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Home distance from benzene sites linked to lymphoma risk
Monday, July 29, 2013
By Andrew M. Seaman
NEW YORK (Reuters Health) - How far a person lives from a manufacturing plant that releases the chemical benzene into the environment may determine their risk of developing immune system cancer, a new study suggests.
Researchers in Georgia looking at rates of non-Hodgkin lymphoma in that state found that risk for the disease fell with every mile between a person's home and facilities that release benzene.
"It would suggest even with moderate changes in distance that there can be large changes in the decrease in non-Hodgkin lymphoma," said Dr. Christopher Flowers, the study's lead author and head of the lymphoma program at Winship Cancer Institute of Emory University in Atlanta.
Non-Hodgkin lymphoma is a large group of cancers that grow out of the body's immune system. An individual's risk of developing the cancer is about 1 in 50 over the course of a lifetime, according to the American Cancer Society.
But that risk has risen between 3 and 4 percent every year since the 1970s, Flowers and his colleagues write in the journal Cancer.
Better diagnosis of the disease and changes in cancer classifications are responsible for about half of that increase, they add, and exposure to certain industrial chemicals may also be contributing.
According to the U.S. Centers for Disease Control and Prevention, benzene is used in the production of plastics, nylons, resins and other materials, such as lubricants, dyes, cleaners and pesticides.
Even in small amounts, the chemical has been shown to alter DNA, the researchers write, and it is already linked to the development of leukemia, a blood cell cancer.
But there's still controversy about whether it is involved in non-Hodgkin lymphoma.
For the new study, Flowers and his colleagues combined information on chemical release sites in Georgia between 1988 and 1998 from the U.S. Environmental Protection Agency, and data from a state cancer registry from 1999 to 2008 as well as the 2000 U.S. Census.
In Georgia, 19 facilities reported benzene releases between 1988 and 1998 and there were 12,716 cases of non-Hodgkin lymphoma in adults between 1999 and 2008.
The overall risk for the cancer was about 17 cases per 100,000 people per year, and the researchers found that the risk of developing non-Hodgkin lymphoma fell by about 0.3 percent for every mile between a person's home and a benzene release site.
"These are mean differences between the location areas and release sites. That takes into account every release site in the state," Flowers said.
He added that it's hard to define how many cancers a 0.3 percent reduced risk would represent, but it's a difference that won't mean much to an individual person.
"We can say - at the population level - the incidence of non-Hodgkin lymphoma was higher in those population areas that are clustered around (the facilities)," Flowers said.
He cautioned, however, that the new finding can't exclude influences from other factors, such as other chemicals that were also released at those sites.
"Given the fact that there are numerous other studies in other countries It's a further piece of important evidence supporting a link between benzene exposure and non-Hodgkin lymphoma," said Martyn Smith, a professor of public health at the University of California, Berkley.
"I think this is an additional piece of information that's very useful in adding to the literature," said Smith, who wasn't involved in the new study.
Tongzhang Zheng, the Susan Dwight Bliss Professor of Epidemiology and Environmental Health at the Yale School of Public Health in New Haven, Connecticut, said the link may be even stronger for specific types of non-Hodgkin lymphoma or for people who are genetically susceptible to certain cancers.
"This study clearly suggests there is an increased risk, but because of the type of the study we cannot say there is a casual relationship," said Zheng, who has studied the effects of benzene exposures but wasn't involved in the new research.
SOURCE: http://bit.ly/16uRev9 Cancer, online July 29, 2013.
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