On February 8, 2002, the National Institute for Occupational Safety and Health (NIOSH) received a joint request from the Sergeant at Arms Office at the United States Senate and the Chief Administrative Officer at the United States House of Representatives regarding health concerns related to handling and opening irradiated mail at the United States Senate and House office buildings in Washington, D.C. In response to the request, NIOSH representatives conducted environmental and epidemiologic evaluations at the Russell, Dirksen, Hart, Cannon, Longworth, Rayburn, and Ford Buildings, the Senate Post-Office Screening Facility, the House Mail Processing Facility, the Capitol building, and Postal Square on February 13-15, 2002. The environmental evaluation included air sample collection for carbon dioxide, temperature, and relative humidity as well as for contaminants potentially derived from heated mail as a result of irradiation, including small and total particulate, volatile organic compounds, formaldehyde, ozone, carbon monoxide, toluene diisocyanate, and polynuclear aromatic hydrocarbons. In addition, bulk samples of irradiated mail and mail that had not gone through the irradiation process were analyzed for anions, metals, and pH. The epidemiologic evaluation consisted of interviews with individual employees who handled or had concerns about the mail, meetings with the Senior Medical Officer from the Office of the Attending Physician (OAP), and review of data collected by the OAP. Air samples indicated non-detectable or low concentrations of sampled contaminants. The types and levels of airborne substances we measured in areas where irradiated mail was handled were not distinguishable in a meaningful way from those measured in areas where irradiated mail was not handled. This comparison was hindered in a few cases where employee interviews revealed that mail volumes and/or mail opening activities were lower on the day that samples were collected. We do not suspect that daily variability of the mail load will have an effect on the results of our environmental evaluation based on the number of buildings and offices evaluated, the number of samples collected, and the low concentrations of any detectable compounds. Many of the volatile organic compounds that were detected are common in indoor air, and the results of the sampling for these compounds generally are similar to results seen by NIOSH in other indoor environments. The bulk sample analysis did not provide information that could link irradiated mail to the reported health effects. . Among the 389 Congressional staff employees interviewed, the most common symptoms were headache, skin irritation, eye irritation, skin rash, dry hands, nausea, and nose or throat irritation. We believe that it is likely that multiple factors are responsible for the reported symptoms. The added dryness of the mail from the irradiation process can lead to dryness and skin irritation from repeated handling of the mail. This is due to the absorptive effect of the damaged cellulose fibers from the irradiated paper drawing moisture off the skin. This drying effect can cause the outer layer of the skin to dry out and fissure, causing chapped and irritated skin. Individuals with a history of atopy (allergies) may have been particularly vulnerable. The we observed in our environmental survey can also exacerbate the symptoms of eye and skin irritation that were seen. In general, established guidelines for occupational exposures are based on the goal of preventing and minimizing measurable adverse effects in healthy populations. They are not based on avoidance of odors, and many chemical odors can be detected by smell at levels below exposure guidelines. Some odors can be detected by humans at levels below those detectable using industrial hygiene techniques. There is evidence that irritation can be produced from volatile organic compounds at very low levelsólevels which would trigger the activation and amplification of the neurosensory mechanisms for an odor threshold (activating the sense of smell), but potentially below levels that we could measure for some compounds. Thus, odors could potentially trigger irritant symptoms experienced by the employees, including some of the mucous membrane irritation and headaches. Adding to the unfamiliar and unpleasant odors causing headaches and irritation, skin irritation, and mucous membrane irritation, was the fact that these occurrences happened in a climate of heightened awareness and unusual anxiety in these Government Buildings due to recent terrorist acts. It is possible that this heightened awareness and resultant employee stress, while not a root cause of the problem, may have contributed to problems caused by the handling of the very dry irradiated mail. Environmental samples collected across several Capitol Hill building locations over a three day period did not reveal any exposures exceeding any existing occupational guidelines. In addition, exposures in irradiated mail locations were not demonstrably higher than exposures in control locations where no mail was opened. These findings are similar to what has been found in other recent investigations of irradiated mail. Medical interviews did result in finding a fairly high number of individuals reporting symptoms of irritation. As noted above, the absorptive effect of the irradiated paper drawing moisture off the skin could account for some of the symptoms, other irritant symptoms may be due to odors associated with the mail, still others due to the and heightened awareness. Therefore, it is likely that a number of causes were responsible for the reported symptoms. Recommendations are provided in the report.