Solution Summary: Enhanced Video Analysis of Dust Exposures (EVADE) Software Program
Enhanced Video Analysis of Dust Exposures (EVADE) is a software program developed by the National Institute for Occupational Safety and Health (NIOSH) that lets users synchronize video feed of work processes with exposure measurements from a real-time datalogging aerosol monitor. Using EVADE, this information can be viewed simultaneously, allowing workers and safety professionals to more easily identify which processes may be generating the highest levels of respirable dust or crystalline silica. EVADE is an administrative control that assists in identifying hazardous processes so that targeted steps can be taken to reduce exposures.
Traditional sampling for respirable dust or silica involves sending a sample out to a lab. The results represent an average concentration of dust or silica over a set period of time regardless of how many tasks were performed during that sampling interval. Although this is important information, it does not tell the user much about variations in the level of respirable dust or silica, how extreme these variations were, or which tasks are high-exposure and therefore priorities for engineering controls.
Real-time monitors take instantaneous measurements every few seconds, letting users identify exposure peaks or spikes. EVADE matches these data with video feed from a camera attached to a worker’s helmet or a piece of equipment. This allows users to easily identify tasks or processes associated with high periods of exposure to respirable dust or crystalline silica. Although real-time monitors primarily measure respirable dust, it is easy to figure out the respirable silica concentration if you know the percentage silica in the material being disturbed.
EVADE can directly read data downloaded from Thermo Scientific’s personal Data Ram™ 1000 (pDR-1000), Thermo Scientific’s personal Data Ram 1500 (pDR-1500), or TSI, Inc.’s Sidepak Personal Aerosol Monitor AM510, (AM-510). However, data from any other real-time monitor can be easily modified to a format usable by EVADE (see https://www.cdc.gov/niosh/mining/UserFiles/works/pdfs/2014-133.pdf, page 3). To set up your monitor, follow the manufacturer’s directions. Make sure to attach a cyclone to the inlet to remove larger, non-respirable particulate (Figure 1).
Figure 1. SGS Galson, Respirable Silica Dust Sampling (Source: https://www.youtube.com/watch?v=9LPzWn9GchQ)
Although initial testing of EVADE was performed with the V.I.O. POV HD camera, any portable unit that can be safely attached to a hardhat, vest, or piece of equipment is suitable. The camera should be positioned so that it records the majority of dust or particulate-generating tasks, without impeding the worker’s view or mobility. This usually means clipping or bracketing it on to a helmet or hardhat, pointed forward (see Figure 2).
Figure 2. Mining Magazine, 2017, Free hazard detection software from NIOSH (Source: http://www.miningmagazine.com/management/safety/free-hazard-detection-software-from-niosh/)
Although EVADE can synchronize video files and exposure data with different lengths and start times, it is easiest to start and stop video recording and real-time monitoring at the same time. Video files with the extension .avi, .wmv, and .mp4 are compatible with EVADE. There are numerous free tools online that will convert videos to .mp4 format.
Figure 3 shows a sample project that was preloaded into EVADE:
Figure 3. NIOSH EVADE 2.0.
When the user presses ‘Play’, the video file (upper right window) and data file (lower right window) play simultaneously, showing the user the exact activities performed during periods of high and low exposure to respirable dust.
Many common construction materials (brick, block, mortar, concrete, etc.) contain varying percentages of silica. Silica particles that are small enough to penetrate into the lower lung are referred to as respirable crystalline silica (RCS). RCS can cause cancer, chronic obstructive pulmonary disease (COPD) and silicosis, an incurable lung disease that leads to death.
The Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for respirable crystalline silica in the construction industry is 50 μg/m3, expressed as an 8-hour time weighted average (TWA).
Even if the materials generating dust have a very low silica percentage, respirable dust can still lead to bronchitis, pneumoconiosis, and respiratory sensitization (allergic reaction). Other types of dust, such as wood dust, can cause certain types of cancer. The construction PEL for ‘Particulates Not Otherwise Regulated (Total Dust)’ is 15 mg/m3 TWA. Although there is no construction standard for ‘Particulates Not Otherwise Regulated (Respirable Fraction),’ the general industry PEL recommends they be kept below 5 mg/m3 TWA.
How Risks are Reduced:
Workers in the construction industry often perform multiple tasks in the same shift. Even when the same task is performed consistently, tools or location may change. Because of this, it can be difficult to figure out which work processes in a given shift generate the majority of a worker’s silica exposure. Although most silicosis is chronic, resulting from 10 or more years of exposure, acute and accelerated silicosis can occur when workers are exposed to especially high levels of respirable silica dust over shorter periods of time. EVADE allows users to identify shorter periods of elevated exposure and the work processes associated with them. This information can be used to prioritize tasks for engineering controls.
Traditional sampling, which gives a time-weighted average, can hide especially high periods of exposure. A worker being sampled for 8 hours who is exposed to 1500 μg/m3 of respirable crystalline silica for 15 minutes would have an 8-hour TWA of 47 μg/m3. According to the OSHA PEL, this is within acceptable levels. However, the dose-response relationship between silica and silicosis is not entirely understood. Even in chronic diseases that appear after many years of exposure, higher peak exposures may have an influence on disease onset (Checkoway et al, 1992). Short periods of high respirable silica exposure can have the potential to contribute to acute or accelerated silicosis and are important considerations during any exposure assessment.
Identifying the specific task, tool, and environment causing worker exposure to silica can allow contractors to eliminate harmful processes or substitute more effective tools or engineering controls. If these approaches are not feasible, knowing the maximum silica concentration rather than the average promotes the use of PPE with an adequate assigned protection factor. The EVADE software interface also has a “bookmark” function that lets users flag exposure peaks so they can easily compare, contrast, and jump between different points in time.
Effects on Productivity:
Using EVADE to identify work processes associated with exposure peaks reduces the amount of time and resources that would otherwise be expended on this activity. Once hazardous processes are identified, resources like engineering controls and PPE can be more effectively allocated. Several features of EVADE, such as bookmarking and simultaneous scrolling, also allow safety professionals to communicate and share information more quickly and efficiently (Cecala, 2013). Eliminating periods of high dust exposure will also enhance visibility, improving both quality and pace of work.
Attaching a mobile video recorder to the worker eliminates the need for a second person to observe the work process as they perform monitoring. Wearing a camera or real-time datalogging aerosol monitor is not expected to have any impact on worker productivity.
EVADE Version 2.0 is currently available for download. A guide document based on EVADE Version 1.0 can be downloaded from https://www.cdc.gov/niosh/mining/UserFiles/works/pdfs/2014-133.pdf.
Although the EVADE program was originally developed for use in the mining sector, it has applications in any workplace with the potential for exposure to respirable dust or crystalline silica. It is currently available for Windows computers only. EVADE does not record video or take exposure measurements, but rather allows for easier, quicker, and more informative synchronization of pre-existing video and real-time exposure measurements.
Using direct reading aerosol monitors, EVADE can also be used for other solid aerosols such as lead-based paint dust. Hardware or software modification may be required for tasks involving exposures monitored by other direct reading instruments.
Bruce Lippy, PhD, CIH, Jean Christophe Le, MPH, Jim Platner, PhD, CIH , Sara Brooks, MPH, CPH - CPWR The Center for Construction Research and Training
National Institute for Occupational Safety and Health
To obtain information, visit EVADE 2.0 or contact 1-800-232-4636