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Building Health Sciences - Healthy buildings, healthy people, healthy business

Congressionally-Mandated Epidemiological Study


NSA LogoFor many years, National Security Agency (NSA) employees at the Fort Meade, Maryland complex had reported discomfort and health symptoms which were difficult to correlate with specific illnesses or building elements. Some employees continued to feel unwell at work, despite extensive efforts to investigate the cause of these symptoms and to ameliorate any potential contributors. This lack of resolution, plus the vital national mission served by NSA, led to a Congressional mandate to determine whether building conditions at the NSA Fort Meade Campus were causing employee illnesses. Building Health Sciences was selected to complete this large, congressionally-mandated epidemiological study and Health Hazard Evaluation (HHE).

Study Design

This study was complicated by the fact that it involved forty buildings and 40,000 occupants engaged in a highly-sensitive mission. We investigated many factors, both building and non-building related, that are medically and scientifically known to contribute to work-related symptoms. Many different types of statistical analyses were used to determine the best predictors of various work-related symptom outcomes. Extensive Questionnaire responses and environmental information, totaling approximately 4 million data points, were obtained and analyzed, while maintaining individual confidences and Agency security.

Data were derived from three sources:

  • An epidemiological questionnaire, completed by 7,637 volunteers
  • Extensive Indoor Environmental and Air Quality (IEAQ) sampling (over 50,000 samples); and
  • Individual HHEs of 122 volunteers, including an HHE questionnaire and individual workplace testing

Study Areas

We evaluated twelve Study buildings subdivided into 353 Study Areas (SAs). Initially, we correlated Questionnaire-reported symptoms and self-reported environmental observations to identify potential target areas for environmental sampling. We uncovered wide intra-building variations in symptom experience: the buildings, per se, were not consistent contributors to the feelings of unwellness. Rather, the NSA Fort Meade Campus, with its non-uniform forty buildings, disparate Agency operations, and multiple occupant skill communities and job functions, is actually comprised of numerous micro-environments sharing sufficient commonalities to be studied. Our extensive data enabled us to make observations from the campus level all the way down to the building, Study Areas, functional groups, and individual workstation levels. These multi-level observations informed our conclusions and recommendations.

Health Hazard Evaluation (HHE)

Our HHE protocols included a NIOSH-tailored HHE Questionnaire, Personal IEAQ sampling, and individual examinations for such factors as potential Workplace Exacerbation of Asthma (WEA), decrements in pulmonary function during the workweek, as well as allergic propensity determined by specific blood tests. We correlated the HHE Questionnaire findings with the personal sampling device environmental data to further explore the HHE participant’s perceptions of their work environment, relevant personal history and health symptoms of primarily those with asthma and respiratory symptoms. We also measured certain ergonomic and other thermal comfort issues and correlated those with various endpoints.

Testing the Hypothesis

The hypothesis was that the buildings' indoor environmental and/or other work-related conditions were adversely affecting some employees, manifested as either symptoms, illnesses, and/or impaired performance. To evaluate this, we matched self-reported symptoms, either singly or in combination, against environmental factors. The environmental factors were both subjective (self-described from questionnaire responses), as well as objective (from our actual environmental testing). We selected the investigative approaches and statistical methodologies, to ensure a high level of statistical sensitivity.

Key Findings

We reviewed an extensive amount of scientific and medical literature, millions of data points, tens of thousands of environmental samples, and thousands of statistical analyses. The key findings of the Study are listed below.

  • Response to the questions posed in the original congressional mandate
    • Nothing identified in the air of these buildings during the Study period was making people sick.
    • A variety of factors such as dry air, cleanliness, underlying individual susceptibilities, and job stress contributed to symptoms.
    • Symptoms were more closely associated with micro-environments within buildings than with either buildings themselves or campus-wide.
    • When compared to the 100 non-complaint buildings in the EPA BASE Study data, the study buildings manifested no evidence of any increased risk to health.
    • There was wide intra-building variation in the extent to which respondents indicated they experienced a particular symptom or combination of symptoms.
    • Thus, localized Study Area issues, rather than campus-wide building problems, predominated.
  • In both the epidemiological study and the HHE, relatively few reported environmental factors strongly- or directly-correlated with clinical endpoints. However, a number of factors and relationships emerged as important contributors to work-related symptom experiences that may impair optimal occupant performance. These led to some of our recommendations.
  • Relationships were observed between various factors identified in the questionnaire and loss of productivity (presenteeism) and loss of workdays (absenteeism). These are relevant because they reflect the physical or emotional discomfort of the occupants.


The health-based approach we utilized in this high profile, historically-problematic IEAQ situation at NSA resulted in uncovering significant contributors to occupant health symptoms and comfort that were not apparent in any of the previous traditional IEAQ investigations. Our findings are now being used by NSA to improve occupant health, comfort and productivity.

Lessons Learned

Further, our findings suggest that incorporation of a health-based approach into everyday IEAQ investigations and maintenance may prevent IEAQ incidents or mitigate their escalation, in addition to protecting the health and safety of the building occupants, while enhancing productivity. IEAQ investigations are complex. BHS' comprehensive, experience, research and library of both complaint and non-complaint buildings enables us to compare new IEAQ investigations' results to the vast database we have created as a result of this extensive investigation. Comparable analyses can be made for future large and small IEAQ challenges.

The NSA Epidemiological Investigation was presented to the 2009 professional conference of the American College of Occupational and Environmental Medicine (ACOEM) in San Diego, CA. If you would like the full PowerPoint presentation, contact Allan Burt.