|Year : 2019 | Volume
| Issue : 2 | Page : 212-216
Effect of exposure to formaldehyde on the forced vital capacity of medical students: A longitudinal study
Dipak Kumar Dhar1, Sudeepa Chaudhuri2
1 Department of Physiology, Himalayan Institute of Medical Sciences, Swami Rama Himalayan University, Dehradun, Uttarakhand, India
2 Department of Physiology, Rohilkhand Medical College and Hospital, Bareilly, Uttar Pradesh, India
|Date of Submission||18-May-2019|
|Date of Decision||22-Aug-2019|
|Date of Acceptance||26-Aug-2019|
|Date of Web Publication||16-Dec-2019|
Dr. Dipak Kumar Dhar
Department of Physiology, Himalayan Institute of Medical Sciences, Swami Rama Himalayan University, Jolly Grant, Dehradun, Uttarakhand
Source of Support: None, Conflict of Interest: None
Background and Aim: Formaldehyde exposure is one of the various occupational hazards experienced by a doctor during his life. There is consistent and regular exposure to formaldehyde during the gross anatomy dissection classes. Since it vaporizes at room temperature, respiratory system is easily affected. The present study was undertaken to assess its effect on forced vital capacity (FVC) of medical students. The aim of this study is to evaluate the FVC of the 1st year medical students after exposure to formaldehyde. Materials and Methods: A longitudinal study was conducted in the Department of Physiology among 1st year MBBS students. The spirometric parameter FVC was recorded in 80 medical students using spirometer RMS Helios 401. Percent predicated values were used for analysis. The baseline values were recorded at the beginning of the academic calendar and followed up at the end of 1st, 6th, and 10th months. Data were analyzed using the SPSS. Descriptive statistics and repeated measures ANOVA was used for the analysis. A value of P < 0.05 was considered statistically significant. Results: The mean FVC declined significantly over the 1st month of exposure following which there was a gradual reversion to the baseline values over the remaining study period. The cumulative pattern of this change was also statistically significant (P = 0.000). Conclusion: Formaldehyde causes detrimental changes on the ventilatory mechanics of the lung. The effect is marked in the initial phase following which the body tries to restore homeostasis.
Keywords: Forced vital capacity, formaldehyde, medical students, ventilatory derangement
|How to cite this article:|
Dhar DK, Chaudhuri S. Effect of exposure to formaldehyde on the forced vital capacity of medical students: A longitudinal study. Arch Med Health Sci 2019;7:212-6
|How to cite this URL:|
Dhar DK, Chaudhuri S. Effect of exposure to formaldehyde on the forced vital capacity of medical students: A longitudinal study. Arch Med Health Sci [serial online] 2019 [cited 2020 Apr 10];7:212-6. Available from: http://www.amhsjournal.org/text.asp?2019/7/2/212/273075
| Introduction|| |
Health care has been the epicenter of human civilization since the beginning. A doctor, therefore, plays a very vital role in society. However, during the period of their medical education and training, doctors are exposed to a wide spectrum of occupational hazards ranging from chemicals to biological agents. One of the earliest of these is exposure to formaldehyde, which occurs in the 1st year when gross anatomy is taught with the help of cadavers. A medical student learns about the basics of the body's structure by scrupulous dissection of cadavers. These cadavers are embalmed with the help of embalming fluids which chemically is a composite mixture of various substances acting as fixatives, preservatives, germicides, buffers, wetting agents, anticoagulants, dyes, perfuming agents, etc. Formalin, which is a 37% aqueous solution of formaldehyde is used as the preservative in these fluids. The formalin concentrations in arterial fluid and cavity fluid are 10% and 60%, respectively. While keeping a provision for spillage, approximately 10 l of arterial fluid are needed for an adult body weighing 65–75 kg. Formalin on vaporization yields formaldehyde. Therefore, medical students during the 1st year are regularly exposed to formaldehyde in anatomy dissection classes. Studies have documented that evaporation of formaldehyde from cadavers produces considerable amount of exposure to the students and the instructor.,
Chemically, formaldehyde (HCHO) is the simplest aldehyde and is produced by the oxidation of methyl alcohol. At room temperature, it exists as a gas which has noxious properties and a strong pungent odor. The safety of formaldehyde is now a matter of rising concern and debate. Today, there is substantial corpus of evidence in the medical research literature which shows that formaldehyde can be toxic, allergenic, and even carcinogenic on prolonged exposure., Apart from its irritant effects on exposed surfaces of the body, the respiratory tract is its critical target of toxicity because formalin vaporizes at room temperature to produce air-borne formaldehyde.,,, It has been found that its levels more than 0.5 ppm in the ambient atmosphere causes derangement of pulmonary functions and a concentration of around 50 ppm has been associated with chemical pneumonitis. The fundamental physiological basis of all these effects of formaldehyde lies in its high reactivity. The oxygen atom of aldehyde group of formaldehyde is highly electronegative which has the propensity to react easily with nucleophilic sites on cell membranes and cause changes at cellular level. The high reactivity also produces tissue inflammation either due to chemical injury to the cells or allergenic mechanism.
