SW, Watson GE, Zareba G, Burns CM, Shamlaye CF, Myers GJ. 2013. Autism spectrum disorder phenotypes and prenatal exposure to methylmercury. Epidemiology 24(5):651-659. [Abstract Van Wijngaarden E, Davidson PW, Smith TH, Evans K, Yost K, Love T, Thurston SW, Watson GE, Zareba G, Burns CM, Shamlaye CF, Myers GJ. 2013. Autism spectrum disorder phenotypes and prenatal exposure to methylmercury. Epidemiology 24(5):651-659.]
  8. Hertz-Picciotto I, Green PG, Delwiche L, Hansen R, Walker C, Pessah IN. 2010. Blood mercury concentrations in CHARGE Study children with andwithout autism. Environ Health Perspect 118(1):161-166. [Abstract Hertz-Picciotto I, Green PG, Delwiche L, Hansen R, Walker C, Pessah IN. 2010. Blood mercury concentrations in CHARGE Study children with andwithout autism. Environ Health Perspect 118(1):161-166.]
  9. Arora M, Reichenberg A, Willfors C, Austin C, Gennings C, Berggren S, Lichtenstein P, Anckarsäter H, Tammimies K, Bölte S. 2017. Fetal and postnatal metal dysregulation in autism. Nat Commun 8:15493. [Abstract Arora M, Reichenberg A, Willfors C, Austin C, Gennings C, Berggren S, Lichtenstein P, Anckarsäter H, Tammimies K, Bölte S. 2017. Fetal and postnatal metal dysregulation in autism. Nat Commun 8:15493.]
  10. Curtin P, Austin C, Curtin A, Gennings C, Arora M, Tammimies K, Wilfors C, Berggre S, Siper P, Rai D, Meyering K, Kolevzon A, Mollon J, David AS, Lewis G, Zammit S, Heilbrun L, Palmer RF, Wright RO, Bölte S, Reichenberg A. 2018. Dynamical features in fetal and postnatal zinc-copper metabolic cycles predict the emergence of autism spectrum disorder. Sci Adv 30;4(5). [Abstract Curtin P, Austin C, Curtin A, Gennings C, Arora M, Tammimies K, Wilfors C, Berggre S, Siper P, Rai D, Meyering K, Kolevzon A, Mollon J, David AS, Lewis G, Zammit S, Heilbrun L, Palmer RF, Wright RO, Bölte S, Reichenberg A. 2018. Dynamical features in fetal and postnatal zinc-copper metabolic cycles predict the emergence of autism spectrum disorder. Sci Adv 30;4(5).]
  11. Brown AS, Cheslack-Postava K, Rantakokko P, Kiviranta H, Hinkka-Yli-Salomäki S, McKeague IW, Surcel HM, Sourander A. 2018. Association of Maternal Insecticide Levels With Autism in Offspring From a National Birth Cohort. Am J Psychiatry; doi: 10.1176/appi.ajp.2018.17101129. [Abstract Brown AS, Cheslack-Postava K, Rantakokko P, Kiviranta H, Hinkka-Yli-Salomäki S, McKeague IW, Surcel HM, Sourander A. 2018. Association of Maternal Insecticide Levels With Autism in Offspring From a National Birth Cohort. Am J Psychiatry; doi: 10.1176/appi.ajp.2018.17101129.]
  12. Schmidt RJ, Hansen RL, Hartiala J, Allayee H, Schmidt LC, Tancredi DJ, Tassone F, Hertz-Picciotto I. 2011. Prenatal vitamins, one-carbon metabolismgene variants, and risk for autism. Epidemiology 22(4):476-485. [Abstract Schmidt RJ, Hansen RL, Hartiala J, Allayee H, Schmidt LC, Tancredi DJ, Tassone F, Hertz-Picciotto I. 2011. Prenatal vitamins, one-carbon metabolismgene variants, and risk for autism. Epidemiology 22(4):476-485.]
