The sick building syndrome: prevalence studies.

Random samples or the entire workforce in nine offices in which similar clerical work was being performed were studied using a doctor administered questionnaire that inquired into symptoms that have been linked with the "sick building syndrome." Five of the offices were fully air conditioned, one had recirculation of air and mechanical ventilation, and three were naturally ventilated. Workers in three air conditioned and three naturally ventilated buildings were interviewed blind. Seven of the buildings were studied at our request in the absence of any known problem. Comparison of prevalences of symptoms between the naturally ventilated and the other buildings showed a repeated pattern of nasal, eye, and mucous membrane symptoms with lethargy, dry skin, and headaches. There were highly significant excesses of these six symptoms in the air conditioned buildings when compared by chi 2 tests with the naturally ventilated buildings. It is suggested that these six symptoms represent the sick building syndrome and that the size of the problem is probably greater than is currently recognised. Possible causes are discussed.     

Thermal comfort in naturally ventilated and air-conditioned buildings in humid subtropical climate zone in China

A thermal comfort field study has been carried out in five cities in the humid subtropical climate zone in China. The survey was performed in naturally ventilated and air-conditioned buildings during the summer season in 2006. There were 229 occupants from 111 buildings who participated in this study and 229 questionnaire responses were collected. Thermal acceptability assessment reveals that the indoor environment in naturally ventilated buildings could not meet the 80% acceptability criteria prescribed by ASHRAE Standard 55, and people tended to feel more comfortable in air-conditioned buildings with the air-conditioned occupants voting with higher acceptability (89%) than the naturally ventilated occupants (58%). The neutral temperatures in naturally ventilated and air-conditioned buildings were 28.3°C and 27.7°C, respectively. The range of accepted temperature in naturally ventilated buildings (25.0∼31.6°C) was wider than that in air-conditioned buildings (25.1∼30.3°C), which suggests that occupants in naturally ventilated buildings seemed to be more tolerant of higher temperatures. Preferred temperatures were 27.9°C and 27.3°C in naturally ventilated and air-conditioned buildings, respectively, both of which were 0.4°C cooler than neutral temperatures. This result suggests that people of hot climates may use words like “slightly cool” to describe their preferred thermal state. The relationship between draught sensation and indoor air velocity at different temperature ranges indicates that indoor air velocity had a significant influence over the occupants’ comfort sensation, and air velocities required by occupants increased with the increasing of operative temperatures. Thus, an effective way of natural ventilation which can create the preferred higher air movement is called for. Finally, the indoor set-point temperature of 26°C or even higher in air-conditioned buildings was confirmed as making people comfortable, which supports the regulation in China that in public and office buildings the set-point temperature of air-conditioning system should not be lower than 26°C.     

Air movement preferences observed in naturally ventilated buildings in humid subtropical climate zone in China

Occupants’ preferences for air movement in naturally ventilated buildings have been extracted from a database of three thermal comfort surveys conducted in the humid subtropical climate zone in China, during winter, spring, and summer seasons. The distribution of draft sensation shows that only 25.7, 38.5, and 28.7% of the subjects in winter, spring, and summer, respectively, felt that the available air movement was just right, suggesting that indoor air velocity may be a big problem in naturally ventilated buildings in humid subtropical China. Air movement preferences show that 15.8, 61.3, and 80.6% of subjects in winter, spring, and summer, respectively, wanted more air movement. Only a handful of subjects wanted less air movement than they were actually experiencing in any season, suggesting that draft was not much of an issue for thermal comfort. Occupants’ preference for air movement is strongly related to thermal sensation, showing that people want to control air movement as a means of improving their comfort. The demand for less air movement under cool sensation is much smaller than the overwhelming demand for more air movement when the sensation was warm. The above results indicate that air movement might have a significant influence over the respondents’ comfort sensation and that people required a high level of air movement in order to be comfortable during the summer season. Thus, one efficient way to improve the thermal environment in summer in humid subtropical China could be to provide occupants with effective natural ventilation and allow personal control of the air movement. Our findings are also applicable to other buildings, to encourage designers to provide air movement as a low energy cooling strategy and to ensure that sufficient levels of air movement are available.     

