Neuropsychological Effects of Air Pollution on Children and Adolescents (0–18 Years): A Global Bibliometric Analysis

Abstract

In recent years, increasing attention has been paid to the impact of air pollution on the neuropsychological development of children and adolescents. However, a comprehensive overview of global research trends and thematic structures in this field remains lacking. This study applies bibliometric methods to systematically analyze 1441 English-language publications from 2000 to 2024, retrieved from the Web of Science Core Collection and Scopus. Using CiteSpace 6.4.R1, VOSviewer 1.6.20, and RStudio Bibliometrix (RStudio version: 2025.05.1+496, R version: 4.5.0, Bibliometrix package version: 5.0.0), we conducted a multidimensional visualization of publication trends, contributing countries and institutions, interdisciplinary integration, author collaborations, and keyword clustering. Results show a marked increase in research output in recent years, with the United States, China, and Spain leading in publication number and international collaboration. Key research themes include particulate pollution, prenatal and early-life exposure, and neuropsychological disorders such as attention-deficit hyperactivity and autism, alongside mechanisms like oxidative stress and neuroinflammation. This study builds a knowledge framework for the field, offering insights for scholars and evidence-based guidance for policymakers to support interventions that protect the neuropsychological health of the younger population.

1. Introduction

The rapid advancement of urbanization has resulted in a substantial increase in atmospheric pollutants. Air pollution contains a complex mixture of harmful components, including fine particulate matter (PM_2.5 and PM₁₀), trace gases, volatile organic compounds (VOCs), and metals, primarily generated by fossil fuel combustion from a wide range of anthropogenic activities such as vehicular traffic, industrial operations, residential heating, and waste or agricultural burning [1,2,3]. Globally, the concentrations of pollutants such as PM_2.5 and nitrogen dioxide (NO₂) continue to rise, posing significant threats to human health [4]. Numerous studies have demonstrated strong associations between exposure to PM_2.5 and NO₂ and the onset of neurodevelopmental disorders in children [5,6]. According to the World Health Organization’s report in 2018, Air Pollution and Child Health: Prescribing Clean Air, approximately 93% of children under the age of 15 breathe polluted air every day, which can impair neurodevelopment and cognitive function, and increase the risk of asthma and childhood cancer. In response, the 2021 WHO Global Air Quality Guidelines lowered the annual mean PM_2.5 limit from 10 µg/m³ to 5 µg/m³, emphasizing protection for pregnant women and children [7]. The 2024 State of Global Air report by the Health Effects Institute identifies air pollution as the second leading global health risk, particularly threatening to children due to their physiological and neurological vulnerabilities [8]. Prenatal exposure to PM_2.5 has been confirmed through multiple cohort studies to be associated with impaired executive function and symptoms of attention deficit hyperactivity disorder (ADHD) in children [9].

Childhood and adolescence represent critical periods for neurodevelopment and cognitive formation, during which the brain exhibits high plasticity and heightened sensitivity to environmental exposures [10]. Epidemiological and experimental toxicological studies have indicated that air pollution is closely linked to chronic neuroinflammation, microglial activation, and white matter abnormalities [11,12]. These pathological changes negatively impact neurocognitive development and provide mechanistic evidence supporting the association between air pollution and neurodevelopmental disorders in children. Pollutants may interfere with neural development through mechanisms such as oxidative stress, neuroinflammation, and epigenetic regulation, leading to cognitive decline, increased ADHD risk, and even structural changes like abnormal gray matter volume [13]. Moreover, early exposure to PM_2.5 and NO₂ has been linked to autism spectrum disorders, while exposure during childhood has been associated with the onset of ADHD [14]. There is also substantial evidence correlating air pollutants with cognitive deficits, anxiety, depression, self-injury, and other behavioral issues [15]. Across different early-life stages, exposure levels are positively correlated with the risk of neuropsychological disorders, and there may be dose–response relationships between specific pollutants and developmental impairments [16]. Critical mechanistic gaps limit our ability to conclusively link PM_2.5 exposure to developmental neurotoxicity. The specific brain cells responsible for Reactive Oxygen Species (ROS) production and the functional maturity of antioxidant systems in early life remain undefined [17,18]. Furthermore, evidence for neuroinflammation as a causal pathway is constrained by sparse longitudinal data on inflammatory dynamics and an overreliance on in vitro findings to explain in vivo outcomes [18,19]. Consequently, pinpointing the cellular targets, verifying compensatory capacity across development, and obtaining longitudinal human evidence constitute essential future directions.

Despite increasing evidence highlighting the potential links between air pollution and adverse neuropsychological outcomes in children [20,21,22], research in this field remains fragmented and lacks a comprehensive bibliometric synthesis of key themes, knowledge structures, and developmental trends. Bibliometric analysis offers a systematic approach to assess the contributions of countries, institutions, authors, and journals within a specific research domain [23]. Tools such as CiteSpace and VOSviewer facilitate the construction of knowledge frameworks and identification of research hotspots and frontiers. By quantifying bibliographic data, these tools provide visual insights into core topics, influential scholars and institutions, and interdisciplinary dynamics, effectively addressing the limitations of traditional review methods [24]. VOSviewer, based on co-citation principles and multidimensional scaling, generates science maps by minimizing a target function to optimize node placement [25]. It computes “attractive” and “repulsive” forces to cluster highly related nodes while dispersing less related ones, thereby elucidating the network structure [26]. CiteSpace, developed by Prof. Chaomei Chen’s team at Drexel University, combines bibliometrics, data mining, and visualization to analyze research structures and development trends within a field [27]. As a dynamic and multidimensional tool, CiteSpace supports scholars in exploring the structural evolution of complex knowledge domains [28].

Bibliometrix, an R-based open-source package developed by scholars Massimo Aria and Corrado Cuccurullo, integrates data cleaning, statistical analysis, and scientific visualization, offering a comprehensive bibliometric solution [29]. In this study, we employed bibliometric methods to systematically analyze the impact of air pollution on the neuropsychological health of children and adolescents. While traditionally applied in Library and Information Science (LIS), bibliometric methods have extended into various disciplines. For instance, Li, Yang [30] and co-authors analyzed three decades of LIS literature and found a shift from information ordering to value-based information application, emphasizing human factors and the role of online information resources. In the field of Technology Management (TM), bibliometrics is widely used to identify emerging technologies, forecast development directions, and analyze academia-industry collaboration [31]. Research by Shi Yubo [32] and colleagues reveals that over the past 20 years, the TM field has grown significantly, with the U.S., China, and the U.K. leading the domain. In medical and health sciences, bibliometric methods help identify research hotspots and trends, and evaluate the scientific impact of hospitals, teams, and experts. For example, Zhong et al. [33] used CiteSpace to analyze the molecular mechanisms of exercise-induced anti-cancer effects, revealing metabolism, oxidative stress, gene expression, and apoptosis as key pathways. Such studies illustrate the utility of bibliometric approaches in supporting interdisciplinary research and elucidating complex phenomena.

