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While plenty of previous research has linked individual pollutants
to increased risks of specific types of cancer, the current study
focused on how the combined effect of exposure to a variety of
environmental contaminants may influence the risk of tumors.
Researchers examined the annual incidence rate for cancer diagnoses
for each county in the U.S. and found an average of 451 cases for
every 100,000 people. Compared to counties with the highest
environmental quality, counties that ranked the lowest had an
average of 39 more cancer cases each year for every 100,000
residents.
“We do not experience exposures in a vacuum but rather are exposed
to several exposures at any one time,” said lead study author Dr.
Jyotsna Jagai, of the University of Illinois at Chicago.
“We considered a broad definition of environmental exposures, which
included pollution in the air, water, and land and also (man-made)
and sociodemographic environmental factors,” Jagai said by email.
“We found that counties with poor overall environmental quality
experienced higher cancer incidence than those counties with good
overall environmental quality.”
Cancer causes one in four deaths in the U.S. each year, Jagai and
colleagues note in the journal Cancer.
To assess the connection between environmental quality and cancer
risk, the researchers examined county-by-county data on exposure to
different pollutants from 2000 to 2005 and on new cancer diagnoses
from 2006 to 2010.
Compared to men in counties with the highest environmental quality,
men living in counties with the poorest environmental quality had an
average of 33 more cases of all types of cancer for every 100,000
people. For women, living in counties with the worst environmental
quality was associated with an average of 30 more cases of cancer
for every 100,000 people.
In addition to looking at overall cancer rates, researchers also
looked separately at the most common tumor types: lung, colorectal,
prostate and breast malignancies.
Prostate and breast tumors were strongly associated with
environmental quality, the study found. Living in the counties with
the worst environmental quality was tied to about 10 more cases of
these tumors for every 100,000 people.
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One limitation of the study is that researchers may not have had
enough years of data to fully assess the connection between
pollutants and cancer because some slow-growing tumors might appear
many years after exposure to pollutants, the authors note.
Researchers also lacked data on individuals’ lifestyle factors that
can influence cancer risk, such as alcohol use, exercise habits and
nutrition.
“We do have to be careful about drawing conclusions from studies of
neighborhood factors that lack detailed information on
characteristics of individuals living in those neighborhoods because
the observed associations could very well be due to attributes of
the individuals rather than the environment itself,” said Scarlett
Lin Gomez, author of an accompanying editorial and a researcher at
the Cancer Prevention Institute of California and the Stanford
Cancer Institute.
“However, neighborhood environment has been consistently shown to
have its own impacts on health and on cancer over and above
individual characteristics,” Gomez said by email.
SOURCE: http://bit.ly/2prAoNT Cancer, online May 8, 2017.
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