low level exposure to asbestos and risk

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?

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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

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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…

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Gas masks…

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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

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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?

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Example of sampling site on tracks

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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