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Occup Environ Med. 2007 December; 64(12): e26.
PMCID: PMC2095358


127 Respiratory sequelae following a fire at a chemical waste depot

F. E. Greven1, F. Duijm1, H. A. M. Kerstjens2, D. Heederik3, F. E. Greven1. 1Municipal Health Service; 2Department of Pulmonology, University Medical Center, Groningen; 3IRAS Division of Environmental Epidemiology, Utrecht University

ObjectivesIn May 2000 480 tons of chemical waste were burnt at a hazardous waste disposal site and dispersed smoke and other combustion products over a large area to the west of the town of Drachten, The Netherlands. The objectives of this study are: first, to evaluate whether reactive airways dysfunction syndrome (RADS) occurs among the examined subjects; second, to evaluate if the RADS can be attributed to the ATF fire.

MethodsBecause there was still concern among some of the public and workers involved in the incident, an aetiological study was undertaken in 2006. Because the results of a previously self‐administered questionnaire demonstrated that RADS was a possible sequela of exposure to the smoke, the study focused on RADS and started with an interview by telephone using a standardised questionnaire. This was followed by a medical survey of 25 possible cases and 50 randomly sampled controls. Subjects meeting predefined criteria enrolled in a medical examination that consisted of spirometry, histamine challenge tests, laboratory tests and a chest x ray. In a subsample induced sputum has been assessed. Exposure was considered high if the distance to the fire was up to 100 m, intermediate from 100 to 1000 m and low beyond 1000 m.

ResultsPreliminary results show an odds ratio (95% CI) of 4.3 (1.5 to 11.8) for cases and controls of the interview. This odds ratio increased to 14.0 (2.8 to 70.8) when analysis was restricted to cases of lung physician diagnosis of possible RADS.

ConclusionIndications were found of an association between exposure and respiratory symptoms indicative of RADS. The likelihood of selection and other biases will be discussed and balanced against the results of the medical survey.

Key wordsrespiratory effects; combustion products; police officers

128 A diagnostic model to predict the probability of sensitisation to wheat allergens among bakers

E. Meijer1, E. Suarthana1, K. G. M. Moons2, J. de Monchy3, T. Meijster1, D. Heederik1. 1Institute for Risk Assessment Sciences, Utrecht University; 2Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht; 3Department of Allergology, University Medical Center, Groningen

ObjectivesIn The Netherlands, the baking and flour producing industries agreed on developing a health surveillance system to reduce the number of occupational allergic diseases and improve their prognosis by early detection of those at high risk. The study aimed to develop and validate a diagnostic model by using questionnaire items and exposure information to predict the probability of sensitisation to wheat allergens. The model should be used as a screening instrument to detect workers with different risks of being sensitised.

MethodsThe diagnostic model was developed with the results from a cross‐sectional study in 890 Dutch bakers. Class II IgE to wheat was used as the reference standard. Diagnostic accuracy of the developed model was evaluated and bootstrapping was used to assess internal validity. External validation was conducted in 391 other bakers.

ResultsThe diagnostic model consisted of five questionnaire items (respiratory symptoms, history of asthma, a history of allergy, hay fever, work‐related upper respiratory symptoms) and two exposure proxies (working years, and being a traditional baker). The model showed good calibration (p = 0.9) and discriminative ability (AUC 0.77; 95% CI 0.72 to 0.82). From the bootstrapping procedure a shrinkage factor of 0.86 was calculated, resulting in a corrected AUC of 0.76. External validation showed good calibration (p = 0.9). External validation in traditional bakers showed an AUC of 0.83 (0.77 to 0.90), whereas in industrial bakers an AUC of 0.67 (0.58 to 0.77) was found.

ConclusionThis easy‐to‐use diagnostic model to predict the likelihood of being sensitised to wheat allergens showed good diagnostic accuracy and good external validity. It can be an efficient and effective instrument to detect sensitised bakers in an early phase and can lower the costs by investigating only those bakery workers at high risk of being sensitised.

Key wordsdiagnostic model; wheat sensitisation; external validity

129 Validity of silicosis early detection and its influence on risk estimation in epidemiology

Y. Sun. BGIA ‐ Hauptverband der gewerblichen Berufsgenossenschaften

ObjectivesEarly detection and diagnosis of silicosis among dust exposed workers is based mainly on the presence of rounded opacities on radiographs. It is thus important to examine how reliable the radiographic findings are in comparison to pathological findings.