Emerging and interdisciplinary fields can employ citation networks to trace their developmental trajectories and apply burst word analysis to uncover potential research directions [34]. Fang [35] conducted a bibliometric analysis of digital medicine using CiteSpace, highlighting its evolution as an interdisciplinary field bridging computer science, information engineering, and medicine. In the research of environmental health, bibliometric analysis has become a vital tool for identifying trends and research priorities. For instance, Chen [36,37] applied scientometric methods to map the evolution of solar-driven interfacial evaporation technologies and optimization algorithms in cold chain logistics, providing valuable references for future work. Guo and other scholars [38,39,40] combined CiteSpace, Bibliometrix, and VOSviewer to offer a holistic view of the research landscape. Building on these methodologies, this study employs bibliometric analysis to examine the research landscape on the neuropsychological effects of air pollution on children and adolescents (0–18 Years) (NEAPCA), aiming to construct a comprehensive knowledge map and offer deep insights.

In this study we used CiteSpace 6.4.R1 to visualize and analyze collected bibliographic data, including article titles, keywords, publishing institutions, regional affiliations, and author information. Based on these nodes, we systematically evaluated the progress in research on air pollution and neuropsychological outcomes in young populations. Additionally, VOSviewer 1.6.20 was utilized to generate author collaboration and journal co-occurrence networks, enabling a deeper analysis of research hotspots and academic evolution. Ultimately, we summarized the findings of our bibliometric analysis and explored future research directions. By adopting a bibliometric perspective, this study seeks to comprehensively elucidate the knowledge structure, developmental pathways, and future trends in the field of air pollution and neuropsychological health in children and adolescents. The findings aim to inform public health policymakers in optimizing environmental intervention strategies, guide researchers in identifying priority areas, and contribute to the advancement of global child and adolescent neuropsychological health. Furthermore, this bibliometric synthesis provides crucial insights for scholars specializing in this field. The paper addresses seven key research questions: (1) What is the current research scale and developmental trajectory of studies on air pollution and neuropsychological health in children and adolescents? (2) What are the core topics and frequently used keywords in this body of literature? (3) Who are the leading scholars in this field, and what are the features of their collaboration networks? (4) What are the disciplinary characteristics of the field, and is there evidence of interdisciplinary integration? (5) What are the geographic patterns of research, and are there regional hotspots? (6) Which countries or institutions lead the field, and what are their international collaboration patterns and academic influence? (7) Which journals have predominantly published research on the association between air pollution and neuropsychological health in children and adolescents?

2. Methods

2.1. Data Sources and Retrieval Strategy

This study selected the Web of Science Core Collection (WOSCC) and Scopus databases as the primary sources for literature retrieval, aiming to comprehensively collect publications related to the impact of air pollution on the neuropsychological health of children and adolescents. The search was conducted for the period from 1 January 2000 to 31 December 2024. The language was restricted to English, and only articles and reviews were included. Publications that were topically irrelevant, contained incomplete information, or belonged to non-academic types (e.g., books, conference proceedings, and redundant literature) were excluded. Before conducting the search, we systematically reviewed the authoritative literature in this field to extract all the standard terms and common expressions related to the research topic and classified the terms into three categories: pollutant types, health impacts, and populations. Then, we selected the highly cited papers published in the Web of Science Core Collection and Scopus over the past 5 years (2020–2024), and examined whether the titles, abstracts, and keywords of the papers contained the core terms of this study. At the same time, we added the terms related to the research topic in the literature (terms that were not included in the established search formula.

Advanced search functions of both databases were employed, with multiple synonym combinations used to construct the search queries. Keywords related to air pollution included: “air pollution”, “PM_2.5”, “NO₂”, “ozone”, and “particulate matter”. Keywords related to children and adolescents included: “child”, “adolescent”, “pediatric”, “teenager”, and “youth”. For neuropsychological development, keywords such as “neurological effects”, “neurodevelopment”, “cognitive function”, “mental health”, “nervous system”, “brain development”, “behavioral disorder”, “ADHD”, “autism”, and “learning disability” were used. These three groups of keywords were connected using the Boolean operator “AND”. It is important to note that field-tag syntax differs between the two databases: Scopus uses TITLE-ABS-KEY to target titles, abstracts, and keywords, while WOS uses TS (Topic Search) for the same purpose. Both databases support Boolean operators (AND/OR) and wildcard characters (e.g., *) to enhance retrieval flexibility. Detailed search strategies are provided in the Appendix A.

2.2. Literature Screening

The exclusion criteria for literature were as follows: (1) studies lacking a direct link between air pollution and neuropsychological development in children and adolescents, including those addressing only air pollution or only youth populations; (2) publications with incomplete bibliographic information, such as missing titles, abstracts, or keywords; and (3) studies unrelated to neuropsychological research.

All retrieved records from the two databases were imported into NoteExpress for reference management. Using NoteExpress’s duplicate detection function based on “title”, “author”, and “journal”, duplicate entries were identified and removed (426). Subsequently, the titles, keywords, and abstracts of all records were manually screened to exclude studies (80) not meeting the inclusion criteria. The literature screening was conducted by three individuals. Two of them screened the literature in accordance with the screening criteria, and any controversial cases were referred to the third individual to decide whether to retain the literature.

2.3. Data Analysis

NoteExpress was used to manage the retrieved literature and extract data on annual publication numbers. These data were then processed using Excel to generate a temporal trend graph of yearly publication output. The filtered records were converted into compatible formats and imported into VOSviewer (version 1.6.20) and CiteSpace (version 6.4.R1) for in-depth bibliometric analysis.

In CiteSpace, the time slicing was set to one or two years depending on the analysis objective. The Pathfinder algorithm was used for pruning, and the Top N parameter was set to 50 to balance network density and core node recognition. For constructing the country collaboration network, default settings were maintained to ensure comparability. Institutional collaboration networks were generated with a minimum co-authorship threshold of 20. Keyword co-occurrence and clustering were performed using the log-likelihood ratio (LLR) algorithm, and a dual-map overlay of journals was created. Additionally, CiteSpace was employed to detect citation burst keywords.

In VOSviewer, journal co-occurrence networks were constructed with a minimum threshold of five publications per journal to ensure meaningful representation of the network structure. Finally, the Bibliometrix package in RStudio (RStudio version: 2025.05.1+496, R version: 4.5.0, Bibliometrix package version: 5.0.0) was utilized to generate a global collaboration map and Sankey diagrams illustrating the relationships among countries, authors, and affiliated institutions.

The overall literature screening and bibliometric analysis workflow is illustrated in Figure 1.

3. Results and Discussion

3.1. Analysis of the Number of Publication on the Impact of Air Pollution on the Neuro-Mental Health of Children and Adolescents

A total of 1441 publications related to the impact of air pollution on the neuropsychological health of children and adolescents were retrieved from 1 January 2000 to 31 December 2024. Literature before 2000 was excluded because it was relatively scarce in databases like Web of Science and Scopus, and early databases lacked unified standards for data format and information completeness—resulting in inconsistent records that failed to meet the demand for large-scale, standardized data in bibliometric analysis. Figure 2 illustrates the annual distribution of publications in this field. Overall, the number of publications has shown a fluctuating but generally increasing trend. From 2000 to 2013, the annual output remained relatively low. A noticeable surge began in 2014, with 28 publications, and peaked in 2022 with 70 publications. Although a slight decline occurred in 2023, the output rebounded sharply in 2024, reaching a record high of 206 publications. Of particular note, the year 2014 marked the most significant year-on-year growth, with a 140% increase compared to the previous year, indicating the onset of a rapid development phase in this research domain. Articles published during the recent four-year period (2021–2024) account for approximately 48% of the total literature, highlighting the intensifying scholarly interest in this area. Furthermore, the compound annual growth rate (CAGR) of publication number between 2000 and 2024 fluctuated mostly between 12% and 19%, with the highest rate of 19% observed in 2014. These figures suggest that the field has maintained relatively steady growth over an extended period. Based on trend fitting of the data shown in Figure 2, it can be inferred that research output in this domain is likely to continue increasing, reflecting a growing global interest and sustained academic attention to the neuropsychological impacts of air pollution on younger populations.

