Will a brief exposure to asbestos always lead to the development of an asbestosis disease or even the fatal mesothelioma cancer of the lung linings? It’s a question that can be often asked by those who have a family member who remembers having a temporary contact with asbestos at some stage in their working life. One recent example concerns a deceased victim who – in his early 20s was employed for only a few months at a factory during the late 1960s to cut asbestos sheeting on a circular saw every day.

The victim’s widow recalls her late husband mentioning how he breathed in the airborne fibre dust caused by the sawing process, and which also settled on his work-clothes and exposed skin. The Asbestos Industry Regulations 1931 – in force at the time – did not apply outside the asbestos-using industries, and only covered specific activities such as textile weaving and spinning. It often meant that no adequate breathing protection was ever supplied in many other industry sectors where men were in daily contact with the deadly fibres, and where there was also a general lack of asbestos awareness to the long term health dangers. It was only when The Asbestos Regulations 1969 – which actually came into force in May 1970 – that the first quantity control levels of exposure to asbestos were introduced, which widened protection to workers in other industries.

Nevertheless, cases have been heard in court where it is argued that even the briefest of exposures led to a claimant’s mesothelioma. The phrase “one fibre can kill” was first used in the 1980s when referring to a brief but intensive exposure primarily encountered by tradesmen, building/demolition workers, firemen and other emergency services.

Exposure to asbestos for just 6 hours

In one case, a 69 year old carpenter’s labourer was diagnosed with mesothelioma more than 35 years later from an exposure to asbestos over just four weeks. A 67 year old victim believed his cancer was the result of asbestos exposure at a summer job in 1970, while still a student. In another tragic example, exposure to the deadly brown ‘amosite’ asbestos for just 6 hours in the late 1970s was strongly believed to have led to a victim’s mesothelioma nearly 40 years later.

Use of asbestos in insulation products and as a material strengthener was in decline by the late 1970s and a first ban introduced on brown and blue asbestos in the mid-1980s. However, young men women starting their working lives during the 1970s and 80s could still be at risk of brief occupational – and non-occupational exposures in a school, hospital or council building. Previous research into twenty years of medical data of over 2,000 males exposed to asbestos found that the highest incidence of malignant pleural mesothelioma was among those first exposed during the early part of their life, particularly if they were under or around 20 years old.

Employer defendants have argued in court that brief exposures would not accumulate sufficient quantities of fibres in the lung tissue to increase the probable risk of developing an asbestos- related disease. The “Helsinki Criteria” of 1997 had set the fibre ml level at 25 fibre/ml years or above, at which mesothelioma, asbestosis or lung cancer would be held to have been caused by asbestos exposure. The level of exposure would be determined on a scale from 1 year’s ‘substantial’ exposure at 25 fibre/ml through to 5 years ‘moderate’ exposure at 5 fibre/ml per year.

Risk of cancer varied between different industries

In 2005, the Industrial Injuries Advisory Council (IIAC) relooked at the criteria and obtained evidence to show that the risk of lung cancer varied between different industries at similar levels of cumulative exposure to asbestos. The IIAC cautioned that “counting techniques have a significant false negative rate” and recommended that a diagnosis of asbestosis should be based on clinical evidence of lung lining fibrosis and a history of occupational exposure to asbestos. In 2011, the UK was repeatedly called upon to comply with guidance set out by the European Asbestos Directive, which addresses the issue of “sporadic and low intensity exposure to asbestos” rather than simply measuring the extent of exposure and risk.

As recently as 2015, London School of Hygiene and Tropical Medicine published research which showed that lifetime mesothelioma risk is around 0.02 per cent per 1000 amphibole (sharp, needle-shaped) fibres per gram of dry lung tissue from 1 to 4 in the most heavily exposed building workers to less than 1 in 500 in most of the population. Today, The Health and Safety Executive (HSE) state that the exposure control limit is 0.1 asbestos fibres per cubic centimetre of air (0.1 f/cm3) averaged over a four hour period.

In the same year, latest HSE figures revealed that mesothelioma mortality had increased to more than 2,540. One year later, further date revealed that mesothelioma or non-malignant pleural diseases associated with asbestos exposure accounted for 60 per cent of cases reported to SWORD – the HSE funded scheme to monitor work-related respiratory disease in the UK.