Forced vital capacity (FVC) is defined as the maximal volume of air exhaled with the maximal forceful effort from a maximal inspiration. The recording of FVC, therefore, involves both the phases of the respiratory cycle, i.e., inspiration and expiration. A diminution in any of the components, maximum inspiration or a forceful expiration, either separately or in concert would reduce the amount of FVC recorded, thus making FVC as one of the most sensitive parameters to record inadequacy in pulmonary ventilation. Formaldehyde has been found to affect both the upper and lower respiratory tract. Studies have suggested that it affects ventilatory dynamics in both the central and peripheral airways,,, implying that there is state of constriction of the airways, either due to its chemical irritant nature or a possible IgE-mediated mechanism. Formaldehyde also polymerizes to form paraformaldehyde which has a unique property of adsorbing formaldehyde vapors on its surface. On adsorption, the particles which attain an average size of 1–2 microns become respirable. These particles easily get carried to the depths of the lungs. Being a chemical irritant and noxious agent, formaldehyde could naturally incite an inflammatory reaction. Chronic inflammation and epithelial injury followed by repair would eventually herald a process of fibrosis, thus attenuating the expansion of the lung parenchyma to variable degree.
The available research suggests formaldehyde causes small but significant changes in lung functions of occupationally-exposed subjects following prolonged exposure. The present study was, therefore, intended to observe its longitudinal effect on the 1st year medical students as the dissection hours provide a portal of consistent exposure over the 1st year.
| Materials and Methods|| |
A longitudinal, descriptive study was conducted in the Department of Physiology among 1st year MBBS students in the academic year 2015–2016. Prior approval was obtained from the Institutional Ethics Committee. Students having no history of previous exposure to formalin were considered as subjects. Those with prior 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, smokers, and those who were not willing to participate were excluded from the study. Eighty medical students (40 male and 40 female students) out of the total 150 students were selected employing simple random sampling technique. Before recording the parameter, the nature of the study was explained to every participant, and informed consent was taken. FVC was recorded using computerized spirometer RMS Helios 401 (ISO 9001:2008) available in the research laboratory of the Department of Physiology (Sample recordings depicted in [Figure 1] and [Figure 2]). Measurements were done in the sitting posture. Best of three such values were recorded as per the guidelines of the American Thoracic Society (ATS)., The baseline values were recorded at the beginning of the academic calendar and follow-up values at the end of 1st, 6th, and 10th months. The current guidelines recommend expressing the recorded lung functions as a percentage of the predicted normal values for a subject's age, height, weight, and ethnicity, in the form of percent-predicted values. Therefore, in the present study, percent predicted values have been used for analysis to eliminate the confounding effect of various anthropometric and other factors. With this method, 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., When race-specific references are not available, the ATS, European Respiratory Society, and American College of Occupational and Environmental Medicine recommend use of a scaling or adjustment factor on the Third National Health and Nutrition Examination Survey standards. To account for larger thoracic cages observed in Caucasians when compared with Asians of the same age, height, and gender, it is recommended that the predicted values be multiplied by 0.88 to obtain appropriate Asian reference values., Such provisions are nowadays engineered within the computerized spirometry software, as used in the present study. The appropriate ethnic correction factor was selected in the Helios software before recording the parameter. The data were analyzed using the SPSS (Manufactured by SPSS Inc., Chicago, USA) software. Descriptive statistics and tests such as repeated measures ANOVA was used for analysis of the data. A value of P < 0.05 was considered statistically significant.
|Figure 2: A sample flow-volume curve of a subject recorded using RMS Helios 401|
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| Results|| |
The pattern of changes observed in FVC and forced expiratory volume in 1 s (FEV1) is shown in [Table 1] and [Table 2]. [Table 3] and [Table 4] show the cumulative changes over the whole-study period were statistically significant. On analysis of the change during the intervals, it can be observed that the decrement in 1st month of exposure was significant, following which there is a gradual correction. Significant improvement occurred after 6 months. The effect was similar in both males and females, except for the 1st month of exposure where a steeper decrease was seen in males.
