APIL Asbestos Conference Exposure from the Engineer’s Viewpoint Quantifying the Dose – how fleeting? Proximity, date and type Engineering issues arising from Asmussen v Filtrona and Williams v University of Birmingham Friday 21 September 2012

Concentrations, exposures and doses – what does it all mean? Low dose cases post Asmussen and Williams 2

A confusing array of terms … Dust concentration Exposure Dose ‘A substantial quantity of dust’ 3

Dust concentration The amount of dust (or fibre) in the air Units: – fibres/ml = fibres/cm 3 = fibres/cc – Particles per cc Where/how was the measurement made: – Area test – Personal sample 4

Dust exposure A measure of dust inhaled over a period of time, therefore … The average dust concentration in a person’s breathing zone over a period of time ‘Time weighted average’(TWA) 5

Dust exposure - example A personal air sample records an average dust concentration for a task of 2 fibres/ml The person carries out the task for 2 hours (and then works in a dust free place for the remainder of the day) The person’s exposure will be: – 0.5 fibres/ml 8 hr TWA (2 hrs/8 hrs x 2 fibres/ml) 6

What’s the significance? Standards are generally expressed as dust concentrations eg TDN 13 triggers Regulations when the average concentration of chrysotile or amosite over any 4 hour period is greater than 2 fibres/ml Exposure is required to calculate the dose (ie the total amount of dust to which a person has been exposed) 7

Dose estimates Estimate of the total dust exposure over a period eg: – Over a working life – With a particular employer Required for: – Divisible diseases re causation – Apportionment Due to uncertainties will be indicative of the order of exposure, not absolute 8

Dose estimates -units Typically: Dose (fibres/ml years) = (8 hour time weighted) exposure (fibres/ml) x (working) years of exposure Other units can be used eg – fibres/ml days – fibres/ml months 9

Some examples 1 1 f/ml = 1 fibre/ml year 25 1 f/ml = 25 fibre/ml years 1 25 fibre/ml = 25 fibre/ml years 10

Quantifying daily exposure Object is to estimate the average exposure concentration over an 8 hour shift (the 8 hour time weighted average (TWA)) If exposure concentration is constant and the shift is 8 hours long then the 8 hour TWA exposure is the same as the exposure concentration. If not then: 8 hour TWA (f/ml) = (C 1 T 1 + C 2 T 2 + … C N T N )/480 Where: C = the exposure concentration and T = the exposure duration in minutes for each period 11

Example A person works at task A with exposure of 2 fibres/ml for 6 hours and task B with exposure of 4 fibres/ml for 2 hours. 8 hour TWA = (2 x 6)/8 + (4 x 2)/8 = 2.5 fibres/ml 8 hour TWA 12

‘a substantial quantity of dust’ Factories Act 1937 and 1961 Not defined, no decided cases – Visible dust cloud, particularly if – Concentration greater than 10 – 12 fibres/ml 13

Low dose cases Exposure is significant (in the context of causation) if it is: “above a level commonly found in the air in buildings and the general outdoor environment” ie above ‘background level’ which is of the order of – f/ml As cited, this is a concentration, not a daily exposure or a dose Suggests dose may not be an issue in non divisible disease? 14

What about short term exposure? Consider a person present for 5 minutes in an area where the concentration of asbestos dust is fibres/ml as a result of dust originating from lagging in poor condition. The concentration is above background, so … The exposure is ‘significant’. (subject to foreseeability of risk) a duty holder could be criticised in the above circumstances, BUT Would it be causative? (a matter for the medics) 15

Thermal insulation (lagging) 15 – 100% asbestos Used up to the late 1960s / early 1970s All types of asbestos used Mixed on site / pre-formed Also includes rope, string, yarn, mattresses and blankets 16 Image source – HSE Proximity, Date and Type?

Sprayed Coatings Up to 85% asbestos Usually crocidolite (up to 1970) Amosite and chrysotile up to the cessation of use in Image source – HSE Proximity, Date and Type?

18 Image source – HSE Asbestos Insulation Board (AIB) 16 – 40% asbestos (mainly amosite) Used from 1950s to circa 1980 Numerous construction uses Fire protection Heat resistance Partitions Some ceiling tiles General building board Proximity, Date and Type?

19 Image source – HSE Asbestos Cement (AC) % asbestos (chrysotile) Early 20 th Century to 1990s Numerous construction uses Corrugated and flat sheets Moulded products Proximity, Date and Type?