3.2. Country and Institutional Research Mapping Analysis

We obtained the data in

Table 1. Top 10 countries by number of publication about NEAPCA research field.

Published Number	Centrality	Starting Year	Country
656	0.26	2000	USA
205	0.08	2006	CHINA
132	0.10	2003	ENGLAND
128	0.05	2002	SPAIN
78	0.12	2001	CANADA
70	0.13	2012	AUSTRALIA
68	0.01	2005	THE NETHERLANDS
61	0.08	2006	ITALY
60	0.06	2005	GERMANY
46	0.07	2010	MEXICO

by using the CiteSpace (version 6.4.R1) software. We chose the national nodes for the analysis. The parameters were mainly kept at the default settings of the software to ensure objectivity and reproducibility. The time span was set to once every two years, and the selection criteria for nodes within each period was the 50 countries with the highest occurrence frequency (g index: k = 25). The centrality values were automatically calculated by the software algorithm. In the national cooperation network, the centrality of 0.26 for the United States indicates that it is in a more central position and has strong influence, while the centrality of 0.01 for the Netherlands implies that it is more marginal and has weaker influence. The analysis, as detailed in Table 1, revealed that the top five countries in terms of publication number on the neuropsychological impacts of air pollution on children and adolescents are the United States (656 publications), China (205), England (132), Spain (128), and Canada (78). Figure 3 shows that this international cooperation network has a “core–periphery” structure. The United States is the absolute core node with high centrality, extensive cooperation and strong resource control power; China, England, etc., are secondary core nodes, playing a hub role in regional cooperation.

The primary institutions contributing to this research domain include medical schools and schools of public health affiliated with comprehensive universities, as well as independent research centers focused on medical and environmental health sciences [11,41]. These institutions primarily represent disciplines such as medicine, public health, and interdisciplinary science. Specifically, their research includes the following areas: Public Health Sciences: Population and Public Health Sciences, Public Health, Environmental Health, Epidemiology, and Preventive Medicine; Clinical Medicine: Neurology, Psychiatry, and Pediatrics; and Basic and Interdisciplinary Research: Biostatistics and psychology.

As illustrated in Figure 4, the Barcelona Institute for Global Health (ISGlobal) has emerged as a leading institution in this field, with notable academic influence. ISGlobal focuses on health challenges associated with air pollution, climate change, urban health inequalities, and global health issues in low- and middle-income countries [42,43]. The institute adopts a problem-oriented research model and maintains close collaborations with global partners, particularly in Africa, South Asia, and Latin America. Its efforts are characterized by strong international cooperation and a focus on high-impact public health outcomes.

The top five most productive research departments in this field are the Department of Pediatrics, Department of Epidemiology, Department of Environmental Health, Department of Psychiatry, and Schools of Public Health, as detailed in

Table 2. Top 10 academic departments by number of publications.

Publication Numbers	Centrality	Starting Year	Institute
95	0.16	2003	Department of Pediatrics
94	0.13	2005	Department of Epidemiology
74	0.18	2005	Department of Environmental Health
56	0.07	2013	Department of Psychiatry
51	0.05	2008	School of Public Health
42	0.10	2008	Department of Environmental Health Sciences
42	0.08	2005	Department of Preventive Medicine
41	0.07	2010	Department of Biostatistics
41	0.03	2017	ISGlobal
37	0.06	2013	Department of Psychology

. Among them, the Department of Pediatrics leads in publication number, demonstrating high research activity in studies addressing the effects of air pollution on children and adolescents. The Department of Environmental Health, with a centrality score of 0.18 in the institutional collaboration network, occupies a key position in the research structure focused on neuropsychological impacts of air pollution on younger populations.

In-depth analysis of the research landscape across countries and institutions reveals marked disparities in study design, exposure assessment methods, and pollutant focus. High-income countries in Europe and North America tend to adopt cross-sectional designs, often supplemented by longitudinal cohort studies [44]. Notable examples include the Adolescent Brain Cognitive Development (ABCD) study in the United States and the NeuroSmog project in Poland, both of which represent large-scale cohort designs [45]. In contrast, most studies conducted in China rely primarily on cross-sectional data [46].

Regarding exposure assessment, Western countries frequently employ geospatial modeling techniques—such as land use regression models—to estimate ambient levels of PM_2.5 and NO₂ [47]. Chinese studies, however, more often depend on environmental monitoring data collected from residential or school settings to evaluate exposure levels [48]. Differences are also evident in the types of pollutants under investigation. Research in Europe and North America typically covers a broader range of pollutants, including PM_2.5, NO₂, and polycyclic aromatic hydrocarbons (PAHs) [49,50]. In contrast, Chinese studies predominantly focus on the neurodevelopmental effects of PM_2.5 and its chemical components on children and adolescents [51].

3.3. Keyword Co-Occurrence and Clustering Analysis

Keyword co-occurrence network analysis identifies thematic relationships by quantifying the frequency with which keywords appear together in the same publication [52]. When two keywords are found simultaneously in the title, abstract, or keyword fields of a single article, they are considered to co-occur. A higher co-occurrence frequency suggests a stronger thematic association between the two keywords, indicating that they likely belong to the same research focus or emerging topic area [53]. Centrality analysis, based on network theory, is employed to measure the significance and influence of a keyword within the co-occurrence network [27]. Keywords with high centrality serve as pivotal nodes connecting various themes and play an essential role in maintaining network integrity and facilitating information flow. By analyzing both keyword frequency and centrality, this study aimed to identify core topics and research hotspots in the field.

Figure 5 is a knowledge map generated using CiteSpace software, showing the keyword co-occurrence network of research on air pollution and the neuropsychology of children and adolescents from 2000 to 2024. The map contains multiple keywords, such as “indoor air pollution”, “nitrogen dioxide”, “oxidative stress”, “particulate matter”, “air quality”, “child development”, etc. These keywords are connected by lines to represent the frequency and relationship of their co-occurrence in relevant research. Through this map, the hotspots and trends of research in this field can be understood intuitively.

Using CiteSpace, a total of 829 keywords extracted from 1441 articles were analyzed. The top 20 keywords ranked by frequency and centrality are presented in

Table 3. Frequency and centrality of high-frequency keywords.

