Cited by 247Air Quality and Health ImpactsAutism Spectrum Disorder ResearchIndoor Air Quality and Microbial Exposure

The DOI matches its Crossref record; 89 of the 93 references it cites were found in a registry or an index; none of the 54 sources its claims cite is checked for support yet.

A Systematic Review and Meta-Analysis of Multiple Airborne Pollutants and Autism Spectrum Disorder

Open access

Abstract

BACKGROUND: Exposure to ambient air pollution is widespread and may be detrimental to human brain development and a potential risk factor for Autism Spectrum Disorder (ASD). We conducted a systematic review of the human evidence on the relationship between ASD and exposure to all airborne pollutants, including particulate matter air pollutants and others (e.g. pesticides and metals). OBJECTIVE: To answer the question: "is developmental exposure to air pollution associated with ASD?" METHODS: We conducted a comprehensive search of the literature, identified relevant studies using inclusion/exclusion criteria pre-specified in our protocol (registered in PROSPERO, CRD # 42015017890), evaluated the potential risk of bias for each included study and identified an appropriate subset of studies to combine in a meta-analysis. We then rated the overall quality and strength of the evidence collectively across all air pollutants. RESULTS: Of 1,158 total references identified, 23 human studies met our inclusion criteria (17 case-control, 4 ecological, 2 cohort). Risk of bias was generally low across studies for most domains; study limitations were related to potential confounding and accuracy of exposure assessment methods. We rated the quality of the body of evidence across all air pollutants as "moderate." From our meta-analysis, we found statistically significant summary odds ratios (ORs) of 1.07 (95% CI: 1.06, 1.08) per 10-μg/m3 increase in PM10 exposure (n = 6 studies) and 2.32 (95% CI: 2.15, 2.51) per 10-μg/m3 increase in PM2.5 exposure (n = 3 studies). For pollutants not included in a meta-analysis, we collectively evaluated evidence from each study in rating the strength and quality of overall evidence considering factors such as inconsistency, imprecision, and evidence of dose-response. All included studies generally showed increased risk of ASD with increasing exposure to air pollution, although not consistently across all chemical components. CONCLUSION: After considering strengths and limitations of the body of research, we concluded that there is "limited evidence of toxicity" for the association between early life exposure to air pollution as a whole and diagnosis of ASD. The strongest evidence was between prenatal exposure to particulate matter and ASD. However, the small number of studies in the meta-analysis and unexplained statistical heterogeneity across the individual study estimates means that the effect could be larger or smaller (including not significant) than these studies estimate. Our research supports the need for health protective public policy to reduce exposures to harmful airborne contaminants among pregnant women and children and suggests opportunities for optimizing future research.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

This systematic review and meta-analysis found generally increased ASD risk with air pollution exposure, with the strongest evidence for particulate matter, but rated the overall evidence as “limited evidence of toxicity.” Pooled random-effects estimates were statistically significant for PM10 and PM2.5, though based on few studies with unexplained heterogeneity.

Key findings

  • Of 1,158 references, 23 human studies met inclusion criteria (17 case-control, 4 ecological, 2 cohort); risk of bias was generally low across most domains except confounding and exposure assessment.
  • Meta-analysis found a summary OR of 1.07 (95% CI: 1.06, 1.08) per 10-μg/m3 increase in PM10 (n = 6 studies) and 2.32 (95% CI: 2.15, 2.51) per 10-μg/m3 increase in PM2.5 (n = 3 studies).
  • The quality of the body of evidence across all air pollutants was rated “moderate,” and the overall strength of evidence was rated “limited evidence of toxicity.”
  • All included studies generally showed increased ASD risk with increasing air pollution exposure, but not consistently across all chemical components; non-meta-analyzed pollutants had limited data and confidence intervals commonly overlapped the null.

Methods

  • Applied the Navigation Guide systematic review methodology, based on Cochrane/GRADE, with a protocol registered in PROSPERO (CRD # 42015017890); searched PubMed, ISI Web of Science, Biosis Previews, Embase, Google Scholar, Toxline, grey literature, and expert consultation.
  • Included human studies with original data, air pollution exposure prior to ASD diagnosis/assessment, and a comparator; 23 studies were included after duplicate screening and full-text review.
  • For meta-analysis, standardized adjusted OR estimates per 10-μg/m3 increase in PM10 or PM2.5 and combined them in random-effects models with inverse variance weighting; heterogeneity assessed with Cochran’s Q and I2, with leave-one-out and hierarchical cluster analyses.

Limitations

  • The paper states that the small number of studies in the meta-analysis and unexplained statistical heterogeneity mean the effect could be larger or smaller, including not significant; sensitivity analyses suggested a single added study could shift PM10 or PM2.5 summary estimates to overlap the null.
  • The paper states that study limitations related to potential confounding and accuracy of exposure assessment methods, with many air pollutant chemicals or classes rated “high” or “probably high” risk of bias for exposure assessment.
  • The paper states that publication bias could not be assessed quantitatively because fewer than 10 studies were included in the meta-analysis; evident from the text, the evidence base is observational and heterogeneous in exposure metrics, confounder adjustment, and outcome assessment.

