Safety and health risks for workers exposed to cold thermal environments: A frozen food processing industry perspective

Abstract

BACKGROUND:

Environmental temperatures in the fresh food industry vary from 0°C to 10°C, and go below -20°C for the frozen food industry, representing risk for the health and safety of workers involved.

OBJECTIVE:

The aim of this work was to evaluate the cold thermal stress risks for workers working in a frozen food industry.

METHODS:

A total of 27 acclimatized workers (13 male and 14 female) participated in a study which was conducted during 11 working days. The thermal sensation questionnaire and the cold work health questionnaire (CWHQ) were applied to all participants. Additionally, 4 workers were chosen to be fully monitored with a thermometer telemetry capsule for measuring the intra-abdominal temperature and 8 skin temperature sensors.

RESULTS:

The lowest recorded hand temperature was 14.09°C, lowest forehead 18.55°C, mean skin temperature had variations of 1.10 to 3.20°C along the working period. Highest and most frequent fluctuations were found in the hand and forehead skin temperatures, small changes were found in mean skin temperature.

CONCLUSIONS:

Answers to the CWHQ increase concern on clinical forms of “a frigore”, and in two cases the mean body temperature decreased below 35.0°C, which is defined in the current literature as a mild form of hypothermia.

Keywords

Cold exposure thermoregulation core temperature thermal sensation cold work health questionnaire

1 Introduction

The structure of the labour market in the food industry is constantly undergoing change, with consumers purchasing less fresh and more frozen and chilled foods [1, 2]. Even more, the trend show that the frozen food industry will continue to grow due to the quality and safety of frozen food, and due to the extended storage life, control the dietary portion and reducing waste, offering the possibility to preserve and use seasonal foods all year round [3].

In the fresh food industry the working activities are conducted in environmental temperatures from 0°C to 10°C, while in the frozen food industry at temperatures below –20°C, varying from –5°C to –30°C depending on the practical storage life and type of food to be frozen [4].

In indoor environments, the climate conditions are constant and predictable, which facilitates the application of risk management measures. In addition to individual factors for adapting to cold (such as body fat content level of physical fitness, gender, age, diet and ethnicity), adaptation to cold-exposure in indoor environments could be successfully organized through the application of cold disturbances such as shelter, clothes, heat sources and time sharing.

When the human body is exposed to cold, vasoconstriction occurs, reducing blood flow to the peripheral areas of the body, in an attempt to conserve heat and maintain organ functions. If the heat loss is severe, the brain sends signals to the muscles, generating heat through producing tremors caused by compulsively contracting the muscles [5].

The adverse effects of exposure to moderate and severe cold thermal environment were evidenced through different studies. Studies conducted in a frozen food industry concluded that the health of the workers frequently exposed to cold should be monitored on regular basis, as they tend to relate more pain in the musculoskeletal system, disturbance throughout the body, respiratory symptoms and episodic finger symptoms [6]. Further-on, the order-picking work in the cold leads to complaints in the upper part of the body [7], which can further lead to work accidents [8], or with prolonged and chronic hyperpnoea with cold dry air, leading to the development of respiratory symptoms [9].

This information are further-on important as the newest data estimate that in the USA alone, there are around 93 thousands people employed in the Frozen Food Production industry, where most of them participate in the production, and therefore daily exposed to cold thermal environment [10].

The aim of this work was to evaluate cold thermal stress risks for workers working in a frozen food industry, considering both moderate and severe cold thermal environment exposure.

2 Methodology

2.1 General data

The study is originally part of a doctoral thesis [11].

The experiments were conducted in the cold packing sector of a frozen food processing factory located in Rio Grande do Norte, a tropical region located in Brazil. The study included all workers from the studied cold packing sector. In total, 27 acclimatized workers participated in the study, 13 male (mean age±sd 25.20±5.43 years) and 14 female (mean age 34.40±5.00 years). As the industrial working activities are dynamic, some workers moved from the cold packing sector to another sector, which influenced the number of participants in each questionnaire. Twenty-three of them fulfilled the thermal sensation questionnaire, while twenty fulfilled the cold work health questionnaire.

Only four workers were exposed to severe cold thermal environment, which were therefore selected to be fully monitored with various equipment. All the applied documents were translated into Brazilian Portuguese. The experiment was approved by the Ethics Committee of the of the University of Porto, approval number: 06/CEUP/2015.

