A French study has revealed an increased incidence of acute myeloid leukemia (AML) among children living close to heavily used roads.
The incidence of AML was 30% higher among children who lived within 150 m of heavily used roads and where the combined length of road sections
within this radius exceeded 260 m.
The researchers believe the association between AML and road proximity may be driven by traffic-related benzene exposure.
Previous research has shown an increased risk of leukemia among adults with a history of occupational exposure to benzene.
The current study did not suggest an increased risk of acute lymphoblastic leukemia (ALL) among children living closed to heavily used roads.
Jacqueline Clavel, MD, PhD, of INSERM in Paris, France, and her colleagues reported these findings in the American Journal of Epidemiology.
The team analyzed 2760 cases of leukemia diagnosed in children younger than 15 years of age in metropolitan France between 2002 and 2007, including 418 cases of AML and 2275 cases of ALL.
The researchers compared these cases to a contemporary sample of 30,000 control children representative of the metropolitan population.
The data showed that neither distance from the nearest major road(s) nor the length of major roads within 150 m of a child’s residence was associated with ALL.
However, there was an association for AML. For children whose home was less than 150 m from the nearest major road(s), the odds ratio (OR) was 1.2.
When the total length of major road(s) within 150 m from the child’s residence was 257-308 m (second tertile) or 309 m or greater (third tertile), the OR was 1.3. When the total length of major roads was 1-256 m (first tertile), the OR was 0.90.
The researchers noted that traffic-related nitrogen dioxide concentration was not associated with ALL or AML. But their data indicated that benzene concentration was associated with AML.
To assess this potential association, the team studied the Île-de-France region of Paris, the most urbanized region, for which the mean annual concentration of benzene, mainly from road traffic, was estimated in the vicinity of each residence.
The median estimated benzene concentration for controls living in the Île-de-France region was 1.3 μg/m3 (range, 0.3 to 8.5 μg/m3). And the length of major roads within 150 m of a child’s residence was positively and significantly correlated with log benzene concentration (r=0.3, P<0.001).
So it followed that exposure to an estimated benzene concentration greater than the median was associated with AML (OR=1.6).
The researchers also used a composite variable based on the estimated benzene concentration and the length of major roads around a child’s residence.
The association with AML was largest among children with at least 309 m of major roads within 150 m of their residence and estimated benzene concentrations of 1.3 μg/m3 or greater (OR=2.2).
The researchers said these results support a role for traffic-related benzene exposure in the etiology of childhood AML.