Odors and Sensations of Humidity and Dryness in Relation to Sick Building Syndrome and Home Environment in Chongqing,China

The prevalence of perceptions of odors and sensations of air humidity and sick building syndrome symptoms in domestic environments were studied using responses to a questionnaire on the home environment. Parents of 4530 1–8 year old children from randomly selected kindergartens in Chongqing, China participated. Stuffy odor, unpleasant odor, pungent odor, mold odor, tobacco smoke odor, humid air and dry air in the last three month (weekly or sometimes) was reported by 31.4%, 26.5%, 16.1%, 10.6%, 33.0%, 32.1% and 37.2% of the parents, respectively. The prevalence of parents’ SBS symptoms (weekly or sometimes) were: 78.7% for general symptoms, 74.3% for mucosal symptoms and 47.5% for skin symptoms. Multi-nominal regression analyses for associations between odors/sensations of air humidity and SBS symptoms showed that the odds ratio for “weekly” SBS symptoms were consistently higher than for “sometimes” SBS symptoms. Living near a main road or highway, redecoration, and new furniture were risk factors for perceptions of odors and sensations of humid air and dry air. Dampness related problems (mold spots, damp stains, water damage and condensation) were all risk factors for perceptions of odors and sensations of humid air and dry air, as was the presence of cockroaches, rats, and mosquitoes/flies, use of mosquito-repellent incense and incense. Protective factors included cleaning the child’s bedroom every day and frequently exposing bedding to sunshine. In conclusion, adults’ perceptions of odors and sensations of humid air and dry air are related to factors of the home environment and SBS symptoms are related to odor perceptions.     

Association of sickness absence with poor sleep and depressive symptoms in shift workers

A cross-sectional study was conducted to evaluate the contribution of daily sleep habits and depressive symptoms to sickness absences of shift workers. A self-administered questionnaire that solicited answers about sleep, symptoms of depression, sickness absence, diseases/injuries, and lifestyle factors was submitted to a sample of 522 rotating shift workers between the ages of 18-59 (mean 27) yrs of an electric equipment manufacturing company. The seven features of sleep queried were daily hours of sleep, time to fall asleep, awakening during sleep, early morning awakening, sleep well at night, sufficiency of sleep, and excessive daytime sleepiness at work. The responses were assessed over the subject's previous 1-yr period. Each sleep feature, except daily sleeping hours, was dichotomized by the following responses: (1) taking more than 30min to fall asleep (difficulty initiating sleep; DIS), (2) awakening during sleep almost every day (difficulty maintaining sleep; DMS), (3) early morning awakening almost every day (EMA), (4) sleeping very poorly or not so well at night, (5) definite or somewhat insufficient nightly sleep, and (6) excessive daytime sleepiness at work almost every day (EDS). Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression (CES-D) scale. Sickness absence was calculated by asking subjects "How many days in total have you been absent from work due to sickness, including paid vacation, in the last 1-yr period?" The responses were divided into three groups that included no (0 days) sickness absences (reference group, n=235 subjects), 1 to 4 days (short-term, n=199 subjects), and 5 days or more (long-term, n = 88 subjects). Compared to the prevalence of sleep features of the reference group, workers with short-term absence showed a significantly higher prevalence of EMA with an odds ratio (OR) of 5.3, 95% confidence interval (CI) 1.3-22.0. Long-term absence was significantly associated with DMS (OR = 2.1, 95%CI 1.0-4.6), EMA (OR = 5.6, 95%CI 1.0-28.7), sleeping poorly at night (OR= 2.6, 95%CI 1.4-5.0), and high depressive symptoms (OR = 2.0, 95%CI 1.0-3.7) according to the CES-D score of >16, after adjusting for multiple confounding variables. These data point to an association between both the parameters of poor sleep and symptoms of deep depression when self-reported sickness absence is frequent. The association is particularly strong with long-term absence in male shift workers.     

Air movement preferences observed in office buildings

Office workers’ preferences for air movement have been extracted from a database of indoor environmental quality surveys performed in over 200 buildings. Dissatisfaction with the amount of air motion is very common, with too little air movement cited far more commonly than too much air movement. Workers were also surveyed in a detailed two-season study of a single naturally ventilated building. About one-half the building’s population wanted more air movement and only 4% wanted less. This same ratio applied when the air movement in workspaces was higher than 0.2 m/s, the de facto draft limit in the current ASHRAE and ISO thermal environment standards. Preference for “less air motion” exceeded that for “more” only at thermal sensations of −2 (cool) or colder. These results raise questions about the consequences of the ASHRAE and ISO standards’ restrictions on air movement, especially for neutral and warm conditions.     

