By Roberta Attanasio
It’s said to have a sweet smell, or a gasoline-like odor. It’s mostly in the air, and sometime in the water and soil. It’s found all around the world. It’s in cigarette smoke and gasoline vapors. It’s a known human carcinogen – a substance known to cause cancer. It’s benzene. Its target organ is the bone marrow, the soft spongy tissue that lies within the hollow interior of long bones and produces all types of blood cells.
The Agency for Toxic Substances and Disease Registry (U.S. Department of Health and Human Services) in the “Toxicological Profile for Benzene” states: “Everyone is exposed to a small amount of benzene every day. You are exposed to benzene in the outdoor environment, in the workplace, and in the home. Exposure of the general population to benzene mainly occurs through breathing air that contains benzene. The major sources of benzene exposure are tobacco smoke, automobile service stations, exhaust from motor vehicles, and industrial emissions. Vapors (or gases) from products that contain benzene, such as glues, paints, furniture wax, and detergents, can also be a source of exposure. Auto exhaust and industrial emissions account for about 20% of the total national exposure to benzene. About half of the exposure to benzene in the United States results from smoking tobacco or from exposure to tobacco smoke.”
In addition, in the same Profile, the Agency for Toxic Substances and Disease Registry tells us: “If you are exposed to benzene, many factors will determine whether you will be harmed. These factors include the dose (how much), the duration (how long), and how you come in contact with it. You must also consider any other chemicals you are exposed to and your age, sex, diet, family traits, lifestyle, and state of health.”
For more than a century, it has been known that excessive exposure to benzene damages the bone marrow, resulting in aplastic anemia, a blood disorder in which the body’s bone marrow doesn’t make enough new blood cells (aplastic anemia is also called bone marrow failure). During the last few decades, it has become clear that long-term exposure to benzene can also cause leukemias and lymphomas.
Leukemias are a group of cancers of the blood-forming cells. Large numbers of abnormal blood-forming cells are produced in the bone marrow. From there, the abnormal cells go into the bloodstream and spread to other parts of the body.
Lymphomas are cancers in which lymphocytes (cells that destroy infectious microorganisms) become abnormal – similarly to leukemias, they grow and multiply uncontrollably.
There are many types of leukemias and lymphomas.
“The U.S. EPA classified benzene as a known human carcinogen: Epidemiologic studies and case studies provide clear evidence of a causal association between exposure to benzene and acute nonlymphocytic leukemia (ANLL) and also suggest evidence for chronic nonlymphocytic leukemia (CNLL) and chronic lymphocytic leukemia (CLL). Other neoplastic conditions that are associated with an increased risk in humans are hematologic neoplasms, blood disorders such as preleukemia and aplastic anemia, Hodgkin’s lymphoma, and myelodysplastic syndrome (MDS). These human data are supported by animal studies. The experimental animal data add to the argument that exposure to benzene increases the risk of cancer in multiple species at multiple organ sites (hematopoietic, oral and nasal, liver, forestomach, preputial gland, lung, ovary, and mammary gland). It is likely that these responses are due to interactions of the metabolites of benzene with DNA. In 1998, the World Health Organization International Agency for Research on Cancer (IARC) classified benzene as a known (Group 1) human carcinogen based on sufficient evidence that benzene is carcinogenic to humans, and limited evidence that benzene is carcinogenic in experimental animals.”
A few days ago (July 29, 2013), a new study on benzene and its association to lymphomas was published on line in Cancer, a peer-reviewed journal of the American Cancer Society. Results from the study show that the incidence of non-Hodgkin lymphoma is significantly higher in regions near facilities that release benzene into the environment. Non-Hodgkin lymphomas include a large variety of lymphomas, as for example chronic lymphocytic leukemia, which is listed in the Benzene TEACH Chemical Summary.
For the study published in Cancer, the researchers used publicly available data from the EPA and the U.S. Census Bureau to analyze the geographic patterns of non-Hodgkin lymphoma cases in the state of Georgia (USA) between 1999 and 2008. This group examined the associations between new cases of lymphoma and the locations of facilities—such as petroleum refineries and manufacturing plants—that released benzene into the surrounding air or water.
The group found that, in areas located around benzene-release sites, the incidence of non-Hodgkin lymphoma was significantly greater than expected. These sites were mostly located in the metropolitan Atlanta area. The risk of non-Hodgkin lymphoma decreased as the distance from benzene-release sites increased (for every additional mile of distance, there was a 0.31 percent decrease in the risk of non-Hodgkin lymphoma).
The investigators hope that their results will inform the public about the potential risks of living near facilities that release carcinogens into the air, groundwater, or soil.
In the mean time, let’s not forget that tobacco smoke is a major source of indoor exposure to benzene.