Crystalline Silica and RSP Control Methods Effectiveness during Concrete Grinding

Akbar-Khanzadeh, Farhang

Abstract

Concrete surface grinding generates one of the highest levels of crystalline silica dust in the construction industry, exposing concrete grinders to unacceptable levels of this highly toxic chemical linked to a variety of respiratory and other diseases. The proposed study, a follow up of our recently completed pilot project funded by the National Institute for Occupational Safety and Health (NIOSH) through the Center to Protect Workers' Rights, covers multiple NIOSH NORA priority areas: intervention effectiveness research, chronic pulmonary diseases, control technology and exposure assessment. This study's long-term goal is to characterize/prevent silica dust exposure during construction activities. It's short-term goal is to determine the feasibility, limitations and effectiveness of additional available dust control methods in enhancing existing dust control methods during concrete grinding. Our pilot study confirmed previous studies' findings, including our study in 2002, that the commonly used approaches do not reduce silica dust to acceptable levels. The proposed study will demonstrate the effects of major relevant influencing factors and will reveal the combinations of those factors that effectively control silica dust. The study will be performed in a controlled environment (a field laboratory) to collect data. Silica dust sampling parameters (factors) will be as follows: (a) grinding techniques: uncontrolled 1 (conventional-grinding), controlled 2 (wet-grinding and ventilated- grinding); (b) grinder diameter sizes: 3 (4.5-inch, 7-inch and 9-inch); (c) general ventilation position: 2 (on, off); (d) sampling time set up: 3 (conventional- grinding 5,15, 25 min, wet-grinding 30, 45, 60 min, ventilated- grinding 45, 60, 90 min); (e) control method flow-rate: conventional-grinding 1 (0, no water or airflow), wet- grinding water flow 3 [0.2, 0.4, 0.8 L/min/inch diameter], and ventilated-grinding airflow-rate 3 (0.25, 0.50, 1.0 L/min/inch diameter). Thus, the (1 x 3 x 2 x 3 x 1) factorial design applies to uncontrolled conventional- grinding and the (2 x 3 x 2 x 3 x 3) factorial design applies to wet-grinding and ventilated-grinding. At each factor level, 2 personal samples (replicate) will be collected and their average value will be reported as the silica concentration for that factor level. The total resulting number of air samples will be 252. For quality control, 28 blank, 30 background and 20 bulk samples will also be collected. Multiple analyses of variance will be used to analyze the data to find the desired combination of factors. ? ? ?