Climate Impacts on Extreme Energy Consumption of Different Types of Buildings

Exploring changes of building energy consumption and its relationships with climate can provide basis for energy-saving and carbon emission reduction. Heating and cooling energy consumption of different types of buildings during 1981-2010 in Tianjin city, was simulated by using TRNSYS software. Daily or hourly extreme energy consumption was determined by percentile methods, and the climate impact on extreme energy consumption was analyzed. The results showed that days of extreme heating consumption showed apparent decrease during the recent 30 years for residential and large venue buildings, whereas days of extreme cooling consumption increased in large venue building. No significant variations were found for the days of extreme energy consumption for commercial building, although a decreasing trend in extreme heating energy consumption. Daily extreme energy consumption for large venue building had no relationship with climate parameters, whereas extreme energy consumption for commercial and residential buildings was related to various climate parameters. Further multiple regression analysis suggested heating energy consumption for commercial building was affected by maximum temperature, dry bulb temperature, solar radiation and minimum temperature, which together can explain 71.5 % of the variation of the daily extreme heating energy consumption. The daily extreme cooling energy consumption for commercial building was only related to the wet bulb temperature (R²= 0.382). The daily extreme heating energy consumption for residential building was affected by 4 climate parameters, but the dry bulb temperature had the main impact. The impacts of climate on hourly extreme heating energy consumption has a 1-3 hour delay in all three types of buildings, but no delay was found in the impacts of climate on hourly extreme cooling energy consumption for the selected buildings.     

Prevention of abnormal pulmonary mechanics in the postmortem guinea pig lung

Severe postmortem bronchoconstriction has been shown previously in guinea pig lungs and linked to pulmonary blood loss during exsanguination (Lai et al., J. Appl. Physiol. 56: 308-314, 1984). To reexamine this phenomenon we measured postmortem airway function in anesthetized open-chest guinea pigs after sudden circulatory arrest. Animals were divided into 4 groups of 10 and ventilated for 15 min postmortem with different gases: 1) room air, 2) conditioned air, 3) dry 5% CO2-21% O2-74% N2, and 4) conditioned 5% CO2-21% O2-74% N2. In room air-ventilated lungs there was a 50% decrease in dynamic compliance (Cdyn) by 15 min and marked gas trapping compared with control lungs. Conditioning the room air did not attenuate these changes, but when 5% CO2 was added to the conditioned postmortem inspirate, gas trapping was eliminated and the fall in Cdyn was almost abolished. Ventilation with a dry 5% CO2 gas mixture at room temperature resulted in a 31% fall in Cdyn at 15 min but no gas trapping. We conclude that marked abnormalities of airway function occur postmortem in room air-ventilated guinea pig lungs in the absence of pulmonary blood loss. The changes are mainly due to airway hypocarbia, a known cause of bronchoconstriction, but a reduction in Cdyn can also occur if there is marked airway cooling and drying. Acute postmortem airway dysfunction can be prevented in the guinea pig by maintaining normal airway gas composition.     

Effect of fee-for-service air-conditioning management in balancing thermal comfort and energy usage

Balancing thermal comfort with the requirement of energy conservation presents a challenge in hot and humid areas where air-conditioning (AC) is frequently used in cooling indoor air. A field survey was conducted in Taiwan to demonstrate the adaptive behaviors of occupants in relation to the use of fans and AC in a school building employing mixed-mode ventilation where AC use was managed under a fee-for-service mechanism. The patterns of using windows, fans, and AC as well as the perceptions of students toward the thermal environment were examined. The results of thermal perception evaluation in relation to the indoor thermal conditions were compared to the levels of thermal comfort predicted by the adaptive models described in the American Society of Heating, Refrigerating, and Air-Conditioning Engineers Standard 55 and EN 15251 and to that of a local model for evaluating thermal adaption in naturally ventilated buildings. A thermal comfort-driven adaptive behavior model was established to illustrate the probability of fans/AC use at specific temperature and compared to the temperature threshold approach to illustrate the potential energy saving the fee-for-service mechanism provided. The findings of this study may be applied as a reference for regulating the operation of AC in school buildings of subtropical regions.     