Frequency of High-Frequency Keywords			Centrality of High-Frequency Keywords
No.	Frequency	Keyword	No.	Frequency	Keyword
1	861	air pollution	1	0.11	cardiovascular disease
2	489	environmental exposure	2	0.1	child development
3	468	particulate matter	3	0.09	controlled study
4	368	air pollutant	4	0.07	air pollutants
5	346	air pollutants	5	0.07	ambient air
6	346	controlled study	6	0.07	environmental factor
7	340	major clinical study	7	0.07	disease association
8	298	mental health	8	0.06	indoor air pollution
9	242	cohort analysis	9	0.06	child health
10	236	preschool child	10	0.06	air quality
11	230	atmospheric pollution	11	0.06	air pollutant
12	223	pollution exposure	12	0.06	risk assessment
13	219	prenatal exposure	13	0.05	health hazard
14	216	child health	14	0.05	cohort analysis
15	206	adverse event	15	0.05	health risk
16	198	nitrogen dioxide	16	0.05	attention deficit disorder
17	196	risk factor	17	0.04	central nervous system tumor
18	129	Prenatal exposure delayed effects	18	0.04	case–control studies
19	124	cohort studies	19	0.04	preschool child
20	122	Autism spectrum disorder	20	0.04	brain development

. As shown, “air pollution” ranked first in frequency (861 occurrences), followed by “environmental exposure” (489). Keywords ranked third to tenth in frequency included “particulate matter” (468), “air pollutant” (368), “air pollutants” (346), “controlled study” (346), “major clinical study” (340), “mental health” (298), “cohort analysis” (242), and “preschool child” (236). In terms of centrality, the top ten keywords were “cardiovascular disease” (0.11), “child development” (0.10), “controlled study” (0.09), “air pollutants” (0.07), “ambient air” (0.07), “environmental factor” (0.07), “disease association” (0.07), “indoor air pollution” (0.06), “air quality” (0.06), and “risk assessment” (0.06). These findings indicate that current global research on the effects of air pollution on children and adolescents is focused on several key areas. First, there is a strong emphasis on the direct associations between specific types of air pollutants—particularly particulate matter (PM_2.5 and PM₁₀) and ozone—and their health impacts, including cardiovascular disease and long-term developmental outcomes in children [54,55]. Environmental exposure assessment methods, such as geographic information system tracking and cohort analyses, are commonly applied to quantify both indoor and outdoor air pollution levels and to explore causal links between household factors (e.g., coal burning) and child health outcomes [56].

Moreover, a growing body of research is examining the psychological impacts of air pollution on children and adolescents, with particular attention to how environmental stressors may contribute to anxiety, depression, and other mental health disorders [57,58]. Simultaneously, efforts are underway to refine air quality standards and risk assessment frameworks, aiming to support targeted regional interventions for vulnerable groups such as children and adolescents in order to mitigate the health risks associated with air pollution [59,60].

Keyword clustering analysis, performed using the CiteSpace software, involves grouping all extracted keywords into clusters based on their semantic similarity and co-occurrence patterns [61]. This process transforms unstructured keyword data into structured categories, facilitating the identification of research themes. According to established bibliometric standards, a clustering modularity value (Q value) greater than 0.3 indicates a statistically significant cluster structure, while a mean silhouette score (S value) above 0.7 reflects high clustering reliability. An S value greater than 0.5 is generally considered acceptable for meaningful clustering results [27].

Using CiteSpace version 6.4.R1 and applying the Log-Likelihood Ratio (LLR) algorithm, we conducted a clustering analysis on the keyword co-occurrence network. The resulting visualization is presented in Figure 6. The analysis identified 10 major thematic clusters, labeled as follows: #0 air pollution, #1 school characteristics, #2 global health, #3 study area, #4 prenatal exposure, #5 childhood cancer, #6 mental disorder, #7 autism spectrum disorder, #8 hyperactivity disorder, and #9 perinatal risk factor.

Each colored block in the network map represents a distinct cluster. The overall modularity score of Q = 0.5244 and average silhouette score of S = 0.8015 indicate well-defined inter-cluster separation and high internal consistency, confirming the robustness and reliability of the clustering outcome. Additionally, the dense interconnections among clusters, represented by linking lines in the visualization, suggest strong thematic relationships across keyword groups, highlighting the interdisciplinary and multifaceted nature of research on air pollution and neuropsychological outcomes in children and adolescents.

To further explore population-specific research focuses, the 1441 collected publications were categorized into three thematic groups based on developmental stages: infants, preschool children, and adolescents. The infant-related literature included 306 articles, preschool-related literature comprised 357 articles, and adolescent-related studies totaled 572 articles. As shown in Figure 7, the clustering analysis of keywords related to infants (Q = 0.559, S = 0.8355) revealed ten primary thematic categories: #0 critical windows, #1 leukemia, #2 middle aged, #3 physical activity, #4 asthma, #5 calcitriol, #6 autism, #7 social class, #8 fine particulate matter, and #9 particulate matter. These clusters include a diverse range of topics, including disease outcomes, environmental exposures, social determinants, and health interventions. For instance, leukemia and asthma highlight specific disease burdens in early life, while autism reflects increasing attention to neurodevelopmental disorders. Keywords such as fine particulate matter and particulate matter emphasize the health risks posed by air pollution. The social class cluster explores health disparities related to socioeconomic status, including differences in disease incidence, healthcare access, and health behaviors across social strata.

The cluster labeled critical windows refers to life stages during which environmental exposures can have long-lasting impacts on health and disease development, particularly in early infancy. Interestingly, the presence of middle aged and physical activity within infant-related literature may reflect broader studies that include maternal health or parental behaviors influencing child outcomes. Calcitriol, a vitamin D metabolite, is likely discussed in the context of immune regulation and disease prevention mechanisms during infancy. For the preschool-age group, keyword clustering (Q = 0.5325, S = 0.7966) results identified the following categories: #0 neurodevelopment, #1 particulate matter, #2 Sweden, #3 children, #4 brain-derived neurotrophic factor (BDNF), #5 France, #6 neuroimaging, #7 childhood cancer, #8 pregnancy, and #9 house dust.

Neurodevelopment is the central research theme, including investigations into developmental mechanisms, influencing factors, and their associations with neurological disorders. The cluster brain-derived neurotrophic factor (BDNF) is closely tied to neurodevelopment, as BDNF plays a critical role in neuronal survival, synaptic plasticity, and learning processes, and is often studied in relation to neurodevelopmental conditions.

Neuroimaging provides structural and functional insights into brain development during early childhood and is increasingly used to examine the impacts of environmental exposures. Particulate matter and house dust highlight environmental risk factors, reflecting growing interest in how indoor and ambient pollutants affect cognitive and behavioral development.

Geographic clusters such as Sweden and France suggest these countries have contributed distinctive research in this area. Keywords like children and pregnancy reflect the holistic view of child health across the life course—from prenatal influences to early interventions and preventive strategies in childhood.

For adolescents, keyword clusters (Q = 0.5112, S = 0.8004) included: #0 depression, #1 green space, #2 weather, #3 childhood cancer, #4 brain development, #5 urbanization, #6 autism, #7 schools, #8 children, and #9 incidence.

Depression and autism highlight a strong focus on adolescent mental health, with research addressing pathogenesis, risk factors, treatment strategies, and preventive measures. Green space investigates the relationship between exposure to natural environments and psychological as well as physical well-being in adolescents. The urbanization cluster captures concerns regarding the health impacts of rapid urban development, lifestyle transitions, and shifts in disease patterns.

