Lung Disease and Work

The Lane Lecture is an annual event hosted by the Centre for Occupational and Environmental Health at the University of Manchester. Named in honour of Ronald Lane, the first ever Professor of Occupational Health at the University.

This year the lecture was delivered by Professor David Fishwick, Chief Medical Officer and Co-Director of the Centre for Workplace Health. His talk was entitled The lungs at work: from cotton mills to composites? One of the key messages is that diseases such as byssinosis and silicosis are not historic issues.

In 1890 there were more cotton mills in Manchester than in the rest of the world. But that is no longer the case – the industry has been transferred overseas, particularly to developing economies. So byssinosis, which is caused by exposure to cotton dust, is no longer a problem in the UK. However, it’s a different matter in those countries where cotton is now produced.

Studies carried out in recent years have shown high incidences of byssinosis in some mills in developing countries. One study in Karachi, Pakistan in 2008 found that among 362 textile workers 35.6% had byssinosis. (Prevalence of Byssinosis in Spinning and Textile Workers of Karachi, Pakistan, Archives of Environmental & Occupational Health, Vol. 63, No. 3, 2008 )

Professor Fishwick also focused on Silicosis, the oldest known occupational lung disease which remains a significant problem across the globe, including the UK. This debilitating disease is caused by exposure to respirable crystalline silica (particles smaller than 10 microns) which can occur in many industries, including mining, quarrying, brick and tile manufacture, stone masonry, glass manufacture, tunnelling, foundries, ceramic manufacturing and construction activities.

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The risk is clearly associated with the level of exposure and it only takes a regular exposure to very low concentrations to cause the disease. The US Occupational Safety and Health Administration (OSHA) estimates that 30% of workers with 45 years of exposure to 0.1 mg/m3 respirable crystalline silica dust will develop silicosis (see page 16394 of the “Final Rule”). Yet 0.1mg/m3 (respirable dust) is the current Workplace Exposure Limit for crystalline silica in the UK.

Clearly the current WEL is not a “safe level” and there is a very strong case for reducing it. In the US OSHA has recently announced a reduction in their Permitted Exposure Limit for silica down to 0.05 mg/m3. No change is proposed in the UK. The HSE’s view is that there are difficulties accurately measuring exposures lower than 0.1mg/m3, so it would be difficult to demonstrate compliance, and that, in any case, employers have a duty to not only meet the exposure limit but the apply “principles of good control practice” set out in Schedule 2A of the Control of Substances Hazardous to Health Regulations. Not everyone agrees with them, however.

As well as causing silicosis, respirable crystalline silica is a carcinogen. It’s estimated that in the UK it causes around 600 deaths per year from lung cancer shows  with 450 of these occurring from exposures in the construction sector.

Occupational cancer deaths by cause in Great Britain, 2005 (HSE)

Personally, I’d like to see the WEL reduced and research done to develop better sampling methods which will allow low levels of exposure to be evaluated. I do sympathise, though, with their emphasis on control. Reducing exposure by introducing improved controls is the key to preventing workers from developing industrial disease. Measurement can help us to understand exposure and identify where improved controls are needed. But sometimes the problem is obvious and in those cases it’s better to spend time, effort and money sorting it out, particularly when there are well established solutions available.

Silica exposure in the construction industry

One of the most important health risks encountered by construction workers is exposure to respirable crystalline silica dust. Crystalline silica, mainly in the form of quartz, is the main component of most rocks, sands and clays. In the construction industry it can be found in  stone, concrete, aggregates, mortars and other materials.

Respirable particles (smaller than 10 microns in diameter) of crystalline silica,  which are produced during many common activities such as cutting, blasting or drilling granite, sandstone, slate, brick or concrete, penetrate deep down into the lungs where they can cause serious damage. Regular, repeated exposure to respirable crystalline silica can lead to silicosis, a debilitating lung disease, chronic obstructive pulmonary disorders (COPD) and lung cancer. It usually takes many years of exposure to silica dust before these symptoms start.

A couple of weeks ago I was giving a talk to a meeting of safety consultants on the BOHS breathefreely initative and decided to include some discussion on silica exposures in the industry. Unfortunatly no major study has been carried out in the UK. However, there are several detailed papers on exposures in the industry in some comparable countries in the Annals of Occupational Hygiene and other journals, so I was able to include some figures in my talk.