All workers usually conduct similar working tasks each day, spending most of their time in moderate cold thermal environment. Female workers conducting low physical repetitive work in a standing position (packing fish and crustaceans into 400 grams packages), and male workers conducting moderate to heavy physical work (packing 400 grams packages into 20 kg packages, check the stored material, organize materials on pallets, separate materials from pallets, move pallets and heavy loads with forklifts, once a week breaking the ice on the floors in the severe cold chambers and do heavy liftings). The only male with low intensity work was the leader of logistics (volunteer number 1), which was the connection between offices and the stock, giving directions on working tasks, organizing and supervising the packing activity. Although he didn’t conduct heavy work, his task included higher exposure to severe cold, as he would often enter to verify or count the products in the stock. Other fully monitored workers were male packing operators, spending most of their time in moderate cold (below 18°C, measured by a thermometer placed at 7 meters height), and several times per day storing frozen packages in the severe cold chambers (with temperature of –25°C).

2.2 Thermal sensation questionnaire (TSQ)

The Thermal sensation questionnaire (based on the Annex B of the ISO 10551:199 [12]) was answered in total 100 times by 23 workers. It was conducted during three working days on 19/01/2016, 21/01/2016 and 26/01/2016 for workers from the cold packing sector. The answers were collected 4 times a day: around 08:00, at the beginning of the morning working period (fulfilled 34 times); around 12:00, at the end of the morning working period (fulfilled 13 times); around 13:30, at the beginning of the afternoon working period (fulfilled 25 times); and around 16:30, at the end of the afternoon working period (fulfilled 28 times). The number of questionnaires fulfilled on each day and part of the day varied, depending on the number of workers present at that time in the cold packing sector.

2.3 Cold work health questionnaire (CWHQ)

The Cold work health questionnaire (based on the Annex D of the ISO 15743:2008 [13]) was answered in total by 20 workers, one time by 10 male (mean age 25.7±6.04 years) and 10 female (mean age 34.2±4.91 years) workers from the cold packing sector. It was conducted during the same three working days as the TSQ. The questionnaire gives an overview of the workers self-evaluation on his/her cold sensitivity, cold urticaria, respiratory symptoms, cardiovascular symptoms, symptoms related to peripheral circulatory disturbances, symptoms related to white fingers, symptoms related to musculoskeletal system, local cold injuries and the effect of cold on performance.

2.4 Fully monitored workers

Four workers from the cold packing sector were chosen to be fully monitored during their working activities. Three of them were screened during 3 working days, while one during 2 working days. In total, a sample of 11 working periods was achieved. The mean age±sd of the fully monitored workers was 29.00±6.32 years old, mean body height was 167.40±5.40 cm, mean weight during all 11 measuring days was 79.70±17.9 kg, mean body mass index (BMI) was 28.41±6.28 kg/m². In the Table 1 are illustrated physical characteristics and lifestyle data from 4 fully monitored workers.

Table 1
Detailed physical characteristics and lifestyle data from fully monitored workers

Volunteer Age (years) Height (cm) Weight (kg) BMI (kg/m²) Coffee^* Last meal Ate for the last meal^* Medications taking Went to sleep and woke up Sleeping hours Working period

V1 21 161.0 88.60 34.20 NO 20:00 Sandwich NO 23:00 –06:00 7 h 44 h/d

6 d/w

17 m

89.00 34.30 21:00 Cuscuz^ 22:30–06:30 8 h 44 h/d

92.40 35.60 19:30 Cuscuz^, bread, egg 22:30–06:40 8 h 10’ 6 d/w

V2 27 174.0 100.20 33.10 YES 06:30 Chicken, bread, milk NO 21:00–05:00 8 h 8 m

101.20 33.40 YES 06:30 Bean soup NO 21:40–05:30 7 h 50’ 44 h/d

98.00 32.40 NO 06:00 Milk with oatmeal Headache pill 22:00–05:40 7 h 40’ 6 d/w

V3 33 166.1 60.70 22.00 YES 06:30 Sandwich NO 22:30–05:30 7 h 20 m

61.30 22.20 06:20 Egg, bread 22:30–05:20 6 h 50’ 44 h/d

NA NA 6 d/w

V4 35 168.5 61.75 21.70 NO 06:20 Cuscuz^, milk NO 00:00–06:00 6h 16 m

62.20 21.90 Cuscuz^, milk, egg 23:00–06:00 7 h

61.60 21.70 Cuscuz^**, sausage, milk 23:30–06:00 6 h 30’