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Integrity signals

Registry

Crossref · 10.1371/journal.pone.0161851

Cites

89 of 89 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Figures

Fig 1 Search results for studies relevant to air pollution exposure and ASD outcome.
Fig 1 Search results for studies relevant to air pollution exposure and ASD outcome.CC0 · PubMed Central
Fig 2 Risk of bias ratings for included human studies relevant to air pollution exposure and ASD outcome. A, All criteria except exposure assessment criteria. B, Exposure assessment criteria.
Fig 2 Risk of bias ratings for included human studies relevant to air pollution exposure and ASD outcome. A, All criteria except exposure assessment criteria. B, Exposure assessment criteria.CC0 · PubMed Central
Fig 3 Meta-analysis of human studies; reported effect estimates [95% confidence interval] from individual studies (inverse-variance weighted, represented by size of rectangle) and overall pooled estimate from random effects (RE) model for PM10 exposure and ASD.
Fig 3 Meta-analysis of human studies; reported effect estimates [95% confidence interval] from individual studies (inverse-variance weighted, represented by size of rectangle) and overall pooled estimate from random effects (RE) model for PM10 exposure and ASD.CC0 · PubMed Central
Fig 4 Meta-analysis of human studies; reported effect estimates [95% confidence interval] from individual studies (inverse-variance weighted, represented by size of rectangle) and overall pooled estimate from random effects (RE) model for PM2.5 exposure and ASD.
Fig 4 Meta-analysis of human studies; reported effect estimates [95% confidence interval] from individual studies (inverse-variance weighted, represented by size of rectangle) and overall pooled estimate from random effects (RE) model for PM2.5 exposure and ASD.CC0 · PubMed Central

Verification

Claims the paper makes

31 Own interpretation · 30 Own result · 26 Own method · 23 Not checked yet · 16 No basis given

Verify all 54 references — free account

Show all 52 claims

  • It may state two separate claims as one. 44
  • Probably not a substantial claim. 40
74 of 74
  • The paper relies on this without support.

    A systematic review and meta-analysis of the evidence for the relationship between air pollution and ASD had been lacking.

    “However, a systematic review and meta-analysis of the evidence for the relationship between air pollution and ASD had been lacking.”
  • The paper relies on this without support.

    The risk-of-bias rating adequately accounts for the lack of direct exposure measurement, so no downgrade for indirectness is needed.

    “Exposures were not directly measured (lacking biomarkers or individual measurement of air pollutants); however this was accounted for in the ROB rating and no other areas of concern existed for indirectness.”
2 of 2

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Self-check

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Each contradiction between two passages listed here was confirmed by an independent check.

3 of 3

Citations

Cites

Research works printed but not linked: 5

  1. M Pino-López, 2013, Autism Spectrum Disorders and Parental Occupational Exposures, Revista Española de Salud Pública, 87, 73
  2. AS Rosenbaum, 1999, National estimates of outdoor air toxics concentrations, Journal of the Air & Waste Management Association, 49, 1138, 10.1080/10473289.1999.10463919 · DOI · Paper page
  3. Environmental Protection Agency U.S. (US EPA). Limitations in the 1996 National-Scale Air Toxics Assessment 2015. Available: https://archive.epa.gov/airtoxics/nata/web/html/conf.html.
  4. S Levesque, 2011, Diesel exhaust activates and primes microglia: air pollution, neuroinflammation, and regulation of dopaminergic neurotoxicity, Environmental Health Perspectives, 119, 1149, 10.1289/ehp.1002986 · DOI · Paper page
  5. J Lam, 2014, Applying the Navigation Guide: Case Study #4. Association Between Developmental Exposures to Ambient Air Pollution and Autism, A Systematic Review of the Human Evidence Protocol

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Metadata

Authors
Lam, J., Sutton, P., Kalkbrenner, A., Windham, G., Halladay, A., Koustas, E., Lawler, C., Davidson, L., Daniels, N., Newschaffer, C., & Woodruff, T.
Affiliations
  • University of California, San Francisco (US)
  • University of Wisconsin–Milwaukee (US)
  • California Department of Public Health (US)
  • Rutgers, The State University of New Jersey (US)
  • National Institutes of Health (US)
  • Kaiser Permanente (US)
  • Drexel University (US)
Corresponding author
Lam, Juleen
Venue
PLOS ONE
Published
2016-09-21
Volume
11
Issue
9
Pages
e0161851
ISSN
1932-6203 (ISSN-L)
OpenAlex
W2522738868
Cited by
247
References
93
Citations by year
2026: 15 · 2025: 16 · 2024: 20 · 2023: 26 · 2022: 34 · 2021: 42 · 2020: 28 · 2019: 24 · 2018: 26 · 2017: 15 · 2016: 1
FWCI
2.45
Type
journal article
Language
en
Open access
Locations
  • PLoS ONE (publishedVersion, public-domain)
  • PubMed Central (publishedVersion, public-domain)
  • PubMed (publishedVersion)
  • eScholarship (California Digital Library) (submittedVersion)
  • RePEc: Research Papers in Economics (submittedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • Figshare (submittedVersion, cc-by)
Funders
  • United States Environmental Protection Agency (P01 83543301)
  • Autism Speaks (9337)
  • National Institute of Environmental Health Sciences (PO1ES022841)
Topics
  • Physical Sciences › Environmental Science › Health, Toxicology and Mutagenesis › Air Quality and Health Impacts
  • Life Sciences › Neuroscience › Cognitive Neuroscience › Autism Spectrum Disorder Research
  • Physical Sciences › Environmental Science › Health, Toxicology and Mutagenesis › Indoor Air Quality and Microbial Exposure
Keywords
autism spectrum disorder, air pollution, particulate matter, PM10, PM2.5, prenatal exposure, early life exposure, developmental neurotoxicity, pesticides, heavy metals, ambient air pollution

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