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Chemical exposure in the work place: mental models of workers and experts
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine.
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Many workers are daily exposed to chemical risks in their work place that has to be assessed and controlled. Due to exposure variability, repeated and random measurements should be conducted for valid estimates of the average exposure. Traditionally, experts such as safety engineers, work environment inspectors, and occupational hygienists, have performed the measurements. In self assessment of exposure (SAE), the workers perform unsupervised exposure measurements of chemical agents.

This thesis studies a prerequisite for SAE, i.e. the workers’ mental models of chemical exposure. Further, the workers’ mental models are contrasted with experts’ reasons and decision criteria for measurement.

Both qualitative and quantitative data generated from three studies (Paper I, II, and III) were used to describe the workers’ mental model of chemical exposure. SAE was introduced to workers in three different industries; transports (benzene), sawmill industry (monoterpenes), and reinforced plastic industry (styrene). By interviews, qualitative data were collected on the workers’ interpretation of measurement results and preventive actions. To evaluate the validity of worker measurement, the measurements were compared with expert measurements. The association between each worker’s number of performed measurement and mean level and variability in exposure concentrations was calculated. Mean absolute percent/forecast error (MAPE) was used to assess whether the workers’ decision models were in accordance with a coherence or correspondence model. In Paper IV, experts (safety engineers, work environment inspectors, and occupational hygienists) were interviewed to elucidate their mental models about the triggers and decision criteria for exposure measurements.

The results indicate that the workers’ measurement results were in agreement with experts’. However, the measurement results were not a strong enough signal to induce workers to take preventive actions and sustained exposure measurements even if the measurement result were close to the occupational exposure limit. The fit was best for the median model, indicating that the workers’ mental models for interpretation of measurement data can best be described by the coherence theory rather than by the correspondence theory. The workers seemed to mentally reduce the variation in the exposure to a measure of central tendency (the median), and underestimated the average exposure level. The experts were found to directly take preventive actions instead of performing exposure measurements. When they performed exposure measurements, a worst case sampling strategy was most common. An important trigger for measurement for the experts was “request from the employer” (safety engineers), “legal demands” (work environment inspectors), and “symptoms among workers” (occupational hygienists). When there was a trigger, all experts mentioned expectations of high exposure level as a decision criterion for measurements.

In conclusion, the studies suggest that workers’ mental interpretation model is best described in terms of a coherence model rather than a model of correspondence. The workers reduced the variation mentally in favor of an estimate of average exposure (median), which may imply that they underestimate short-term, high exposure health risks. A consequence is that interpretation of measurements such as SAE cannot be given to the individual worker without some support, e.g. from an expert. However, experts often chose to directly take preventive actions, without measuring the exposure. The results indicate that also the experts need support e.g. from the legal system if exposure measurements are to be done.

Place, publisher, year, edition, pages
Umeå: Yrkes- och miljömedicin , 2008.
Umeå University medical dissertations, ISSN 0346-6612 ; 1173
Keyword [en]
self-assessment of exposure, predictions, expert judgment, risk, interpretation, time series analysis, MAPE, benzene, monoterpenes, styrene
Research subject
Occupational and Environmental Medicine
URN: urn:nbn:se:umu:diva-1646ISBN: 978-91-7264-548-6OAI: diva2:141686
Public defence
2008-05-28, NUS, sal B, plan 9, By 1D, Umeå universitet, Umeå, 09:00 (English)
Available from: 2008-05-12 Created: 2008-05-12 Last updated: 2011-06-08Bibliographically approved
List of papers
1. Self-assessment of exposure: a pilot study of assessment of exposure to benzene in tank truck drivers
Open this publication in new window or tab >>Self-assessment of exposure: a pilot study of assessment of exposure to benzene in tank truck drivers
Show others...
2000 (English)In: Applied occupational and environmental hygiene, ISSN 1047-322X, Vol. 15, no 2, 195-202 p.Article in journal (Refereed) Published
National Category
Environmental Health and Occupational Health
urn:nbn:se:umu:diva-3187 (URN)10.1080/104732200301692 (DOI)10675977 (PubMedID)
Available from: 2008-05-12 Created: 2008-05-12 Last updated: 2015-02-13Bibliographically approved
2. Workers' interpretation of self-assessment of exposure
Open this publication in new window or tab >>Workers' interpretation of self-assessment of exposure
2008 (English)In: The Annals of occupational hygiene, ISSN 1475-3162, Vol. 52, no 7, 663-671 p.Article in journal (Refereed) Published
Abstract [en]