Mean±SD 29±6.3 167±5.4.4 77.81±19.74 27.75±6.82 15.2±5.12 months

78.42±19.89 27.95±6.82

84.00±19.60 29.90±7.28

Volunteer	Age (years)	Height (cm)	Weight (kg)	BMI (kg/m²)	Coffee^*	Last meal	Ate for the last meal^*	Medications taking	Went to sleep and woke up	Sleeping hours	Working period
V1	21	161.0	88.60	34.20	NO	20:00	Sandwich	NO	23:00 –06:00	7 h	44 h/d
											6 d/w
											17 m
			89.00	34.30		21:00	Cuscuz^**		22:30–06:30	8 h	44 h/d
			92.40	35.60		19:30	Cuscuz^**, bread, egg		22:30–06:40	8 h 10’	6 d/w
V2	27	174.0	100.20	33.10	YES	06:30	Chicken, bread, milk	NO	21:00–05:00	8 h	8 m
			101.20	33.40	YES	06:30	Bean soup	NO	21:40–05:30	7 h 50’	44 h/d
			98.00	32.40	NO	06:00	Milk with oatmeal	Headache pill	22:00–05:40	7 h 40’	6 d/w
V3	33	166.1	60.70	22.00	YES	06:30	Sandwich	NO	22:30–05:30	7 h	20 m
			61.30	22.20		06:20	Egg, bread		22:30–05:20	6 h 50’	44 h/d
			NA	NA							6 d/w
V4	35	168.5	61.75	21.70	NO	06:20	Cuscuz^**, milk	NO	00:00–06:00	6h	16 m
			62.20	21.90			Cuscuz^**, milk, egg		23:00–06:00	7 h
			61.60	21.70			Cuscuz^**, sausage, milk		23:30–06:00	6 h 30’
Mean±SD	29±6.3	167±5.4.4	77.81±19.74	27.75±6.82							15.2±5.12 months
	78.42±19.89	27.95±6.82
	84.00±19.60	29.90±7.28

^*In the past 12 hours; ^**cuscus is a plain, steamed, cake-like cereal made with yellow, precooked corn meal.

The medical examination was conducted by the industrial medical doctor. All subjects were informed about the goals and risks of the experiments and signed the informed consent prior to participating. The subjects were examined and asked to, prior to participating in the trial, to drink the usual amount of coffee, tea, to avoid drinking alcohol for at least 12 h before the test; not to eat spicy food at least 12 h before the test; sleep normally before the test (about 8 h); not conduct greater physical exertion than it is usual at least 1day before the test. All the subjects were non-smokers, didn’t drink tea, alcohol, eat spicy food, were right- handed and had a usual physical exertion the day before the trial was conducted. Every day before the trial, it was recorded what they ate in their previous meal, what time they ate, if they took some medicines, the time when they went to sleep and when they woke up, as well the number of hours they slept. All subjects had the same working period of 8 hours, the morning part from 07:30 till 11:30, the pause of 1 hour, and finally the afternoon part from 12:30 till 16:30 (working hours varying depending on the process situation). Daily exposure to SCE varied among workers depending on the activity from 1 to 31 minutes, with a maximal encountered interrupted exposure of 8 minutes.

The experiments were conducted during a normal working day, with the subjects performing the usual tasks being exposed to severe cold as usual and over the usual time period. The experiments were conducted with the usual industrial work of 8 hours at 16 to 18°C and entering for several times to the frozen food chamber at air temperature of –25°C. Skin temperature (Tskin) was measured with bioplux skin temperature sensors. The sensors were put according to ISO 9886:2004 [14] on 8 measuring points: forehead (Sk8), right arm in upper location (Sk7), right scapula (Sk6), left upper chest (Sk5), left arm in lower location (Sk4), left hand (Sk3), right anterior thigh (Sk2) and left calf (Sk1).

