No statistically significant increased rates were found for all cancer sites combined, the authors added. On the three types of cancer rates that did go up, they stress that their findings should be viewed with caution for a number of reasons. For example, they were based on very few cancers, a short follow-up time, and few multiple comparisons.
The researchers wrote as background information:
"The terrorist attacks on the World Trade Center (WTC) on September 11, 2001, claimed more than 2,700 lives and exposed hundreds of thousands of people to dust, debris, pulverized building materials, and potentially toxic emissions, resulting in short- and medium-term health effects."
The dust, aerosols and smoke that emanated from the debris of the Twin Towers contained complex mixtures of volatile chemicals and particulate matter - many of these chemical are currently classed as suspected carcinogens. A carcinogen is a cancer-causing substance or agent.
Rescue/recovery workers inhaled complex mixtures of volatile chemicals and particulate matter
They authors wrote: "The presence of carcinogenic agents raises the possibility that exposure to the WTC environment could eventually lead to cancers."
Some previous studies had shown higher cancer rates among subgroups of rescuers. In September 2011, Dr. David J. Prezant, Chief Medical Officer of Fire Department of the City of New York, wrote in The Lancet that male firefighters who were involved in rescue and recovery after 9/11 had a higher rate of cancer compared to the rest of the population. Another article in the same journal found that exposed rescue workers and civilians have lower death rates than the rest of the NY City population.
Jiehui Li, M.B.B.S., M.Sc., and team carried out a study to determine what the rate of cancer is among WTC (World Trade Center) rescue and recovery workers, as well as volunteers. They also included data on people who did not take part in any rescue or recovery work. The study included 55,778 residents who had been enrolled in the World Trade Center Health Registry in 2003-2004. 21,850 of them were rescue and recovery workers. They were all, including 33,928 people not involved in any rescue/recovery work, followed-up from enrollment to the end of 2008. They made comparisons within groups of people using a range of models, and also tried to determine whether there might be a link between the intensity of WTC exposure and certain cancers.
They gathered and examined data from 11 state cancer registries in order to identify and link cancer cases. They computed SIRs (standardized incidence ratios) with 2003-2008 New York State rates as the reference, and concentrated on cancers that were diagnosed in 2007-2008 as being the most likely to be associated with exposure during 9/11 and its aftermath.
They also calculated the site-specific and incidence rate differences between the WTC rescue-recovery workers and the New York State population in 2007-2008.
By the end of 2008:
- Among the 55,778 eligible enrollees, there were 1,187 incident cancers
- 37% (439) of these incident cancers were diagnosed in rescue and recovery workers, and 63% (748) among non rescue/recovery participants
- Across all cancers, the midpoint (median) age for a cancer diagnosis of any kind was 57 years
- For all sites combined there was no significant difference in overall cancer (of any kind) between the period up to the end of 2006 and 2007-2008 (the later period)
- Three of the 23 cancer sites investigated saw higher rates during the later period. These were in prostate cancer, thyroid cancer and multiple myeloma
- Thyroid cancer was also significantly higher during the earlier period
"No increased incidence was observed in 2007-2008 among those not involved in rescue/recovery. Using within-cohort comparisons, the intensity of World Trade Center exposure was not significantly associated with cancer of the lung, prostate, thyroid, non-Hodgkin lymphoma, or hematological cancer in either group.
Given the relatively short follow-up time and lack of data on medical screening and other risk factors, the increase in prostate and thyroid cancers and multiple myeloma should be interpreted with caution. The etiological role of WTC exposures in these 3 cancers is unclear. Longer follow-up of rescue/recovery workers and participants not involved in rescue/recovery is needed with attention to selected cancer sites and to examine risk for cancers with typically long latency periods."
Written by Christian Nordqvist