Cumulative Occupational Exposure Assessment for Mineral Dust Using Finnish Job-Exposure Matrix ( FINJEM )

Mineral dust is classified by International Agency for Research on Cancer (IARC) as carcinogenic to humans because it is thought to cause lung cancer. Studies show strong associations between asbestos or other mineral dusts (OMD) exposure and respiratory health risk. The aim of the study was to examine the relationship between airflow obstruction (AFO) and cumulative occupational exposure to mineral dust, using the Finnish Job Exposure Matrix (FINJEM), in a population historically at high risk of lung cancer. The quantitative estimation of cumulative exposure to asbestos and OMD were calculated using the FINJEM from the data obtained at the baseline assessment in the Wythenshawe Respiratory Health Study (WRHS). The study was a population-based observational cohort study comprises all patients, aged 5075, registered with a General Practitioner (GP) practices in Wythenshawe District, Manchester. Among 257 study subjects who were assessed at baseline, 165 (64.2%) reported that they have been exposed to any occupational hazards, 56 (21.8% subcohort exposed) to asbestos and 42 (16.3% subcohort exposed) to OMD. There was a significant positive correlation between occupational exposure to OMD (Pearson correlation coefficient, r = 0.47, p = 0.01). They were 5 times higher risk to get airflow obstruction among those who have been exposed to low level of asbestos compared to non-exposed, after adjustment for gender, age and smoking (adjusted Odds Ratio (aOR) = 5.76, 95% Confidence Interval (CI) = 1.37 – 24.1). However, no significant association was found between level of exposure to OMD and airflow obstruction. It is suggested that workplace exposure to mineral dusts is sufficient to produce measurable airflow obstruction evidence of occupational respiratory ill-health. The findings from this study supports the FINJEM could be used in epidemiological study and a potential cost-effective exposure assessment particularly in examining the relationship between cumulative occupational exposures with respiratory ill-health. _____________________________________________________________________________ December 2014, vol 1, N . 2 : 47-56 Journal of Occupational Safety and Health December 2014, vol 11, No. 2 48 of exposure and the prevalence or airflow obstruction (AFO) among the studied population may contribute to heterogeneity in exposure-response relationship between studies. Large potential of misclassification of biologically significant exposure hinder detection of true elevated exposure-response relationships. The frequently lacking information on smoking habits in workers cohorts may lead to inaccurate risk estimates because of the prevailing role of smoking in respiratory ill-health patients8. Occupational exposure assessment in populationbased study gives a major challenge due to the wide range of occupations in different types of industries involved. Previous studies investigated the association between occupational exposures and risk of developing respiratory ill-health which includes COPD and lung cancer proved to show the links by using the general population Job-Exposure Matrix (JEM)5,9,10. The Finnish Job-Exposure Matrix (FINJEM) is a tool yielding quantitative estimation of cumulative occupational exposure which represents a potentially cost-effective exposure assessment tool11. Moreover, it is applied since the previous exposure assessment at individual’s level was not available in the study population. This paper is deemed to justify further analysis using the FINJEMbased method to study relationship between mineral dust exposure and airflow obstruction thus may assist in targeting a high risk population for lung cancer screening in the primary care setting. The aim of the study was to examine the relationship between airflow obstruction (AFO) and cumulative occupational exposure to mineral dust, using the Finnish Job Exposure Matrix (FINJEM), in a population historically at high risk of lung cancer. To achieve these aims, the estimation of exposure to asbestos and other mineral dusts (OMD) were calculated using the Finnish Job-Exposure Matrix (FINJEM) from the data obtained at the baseline assessment in the Wythenshawe Respiratory Health Study (WRHS). The extent of exposure assessment thus looking at the association between airflow obstruction and occupational exposure were explored. Methodology Study population Participants were part of the Wythenshawe Respiratory Health Study (WRHS) 2010, which looked for an early detection of respiratory ill-health in high risk populations. WRHS was a population-based observational cohort study comprises all patients, aged 5075, registered with a GP practices in Wythenshawe District, Manchester. Data on life-time occupational history was captured from the job questionnaire interviewed at the baseline study assessment. Occupation was initially coded according to the Standard Occupational Classification (2000)33, using self-reported information on job title, type of work, type of company, period of employment and type of exposure. Exposure estimates were calculated based on occupation-specific estimates and the distribution of occupations within industries. FINJEM was used to assign exposure information to individual workers. For each year of the total occupational history of each individual in the dataset, exposure was estimated using the time specific exposure information for occupational groups according to code of occupation (oCODE)12,13,14. All the information of every subjects were coded and calculated for the average exposure estimation in the excel database constructed for this study before transferred to SPSS database for descriptive and statistical tests analysis. Statistical Analysis Those workers exposed to inorganic mineral dust were analysed to look at the quantitative estimation of cumulative exposure of each subjects. Log transformed using the natural log function was carried out to create a new variable to reduce skewness for further analysis, for both quantitative data on cumulative exposure to asbestos and OMD. Pearson Chi-squared tests were used to test an association between different level of occupational exposure and outcome measure, airflow obstruction (AFO). Linear regression analysis was performed to assess the relationship between the forced expiratory volume in one second (FEV1 % predicted) and log-transformed cumulative occupational exposure to asbestos and OMD. Multivariate analysis of airflow obstruction and the occupational exposure with potential confounders were then carried out using multiple linear regression (MLR) and the results are presented as Pearson correlation coefficient, r and the overall p -value. Statistical significance was assumed at p < 0.05. Results Among 257 study subjects who were seen and been interviewed at baseline, 165 (64.2%) reported that they have been exposed to any occupational hazards with different type of exposure to cancer-causing agents, namely dust, mist and/or fumes, mineral and/or chemicals and ionizing radiation or radioactive materials at some times in their working lives. Occupational Exposure to Asbestos With regards to asbestos exposure, 56 (21.8% subcohort exposed) subjects reported ever been exposed to asbestos. Based on FINJEM’s code of occupation (aCODE), 21 occupational subgroups were found to be exposed to asbestos in this study. Most often reported jobs were metal smelting furnacemen, aCODE 630 subgroups (n = 27, 12.9%) followed by occupations in manufacturing, aCODE 759 (n = 25, 12.0%). Other subgroups are distributed in table 1. December 2014, vol 11, No. 2 Journal of Occupational Safety and Health 49 Table 1. Code of occupation (aCODE) and the list of occupation with exposure to asbestos based on FINJEM for exposed study subjects 8 Table 1. Code of occupation (aCODE) and the list of occupation with exposure to asbestos based on FINJEM for exposed study subjects aCODE List of occupations with asbestos exposure n %