CHRISMED Journal of Health and Research

: 2020  |  Volume : 7  |  Issue : 1  |  Page : 8--11

Effect of exposure to formalin on peripheral and smaller airways of 1st-year medical students

Dipak Kumar Dhar 
 Department of Physiology, Himalayan Institute of Medical Sciences, Dehradun, Uttarakhand, India

Correspondence Address:
Dipak Kumar Dhar
Department of Physiology, Himalayan Institute of Medical Sciences, Dehradun, Uttarakhand


Context: One of the occupational hazards experienced by a doctor is the exposure to formaldehyde during gross anatomy dissection classes. As it vaporizes at room temperature, the respiratory system is easily affected. The present study was conducted to assess the effect of formaldehyde on the smaller and peripheral airways. Aims: The study aimed to evaluate the effect of formaldehyde exposure on the smaller and peripheral airways of 1st-year medical students. Settings and Design: A longitudinal, descriptive study was conducted in the Department of Physiology, Rohilkhand Medical College and Hospital, among 1st-year MBBS students in the academic year 2015–16. Materials and Methods: The spirometric parameter, forced expiratory flow at 25%–75% (FEF25%–75%)was recorded in eighty medical students using spirometer RMS Helios 401 available in the research laboratory of the department. Percent-predicated values were used for the analysis. The baseline values were recorded at the beginning of the academic calendar and followed up at the end of the 1st, 6th, and 10th months. Statistical Analysis Used: Data were analyzed using the SPSS software. Descriptive statistics and repeated measures ANOVA were used for the analysis.P <0.05 was considered statistically significant. Results: The overall mean FEF25%–75%declined up to the 6th month following which there was a gradual correction. The overall pattern of change and the decrease in 1st month was statistically significant (P = 0.001). Conclusions: There is some detrimental effect of formaldehyde on smaller and peripheral airways which affects the ventilatory dynamics.

How to cite this article:
Dhar DK. Effect of exposure to formalin on peripheral and smaller airways of 1st-year medical students.CHRISMED J Health Res 2020;7:8-11

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Dhar DK. Effect of exposure to formalin on peripheral and smaller airways of 1st-year medical students. CHRISMED J Health Res [serial online] 2020 [cited 2020 Sep 19 ];7:8-11
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One of the various occupational hazards of a doctor is exposure to formaldehyde fumes during the phase of his education and training in medical schools, where he learns anatomy by scrupulous dissection of cadavers. These cadavers are embalmed with fluids containing formalin, which is a 37% by weight or 40% by volume aqueous solution of formaldehyde. Chemically, formaldehyde (HCHO) is the simplest aldehyde produced by the oxidation of methyl alcohol. At room temperature, it is a noxious, colorless, and flammable gas.[1] Evaporation of formaldehyde from cadavers produces a high degree of exposure among the students and the instructor[2],[3] since they handle the cadavers during dissection classes routinely. As formalin vaporizes at room temperature, it can be deduced easily that the respiratory tract is the critical target of the toxicity of airborne formaldehyde.[4],[5],[6],[7] Studies conducted on occupational exposure to formaldehyde suggest that small but significant changes occur in lung functions of exposed participants following prolonged exposure.[8] It has been suggested that formaldehyde concentrations of more than 0.5 ppm in the ambient atmosphere cause detrimental alterations in the pulmonary functions, in addition to various mucosal irritation symptoms.[9]

Formaldehyde is known to polymerize and form paraformaldehyde, which has a unique property of adsorbing formaldehyde vapors on their surface. Upon adsorption, the particles which attain an average size of 1–2 μ become respirable[10] and get carried to the terminal branches of the respiratory tract, which are the smaller and peripheral airways. On deposition, formaldehyde, being a toxic and irritant substance, would naturally incite an inflammatory reaction which would impair the ease of airflow in these smaller and peripheral airways. One of the best ways by which the peripheral and smaller airways can be evaluated is the measurement of the forced expiratory flow at 25%–75% (FEF25%–75%) on spirometry. It represents the mean FEF25%–75% of the forced vital capacity (FVC),[11] i.e. it reflects the dynamics of the middle part of forced expiration. It is also known as the maximum mid-expiratory flow.

Studies done to evaluate the effect of exposure to formaldehyde on the peripheral airways are limited. This study, therefore, intended to throw light on how formaldehyde affects the ventilatory dynamics of these airways in medical students.

 Materials and Methods

A longitudinal, descriptive study was conducted at the department of physiology among 1st-year MBBS students in the academic year 2015–16. Approval was obtained from the Institutional Ethics Committee (IEC) (vide document IEC/IRB No. IEC/27/2015). Students having no history of previous exposure to formalin were considered as participants. The exclusion criteria comprised the presence of any preexisting diseases chronic respiratory diseases such as bronchial asthma, allergic diseases, known allergy to any substance, any acute or chronic inflammatory state, altered baseline pulmonary function test, deformities of the thoracic cage or spine, extremes of height and weight, and those who were not willing to participate in the study. Eighty medical students (40 male and 40 female students) of the total 150 students, who suitably fulfilled these criteria, were selected using the simple random sampling technique. Informed consent was obtained from every participant after explaining the nature of the study. FEF25%-75% was recorded using computerized spirometer RMS Helios 401 (ISO 9001:2008) available in the research laboratory of the department of physiology. The FVC maneuver of the software was used and FEF25-75% was recorded in the sitting posture.[11] Best of three such values was recorded as per the guidelines of the American Thoracic Society.[11],[12] The baseline values were recorded at the beginning of the academic calendar and follow-up values at the end of the 1st, 6th, and 10th months. It is now recommended to use percent-predicted values of the lung functions instead of absolute values, which expresses the recorded lung functions as a percentage of the predicted normal values for a participant's age, height, weight, and ethnicity. Therefore, in the present study, percent-predicted values were used for the analysis to eliminate the confounding effect of various anthropometric and other factors. The normal range of pulmonary function parameters is considered to be within a range of 80%–120% of the predicted values and percent-predicted values <80% represent suboptimal function.[13],[14] FEF25%–75% below 80% of the predicted value is suggestive of peripheral airway obstruction.[15] Data were analyzed using the SPSS software SPSS version 13 (Manufactured by SPSS Inc., Chicago, USA). Descriptive statistics and tests such as repeated measures ANOVA were used for the analysis of the data. P < 0.05 was considered statistically significant.


