Evaluating the influence of ambient conditions in the cooking space of railway pantry car using selected thermal indices and physiological parameter

Abstract

BACKGROUND:

Hot and humid indoor environment of the kitchen affects worker performance. The Indian Railway’s pantry car culinary is one of them that cooks food for the on-board passengers, which could be bothered by the hot indoor climate.

OBJECTIVE:

The current study aimed to identify the indoor working environment of the railway “pantry car” using heat stress indices such as “Universal Thermal Climate Index-UTCI,” “Wet-Bulb Globe Temperature-WBGT,” “Discomfort Index-DI,” “Tropical Summer Index-TSI,” “Heat Index-HI,” and Heart Rate-HR with clothing insulation. METHODS: The study was performed in 2018 (August-summer season) to collect field survey data on 6 railway pantry cars. Measurements were carried out during peak cooking times such as morning “7 : 00 am”, day “11 : 30 am”, evening “4 : 00 pm,” and night “6 : 30 pm”. This study’s descriptive and Pearson’s correlation analysis was accomplished using SPSS version 2016 software.

RESULTS:

The analysis results revealed that the average values were for UTCI (37.77±5.26°C), WBGT (30.42±2.28°C), DI (30.05±2.70°C), TSI (33.21±2.90°C), HI (48.53±4.86°C), correspondingly. During analysis, the strongest correlation association was observed between “TSI and DI” (r = 0.985, p < 0.000) and WBGT and TSI (r = 0.958, p < 0.000). A “significant correlation” was found between UTCI and HI (r = 0.637, p < 0.05). While no signification correlation was found between “heat stress indices and physiological parameters (p > 0.05)”.

CONCLUSION:

In this study, all the heat stress index limit values showed highly harsh working conditions inside the pantry car, which created unfavorable circumstances for the culinarians. Inappropriate “ventilation design” could be a reason for discomfort in the railway pantry car.

Keywords

Heat stress Indoor environment kitchen railway Environmental ergonomics thermal comfort heart rate

1. Introduction

Proper design of the indoor workplace environment enhances workers’ productivity and health. However, most developing countries, including India, still face issues such as “occupational health, “safety hazards,” “work-related diseases,” “injuries,” and “heat impact on occupants”. Extreme heat occurrences have had serious negative effects on China as well. In 2020, heat waves in China were blamed for around 15,000 fatalities [1]. In a similar vein, almost 50,000 people died in Russia during the 2010 heat impact [1]. In 2021, the effects of heat in North America claimed the lives of about 500 individuals [2].

Heat stress is described as a hazardous physical mechanism in workplaces such as brick industries, mining, farming, foundry sector, etc [3]. While some researchers also reported that there is a problem of heat stress in commercial kitchen environments [4]. But there is no study focused on the railway pantry car kitchen environment regarding heat stress. While a few studies conducted on railway pantry car kitchen’s thermal environment, they focused on thermal comfort issues using predicted mean vote (PMV), predicted percentage of dissatisfied (PPD), & standard effective temperature (SET) indexes [5, 6].

Heat stress causes thermal fatigue disorder, and muscle cramps among workers [7]. Accordingly, prolonged heat exposure conditions can also cause heat exhaustion and heat stroke issues, which will affect the health and productivity of workers [8]. The higher values of environmental heat stress affect workers’ health by affecting “sweat rate”, “core body temperature”, and “pulse rate” [9]. Similarly, Vatani et al. [8] stated that the efficiency of workers also decreases with higher heat exposure limits. An increase in the heat stress level impacts more chances of kidney-related problems among the workers [10]. Crandall and Wilson [11] indicated that increased heat stress influences the heart rate (HR). Almost 14 million employees working in different manufacturers in the USA were suffering from heat-related difficulties as per the US Bureau of Labor in 2004 [12]. Krishnamurthy et al. [13] specified that millions of poor employees face high heat exposure issues in the workplace in India during the summer season.

