CoChat
Sign Up
Cited by 838Air Quality and Health ImpactsAtmospheric chemistry and aerosolsIndoor Air Quality and Microbial Exposure

The DOI matches its Crossref record; 86 of the 89 references it cites were found in a registry or an index; none of the 92 sources its claims cite is checked for support yet.

Ozone Pollution: A Major Health Hazard Worldwide

Open access
Zhang, Junfeng (Jim), Wei, Yongjie, Fang, Zhangfu·2019·Frontiers in Immunology
DOI 10.3389/fimmu.2019.02518PMC PMC6834528
Open this paper in CoChat — free accountOpen PDF

Abstract

Oxides of nitrogen (NOx) and volatile organic compounds (VOCs) released into the atmosphere can react in the presence of solar irradiation, leading to ozone formation in the troposphere. Historically before clean air regulations were implemented to control NOx and VOCs, ozone concentrations were high enough to exert acute effects such as eye and nose irritation, respiratory disease emergencies, and lung function impairment. At or above current regulatory standards, day-to-day variations in ozone concentrations have been positively associated with asthma incidence and daily non-accidental mortality rate. Emerging evidence has shown that both short-term and long-term exposures to ozone, at concentrations below the current regulatory standards, were associated with increased mortality due to respiratory and cardiovascular diseases. The pathophysiology to support the epidemiologic associations between mortality and morbidity and ozone centers at the chemical and toxicological property of ozone as a strong oxidant, being able to induce oxidative damages to cells and the lining fluids of the airways, and immune-inflammatory responses within and beyond the lung. These new findings add substantially to the existing challenges in controlling ozone pollution. For example, in the United States in 2016, 90% of noncompliance to the national ambient air quality standards was due to ozone whereas only 10% was due to particulate matter and other regulated pollutants. Climate change, through creating atmospheric conditions favoring ozone formation, has been and will continue to increase ozone concentrations in many parts of world. Worldwide, ozone is responsible for several hundreds of thousands premature deaths and tens of million asthma-related emergency room visits annually. To combat ozone pollution globally, more aggressive reductions in fossil fuel consumption are needed to cut NOx and VOCs as well as greenhouse gas emissions. Meanwhile, preventive and therapeutic strategies are needed to alleviate the detrimental effects of ozone especially in more susceptible individuals. Interventional trials in humans are needed to evaluate the efficacy of antioxidants and ozone-scavenging compounds that have shown promising results in animal studies.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

This narrative review synthesizes evidence that tropospheric ozone, formed photochemically from NOx and VOCs, is a worldwide health hazard causing respiratory and emerging cardiovascular and CNS effects, with concentrations rising in many regions despite declines in the US and Western Europe. It argues that adverse effects occur below current regulatory standards, that climate change will worsen ozone burdens, and that more aggressive precursor emission cuts plus antioxidant/scavenger strategies are needed.

Key findings

  • Ozone exposure is associated with respiratory effects (airway inflammation, aggravated asthma, emphysema, COPD), likely asthma development, and premature death, with stronger evidence for respiratory than other mortality; children are at increased risk. In the US in 2016, 90% of non-compliance with national ambient air quality standards was due to ozone versus 10% for particulate matter and other pollutants, and 100.6 million people (nearly one in three) lived in counties exceeding the 70 ppb NAAQS in 2017.
  • Despite US reductions in NOx (61%) and VOCs (54%) from 1980–2017 and a 32% decrease in national average daily max 8-h ozone, global background ozone is rising: Mt Waliguan Observatory on the Tibetan Plateau showed increases of 0.2–0.3 ppb per year during spring and autumn (1994–2013). In the North China Plain, a 40% PM2.5 reduction from 2013–2017 was partly responsible for an ozone increase of 1–3 ppb per year.
  • Climate change is projected to increase ozone: warming alone may increase ozone-standard exceedance days across the eastern US by 68% by 2050; the 95th percentile of daily 8-h max ozone is predicted to rise from 79 ppb in 2012 to 87 ppb in 2050; and climate change alone is estimated to add 0.43 ppb (95% CI: 0.14–0.75) to average ozone in 19 southeastern US urban communities in the 2040s versus 2000.
  • Global mortality estimates vary widely: a 6% increase in premature deaths attributable to ozone from 1990 (143,000) to 2010 (152,000); 700,000 ± 300,000 respiratory mortalities in 2000; 254,000 COPD deaths in 2015; 316,000 respiratory deaths in China; ~23,500 in the EU. Ozone was linked to an estimated 9–23 million (8–20% of total) asthma-related emergency room visits globally, and DALYs lost of 6.3 ± 3.0 million years in 2000 and 4.1 (95% CI: 1.6–6.8) million years from COPD alone in 2015. A 5 ppb increase in long-term ozone was associated with 0.25 year (95% CI: −0.30 to −0.19) lower life expectancy in males and 0.21 year (95% CI: −0.25 to −0.17) in females.
  • Mechanistically, ozone as a strong oxidant induces oxidative damage and immune-inflammatory responses; Koren et al. found acute exposure (0.4 ppm for 2 h) produced an 8.2-fold increase in polymorphonuclear leukocytes in BAL fluid. Emerging evidence links ozone to cardiovascular mortality, hemostatic markers, and CNS effects including neurodegenerative disorders.