Sickness absence among municipal workers in a Brazilian municipality: a secondary data analysis

Background

Sickness absence, work disability associated with illness or injury, is a major public health problem worldwide. Some studies have investigated determinants of sickness absence among workers with shorter job tenure, but have only focused on certain diagnostic groups. Although it is well established that job tenure has an inverse relationship with work injury rate, less is known about its association with sickness absence for other disorders. Therefore, this study aimed to investigate the risk factors for incidence and duration of sickness absence according to diagnosis over a 7-year period. A dynamic cohort consisting of all permanent civil servants hired from 2005 to 2011 by the Goiania municipality-Brazil. Data of certified sickness absences longer than 3 days were analyzed. The incidence density was calculated per 1000 person-years in each ICD-10 category. The association between sickness absence and socio-demographic and occupational characteristics was examined using negative binomial regression models.

Results

18,450 workers, mean age of 32 years, accumulated 14,909 episodes of sickness absence. Overall, the incidence density was 234.6 episodes per 1000 person years. Diagnostic groups with the highest incidence density of sickness absences were injuries (49.1), musculoskeletal disorders (31.3) and mental disorders (29.2). Factors predicting any sickness absence were female gender, older age, low education, being a health professional, multiple jobs and full-time employment. Mental health disorders were more common among education professionals, musculoskeletal disorders among blue collar workers and injuries among inspection workers. Prolonged time on sick leave was associated with male gender, older age groups, low education and income, blue-collar workers, more than one job contract and full time employment.

Conclusions

These findings demonstrate a substantial sickness absentee burden and they provide relevant information for targeting prevention and health promotion policies to the most vulnerable occupational groups.

     

Association of Sickness Absence with Poor Sleep and Depressive Symptoms in Shift Workers

A cross-sectional study was conducted to evaluate the contribution of daily sleep habits and depressive symptoms to sickness absences of shift workers. A self-administered questionnaire that solicited answers about sleep, symptoms of depression, sickness absence, diseases/injuries, and lifestyle factors was submitted to a sample of 522 rotating shift workers between the ages of 18–59 (mean 27) yrs of an electric equipment manufacturing company. The seven features of sleep queried were daily hours of sleep, time to fall asleep, awakening during sleep, early morning awakening, sleep well at night, sufficiency of sleep, and excessive daytime sleepiness at work. The responses were assessed over the subject's previous 1-yr period. Each sleep feature, except daily sleeping hours, was dichotomized by the following responses: (1) taking more than 30 min to fall asleep (difficulty initiating sleep; DIS), (2) awakening during sleep almost every day (difficulty maintaining sleep; DMS), (3) early morning awakening almost every day (EMA), (4) sleeping very poorly or not so well at night, (5) definite or somewhat insufficient nightly sleep, and (6) excessive daytime sleepiness at work almost every day (EDS). Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression (CES-D) scale. Sickness absence was calculated by asking subjects “How many days in total have you been absent from work due to sickness, including paid vacation, in the last 1-yr period?” The responses were divided into three groups that included no (0 days) sickness absences (reference group, n = 235 subjects), 1 to 4 days (short-term, n = 199 subjects), and 5 days or more (long-term, n = 88 subjects). Compared to the prevalence of sleep features of the reference group, workers with short-term absence showed a significantly higher prevalence of EMA with an odds ratio (OR) of 5.3, 95% confidence interval (CI) 1.3–22.0. Long-term absence was significantly associated with DMS (OR = 2.1, 95%CI 1.0–4.6), EMA (OR = 5.6, 95%CI 1.0–28.7), sleeping poorly at night (OR = 2.6, 95%CI 1.4–5.0), and high depressive symptoms (OR = 2.0, 95%CI 1.0–3.7) according to the CES-D score of ≥16, after adjusting for multiple confounding variables. These data point to an association between both the parameters of poor sleep and symptoms of deep depression when self-reported sickness absence is frequent. The association is particularly strong with long-term absence in male shift workers.     

Mathematical model of the distribution of small negative ions in air conditioned rooms

The distribution of small negative ions with mobility k_r=0.5+ (cm²/Vs) in an air conditioned room is presented. The air was ionized by an ion generator, which was placed at the outlet of the air duct. The measurements were made at 100 different locations in the room. It was established, that the main factors in the distribution of ions were the coordinates of points in the room space. Regression analysis method was applied to determine optimal estimate of identified static characteristics of ions distribution. The main purpose of this research was to obtain data for the correct placement of ion generators in air conditioned or ventilated rooms.     

