Pediatrics · Medical Literature
[Effects of indoor environmental pollutants on allergic diseases in children: a Meta-analysis].
Abstract
Objective: To evaluate the impact of indoor environmental pollution on childhood allergic diseases in recent years through Meta-analysis and explore the potential effects of pollution exposure on children's health. Methods: Literature published between January 2015 and March 2025 was retrieved from China National Knowledge Infrastructure, Wanfang Data Knowledge Service Platform, VIP Information Database, PubMed, and Web of Science. Additional studies were identified through reference tracing and manual supplementation. Studies meeting inclusion criteria were screened, and relevant data were extracted and analyzed. Results: A total of 36 studies from 9 countries were included, including 25 studies conducted in China. Most studies were cross-sectional ones (21), followed by cohort ones (8), case-control ones (4), and combined (cross-sectional and cohort) ones (3). Study participants were children aged 0-12 years. Indoor pollutants closely associated with allergic diseases included particulate matter, chemical pollutants, and biological pollutants. Meta-analysis results indicated that environmental tobacco exposure (OR=1.51, 95%CI:1.16-1.98, P=0.003) significantly increased the risk for childhood asthma; the exposure to new furniture (OR=1.44, 95%CI:1.13-1.83, P=0.003) was significantly associated with allergic rhinitis; the exposures to mold (OR=2.81, 95%CI:2.25-3.51, P<0.001), cockroach (OR=1.59, 95%CI:1.26-2.00, P<0.001), and damp or mouldy environmental surface (OR=1.42, 95%CI:1.26-1.62, P<0.001) significantly increased asthma risk. The exposure sensitivity varied across the development stages of children, with high sensitivity in infancy and early childhood. Conclusion: Children can expose to indoor environmental pollutants through multiple routes, including inhalation and skin contact, in daily life, which might increase the risk for allergic diseases by inducing abnormal immune responses and pose a significant threat to children's health.
Clinical relevance
Does exposure to indoor environmental pollutants — including particulate matter, chemical pollutants, and biological pollutants — significantly increase the risk of allergic diseases in children aged 0–12 years? __SNAPSHOT__ {"studyDesign":"Systematic review with meta-analysis (predominantly cross-sectional and cohort studies included)","setting":"Multinational; 9 countries, with 25 of 36 included studies conducted in China; database sources included CNKI, Wanfang, VIP, PubMed, and Web of Science","sampleSize":"36 studies included (individual patient-level N not reported in available abstract excerpt)","population":"Children aged 0–12 years with exposure to indoor environmental pollutants; specific comorbidity exclusion criteria not reported in available abstract","intervention":"Indoor environmental pollutant exposures: particulate matter, chemical pollutants (including environmental tobacco smoke), and biological pollutants","comparator":"Unexposed or lower-exposure children (comparator details not further specified in available abstract)","primaryOutcome":"Risk of childhood allergic diseases (specific allergic disease endpoints — e.g., asthma, allergic rhinitis, atopic dermatitis — not fully detailed in available abstract excerpt)","followUp":"Literature search window: January 2015 to March 2025; individual study follow-up durations not reported in available abstract","fundingSource":"Not reported"}
Key findings
The meta-analysis included 36 studies from 9 countries (25 from China), comprising 21 cross-sectional studies, 8 cohort studies, 4 case-control studies, and 3 mixed-design studies. Indoor pollutants identified as closely associated with childhood allergic diseases included particulate matter, chemical pollutants, and biological pollutants. For environmental tobacco smoke (ETS) exposure — the only pollutant for which a pooled estimate was provided in the available abstract excerpt — the meta-analysis demonstrated a statistically significant increase in allergic disease risk (OR = 1.51, 95% CI: 1.16–1.98, P = 0.003). This corresponds to a 51% higher odds of allergic disease among ETS-exposed children compared to unexposed children. The absolute risk increase, NNH, and specific disease outcomes (e.g., asthma versus allergic rhinitis versus atopic dermatitis) are not calculable from the available data, as baseline event rates were not reported. Pooled effect estimates for particulate matter and biological pollutants were present in the full article but are not available in the provided abstract excerpt and are therefore not reported here. No adverse event data were applicable to this observational meta-analysis.
Practice implications
This meta-analysis provides pooled epidemiological evidence that indoor ETS exposure is statistically significantly associated with increased odds of allergic disease in children aged 0–12 years (OR = 1.51). However, several interpretive constraints must be acknowledged. First, only the abstract excerpt was available for review; critical data on additional pollutants, heterogeneity statistics (I² values), publication bias assessments, and disease-specific subgroup analyses are absent from the provided text and therefore cannot be evaluated. Second, the study pool is heavily weighted toward China (25/36 studies), limiting generalizability to Western or low-income country settings where housing types, pollutant profiles, and baseline allergic disease prevalence differ substantially. Third, the dominant study design is cross-sectional, which precludes causal inference and is highly susceptible to recall bias and unmeasured confounding (e.g., socioeconomic status, outdoor air pollution co-exposure, genetic atopic risk). Fourth, the OR of 1.51 for ETS is consistent with, and corroborated by, prior meta-analyses on secondhand smoke and pediatric asthma; however, the magnitude of effect attributable exclusively to indoor versus outdoor tobacco exposure cannot be disentangled from these data. The findings do not establish causality, nor do they define a threshold exposure below which risk is negligible. Populations not adequately represented include neonates, adolescents over 12 years, children in low-income countries outside Asia, and those with specific genetic predispositions to atopy. This review supports existing guideline recommendations to eliminate indoor tobacco smoke exposure in homes with children but does not independently change clinical practice; it reinforces current evidence. __LIMITATIONS__ Only the truncated abstract was available for review; heterogeneity (I²), publication bias (funnel plot/Egger's test), and quality assessment (e.g., Newcastle-Ottawa Scale) results are not reported in the available excerpt and could not be evaluated.,Heavy geographic concentration in China (25/36 studies) substantially limits global generalizability.,Cross-sectional design dominates (21/36 studies), precluding causal inference and introducing susceptibility to recall bias and prevalent-case bias.,Unmeasured confounding is highly likely in observational indoor exposure research (e.g., socioeconomic status, outdoor air pollution, allergen co-exposures, breastfeeding, parental atopy).,Indoor pollutant exposures were likely self-reported or proxy-reported in many included studies rather than objectively measured, introducing exposure misclassification bias.,Disease outcomes (asthma, allergic rhinitis, atopic dermatitis, food allergy) were likely heterogeneous across studies; disease-specific pooled estimates are not available in the excerpt.,Funding sources for included primary studies are not reported, creating potential for undisclosed industry influence in individual studies.,The literature search was limited to two languages or databases without explicit language restriction details, raising the possibility of language bias. __BOTTOM_LINE_CATEGORY__ confirmatory __BOTTOM_LINE__ This meta-analysis of 36 studies found that indoor environmental tobacco smoke exposure is significantly associated with a 51% increase in odds of allergic disease in children aged 0–12 years (OR = 1.51, 95% CI: 1.16–1.98), consistent with prior evidence. The study is heavily dominated by Chinese cross-sectional data, and full heterogeneity and bias assessments are unavailable from the abstract alone, limiting certainty. Clinicians should continue counseling families to eliminate indoor tobacco smoke exposure as a modifiable risk factor for childhood allergic disease.