The Health Hazard Evaluation Program received a request from a management representative at a federal government agency concerned about potential employee exposures to erionite mineral fibers when maintaining dirt roads in areas where erionite was confirmed or was suspected to be present. We visited two field offices to assess potential employee exposures to erionite and respirable crystalline silica (quartz) during road maintenance activities in October 2012 and August 2013. Erionite is a naturally occurring mineral found in fine-grained sediments such as volcanic ash deposits that have been altered by weathering and ground water. Erionite deposits have been identified in all of the western states except Washington. We observed employees blading and grading dirt roads, replacing culverts and cattle guards, replacing aggregate on parking lots, and pulverizing and analyzing rock samples. We took air samples for mineral fibers and crystalline silica and bulk rock and soil samples to analyze for erionite. We found that employees doing road maintenance activities could be exposed to quartz above the recommended limits. Area air samples indicated a high percentage of quartz, up to 100%. Zeolite mineral fibers, a class of fibers that includes erionite, were not found in the personal air samples. None of the bulk rock samples collected in the areas surrounding where employees worked contained erionite. Because of the variable environmental and geological conditions encountered by the employees and the variability in job tasks, including tasks that aerosolize dust particles, the potential for exposure to erionite and silica dust exists. Therefore, minimizing dust exposure during dust-generating activities is prudent. To address the potential for exposure to dust that may contain erionite or crystalline silica, we recommended the employer (1) not use aggregate that contains erionite to repair roads, (2) maintain air filters in the equipment regularly, (3) wet the soil before doing road maintenance, (4) schedule dust-generating tasks on days when the soil is moist, and (5) provide employees with clothes that are solely designated for work activities. We also recommended monitoring employees' exposure to respirable crystalline silica, and training employees in proper work practices for working in areas that contain crystalline silica or erionite. We recommended employees keep the windows and doors on equipment closed, and not bring work clothing home.