Controlling Formaldehyde Exposure
A Case Study in an Academic Gross Anatomy Lab
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It is well known that work in a gross anatomy lab presents the potential for exposure to formaldehyde in concentrations that exceed established occupational exposure limits. All too often, these labs are relegated to basements or older facilities that lack adequate exhaust ventilation to properly control for hazards from formaldehyde exposure. Addressing these situations can require creative approaches.
The University of Utah School of Medicine has five gross anatomy labs located in a small, aging facility where effective management of formaldehyde exposure to students and staff proved challenging. The labs are used during the spring semester for both wholesale dissections of cadavers as well as more limited “prosections” of tissue and organ samples performed as demonstrations for students of the medical and dental schools. The labs are also in use during the fall semester for limited prosection work. Specimens used during these classes are fixed with formalin.
Historical exposure assessments in these spaces showed formaldehyde levels that varied widely depending on the situation but which, in most cases, exceeded established OELs. The ventilation system in the building was found to be inadequate to control observed levels in the spaces, and due to the way the building had been constructed, upgrading the ventilation system as a whole was basically impossible and extremely cost prohibitive. Instead, a variety of control strategies was explored.
SAMPLING METHODOLOGY An extensive round of sampling was conducted in the spring of 2019. To evaluate student and worker formaldehyde exposures during anatomy classes, specimens were positioned in the labs as they would have been during a typical lab class. Air sampling was then conducted using passive diffusion badges in each of the five labs. In some cases, lab staff wore respiratory protection and conducted various dissections and other activities to mimic conditions during normal laboratory classes.
For most evaluations, formaldehyde passive diffusion monitoring badges were hung or suspended adjacent to the dissection tables and at breathing-zone height approximately 2–3 feet from the specimen. The badges were left in place for the duration of the simulated lab classes—a full eight hours in some cases. After the sampling period, the badges were collected and sent for analysis. Figure 1 illustrates the typical setup for the sampling.
Figure 1. Initial sampling setup with passive monitoring badges.
Sampling was conducted throughout the building as well to determine formaldehyde concentrations in non-laboratory spaces during dissection classes. This sampling verified that an exposure risk was not present outside of the lab spaces.
Sampling determined that the gross anatomy labs were above the OSHA action level of 0.5 ppm and, in some cases, the permissible exposure limit of 0.75 ppm, both measured as eight-hour time-weighted averages. On Nov. 12, 2019, the university’s EHS director, in conjunction with the dean of Health Sciences, decided to halt all gross anatomy lab classes until the situation could be properly controlled. Lab classes were moved to a virtual format for the remaining weeks of the spring semester; the fall semester lab classes were rescheduled and moved into a different laboratory facility on campus.
Different control approaches were discussed with the user group, which included the lab director, teaching assistants, and members of the university’s Body Donor Program. After each control was attempted, the EHS team conducted sampling to determine the level of success, using the initial sampling as a baseline for comparison. The remainder of this article describes the various control strategies.
CONTROL STRATEGY 1: USE REDUCTION The first control strategy attempted was to reduce the number of tables and cadavers from six to three in each of the five labs. Sampling without any simulated use conditions showed levels that were the same or above baseline exposures. Sampling with lab staff in respirators simulating actual use conditions showed that half the samples were at or above the OSHA action level, with three above the PEL. Statistical analysis showed with a 95 percent confidence interval that this entire dataset would be above the PEL. Use of a fan to simulate air movement from people walking around the room showed similar results.
Based on these results, it was determined that the number of cadavers in the room does not change observed exposure levels.
CONTROL STRATEGY 2: USING ONLY PROSECTIONS Next, sampling was performed using only prosections and not full cadavers. The procedures performed in these labs included neuroanatomy, general anatomy, dental, and gross anatomy. All the sampling done for prosections came back under the OSHA PEL and action level, so these labs were cleared for resumption of classes only when working with smaller prosections. This strategy was only partially successful since students’ coursework required working with full cadavers.
CONTROL STRATEGY 3: DOWNDRAFT VENTILATION A small pilot program in one of the anatomy labs that had been initiated in 2018 was finished in the spring of 2019. A mechanical engineer was engaged to design a downdraft ventilation system that would work with the existing exhaust system in the building. This presented a difficult challenge in that the existing exhaust was inadequate and there was limited physical space available to upgrade the ducting and exhaust capacity. Five of these new ventilated downdraft tables were installed as shown in Figure 2.
Figure 2. Installed downdraft tables.
