Key Findings
- Purpose
To examine whether higher ambient concentrations of criteria air pollutants were associated with increased odds of abnormal pulmonary function among children and young adults with sickle cell disease (SCD). - Population (Model)
Retrospective observational study using 10 years of data (2010–2019) from 65 children and young adults with SCD, ages 5–19 years, who resided in Jefferson County, Alabama, and had at least one pulmonary function test (PFT) at Children’s Hospital of Alabama. The cohort included HbSS (75.4%), HbSβ⁰-thalassemia (12.3%), HbSC (9.2%), and HbSβ⁺-thalassemia (3.1%); 84.6% had asthma and 81.5% were receiving SCD-modifying therapy. Analyses considered sex, age, SCD genotype, asthma, and SCD-modifying therapies. - Headline Result
Among the criteria air pollutants evaluated, higher monthly average nitrogen dioxide (NO₂) concentrations were significantly associated with abnormal forced expiratory volume in 1 second (FEV₁). In unadjusted analyses, each 1 parts-per-billion (ppb) increase in monthly average NO₂ was associated with 53% higher odds of an abnormal FEV₁ result (odds ratio [OR], 1.53; 95% confidence interval [CI], 1.01–2.33; P = .047). The adjusted association was not statistically significant (OR, 1.59; 95% CI, 0.95–2.69; P = .077). Obstruction indices—FEV₁/forced vital capacity (FVC) and forced expiratory flow at 25%–75% of FVC (FEF₂₅–₇₅%)—were normal in all participants, but FEV₁ and FVC were frequently reduced; the NO₂ association was observed for FEV₁. - Why It Matters
Pulmonary complications are an important source of morbidity in SCD, and asthma and acute chest syndrome can contribute to impaired lung function. This study provides preliminary evidence that higher monthly average NO₂ concentrations may be associated with abnormal FEV₁ in children and young adults with SCD. The findings support further investigation of air pollution as a potentially modifiable environmental exposure, particularly among individuals with existing respiratory vulnerability. The observational design does not establish that NO₂ exposure causes impaired lung function.
- Evidence Gaps & Limitations
The study was based on a small sample from a single county, limiting generalizability. The researchers could not adjust for several potentially important confounders, including smoking or vaping, secondhand smoke exposure, home conditions, socioeconomic factors, interactions among pollutants, and meteorological conditions. The study also lacked data on adherence to SCD-modifying or asthma-control therapies. Because of the observational design, the findings establish an association rather than causation. Larger, longitudinal, multicenter studies are needed to clarify exposure-response relationships, mechanisms, and whether reducing air-pollution exposure improves pulmonary outcomes in SCD.
Source: Journal of Sickle Cell Disease- “Pulmonary function among children and young adults with sickle cell disease: the potential role of air pollution”
Regulatory & Guideline Watch
The U.S. Environmental Protection Agency (EPA) identifies nitrogen dioxide (NO₂) as one of the six criteria air pollutants regulated under the Clean Air Act and uses the Air Quality Index (AQI) to communicate short-term outdoor air-quality risks. Children and people with lung disease, including asthma, can be more susceptible to certain air-pollution exposures. No SCD-specific guideline establishes an ambient NO₂ exposure threshold or recommends routine air-pollution monitoring as part of SCD management.