Methods

  • Narrative review (no primary data collection); the paper synthesizes atmospheric chemistry, exposure/dosimetry considerations, epidemiological and toxicological evidence, and regulatory context.
  • Draws on cited studies including controlled human exposure trials, animal/rodent studies, cohort studies (e.g., American Cancer Society cohort, US Medicare population of 60 million older adults, 2000–2012), multicity time-series studies, and climate/ozone projection modeling.
  • No systematic search strategy, inclusion criteria, or meta-analytic pooling is described.

Limitations

  • Stated: the relatively large gap in mortality estimates across studies is due to uncertainties and inconsistency in the concentration–effect relationship and ozone exposure assessment; estimates were based on respiratory effects alone due to uncertainties in cardiovascular evidence; epidemiological evidence is limited for a causal relationship between chronic exposure and mortality/morbidity; determining the best measure of long-term ozone exposure is challenging given diurnal and seasonal variation; co-exposure to PM2.5 may affect repair of ozone damage.
  • Evident from the text: as a narrative review without a stated systematic search or quality appraisal, selection of cited evidence may be non-exhaustive; several cited findings are projections or model-based rather than observed outcomes; the paper notes null findings in some European studies on long-term ozone and cardiovascular mortality, indicating inconsistency in the evidence base.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.3389/fimmu.2019.02518

Cites

86 of 86 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

0 of 92 cited sources checked · 0 supported · 0 flagged

Show all 84 claims

  • Probably not a substantial claim. 18
  • It may state two separate claims as one. 18
  • The quote only partly states this claim. 2
33 of 33

  • The authors state this as an assumption.

    The health risk associated with lower-level ozone in cold months is negligible.

    “assuming that the health risk associated with lower-level ozone in cold months is negligible”

  • The authors state this as an assumption.

    Lower concentrations during the rest of 16 h do not contribute to an adverse effect when using 8-h daily max concentration.

    “using 8-h daily max concentration assumes that lower concentrations during the rest of 16 h do not contribute to an adverse effect”

  • The paper relies on this without support.

    Some acute ozone effects are reversible.

    “some of the acute ozone effects are known to be reversible”

  • The paper relies on this without support.

    The relationship of ozone production with its precursors is non-linear, so reducing one precursor may not necessarily lead to ozone reduction.

    “Part of the challenges is the “non-linear” relationship of ozone production with its precursors, as reducing one of the precursors may not necessarily lead to ozone reduction.”

  • The paper relies on this without support.

    Even within a metropolitan area, the optimal ratio of NOx to VOCs associated with minimal ozone formation changes from day to day and from upwind to downwind.

    “Even within a metropolitan area, the optimal ratio of NOx to VOCs associated with minimal ozone formation changes from day to day (even hour to hour) and from upwind to downwind.”

  • The paper relies on this without support.

    Sources of VOCs can be numerous and hard to characterize.

    “Sources of VOCs can be numerous and hard to characterize.”