Weather reflects studies examining the influence of meteorological conditions—including extreme weather events—on physical and mental health outcomes. Clusters like children and childhood cancer indicate continued concern for pediatric health within the adolescent age group. Schools as a keyword points to the influence of educational environments on adolescent development, while brain development is linked to ongoing neurological maturation processes during adolescence. Lastly, incidence likely relates to epidemiological research examining trends and prevalence of health conditions in this population.

3.4. Burst Keyword Detection and Temporal Evolution

Keyword burst analysis is an effective approach to identify terms that appear suddenly and with rapidly increasing frequency during specific periods, indicating emerging research hotspots or topics receiving heightened attention in the field [53]. In order to understand the development trajectory of studies on the neuro-psychological effects of air pollution on children and adolescents from 2000 to 2024, we conducted a keyword emergence detection based on the analysis setting of γ[0,1] = 1, and set the minimum duration to 1. The results identified 15 burst keywords (see

Table 4. Top 15 keywords with the strongest citation burst.

Keywords	Year	Strength	Begin	End	2000–2024 *
adverse effects	2005	21.4	2010	2017	▂▂▂▂▂▂▂▂▂▂▃▃▃▃▃▃▃▃▂▂▂▂▂▂▂
preschool child	2003	18.77	2006	2019	▂▂▂▂▂▂▃▃▃▃▃▃▃▃▃▃▃▃▃▃▂▂▂▂▂
environmental exposure	2003	18.62	2003	2016	▂▂▂▃▃▃▃▃▃▃▃▃▃▃▃▃▃▂▂▂▂▂▂▂▂
traffic-related air pollution	2013	15.56	2013	2020	▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃▃▃▃▃▃▂▂▂▂
disease association	2009	14.23	2009	2020	▂▂▂▂▂▂▂▂▂▃▃▃▃▃▃▃▃▃▃▃▃▂▂▂▂
environmental health	2002	13.35	2002	2015	▂▂▃▃▃▃▃▃▃▃▃▃▃▃▃▃▂▂▂▂▂▂▂▂▂
attention deficit disorder	2011	12.71	2011	2020	▂▂▂▂▂▂▂▂▂▂▂▃▃▃▃▃▃▃▃▃▃▂▂▂▂
pregnancy	2021	11.17	2021	2023	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃▂
central nervous system	2001	10.71	2001	2020	▂▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▂▂▂▂
Autism spectrum disorder	2014	9.98	2015	2020	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃▃▃▃▂▂▂▂
adolescent	2021	9.31	2023	2024	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃
social status	2009	8.64	2019	2020	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▂▂▂▂
nervous system disorder	2014	8.58	2014	2019	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▃▃▃▃▂▂▂▂▂
cognition	2021	7.55	2022	2023	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▂
children	2021	7.23	2022	2023	▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▃▃▂

* The red indicate that the keyword is in an “explosive” phase during this period; the blue indicate that the keyword is in a “normal” or “non-explosive” state during this period.

). In the keyword burst map, “Strength” denotes the intensity of the burst, with higher values indicating stronger prominence and popularity of the term. “Begin” and “End” represent the time period during which the burst occurred, illustrating the temporal dynamics of research focus shifts. Red line segments mark the start and end of the burst, representing the duration during which the keyword remained a research hotspot or frontier (mean burst duration 7.2 years, median burst duration 7 years).

From the keyword burst visualization, the most prominent burst terms include “adverse effects”, “preschool child”, “environment exposure”, and “traffic-related air pollution”. Among them, “adverse effects” exhibited the highest burst strength of 21.4, occurring from 2010 to 2017, indicating intense research activity during this period on the negative impacts of air pollution on neurodevelopment in children and adolescents. For instance, studies have shown that adolescents living in areas with higher PM_2.5 exposure have lower performance IQ (PIQ) scores, and this adverse effect is more significant among families with low economic conditions and males [62]. Furthermore, a mother’s exposure to outdoor air pollution during pregnancy may have adverse effects on behavioral problems in childhood [63].

The emergent intensity of “preschool child” was 18.77, and the duration was from 2006 to 2019, indicating that the health issues of preschool children have long received attention. In addition, the key words with emergent intensity exceeding 10 also include “central nervous system” and “pregnancy”. Among them, “pregnancy” began to attract attention in 2021 and continued until 2023, with an emergent intensity of 11.17, reflecting the increased concern over the health of pregnancy and the impact of environmental exposure during pregnancy in recent years. Although the emergence intensity of “adolescent” is relatively low, it has gradually become a research hotspot from 2023 to 2024, indicating that adolescent health will become an important research direction in the future. In addition, neuropsychological disorders in children and adolescents such as attention deficit disorder and autism spectrum disorder have also received extensive attention. Some scholars have studied the association between exposure to air pollutants such as PM_2.5 and NO₂ during pregnancy and the first year of an infant’s birth and behaviors related to autism spectrum disorder in children [64].

Combined with the analysis of the thematic distribution map (Figure 8), this map presents the evolution trend of themes from two dimensions: “degree of development” and “degree of relevance”, where the horizontal axis represents the degree of relevance and the vertical axis represents the degree of development. The distribution of different topics is presented in the figure, and the core topics, emerging topics and fundamental topics in the research are identified. It can be clearly seen from the figure that the themes of “air-pollution” and “children” are in relatively important positions, indicating that the research focus lies in exploring the impact of air pollution on children and adolescents.

The key words “behavior”, “mental-health”, “psychiatric disorders”, “cognitive” are concentrated in the medium-high correlation degree and medium-high development degree areas, indicating a high level of attention to the mental health status of children and adolescents under air pollution, covering research in aspects such as mental illness, cognitive function, and behavioral disorders. The key words “PM_2.5”, “fine particulate matter”, and “NO₂” have a certain distribution in the figure, indicating that the research on the neuropsychological effects of different air pollutants on children and adolescents is highly popular. Words “exposure”, “health”, and “risk” appear in the fourth quadrant, indicating that most studies involve assessing the level of exposure of children and adolescents to air pollution and the corresponding health risks. The terms “prenatal exposure” and “pregnancy” have a relatively high degree of correlation in the figure, indicating that a large number of studies have focused on the long-term effects of exposure to air pollution during pregnancy on the neuropsychological development of the fetus. In addition, The key words “fine particulate matter”, “cohort”, “association”, and “PM_2.5” are located in the “Emerging or Declining Themes”. The area indicates that the research on the connection between fine particulate matter and neuropsychology may be an emerging field, with its research popularity either on the rise or still developing. Chen [65] identified research hotspots in the field of air pollution control, such as PM_2.5 concentration, through keyword co-occurrence analysis.

3.5. Author Collaboration Network

From 2000 to 2024, numerous scholars have published papers on the relationship between air pollution and the neurocognitive and psychological health of children and adolescents. Based on 843 articles retrieved from the Web of Science Core Collection on the impact of air pollution on the neurocognitive and psychological health of children and adolescents, the publication data of the top 10 most prolific authors were analyzed (see

Table 5. Top 10 core authors in NEAPCA research field.