Many elements specify the occupational heat stress like temperature, humidity, air velocity, clothing level, and activity rates of workers [9]. All element’s values significantly differ according to workers’ environment, occupation, and personal characteristics [9]. Nowadays, different types of heat stress indices are used to assess indoor thermal environmental conditions in diverse areas in many countries such as; Universal Thermal Climate Index (UTCI) in Iran (Brick industries) [8], in Berlin (Building environment) [14]; Wet-Bulb Globe Temperature (WBGT) in India (Glass manufacturing plant, Steel industry, Kitchen in hostel mess) [4, 15, 16]; Discomfort Index (DI) in Iran (Rolling mill, Workshop of brick kilns) [17, 18], in Indonesia (Macro-Environmental station) [19], in Taiwan (Heavy-oil power plants and coal-fueled power plan) [20]. Similarly, Tropical Summer Index (TSI) in Iran (Mine sector) [12], in India (Building sector) [21]; Heat Index (HI) in U.S.A (University of South Florida) [22], accordingly in Switzerland, HI used in buildings environments [23].

Indian Railway’s (IR) pantry car plays an essential role in serving food to on-board passengers in the Indian Railway Catering and Tourism Corporation (IRCTC) [5, 6, 24]. The IR pantry car is usually like a kitchen that cooks food for the passengers throughout the day while the train stops and proceeds [25, 26]. Currently IR offers two different styles of railway pantry cars: Linke-Hoffmann-Busch (airconditioned) and Integral Coach Factory (non-air conditioned). However, earlier investigations found no distinction in the cooking environment between models of pantry cars with air conditioning and those without. A pantry car accommodates 3–5 chefs, 2 railway employees, and 1 food contractor. Most of the time, the indoor environment of the kitchen of the IR pantry car gets very hot due to the whole day’s cooking process [27, 28]. These types of hot and humid working environments inside the kitchen of the pantry car lead to generating occupational heat stress issues [29, 30]. This hot and uncomfortable indoor weather affects workers’ health and productivity. There are no studies that specifically address heat stress in pantry car chefs. However, Alam et al. [5] carried out a thermal comfort study on Indian Railways to predict the comfort zone of the kitchen staff and suggested a temperature of 18.50–27.80°C for the summer and 17.80–25.50°C for the winter. Similarly, in airconditioned and non-airconditioned pantry car kitchens, the study suggested comfort zone (20–27.02°C) and neutral temperature (23.5°C) with significant p < 0.05 and coefficient of correlation 0.72 [24]. Also, a previous study determined that PMV (3.10) and PPD (99%) for chefs in non-airconditioned pantry cars. Similarly, the PMV and PPD indices for chefs in air-conditioned pantry cars were (2.21) and (85%), which indicated a warm and hot environment throughout the cooking process [6]. Subjective observation also showed that 76% of the cooks did not accept the thermal conditions while cooking inside the pantry car [5].

The research suggests that heat stress is a significant problem for occupants who work in indoor environments such as railway pantry car kitchens. Using heat stress indices like UTCI, WBGT, DI, TSI, and HI, numerous studies have examined environmental heat stress in diverse regions across multiple nations. While few studies have discussed thermal comfort levels among chefs in IR pantry cars. But the literature regarding heat stress issues, particularly on IR pantry kitchens, has been found to be negligible. Therefore, the current study aimed to fill these research gaps by determining the ambient conditions in the IR pantry car using physiological measures (heart rate) and heat stress indices (UTCI, WBGT, DI, TSI, and HI). The research hypothesized that a detailed examination of the thermal, physiological, and clothing parameters would help understand the ambient condition of the IR pantry car.

2. Method

2.1. Study design

The cross-sectional study was conducted on the kitchen environment of Indian Railway pantry cars in 2018 (August- summer season). In this study, a total of “6” railway pantry cars were taken for field measurement. Measurements were taken in August during the cooking period (morning “7 : 00 am”, day “11 : 30 am”, evening “4 : 00 pm” and night “6 : 30 pm”) inside the pantry car kitchen [at the center of the cooking area]. The measurement was done only in the daytime because chefs closed the cooking process between 8 : 00 pm and 9 : 30 pm. All environmental parameters were measured during the experiment according to ASHRAE 55 and ISO 7730 standards [5, 6].

This study only targets cooks (chefs) in the kitchen of railway pantry car. Other employees/workers have not been considered as they are not continuously staying inside the kitchen area/zone. In India, 338 trains move with pantry cars, according to a report by the Railway Board [5, 6, 24]. Usually, 3 to 5 chefs work in a single IR pantry car [5, 6, 24]. A random sample size of approximately 29 was estimated in this study with a 95% confidence level and a 20% confidence interval. The total number of chefs was determined to be 1360 throughout “338” trains. Thus, 29 cooks from 6 IR pantry cars took part in the experiments for this research.

