Childhood cancers are devastating. Even when the disease is not fatal, its long-term effects can be severe. Not enough is known about the risk factors.
“Research suggests that only 5 to 10 per cent of childhood cancers are attributable solely to genetics, while the rest are due to other factors, particularly environmental ones,” explained Stéphane Buteau, a professor in the Department of Environmental and Occupational Health in the School of Public Health at Université de Montréal.
Through a project funded by the Canadian Institutes of Health Research, Buteau is leading a multi-institutional team examining the link between air pollution and childhood cancers.
In study published in Environmental Pollution, the researchers examine one specific source of air pollution—gas stations—and their connection to cancer risk in children.They have found that living within 250 metres of a gas station raises childhood cancer risk. Specifically, living within 250 metres of a gas station is associated with a higher risk of childhood leukemia—a risk that increases with proximity and is highest for those living within 100 metres, but stricter vapour-control regulations can reduce the danger.
A known carcinogen
The research team focused on gas stations because gasoline contains benzene, a known carcinogen linked to leukemia and other serious health risks in adults.
Benzene is a natural component of crude oil that is also found in gasoline. Highly volatile, it is released into the environment during gasoline storage, vehicle refueling and the unloading of tanker trucks.
A 2023 Health Canada study concluded that exposure to benzene from gas station emissions may pose unacceptable risks to human health for people living nearby.
However, the effects of this exposure on the unborn and on children – particularly the cancer risk – remain poorly understood.
The researchers used Quebec’s medical administrative databases, which consist of provincial health records from doctor visits and hospital stays, to track newborns from birth. This enabled them to link a child’s place of residence at birth with cancer diagnoses.
To assess exposure to benzene, the researchers used three indicators: number of gas stations within a 250 metre radius of the child’s postal code at birth, distance to the nearest gas station, and a composite measure of both distance and number of gas stations.
Higher risk within 250 m
The results were clear: living near a gas station increased the risk of developing childhood leukemia, even after adjusting for confounding factors such as socioeconomic status, living environment (urban versus rural) and maternal characteristics.
“We also controlled for the fact that people living near gas stations are often close to busy roads,” added Buteau.
Specifically, living within 250 metres of a gas station is associated with a higher risk of childhood leukemia – a risk that increases with proximity and is highest for those living within 100 metres.
The study is not without its limitations, notably the use of indirect measures, or proxies, as stand-ins for variables that are difficult or impossible to measure directly.
“In the absence of residential history, postal codes at birth were used to estimate exposure during the prenatal and early-life periods—times of heightened susceptibility to environmental hazards,” said Buteau, who hopes to replicate the study across Canada to confirm the results.
Reducing the danger
The study also found that the link between living near a gas station and childhood cancer was less pronounced in Montreal, where municipal regulations require gasoline vapour recovery systems in order to minimize the emission of volatile organic compounds during fuelling.
“While we don’t know exactly how well these regulations are being followed, it’s a compelling finding that supports the hypothesis that such measures do in fact reduce atmospheric emissions,” noted Buteau.
As a precautionary measure, the study recommends adopting similar regulations across Canada and establishing buffer zones to ensure new homes, schools and daycares are not built within range of gas stations.
“Such measures are simple and not costly to implement, and they would deliver major health benefits and help reduce inequalities in exposure levels,” Buteau pointed out.
Thus, despite its fairly simple and straightforward design, this study has significant public health implications, he believs. Moving forward, the researchers are expanding their scope to examine the role of industrial emissions and particulate matter in the development of childhood cancers.
