Identification and validation of risk factors in cold work

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DOCTORA L T H E S I S DOCTORA L T H E S I S

Luleå University of Technology

Department of Human Work Sciences • Division of Industrial Production Environment

:|: -|: - -- ⁄ -- 

:

Identification and validation of risk factors in cold work

Lina Giedraitytė

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G G G G G G G G

Identification and validation of risk factors in cold work

by

Lina Giedraityt ŝ

August, 2005

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– Utititi, šalta, – Skundžiasi ruduo:

– Kas pasiƈs man paltĈ, Kas kepurč duos?

Kojos jau sušlapo, Permerkŝ lietus.

Kas iš klevo lapo Man pasiƈs batus?...

Ištrauka iš Justino MarcinkeviĀiaus

„R udens skundas”

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Preface

The work for this Doctoral thesis was carried out at the Division of Industrial Working Environment, Department of Human Work Sciences, Luleå University of Technology.

Financial support has been generously provided by Luleå University of Technology, the European Regional Development Fund (Barents Interreg IIA Program) and the Swedish Institute.

The primary tutor has been professor Ingvar Holmér from the Thermal Environment Laboratory, Department of Design Sciences, Lund Technical University with tutor assistance provided by professor Jan Johansson and associate professor Bo Johansson. Professors Houshang Shahnavaz and John Abeysekera not only introduced me to the field of ergonomics, but also encouraged me for the more advanced studies in the field.

I would also like to express my gratitude to research engineers Tanja Risikko and Anita Hicks, educational trainer Liisa Hänninen and trainer Maire Huurre from the Cold Work Action Program of the Finnish Institute of Occupational Health, Oulu, Finland for conducting the studies involving Finnish observers. Director Arvid Påsche and senior engineer Bård Holand from Thelma AS, Trondheim, Norway are also due my thanks for their contributions to the studies with Norwegian observers.

I am also grateful to all co-authors of the articles included in this thesis along with the subjects who made it possible.

I would like to thank all of the employees at the Department of Human Work Sciences for making Arbetsvetenskap a nice place to belong.

Thanks to all my friends scattered all over the world. Special thanks to the ones here in Sweden who shared with me the dark and cold winters.

Finally, my unadulterated gratitude goes to Dr. Andrew Bérubé for being a benevolent native English speaker (for all that it implies to live among non-native speakers), for eloquently putting my research into the perspective of geophysics and for simply being my better half, often a less devilish one.

Nuoširdus dơkui keliauja ir Ƴ Lietuvą. Nors ir atsidǌrĊs šio ilgo sąrašo gale, jis tikrai ne mažiau svarbus, nes skirtas visiems tiems, kurie kiekvieną kartą nekantriai laukia manĊs sugrƳžtanþios – ypaþ tơþiui, mamai ir broliui Arǌnui. Kas iš manĊs ir beliktǐ be jǌsǐ visǐ ir gimtǐjǐ namǐ šilumos!

August, 2005 Luleå

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Abstract

There are very few methods available for the assessment of cold exposure and they rely more or less on complex equations for calculating heat balance; therefore, there is a need for new practical methods for the identification and control of cold hazards in workplaces.

In the first study, the aim was to test a checklist which enables cold risk assessment based on observations in the workplace. The checklist has seven main sections of cold related risk factors: ‘cold air’, ‘wind/air movements’, ‘contact with cold surfaces’, ‘exposure to water/

liquids/moisture’, ‘protective clothing against cold’, ‘protection of hands/feet/head from cold’

and ‘the use of personal protective equipment’. A total of 82 evaluation sheets were obtained from the field testing (24 from Sweden and 58 from Finland). The subjects found the observational checklist to be a usable tool for cold risk assessment in terms of the time needed to perform the risk assessment procedure, the interference of the method with the observed work, the adequacy of the instructions and the facility of the checklist.

In the second study, the aim was to test a checklist in workplaces in a country representing a different approach to safety culture than the one prevailing in Scandinavian countries. The secondary objective was to test whether there was a learning effect reflected in the results recorded in the evaluation sheets filled in after conducting cold risk assessment procedure for the first, the second and the third time. A total of 277 evaluation sheets were obtained from 116 observers from the two sawmills in north-western Russia. The observers, similarly to the ones in Finland and Sweden, found the observational checklist to be a usable tool for cold risk assessment in terms of the time needed to perform the risk assessment procedure; the instructions provided to the checklist and to the summary table; the facility of the checklist and of the summary table and the suitability of the checklist (in regards to the structure and the content) to identify the cold-related risk factors. According to the Nordic observers, a workers’

representative responsible for industrial safety and workers themselves should carry out the assessment procedure at the workplace. On the contrary, the Russian observers mentioned workers only in 7.5% of the evaluation sheets giving priority to a safety engineer (mentioned in 50.5% of evaluation sheets) and a foreman (mentioned in 22.6% of evaluation sheets). No statistically significant effects of learning were found when three groups of answers (after the first, second and third time) from 73 observers were compared.

In the third study, the objective was to validate the checklist for the identification of cold- related problems under laboratory conditions in terms of whether the checklist generated results were in accordance with the subjects’ physiological measurements and self-reported observations of their thermal state. Eight male subjects were screwing bolts with both gloves and bare hands and stepping in 0°C, walking at 3.5 km/hour and 4.9 km/hour in –10°C and at 3 km/hour in –25°C and standing still at 4°C in the climatic chamber. In conclusion, the number of subjects who assessed the particular cold related risk factor by means of the checklist in conformity to their reported thermal sensations and measured skin temperatures varied most often from five to eight subjects. In some rare cases, only one, two or three subjects gave evaluations that were in agreement. In particular, this was the case for risk factors concerning the presence of light work and protection of extremities against cold, when several work tasks were performed under the same experiment.

In the fourth study, the aim was to identify cold-related risk factors that people face in their work environment and to investigate whether the region where the checklist was filled in, the type of work (indoor versus outdoor work), ambient temperatures and the sector that the company represented had any influence on the ratings that these factors received. Cold-related risk factors were assessed in 14 companies representing various work activities in

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construction, stevedoring and storage, tourism, sawmills, fish processing, forestry and road building industries in four countries: Finland, Norway, Sweden and north-western Russia. An observational checklist for the assessment of 13 cold-related risk factors was applied and 164 checklists were filled in by 80 selected observers in the Nordic countries and 277 checklists were completed by 116 selected observers in north-western Russia. The observers consisted of worksite managers, occupational health and safety (OH&S) representatives, occupational nurses and the workers themselves. The majority of the cold-related risk factors were rated differently by Nordic and Russian observers in term of either the chosen severity of the problem (‘no problem’, ‘slight problem’ or ‘considerable problem’) or the frequencies of ratings along these categories. Five factors (‘cold air’, ‘wind/ air movements’, ‘contact with cold surfaces’, ‘water/ liquids/ damp’ and ‘highly varying workload’) were most often rated as slightly problematic and two factors (‘protective clothing against cold’ and ‘light work’) as causing no problems by both groups. The remaining six factors (‘protection of extremities against cold’, ‘use of PPE’, ‘long-term cold exposure’, ‘varying thermal environments’,

‘slipperiness’ and ‘insufficient lighting’) were rated differently by Nordic and Russian observers, and the latter indicated less favourable situations at the observed workplaces. Only a few factors had different ratings if various variables (nature of work, ambient temperatures and sector of economic activities) were taken into account.

