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Janet Gray, Ph.D.
Janet Gray, Ph.D.

As author of our 2008 and 2010 State of the Evidence reports, Dr. Gray drives the science behind all our work.

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Accidental Exposure Studies


Definition: Studies of individuals and communities who experience environmental catastrophes that result in high exposures to chemicals and radiation.

Classification: Human

Catastrophes offer some of the best evidence for the link between environmental exposures and cancer because the exposure is related to an observable event that happened at a specific time. Exposures are often carefully measured and documented and can be linked to health records.


Some communities experience high-level catastrophic exposures to carcinogens: Hiroshima and Nagasaki after the U.S.-detonated atomic bombs; Chernobyl and Three Mile Island after nuclear reactor accidents; Seveso, Italy, after the accidental release of dioxin from a chemical plant. In each of these cases, the mass exposures of young women and girls led to increased breast cancer rates two to three decades later (Pesatori, 2009; Pukkala, 2006; Land, 1997).


Exposures are often easily identified due to the catastrophic nature of the event. Measures of toxic chemicals or radiation may be better documented in the case of extreme events, and the time at which exposures occurred is more clearly defined. Studies can look at the age of individuals when the event occurred, so these studies have offered very important insights into the link between timing of exposure and health effects such as breast cancer.


Catastrophic exposures impose considerable human suffering that could often be avoided via more prudent regulations of chemicals and radiation. They are, by nature, accidental, and require rapid response and data collection. Exposures are frequently higher than those in normal daily life, so these cases may not answer questions about low-dose exposures.