2.2. Ethics approval

The study obtained ethics approval from the student research committee (SRC), Punjab Engineering College, Chandigarh, approved the study protocol [Reference number: PEC/PED/38A].

2.3. Measurement of physiological parameter

Sixty-nine workers (chefs) have participated in this research for physiological measurement. In this study, only the chefs’ heart rate (HR) was measured during cooking time with the help of Polar V800 without troubling chefs’ work performance inside the kitchen of the IR pantry car. Researchers have utilized this validated and calibrated equipment to gather workers’ HR [12, 31]. The present study measured the chefs’ resting heart rate (R-HR) and working heart rate (W-HR). The time interval difference between resting R-HR and W-HR) time was 10 min.

2.4. Measurement of thermal/environmental parameters

In this study, thermal parameters such as “wet bulb temperature-Twb”, “air temperature-Ta”, “dew point temperature-Tdp”, and “relative humidity-RH” were measured with the help of the Kestrel weather meter 4500. At the same time, “air velocity-Va” was measured with the help of a Thermal anemometer testo-405i. While “globe temperature-Tg” was recorded with a 6-inch black-globe thermometer. The accuracy and range of these instruments were suitable as per ASHRAE standard [5, 24]. All thermal parameters were measured “1.1 m (43 in.) above the floor and at 0.3 m (1 ft) distant at the workstation (where the employees were working during the peak operating hours of a working day”, which was appropriate for the kitchen environment [6, 32].

2.5. Calculation of heat stress indices

2.5.1. Universal Thermal Climate Index (UTCI)

UTCI was produced as a “standard criterion” for assessing “heat stress in the light of human meteorology” [12, 33]. Environmental parameters (including air temperature-Ta, mean radiant temperature-Tmrt, relative humidity-RH, and air velocity-Va) are needed to determine this index [12, 33]. The general expression of UTCI has given in Equation (1) [8].

UTCI = f (Ta; Tmrt; Va; RH)

(1)

Vatani et al. [8] suggested Tmrt equal to Ta for estimation of UTCI in an indoor environment. Therefore in this study, UTCI was calculated accordingly. The sensation/stress values of UTCI is such as; “extreme cold stress (< – 40°C)”, very strong cold stress (–40 to –27°C)”, “strong cold stress (–27 to –13°C)”, “moderate cold stress (–13 to 0°C)”, “slightly cold stress (0 to +9°C)”, “no thermal stress (+9 to +26°C)”, “moderate heat stress (+26 to +32°C)”, “strong heat stress (+32 to +38°C)”, “very strong heat stress (> +46°C)” [33].

2.5.2. Wet-bulb globe temperature (WBGT)

The WBGT index is widely used to determine “heat stress” in a “thermal environment”. Equation (2) is used in this study to calculate the “WBGT index”, which was recommended according to ISO 7243 standard for indoor environment [8].

WBGT = 0.7 Twb \times 0.3 Tg

(2)

Where Twb = natural wet-bulb temperature, and Tg = globe temperature.

The “exposure risk level for WBGT” are classified as; “extreme danger (≥30°C)”, “danger (28–30°C)”, “extreme-caution (23–28°C)”, “caution (18–23°C)”, “no danger (<18°C)” [33, 34].

2.5.3. Discomfort index (DI)

It is a vital indicator that calculates the “human heat sensation for different climate conditions” [35]. The higher the amount of DI, the greater rate of discomfort [3]. As given in Equation (3), in this study, DI was appraised by the grouping of “air temperature-Ta” and “relative humidity-RH” with “some correction factor related to the thermal degree of discomfort perceived by the user in a work environment” [3, 36].

DI = Ta - 0.55 \times (1 - 0.01 RH) \times (Ta - 14.5)

(3)

The discomfort conditions of DI is such as; “no discomfort (21°C)”, “under 50% population feels discomfort (21–24°C)”, “most 50% population feels discomfort (24–27°C)”, “most of population suffers discomfort (27–29°C)”, “everyone feels severs stress (29–32°C)”, “state of medical emergency (32°C)” [36].

2.5.4. Tropical summer index (TSI)

It is an “empirical heat stress index,” emphasizing the “Indian climatic” situations [12, 37]. Equation (4) represents the mathematical relationship of TSI [12].