MethodsA systematic literature search via Medline was conducted. The validity of silicosis detection and its influence on risk estimation in epidemiology were evaluated in a sensitivity analysis.

ResultsFour studies on comparison between radiographic and pathological findings of silicosis were identified. The sensitivity of radiographic diagnosis of silicosis (ILO 1/1) varied between 39% and 71%, and specificity between 60% and 99%. Under the realistic assumption of a silicosis prevalence of between 2% and 8% in dust exposed workers, 23% to 56% of silicosis identified may be falsely diagnosed. The sensitivity analysis indicates that invalid diagnostics alone may lead to the finding of an increased risk of lung cancer among patients with silicosis. It may also lead to findings of 1% to 4% of radiographic silicosis even when there is no case of silicosis. However, the risk of silicosis could also be underestimated if the prevalence of silicosis exceeds 10%.

ConclusionEpidemiological studies based on patients with silicosis should be interpreted with caution.

Key wordssilicosis diagnosis; validity; risk estimation

130 Dust exposure in the Alberta sawmill study

M. Yamanaka1, T. L. Guidotti2, N. Koehncke3. 1WorkSafeBC; 2George Washington University; 3University of Saskatchewan

ObjectivesWe evaluated the level of softwood dust exposure in Alberta sawmills in 1995 as part of the Alberta Sawmill Study. Noise data from the study have already been published.

MethodsFrom nine Alberta sawmills, 210 wood dust samples (inhalable) were collected with personal monitors using IOM (Institute of Occupational Medicine) sampler devices. Nine mills were pooled and 13 jobs were combined into four occupational groups.

ResultsApproximately 9% of samples exceeded the then‐proposed ACGIH TLV (American Conference of Governmental Industrial Hygienists Threshold Limit Value) of 5 mg/m3 TWA (time weighted average) for inhalable wood dust, which has since been revised to 1 mg/m3. There was a significant statistical difference (p<0.001) between the median IPM dust levels of the four occupational groups. “Clean‐up” workers (a subset of sawmill workers) had statistically significant higher mean inhalable dust levels, with 32% of samples for “clean‐up” workers exceeding the proposed ACGIH TLV. The clean‐up occupational group, which has the fewest number of samples collected, had the highest recorded dust levels (34.6 mg/m3), and the highest percentage (32%; 95% CI 14.8% to 49.4%) of IPM samples above the proposed ACGIH NIC TLV of 5 mg/m3. The clean‐up group had the highest geometric mean (3.5 mg/m3), arithmetic mean (5.7 mg/m3) and median (3.1 mg/m3) dust levels, followed by the maintenance, planermill, and sawmill occupational groups.

ConclusionWith particular attention to the “clean‐up” workers, sawmills were advised to review and update their wood dust control methods to improve engineering controls, administrative controls and personal protective equipment. Local exhaust controls, maintenance of equipment (blades, belts, motors and guards) and enclosures may reduce dust emissions. Job rotation during the day is a form of administrative control and has the effect of decreasing the exposure time to wood dust (assuming that the worker is rotated to an area of less dust). When engineering methods and administrative controls are not feasible or practical, personal protective equipment can be used.

Key wordswood dust; sawmills; occupational category

131 Exposure–effect and exposure–response relationships between indium exposure and interstitial lung damage

M. Nakano1, Y. Kikuchi1, A. Tanaka2, M. Hirata2, Y. Sano1, N. Yoshioka1, Y. Nishiwaki1, T. Takebayashi1, K. Omae1, M. Nakano1. 1Keio University, School of Medicine, Tokyo, Japan; 2Kyushu University, Graduate School of Medical Sciences, Fukuoka, Japan

ObjectivesFive case reports and two epidemiological studies revealed that exposure to hardly soluble indium compound dusts caused interstitial lung injury. To assess exposure–effect and exposure–response relationships between indium exposure and effects on the lungs, we designed a baseline survey in 14 indium plants during December 2003 through December 2006.

MethodsStudy subjects were 488 indium‐exposed, 125 ex‐exposed and 182 non‐exposed workers. Mean age of exposed, ex‐exposed and non‐exposed workers was 36.6, 39.1 and 41.4 years. Indium exposure duration (month) of exposed and ex‐exposed workers was 0.3–488 (median 58.0) and 1.0–252 (60.4). KL‐6, SP‐D, SP‐A, WBC, CRP and spirometry were examined for assessing the effects on lung interstitium. Because indium concentrations in the workplace were not available, we adopted indium in serum (In‐S) as an exposure index. Some potential confounders were also checked.

