http://www.reuters.com/article/2015/10/06/us-health-airpollution-kids-leukemia-idUSKCN0S02Q520151006
Tue Oct 6, 2015 4:38pm EDT
Benzene in traffic emissions tied to childhood leukemia
By Kathryn Doyle
(Reuters Health) - Traffic pollution near the home – and specifically,
benzene in the air - increases the risk of one type of childhood
leukemia, according to a nationwide study in France.
Leukemia, or cancer of the blood cells, is the most common cancer among
children younger than age 15, according to the U.S. National Cancer
Institute.
Childhood leukemia is a very rare disease, so it is hard to have enough
cases in one study to determine which risk factors play a role, but
according to this and other large surveys, the evidence seems to be
pointing toward an association between traffic emissions and childhood
leukemia, said coauthor Denis Hemon of the Institute National de la
Santé et de la Recherché Medical (INSERM) based in Paris.
“Overall I would say the balance is in favor of an association,” Hemon
told Reuters Health by phone.
The researchers used a nationwide study of 2,760 childhood leukemia
cases in France compared with 30,000 kids who did not have leukemia
between 2002 and 2007.
They used residential addresses to estimate proximity to traffic,
including distance to nearest major road and total length of roads near
the home, as well as estimates of benzene concentrations specifically
for the Paris metro area.
Children who lived more than 500 meters from the nearest road were used
for reference, having the lowest traffic exposure, and those who lived
150 meters or less from a major road had the highest exposure.
More than 2,000 of the leukemia cases were acute lymphoblastic leukemia
(ALL), while only 418 were acute myeloblastic leukemia (AML).
A 300 meter increase in major road length within 150 meters of the home
appeared to increase the risk of AML by 20 percent, but did not affect
the risk of ALL, when the researchers compared the leukemia groups and
the comparison group.
There were similar results specifically in the Paris metro area when
benzene levels were included in the analysis, as reported in the
American Journal of Epidemiology.
Benzene concentrations near Paris ranged from 0.3 to 8.5 micrograms per
cubic meter.
According to the Air Quality in Europe Report 2014 by the European
Environmental Agency, the limit to environmental levels of benzene
should be 5 micrograms per cubic meter, although the World Health
Organization has not set an air quality guideline for benzene.
Short-term benzene exposure may cause drowsiness, dizziness, and
headaches, as well as eye, skin, and respiratory tract irritation, while
long-term inhalation exposure in occupational settings has caused
various disorders in the blood, including reduced numbers of red blood
cells and aplastic anemia, according to the U.S. Environmental
Protection Agency.
Though benzene is carcinogenic for adults, it is not clear how benzene
exposure would cause AML in children, Hemon said.
High radiation exposure can cause leukemia, as can genetic risk factors
like Down Syndrome, and there may be other risk factors we do not know
about, he said.
Evidence is starting to mount that exposure to traffic emissions early
in life is tied to childhood leukemia, either only to AML or just more
strongly to this than to other forms of leukemia, said professor Marco
Vinceti of the Universita di Modena e Reggio Emilia in Italy, who has
studied this question but was not part of the French paper.
“Our study as well found the same association with leukemia,” Vinceti
told Reuters Health by phone. “We looked at particulate matter and
benzene, and the results were that there was no association for
particulate matter.”
The French study was large and carefully avoided selection bias by
including data from all patients diagnosed in the country, he said.
There seems to be a stronger link between benzene and leukemia in Europe
than in the U.S., though it is unclear why, he said.
Though benzene levels have sharply decreased in Europe in recent years,
and the levels in the current study are largely well below European
regulations, childhood leukemia cases have not decreased, Vinceti said.
This may be due to other risk factors, like genetics, he said.
There is not much an individual can do to reduce exposure to traffic
emissions in a big city, other than supporting legislation to further
reduce automobile emissions, Hemon said.
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