In the fifth study, the aim was to validate the Edholm scale and the ISO 8996 standard by comparing the metabolic rates estimated for both methods with the actual measured metabolic rate (MMeas) in six manual material handling tasks simulated under laboratory conditions. The metabolic rate was calculated from the oxygen consumption VO₂ (19 participants) according to Standard No. ISO 8996. Additionally, the subjects estimated perceived exertion using the Borg scale. The metabolic rates derived from the Edholm scale (MEdh) overestimated five of six activities by 34–50% (D=.05). The metabolic rates derived from ISO 8996 (MISO) overestimated all activities by 7–38% (D=.05).

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List of publications

This thesis is based on the following papers that can be found in the appendix II:

Paper I

Giedraitytơ, L., Mäkinen, T.M., Holmér, I., Hassi, J. (2005). The field testing of an observational checklist for the assessment of cold-related risk factors. International Journal of Circumpolar Health, manuscript accepted for publication.

Paper II

Giedraitytơ, L., Rybitski P.N., Loukianova, N. (2005). The usability of an observational checklist for the assessment of cold-related risk factors tested by Russian sawmill workers.

Submitted to International Journal of Industrial Ergonomics.

Paper III

Giedraitytơ, L., Holmér, I., Gao C., Kuklane K. (2005). Validation of the observational checklist for the assessment of cold-related risk factors under laboratory conditions.

Submitted to Applied Ergonomics.

Paper IV

Giedraitytơ, L., Mäkinen, T.M., Abeysekera, J., Holmér, I., Hassi, J. (2005). Observed cold- related risk factors for indoor and outdoor work in the Nordic countries and north-western Russia. Submitted to International Journal of Industrial Ergonomics.

Paper V

Giedraitytơ, L., Holmér, I., Gavhed, D. (2001). Validation of methods for determination of metabolic rate in the Edholm scale and ISO 8996. International Journal of Occupational Safety and Ergonomics, 7(2), 135–148.

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1. Introduction

1.1. Occupational exposure to cold

Many persons engaged in different occupations face cold exposure of varying duration and intensity. In Sweden, for example, 16.4 % of all employed people (about 4.2 million) in 2001 were exposed to cold work outdoors during winter months or a cold indoor climate for at least a quarter of their working time. If the statistics are divided by gender, 22.7% of all employed men and 9.5% of all employed women were exposed to cold environment at their workplaces for at least a quarter of their working time (Statistics Sweden, 2002). The percentages are somewhat higher than those of 1999, when 14.8 % of all employed persons (or 21.5% of men and 7.3 % of women) faced such working conditions (Statistics Sweden, 2000).

In Sweden, the occupational groups (according to the Swedish Standard Classification of Occupations, SSYK) most exposed to cold, are: skilled agricultural and fishery workers (60.6% of employed persons in this group are exposed to cold at least a quarter of the time);

craft and related trades workers (38.4%), especially subgroups such as building frame and related trades workers (67.0%) and building finishers and related trades workers (45.5%) falling under this category; and plant and machine operators and assemblers (29.1%), especially the subgroups of motor-vehicle drivers (53.4%) and agricultural and other mobile- plant operators (49.8%). In the remaining occupational groups the percentages of exposed workers vary from 2.0 to 25.2%, with certain subgroups having very high percentages such as child-care workers (40.6%), teaching associate professionals (30.5%) and stock clerks and storekeepers (29.0%) (Statistics Sweden, 2002).

In Finland, the weekly duration of exposure to cold at work was reported to be the largest (slightly over 20 hours) among construction workers, assemblers and repairers; higher than average (13 hours) exposure time was reported in farming, military and processing occupations (Hassi et al., 1998).

In the Nordic countries several questionnaire surveys have been carried out in which experience concerning the physical hazards of workplaces have been investigated. In these studies, it was found that 17–28 % of the employees experience draughts and 14–16 % experience coldness as a hazard in their work (Pekkarinen, 1994).

In 2001 in Sweden 0.7% of all employed men and 0.5% of all employed women had work related disorders during the previous twelve months (the time of the survey being a starting point) due to heat, cold or draught (Statistics Sweden, 2005). The percentage was somewhat higher (1.2–2.0%) for the subgroups with the highest share of exposed persons.

1.2. Human thermal balance and heat loss

The body generates heat continuously by converting food to energy and using the energy in the form of work. The majority of energy is converted to heat, which contributes to maintaining the body temperature. There must be an appropriate balance between the heat generated and the heat lost/gained from the environment. Whenever a temperature difference occurs between the body and its surroundings, heat transfer processes will occur to reduce this difference. The processes available, depending on the prevailing physical circumstances are heat loss or gain to a solid surface in contact with the body by conduction, heat loss or gain by convection and radiation due to cooler/warmer air and surroundings, and heat loss from the skin and respiratory tract due to evaporation of moisture (Youle, 1995).

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In cold weather, the only source of heat gain is the body’s own internal heat production, which increases with physical activity (Canadian Centre for Occupational Health and Safety, 1995). Hot drinks and food are also a source of heat.

The body loses heat to its surroundings in several different ways. Approximately 60% of heat loss occurs in the form of infrared heat rays or radiation (Herington & Morse, 1995).

Conduction accounts for only 2–3 % of the heat loss, although it may increase fivefold in wet clothing and 25-fold in cold water (Herington & Morse, 1995). In general, the higher the temperature difference between the body surface and cold objects, the faster the heat loss by conduction. Convection, or the movement of air currents, produces an average heat loss of 12%, although this amount can greatly increase with wind speed as the rate of loss depends on the air speed and the temperature difference between the skin and the surrounding air (Herington & Morse, 1995). Sweat production and its evaporation from the skin is also a cause of heat loss. This is important when performing hard work. Of the total heat loss of man, at least 20% is usually by evaporation of moisture, both from the skin surface (about two-thirds) and from the respiratory tract through evaporation of water from the lungs (about one-third) (Burton & Edholm, 1969). Small amounts of heat are lost when cold food and drink are consumed. Additional heat is lost during breathing by inhaling cold air.

