World Trade Center first responders have a significantly higher rate of leukemia and other cancers, including those of the thyroid and prostate, nearly two decades after the attacks on September 11, 2001, new research suggests.

The findings add to a growing body of evidence that has found higher rates of cancer in those who arrived and worked at Ground Zero in the months following the attack. However, this is the first time that researchers have linked presence at the scene with “statistically significant elevations” of leukemia cases. The findings are reported in JNCI Cancer Spectrum. 

An estimated 50,000 rescue and recovery personnel arrived at the scene, during which time many were exposed directly to dust containing dangerous chemicals – such as asbestos, benzene, polychlorinated biphenyls – from the collapsing towers. Cleanup at the site continued for 10 months, further exposing workers to toxins later shown to have adverse health effects, including cancer.

To come to their conclusions, researchers at Mount Sinai analyzed the cases of more than 28,000 workers registered with the General Responder Cohort, a federally funded medical monitoring and treatment program, and compared it with cancer registries from across six states between 2002 and 2013. Of the first responders, 85 percent were males who worked namely in construction or law enforcement – half of the responders reported at least some level of exposure to dust clouds caused by the collapse.

Specifically, researchers found the presence of 1,072 cancers in 999 responders. Though cancer rates may have been linked to other risk factors such as age, gender, and smoking habits, the researchers say that the "complex, sustained exposure and the unknown long-term health effects... are matters of national concern." Neither the length of time working on the site nor the intensity of exposure seemed to impact the higher risk of developing certain cancers, but the researchers note that wearing protective equipment or respirators may have played a role in reducing exposure to carcinogens.

"This study showed increased incidence of several cancer types compared to previously conducted studies with shorter follow-up periods," said Dr Susan Teitelbaum, professor of environmental medicine and public health at the Icahn School of Medicine at Mount Sinai and one of the lead authors, in a statement. "Because of the long latency period of many types of cancer, it is possible that increased rates of other cancers, as well as World Trade Center exposure health issues, may emerge after longer periods of study."

The findings are of particular relevance as cancer is classified as a WTC-related condition by the National Institute for Occupational Safety and Health, meaning those who have been diagnosed with the condition are eligible for federally funded treatment.