TSI = 0.308 \times Twb + 0.745 \times Tg - 2.06 \sqrt{(} Va + 0.841)

(4)

Where; Twb = “wet bulb temperature (°C)”, Tg = “globe temperature (°C)”, Va = “air velocity (m/s)”. TSI “thermal sensation values” and “temperature range” are categorized such as; “cold (<19.0°C)”, “slightly cool (19.0–25.0°C)”, “comfortable (25.0–30.0°C)”, “slightly warm (30.0–34.0°C)” and “hot (>34.0°C)” [3, 37].

2.5.5. Heat Index (HI)

HI is the association between “ambient temperature and relative humidity versus skin (or apparent) temperature” [38]. In the current study, HI was employed to determine the working conditions inside a railway pantry car. With the support of “Kestrel weather meter 4500,” HI has been recorded directly during physical measurement. The values of HI “temperature limits” and “working conditions” are categorized as; “caution (27–32°C)”, “extreme caution (32–41°C)”, “danger (41–54°C)”, “extreme danger (over 54°C)” [39].

2.6. Validity and reliability of the tools

The Kestrel Weather Meter 4500, a 6-inch black-globe thermometer, and the thermal anemometer Testo-405i have been used by previous researchers to measure thermal parameters in kitchens/hot, humid environments that comply with ASHRAE-55 and ISO standards for accuracy, validity and reliability [3, 24, 26, 29, 30]. Also, Polar V800 (for measuring heart rate), whose reliability and validity were found satisfactory (r = 0.99, 95% confidence intervals) for workers [40, 41].

2.7. Data analysis

In the current study, as the amount of data was less than 50, normality testing was performed using the Anderson– Darling test. The “normality hypothesis (p-value < 0.05)” was tested using a non-parametric test. A descriptive analysis of thermal parameters, indices, heart rate, and clothing values was performed, with mean, standard deviation, maximum, and minimum values obtained using Microsoft Excel 2016. Further “Pearson’s correlation analysis” was executed using the “IBM SPSS Statistics” package version 2016 to identify the significant level between various heat stress indices.

3. Results

3.1. Demographic details of IR pantry car chefs

The IR “pantry car” cook’s demographic details were (in mean and standard deviation) such as: age “36.87±6.36” year, height “171.03±5.17” cm, weight “68.18±6.28” kg, body mass index “23.32±2.03” kg/m², everyday operating period “12.07±1.95” hour, everyday relaxing period “7.71±0.57” hour. While employment experience was (in percentage) as like: less than 1 year (10.14%), 1 to 2 years (21.76%), 3 to 5 years (36.23%), and more than 5 years (31.87%).

3.2. Analysis of environmental, physiological, and other parameters

As shown in Table 1, descriptive analysis was used for analysing environment parameters, physiological parameters, and thermal indices. The data has been presented in average, standard deviation, maximum, and minimum. In this study, during the data analysis, the temperature/heat stress value was found to be maximum during the cooking time (11 : 30 am – 4 : 00 pm) and minimum during the cooking time (7 : 00 am – 9 : 00 am).

Table 1.
Parameters of thermal, physiological and personal.

Variable Average Standard deviation Maximum Minimum

Thermal parameters Twb (°C) 29.60 2.24 34 26

Ta (°C) 32.42 3.02 37 26.10

Tdp (°C) 28.33 1.24 31 26.10

Tg (°C) 32.30 2.59 37 28

RH (%) 75.83 3.86 87 69

Va (m/s) 0.03 0.05 0.20 0.00

Heat stress indices UTCI (°C) 37.77 5.26 47.25 28.17

WBGT (°C) 30.42 2.28 34.43 26.41

DI (°C) 30.05 2.70 34.20 24.80

TSI (°C) 33.21 2.90 37.52 27.25

HI (°C) 48.53 4.86 58 40

Physiological R-HR (bpm) 69.71 1.57 73 67

parameters W-HR (bpm) 83.71 3.75 90 77

Other parameters Clothing (Clo) 0.54 0.15 0.90 0.30

	Variable	Average	Standard deviation	Maximum	Minimum
Thermal parameters	Twb (°C)	29.60	2.24	34	26
	Ta (°C)	32.42	3.02	37	26.10
	Tdp (°C)	28.33	1.24	31	26.10
	Tg (°C)	32.30	2.59	37	28
	RH (%)	75.83	3.86	87	69
	Va (m/s)	0.03	0.05	0.20	0.00
Heat stress indices	UTCI (°C)	37.77	5.26	47.25	28.17
	WBGT (°C)	30.42	2.28	34.43	26.41
	DI (°C)	30.05	2.70	34.20	24.80
	TSI (°C)	33.21	2.90	37.52	27.25
	HI (°C)	48.53	4.86	58	40
Physiological	R-HR (bpm)	69.71	1.57	73	67
parameters	W-HR (bpm)	83.71	3.75	90	77
Other parameters	Clothing (Clo)	0.54	0.15	0.90	0.30