1.3. Effects of cold exposure

Holmér (1994) has summarised the problems associated with occupational cold exposure:

thermal discomfort and pain sensation, in particular from the extremities; performance decrements due to cold hands, cold muscles or general cooling or due to hinders caused by protective clothing against cold such as weight, bulk, friction, etc; effects on human health such as cold injuries, initiation and aggravation of symptoms for cardio-respiratory diseases or elevated accident risks; and special requirements that arise from the above named factors for design and performance of work, for planning and design of workplaces and for design and use of equipment and tools.

Ramsey et al. (1983) found that ambient temperature had a statistically significant effect on the so called unsafe behaviour index (UBI). According to the authors, this relationship forms a U-shaped curve, with minimum UBI values occurring in the preferred temperature zone of 17 to 23ºC wet bulb globe temperature (WBGT). If the ambient temperature increases above or decreases below the preferred range, the proportion of unsafe behaviour increases.

1.3.1. Physiological responses to cold

Humans are warm-blooded animals; the body core temperature must normally be regulated to remain within a narrow range, typically 37.0±0.5°C, and the usual maximum deviation that can be tolerated by fit people (but with potential strain) is approximately ±2°C (Youle, 1995).

The hypothalamus, a part of the brain, has the main responsibility for body temperature in humans (Parsons, 1993). The hypothalamus accepts the information concerning the temperature status of the body, compares that information with a ‘set point’, and, if needed, initiates the body’s two main defences against cold, shivering and peripheral vasoconstriction (Evenson, 1994). Shivering, produced by involuntary muscle contraction, is the typical response to cold that cause an increase in the metabolic rate and hence the heat production of the body (Peterson, 1991). When the skin cools, blood flow is shunted from vessels which lie near to the surface to those deeper within the tissue, where heat is more easily conserved. This is done by reducing the diameter of the surface capillaries (vasoconstriction) through muscular action (Peterson, 1991). With continued cold exposure, cold-induced vasodilatation (an increase in the diameter of the deeper vessels) alternates with peripheral vasoconstriction

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to conserve core heat and, at the same time, intermittently save function in the extremities (Evenson, 1994). Cold stress can quickly overwhelm human thermoregulation with consequences ranging from impaired performance to death (Stocks et al., 2004).

1.3.2. Subjective responses to cold

Thermal sensation (discomfort and pain sensation) is related to how people feel and is therefore a sensory experience and a psychological phenomenon, thus it is not possible to define sensation in physical or physiological terms (Parsons, 1993). For example, cooling of the hand is very individually perceived (Hammarskjöld, Harms-Ringdahl & Ekholm, 1992).

However, most people feel comfortable when the air temperature ranges from 18°C to 22°C and the relative humidity is about 45% (Pathak & Charron, 1987).

Nerves in the skin can detect the sensation of cold as the nerves endings, some of which respond to warm stimuli and some to cold, are distributed across the skin (Evenson, 1994).

There are apparent anomalies whereby the skin can feel ‘cool’ at a temperature greater than that where the skin feels ‘warm’, because of the previous adapting temperature and rate of temperature exchange. This phenomenon is valid for small areas of the skin and also to the whole body sensation (Parsons, 1993).

Pain due to cold is related to vasoconstriction of blood vessels, but at low temperatures however, cold induced vasodilatation increases blood flow with an associated pleasant sensation (Parsons, 1993).

Although pain due to cold can be very intense, the physiological correlations are not so clear (Parsons, 1993). Havenith, Van de Linde & Heus (1992) have studied thermal and pain sensation associated with hand cooling in 12 subjects while they touched six different materials. They found that equal pain and thermal levels were associated with lower temperatures for the back of the hand than for the contact side: the slightly painful condition was associated with a skin temperature of 16^oC for the back and 19^oC for the palm of the hand. They have also reported that pain level appeared to be inversely related to cooling speed (Havenith, Van de Linde & Heus, 1992). However, another study (Chen, Nilsson & Holmér, 1994) investigating skin temperature changes and the subjective sensations of bare fingers touching a cold aluminium surface (in 25 subjects) reported that thermal and pain sensation lacked a good correlation with temperatures and temperature changes. Furthermore, it was found that both thermal and pain sensation strongly correlated to the skin temperatures on the hand and fingers under convective cooling, while no correlation was found under contact cooling (Chen & Holmér, 1998). Subjective judgements such as the decrease in finger pain and cold sensation during repeated finger cooling and the absence of them during post- immersion rest may not be reliable indicators for monitoring the risk of progressive tissue cooling and frostbite formation (Sawada, Araki & Yokoyama, 2000).

When feet were cooled, cold and pain sensations were connected with considerably lower temperatures in toes and heels (Kuklane, Geng & Holmér, 1998).

It has been reported that subjects immersed in cold water (+10^oC) were unable to reliably assess how cold they were (Hoffman & Pozos, 1989). The authors came to the conclusion that subjects who are rapidly cooled in water may have considerable difficulty separating feelings of cold from feelings of pain and discomfort.

1.3.3. Performance in cold

Cold exposure and the associated behavioural and physiological reactions have an impact on human performance, i.e. manual, muscular and aerobic performance, simple and choice

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reaction time, tracking, vigilance, cognitive tasks, etc (Holmér, Granberg & Dahlström, 1998). In a study of forklift workers who were entering cold stores very frequently for short periods of time, the reported cold stress and the decrease in workers' performance were the same as for continuous exposure to cold (Tochihara, 2005).

Manual performance is a combination of many kinds of ability that require, for instance, good tactile sensitivity, hand dexterity, force capability and motor co-ordination, and these skills are all influenced by hand cooling (Geng, Karlsson & Holmér, 2000). During cold exposure, manual performance is affected negatively and a significant increase in rapid erroneous responses is demonstrated (Enander, 1986). Various aspects of the effects of hand cooling on manual performance were investigated by many authors (Hammarskjöld, Harms-Ringdahl &

Ekholm, 1992; Giesbrecht, Wu, White, Johnston & Bristow, 1995; Tochihara, Ohnaka, Tuzuki & Nagai, 1995; Tochihara, Ohkubo, Uchiyama & Komine, 1995; Ozaki, Nagai &

Tochihara, 2001; Cheung, Montie, White, & Behm, 2003; Nowak, & Hermsdorfer, 2003; Jay

& Havenith, 2004).

