SHIPYARD WELDERS & FUME EXPOSURES

Joseph Nelson’s grandmother worked in the shipyards during World War II. So, it seemed fi tting that his graduate research project, studying welding fume exposures, led him to three regional shipyards. Nelson, who works with Professor Noah Seixas, wanted to characterize welding fumes and identify exposures to welders. From this information, he plans to develop a statistical model designed to predict worker exposure in different situations.

Predicting worker exposures in this setting isn’t easy. Welders don’t typically weld for eight hours straight, said Nelson. The exposures can vary by duration of welding activity, size of the space, and type of ventilation used. The welder or someone else can set up the ventilation. The ventilation system, even when present, may be ineff ective. For example, in the hull of a ship, a welder may be far away from ventilation, or a welder may use a fan for ventilation, which circulates the air and cools the worker but doesn’t get rid of the fumes.

There’s another caveat, Nelson explains. In ship repair, electricians, carpenters, plumbers, painters, and pipe fitters may be working in the same space as a welder. He often observed adjacent-worker exposure to welding fumes. One common scenario in ship repair, Nelson said, is the pairing of a welder with a fire watch worker, who watches for fires and holds a fire extinguisher in one hand and a radio in another. The fire watch is likely exposed to the same fumes as the welder, but the fire watch is not necessarily wearing the same protective equipment, such as respirator.

With the help of Field Group staff, Nelson connected with these shipyards where Nelson collected 165 eight-hour personal samples of welding fumes from more than 60 welders. With the EH Lab staff’s assistance, Nelson analyzed these samples for 10 different metals and total particulates. He hopes the data will help employers in the shipyards set policy around welder exposures and affect worker practices.

Before his graduation with a master’s degree in Exposure Sciences in June 2009, Nelson will present results from the study and the model he is developing for predicting exposure at the American Industrial Hygiene Association Conference in Toronto, Canada. He hopes his study will be expanded and used to help with epidemiological studies of shipyard welders and welder fume exposures.

BUS DRIVERS AND VIBRATION

Ryan Blood downloads vibration signal data to his laptop.
Photo by Seong Hwang.

Based on workers’ compensation data from King County Metro, a substantial number of claims from bus drivers were associated with low-back pain or injury, explained doctoral student Ryan Blood. In many of the claims, bus drivers cited bouncing and jarring of the bus as the reason for their back pain.

In 2004, King County Metro asked the Field Group to help determine sources of these back injuries, and the Field Group worked with Associate Professor Pete Johnson to investigate the problem. The relationship between low-back pain and exposure to whole body vibration has been established in prior research, and in 2005, Johnson received departmental funding to measure whole body vibration exposures in King County Metro’s bus drivers.

Blood worked with Johnson to characterize average vibration exposure and to develop a special instrument to measure “impulsive shocks,” which occur when a bus driver hits a speed bump or a pothole. These shocks are as significant to whole body vibration exposure as average vibration exposure. Blood explains that a bus driver on a smooth freeway all day and another bus driver unexpectedly driving over a few potholes while driving on city streets will be exposed to different types of vibration.

Seats can greatly influence whole body vibration exposures. At King County Metro, the current bus seat allows a driver to adjust the seat forward or back, set the firmness of the back support, and modify the seat suspension or stiffness.

In 2007, Blood and Johnson worked with King County Metro on another study to evaluate the ability of three different seats to “absorb” vibration exposures. All seats performed similarly, but the researchers found the seat suspension setting had a signifi cant eff ect on whole body vibration exposures. A more rigid seat resulted in lower exposures. Blood and Johnson also found the driver’s weight was an important factor. Results showed that a heavier person experiences less vibration than a lighter person. With seats designed to accommodate the heaviest drivers, other drivers may experience higher vibration levels.

In the same study, freeway driving resulted in higher average vibration exposures than city-street driving. Since the type of street and bus route affects exposures, a possible solution may be to rotate the higher exposure routes among drivers, said Johnson.

Blood and Johnson’s next step is to compare vibration exposures in diff erent types of buses. King County Metro has high-floor buses, low-floor buses, articulating buses, and coach buses. The researchers will study how each bus performs on varying road types and routes. Ultimately, the goal of their work is to identify factors that influence whole body vibration exposures in bus drivers and to provide administrative and engineering solutions that could effectively reduce exposures and risk of chronic back injury.

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