  13. Schmidt RJ, Tancredi DJ, Ozonoff S, Hansen RL, Hartiala J, Allayee H, Schmidt LC, Tassone F, Hertz-Picciotto I. 2012. Maternal periconceptionalfolic acid intake and risk of autism spectrum disorders and developmental delay in the CHARGE (CHildhood Autism Risks from Genetics and Environment) case-control study. Am J Clin Nutr 96(1):80-89. [Abstract Schmidt RJ, Tancredi DJ, Ozonoff S, Hansen RL, Hartiala J, Allayee H, Schmidt LC, Tassone F, Hertz-Picciotto I. 2012. Maternal periconceptionalfolic acid intake and risk of autism spectrum disorders and developmental delay in the CHARGE (CHildhood Autism Risks from Genetics and Environment) case-control study. Am J Clin Nutr 96(1):80-89.]
  14. DeVilbiss EA, Magnusson C, Gardner RM, Rai D, Newschaffer CJ, Lyall K, Dalman D, Lee BK. 2017. Antenatal nutritional supplementation and autism spectrum disorders in the Stockholm youth cohort: population based cohort study. BMJ 359:j4273. [Abstract DeVilbiss EA, Magnusson C, Gardner RM, Rai D, Newschaffer CJ, Lyall K, Dalman D, Lee BK. 2017. Antenatal nutritional supplementation and autism spectrum disorders in the Stockholm youth cohort: population based cohort study. BMJ 359:j4273.]
  15. Goodrich AJ, Volk HE, Tancredi DJ, McConnel R, Lurmann FW, Hansen FL, Schmidt RJ. 2018. Joint effects of prenatal air pollutant exposure and maternal folic acid supplementation on risk of autism spectrum disorder. Autism Res 11(1):69-80. [Abstract Goodrich AJ, Volk HE, Tancredi DJ, McConnel R, Lurmann FW, Hansen FL, Schmidt RJ. 2018. Joint effects of prenatal air pollutant exposure and maternal folic acid supplementation on risk of autism spectrum disorder. Autism Res 11(1):69-80.]
  16. Schmidt RJ, Kogan V, Shelton JF, Delwiche L, Hansen RL, Ozonoff S, Ma CC, McCanlies EC, Bennett DH, Hertz-Picciotto I, Tancredit DJ, Volk HE. 2017. Combined Prenatal Pesticide Exposure and Folic Acid Intake in Relation to Autism Spectrum Disorder. Environ Health Perspect 125(9):097007. [Abstract Schmidt RJ, Kogan V, Shelton JF, Delwiche L, Hansen RL, Ozonoff S, Ma CC, McCanlies EC, Bennett DH, Hertz-Picciotto I, Tancredit DJ, Volk HE. 2017. Combined Prenatal Pesticide Exposure and Folic Acid Intake in Relation to Autism Spectrum Disorder. Environ Health Perspect 125(9):097007.]
  17. Schmidt RJ, Iosif AM, Guerrero AE, Ozonoff S. 2019. Association of maternal prenatal vitamin use with risk for autism spectrum disorder recurrence in young siblings. JAMA Psychiatry; doi: 10.1001/jamapsychiatry.2018.3901. [Abstract Schmidt RJ, Iosif AM, Guerrero AE, Ozonoff S. 2019. Association of maternal prenatal vitamin use with risk for autism spectrum disorder recurrence in young siblings. JAMA Psychiatry; doi: 10.1001/jamapsychiatry.2018.3901.]
  18. Shin HM, Schmidt RJ, Tancredi D, Barkoski J, Ozonoff S, Bennett DH, Hertz-Picciotto I. 2018. Prenatal exposure to phthalates and autism spectrum disorder in the MARBLES study. Environ Health 17(1):85. [Abstract Shin HM, Schmidt RJ, Tancredi D, Barkoski J, Ozonoff S, Bennett DH, Hertz-Picciotto I. 2018. Prenatal exposure to phthalates and autism spectrum disorder in the MARBLES study. Environ Health 17(1):85.]

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