20 Friction products Up to 50% asbestos (chrysotile) (as supplied) Majority converted to forsterite in use Use up to the mid-1980s Brake and clutch linings Image source – HSE Proximity, Date and Type?

21 Other products include (but not limited to): Millboard Fire blankets, gloves, protective clothing Flooring materials Textured coatings Proximity, Date and Type?

Liability in low dose cases Two issues: – Foreseeability – ‘Standards of the day’ 22

Asmussen v Filtrona Foreseeability “Even by [1972] the dire consequences of exposure to small quantities of asbestos was not generally recognised … foreseeability of injury is to be tested against the standard of the well informed employer who keeps abreast of the developing knowledge and applies his understanding without delay” (judgement paragraph 55) Implications regarding foreseeability? 23

Foreseeable risk 1965 ‘Sunday Times’ article, but … What exposure specific advice was available? – Guidance Literature? – HMFI? In some instances long standing knowledge (eg manufacturing, application/removal of lagging) In others less clear cut (eg presence of lagging, brake servicing) 24

Asmussen v Filtrona Standards of the day “Safety was to be judged according to the general knowledge and standards of the time. The best indication of the state of knowledge and standards of the time was … Technical Data Note 13. In the light of this guidance, an employer could properly infer that the Factory Inspectorate was indicating at what levels exposure to asbestos fibres was liable to cause danger… the Court was bound to apply the standards of the time” (paragraphs 66 – 67) 25

Asmussen v Filtrona Standards of the day Also reference to Baker v Quantum Clothing: “… statutory duties which refer to safety, injury and danger must … be judged according to the general knowledge and standards of the times” (my emphasis) Paragraph 69 26

‘Standards of the time’ 1937 – 1970: Factories Act ‘any substantial’ or ‘likely to be injurious’ dust 1960: American Threshold Limit Values (177 ppcc, arguably fibres/ml effectively as an 8 hour TWA) 1970: TDN 13 (0.2 fibres/ml crocidolite; 2 fibres/ml other, 10 minute and 4 hour reference periods, subject to 12 fibres/ml maximum 1976: EH 10 similar to TDN 13 but qualified: “Exposure to all forms of asbestos dust should be reduced to the minimum that is reasonably practicable” 1983 on: various revisions to TDN/EH10 standards 27

‘General Knowledge … of the time’ HMFI annual reports Guidance documents – DOE (Dust and fumes in factory atmospheres) – Asbestosis Research Council (ARC) – Asbestos Information Committee (AIC) (?) – HM Factory Inspectorate 28

The implications Asmussen v Filtrona seems to me to support an argument that: – Risk must be foreseeable, and – Exposure below ‘the standards of the time’ will be acceptable Now supported by Williams v University of Birmingham 29

Williams v University of Birmingham Based on exposure, was there a risk that Mr Williams would contract mesothelioma, five steps: – ‘Actual level of exposure’ – Knowledge in relation to that degree of exposure – Was it reasonably foreseeable that injury would occur – What steps should have been taken – Were the steps actually taken 30

Identify the hazard (asbestos dust) and be aware of potential need for precautions Consider the risk (possibility of fatal injury with no known safe level of exposure) Consider the precautions (by reference to knowledge of the day) 31 Compare this to practice

Some observations Should the first consideration be the level of exposure? There is (and was) no known safe level of exposure to asbestos dust The risk under consideration is death (v NIHL in Baker) The pre 1970 standard was to reduce exposure ‘as far as practicable’ – could the intention of TDN13 have been to dilute this standard? For other dusts (not associated with such serious risk) the standard remained to reduce exposure ‘as far as (reasonably) practicable’ – was the intention a less onerous standard for a more dangerous dust? The TDN 13 standards were based on perceived risk of asbestosis NOT mesothelioma. The asbestos industry were consulted in the standard setting process and therefore could be argued to have influenced the standards (interesting comments of Lord Dyson at paragraph 101 of Baker v Quantum – standards can be compromised by lobbying) 32

Low dose cases: Conclusions Each case on its merits Liability may not necessary follow from ‘significant’ exposure post 1965 Carefully consider exposure AND: – Whether or not a risk was foreseeable – What the duty holder could reasonably be expected to do about the exposure 33

John Raper Consultant Forensic Scientist Pragma Asbestos Ltd 2 Beacon Walk Gringley on the Hill Doncaster DN10 4TD (01777)