On November 30, 2007, NIOSH received a request from managers at Aduddell Restoration and Waterproofing, Inc. for an HHE at the Ballston Mall Parking Garage in Arlington, Virginia. The managers wanted to know if the employees were adequately protected against silica and MDI during parking garage repair. Full-shift PBZ air samples for respirable particulates and silica were collected on four employees over 2 days. The amount of MDI monomer in a bulk sample of Part A and Part B was measured. We also evaluated the curing time after mixing MDI-containing Part A and the inert Part B. Employees were exposed to hazardous levels of respirable crystalline silica during jackhammering and sandblasting. Of the eight PBZ air samples for respirable dust and silica, seven reached or exceeded the silica (as quartz) ACGIH TLV of 0.025 mg/m3, and five reached or exceeded the NIOSH REL of 0.05 mg/m3. None of the samples exceeded the OSHA PEL. Approximately 52% of the bulk sample of Part A was MDI monomer. Part B contained no MDI monomer. A quantitative analysis of the reaction between Part A and Part B showed that approximately 80% of the MDI monomer reacted in the first 10 minutes. At 60 minutes, the mixture was hardened. We considered inhalation exposure to MDI unlikely because of the low vapor pressure of MDI, the relatively short curing time between the MDI-containing Part A and the inert Part B, and the method used to pour and apply the MDI-containing slurry. However, we believed there was a potential for dermal exposure to MDI that could result in sensitization, asthma, and contact dermatitis. We interviewed all 10 employees who were working during our site visit

none reported work-related health concerns. The company provided the appropriate type of respirator for crystalline silica and required employees to wear it. However, not all job tasks requiring respirators were clearly defined. Additionally, employees were neither respirator fit-tested nor did they clean or maintain their respirators properly. We recommend informing employees that MDI monomer may still exist after Parts A and B are mixed together and requiring them to wear butyl rubber gloves when mixing these compounds. We also recommend requiring employees to wear respirators during jackhammering and sandblasting. The company's respirator program should comply with the OSHA Respiratory Protection Standard. Additional recommendations included exploring possible engineering controls to reduce dust levels while jackhammering and sandblasting

complying with the OSHA Hazard Communication Standard

evaluating employees' exposure to noise during jackhammering and sandblasting activities

providing antivibration gloves to employees who use vibrating tools such as jackhammers

wearing eye protection while sandblasting, jackhammering, or mixing and applying filler material

and establishing a smoking cessation program.