As it was concluded through a revision of previously conducted studies [15], that the assessment of thermal strain in cold thermal environment should be measured through oesophageal or intra-abdominal temperature, the core body temperature was measured by using the Equivital Ingestible Pill Sensor (thermometer telemetry capsule) with dimensions of 8.7 mm by diameter and 23 mm by length. It was swallowed with water for at least 5 hours before each test (usually before going to sleep); travelled along the digestive tract harmlessly, and leaving naturally within 24 to 72 hours. The sensors began to transmit one minute after the capsule activation by the external monitor, sending details every 15 seconds to the EQ02 Life Monitor –Electronics Sensor Module (SEM), which transmits the data via Bluetooth. The SEM was transported in a belt, recording the data from core body temperature, chest skin temperature, heart rate, respiratory frequency and accelerometry (Acc). For the fully monitored workers, a codification was used for each volunteer “V01-D3-1”, where “V01” stands for volunteer number 1 (to each volunteer was given a code name), “D3” stands for the trial day of that specific volunteer, and the last number “1” stands for morning, while “2” for afternoon part of the trial.

2.5 Clothing

While working, the subjects wore their usual clothing, including socks, underpants, t-shirt and trousers, and above-it the jacket with a hood, trousers, boots, as part of the cold protective clothing. It was noticed that some subjects put their feet in plastic bags before wearing the boots.

2.6 Data analysis

The data of core body temperature and accelerometry were analyzed by using the programs Equivital Manager and EqView professional. The skin body temperature was recorded by using the MonitorPlux program, later on to be processed by using a Matlab 2014b software program. When the Tcore recorded value was –1°C in the gathered data, it was considered as outlier and therefore excluded from the graphics. The mean skin temperature was calculated using the weighting coefficients as suggested by ISO 9886:2004 [14]. Statistical analysis were done by using the excel statistical toolbox.

3 Results

The results of the TSQ are illustrated in the Table 2. For the purpose of this study, 19 questionnaires from 19 workers were selected (9 males and 10 females), showing answers 3 times a day: at the beginning of the morning working period, at the beginning of the afternoon working period and at the end of the afternoon working period with a total of 57 questionnaires. Other questionnaires were excluded as the answers were gathered only in some day periods or the answers were from different day periods and different days. The answers 4 and 5 were excluded from this study as they seemed to be biased.

Table 2
Thermal Sensation Questionnaire results

Question 1. How do you feel at this precise moment: I am. . .(1) 2. How do you find this? (2) 3. At this moment, would you prefer to be? (3)

Day period 1 3 4 1 3 4 1 3 4

Male Mean –2.22 –0.56 –1.33 –1.22 –0.33 –0.89 0.33 –0.11 –0.11

volunteers ±sd 1.64 2.51 2.12 0.83 0.50 1.27 0.71 1.05 1.27

Female Mean –2.20 –2.30 –2.10 –0.70 –0.50 –0.50 0.40 0.10 0.70

volunteers ±sd 1.14 1.42 0.99 0.82 0.71 0.71 0.70 1.10 1.06

	Question	1. How do you feel at this precise moment: I am. . .(1)	2. How do you find this? (2)	3. At this moment, would you prefer to be? (3)
	Day period	1	3	4	1	3	4	1	3	4
Male	Mean	–2.22	–0.56	–1.33	–1.22	–0.33	–0.89	0.33	–0.11	–0.11
volunteers	±sd	1.64	2.51	2.12	0.83	0.50	1.27	0.71	1.05	1.27
Female	Mean	–2.20	–2.30	–2.10	–0.70	–0.50	–0.50	0.40	0.10	0.70
volunteers	±sd	1.14	1.42	0.99	0.82	0.71	0.71	0.70	1.10	1.06

⁽¹⁾ Scale from –4 to +4: –4 (very cold), –3 (cold), –2 (cool), –1 (slightly cool), 0 (neutral), +1 (slightly warm), +2 (warm), +3 (hot), +4 (very hot); ⁽²⁾ Scale from –4 to 0: –4 (extremely uncomfortable), –3 (very uncomfortable), –2 (uncomfortable), –1 (slightly uncomfortable, 0 (comfortable); ⁽³⁾ Scale from –3 to +3: –3 (much cooler), –2 (cooler), –1 (slightly cooler), 0 (neutral/without change), +1 (slightly warmer), +2 (warmer), +3 (much warmer).

The results of the first question from the CWHQ are illustrated in the Fig. 1 for male and Fig. 2 for female workers, showing on the left figure the answers from male and on the right from female workers.

Fig. 1

Results for male workers on the question 1 “How do you generally feel in cold?” with answers regarding a) Whole body, b) Fingers, c) Toes.

Fig. 2

Results for female workers on the question 1 “How do you generally feel in cold?” with answers regarding a) Whole body, b) Fingers, c) Toes.