Once the project was finished, an exposure assessment was conducted to evaluate the effectiveness of the new downdraft table ventilation system. The first round of sampling showed that the new system was still inadequate and levels in excess of the PEL were still present. The EHS team determined that the system was not working properly and found that the airflow was not set to the desired rate. Adjustments were made to the system, and a second round of sampling showed that the new system was successful in controlling the exposure and observed levels were below both the PEL and the more protective ACGIH Threshold Limit Value of 0.1 ppm (eight-hour TWA). The five samples taken ranged from 0.024 ppm to 0.043 ppm.
CONTROL STRATEGY 4: PORTABLE FUME EXTRACTORS For the four remaining labs, the manager of the facility that houses the gross anatomy labs suggested that we try a fume extractor system that is usually used for welding. Three portable fume extractors were purchased, and the university’s metal shop was enlisted to design and fabricate vents to be added to the sides of the dissection tables, creating a makeshift downdraft table. Three prototype exhaust systems were built and attached to the dissection tables as shown in Figure 3.
Sampling was conducted using the three available flow rate settings (high, medium, and low) on the fume extractor units. An additional sample run was conducted using a configuration of two tables connected to a single fume extractor unit set to the highest flow rate. (See Figure 4 for diagrams of the sampling configurations.) Formaldehyde passive diffusion badges were placed in the breathing zone above each cadaver and on three students while they performed dissections in the lab equipped with the prototype exhaust systems. Badges were left in place for the normal dissection duration, approximately 2–3 hours.
The eight-hour TWAs for the 18 samples taken ranged from 0.13 ppm to 0.65 ppm, with only two results above the OSHA action level. These were observed during the test that utilized two tables sharing a single fume extractor unit. It was determined that the prototype exhaust system with a single extractor unit run on low and attached to only one table successfully controlled observed formaldehyde levels to below the action level. Sampling also verified that use of the high setting decreased the overall effectiveness of the units, although levels were still below the action level.
Figure 3. Prototype exhaust systems using portable fume extractors were built and attached to the dissection tables. From top left: an unmodified table (A), a table outfitted with a fume extractor (B), views of the modified table from the side (C) and top (D), the new filter (E), the side vent fabricated at the university’s metal shop (F), and the filter attachment underneath the table (G). (Click or tap on the figure to open a larger version in your browser.)
OVERALL STRATEGY IMPLEMENTATION This process of discovery showed that both downdraft ventilation and portable fume extractors were effective in controlling exposures in the labs. It was determined that the most cost-effective control strategy was to procure additional fume extractor units and deploy the prototype system for all tables in the gross anatomy labs. Clearance was given to resume gross anatomy lab classes for the spring 2022 semester pending installation of the new systems.
Once the new prototype systems were deployed on all tables in the four labs, sampling was conducted during normal use conditions—that is, during actual lab classes with students present. Formaldehyde passive diffusion badges were placed in the breathing zone area above one cadaver in each room and on four teaching assistants while they performed dissections with students participating in the class. Badges were left in place for the entire duration of the three-hour class. The fume extractor units were all set to the low setting. The eight samples taken ranged from 0.6 ppm to 0.13 ppm (eight-hour TWA), well below the OSHA action level.
Additional sampling was performed with five of the new tables in one room to verify results and increase the number of people able to dissect (see Figure 5). Observed formaldehyde levels ranged from 0.01 ppm to 0.04 ppm (eight-hour TWA)—not only well below the OSHA action level but also below the TLV.
Figure 4. Sampling configurations for lab tables modified with portable fume extractors. Tests 1 and 2 (left) were conducted on three tables, each with its own filter and with the extractor set to low, medium, or high as indicated. For Test 3 (right), two of the tables were attached to the same fume extractor set to high, while the third table had its own fume extractor set to high. (Click or tap on the figure to open a larger version in your browser.)
Figure 5. Layout of gross anatomy lab during sampling to verify controls. Each table was modified with portable fume extractors. (Click or tap on the figure to open a larger version in your browser.)
Moving forward, sampling will be conducted each spring semester to verify continued efficacy of the fume extractor-based exhaust systems. Use of these systems is not without difficulties. Filter change-out schedules will need to be maintained, for example, and filters represent a recurring cost. This study has shown, however, that fume extractors can be an effective tool for controlling formaldehyde exposure in the anatomy lab setting.
MATT LUNDQUIST, CIH, graduated from Utah State University with a degree in industrial hygiene. He is currently a senior industrial hygienist for the University of Utah.
The author thanks Kerry Peterson, David Morton, and Geoff Dorius for their help and contributions.
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