Cold impairs the performance of complex mental tasks, while relatively simple tasks are unaffected (Enander, 1987; Thomas, Ahlers, House & Schrot, 1989; Giesbrecht, Arnett, Vela

& Bristow, 1993).

Cooling negatively affects all components of muscular performance: endurance, force, power, velocity and co-ordination (Oksa, Rintamäki & Mäkinen, 1991; Oksa, Rintamäki & Mäkinen, 1992; Oksa, Rintamäki & Mäkinen, 1993; Howard, Kraemer, Stanley, Armstrong & Maresh, 1994; Oksa, Rintamäki & Rissanen, 1997; Oksa, 2000.).

1.3.4. Health effects

Cold injuries occur as the result of man’s inability to properly protect himself from cold with subsequent lowering of the core body temperature (Holmér, Granberg & Dahlström, 1998).

Injuries from cold exposure are divided into two major types: non-freezing cold injuries (hypothermia, chilblains and trench/immersion foot) and freezing cold injuries (frostnip and frostbite).

Hypothermia, the lowering of core body temperature below 35°C, occurs when the body is unable to produce enough heat to replace heat lost to the environment (Evenson, 1994). As the core temperature continues to fall, the heart rate slows, breathing shallows, shivering diminishes and consciousness is lost at 32°C to 30°C (Wilkerson, 1986). The lowest known temperature for therapeutic survival of hypothermia is 9°C (Herington & Morse, 1995).

Chilblains is cold injury from repeated exposure of bare skin to wet, windy conditions at temperatures ranging from 15°C to near freezing and although uncomfortable, it causes little or no impairment (Wilkerson, 1986). Trench/immersion foot develops slowly over a period of hours to days from prolonged exposure of the lower extremities to cold (0°C to 10°C) and moisture (Burtan, 1994).

Frostbite, damage to tissue caused by overexposure to low temperatures usually involving the toes, nose, ears or fingers can cause injury ranging in severity from quite superficial but painful to frank necrosis (Peterson, 1991). Frostnip is a mild, reversible, superficial injury that involves no loss of tissue (Evenson, 1994).

Circulatory changes due to cold include a rise in cardiac output, an increased blood pressure and a higher peripheral vasoconstriction (Burton & Edholm, 1969). Cooling of the forehead and head elicits an acute elevation of systolic blood pressure and, eventually, elevated heart rate, however this reaction is of short duration and normal or slightly elevated values are regained after seconds or minutes (Holmér, Granberg & Dahlström, 1998).

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There is little evidence of cold injury of the respiratory tract due to cold (Parsons, 1993).

Inhalation of moderate volumes of cold dry air presents limited problems in healthy persons (Holmér, Granberg & Dahlström, 1998).

Snow, ice and reduced visibility increase the incidence of accidents in the cold. Snow blindness and sunburn may occur when the skin and eyes are unprotected from the ultraviolet rays of the sun and their reflection off the snow. The use of heaters and stoves increases the risk of fire, burns and carbon monoxide poisoning, particularly in confined spaces (Evenson, 1994).

The sensitivity and dexterity of fingers lessen in cold. At lower temperatures, cold effects deeper muscles, resulting in reduced muscular strength and stiffened joints. Mental alertness is reduced due to cold-related discomfort. For all these reasons accidents are more likely to occur in very cold working conditions (Pathak & Charron, 1987).

The use of protective clothing against cold is sometimes compromised, even when this has detrimental effects on one’s health. Manual tasks in cold are often done with bare hands or wearing thin gloves (Risikko & Anttonen, 1998), as the use of thick protective gloves against cold can impair manual functions such as hand dexterity or precision. Protective clothing against cold cannot always provide a satisfactory level of protection. For example, cold feet was one of the biggest sources of complaints for Swedish farmers regarding their thermal work environment (Kuklane, 2000). Although a hood is superior in comparison to other possibilities for protecting the face such as a face mask or a scarf (Rintamäki, Mäkinen &

Gavhed, 1998), the problem of combining it with a safety helmet is still unsolved. Personal protective devices used in cold climate can become clumsy and uncomfortable, and therefore prevent the worker from wearing them (Berquist & Abeysekera, 1994).

1.4. Cold risk assessment

1.4.1. Risk assessment in the working life

The employer has a duty to ensure the safety and health of workers in every aspect related to the work, and the employer shall, among other things, be in possession of an assessment of the risks to safety and health at work (Council of the European Communities, 1989).

In Sweden, all employers ‘shall regularly investigate working conditions and assess the risks of any person being affected by ill-health or accidents at work’ (Arbetsmiljöverket, 2001). In Sweden, according to these provisions, the risk assessment should be documented in writing indicating which risks are present and whether or not they are serious.

The British Standard (1996) is intended to assist organisations in developing an approach to the management of occupational health services (OH&S) in such a way as to protect employees and others whose health and safety may be affected by the organisation’s activities. It promotes the adoption of a structured approach for the identification of hazards and the evaluation and control of work related risks.

According to the standard BS 8800 (1996), for many years OH&S risk assessments have usually been carried out on an informal basis. However, it is now recognised that risk assessments are a key foundation for pro-active OH&S management and that systematic procedures are necessary to ensure their success.

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6 Figure 1. The process of risk assessment

(adapted from BS 8800, 1996)

The standard (BS 8800, 1996) recommends for organisations to follow these basic steps for effective risk assessment (see figure 1):

a) to classify work activities, i.e. to prepare a list of work activities and gather information about them;

b) to identify all significant hazards relating to each work activity, considering who might be harmed and how;

c) to determine risk by making a subjective estimate of the risk associated with each hazard, assuming that planned or existing controls are in place;

d) to decide if the risk is tolerable by judging whether planned or existing OH&S precautions (if any) are sufficient to keep the hazard under control;

e) to prepare a risk control action plan (if necessary) to deal with any issues found by the assessment; and

f) to review the adequacy of the action plan, i.e. to re-assess the risks on the basis of the revised controls and check that they will be tolerable.

1.4.2. Cold-related risk factors

Holmér (1998) outlined the relationship between the environmental factors (i.e. air temperature, radiant temperature, humidity and air velocity together with activity and clothing) and the anticipated cooling effects: whole body cooling, local cooling such as extremity cooling, airway cooling (or cooling of respiratory tract), wind chill (or convective skin cooling) and contact cooling (or conductive skin cooling).

Evaluation of the above named types of cold stress requires different sets of measurements (Holmér, 1994), as shown in the figure 2. However, quick estimates (for the purposes of the first rough classification of problems and/or the basis for further action, e.g., for a more detailed assessment or a preventive measure) may be based on the information about the type and intensity of work, air temperature, wind speed and available personal protection (Holmér, 1994).

