Identification and validation of risk factors in cold work

University dissertation from Luleå : Luleå tekniska universitet

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 the checklist at workplaces in a country representing a different approach to safety culture than the one prevailing in Scandinavian countries. A secondary objective was 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. A total of 277 evaluation sheets were obtained from 116 observers from 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 for the checklist and to the summary table; the facility of the checklist and summary table and the suitability of the checklist (in regards to the structure and content) in identify cold- related risk factors. 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 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) were compared (N=73). 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 0C, walking at 3.5 km/hour and 4.9 km/hour in -10C and at 3 km/hour in -25C and standing still at +4C 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 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 (M_Meas) 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 (M_Edh) overestimated five of six activities by 34-50% (significance level .05). The metabolic rates derived from ISO 8996 (M_ISO) overestimated all activities by 7-38% (significance level .05).