Author	Number	Institute	Country
Sunyer J	35	Barcelona Institute for Global Health	Spain
Guxens M	32	Barcelona Institute for Global Health	Spain
Schwartz J	24	Harvard T.H. Chan School of Public Health	USA
Mcconnell R	22	University of Southern California	USA
Chen JC	20	University of Southern California	USA
Dadvand P	18	Barcelona Institute for Global Health	Spain
Forns J	17	Barcelona Institute for Global Health	Spain
Ibarluzea J	16	University of Basque Country	Spain
Nieuwenhuijsen M	16	Barcelona Institute for Global Health	Spain
Kloog I	15	Icahn School of Medicine at Mount Sinai	USA

). The results showed that Dr. Sunyer J from Spain had the highest number of publications (35 articles), ranking first. Dr. Guxens M, also from the Barcelona Institute for Global Health (ISGlobal), ranked second with 32 publications. Dr. Schwartz J from the United States ranked third with 24 publications. The fourth and fifth positions were both held by scholars from the University of Southern California, namely Dr. McConnell R (22 articles) and Dr. Chen JC (20 articles). The sixth to ninth positions were all occupied by Spanish scholars: Dr. Dadvand P (18 articles), Dr. Forns J (17 articles), and Dr. Nieuwenhuijsen M (16 articles), all of whom are affiliated with ISGlobal. In terms of institutional distribution, six scholars from ISGlobal were among the top 10, with a total of 134 publications, accounting for 62% of the total publications by the top 10 authors (215 articles). This indicates that scholars within ISGlobal have a close collaboration, forming a highly productive research team.

In other institutions, Harvard University was represented by a single scholar, Dr. Schwartz J (24 articles), while the University of Southern California contributed 42 articles through Dr. McConnell R and Dr. Chen JC. The University of the Basque Country (16 articles) and the Icahn School of Medicine at Mount Sinai (15 articles) were each represented by a single scholar. Although China ranks second in terms of publication volume in this research field, author collaboration is relatively dispersed, and most studies are short-term. The author collaboration network was visualized using VOSviewer, as shown in Figure 9. The colors in the figure represent different thematic clusters, with each color corresponding to a specific research theme or area. Nodes of different colors represent researchers and their respective research themes, and the size of the nodes reflects the academic influence of the researchers. The figure shows that Dr. Sunyer J, Dr. McConnell R, and Dr. Schwartz J are key researchers in this field, with larger nodes indicating their significant influence in the academic community. The lines connecting the nodes represent collaborative relationships between researchers, and the presence of cross-cluster connections indicates some degree of collaboration or association between different research themes. Several relatively dense clusters are also visible in the figure, suggesting that researchers within these thematic areas have close collaborations. Additionally, some scattered nodes in the peripheral regions may represent independent researchers or smaller research teams with limited influence. Overall, in the author collaboration network of current research on the relationship between air pollution and the neurocognitive and psychological health of children and adolescents, most scholars primarily collaborate with researchers within their own institutions and have limited collaboration with other thematic research teams.

3.6. Co-Citation of References

Co-citation of references refers to the phenomenon where two or more early publications are simultaneously cited in the reference lists of one or more subsequent publications [66]. In CiteSpace, by selecting “reference” as the node type, LLR clustering analysis was performed on the cited references. According to the automatic clustering results, the modularity value Q was 0.7868 (greater than 0.3), and the average silhouette value S was 0.9322 (greater than 0.7), indicating that the clustering effect was significant and the results were highly reliable. The clustering analysis revealed the cluster characteristics of research on air pollution and the neurocognitive and psychological health of children and adolescents. The top 10 key thematic clusters included: #0 autism spectrum disorder, #1 systematic review, #2 adverse effect, #3 intellectual disability, #4 environmental noise, #5 mental health crises, #6 utero exposure, #7 neurodevelopmental disorder, #8 inma cohort, and #9 critical proton mr. Clustered references and their related bibliographic information are shown in

Table 6. Clustered references and related bibliographic information.

#0 autism spectrum disorder	#5 mental health crises
Volk HE, 2013 [67] (DOI: 10.1001/jamapsychiatry.2013.266) Raz R, 2015 [68] (DOI: 10.1289/ehp.1408133)	Lopuszanska U, 2020 [69] (DOI: 10.1097/WNN.0000000000000235) Zundel CG, 2022 [70] (DOI: 10.1016/j.neuro.2022.10.011)
#1 systematic review	#6 utero exposure
Dadvand P, 2017 [71] (DOI: 10.1289/EHP694) Markevych I, 2018 [72] (DOI: 10.1016/j.scitotenv.2018.06.167)	Edwards SC, 2010 [73] (DOI: 10.1289/ehp.0901070) Brook, R. D, 2010 [74] (DOI: 10.1161/CIR.0b013e3181dbece1)
#2 adverse effect	#7 neurodevelopmental disorder
Sunyer J, 2015 [22] (DOI: 10.1371/journal.pmed.1001792) Chiu YHM, 2016 [75] (DOI: 10.1016/j.envint.2015.11.010)	Raz R, 2018 [76] (DOI: 10.1093/aje/kwx294) Calderón-Garcidueñas, L, 2022 [77] (DOI: 10.1021/acs.est.1c04706)
#3 intellectual disability	#8 inma cohort
Dutheil F, 2021 [78] (DOI: 10.1016/j.envpol.2021.116856) Roberts S, 2019 [79] (DOI: 10.1016/j.psychres.2018.12.050)	Guedes AMFM, 2003 [80] (DOI: 10.1016/S0043-1354(03)00178-7) Martínez NS, 2003 [81] (DOI: 10.1016/S0304-3894(03)00207-3)
#4 environmental noise	#9 critical proton mr
Peterson BS, 2015 [82] (DOI: 10.1001/jamapsychiatry.2015.57) Forns J, 2016 [83] (DOI: 10.1289/ehp.1409449)	Calderón-Garcidueñas L, 2012 [84] (DOI: 10.3389/fpsyg.2012.00217) Jerrett M, 2014 [85] (DOI: 10.1186/1476-069X-13-49)

.

The timeline map shown in Figure 10 illustrates the main changes in research content of specific topics over time, reflecting research trends in different periods. The cluster timeline map integrates the characteristics of both the cluster map and the timeline map, not only presenting the results of the cluster map but also showing the evolutionary process of the timeline map. This allows for a more detailed analysis of the evolutionary characteristics of each cluster. As shown in Figure 10, cluster research in this field began around 2009, with research prior to 2009 being relatively scattered.

Early Research (2009–2015): The focus was primarily on autism spectrum disorder, utero exposure, and critical proton magnetic resonance. Studies indicated that air pollution exposure during the first year after birth was most significantly associated with autism risk, while exposure during the late pregnancy period had the strongest association with autism risk. Therefore, pregnancy and the early postnatal period were considered critical periods for the impact of air pollution on autism risk [67,68].

Mid-Term Development (2016–2019): The number of systematic reviews increased significantly. Research began to focus on the relationship between neurodevelopmental disorders and environmental noise, as well as other adverse factors, and gradually expanded to different developmental stages of children and adolescents. Green spaces were found to positively impact children’s attention through multiple pathways, including promoting physical health, reducing air pollution and noise exposure, and increasing the richness of microbial environments [71]. Additionally, green spaces may indirectly promote children’s cognitive development by enhancing immune regulation and alleviating psychological stress.