Classify work activities

Identify hazards

Determine risks

Decide if risk is tolerable Prepare risk control action plan

(if necessary)

Review adequacy of action plan

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Figure 2. Scheme for the identification of cold stress and for the selection of appropriate measurements for its assessment (adapted from Holmér, 1994).

1.4.3. Methods used in cold risk assessment

Methods for the assessment of cold stress may serve several purposes and they may be used to evaluate or predict conditions critical to: survival; risk of acute or chronic adverse health effects; performance; efficiency and productivity; and maintenance of comfort (Holmér, 1993). Occupational exposure to cold generally includes conditions associated with minimal adverse health effects.

The thermal environment can be assessed in either subjective terms or by objective measurements, or both. In the former case individuals are asked to give an opinion on the thermal environment which they are experiencing (Youle, 1995). The methods for the assessment of cold stress based on measurements are presented in ISO technical report 11079 (1993). The complementary information needed for the evaluation of cold stress can be found in other standards: ISO 8996 (1990) regarding determination of metabolic heat production;

ISO 9886 (1992) regarding evaluation of thermal strain by physiological measurements; and ISO 9920 (1995) regarding estimation of the thermal insulation and evaporative resistance of a clothing ensemble.

The risk for whole body cooling is determined by calculating the clothing insulation level required to maintain the heat balance at defined levels of physiological strain. The calculated required clothing insulation value, IREQ, which indicates a protection level can be regarded as a cold stress index (ISO/TR 11079, 1993). Assessment of contact cooling, extremity cooling and airway cooling is based on empirical or predicted values (Holmér, 1998). For example, ISO/TR 11079 (1993) recommends that local cooling caused by convection, radiation or contact heat losses should not result in hand skin temperatures below 15°C and 24°C for high and low stress levels respectively. At temperatures below –40°C, respiratory and eye protection can be required, particularly with high activity levels and strong wind (ISO/TR 11079, 1993). The workers should not have bare hand contact with cold surfaces below –7°C in order to prevent contact frostbite, and they should protect the hands with

Whole body cooling

Extremity cooling

Skin (convective) cooling

Skin (conducive) cooling

Respiratory cooling Type of cold stress

Air temperature

Mean radiant temperature Air velocity

Relative humidity Activity level (Clothing)

Air temperature Air velocity Air temperature Air velocity Air temperature Air velocity

Measurements

Analysis

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mittens if the air temperature is –17.5°C or less (ACGIH, 1989). A method for the assessment of cooling of unprotected skin is called the wind chill index (WCI) which is the chilling temperature that defines the ambient temperature under which calm conditions would produce the same cooling effect as the actual environmental conditions (ISO/TR 11079, 1993).

Holmér (1999) has suggested an approach (see figure 3) that might be used as a framework for the assessment of the possible effects of exposure to cold based on the international standards and other scientific literature available in the field.

Figure 3. Relation between climate, stress, strain and risk assessment (adapted from Holmér, 1999).

1.4.4. A strategy for cold risk assessment

The action model (see figure 4) suggested by Risikko et al. (2003) helps to assess and manage the cold-induced health and safety risks at work. The methods available for the assessment of cold exposure are very few and rely more or less on complex equations for calculating heat balance (Holmér, 1991). Therefore a certain level of expertise is needed for successful application of these procedures that might not be available to OH&S people especially in small and medium-sized enterprises (SMEs).

Malchaire, Gebhardt and Piette (1999) addressed this problem and proposed a strategy for the evaluation and prevention of risk due to work in thermal environments, which rests on two basic principles: it is participative and structured in four stages - ‘Screening’, ‘Observation’,

‘Analysis’ and ‘Expertise’ - that require complementary knowledge and competence.

According to this strategy, after the screening of the workplace, the second stage

‘Observation’ should provide a method for identifying particular circumstances, specific tasks or certain working conditions where problems related to work in cold exist and guidelines for the elimination of the problem. At the end of this stage the decision has to be made whether the problem is satisfactory controlled; and if not, the third stage ‘Analysis’ of the risk assessment has to be carried out with the help of occupational hygienists or persons with

Air temperature Wind

Humidity Radiation Activity Clothing Precipitation Work organisation

Whole body cooling Extremity cooling Skin convective cooling Skin contact cooling Respiratory cooling

Discomfort Pain Cold Injury Cardiac Peripheral circulation Respiration Muscular function and performance

Individual factors Gender Age Health Fitness Acclimatisation Training Experience Judgement Cold climate Cold stress Strain/ effect

Stress prediction

‘normal’ response

Stress prediction

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adequate training. If the problem still persists the fourth stage ‘Expertise’ has to be addressed ( Malchaire, Gebhardt & Piette, 1999).

The above named methods for cold risk assessment are mostly intended for the stages

‘Analysis’ or ‘Expertise’ due to their complexity and the specific training required. A recent field study (Mäkinen & Hassi, 2002) testing the usability of ISO thermal standards reported that the methods described in these standards were mostly useful in the more advanced stages of cold risk assessment. Furthermore, concerning the assessment of cold environments there are no instructions for how to use the present ISO thermal standards in a complementary way in practical workplace assessments. It was concluded (Mäkinen & Hassi, 2002) that there is a clear need for new practical methods to identify and control cold hazards in workplaces which could be used in the ‘Observation’ stage.

Figure 4. Cold risk management model for a company (adapted from Risikko et al., 2003).

Company’s policies and management systems Occupational health & safety (OH&S) LEGISLATION & REGULATIONS

international & national

general labour safety legislation & norms

industry-specific safety regulations

occupational health care legislation & regulations

trade agreements etc.

COLD RISK MANAGEMENT AT WORKPLACE Cold risk assessment

Preventive measures against cold

Supportive information

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2. Objectives of the study

The aims of the thesis were:

(a) to test the usability of the developed observational checklist for cold risk assessment for use in the ‘Observation’ stage by workers themselves or by those responsible for work organisation who usually lack training in ergonomics or human factors.

(b) to test the checklist at workplaces in a country representing a different approach to safety culture than the one prevailing in Scandinavian countries.

(c) to test whether there was a learning effect reflected in the results recorded in the evaluation sheets when filled in after conducting the cold risk assessment procedure for the first, second and third time.

(d) to validate the checklist for the identification of cold-related problems under laboratory conditions in terms of whether the checklist generated results were in agreement with the subjects’ physiological measurements and self-reported observations of their thermal state.

(e) to identify cold-related risk factors that some workers face in their work environment.

(f) to investigate whether the region where the checklist was filled in, type of work (indoor versus outdoor work), ambient temperatures and the sector that the company represented had any influence on the ratings that these factors received.

