Measurements of chlorinated dibenzo-p-dioxins (CDD) and chlorinated dibenzofurans (CDF) in three different occupational environments were made by NIOSH. Air sampling to determine potential inhalation exposures to CDD and CDF were conducted at a municipal incinerator in Philadelphia, Pennsylvania, an electrical transformer metals reclamation facility in Ashtabula, Ohio, and a paper mill in Rumford, Maine. Additionally, the potential for skin exposure was determined by collecting surface wipe samples for CDD and CDF from the incinerator and metals reclamation facility. The municipal incinerator CDD/CDF toxic equivalent airborne concentrations ranged from 0.01 to 20.4 picograms/cubic meter (pg/m3), and the CDD/CDF toxic equivalent surface concentrations ranged from 0.4 to 43.5pg/m3. CDD/CDF airborne concentrations at the metals reclamation facility ranged from 0.1 to 6.2pg/m3, and surface toxic equivalents were between 2.7 and 36.1pg/m3. The paper mill had CDD/CDF toxic equivalents ranging from 0.01 to 0.06pg/m3. The authors conclude that potential inhalation exposures to both CDD and CDF measured at the metals reclamation facility and the incinerator are near or more than the National Research Council (NRC) guideline of 10pg/m3. Surface levels of CDD and CDF are also above the NRC guideline of 25pg/m3, indicating that skin exposure is probable.