Dear Editor,

In the recent Acta Anatomica Nipponica (Kaibogaku Zasshi Vol. 85, No. 1, 2010)—a special issue concerning the improvement of the formaldehyde (FA) environment in gross-anatomy laboratories—four papers were published, two of which described originally developed dissection tables equipped with local ventilation systems (Shinoda and Oba 2010; Kikuta et al. 2010) and two of which outlined the environmental health hazards caused by FA (Uchiyama 2010; Sakamoto and Miyake 2010). Due to its effectiveness and low cost, the FA solution is widely used in Japanese medical and dental schools to embalm human bodies donated for use in gross anatomy dissection classes. However, the gaseous FA that evaporates from embalmed bodies causes not only acute irritation to the eyes and respiratory tract but also chronic non-threshold carcinogenicity. According to a risk-based evaluation of FA, the Ministry of Health, Labor, and Welfare in Japan has set the administrative level of FA to 0.1 ppm in working environments in which FA is handled.

In our medical school, the dissection laboratory for students (L23 × W12 × H3.3 m, in which 20–23 bodies prepared with 10 l of 5.5% FA/30% ethanol solution are used) had a high-performance general (whole-room) ventilation system with a competence of 25000 m3/h; however, the mean FA concentration of the room (“A” measurement) and the estimated maximum exposure to FA (“B” measurement) during dissection classes were 0.520 and 0.480 ppm, respectively (HPLC analysis performed by Panasonic Health Organization Science Center of Industrial Hygiene, Osaka, Japan). To reduce FA exposure during dissection classes, we introduced 23 dissection tables with local ventilation apparatus (Meiko Medical, Fukuoka, Japan). The details of this system have already been described elsewhere (Shinoda and Oba 2010). Briefly, the system consists of a simple plenum-chambered dissection table and a transparent vinyl duct which connects the table to the pre-existing general ventilation duct via a flow control valve in the ceiling. The 40 pre-existing, randomly oriented air-supply openings in the ceiling were not replaced (no downward flow of air for each dissecting table). The total ventilation flow rate was 18 m3/min/table.

The local ventilation system we introduced successfully reduced the FA concentration of the room during dissection classes. The A and B FA measurements were 0.035 and 0.054 ppm, respectively. Using a photoelectronic method (FP-30, Rikenkeiki, Tokyo, Japan), we also measured the 30-min mean FA concentration at the center of the dissection room (1.2 m above the floor) and at the corner of a dissection table (0.5 m above the table) in every class 30–60 min after the start of the dissection (Fig. 1). The mean FA concentrations at the center of the room and the corner of the table were 0.056 (n = 41) and 0.057 ppm (n = 41), respectively. FA concentrations higher than 0.1 ppm were recorded for dissection schedules #8 and 9, during which the upper extremities were placed in the abducent position; thus, the source of the FA was out of the effective range of the local ventilation system. Thirty-nine of the 41 measurements of FA concentration at the center of the room and 40 of the 41 measurements at the corner of the dissection table did not exceed 0.1 ppm, and 37 of the 41 measurements at the center of the room and 35 of the 41 measurements at the corner of the table were less than 0.08 ppm (the indoor air-quality guideline level for FA in normal workplaces).

Fig. 1
figure 1

Formaldehyde (FA) concentrations during dissection classes involving the use of a local ventilation system. Dissection schedules: 1–4, introduction and superficial structures of the trunk, neck, and back; 5, intermediate structures of the neck and thoracic wall; 6–12, upper limb; 13–14, deep structures of the back; 15, abdominal wall; 16–18, thorax; 19–25, lower limb; 26–33, abdomen; 34–41, head and deep structures of the neck. A (0.1 ppm), administrative level of FA in workplaces handling FA; B (0.08 ppm), guideline level of FA for normal workplaces

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In this letter, we report that connecting a dissection table with a local ventilation system to a pre-existing general ventilation duct successfully reduced FA exposure during dissection. However, the FA concentration exceeded 0.08 ppm during the dissections of specific regions (Fig. 1), so it may be necessary to consider additional strategies for FA reduction, such as downward flow of air supply above the table (Shinoda and Oba 2010) and the utilization of personal protective equipment by students with hypersensitivity to FA (Akbar-Khanzadeh and Pulido 2003). The well-arranged transparent ventilation duct between the dissection table and a flow-control valve in the ceiling did not affect the view and the movements/activities of the students in the laboratory. In conclusion, an appropriate device for reducing the FA concentration in dissection laboratories protects individuals from FA toxicity and may also improve the learning efficiency of medical students.