Exposure assessment for occupational epidemiology part 2
•Download as PPTX, PDF•
2 likes•505 views
The aim of this lecture is to provide an introduction to occupational exposures and the strategies used in epidemiological studies to assess exposure of subjects.
Recommended
More Related Content
What's hot
What's hot (19)
Similar to Exposure assessment for occupational epidemiology part 2
Similar to Exposure assessment for occupational epidemiology part 2 (20)
More from Retired
More from Retired (20)
Recently uploaded
Recently uploaded (20)
Exposure assessment for occupational epidemiology part 2
- 1. INSTITUTE OF OCCUPATIONAL MEDICINE . Edinburgh . UK www.iom-world.org Exposure assessment 2 John Cherrie
- 2. Summary… • General approaches to exposure estimation • Linkage to the individual – the central role of job title • Examples from synthetic mineral fibre studies • JEMs • Use of exposure data • Lenters et al and asbestos
- 5. The essence of exposure assessment… • Identify a theoretical framework for exposure and select the most appropriate exposure metric • Identify the maximum amount of information you can collect about the subjects • Identify an algorithm to translate the available information to an exposure estimate
- 6. Types of exposure metric… • Quantified personal exposure measurements • Quantified job or area data • Ordinally ranked jobs or tasks • Duration of employment in industry • Job title unranked • Ever employed in industry Best Worst
- 7. Information sources... • Personnel records • Other company records • Subject • Relatives or friends • Co-workers • Community records • Environmental monitoring records
- 9. Linkage to individual… • Industry or work area • Job title • Grouped job titles • Task lists by job • Task lists by individual • Obtained retrospectively by interview or collected prospectively • From the subject or other informant source
- 10. European MMMF studies… • Five glasswool plants, seven rock/slagwool plants and two glass continuous filament plants • Total of 13,788 subjects • Employed between 1940 and 1978 Lung cancers SMR 95% CI Rock/slag 97 138 112 - 168 Glasswool 149 112 94 - 132 GCF 14 93 51 - 157
- 11. Changes…
- 12. Descriptive exposure data… Cherrie et al (1986). Environmental surveys in the European man-made mineral fiber production industry, 12(SUPPL. 1), 18–25.
- 13. Technological history… Cherrie, J., & Dodgson, J. (1986). Past exposures to airborne fibers and other potential risk factors in the European man-made mineral fiber production industry, 12 Suppl 1(SUPPL. 1), 26–33. • Early phase • Intermediate • Late phase
- 15. Co-exposures… • Asbestos • Used in some form or other in all of the plants • Four plants used cloth, yarn or cement products in production processes • Polycyclic Aromatic Hydrocarbons (PAH) • Bitumen and tar used in some plants • Polychlorinated Biphenyls (PCBs) • Ionising radiation • Formaldehyde • Possible arsenic exposure
- 16. Exposure assessment for a nested case- control study… • Use of an algorithm based on source-receptor paradigm • Near-field and far-field 𝐶 𝑁𝐹 = 𝜀𝑖,𝑁𝐹. ℎ 𝑁𝐹. 1 − 𝜂𝑙𝑣,𝑁𝐹 . 𝑡 𝑎,𝑁𝐹 + 𝜀 𝑝 . 1 − 𝜂 𝑝𝑝𝑒 . 𝑑 𝑔𝑣,𝑁𝐹 𝐶 𝐹𝐹 = 𝜀𝑖,𝐹𝐹. ℎ 𝐹𝐹. 1 − 𝜂𝑙𝑣,𝐹𝐹 . 𝑡 𝑎,𝑁𝐹 + 𝜀 𝑝 . 1 − 𝜂 𝑝𝑝𝑒 . 𝑑 𝑔𝑣,𝐹𝐹 𝐶 = 𝐶 𝑁𝐹 + 𝐶 𝐹𝐹 Cherrie, J., & Schneider, T. (1999). Validation of a new method for structured subjective assessment of past concentrations. The Annals of Occupational Hygiene, 43(4), 235–245.
