Acute lymphoblastic leukemia (ALL) is the most common childhood cancer and shows marked differences in incidence and survival by age. International data indicate substantially higher 5-year survival among pediatric patients compared with older age groups. In northern Thailand, seasonal and persistent air pollution—especially particulate matter (PM) from biomass burning—regularly exceeds World Health Organization recommendations. The health burden of ambient air pollutants such as PM2.5, PM10, NO2, O3, and CO includes increased mortality from noncommunicable diseases, and limited evidence links PM exposure with leukemia outcomes. This study aimed to assess whether exposure to major ambient pollutants is associated with mortality in pediatric, adolescent and young adult (AYA), and adult patients diagnosed with ALL in eight provinces of upper northern Thailand.
This was a retrospective cohort study of 604 patients diagnosed with ALL from January 1, 1999, to December 31, 2020, in eight provinces in upper northern Thailand (Chiang Mai, Chiang Rai, Nan, Phrae, Phayao, Lampang, Lamphun, and Mae Hong Son). Patients were followed from registry registration until the end of February 2024 to assess survival.
Demographic and clinical variables from the Chiang Mai Cancer Registry were included where available: sex, age, body mass index (BMI), smoking history, hill tribe ethnicity, family history of cancer, and cancer characteristics and stage at diagnosis. For pediatric patients, additional maternal and family sociodemographic variables available in the registry were included. Cause of death was obtained from linked hospital records and national death certificate data.
Hourly concentrations of PM2.5, PM10, NO2, O3, and CO were obtained from the Copernicus Atmosphere Monitoring Service (ECMWF) reanalysis product. The reanalysis provides consistent atmospheric composition fields with approximately 80 km horizontal resolution (often interpolated to a 0.75° × 0.75° grid). Annual average concentrations for 2003–2020 were calculated for each district in the eight provinces, then linked to patients’ district of residence at diagnosis.
The source text indicates the investigators assumed patients’ recorded addresses did not ... (text truncated in the provided source). Therefore, details on assumptions about residential stability, duration at address, or handling of potential residential mobility and resulting exposure misclassification were not reported in the excerpt provided.
Statistical analyses described in the article included calculation of survival rates by age group and comparison of pollutant concentrations between survivors and nonsurvivors. Multivariable survival models produced adjusted hazard ratios (aHRs) for death comparing AYA and adult groups to pediatric patients and assessed the association between pollutant categories (including a PM2.5 threshold) and mortality. Specific model covariates and full modeling strategy details were presented in the original article; only summary results are available in the provided text.
The cohort comprised 604 ALL patients: 344 (57.0%) pediatric (<15 years), 152 (25.1%) AYA (15–39 years), and 108 (17.9%) adults (≥40 years). Reported 5-year survival rates were 64.5% for pediatric patients, 19.6% for AYA, and 6.7% for adults.
Comparisons of ambient pollutant concentrations showed that PM2.5, PM10, O3, and CO were significantly higher among patients who died than among survivors, with these differences most marked in the pediatric subgroup. Among AYA patients, those who died had higher PM2.5, PM10, and CO concentrations compared with survivors. The manuscript reports adjusted hazard ratios for age: AYA patients had an increased risk of death relative to pediatric patients (aHR 3.76), and adults had a still higher risk (aHR 8.10). A diagnosis before 2010 was associated with increased mortality (aHR 1.38).
The investigators also report a pollutant threshold association: PM2.5 ≥50 µg/m³ was associated with higher mortality among pediatric patients in this cohort. The text provided does not include full numerical details for pollutant-specific effect estimates, confidence intervals for pollutant associations, or subgroup model covariates beyond those summarized above.
In a region with recurrent and sometimes extreme particulate pollution related to biomass burning and transboundary smoke, this registry-based study identified links between higher ambient pollutant levels and worse survival after ALL diagnosis. The age-stratified results showed the largest pollutant-associated differences in pediatric patients, while AYA decedents also experienced higher PM2.5, PM10, and CO exposures than survivors. Age at diagnosis remained a strong predictor of mortality, consistent with prior literature reporting superior outcomes in children compared with older patients.
The study used a global atmospheric reanalysis product to assign district-level annual averages of PM2.5, PM10, NO2, O3, and CO to patients’ residential districts at diagnosis. This approach enables consistent spatially and temporally resolved exposure estimates across multiple provinces but can be limited by resolution and exposure misclassification if individual residential histories or indoor exposures differ from district averages.
Limitations apparent from the provided excerpt include incomplete reporting in the source text regarding assumptions about residential address stability and the handling of mobility over the follow-up period. Detailed modeling choices, adjustment covariates, and full pollutant-specific effect sizes and confidence intervals for all comparisons were not included in the excerpt and should be consulted in the full article for comprehensive interpretation.
In this cohort of 604 ALL patients in northern Thailand, higher ambient concentrations of PM2.5, PM10, O3, and CO were observed in patients who died versus survivors, with the strongest signals among pediatric patients. AYA and adult age groups had substantially higher adjusted mortality risks compared with children, and diagnosis before 2010 was associated with increased mortality. The study reports an association between PM2.5 ≥50 µg/m³ and increased mortality in pediatric ALL patients. These findings highlight the potential adverse influence of ambient air pollution on survival after ALL diagnosis in a high-exposure region. Further evaluation of individual-level exposure, residential mobility, and detailed pollutant-specific risk estimates as reported in the full paper is recommended to clarify causality and inform protective strategies.
Note: The provided source text was truncated at a sentence describing assumptions about patients’ recorded addresses; therefore, specific details about exposure assignment assumptions or handling of residential change were not available in the excerpt and are not reported here.