The Availability and Validity of Information on Children Exposed to the 9/11/2001 Disaster

In 2002, the World Trade Center Health Registry (WTCHR) was established in New York City’s Department of Health and Mental Hygiene to monitor the health of people directly exposed to the 9/11 attacks in NYC. The WTCHR monitors the short and long-term (20+ years) physical and mental health conditions caused by the terrorist attacks among exposed responders and civilian survivor populations. Enrollees include rescue, recovery, and clean-up workers; residents of lower Manhattan; people who worked in the office buildings and businesses in the affected area; passersby, and children enrolled in schools in lower Manhattan at the time of the attacks. The registry publishes updates on the health of this population regularly. Notably, the more than 71,000 enrollees in the WTCHR have formed a foundation for supporting robust prospective research into the health and well-being of its members.

During the registration period, children under age 18 were enrolled by their parents. These children either lived (2379) or went to school (753) South of Canal Street in Lower Manhattan on September 11, 2001. Children have been the subject of multiple WTCHR studies. To date, the WTCHR has ten publications on a wide range of health outcomes in children, including asthma, reproductive outcomes, substance use, behavioral issues, and PTSD. In addition, several publications include both children and adults, among which several are focused on cancer. As the youth population has progressed into adulthood, a heightened concern regarding the long-term effects of youth exposure to 9/11 has led to closer scrutiny of existing information for research. As a result, an effort was made to find out how the population who were enrolled as children in the WTCHR represent all the children who lived South of Canal Street or were in schools in that area. Assessing the representativeness is important for a complete understanding of this potentially vulnerable population’s health conditions related to 9/11 exposure.

Overall, the study found that the WTCHR’s youth cohort is representative of the population at risk on many attributes including age for ages <15 years, sex, and to a lesser extent income and race/ethnicity. Specific findings within attributes include:

• Age: Overall, the proportion of the WTCHR youth cohort who were residents and who were younger than 15 years is similar to the exposed population based on the 2000 census population. Children 15 and older at the time of 9/11 are slightly underrepresented, most likely because they were young adults (aged 18 years or older) when enrollment began (2003–2004) and were more difficult to reach for recruitment than younger children.
• Race/Ethnicity: The youth studied were slightly higher in proportions of White, Black, and Hispanic enrollees compared to the 2000 census. In contrast, Asian, and other (e.g., multiple endorsements of race/ethnic membership) youth appear slightly underrepresented in the WTCHR.
• Sex: There were no significant differences between male and female children studied when compared to the 2000 census population.
• Household Income: When comparing household incomes, WTCHR and census proportions were similar in the lowest income category (<$25,000). However, there were slightly fewer enrollees than expected in the middle-income category ($25,000–$50,000) and slightly more in the highest category (>$50,000) when compared with the 2000 census population

In conclusion, the WTCHR has successfully recruited and retained a sufficiently large and representative group of enrollees necessary to investigate health conditions among persons exposed to 9/11 as children. Although disaster studies are generally not designed to estimate population parameters, the WTCHR’s group of 9/11-exposed children represents the population at risk in many ways and knowing the extent of differences informs research planning. Given its size and diverse population, the WTCHR is well positioned for health effects research involving 9/11 youth now and moving into the future.

The study, “Scientific Value of the Sub-Cohort of Children in the World Trade Center Health Registry”, was recently published in the International Journal of Environmental Research and Public Health.

To read the complete paper on this topic or other research publications by the World Trade Center Health Registry visit the WTCHR website.

Learn more about 9/11 health effects research on the World Trade Center Health Program research webpage.

Robert M. Brackbill, PhD, MPH, James E. Cone, MD, MPH, Mark R. Farfel, ScD, and Paul Gambino are with the New York City Department of Health and Mental Hygiene and are grantees of the World Trade Center Health Program.

Emma Butturini, MPH; Robert D. Daniels, PhD, CHP; and Travis Kubale, PhD are with the World Trade Center Health Program.