Results Thegeometric means (GM) of In‐S (ng/ml) in non‐exposed, ex‐exposed and exposed workers were 0.28, 1.28 and 1.30. The GM of KL‐6 (U/ml) was 232, 295 (p<0.05 compared to non‐exposed) and 343 (p<0.05), and that of SP‐D (ng/ml) was 49.3, 51.1 and 58.1 (p<0.05). Other effect indices showed no differences among the three groups. When the exposed workers were classified into eight groups by In‐S (<1, 1–2.9, 3–4.9, 5–9.9, 10–19.9, 20–29.9, 30–49.9, [gt-or-equal, slanted]50 ng/ml), the GM of KL‐6 in each group was 222, 266, 339, 450, 512, 765, 931 and 1435, and that of SP‐D was 41.1, 62.0, 56.1, 69.1, 78.9, 127.5, 125.8 and 151.0. The prevalence (%) of KL‐6 exceeding the reference value (<500) in each group was 3.4, 5.6, 18.9, 35.7, 49.1, 78.9, 81.0 and 100, and that of SP‐D (<110) was 5.4, 14.0, 16.1, 22.0, 32.4, 54.5, 76.9 and 76.9. Compared to the lowest In‐S group (<1), KL‐6 and SP‐D were significantly larger in [gt-or-equal, slanted]3 groups and in [gt-or-equal, slanted]1 groups, and the prevalence of KL‐6 and SP‐D was significantly higher in [gt-or-equal, slanted]3 groups and in [gt-or-equal, slanted]5 groups, respectively.

ConclusionExposure to indium dusts is a risk for KL‐6 and SP‐D increase indicating interstitial lung damage. Sharp exposure–effect and exposure–prevalence relationships were observed. A follow‐up study is necessary to clarify the exposure–incidence relationship.

Key wordsindium; interstitial lung damage; exposure–response relationship

132 An investigation of respiratory and occupational dermatitis symptoms in relation to drilling fluid exposures in Nova Scotian offshore workers

K. A. Zinszer1, V. Gagne2, J. R. Guernsey1. 1Dalhousie University; 2Duke Energy

ObjectivesOffshore petroleum drilling requires the use of complex lubricants. Exposure to drilling fluids can occur through dermal contact or inhalation of mists, vapours, or splashes during certain operations. The health effects of exposure to these fluids have not been widely studied. This study aimed to further knowledge about health effects associated with such exposures in offshore conditions.

MethodsA cross‐sectional observational epidemiological study of 111 drill rig workers currently employed on two rigs operating off the east coast of Canada was conducted. A validated, self‐administered, questionnaire derived from the Haines and Oudyk metalworking fluid survey was used to collect health, exposure and PPE information between December 2003 and February 2004. Descriptive statistical and unconditional logistic regression analyses were conducted using SAS.

ResultsParticipants reported having worked offshore for a mean of 10.2 years. 96% were male. Overall mean age was 39.7 years. 33% were non‐smokers and 31% were current smokers. 73% reported they had regular exposure to drilling fluids (67% direct to clothes and 62% direct to hands). Barrier creams were used by 47% and respirators were used by 40%. Nasal irritation, usual cough, usual phlegm were more frequently reported by exposed versus non‐exposed workers. These symptoms were also more commonly experienced by those working on the drilling floor and marine deck than in other areas. Asthma prevalence was reportedly higher in the currently unexposed versus exposed workers. Usual cough was significantly associated with duration of total exposure, and mud tank and shaker exposures after adjustment for rig, smoking status and atopy. Barrier cream use was protective against developing dry and itchy skin.

ConclusionThis investigation is the first known cross‐sectional investigation of respiratory and dermatological symptoms and drilling fluids exposure in the offshore petrochemical industry. While preliminary, findings suggest that those exposed were at higher risk for nasopharyngeal, respiratory and dermatological symptoms after adjustment for smoking and atopy status. Nevertheless, the symptom prevalence rates observed in this study are lower than those reported for metalworking fluid studies. Challenges with gaining access to the study population may have influenced recruitment and survey responses.

Key wordsdrilling fluids exposure; occupational respiratory disease; occupational dermatitis

133 Early working‐life changes in lung function as predictors of physician visits for respiratory health later in life

C. E. Peters, P. A. Demers, S. M. Kennedy. University of British Columbia

ObjectivesSurveillance programs that include spirometry screening are recommended to help prevent occupational asthma. However, the effectiveness of these measures as predictors of respiratory disease has been less well studied. Our objective was to examine early career changes in simple lung function (FEV1) and bronchial responsiveness (BR) as predictors of respiratory‐related physician visits later in life.