Recent Research (2020–2024): Intellectual disability, mental health issues, and large-scale cohort studies have gradually become core topics in the field of air pollution and children’s neurocognitive health. For example, a study on children in Mexico City found that air pollution had significant negative impacts on their cognition and behavior, particularly among children of low socioeconomic status [84]. Children chronically exposed to air pollution exhibited symptoms of neuroinflammation, neurodegenerative changes, and cognitive deficits. Another cohort study based in London, UK, showed that air pollution exposure during late childhood had long-term effects on depressive symptoms and conduct disorders in adolescence [79].

3.7. International Collaboration Network Analysis

The world collaboration map generated by Bibliometrix (as shown in Figure 11) indicates that the United States has the darkest color, followed by China. The intensity of the color reflects the publication output of each country in the field of research on air pollution and the neurocognitive and psychological health of children and adolescents, thereby confirming the previous conclusion regarding national publication numbers, namely that the United States has the highest publication number, with China in second place. The data on the frequency of international cooperation reveal that the global scientific collaboration network exhibits a significant centralized structure coexisting with regional fragmentation, which can be intuitively observed from the connecting lines in the figure. Regional clusters and fractures are evident, with North America forming a radiation circle centered on the United States (a U.S.–Canada–Mexico triangle), and Europe presenting a multilateral mesh structure. However, cooperation in the Asia-Pacific region shows a unipolar trend, with China’s collaboration in the region highly dependent on Australia, and no balanced multilateral cooperation network has been established. The China–Japan–South Korea triangle is almost completely developed countries, with the total cooperation number of the United States, the United Kingdom, and the Netherlands alone accounting for 53.7% of the global cooperation number. In contrast, high-pollution regions such as India, Nigeria, the Democratic Republic of the Congo, and Zambia have cooperation frequencies of less than one time, highlighting the severe imbalance in the global allocation of scientific research resources. Israel has 17 cooperation frequencies with the United States, far exceeding other countries in the Middle East. Influenced by cultural factors, Saudi Arabia mainly cooperates with Islamic countries such as Egypt and Pakistan. Cooperation among Middle Eastern countries is extremely rare (only 2 times between Saudi Arabia and Egypt), and political factors significantly hinder collaboration in health research in this region. African countries are mostly in a “passive cooperation” state (e.g., Kenya–United Kingdom 1 time), with few autonomous and internal collaborations. This phenomenon reveals a serious inequality, that is, the regions with the heaviest burden of air pollution-related diseases have the weakest research capabilities.

Figure 12 presents a Sankey diagram illustrating the research collaboration network among different countries, authors, and institutions in the field of air pollution and the neurocognitive and psychological health of children and adolescents. The left side of the diagram represents countries (AU_CO), the middle section represents authors (AU), and the right side represents universities (AU_UN). The Sankey diagram visually depicts the cooperative relationships and their strengths among these entities through differently colored and sized flow lines. The diagram clearly shows that the United States and Spain play dominant roles in this research field, not only in terms of the number of participating authors and universities but also through extensive collaborations with other countries and regions.

3.8. Overlay of Dual Maps Analysis

The overlay of dual maps is one of the core visualization functions of CiteSpace software, primarily used to reveal the macroscopic patterns of knowledge flow and connectivity among disciplines [95]. The dual map consists of two main parts: the global discipline distribution map and the local discipline distribution map of the field, with the global discipline distribution map serving as the base map. The dual map overlay spectrum is composed of three parts. The first part includes the citing journal discipline distribution map (application field) on the left and the cited journal discipline distribution map (knowledge base) on the right. The second part is the local discipline distribution map of the field generated from the journal information associated with the analysis object, which shows the relative position of the field in the global discipline map. The third part consists of the colored curves between the two, with the direction, thickness, and color density of the curves indicating the path, intensity, and activity of knowledge transfer, respectively.

As shown in Figure 13, the arc section displays the knowledge flow path map of global research on the association between air pollution and the neurocognitive and psychological health of children and adolescents. On the global discipline map in Figure 13, research on the association between air pollution and the neurocognitive and psychological health of children and adolescents mainly corresponds to three clusters: “VETERINARY, ANIMAL, SCIENCE”, “MEDICINE, MEDICAL, CLINICAL” and “MOLECULAR, BIOLOGY, IMMUNOLOGY”. Research in the “VETERINARY, ANIMAL, SCIENCE” cluster draws its knowledge base from the “ENVIRONMENT, TOXICOLOGY, NUTRITION” and “MOLECULAR, BIOLOGY, GENETICS” clusters on the right. In contrast, research in the “MEDICINE, MEDICAL, CLINICAL” cluster primarily derives its knowledge base from the “ENVIRONMENT, TOXICOLOGY, NUTRITION” and “HEALTH, NURSING, MEDICINE” clusters.

The dual map overlay intuitively demonstrates the knowledge connections and flow in the field of air pollution and children’s neurocognitive and psychological health research but does not provide detailed information on high-impact journals. To address this limitation, the journal network map provided by VOSviewer software was utilized to vividly depict the research dynamics in this field, as shown in Figure 14. In addition, as indicated in

Table 7. Top 10 Journals with the most published articles.

Journals	Documents	Average Citations per Article	Total Link Strength	Rate%
Environmental research	109	34	44,581	7.56%
Environment international	59	38	27,081	4.09%
Environmental pollution	28	26	13,720	1.94%
Environmental health perspectives	24	88	11,856	1.66%
Ecotoxicology and environmental safety	16	14	8032	1.11%
Environmental health	15	19	7545	1.04%
Environmental science and Pollution research	13	24	6565	0.90%
Bmc public health	11	14	5577	0.76%
Epidemiology	11	85	5577	0.76%
Bmj open	10	17	5080	0.69%

, the top ten journals account for 20.54% of the total publications in the field of air pollution and the neurocognitive and psychological health of children and adolescents. Among them, Environmental Research ranks first, accounting for 7.56%; followed by Environment International and Environmental Pollution, respectively, accounting for 4.09% and 1.94%. Additionally, Environmental Health Perspectives and Ecotoxicology and Environmental Safety rank fourth and fifth, respectively, accounting for 1.66% and 1.11%. As can be seen from the table, the relationship between the number of publications and the average influence per article is not a simple positive correlation. Some high-output journals show medium influence, while some journals with a smaller number of publications achieve a high average influence per article. Overall, the high-value journals in the field of air pollution and the neurocognitive and psychological health of children and adolescents are mainly concentrated in the areas of environmental science, toxicology, public health, epidemiology, and general medicine and nursing, which is consistent with the conclusions drawn from the discipline analysis. The number of publications and citations of a journal to some extent reflects its influence in the academic community.

