The Centers for Disease Control and Prevention (CDC) published a September 20, 2012, Federal Register notice seeking comment on a proposed National Institute for Occupational Safety and Health (NIOSH) exposure assessment and epidemiological study of U.S. workers exposed to carbon nanotubes (CNT) and carbon nanofibers (CNF). The notice states that the proposed research is a cross-sectional study of the current U.S. workforce involved with CNT and CNF in manufacturing and distribution, to be conducted in two phases: (1) an industry-wide exposure assessment study to evaluate worker exposure and further develop and refine measurement methods for CNT and CNF; and (2) a cross-sectional study relating the best metrics of CNT and CNF exposure to markers of early pulmonary or cardiovascular health effects. The study will include a questionnaire given by NIOSH personnel as a computer-assisted personal interview, followed by medical examinations to evaluate pulmonary function and blood pressure, and collect sputum and blood. NIOSH will conduct statistical analyses to determine the nature of the relation between exposure to CNT and CNF and these biomarkers of early effect, considering potential confounding factors such as smoking, age, gender, and workplace coexposures, including non-engineered ultrafine particles. CDC invites comments on whether the proposed research is necessary for the proper performance of its functions, including whether the information shall have practical utility; the accuracy of its estimate of the burden of the proposed collection of information; ways to enhance the quality, utility, and clarity of the information to be collected; and ways to minimize the burden of the collection of information. Written comments are due within 60 days of the notice.