Poster: Traffic-related air pollution and risk of childhood leukemia: a meta-analysis
- Dettagli
- Pubblicato Lunedì, 20 Ottobre 2014 12:00
Background and Aims:
Childhood leukemia is overall a rare occurrence, however it is the most frequent malignancy affecting children under 15 years of age. The majority of these cases are acute lymphoblastic leukemia (ALL), followed by acute myeloid leukemia (AML); chronic forms of childhood leukemia are relatively rare. To date, the etiology of childhood leukemia remains largely unknown. Few risk factors (genetic disorders, early infections, ionizing radiation, etc.) have been established, but these factors explain only a small proportion of childhood leukemia. Environmental risk factors among different examined include radon, pesticides, electromagnetic fields and outdoor air pollution, but they have been found to be weakly and inconsistently associated with either form of acute childhood leukemia. Here we review epidemiological studies including outdoor air pollution exposure and risk of childhood acute leukemia
Methods:
We carried out a PubMed up to June 2014, using as MeSH terms childhood leukemia, acute lymphoblastic leukemia, risk, air pollution, outdoor air pollution, and traffic. We identified nineteen case ‐control studies eligible for potential inclusion in the review. We assessed the risk of bias of these studies using the Newcastle Ottawa scale, and we reviewed the methodologies used to assess exposure to traffic ‐related air pollutants, such as the number of vehicles per day characterizing the roads close to subjects' residence, proximity to main roads, or the individual measured or modeled exposure to selected air contaminants.
Results:
Depending on exposure assessment methodology, the meta‐analysis yielded different overall odds ratios (OR), generally indicating an increased risk of childhood leukemia or specific subtypes of the disease, and these results were strengthened after removing studies at risk of selection bias. Summary ORs of the pooled analysis were 1.14 (95% CI 0.97 – 1.34) for traffic density indicators, 1.14 (0.94 – 1.39) for nitrogen dioxide exposure, 1.83 (1.42 – 2.36) for petrol station exposure and 1.46 (0.72 – 2.95) for benzene modeled exposure. Analysis of a specific subtype alone (ALL) get an OR of 1.22 (0.95 – 1.60) for traffic density indicators, furthermore if we consider only studies with NOS≥7 overall OR were 1.20 (0.98 – 1.47) for traffic density indicators and 1.21 (0.97 – 1.52) for nitrogen dioxide exposure. A possible source of difference in effects could be the country where studies were conducted: stratified analysis between American studies and European ones give OR 1.08 (0.88 – 1.33) and 1.56 (1.08 – 2.25) respectively.
Conclusions:
Despite the limitations of this meta‐analysis, such as the differences in the assessment of exposure to outdoor air pollutants, the risk of confounding and the statistical imprecision of the point estimates, results of the study appear to suggest a direct association between traffic‐related air pollution and risk of childhood leukemia.
