A new study by researchers at Emory University has found that people living near factories that emit a chemical known as benzene are at greater risk for developing non-Hodgkin lymphoma, or NHL, a blood cancer. The study, conducted in and around Atlanta and Savannah, Georgia, concluded that for each additional mile a person lived from benzene-emitting petroleum refineries and manufacturing plants, their NHL risk dropped by 0.31%.
Pediatrics, Hematology and Medical Oncology professor Christopher Flowers, one of the lead researchers behind the study, said that the difference in risk for NHL between those living closest to and farthest from factories is substantial. Non-Hodgkin lymphoma is a term that describes several different conditions, some of which are much more aggressive than others.
Benzene and Non-Hodgkin Lymphoma
Rates of NHL are on the rise in America. Over 70,000 people are expected to be diagnosed with this type of cancer this year, and roughly 19,000 will die as a result of the disease. Approximately 30% of those diagnosed with NHL die within the first five years after diagnosis. Lymphoma rates have escalated by an average of 4% per year for the last 40 years running, according to the researchers.
While lymphoma diagnoses have become more common in part due to improved diagnosis methods and an increase in HIV rates (people with HIV are more likely to develop various types of cancers, including NHL), researchers say that about half of the increase could be due to environmental exposure to chemicals such as benzene.
The Environmental Protection Agency, or EPA, classifies benzene as a carcinogenic chemical. The substance itself is a fast-evaporating liquid found in petroleum and coal derivatives, and exposure generally occurs through breathing. Benzene is used commercially in the manufacture of pesticides, detergents and plastics.
It’s long been known that benzene causes leukemia, though only recent studies such as the one cited here are finding a link between benzene and lymphoma, which affects white blood cells. Dr. Richard Hayes, epidemiology professor at New York University, says that although the link is not universally accepted, supporting evidence is accumulating. In a previous study, Hayes and other researchers examined over 75,000 Chinese factory workers, finding them to be at four times greater risk for death from lymphoma than other workers.
Study Findings and Limitations
In order to conduct their new study, Emory University researchers compared population statistics for various areas of Georgia to EPA data regarding factories that emitted benzene from 1988 until 1998. They then compared this data to data regarding the prevalence of non-Hodgkin lymphoma from 1999 through 2008. As expected, after adjusting for factors such as race and age they found that NHL rates were higher in areas around benzene-emitting factories, particularly in the metropolitan Atlanta area. Rates were also higher in Savannah and Augusta as compared to the less-populated southern regions of the state.
One limitation of the study was the fact that urban areas also tend to be more polluted from cigarette smoke, car exhaust and other emissions. It’s possible that these factors, not just factory benzene emissions, contributed to the heightened rates of lymphoma.
In addition, the researchers had no way of detecting the amount of benzene to which individuals in the study were exposed. In other words, the fact that two people live an equal distance from a benzene-emitting factory doesn’t necessitate that they’re exposed to the same levels of benzene.
The Bottom Line
People who live near factories that emit the chemical benzene are more likely to develop the blood cancer non-Hodgkin lymphoma, according to a new study conducted at Emory University in Georgia.
The full text of the study can be found online in the journal Cancer.