The overall mean FEF25%–75% of the students was 110.28 ± 13.84%, at baseline, which showed a declining trend up to the 6th month following which there was a gradual increase toward the initial values, as shown in [Table 1]. A similar trend was observed when FEF25%–75% of the male and female students were considered separately.{Table 1}

When the statistical significance of change in FEF25%-75% was analyzed by repeated measures ANOVA, it was observed that the overall change seen in FEF25%–75% of all students over the entire study period was statistically significant (P = 0.001) and within this, a significant decrement occurred within the 1st month of exposure (P = 0.001). Furthermore, no significant difference was observed in the nature of these changes between the males and females, implying that both the genders were equally affected. The values are depicted in [Table 2].{Table 2}

The percentage of participants who manifested early obstructive changes in the peripheral and smaller airways as measured by their FEF25%–75% values below the normal range is shown in [Figure 1]. It shows that the changes in peripheral airways occurred over a cumulative exposure over some time as the maximum prevalence is seen at the end of the 6th month, which then showed a trend of reverting back to normal.{Figure 1}


In the present study, the baseline FEF25%–75% was found to be in the normal range. It decreased gradually up to the 6th month after which it increased to a certain extent over the remaining study period. However, it was not completely restored to the initial or baseline values. The overall change over the study period and among it, the decrement in the 1st month of exposure was statistically significant. A decline in this parameter but with slightly varying patterns was also noted by other researchers. Shrivastava and Saxena[16] reported a steep initial decline after the 1st month which was followed by a gradual but incomplete correction. Patil et al.,[17] on the other hand, showed a continuous decline over a period of 9 months. Hajra et al.[18] found an initial decrease after the 1st month, followed by a gradual and near-complete improvement. In a comparative study between exposed workers and unexposed participants, Alexandersson et al. found a significant decrease in FEF25%–75% among the exposed group.[19] Studies on the acute effects of exposure on medical students show no significant change on FEF25%–75% as reported by Binawara et al. and Khaliq and Tripathi[20],[21] All these indicate that the smaller and peripheral airways are affected by chronic exposure to formaldehyde vapors.

FEF25%–75% represents the functional integrity of the smaller and peripheral airways. A decrement in the parameter denotes some deleterious effects on these airways. This might occur when paraformaldehyde particles or dust particles adsorb formaldehyde on their surface and attain the respirable size. These would then act as vehicles carrying the formaldehyde to the peripheral airways in the depths of the lung. The particle size for becoming respirable is of the range 1–2 μ. Moreover, a study that attempted to measure the particle size of suspended materials in an embalming room found the mean size to be 1.6 μ[10] which is well within this respirable range.[10],[22],[23] Aerodynamic studies show that in the smaller airways where the flow velocities are usually slow, particles of this size deposit by the process of sedimentation.[10],[23] Once a toxic substance like formaldehyde reaches there, inflammation would ensue as a usual response by the body. The spectrum of histopathological changes in the respiratory tract on exposure to formaldehyde has been studied in animal models, and it ranged from acute interstitial inflammation (pneumonitis), pulmonary fibrosis to acute and chronic lung injury.[24] To worsen the situation further, formaldehyde has been found to adversely affect the mucociliary clearance of the respiratory tract, which is one of the innate immune defenses of our body. Holmström and Wilhelmsson. in a study on workers occupationally exposed to formaldehyde vapors reported that the mucociliary clearance of the respiratory tract was significantly less among the exposed group than the unexposed controls.[25] This suggests that the formaldehyde-adsorbed particles had more chances of being retained.

However, there is a slow but gradual reversion toward the preexposure or normal values after the 6th month, underlining the body's innate principle of restoring homeostasis. The duration after which complete restoration would have occurred could be best assessed by extending the follow-up further, which is an obvious limitation of the present study.


The present study demonstrates that there is some detrimental effect of formaldehyde on the smaller and peripheral airways, which affect the ventilatory dynamics, leading to a reduction of the parameter on spirometry. It resonates with the increasing reports of adverse effects of formaldehyde from different corners of the globe. We must make concerted efforts to reduce the exposure because medical students are subjected to regular exposure for the entire 1st year. Simple steps such as use of masks, goggles, improvement in the ventilation system across the dissection hall, and avoiding unnecessary spillage of formalin within the dissection hall can bring about considerable change in this regard. Other options that have been used in some places include specially-engineered dissection beds, modifying the conventional process of embalming by the use of accessory chemicals, or alternative embalming fluids.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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