Bronchoconstriction elicited by isocapnic hyperpnea in guinea pigs

We demonstrated spontaneous self-limited bronchoconstriction after eucapnic dry gas hyperpnea in 22 anesthetized, mechanically ventilated guinea pigs pretreated with propranolol (1 mg/kg iv). Eucapnic hyperpnea "challenges" of room temperature dry or humidified gas (5% CO2-95% O2) were performed by mechanically ventilating animals (150 breaths/min, 3-6 ml tidal volume) for 5 min. During a "recovery" period after hyperpnea, animals were returned to standard ventilation conditions (6 ml/kg, 60 breaths/min, 50% O2 in air, fully saturated at room temperature). After dry gas hyperpnea (5 ml, 150 breaths/min), respiratory system resistance (Rrs) increased in the recovery period by 7.7-fold and dynamic compliance (Cdyn) decreased by 79.7%; changes were maximal at approximately 3 min posthyperpnea and spontaneously returned to base line in 10-40 min. This response was markedly attenuated by humidification of inspired air. Four consecutive identical dry air challenges resulted in similar posthyperpnea responses in four animals. Increasing the minute ventilation during hyperpnea (by varying tidal volume from 3 to 6 ml) caused increased bronchoconstriction in a dose-dependent fashion in six animals. Neither vagotomy nor atropine altered the airway response to dry gas hyperpnea. We conclude that dry gas hyperpnea in anesthetized guinea pigs results in a bronchoconstrictor response that shares five similar features with hyperpnea-induced bronchoconstriction in human asthma: 1) time course of onset and spontaneous resolution, 2) diminution with humidification of inspired gas, 3) reproducibility on consecutive identical challenges, 4) stimulus-response relationship with minute ventilation during hyperpnea, and 5) independence of parasympathetic neurotransmission.     

Airway Symptoms and Biological Markers in Nasal Lavage Fluid in Subjects Exposed to Metalworking Fluids

Backgrounds

Occurrence of airway irritation among industrial metal workers was investigated. The aims were to study the association between exposures from water-based metal working fluids (MWF) and the health outcome among the personnel, to assess potential effects on the proteome in nasal mucous membranes, and evaluate preventive actions.

Methods

The prevalence of airway symptoms related to work were examined among 271 metalworkers exposed to MWF and 24 metal workers not exposed to MWF at the same factory. At the same time, air levels of potentially harmful substances (oil mist, morpholine, monoethanolamine, formaldehyde) generated from MWF was measured. Nasal lavage fluid was collected from 13 workers and 15 controls and protein profiles were determined by a proteomic approach.

Results

Airway symptoms were reported in 39% of the workers exposed to MWF although the measured levels of MWF substances in the work place air were low. Highest prevalence was found among workers handling the MWF machines but also those working in the same hall were affected. Improvement of the ventilation to reduce MWF exposure lowered the prevalence of airway problems. Protein profiling showed significantly higher levels of S100-A9 and lower levels of SPLUNC1, cystatin SN, Ig J and β2-microglobulin among workers with airway symptoms.

Conclusions

This study confirms that upper airway symptoms among metal workers are a common problem and despite low levels of MWF-generated substances, effects on airway immune proteins are found. Further studies to clarify the role of specific MWF components in connection to airway inflammation and the identified biological markers are warranted.     

Dynamics of Airborne Fungal Populations in a Large Office Building

The increasing concern with bioaerosols in large office buildings prompted this prospective study of airborne fungal concentrations in a newly constructed building on the Gulf coast. We collected volumetric culture plate air samples on 14 occasions over the 18-month period immediately following building occupancy. On each sampling occasion, we collected duplicate samples from three sites on three floors of this six-story building, and an outdoor sample. Fungal concentrations indoors were consistently below those outdoors, and no sample clearly indicated fungal contamination in the building, although visible growth appeared in the ventilation system during the course of the study. We conclude that modern mechanically ventilated buildings prevent the intrusion of most of the outdoor fungal aerosol, and that even relatively extensive air sampling protocols may not sufficiently document the microbial status of buildings. Received: 7 April 1999 / Accepted: 2 August 1999     

