Most childhood cancers are "probably" down to prenatal exposure to industrial and environmental pollutants, most likely to have been inhaled by the mother during pregnancy, suggests research in the Journal of Epidemiology and Community Health.
The author points out that several of the implicated compounds may act as a proxy for other activities, such as transport, which itself generates many other harmful substances.
But carbon monoxide, particulate matter (PM10), and nitrogen oxides, which are associated with oil burning, particularly in engines; and non-methane volatile organic compounds, including benzene, 1,3-butadiene, benz(a)pyrene, and dioxins are cited in the research.
Animal research has already identified some of these compounds as carcinogens, says the author.
Non-methane volatile organic compounds variously reflect solvent use, engine exhaust, fuel evaporation, and other industrial/refinery processes.
The author based his findings on a chemical emissions map for the UK, produced by the UK National Atmospheric Emissions Inventory (NAEI) for 2001, and details of all children who had died from leukaemia and other cancers before their 16th birthday in Great Britain between 1953 and 1980.
To compensate for the time lag between the production of the map and the era covered by the death register, only those children dying between 1966 and 1980 were included in the study.
When all the data had been compiled and the risks calculated, children born within a 1 km radius of emissions hotspots of particular chemicals were between two and four times as likely to die of cancer before reaching the age of 16, as other children.
Proximity to emissions of 1,3-butadiene and carbon monoxide carried the highest risks.
"Most childhood cancers are probably initiated by close perinatal encounters with one or more of these high emissions sources," concludes the author.
The low atmospheric levels of these substances suggest that the mother may breathe them in, with carcinogens passing across the placenta, he ventures. But he adds "effective direct exposures in early infancy, or through breast milk, or even pre-conceptually, cannot be excluded."
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