(g) to validate the Edholm scale and the ISO 8996 standard by comparing the metabolic rates estimated for both methods with the actual measured metabolic rate (MMeas) in six manual material handling tasks simulated under laboratory conditions.

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3. Materials and methods

3.1. The development of the checklist

The checklist (see annex 1 of the Paper I) was developed in a common effort by Finnish and Swedish research teams. It followed the recommendations for the ‘Observation’ method based on the results of validations carried out by 42 trained people in occupational health who worked primarily in SMEs and were confronted with climatic problems (Malchaire, Gebhardt

& Piette, 1999). According to these guidelines, a checklist should be designed for use by people in industry (preferably by the workers themselves). It should be easy to understand even by untrained people (no references to concepts or technical terms), easy to use (the maximum required time no longer than one hour), based on simple observations (no measurements involved), oriented towards prevention and utilising the user’s knowledge of the workplace (Malchaire, Gebhardt & Piette, 1999).

The relationship between climatic factors, i.e., low surface temperature, low air temperature and wind, and the anticipated cooling effects, i.e., whole body cooling and local cooling such as extremity cooling, airway cooling (or cooling of the respiratory tract), wind chill (or convective skin cooling) and contact cooling (or conductive skin cooling) is well known (Holmér, 1998). Although the evaluation of the above named types of cold stress requires different sets of measurements, a quick estimate (for the purposes of the first rough classification of problems and/or the basis for further action, e.g., for a more detailed assessment or a preventive measure) may be based on information about the type and intensity of work, air temperature, wind speed and available personal protection (Holmér, 1994).

The developed checklist has seven main sections of cold-related risk factors: cold air, wind/air movements, contact with cold surfaces, exposure to water/liquids/moisture, protective clothing against cold, protection against cold: hands, feet and head and the use of personal protective equipment. Each of these seven sections has a choice of three levels (or ratings) for the risk factor and each level contains examples, facilitating the rating process. The following rating scale was applied: score 1 means that there is no need for preventive actions, score 2 indicates that corrective actions are recommended in the long term and score 3 denotes immediate need for corrective action. The same rating scale, although without examples for each level, applies to section 8 ‘Other problems related to work in cold’ that includes: long periods of time in cold, light work, variation between light and heavy work, variation of environmental conditions, slipperiness and insufficient lighting.

An important risk factor, low activity level or rate of work was not included in the seven main sections while two other categories, ‘Light work’ and ‘Variation between light and heavy work’ were added under section 8 instead. The likelihood of the appearance of one or more defined cold problems is very dependent on the combination of two variables: the temperature and the activity level (Holmér, 1998), which makes it difficult to interpret. For example, to rate light work at the very risky activity level would not be right for temperatures above zero, whereas it would be true for low temperatures.

The checklist is accompanied by instructions on how and when to use the checklist and a summary table that helps to interpret the results. The instructions attached to the summary table give a more detailed explanation of the scoring scale. Besides the score columns, the table has a column ‘A further investigation needed’ that has to be marked when the problem cannot be solved at this stage of risk assessment procedure and the third stage ‘Analysis’ has

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to be addressed. The other column ‘Preventive measures’ in the summary table is reserved for choosing the appropriate preventive measures.

3.2. Subjects Study I

In Finland, four foremen filled in a checklist and a checklist evaluation sheet 31 times, three occupational nurses did it nine times and seven workers carried out the procedure 18 times. In the cases of the foremen and occupational nurses (except for the two nurses at the electrical installations company), the same person evaluated several working activities at the workplace on a single occasion using separate checklists and evaluation sheets for each observed activity. Therefore, the total number of the returned checklists and evaluation sheets is higher than the total number of the persons multiplied by the checklist testing occasions.

In Sweden, the checklist was tested at two construction companies, a road building company and a district office of the National Board of Forestry in the Northern part of Sweden. Both the workers (13) and the foremen (5) in these companies tested the risk assessment procedure.

Study II

The cold-related risk factors were observed 277 times at two sawmills by nine foremen (27 checklists were filled in) and 105 workers (250 checklists). Only the workers that were currently working outdoors on the day when the authors visited the two sawmills for the first and second time were asked to volunteer for the study. In the original study design it was intended that all observers should conduct the risk assessment procedure three times;

therefore it was not possible for additional workers to join the study on a later occasion.

However, some of the observers dropped out and only 88 of 116 volunteers filled in the checklist twice and only 73 of them did it three times.

Study III

Eight healthy non-smoking male subjects volunteered to participate in the experiment. The subjects were of 22–38 years of age (mean=28, SD=5), 53.0–87.6 kg of weight (mean=71.6, SD=11.1) and of 1.70–1.89 m of height (mean=1.81, SD=0.06). The subjects’ body surface area according to Du Bois ranged from 1.60 to 2.14 m² (mean=1.91, SD=0.07). The subjects had the following occupations: a warehouseman (1), a medical doctor (1), a student (5), and a university lecturer (1). None of the subjects could be characterised as working in cold environments. However, all of them had a previous experience of cold exposures to temperatures at least as low as –20°C.

Study IV

Cold-related risk factors were assessed at 14 companies in four countries: Finland, Norway, Sweden (during December 2000 – April 2001) and north-western Russia (during December 2003 – March 2004). An observational checklist for the assessment of cold-related risk factors was used by 196 selected observers. A total of 164 checklists were filled in the Nordic countries and 277 checklists were filled in north-western Russia (Archangelsk region).

In Finland, four foremen, three occupational nurses and seven workers observed cold-related risk factors at two construction companies (29 checklists filled in), two stevedoring and cargo handling companies (28 checklists), the skiing and arctic golf centre (6 checklists) and a small company providing electrical installation services (9 checklists). There were 72 checklists in total returned by Finnish observers. In Norway, the cold-related risk factors were observed 48 times at two fish processing companies by an occupational health and safety representative

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(1) and workers (47). In Russia, the cold-related risk factors were observed 277 times at two sawmills by nine foremen (27 checklists were filled in) and 105 workers (250 checklists). In Sweden, a total of 44 checklists were filled in at two construction companies (21 checklists), a road building company (4 checklists) and a district office of the National Board of Forestry in the Northern part of Sweden (19 checklists). Both the workers (13) and foremen (5) at these companies observed the cold-related risk factors.

Study V

Nineteen (14 males, 5 females) healthy subjects volunteered to take part in the experiment.