In Table 3 are presented the mean as well the minimum and maximum value of some of the main collected data of skin and core temperature. From this data can be highlighted the values bellow 35°C for mean body temperature. The results of all volunteers show great variation in core temperature along the working day. In the Figs. 3 4 are as example the data from volunteer 3 in which Fig. 3 shows morning Acc and Tcore and Fig. 4 shows afternoon Acc and Tcore. Periods within the severe cold chamber are marked by vertical shaded areas. As an example of core and skin temperatures, results from two volunteers are illustrated in the Figs. 5 6 represent the data of volunteer 1.

Table 3

Mean, minimal and maximal temperatures

		Left hand	Forehead	Core temperature	Mean skin temperature	Mean body temperature
V01_D3_1 temp. (°C)	mean±SD	23.09±1.56	29.57±1.05	37.31±0.04	30.13±0.27	35.15±0.08
	min	18.33	26.05	37.24	29.41	34.98
	max	26.57	30.74	37.41	30.54	35.29
V02_D2_1 temp. (°C)	mean±SD	26.71±3.77	29.56±2.98	37.59±0.11	31.14±1.28	35.65±0.44
	min	14.46	18.55	37.44	29.08	34.94
	max	32.80	35.01	37.81	34.22	36.59

Fig. 3

Results for the volunteer 3 on day 2 morning, selected part of the graph, total accelerometry and core temperature.

Fig. 4

Results for the volunteer 3 on day 2 afternoon, selected part of the graph, total accelerometry and core temperature.

Fig. 5

Results for the volunteer 1 on day 1 morning, left hand (Sk_3), Tcore and Tskin (1-working on a computer, 2-touching the cold package, 3-walking, counting, standing).

Fig. 6

Results for the volunteer 1 on day 1 afternoon, left hand (Sk_3), Tcore and Tskin.

On the left side axis in Figs. 5 6 are illustrated values for the hand and mean skin temperature and in Figs. 3 4 accelerometry values, while on the right-side axis in all (3 to 6) figures are illustrated the core temperature values.

4 Discussion

4.1 Thermal sensation questionnaire (TSQ)

Although it seems that at the start of the afternoon working period male workers feel less cold compared with the end of the afternoon working period, the gathered data don’t seem to be in accordance with any of the other gathered data. The data seem not to be consistent enough to make further conclusions. An example is the females answer to question 1 where the answers are similar even with longer exposure to moderate cold.

4.2 Cold work health questionnaire (CWHQ)

As the industry is located in north-eastern Brazil, with constant high outdoor air temperatures throughout the year, and the work is done at constant low indoor air temperatures in the cold packing sector, there is a risk of “a frigore”, the diseases favoured by low temperature conditions, sudden changes of temperature change from hot to cold, high humidity and air currents. Some answers to the CWHQ might be related to the clinical forms of “a frigore”:

Fifteen reported respiratory symptoms –the respiratory system which may occur in rhinitis, pharyngitis, laryngitis, bronchitis, bronchopneumopathies and pneumonias;

Five reported cardiovascular symptoms, 12 reported symptoms related to peripheral circulatory disturbances and 24 reported symptoms related to white fingers –the cardiovascular system are favoured the obliterate endarteritis, coronary heart disease and hypertension;

Fifteen reported symptoms related to musculoskeletal system –the musculoskeletal system in which may occur rheumatic fever, arthritis and lombosciatics;

Renal diseases may also occur –glomerulonephritis and neurological –neuritis and neuralgia [16, 17].

According to ISO 15743:2008 [13], due to the answers of the workers, detailed interviews should be conducted on cold sensitivity, cold urticaria, respiratory function, cardiovascular function, peripheral circulatory disturbances, Raynaud phenomenon, musculoskeletal symptoms and performance. The type of detailed interview should depend on answers of each worker individually.

In the Fig. 1 in all answers (whole body, fingers and toes) male workers show higher intensity of discomfort (feeling more uncomfortable) compared to females in Fig. 2, which could be explained with higher exposure of males to severe cold thermal environment; therefore it is reasonable to see more complains in the male population on the influence of cold on their health. Although answers from female workers show that the whole body thermal sensation (with 50%feeling slightly uncomfortable and 50%feeling pleasant) and the fingers thermal sensation (10%feeling unpleasant, 50%slightly uncomfortable and 40%feeling pleasant) show high satisfactory rate, their answers on the thermal sensation of toes show higher intensity of discomfort (10%feeling very unpleasant, 30%feeling unpleasant, 60%feeling slightly unpleasant and no one feeling pleasant). It could be explained with their standing packing activity which involves low legs activity with their long exposure to moderate cold and occasional exposure to severe cold (when the doors of the severe cold chambers open). More complains were found in female workers on questions regarding headache named migraine, increased excretion of mucus from the lungs, very profound rhinitis, for the colour of fingers to episodically change into white, and back or hip pain, which could be explained with their type of work (packing fish and crustaceans into packages using plastic gloves for hygienic reasons, but not having gloves for cold protection, and standing during all working period).