During the analysis highest average of temperature was found for Ta (32.42°C) and Tg (32.30°C), respectively. Accordingly, the maximum temperature range was found only in Ta (37°C) and Tg (37°C). The minimum temperature was observed in the case of Twb (26°C). While the minimum temperature value (26.10°C) was identical for both Ta and Tdp. The RH average was 75.83%, with a range between 87% to 69%. Similarly, a low mean air velocity (0.03 m/s) was marked inside the IR “pantry car kitchen”. Throughout the “cooking period”, the value of environmental parameters “did not comply with the ASHRAE standard”. ASHRAE referred that comfort conditions should follow a temperature range of “24.5 to 27.0°C” for summer and “19.5 to 22.5°C” for winter seasons [5, 6]. The current study recorded physiological parameters such as heart rate while working (W-HR) and resting (R-HR). The mean value of W-HR and R-HR was found 83.71 to 69.71 bpm respectively. The W-HR maximum and minimum were 90 to 77 bpm. Similarly, for R-HR, it was 73 to 67 bpm.

The average value of UTCI was 37.77°C, which indicated “strong heat stress” issue for workers. While the “maximum and minimum” range of UTCI was found to be 47.25°C (extreme heat stress) to 32.42°C (moderate heat stress), as represented in Table 2. Whereas the previous study suggested that for UTCI ideal stress is not more than +26°C [12, 33]. Accordingly, the WBGT index’s average value was 30.42°C with “extreme danger” conditions for employees. And the maximum and minimum range was 34.43°C (extreme danger) to 26.4°C (hot extreme caution). Other heat stress indices in this study suggested dissatisfaction with the train pantry car’s inability to accommodate cooking within the kitchen.

Table 2.

Various indices temperature ranges and exposures.

Indices	Range	Value	Work exposure/sensation
UTCI	Maximum	47.25	Extreme heat stress
	Minimum	28.17	Moderate heat stress
WBGT	Maximum	34.43	Extreme danger
	Minimum	26.41	Hot extreme caution
DI	Maximum	34.2	State of medical emergency
	Minimum	24.8	Most 50% population feels discomfort
TSI	Maximum	37.52	Thermal sensation hot
	Minimum	27.25	Comfortable
HI	Maximum	58	Extreme danger
	Minimum	40	Extreme caution

3.3. Correlation analysis of environmental, physiological, and other parameters

In this study, bivariate correlation analysis (i.e., Pearson’s product-moment correlation, two-tailed test) was performed using the IBM SPSS 26 software package (at 0.05 significance level; with confidence interval = 95%), as depicted in Table 3. From the correlation analysis, strong positive associations (p-value < 0.01) were observed among respective heat stress indices. As seen, the relationship of the “highest correlation coefficient” value was found between TSI and DI (with “correlation coefficient” (r) = 0.985). Subsequently, the “second-highest correlation coefficient” was seen between WBGT and TSI (r = 0.958). For UTCI, the highest correlation was observed with TSI (r = 0.945), and DI (r = 0.944) indices followed by WBGT index (r = 0.891). While the “lowest correlation coefficient” was observed between UTCI and HI (r = 0.637). Also, no statistically significant relationship was found between thermal indices and physiological parameters (p-value > 0.05). The clothing insulation (Clo) indicated a significant negative association (p < 0.05) with globe temperature (r = –0.562), also with the HI (r = –0.581) and WBGT (r = –0.516). Figure 1 (a, b, c, d) shows the correlation analysis among “heat stress indices” viz UTCI, TSI, WBGT, DI.

Figure 1.

Scatter plot of relationship between heat stress indices among IR pantry car workers (a), (b), (c) and (d).

Table 3.

Correlation analysis of environmental, physiological, and other parameters.