|Table 1: Percent predicted values of forced vital capacity of the participants over the study period|
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|Table 2: Percent predicted values of forced expiratory volume in 1 s of the students over the study period|
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|Table 3: Significance of change in forced vital capacity on exposure over different spans of time and difference in the effect on male and female participants|
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|Table 4: Significance of change in forced expiratory volume in 1 s on exposure over different spans of time and difference in the effect on male and female students|
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| Discussion|| |
The detrimental effects of formaldehyde exposure on pulmonary mechanics of the participants as observed in the present study are consistent with the fundamental biological behavior of formaldehyde and resonate with similar research works carried out elsewhere by other authors. In our study, a significant decrease was noticed after 1 month of exposure, which subsequently reverted slowly to normal and by the end of the 10th month, it was close to the baseline value. Similar findings were also reported by Shrivastava and Saxena and Hajra et al. However, the pattern differed from Patil et al. who observed that a significant decline in FVC occurred over 9 months of exposure. The decrement in FVC as observed in our study is also in line with other studies on occupational exposure to formalin reported by Alexandersson et al., Holmström and Wilhelmsson Kilburn et al., and Uthiravelu et al. A meta-analysis of 12 studies also concluded that there was a decrease in FVC. With regard to FEV1, our findings were similar to Hajra et al. However, it does not conform to that of Shrivastava and Saxena and Patil et al. who have documented a significant decline in FEV1 over 11 and 9 months, respectively.
There is a multitude of mechanisms by which formaldehyde exerts its effects on the body's physiology. It has been proposed that most likely near 100% absorption of inhaled formaldehyde vapors occurs in the upper respiratory tract as it is highly soluble in water. Once absorbed, the binding of formaldehyde to endogenous proteins creates “haptens” that can elicit an immune response. Chronic exposure to formaldehyde has been associated with immunological hypersensitivity as shown by elevated circulating IgE levels. IgE-mediated allergy is often accompanied by variable amount of constriction of the airways due to contraction of the bronchial smooth muscle. Chemical inflammation which could also exist concomitantly because of the irritant nature of formaldehyde would also contribute to constriction of airways as the different biological mediators released during inflammation such as histamine and serotonin are known to cause contraction of smooth muscles. Third, formaldehyde is known to polymerize and form paraformaldehyde in long term. Studies report that paraformaldehyde particles have been detected in air samples in many places where embalming is carried out. These particles have a unique property of adsorbing formaldehyde vapors on their surface. The particles which attain an average size of 1–2 μ become respirable and get carried to the depths of the lung, where they are deposited. A similar sequence of events could also occur if the formaldehyde vapors get adsorbed on the dust particles and they reach the critical size. The string of events that follow once formaldehyde vapor comes in contact with lung parenchyma has been studied in animal models which showed that there is a dose and duration-dependent alteration in the cytoarchitecture of the epithelium of the lungs. The spectrum ranged from acute interstitial inflammation (pneumonitis), pulmonary fibrosis, and acute purulent bronchitis to acute and chronic lung injury., It was also observed that especially the type II pneumocytes which are the source of pulmonary surfactants bore the brunt of the injury along with the other cells. Reduced amount of surfactant would impair the ease of airflow as a natural consequence. In addition, Holmström and Wilhelmsson in their study on workers occupationally exposed to formaldehyde vapors have reported that the mucociliary clearance of the respiratory tract, which is one of the innate immune defenses of our body, was significantly less among the exposed group than the unexposed controls. This suggests that the formaldehyde-adsorbed particles had more chances of being retained as compared to other substances due to its effect on the ciliary functioning. Occupationally, exposed chemicals and pharmaceuticals such as formaldehyde are also etiological agents of a type of interstitial lung disease called extrinsic allergic alveolitis which are usually accompanied by a restriction of the lung expansion.
However, it has also been suggested that on long term the body tends to correct some of the change, as also observed in our study. The exact mechanisms, however, remain to be unveiled. Some authors have stated that a time period of around 10 weeks after the exposure is needed for recovery to the previous values. This underlines the governing principle of homeostasis in human physiology.
| Conclusion|| |
The study highlights the detrimental effects of formaldehyde on pulmonary ventilation. We must, therefore, make concerted efforts to reduce exposure of the medical students because they are subjected to formaldehyde on a daily basis during the 1st year. Simple methods like use of masks and goggles, better ventilation facilities across the dissection hall and avoiding unnecessary spillage of formalin within the dissection hall premises can markedly cut down on the exposure. 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. This approach will preserve the health and proficiency of the future caregivers in the long run.
The authors gratefully acknowledge Rohilkhand Medical College and Hospital where the study was carried out and the first-year medical students for their wholehearted participation.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4]