Sickness absence and shift work among Japanese factory workers

To investigate the effect of shift work on long-term sickness absence (more than 7 calendar days), an 8-year follow-up study was carried out in a factory in Japan. The participants were male employees aged 18-54 years who were engaged in manufacturing sites. Shift patterns were classified by the number of non-daytime working days during the previous one-year. The causes of sickness absence were classified into three groups, 1) causes except injury, diseases of the musculoskeletal system and connective tissue, 2) injury, 3) diseases of the musculoskeletal system and connective tissue. The analysis of long-term sickness absences was based on the first occurrence. The age-adjusted incidence of sickness absence among shift workers who were on non-daytime shifts more than two-thirds of working days during the previous one year was significantly higher than that among other workers. After adjusting for confounding factors, a significant high risk still existed for this group of workers taking sickness absence for all causes and causes except for injury and the musculoskletal disorders. These findings suggest that shift workers who are engaged on a particular shift schedule are more likely to take leave due to sickness.     

O2 radicals mediate reperfusion lung injury in ischemic O2-ventilated canine pulmonary lobe

This study was undertaken to determine whether lung injury after a period of ischemia reperfusion is caused by O2 ventilation during ischemia and whether this injury is mediated by reactive O2 metabolites. Isolated canine left lower pulmonary lobes were subjected to room temperature ischemia for 6 h while being ventilated with either 100% O2, room air, or 100% N2. After the ischemic period, all lobes were perfused with autologous blood and ventilated with 100% O2 for an additional 4 h. In lobes ventilated with 100% O2 during the ischemic period, massive weight gain (228%) occurred 4 h after reperfusion. A marked increase in pulmonary shunt was noted. Lobes ventilated with room air behaved similarly. In contrast, lobes ventilated with 100% N2 gained significantly less weight (54%) and did not manifest any increase in pulmonary shunt. When lobes ventilated with 100% O2 or room air were pretreated with superoxide dismutase (SOD), the injury was significantly reduced. Pressure-volume deflation study of lobes, after ischemia only, demonstrated that ventilation with 100% O2 and with 100% N2 both equally decreased pulmonary compliance. We conclude that lung ischemia-reperfusion injury is related to O2 ventilation during ischemia and that injury can be prevented by administration of SOD or ventilation with 100% N2. This suggests that the injury is related to O2 metabolites produced during O2 ventilation in the absence of the circulation.     

The Prognostic Value of the Work Ability Index for Sickness Absence among Office Workers

BackgroundThe work ability index (WAI) is a frequently used tool in occupational health to identify workers at risk for a reduced work performance and for work-related disability. However, information about the prognostic value of the WAI to identify workers at risk for sickness absence is scarce.ObjectivesTo investigate the prognostic value of the WAI for sickness absence, and whether the discriminative ability differs across demographic subgroups.MethodsAt baseline, the WAI (score 7-49) was assessed among 1,331 office workers from a Dutch financial service company. Sickness absence was registered during 12-months follow-up and categorised as 0 days, 0<days<5, 5≤days<15, and ≥15 days in one year. Associations between WAI and sickness absence were estimated by multinomial regression analyses. Discriminative ability of the WAI was assessed by the Area Under the Curve (AUC) and Ordinal c-index (ORC). Test characteristics were determined for dichotomised outcomes. Additional analyses were performed for separate WAI dimensions, and subgroup analyses for demographic groups.ResultsA lower WAI was associated with sickness absence (≥15 days vs. 0 days: per point lower WAI score OR=1.27; 95%CI 1.21-1.33). The WAI showed reasonable ability to discriminate between categories of sickness absence (ORC=0.65; 95%CI 0.63-0.68). Highest discrimination was found for comparing workers with ≥15 sick days with 0 sick days (AUC=0.77) or with 1-5 sick days (AUC=0.69). At the cut-off for poor work ability (WAI≤27) the sensitivity to identify workers at risk for ≥15 sick days was 7.5%, the specificity 99.6%, and the positive predictive value 82%. The performance was similar across demographic subgroups.ConclusionsThe WAI could be used to identify workers at high risk for prolonged sickness absence. However, due to low sensitivity many workers will be missed. Hence, additional factors are required to better identify workers at highest risk.