Before the experiment, the subjects were informed on all details of the experimental procedures and the associated risks and discomforts. The subjects’ mean age was 29.0 years, SD was 5.4 years, average body mass was 69.2 kg, SD was 12.7 kg, average height was 1.72 m, SD was 0.09 m and average estimated body surface (area Dubois) was 1.81 m², SD was 0.17 m². The subjects were asked to abstain from strenuous physical activity on the morning of the measurement in order to minimise residual effects of activity on the metabolic rate measurements.

3.3. Procedure Study I

The study was carried out in the northern part of Finland and Sweden during December 2000 and April 2001. All the materials were prepared in English and later were translated into Finnish and Swedish. The training and testing of the checklists were conducted identically in each country.

The purpose of the study was explained to subjects who tested the usability of the checklist.

After this the authors of the article together with the observer went through the instructions, the cold risk assessment checklist, the analysis table and the evaluation sheet (see appendix I).

The observers were asked to perform the cold risk assessment procedure and to fill in the evaluation sheet for the checklist usability independently of the previous times, if any were already carried out. The subjects were also specifically asked to use a separate checklist evaluation sheet after each checklist was filled in. The observers themselves chose the time for conducting the risk assessment procedure. The assessment procedure was performed various times per subject.

Study II

The study was carried out in the region of Archangelsk, north-western Russia, from December 2003 until March 2004. The purpose of the study was explained to observers who tested the usability of the above named checklist. After this the authors of the article together with the observers went through the instructions, the cold risk assessment checklist, the analysis table and the evaluation sheet (see appendix I). The one-page checklist evaluation sheet was attached to the checklist.

Study III

Tests were carried out during the winter season (January–February, 2005). Each subject performed each of the six activities during the same period of the day with intervals of at least one day in between the experiments.

All clothes worn by the subjects during the particular activity (see table 1 in Paper I), skin temperature measurement sensors and heart rate measuring device were weighed several times during the experiment. The sensors were taped on the subjects’ skin with adhesive tape covering the thermistors.

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The subjects were performing activities A, B, C, D and E for 90 minutes and activity F for 60 minutes (see table 1 in Paper I). During activities B, C, D and E the subjects walked on a treadmill and during activity F they were standing still. In the beginning of activity A, the subjects were sitting and screwing metal bolts with bare hands (activity A1). After 20–30 minutes (depending on the subjective assessment of the subjects whether it was appropriate to continue until the estimated time of 30 minutes had elapsed), the stepping test (activity A2) was performed for 20–25 minutes, depending on the physical fitness of the subjects. At the end of activity A, the subjects were screwing the bolts again, but this time the bolts were wet and the subjects were wearing gloves (activity A3).

Exhaled air was collected with Douglas bags and the average value was used as a representative value for the whole activity. The ambient air (for O2 and CO2 concentrations) in the climatic chamber was sampled and analysed for periods when exhaled air was collected. The metabolic rate ( M ) for each activity was determined based on the measured

O2

V (ISO 8996, 1990).

The rectal temperature was measured to represent the body core temperature (T_core). The mean skin temperature (T_skin), was calculated from the temperatures measured by the thermistors positioned on the subjects’ forehead, left scapula, left chest, left upper arm, left forearm, left dorsal hand, left anterior thigh and left calf. In order to measure finger skin temperatures thermistors were placed on the first phalanxes of the left little finger (T_litle_{_}_finger) and the right index finger (T_index_{_}_finger). Toe skin temperatures were derived from thermistors placed on the dorsal first phalanx of the left second toe (T ) and facial temperature was _toe obtained from a thermistor placed on the left cheek (T_cheek). The latter four temperatures were used as a control (during the experiment) and reference temperatures for recorded subjective thermal sensations. Mean body temperature (T_body) was calculated as a sum of mean skin temperature, T_skin, (with coefficient 0.2) and body core temperature, T_core, (with coefficient 0.8). The body heat storage ( S ) was calculated as a function of the rate of change in mean body temperature T_body.

The subjects’ perceived observations of the thermal sensation of the body, face, hands and feet were recorded using a scale from +4 (very hot) to –4 (very cold). Along with thermal sensations, the subjective judgments on thermal comfort/discomfort on a scale from 0 (comfortable) to 4 (very uncomfortable) and thermal preference on a scale from +3 (much warmer) to –3 (much cooler) were recorded as well. Pain sensations in the feet, hands and face were recorded on a scale from 0 (no pain) to 4 (very very painful). These subjective judgments on the subjects’ thermal state and sensations were recorded immediately upon entering the climatic chamber and at each 10^th minute during the performed activity.

The subjects filled in the checklist for identifying cold-related problems at work after the experiment was finished and they had changed back into their own clothes.

Study IV

An observational checklist for the assessment of cold-related risk factors was used to assess cold-related risk factors. The authors provided identical instructions and training on how to carry out the cold risk assessment procedure to the observers in all four countries and prepared the needed material including the checklist itself in each country’s national language. Each observer was asked to perform the cold risk assessment procedure and to fill

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in the checklist independently of the previous times, if any were already carried out. The assessment procedure was performed various times per observer.

Study V

The study was limited to involve activities of low and moderate metabolic rate. Six manual material handling tasks occurring in normal work were designed under laboratory conditions (see table 1 of Paper V). A metabolic rate value (MEdh) for each of the activities was derived from the Edholm scale (Edholm, 1966) as well as MISO from ISO 8996 (1990) tables. The subjects performed the tasks in a random sequence.

The oxygen consumption (VO₂) was measured every ten seconds continuously under the whole time of experiment without subjects taking off the facemask. The morning resting metabolic rate (MRest) at normal room temperature was measured to obtain a reference point in the study before measuring metabolic rates, when subjects were performing various tasks.

Each subject was assigned randomly one task after another till all six simulated tasks were performed. Additionally subjective estimates of exertion were obtained using the RPE scale (Borg, 1970). Before the experiment began, the subjects were instructed how to rate the degree of exertion. They were asked to rate it as accurately and naively as possible. After the particular activity was finished, the scale was shown to a subject immediately and the subject was asked to mark a number on the scale according to how the work was experienced.

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4. Results and discussion

4.1. The usability of the checklist

The results of testing the observational checklist showed that it complies well with the recommendations given by Malchaire, Gebhardt & Piette (1999) for the ‘Observation’

method. According to the field testing results, the developed checklist is an observational method that does not require comprehensive training or knowledge in the assessment of thermal environments, and it causes no interference with the observed work activities. The majority of the observers could easily conduct the risk assessment procedure according to the instructions they had received and found it easy to use the observational checklist. Although there was a difference in the experienced checklist facility between the Finnish and Swedish groups, the majority of the evaluation sheets in each of group indicated that it was easy to use the checklist.