4. Conclusions

This study employed bibliometric tools such as CiteSpace and VOSviewer to systematically analyze the literature from the past 25 years (2000–2024) related to air pollution and its neuropsychological impacts on children and adolescents. Key dimensions analysis included publication number, subject and journal distribution, leading contributors, and keyword clusters. Based on the generated visualizations and data interpretation, we specifically address the seven research questions proposed in the Introduction and draw the following conclusions:

(1)

Research question 1: Research scale and trajectory

Our analysis shows NEAPCA has lower research intensity than more mature fields. For example, Web of Science searches indicate research on “air pollution and children’s respiratory health” is roughly 3 times that on “air pollution and children’s neurodevelopment” (ratio ~3:1). To narrow this gap, NEAPCA can adopt proven strategies from these fields: Build specialized research alliances to coordinate plans and share data; Secure targeted funding for longitudinal cohort studies. Slow development stems from interdisciplinary complexity (environmental science, pediatrics, neuropsychology) and challenges like inaccurate exposure assessment and scarce long-term cohort studies. We propose future research should employ integrated approaches combining advanced neuroimaging and multi-omics to elucidate mechanisms and establish an international multi-center cohort network with harmonized exposure and outcome assessment protocols to improve longitudinal data quality and coverage.

(2)

Research question 2: Core topics and keywords

Three core themes dominate: (a) air pollution’s effects on children’s cognition, behavior, neurodevelopmental disorders (e.g., ADHD) and brain structure; (b) critical exposure pathways (e.g., inhalation) and windows (e.g., prenatal, school-age); (c) mechanisms (oxidative stress, inflammation) and interventions (improving air quality).

(3)

Research question 3: Leading scholars and collaboration

Core influential scholars include Sunyer J, McConnell R, Guxens M, and Schwartz J. However, collaboration networks are fragmented—most focus on intra-institutional or country cooperation, with limited cross-team exchange.

(4)

Research question 4: Disciplinary characteristics and integration

Through searching relevant literature, it is found that there are relatively few studies investigating air pollution and the neuropsychology of children and adolescents simultaneously; notably, this field—interdisciplinary in nature, involving environmental science, pediatrics, and neuropsychology—lacks deep integration, with most studies being single-discipline-led, which ultimately hinders its progress.

(5)

Research question 5: Geographic patterns and hotspots

Research concentrates in high-income regions: (a) North America (U.S. leads in publications, focusing on cohort studies); (b) Europe (Spain, UK, the Netherlands—Spain excels in vulnerable population research). Lower-middle income countries with high pollution have low research output, creating imbalance.

(6)

Research question 6: Leading countries/institutions and collaboration

In this field, regarding publication volume, the United States ranks first, and China ranks second; in terms of academic influence, Spanish institutions (e.g., ISGlobal) are more prominent; for collaboration, leading countries such as the United States, Spain, and China mainly conduct cooperation within their respective regions, while cross-continental partnerships are relatively rare.

(7)

Research question 7: Core journals

In the field of research on the association between neuro-psychological health in children and adolescents and air pollution, Environmental Health Perspectives, Epidemiology, Environment International, and Environmental Research are the core carriers of highly cited literature. Environmental Health Perspectives conducts prospective cohort studies to explore the long-term effects of pollutants on the critical period of neurodevelopment; Epidemiology focuses on innovative epidemiological methods to enhance the accuracy of exposure measurement and the rigor of causal inference; Environment International combines the combined exposure effects of multiple pollutants and molecular mechanisms to build a bridge between macroscopic correlation and microscopic mechanism; Environmental Research focuses on studies of specific populations and scenarios, providing guidance for practical protection.

5. Outlook

The neuropsychological risks of air pollution in children and adolescents are multifaceted and span multiple developmental stages. This study, based on 1441 publications from 2000 to 2024, reveals the evolution and emerging focuses of research in this domain through comprehensive visual analysis. Future research should aim to build a full-chain framework of “exposure–mechanism–intervention” by integrating longitudinal data with advanced technologies. Given the complex interplay of biological mechanisms and social environmental factors, the value of this research area is increasingly recognized. We recommend five key directions for future development:

Firstly, deepening mechanistic exploration: transition from macroscopic correlations to microscopic pathogenic mechanisms. Keywords clustering (e.g., #4 prenatal exposure, #6 mental disorder, #7 autism spectrum disorder) and emerging terms (e.g., adverse effects, central nervous system, cognition) indicate that current research has preliminarily revealed the correlations between pollutants such as PM_2.5 and NO₂ and neurodevelopmental disorders (e.g., ADHD, autism). However, the underlying mechanisms remain largely hypothetical. Future studies should focus on pathways such as oxidative stress, neuroinflammation, and brain structural changes, utilizing multi-omics technologies including neuroimaging, single-cell transcriptomics, and metabolomics to elucidate the impact mechanisms of pollutants on the brain from the molecular to functional levels, thereby facilitating the construction of a closed causal loop.

Secondly, precision in population stratification and identification of critical exposure windows. Thematic mapping and age-specific clustering analysis (infant, preschool, and adolescent) demonstrate significant differences in exposure effects across different developmental stages, with keywords such as “pregnancy”, “prenatal exposure”, “preschool child”, and “adolescent” emerging as high-frequency terms. Research should enhance the sensitivity to exposure windows, particularly during the mid-to-late pregnancy, the first year after birth, and the peak periods of neural plasticity in adolescence, to clarify the long-term impacts of air pollution on brain structure and psychological behavior at different stages.

Thirdly, insufficient Research on Pollutant Types and Interactions. Keyword co-occurrence maps (e.g., particulate matter, NO₂, ozone) are predominantly focused on traditional pollutants, while VOSviewer analysis reveals a lack of attention to co-exposure of multiple pollutants and specific source pollution (e.g., indoor combustion, traffic exhaust). It is recommended that future studies develop composite pollution exposure models to investigate the joint effects of different pollutants and their dose–response relationships at varying exposure concentrations.

Fourthly, need for an empirical closed loop in policy intervention and health impact assessment. Literature emergence analysis indicates that keywords such as “green space” and “urbanization” have only emerged in the past two years, with virtually no empirical literature on the “policy intervention–health benefit” pathway, suggesting that the policy translation value has been severely underestimated. Despite a clear academic consensus on the hazards of air pollution, empirical research at the policy level remains extremely scarce. It is suggested that environmental policies such as urban vehicle control, coal substitution, and green space planning be incorporated into exposure–outcome models to assess their long-term neurocognitive benefits for specific populations.

Finally, imbalanced global collaboration network: need to enhance research capacity in low- and middle-income countries. International collaboration mapping and frequency data show that the United States and China have collaborated 37 times, while China has no substantial collaboration nodes with the Middle East or Africa. Countries such as India, Zambia, and Nigeria have collaboration frequencies of less than one, revealing a structural imbalance of “high pollution–weak research capacity”. The United States and European countries (especially Spain) dominate the global collaboration network. Although China ranks second in publication number, its collaboration distribution remains inward-focused. Regions with high pollution burdens, such as Africa and the Middle East, have weak research capabilities. Future research should focus on promoting the establishment of a “North–South integration” cooperation mechanism centered on China and the United States, with a particular emphasis on strengthening research and intervention for vulnerable children in low- and middle-income countries. To effectively implement this mechanism, it is suggested to draw on the operational model of the “1.5 Degree Active Health International Alliance”, which was initiated by international authoritative institutions such as the World Health Organization (WHO), the United Nations Environment Programme (UNEP), and the United Nations Children’s Fund (UNICEF). On this basis, it is advisable to further incorporate leading global research institutions in child neurology and environmental science centers to participate and establish a multilateral collaboration framework that integrates policy formulation, scientific research, and public welfare practice, providing systematic support for the “North–South integration” mechanism.