Long-term exposure to traffic-related air pollution may increase the risk of developing meningioma, a common noncancerous brain tumor, according to a large Danish study.
Air pollution, especially from
traffic, may raise the risk of noncancerous brain tumors. Ultrafine particles
appear particularly linked to meningioma.
Individuals who are exposed to
elevated levels of air pollution could face a greater likelihood of developing
meningioma, a usually benign brain tumor, according to a large-scale study
published in Neurology Clinical Practice, a journal of the American
Academy of Neurology.
Meningiomas commonly arise in the protective layers
surrounding the brain and spinal cord. While the study identifies a connection
between air pollution and meningioma, it does not establish a causal
relationship.
Traffic-related pollutants under scrutiny
The research examined a range of air pollutants,
particularly those associated with traffic, such as nitrogen dioxide and
ultrafine particles, which tend to be most concentrated in urban areas.
“Many forms of air pollution have been linked to
negative health outcomes, and ultrafine particles are small enough to penetrate
the blood-brain barrier, potentially affecting brain tissue directly,”
explained study author Ulla Hvidtfeldt, PhD, of the Danish Cancer Institute in
Copenhagen. “Our findings indicate that prolonged exposure to traffic-related
and other sources of air pollution may contribute to the development of
meningioma, reinforcing existing evidence that air pollution can impact the
brain as well as the heart and lungs.”
The study tracked nearly 4 million Danish adults,
averaging 35 years of age, over a 21-year span. During this period, 16,596
individuals were diagnosed with central nervous system tumors, including 4,645
cases of meningioma.
Researchers used address histories and advanced
modeling to estimate long-term exposure to air pollution.
Comparing exposure to tumor risk
The researchers estimated each participant’s average
exposure over a 10-year period to several pollutants: ultrafine particles (less
than 0.1 micrometers in diameter), fine particulate matter known as PM2.5 (2.5
micrometers or smaller), nitrogen dioxide (a gas primarily produced by
traffic), and elemental carbon (an indicator of diesel emissions).
They then
categorized participants into three groups for each pollutant, ranging from the
lowest to the highest levels of exposure, to compare health outcomes across
these exposure levels.
Elevated pollutant levels linked to higher risk
For example, for ultrafine particles, people in the
lowest group had an average 10-year exposure of 11,041 particles per centimeter
cubed (cm3) compared to people with the highest exposure of 21,715
particles/cm3. In these groups, 0.06% of people in the group with the lowest
exposure developed meningiomas compared to 0.20% of people with the highest
exposure.
After adjusting for factors like age, sex, education level, and neighborhood socioeconomic status, researchers found that people with higher exposure to air pollutants had a greater risk of developing meningioma:
A 10% increase in risk for meningioma was observed for every additional 5,747 ultrafine particles per cubic centimeter (cm³).
For fine particulate matter, risk rose by 21% for each 4.0 microgram per cubic meter (µg/m³) increase.
Nitrogen dioxide exposure was linked to a 12% higher risk for every 8.3 µg/m³ increase.
Elemental carbon exposure was associated with a 3% greater risk for each 0.4 µg/m³ increase.
The study did not find strong links between these
pollutants and more aggressive brain tumors, such as gliomas.
“While research on the health effects of ultrafine
particles is still in its early stages, these findings point to a possible link
between traffic-related ultrafine particle exposure and the development of
meningioma,” Hvidtfeldt said. “More research is needed to confirm these
results, but if cleaning up our air can help lower the risk of brain tumors,
that could make a real difference for public health.”
A limitation of the study is that pollution exposure
was based on outdoor air quality near people’s homes, so it doesn’t capture all
sources of personal exposure—like workplace air or time spent indoors.
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