Furthermore, the persons who should be performing the cold risk assessments, as suggested by the observers, are the ones who are very well versed in the content of the work. According to the Finnish observers, a workers’ representative responsible for industrial safety and workers themselves should carry out the assessment procedure. This approach was supported by the answers in the Swedish evaluation sheets where workers at the workplace were indicated most often.

According to Malchaire, Gebhardt & Piette (1999), the maximum time required to perform the risk assessment procedure on the ‘Observation’ level should be no longer than one hour.

After applying stricter requirements to the data and reducing the sample size to 70 evaluation sheets, there were only two evaluation sheets where it was indicated that observers needed longer than one hour (a time of 75 minutes was indicated in one Finnish evaluation sheet and 105 minutes was indicated in one Swedish evaluation) to perform the risk assessment procedure. Based on the results, it can be concluded that the expected time for carrying out the cold risk assessment procedure at a workplace is between 20 and 30 minutes.

The statistically significant difference between the times taken to perform the whole risk assessment procedure by the Swedish and Finnish groups could have resulted from the significant differences in time taken to perform the preparation stage. A possible explanation for the differences in time needed to conduct the preparation stage is the fact that information was presented to the groups in different languages (although the content of the written information was identical) and that different groups of the authors had trained the observers.

The time to perform a risk assessment procedure would probably be longer if the stage of

‘Further procedures’ were included in the calculation of the total time. However, only 44% of the answer sheets had times indicated for this stage. Furthermore, there was no clear understanding among observers about what the further procedures should include (for example, some of them included the travel time to and from the observed worksite).

Therefore, the total time was a sum of only three stages. On the other hand, the fact that the observers received training and instructions in person could have shortened the time needed to perform the risk assessment procedure. Another factor that might have reduced the time needed to perform the procedure is the fact that individual observers had tested the checklist and filled in the evaluation sheets several times (on average approximately 2.5 evaluation sheets per observer). However, the study design is such that it does not allow verifying the hypothesis of whether a learning effect made a difference in the time needed to conduct the cold risk assessment procedure after the checklists was used for the first, second or third time.

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Similarly to the results of field testing in the Nordic countries, the observational checklist was found to be a usable tool for cold risk assessment, even when applied to companies with a different approach to safety culture. The results corresponded in terms of the instructions provided for the checklist and summary table; the facility of the checklist and summary table and the suitability of the checklist (in regards to the structure and content) for identifying cold-related risk factors. Furthermore, it complies well on these aspects with the recommendations given by Malchaire, Gebhardt & Piette (1999) for the ‘Observation’

method. The fact that no signs of learning effects in the evaluation sheets filled in after conducting the risk assessment procedure for the first, second and third time were found strengthens the idea that the checklist is rather straightforward and easy to use.

According to the Nordic observers, a workers’ representative responsible for industrial safety and the workers themselves should carry out the assessment procedure at the workplace. On the contrary, the Russian observers indicated workers only in 7.5% of the evaluation sheets, giving priority to a safety engineer (indicated in 50.5% of evaluation sheets) and a foreman (indicated in 22.6% of evaluation sheets). This contradicts the recommendation of (Malchaire, Gebhardt & Piette (1999) that the persons performing the cold risk assessments should be the ones who are very well versed in the content of the work. In the case of Russian observers, it highlights a very interesting situation as the work safety engineer (category most often suggested by the observers) in one of the companies did not even know how many of the employees were working outdoors. The very low percentage of evaluation sheets where the alternative denoting the workers themselves was selected is likely an indication that the observers either have no interest or belief in their ability to influence or change their working environment.

According to Malchaire, Gebhardt & Piette (1999), the maximum time required to perform the risk assessment procedure on the ‘Observation’ level should be no longer than one hour.

As each of the stages: preparation, realisation and analysis of results was most often described by the category of ‘less than 15 min’, the total time for performing the three categories is expected to be less than 45 minutes. There were differences in the categories chosen to describe the time needed to perform the last stage: discussion of results after conducting the cold risk assessment procedure for the first, second and third time. As the majority of the evaluation sheets filled in after the checklist was used for the first time indicated that no discussion took place on the possible preventive measures, the total time to carry out all four stages would be the same – under 45 minutes. After filling in the checklist for the second and third time, the absolute majority of the evaluation sheets suggested an expected total time for conducting all four stages of the assessment procedure to be a sum of four categories of ‘less than 15 min’, still in the line with the recommendations of Malchaire, Gebhardt & Piette (1999).

4.2. The validation of the checklist

The calculated mean M , HR , S and a change in mean body temperature ('T_body) as well as the reported subjective thermal sensations in the whole body, feet, hands and face for all activities are shown in the table 2 of Paper III. T_body for each activity is also depicted in figure 1 of Paper III. Mean T_cheek, T_litle_{_}_finger, T_index_{_}_finger and T for each activity are portrayed in _toe figures 2–7 of Paper III. The results from the subjects’ evaluations of the thermal conditions with the help of the checklist as well as the number of subjects who gave the same most common score for a particular cold-related risk factor during each performed activity are reported in table 3 of Paper III.

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The number of subjects who assessed the particular cold-related risk factor by means of the checklist in conformity to their reported thermal sensations and measured skin temperatures varied most often from five to eight for the factors that were relevant to the performed activity (see table 1). In some rare cases, only one, two or three subjects gave evaluations of the particular cold-related risk factor that agreed to their thermal sensations and measured skin temperatures. In particular, this was the case for risk factors concerning the presence of light work and protection of extremities against cold, when several work tasks were performed under the same experiment. In the case of non-relevant factors, most often seven or all eight subjects gave scores corresponding to the instructions given to subjects prior to the experiment.

Table 1. The number of subjects who assessed the particular cold-related risk factor in accordance with the reported thermal sensations and measured skin temperatures or in agreement with given instructions, in the case of non–relevance.

Activity Risk factor

A B C D E F

Cold air 6 6 4 5 5 6

Wind/ air movements 5 7 7 6 7 7

Touching cold surfaces 6 8 8 8 8 8

Water/ liquids/ damp 8 7 7 7 7 7

Protective clothing against cold 4 8 8 8 8 8

Protection of extremities against cold 2 7 6 6 5 5

Use of PPE 6 8 8 8 7 8

Identification and validation of risk factors in cold work

DOCTORA L T H E S I S DOCTORA L T H E S I S

Identification and validation of risk factors in cold work

Lina Giedraitytė

G G G G G G G G

Identification and validation of risk factors in cold work

by

Lina Giedraityt ŝ

August, 2005

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Preface

Abstract

List of publications

Table of contents

1. Introduction

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2. Objectives of the study

3. Materials and methods

4. Results and discussion