These findings related on feeling cold hands is in accordance with previous studies [18, 19] conducted with workers handling refrigerated products in moderate cold thermal environment.

Although prolonged localized cold exposure can result in localized habituation of vasoconstrictor responses [20], the decrease of the temperature of the hands and fingers might cause discomfort, pain, decreased performance, functional imbalance and cold-related diseases [21].

In order to prevent cold stress symptoms, there is a need to optimize work inside cold stores by considering adequate work-rest periods.

4.3 Fully monitored workers

The indoor thermal conditions in the cold packing section correspond to moderate cold, with air temperature between 16 and 18°C, while in the frozen food chamber was below –25 °C.

As it was found by previous studies, exposure to such temperature variations might result with AMI and stroke [22], therefore it is important to control workers on regular basis in order to be able to manage and reduce the risk for workers [17]. In the Figs. 7 , 8 and 9 are illustrated working activities conducted by the fully monitored workers consisting of pushing 5 pots of ≈20 kg each and packing activities.

Fig. 7

Volunteer 2, pushing 5 pots of ≈20 kg each from the frozen food chamber to moderate cold packing sector.

Fig. 8

Volunteer 4, female workers packing packages of 400 grams, and male workers packing into bigger boxes 10 kg inside the moderate cold sector.

Fig. 9

Volunteer 3, picking frozen packages of 400 grams from the frozen food chamber and then packing them into bigger boxes 20 kg.

As illustrated in Fig. 5, around 07:50 am, the hand temperature of the volunteer 1 decreased to almost 18°C even when he was not exposed to severe cold thermal environment. In that case, the worker was measuring the temperature of the frozen food package, but without using cold protecting gloves. Such decrease in hand temperature can impair complex manual performance and interfere with the use of tools, thereby reducing work safety. This is in accordance with another study which was also conducted in artificially cold environments, where it was evidenced that the skin temperature of the fingertips decreased to 16.86°C [21].

The hand and forehead where found to have the highest and most frequent variations in skin temperature, which is reasonable as they were mostly not covered with the cold protective clothing. The lowest recorded forehead value was 18.60°C, while the average minimal value was 5.3±3.6°C lower than the maximal value. The lowest recorded hand value was 14.1°C, while the average minimal value was 10.4±4.9°C lower than the average maximal value. The hand skin temperature recovery was fast (±2 min from 18.6 to 28.0< °C), but when exposed to cold air or touching cold products or material it also decreased fast (±2 min from±28.0 to 18.0°C), making the changes of its temperature frequent, fast and with greater differences. This extremity thermoregulation depends on the muscle mass of the individual, and is beneficial to all of those carrying out manual tasks in cold environments [23]. Nevertheless, for long term exposures it is necessary to consider using cold protective gloves.

The mean skin temperature show some small and slow variations along the time, with a maximal variation between the minimal and maximal recorded value in one case of 5.1°C along all the measuring working period, and an average of between 1.1 to 3.2°C difference among the workers along all the measured working period. According to previous studies with repeated exposures of 30 min to –25°C, it was found that the mean skin temperature was lower for –2.3 to –2.8°C at the end of the trial compared with the baseline measurements [24].

The mean body temperature has no significant variations along the working period. As it is shown in the Table 3, on two occasions, for V01-D3-1 and V02-D2-1, the mean body temperature decreased slightly below 35°C (on the minimal measured values, 34.98°C and 34.94°C respectively). The current literature has described it as the start of the mild form of hypothermia (general freezing) which occurs when the body temperature decreases to 32.0–35.0°C, and appears with shivering, tachycardia, tachypnea and slowness of ideation and compensated dysarthria. On appearing of mentioned clinical features, the workers should start a rewarming process [17, 25]. Through the indicators of changes in the metabolic rate, rectal and skin temperature, previous studies concluded that it is possible to quantify the adaptation level. Including local cold adaptation of the extremities [26]. Cold exposure are necessary to increase the cold tolerance and prevention of cold injuries [27].