Variable		Heat indices
		UTCI		WBGT		DI		TSI		HI
		R	P-value	R	P-value	R	P-value	R	P-value	R	P-value
Heat stress indixes	UTCI (°C)	–	–	0.891	0.000	0.944	0.000	0.945	0.000	0.637	0.001
	WBGT (°C)	0.891	0.000	–	–	0.916	0.000	0.958	0.000	0.805	0.000
	DI (°C)	0.944	0.000	0.916	0.000	–	–	0.985	0.000	0.727	0.000
	TSI (°C)	0.945	0.000	0.958	0.000	0.985	0.000	–	–	0.781	0.000
	HI (°C)	0.637	0.001	0.805	0.000	0.727	0.000	0.781	0.000	–	–
Physiological parameters	R-HR (bmp)	–0.078	0.717	–0.071	0.742	–0.090	0.675	–0.113	0.599	–0.222	0.298
	W-HR (bmp)	0.073	0.735	0.122	0.571	0.112	0.601	0.068	0.752	–0.064	0.765
Other parameters	Clothing (clo)	–0.240	0.258	–0.516	0.010	–0.415	0.044	–0.447	0.029	–0.581	0.003

Heat Indices: UTCI – “Universal Thermal Climate Index”, WBGT – “Wet-Bulb Globe Temperature”, DI – “Discomfort Index”, TSI – “Tropical Summer Index”, HI – “Heat Index”. Physiological parameters: R-HR – “Resting Heart Rate”, W-HR – “Working Heart Rate”.

4. Discussion

The present study observed thermal parameters such as Ta (37–26.10°C), Twb (34–26°C), RH (87–69%), and Va (0.20–0.00 m/s). While some studies indicate that in indoor work environments, comfortable temperatures should be “between summer (23–26°C) and winter (21–23°C)” [6, 26]. However, Alam et al. [5] stated that the values of RH should be between the “comfortable range (30% to 60%)” and the “optimum range (40% to 60%)” and assumed “ideal RH for 50% ”. Similarly, the velocity range should be for “summer (<0.25 m/s) and winter (<0.15 m/s)” [5, 26]. The present study recorded thermal parameters beyond the recommended limits suggested by previous authors. The estimation of UTCI and WBGT indices in this study showed that the pantry car’s interior was thermally unsatisfied during cooking. Alam et al. [30] stated that the <18°C is a suitable work condition for occupants in an “indoor environment” such as a railway “pantry car kitchen”. While DI indicated “everyone feels severe stress” with an average value of 30.05°C. At the same time, during cooking, “maximum and minimum” values ranges were found to be 34.20°C to 24.80°C. Which defined the discomfort level from a “state of medical emergency” to “most 50% population feels discomfort”. Previous authors stated that the DI < 21 was directed to no discomfort in the working environment scenario [36]. But the present research represents different discomfort scenarios while “working inside the kitchen” of IR pantry car. Accordingly, inside the pantry car, TSI predicted a slightly warm thermal sensation with a mean value of 33.21°C. And thermal sensation range was found to be between hot (37.52°C) to comfortable (27.25°C). TSI found different consequences, such as comfortable sensations within the cooking periods. Alam et al. [30] reported in the study the value of TSI should be 21°C for no discomfort in a kitchen environment such as an IR pantry car. However, the work condition was “danger,” with a temperature of 48.53°C in HI. The lowest HI value was 40°C, which revealed “extreme caution” for workers.

In this study, heart rate values slightly differed due to the workers’ age factor. A previous study stated that the expected R-HR range for grown-ups “ages 18+” is from “60 to 100 bpm” [42]. During major physical activity, the targeted “heart rate” is approximately “70–85% ” of the “maximum heart rate” [43]. Individual parameters such as clothing insulation were found to be 0.54clo. As per ASHRAE standards, it should be 1.0 clo and 0.5 clo for summer and winter seasons respectively [5]. This study’s consequences estimate the assembled fabrics’ values according to the recommended range.