  • The paper relies on this without support.

    Some known sources of VOCs, such as household use of consumer chemicals and biogenic emissions, are difficult to control through regulatory actions.

    “Some known sources, such as household use of consumer chemicals and biogenic emissions, are difficult to control through regulatory actions.”

  • The paper relies on this without support.

    Ozone concentrations and spatiotemporal distributions are specific to local meteorological conditions, local sources of NOx and VOCs, and long-range transport of ozone and associated chemical species.

    “Although the fundamental chemistry of ozone formation is clear, ozone concentrations, and spatiotemporal distributions are specific to local meteorological conditions, local sources of NOx and VOCs, and long-range transport of ozone and associated chemical species.”

  • The paper relies on this without support.

    Aggregative regulatory actions to cut down anthropogenic emissions of NOx and VOCs have not necessarily resulted in sufficient reductions in ozone concentrations in certain areas of the United States.

    “Based on the history of ozone control in the United States, aggregative regulatory actions to cut down anthropogenic emissions of NOx and VOCs have not necessarily resulted in sufficient reductions in ozone concentrations in certain areas of the United States.”

  • The paper relies on this without support.

    The immune-inflammatory responses initiated in the lung are the key in more downstream systemic effects.

    “although the immune-inflammatory responses initiated in the lung are thought to be the key in more downstream systemic effects.”
10 of 10

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

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

  • Global annual ozone death estimates differ by orders of magnitude

    Major

    The abstract puts worldwide premature deaths at several hundred thousand annually, but the discussion attributes 23.0-40.3 million respiratory-related deaths to ozone in 2016. These cannot both describe the annual worldwide burden at the stated scale.

1 of 1

Citations

Cites

Flagged first, then by citations

Show all 89 references

3 of the 89 references couldn’t be matched to a known paper.

Cited by

Sorted by citations

Items 501–600 of 838

Related

See all

Metadata

Authors
Zhang, J. (., Wei, Y., & Fang, Z.
Affiliations
  • Duke University (US)
  • Chinese Research Academy of Environmental Sciences (CN)
  • Guangzhou Institute of Respiratory Health (CN)
Corresponding author
  • Zhang, Junfeng (Jim)
  • Wei, Yongjie
ORCID
Venue
Frontiers in Immunology
Publisher
Frontiers Media SA
Published
2019-10-31
Volume
10
Pages
2518-2518
ISSN
1664-3224 (ISSN-L)
DOI
10.3389/fimmu.2019.02518
PMC
PMC6834528
OpenAlex
W2981938452
Semantic Scholar
af6cf2853c494aaf65433b19c213b76f4250fe97
Cited by
828
References
89
Citations by year
2026: 103 · 2025: 165 · 2024: 185 · 2023: 136 · 2022: 121 · 2021: 79 · 2020: 37 · 2019: 1
FWCI
5.68
Type
journal article
Language
en
Open access
Licence
Locations
  • Frontiers in Immunology (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
Innovative Research Group Project of the National Natural Science Foundation of China
Topics
  • Physical Sciences › Environmental Science › Health, Toxicology and Mutagenesis › Air Quality and Health Impacts
  • Physical Sciences › Earth and Planetary Sciences › Atmospheric Science › Atmospheric chemistry and aerosols
  • Physical Sciences › Environmental Science › Health, Toxicology and Mutagenesis › Indoor Air Quality and Microbial Exposure
Keywords
tropospheric ozone, ozone pollution, air pollution health effects, nitrogen oxides, volatile organic compounds, asthma, respiratory mortality, cardiovascular mortality, oxidative stress, airway inflammation, immune response, ambient air quality standards, antioxidants, fossil fuel emissions, premature mortality
MeSH terms
Air Pollutants, Air Pollution, Animals, Asthma, Humans, Ozone, United States, Global Health

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

A language model drew the claims from the paper on 2026-10-10, under version 3 of the claim definition (model deepseek-v4.1-flash, prompt extract-v3).

A second model labelled each claim on 2026-10-10 (model jev-1.13-20260917, definition revision gold-guideline-v0.2).

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

Are you an author, or do you see a problem with this page? Request a review