MethodsIn 1988 we enrolled trades' apprentices into a prospective study; first follow‐up occurred 2 years later. The cohort was linked to a health care utilisation database with diagnostic codes for physician visits from 1991 to 2004. We devised an asthma case definition of [gt-or-equal, slanted]2 visits coded ICD‐9 493 in a sliding 365‐day window. We also defined “other respiratory disease” (ORD) cases as those who had [gt-or-equal, slanted]3 visits in 1 year (ICD‐9 codes 466, 490–492, 496, 786). We used logistic regression to examine the association with early rapid loss in FEV1 or rapid increase in BR and the likelihood of becoming a case. We also used log‐linear models (negative binomial distribution) to examine predictors of physician visit rates for asthma or ORD visits.

Results281 of 356 subjects were available for this analysis (complete data at baseline, 2‐year follow‐up, [gt-or-equal, slanted]4 years of health care utilisation data). Sixteen met the asthma case definition and 20 met the ORD case definition. Baseline BR was a risk factor for meeting the ORD case definition (OR 3.2, 95% CI 1.0 to 10.4), as well as an increased visit rate for asthma (OR 4.5, 95% CI 1.3 to 14.9). Experiencing a rapid increase in BR over the first 2 years of apprenticeship was strongly related to becoming an asthma case during follow‐up (OR 8.2, 95% CI 2.4 to 28.5) and to increased physician visit rate both for asthma (OR 6.5, 95% CI 1.7 to 24.9) and ORD (OR 2.2, 95% CI 1.3 to 3.8). No FEV1 measures (baseline or rapid change) were important predictors of respiratory‐related physician visits.

ConclusionAn early‐career rapid increase in BR was a strong risk factor for physician visits for both asthma and ORD diagnoses later in life. Rapid decline in simple lung function measures (ie, FEV1), at least over the short term, was not a useful predictor in this study.

Key wordsoccupational lung disease; asthma; apprentices

134 Respiratory symptoms and pulmonary function amongst workers in a rubber wood sawmill factory in Thailand

N. Chaiear1, J. Ngoencharee1, N. Saejiw2. 1Unit of Occupational Medicine, Community Medicine Department, Faculty of Medicine, Khon Kaen University; 2Institute of Allied Health Science and Public Health, Walailak University, Nakhon Si Thammarat

Objectives(1) To study the prevalence of respiratory symptoms amongst workers in the rubber wood sawmill with different exposure intensities. (2) To study the prevalence of the obstructive form of pulmonary function amongst workers in the rubber wood sawmill with the different exposure intensities.

MethodsThis study is a part of a cross‐sectional study on wood dust exposure and respiratory health effects in rubber wood sawmill workers. A large sawmill located in Nakhon Sri Thammarat, Southern Thailand was selected for this study. The entire group of 340 workers was invited to enter the study including office workers. The questionnaire was developed based on the European work‐related respiratory asthma and bronchitis questionnaire. A cross‐shift spirometry was performed in all volunteers. Exposure assessment for rubber wood dust was performed in all job categories by using the personal sampling technique and exposure intensities were classified as high, moderate and low. Descriptive statistics and 95% confidence intervals were used to present the data.

Results82.1% (279/340) of the workers participated in the questionnaire interviews and pulmonary function tests. The mean age of the studied population was 36.7 years. There were more female (78%) than male workers. The mean duration of employment in this factory was 6.21 years. The most common work‐related respiratory symptoms were eye irritation (56.6%, 95% CI 50.8% to 62.5%) followed by dyspnea (37.6%, 95% CI 31.9% to 43.2%). Work‐related upper respiratory symptoms (eye irritation) were higher in the high exposure group, but no such difference was found between the medium and low exposure groups. However, there seemed to be no relationship between exposure intensities and work‐related lower respiratory symptoms (wheezing and dyspnea) in this study. However, since the pulmonary function tests are still being performed in those workers, the results cannot be shown in this abstract. For the exposure assessment, a large percentage of dust belonged to the thoracic fractions.

ConclusionThe workers exposed to rubber wood dust presented with work‐related upper respiratory symptoms more than with lower respiratory symptoms. Exposure intensities may not influence work‐related symptoms but rather the particle size may play an important role in influencing work‐related respiratory symptoms.

Key wordswork‐related respiratory symptoms; occupational exposure; wood dust

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