OBJECTIVES: The aim was to investigate how workers interpret and act upon results from self-assessment of exposure (SAE). METHODS: Workers in four sawmills in Sweden were supplied with diffusive samplers for measurement of terpenes. Workers received both oral and written instructions about terpenes, their medical effects and how to handle the samplers. Responsibility for sampling was left to the individual worker; written feedback about terpene levels was provided after each measurement. The number of measurements was registered. The workers and supervisors were interviewed about their attitudes, perceived control of their work environment, need for preventive actions and future surveillance of the workplace. RESULTS: In total, 28 workers performed 100 terpene measurements. At one sawmill, there was a significant association between exposure levels and the number of measurements performed by each worker (rho = 0.79, P = 0.03). Contrary to instructions, supervisors played an important role in spontaneous organization of the measurements at each mill. Four measurements revealed terpene concentrations that exceeded the occupational exposure limits, and one preventive action was taken as a consequence of high levels. Seventy percent of the workers could not identify any reason for more measurements. Only 15% considered the measurements as their 'own' project, and the rest stated that they participated in order to satisfy the researchers. CONCLUSIONS: Previous studies have shown that workers can perform valid measurements, both select a day and technically perform measurements. This study indicates that this ability is not sufficient to ensure that measurements will be done or that implementing measurements will result in preventive actions. Workers need additional support to take preventive actions and use SAE for ongoing surveillance.

urn:nbn:se:umu:diva-19674 (URN)10.1093/annhyg/men042 (DOI)18660506 (PubMedID)
Available from: 2009-03-09 Created: 2009-03-09 Last updated: 2011-06-08Bibliographically approved
3. Workers’ mental models of chemical exposure in the workplace
Open this publication in new window or tab >>Workers’ mental models of chemical exposure in the workplace
2010 (English)In: Risk Analysis, ISSN 0272-4332, E-ISSN 1539-6924, Vol. 30, no 3, 488-500 p.Article in journal (Refereed) Published
Abstract [en]

The objective of this study was to examine workers’ mental interpretation models developed in response to occupational chemical exposure. The study was performed in six companies within the reinforced plastics industry in northern Sweden, in which styrene was used; 32 workers participated in the study. Each worker performed between four and seven exposure measurements. Before receiving each result of the second to seventh measurements, the workers were asked to predict the level of their next exposure measurement. Their predictions were evaluated with respect to two judgmental principles: coherence (that the predictions are based on logical decision rules, that is, the mean value of the prior exposure levels); and correspondence (the predictions have high empirical accuracy) by calculating the mean absolute percent forcast error (MAPE). The coherence principle was tested by comparing each of the workers’ predictions with the mean, median, and last exposure level (last value) of the prior measurements. The correspondence principle was tested by comparing the worker’s prediction with the outcome of the measurement. The coherence principle was found to be the best descriptor of the workers’ predictions and the median model had the best fit. The mean model had a similar but significantly poorer fit (MAPE values of 29 and 31, respectively). The correspondence model had a poor fit with a MAPE of 54. The workers’ predictions were generally lower than their average exposures. We conclude that the workers’ interpretation model can be best described by a coherence model rather than by a correspondence model.

Chemical exposure, judgmental models, risk perception
National Category
Environmental Health and Occupational Health
Research subject
urn:nbn:se:umu:diva-33175 (URN)10.1111/j.1539-6924.2009.01347.x (DOI)000275338700021 ()20136744 (PubMedID)
Available from: 2010-04-14 Created: 2010-04-14 Last updated: 2011-09-15Bibliographically approved
4. When and why do experts perform exposure measurements?: An exploratory study of safety engineers, work environment inspectors, and occupational hygienists.
Open this publication in new window or tab >>When and why do experts perform exposure measurements?: An exploratory study of safety engineers, work environment inspectors, and occupational hygienists.
2006 (English)In: Journal of Occupational and Environmental Hygiene, ISSN 1545-9624, E-ISSN 1545-9632, Vol. 3, no 12, 713-717 p.Article in journal (Refereed) Published
Abstract [en]

The aim of this study was to describe experts' decision processes leading to measurements of occupational chemical exposure. Safety engineers, clinical occupational hygienists, and work environment inspectors (four from each group) were interviewed according to a semistructured scheme. We analyzed: (i) perceived triggers for measurements, (ii) the experts' decision criteria for performing measurements when there was a trigger, and (iii) sampling strategy. Regarding triggers, all safety engineers reported a “request” from, for example, an employer; all work environment inspectors reported “legal demands;” and all clinical occupational hygienists reported “symptoms among workers.” As a decision criterion, all the interviewees reported that they measured only if they expected sufficiently high levels. The results of the present study highlight factors that trigger measurements and are of importance in determining whether measurements will be performed. These factors appear to be related to the expert's professional role and may bias the assessment of exposure. Thus, when using data from routine measurements done by experts, the possibility of a bias needs to be considered.

Decision Making, Occupational Exposure, Occupational Health/statistics & numerical data, Safety, Workplace
National Category
Medical and Health Sciences
Research subject
urn:nbn:se:umu:diva-9186 (URN)10.1080/15459620601015893 (DOI)17133692 (PubMedID)
Available from: 2008-03-07 Created: 2008-03-07 Last updated: 2011-06-08Bibliographically approved

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