The research revealed the highest link between “TSI and DI” (r = 0.985, p < 0.000) and WBGT and TSI (r = 0.958, p < 0.000), indicating good agreement between the respective thermal indices. A “significant correlation” was discovered between UTCI and HI (r = 0.637, p < 0.05). There was no significant link between “heat stress indices and physiological parameters (p > 0.05)”. Similarly, Zarea et al. [12] stated that the most robust correlation value of found between “UTCI and WBGT” (r = 0.44, p < 0.0001). Also, they have found “no significant correlation” between “heat stress indices” and “workers’ physiological parameters” (p > 0.05). While between TSI and WBGT, a significant correlation was found in terms of the “skin temperature” of workers. Mohammadian et al. [34] found a significant correlation between “WBGT and the physiological parameters of Tcr and HR (r = 0.317, P = 0.002; r = 0.434, P < 0.001, respectively)”. In terms of DI, only a “significant relationship” was found with HR “(r = 0.229, P = 0.03)”. However, a significant dissimilarity was found between “WBGT and the Threshold limit values (t = 4.903, P < 0.001)”. Golmohammad et al. [44] established a relationship between HSI and WBGT among bakery occupants and found significant findings (r = 0.509). In Iran, for the “petrochemical industry” a strong correlation was found between “WBGT and HR (0.731), systolic blood pressure (0.695) and diastolic blood pressure (0.375) and skin temperature (0.451)”, respectively [45]. While the most powerful relationship lived between “required sweat rate (SWreq) and deep body temperature (0.766)” [45]. Similarly, Monazzam et al. [46] performed a study among Petrochemical Industry workers in Iran. In this research, authors established a relationship between physiological parameters viz “HR, systolic and diastolic blood pressure and deep and skin temperatures” and environmental parameter’s viz DI, WBGT, SWrEquation The analysis results indicated that the “highest correlation was found between WBGT and DI index” vs HR “(0.731, 0.725)”, correspondingly. While in the case of SWreq and “deep body temperature,” the highest strong relationship (0.766) was found under a heat stress scenario [46]. Anyiam [47] also argued that working in high temperatures has harmful effects on the health of bakery/kitchen workers, including symptoms associated with heat stress. Accordingly, the greatest significance was found in heart rate, which was related to the “modified physiologically equivalent temperature (0.7773)”, PMV (0.7624), and “perceived heat stress (0.6479)” indices in hot environments [48]. Correspondingly, among Sudanese industrial workers, there was the highest significant relationship (0.690) between heat stroke and WBGT [49].

Hence, the study’s significant findings directed that physiological parameters change under different work environmental conditions. Present study findings also support the previous research outcomes regarding the “relationship between heat stress indices and physiological parameters”.

4.1. Study limitations and further research possibility

The present study assessed the relationship between “heat stress indices”, “physiological parameters”, and “clothing wear”. A few limitations were in this study, such as (i) only the IR pantry car kitchen area was focused; (ii) due to security issue only heart rate was consider for physiological parameters; (iii) physical measurement was taken at specific cooking periods such as morning, day, evening and night not over the entire cooking periods; (iv) Only the chefs’ perspective, a heat stress analysis, and associated dominant elements were addressed in this study. However other factors such as posture prediction, weight lifting, and musculoskeletal pain index, were not targeted; these factors should be considered while designing the “tools” and “workstation” from the ergonomics point of view. Mechanical factors such as vibration and jerk are not taken into account in this investigation. Possible future works could be done like analysing IR pantry car indoor work condition using the subject’s perception with thermal and physiological parameters (“skin temperature, blood pressure, blood oxygen saturation, and various electrophysiological signals”).

5. Conclusions

Working situations in the kitchen environment are callous; the IR pantry car is also one of them. Due to the sedentary physical activity of employees, conventional actions should be carried out to minimize the risk. Therefore, the present study was focused on assessing the thermal environment of the IR pantry using heat-stress indices and heart rate variables. During analysis, the average, “maximum”, and “minimum” values of “thermal indices” (UTCI, WBGT, DI, TSI, HI) showed a complex work environment for culinarians. The strongest correlation was found in all heat stress indices except the association UTCI and HI. Also, no significant correlation has been seen between heat stress vs. physiological and clothing parameters. The present study supported the previous research results, which showed no significant correlation between thermal and physiological parameters. Due to thermal adaptation, workers’ physiological concerns may differ, and they may be accustomed to working in a hot environment.

Footnotes

Acknowledgments

We are grateful to the chefs of the railway pantry kitchens who were willing to participate in this study.

Ethical approval

Punjab Engineering College, Chandigarh, approved the study protocol [Reference number: PEC/PED/38A].

Informed consent

Informed consent was requested from all the study participants.

Conflict of interest

All authors have no conflict of interest to report.

Funding

Not applicable.

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