- 18. Job-exposure matrices… • Job axis, generally coded to an appropriate standardised coding scheme • Exposure axis, defined by the purpose of the authors • Matrix cells, categorical exposure level (and probability) • Sometimes includes a time dimension • May be extended to include tasks or aspects of exposure algorithms • Exposure assignment generally carried out by ”expert” review FINJEM… NOCCA-JEM… Syn-JEM…
- 20. Geoparkinson study… • 959 cases of parkinsonism and 1989 controls • Exposure assessed for solvents, pesticides and metals • Questionnaire administered to subjects • Significantly increased risk with pesticide exposure and ever knocked unconscious • Tobacco smoking was protective Dick, et al. (2007). Environmental risk factors for Parkinson's disease and parkinsonism: the Geoparkinson study. Occupational and Environmental Medicine, 64(10), 666–672.
- 21. Exposure assessment methods… • JEM produced base estimate • 4 categories of intensity (inhalation, skin contact and ingestion) • High = 100 (equivalent to the occupational exposure limit) • Medium = 40 • Low = 5 • None • Base values adjusted based on questionnaire response by expert evaluation Semple, S. E., Cherrie, J., Seaton, A., Dick, F., Haites, N., Osborne, A., et al. (2004). Exposure assessment for a population-based case-control study combining a job-exposure matrix with interview data, 30(3), 241–248.
- 23. Coke workers mortality study… • 6,600 workers from 13 coke works operated by NSF and 14 BSC plants in 1967 • 20-year follow-up resulted in 300 lung cancer deaths and SMRs of around 1.25 • Annual geometric mean concentrations of inhalable dust, BSM and B[a]P for jobs at NSF plant from 1971 to 1983 • Much more limited data for BSC plants – modelled concentrations • Early measurements probably biased • Time trend in BSM but not B(a)P data Miller, B. G., Doust, E., Cherrie, J. W., & Hurley, J. F. (2013). Lung cancer mortality and exposure to polycyclic aromatic hydrocarbons in British coke oven workers. BMC Public Health, 13(1), 962–1. http://doi.org/10.1186/1471-2458-13-962
- 24. Historic monitoring data... • Benefits… • quantitative data • Drawbacks… • may be unbalanced or incomplete • changes in sampling or analytical methods • variations in sampling strategy • changes in process or control measures
- 25. Results from coke study… • No evidence for a relationship of lung cancer risk with exposure to either BSM or B[a]P • There was a statistically significant increase in risk in men with more than 5 years spent working in Ovens Tops jobs at BSC • The estimated relative risk for this was 1.81, • Overall, there was little evidence of an effect of coke oven exposures on lung cancer risk
- 26. Lenters et al… • Classified quality of exposure assessments • Documentation • CE ratio, i.e. the ratio of the average exposure in the highest and lowest CE categories • Conversion factor used • Coverage of exposure data • Job histories
- 27. Summary… • Many strategies open to estimate exposure • Understand the theory behind the exposures and select an appropriate metric • What information about the subjects is available? • Translate the available information to an exposure estimate
Editor's Notes
- Nellie Kershaw was born in Rochdale in 1891. She left school, aged 12, to take up employment and began working in an asbestos mill – later Turner Brothers Asbestos. She was a rover, spinning raw asbestos fibre into yarn. She died aged 33 from asbestosis. 113 men who worked in an asbestos factory. 39 dead.
- Nested case-control study. Cohort 31k men – data from pension fund. Job information and limited info about industry only. OR for engine crew for mesothelioma was 9.75, 20 year latency Lymphoma OR = 2.78 amongst Deck personnel on tankers and leukaemia OR = 2.26 to 6.86 depending on duration of employment Example of job-title approach
- 7
- 10
- 11
- 14
- 15
- 17
- Earliest JEMs originate in the 1980s Most often used for population-based case-control studies.
- OR = 1.13 for low vs no exposure = 1.41 for high vs no exposure
- Adjustment rules provided… Symptoms reported while working with solvents Ventilation and engineering controls Use of respiratory protective equipment (RPE) Work location Quantity of solvent used
- Complex mixture What to use as a marker of risk?
- 24
- Armstrong review and meta-analysis: 100 μg/m3 years benzo[a]pyrene was 1.20 [95% confidence interval (CI), 1.11–1.29]