Previous studies [24, 28] conducted at –25°C concluded that with the exposure of 20 to 30 minutes there is a decline in rectal core temperature in resting, lighter and heavier work (from –0.6 to –1.1°C). In this study measuring intra-abdominal core temperature, the core temperature seem to raise in most of the cases with the exposure to severe cold (as illustrated in all figures), which could be explained by the vasoconstriction in the superficial layers of the body [29]. From Figs. 3 4 (showing total accelerometry), it was not found a clear correlation between the accelerometry variations and the variations in core temperature. Nevertheless, accelerometry always seem to increase with cold exposure (due to the type of activity which is conducted in severe cold chambers), which may also contribute to the increase in core temperature values. The core temperature variations were always less than 1°C difference between the minimum and maximum value, in the most of the cases between 37 and 38°C. Although according to ISO 9886, the core temperature in cold thermal environment should be always measured through oesophageal or intra-abdominal temperature, in order to be relevant for the assessment of thermal strain in cold thermal environment [14], only studies with rectal and tympanic temperatures were found. Although the time of exposure to cold and severe cold environmental conditions were different among the mentioned studies (from °C5.0°C to °C25.0°C), it was in general concluded that core temperature was decreasing in the studies where the working activity was sitting, order picking or loading, while in studies where the working activity was walking on a treadmill, the core temperature was increasing. As the core temperature in the “increasing core temperature articles” was measured rectally, the explanation might be found in the production of heat from the local muscles, for which are is directly affected, and therefore it is higher when the work is performed with the legs than when it is carried out exclusively with arms [14]. By several included articles it was concluded that the rectal temperature was highest when the working activity was heavier [30 –32]. A recent study [33] conducted in a controlled laboratory environment on 11 male volunteers, using intra-abdominal ingestible pill sensor, evaluating variations in core temperature while exposed to severe cold (–20°C), found that the core temperature increased in all cases despite exposure to severe cold thermal environment due to moderate physical exertion.

Thus, given the results obtained in the present study and the results of previous studies by other authors, it can be concluded that more studies should be conducted on the influence of severe cold on core and skin temperature variations, taking into account both genders, with more time of exposure to severe cold. Studies should be also conducted on the variations of core and skin temperature in moderate cold. In activities as the standing packing, which in this study is conducted only by female workers, there are a particular interest on fingers and toes, which were found to have more complains.

5 Limitations

Challenges were found in gathering answers on questionnaires, as the working procedure is very flexible and workers change their working environment depending on the need of the working process.

This work was limited with the working process and industrial conditions. The main limitations of this study are therefore related to the generalizability of the results, which was not possible due to the limited number of workers present in the industrial process.

6 Conclusions

Cold work involves several adverse health effects, pose a risk for cardiovascular diseases and musculoskeletal complains and symptoms. Answers to the CWHQ increase concern on clinical forms of “a frigore”, which could be expected due to high differences between outdoor and indoor temperatures. Detailed interviews should be conducted on cold sensitivity, cold urticaria, respiratory function, cardiovascular function, peripheral circulatory disturbances, Raynaud phenomenon, musculoskeletal symptoms and performance. The hand and forehead had highest and most frequent variations of skin temperature. The mean skin temperature showed some small and slow variations along the time. The mean body temperature showed no significant variations along the working period, but in two cases decreased slightly below 35.0°C which in the current literature has been described as the start of the mild form of hypothermia (general freezing). The core temperature variations were always less than 1.0°C difference between the minimal and maximal value, in most of the cases between 37.0 and 38.0°C. The core temperature was found to increase when the subject was exposed to severe cold. This occurrence may be justified by vasoconstriction and higher physical exertion. However, as workers only went to the freezing chamber to do some activity, and with an intensity higher than that performed outside the chamber, as can be proved by the collected values of accelerometry, it can be concluded that the physical exertion also had a contribution to the increase in core temperature.

Future studies should be conducted considering with a higher number of volunteers, greater exposure time and with different severe cold thermal environment conditions. A future perspective is to compare and discuss the results of the applied questionnaires (thermal sensation questionnaire and the cold work health questionnaires) while considering the years of work in the sector.

Conflict of interest

None to report.

Footnotes

The supplementary files appendix are available from .

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