This document summarizes a historical hygiene assessment of National Semiconductor UK that was conducted to investigate potential occupational exposures. The study reviewed plant records and interviewed former employees to characterize job tasks, hazardous agents like radiation and chemicals, and exposure controls over time. While some early monitoring found exposures above limits, later processes were redesigned with additional protections. An epidemiological follow-up found reduced cancer rates of initial interest and no consistent evidence that cases were more exposed than controls.

1. WORKING FOR A HEALTHY FUTURE
A Review of the United Kingdom
Historical Hygiene Assessment (HHA)
of National Semiconductor UK
John W Cherrie and Karen Galea
INSTITUTE OF OCCUPATIONAL MEDICINE . Edinburgh . UK www.iom-world.org

2. Acknowledgements
• Work funded by the Health and Safety Executive
(HSE)
• Part of an updated mortality study and “cluster
analysis”
• Principal Investigator Dr John Osman
• Other collaborators: Brian G. Miller, Laura MacCalman,
Sam Wilkinson, Andrew J. Darnton, Amy Shafrir,
Damien M. McElvenny

3. Summary…
• The main stimulus for the study
• Outline of the plant history
• Key processes carried out
• Gender differences in exposures
• Key exposures of interest
• The results from the epidemiological
investigations

4. The stimulus for the study…
• Phase II pressure group
• Results form a previous cohort
study undertaken by HSE
• 11 female lung cancers
4 expected
• 3 female stomach cancers
<1 expected
• 4 male brain cancers
<1 expected
• 20 female breast cancers
15 expected

5. NSUK, Greenock, Scotland
4547 employed
before the end of
April 1999
• Wafer fabrication started in the early 1970s
• Many individuals from the local area employed in plant

6. Methodology…
• Interviews with long-service employees and former
employees
• Nominated by company and pressure group
• Scrutiny of records, blueprints etc
• Occupational hygiene measurement data
• Details of ionising and non-ionising radiation sources
• Details of Personal Protective Equipment (PPE) /
Respiratory Protective Equipment (RPE)
• Smoking / health surveillance policies
• Accident / incident reports
• Shift pattern records

7. Plant history…

8. Possible exposure hazardous agents
• Shift work
• Ionising and non-ionising radiation sources
• Toxic metals
• Toxic gases
• Sulphuric and other acid mists
• Various organic solvents
• Asbestos (in buildings) and ceramic fibre

9. Gender differences…
• Originally all operators were female
• The first male operators began in the mid-
1980s By the mid-1990s when there was
equal numbers of males and females
• Supervisory, maintenance, lab technicians
and engineering were predominantly male
• In the early-1990s in Fab 2, men worked on
processes where propylene glycol methyl
ether acetate was used

10. Shift work…

11. Ionising radiation
• Variety of sources, including sealed sources, high
voltage x-ray sources and Krypton-85
• In 1983 tracer flow/leak test process started
• Same year the dose rates from process exceeded
legal limits (Kr-85)
• Additional shielding
• In 1984 process redesigned
• 1986 further problems with Kr-85 imregnatingo-
ring seals
• 1990 process discontinued

12. Antimony and arsenic
• Antimony used in diffusion furnace operations
• Measurements in 1982 showed levels well below OEL
• Arsenic used in diffusion furnaces, ion implanters
(arsine), epitaxial reactors (arsine), vapour
deposition reactors
• Monitoring during process operations below OEL
• Some maintenance tasks resulted in exposures above
OEL, but respirators used

13. Results from the epidemiological study
• SMRs for the three cancers of prior interest for
women reduced in new follow-up
• No further brain cancers in men
• Poor response rate from
subjects/proxies in cluster analysis
• No consistent evidence that cases
more likely to be exposed to
hazards than controls

14. Public response

15. Further information at…
• Leaflet summarising the findings of the follow-up
study
• Main report for the follow-up study
• Appendices to the main report
• Detailed Historical Hygiene Assessment
• www.hse.gov.uk/statistics/publications/nsuk.htm