low level exposure to asbestos and risk
DESCRIPTION
A lecture given at the Weightmans Disease Conference, Birmingham 2010TRANSCRIPT
WORKING FOR A HEALTHY FUTURE
INSTITUTE OF OCCUPATIONAL MEDICINE . Edinburgh . UK www.iom-world.org
The impact of environmental asbestos exposure and it's relevance in cases of low level occupational exposure
John Cherrie
Research Director
www.OH-world.org
Summary…
• Asbestos• Historical uses of asbestos and the
consequences• Risk models• Changes over the last 40 years• Contaminated land• Low-level occupational exposure• Background levels• Conclusions?
3
Asbestos minerals
• Serpentine• Chysotile (white asbestos)
• Amphibole• Amosite (brown asbestos)• Crocidolite (blue asbestos)• Tremolite• Anthophyllite• Actinolite
Fibres...
Fibres are harmful because:• they are thin (d < 3mm)• they are long (l > 5mm) and • because of their shape (l/d > 3)
also because they are persistent in the lung
5
Health effects of asbestos exposure
Asbestosis
Bronchogenic carcinoma
Pleural Mesothelioma
Pleural Plaque
The epidemiology and toxicology…
• Doll (1955) lung cancer
• Wagner et al (1960) mesothelioma
• 1964 New York conference
• Stanton and Wrench(1972) and Pott and Friedrichs (1972) induction of mesothelioma in experiments
HSE guidance from 1970
A serious public health risk...
HSE funded research…
• No evidence of increased risk associated with non-industrial workplaces or ‘low risk’, including motor mechanics and workers handling gaskets and mats
• Only non-occupational exposure associated with increased risk was living with an exposed worker
• Increasing trend in female rates suggest mesothelioma with no known occupational or domestic exposure may be caused by environmental asbestos exposure
Peto et al. (2009) Occupational, domestic and environmental mesothelioma risks in Britain. Report RR696
Occupations affected…
• Historically, insulation workers, shipbuilders and locomotive engineers
• Asbestos exposure was widespread• About 65% of males and 25% of females at risk worked
in medium or higher risk jobs
• The most frequent occupations on death certificates for mesothelioma include carpenters and joiners; plumbers, heating and ventilating engineers; and electricians and electrical fitters
Low exposed jobs…
• Motor mechanic, Draughtsmen, Engineers, Stores & warehousemen, Armed forces, Drivers & road transport workers
• Cleaners, Retail workers, Doctors, nurses & hospital workers, Teachers & school workers, Kitchen workers, Office workers
Asbestos exposures today...
The risks...
• for lung cancer• risk is proportional to cumulative exposure• 1% increase in risk for each year at 1 fibre/ml
• for mesothelioma• risk is related to cumulative exposure and age at first
exposure
• where n = 3.2 and KM = 3.10-8
€
I =KM . f .tn
Hodgson and Darnton model…
15
Gas masks…
16
Death amongst gas mask workers…
0
2
4
6
8
10
12
14
1 6 11 16 21 26 31 36 41 46 51
Mesothelioma deaths per year
1950 1960 1970 1980 1990 2000
Base modelCompeting deathsClearanceClearance and competing deaths
1950 1960 1970 1980 1990 2000
17
Asbestos in soil – where?
• In brown field sites• In green field sites• Gardens to be - on
construction sites• Existing gardens on any
brown field site • Gardens near major
asbestos sites?• Gardens in rural areas
adjacent to asbestos source?
18
Example of sampling site on tracks
20
Air Sample analysis for low levels…
• Samples analysed by electron microscopy (SEM or TEM) for asbestos fibres
• Airborne asbestos concentrations calculated from each sample
• Often need to combine results from several samples over several days to get the necessary sensitivity
Mesothelioma risk…
Scenario Fromage
CumulativeexposureFibre/ml.
hours
Asbestostype
Predicted risk per 1,000,000
HEImodel
Hodgson &
Darntonmodel
Child 2 32.6 amosite 100 120
Child 10 32.6 amosite 100 110
Adult 40 32.6 amosite 11 15
Arc chutes…
• Arc chutes containing asbestos were fitted over and between the copper components
• No visible dust but after handling arc chutes there was a white residue on his hands
• No cutting or drilling required• “Sindanyo” - 50% chrysotile (white) asbestos and 50%
Portland cement• Only 2-days per week in this work • Exposure probably < 0.1 fibres/ml• Hodgson and Darnton model suggests mesothelioma risk
30 per million
Background levels in air…
Study Levels (fibres/ml)
Italian study published 2009 - some areas near damaged asbestos
0.000001 – 0.00001
Italian study published 2006 - near former asbestos mine
0.0001 – 0.0002
USA study published 2007 - inside buildings containing asbestos
Mean 0.00012No sample > 0.01
UK study unpublished - beside asbestos contaminated tracks
<0.0005
UK study published 2001 - homes in Armley, Leeds (no disturbance) - (with disturbance)
<0.0008 <0.0003
UK exposure limit 0.1
in the UK in 1980s…
• Risk for children living near an asbestos factory could be between 2 in 10,000 to 2 in 1,000
Conclusions…
• Mesothelioma epidemic is almost at its peak• Current incidence represents exposure in
1960s and 70s• As time goes on proportionately more cases
will come from “low” or “moderate” jobs• Past environmental exposure may have been
a risk for mesothelioma • In the past living with an asbestos work was
also associated with a risk
My slides are on… www.OH-world.org