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Johnson & Johnson recalling sunscreen: why is benzene carcinogen?

Benzene is both naturally occurring and man-made. It is a known to cause cancers of blood cells and leukemia based on studies in both people and animals.

Johnson & Johnson recalling sunscreen: why is benzene carcinogen?
SCOTT OLSON AFP

Johnson & Johnson voluntarily recalled five lines of sunscreens after they were found to have higher-than-normal levels of benzene, a carcinogen which has been linked to cancer with repeated exposure. What is benzene and why is it a carcinogen?

Benzene is a colorless or light-yellow chemical, that has a sweet odor and is highly flammable. It forms both naturally and through human activities evaporating rapidly when exposed to air. It has also been found to be a carcinogen, causing cancer and other disorders with long-term exposure.

How benzene is formed

Benzene can form through natural processes such as volcanoes and forest fires. Most exposure though comes from human activities; benzene is a natural part of cigarette smoke, a major source, as well as crude oil and gasoline. According to the Center for Disease Control and Prevention low levels of benzene can be encountered in the outdoors, especially near gas stations, from car exhaust, and industrial emissions. Levels tend to be higher indoors due to its presence in products such as glues, paints, furniture wax, and detergents.

It is one of the 20 most widely used chemicals in the US, used to make other chemicals and products. These include plastics, resins and synthetic fibers as well as some lubricants, rubbers, dyes, detergents, drugs, and pesticides. It is also used as an industrial solvent (a substance that can dissolve or extract other substances). The use of benzene has been greatly reduced over the decades as more regulations have been placed on its use.

Why is benzene carcinogen?

Most studies focus on the inhalation, from occupational exposure, or ingestion of benzene. Research into skin exposure shows that benzene can irritate the skin causing redness and blisters, but has also been found to cause benign tumors in mice genetically modified to be more susceptible to carcinogens according to the National Toxicology Program Report on Carcinogens.

Studies in both humans, exposed to high levels of benzene in industrial settings, and lab animals have shown a link between benzene and leukemia along with other cancers of the blood. Benzene has been found to affect bone marrow cells, where new red blood cells are formed, reducing the production of red blood cells. It can also cause the loss of white blood cells through damage to the immune system when the levels of blood and antibodies change.

Studies on lab animals have found benzene to cause different types of tumors when inhaled or swallowed. The findings from those studies also support an excess risk of leukemia in humans from long-term exposure in occupational settings. However, the majority of studies have not found a conclusive increased risk of cancers other than leukemia among people with higher exposures. Even so, the Environmental Protection Agency has classified benzene as a “known human carcinogen for all routes of exposure.”