The research has shown that many of the common activities undertaken in the construction industy lead to exposures well in excess of the UK Workplace Exposure Linit of 0.1 mg/m3 for respirable silica – and this isn’t a “safe limit” with an estimated 2.5% of workers exposed to this concentration for only 15 years developing silicosis. Yet for most of the common operations where workers are at risk from exposure to silica, there are control measures available that are usually relatively straight forward to implement.

Health and Construction

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On Monday this week a worker on a construction site in central London, a former US naval building in Grosvenor Square, died after the building he was working on partially collapsed. At least one other person had to be treated treated for minor injuries.

Accidents on construction sites are all too common. In the period 2012/3 148 people were killed as a result of an accident at work. 39 of these worked in the construction industry. According to statistics from the Health and Safety Executive, although it accounts for only about 5% of the employees in Britain the industry accounts for 27% of fatal injuries to employees and 10% of reported major injuries.

The incident on Monday was a tragic accident that made the headlines. But there are other hazards faced by construction workers that don’t appear in the news. Construction workers can be exposed to various hazardous agents that can have a major impact on their health, the most important including

  • asbestos – although no longer used in Europe it can be present in older buildings and workers can be exposed to asbestos containing dust during refurbishment and demolition work
  • respirable crystalline silica – present in many materials used in construction of buildings
  • diesel exhaust emissions – diesel powered vehicles and equipment are commonly used on construction sites

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According to the HSE exposure to these agents has resulted in

  • About 3 700 occupational cancer cases are estimated to arise each year as a result of past exposures in the construction sector;
  • There were an estimated 74 thousand total cases and 31 thousand new cases of work-related ill health during 2012/13
  • over 500 construction workers are believed to die from exposure to silica dust every year.

Construction workers can also be exposed to other chemicals, such as solvents which are present in paints, adhesives and other products. And they can be exposed to physical hazards such as noise, vibration and solar radiation.

The health effects from all these agents don’t appear over night. They are long term, sometimes only appearing many years after first exposure. So it’s easy to ignore them – but they are responsible for considerable more deaths than accidents at work. An article in the Observer last Sunday reported that last year there were 2,500 deaths due to asbestos exposure, 500 due to respirable crystalline silica exposure and 200 from diesel exhaust emissions. So 3,200 deaths due to exposure to hazardous substances compared to 39 due to accidents. A ratio of more than 80 to 1.

And it’s not just about fatalities. Occupational disease also affect quality of life. The HSE has estimated that averaged over the period 2009/10 to 2011/12 74,000 people whose current or most recent job in the last year was in construction, suffered from an illness (longstanding and new cases) which was caused or made worse by this job.

It’s important that employers make strenuous efforts to ensure the safety of their employees while working on construction sites to prevent tragedies like the accident that occurred last Monday. But, in addition, more attention needs to be paid to those health risks. 

Occupational Cancer–The Causes

Following on from my last post on occupational cancer, I thought I’d look at the latest evidence on what causes the 8000 estimated deaths every year that are linked to occupational cancer.

HSE commissioned Dr Lesley Rushton and colleagues, from Imperial College London to lead a project in collaboration with experts from the Health and Safety Laboratory (HSL), the Institute of Occupational Medicine (IoM) and the Institute of Environment and Health, to produce an updated and detailed estimate of the burden of occupational cancer in Great Britain. Their findings have been published in a HSE Research Report. They make interesting reading.

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Occupational cancer deaths by cause in Great Britain, 2005

The main cause remains asbestos, accounting for almost half of the deaths. Other “traditional” causes also featured prominently – such as mineral oils.  Exposure to diesel exhaust emissions, recently confirmed as a cause of cancer in humans by the International Agency for Research on Cancer (IARC) was also identified as a major work-related cause. There were some new revelations. Although crystalline silica has been recognised as a human carcinogen for some years, I was surprised at the number of cases attributed to exposure to silica containing dusts.

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Exposure to silica dust during construction work

In most cases the implementation of good occupational hygiene practices to control exposure to these chemical agents would significantly reduce the number of cases.

Another interesting finding was that shift working was a major cause of breast cancer in women. Solving this one is more challenging and would require some new thinking and approaches to control.

Occupational cancer is a growing problem. Lesley Rushton at the last BOHS Annual Conference 2013 who noted that by 2060 the number of deaths from occupational cancer will have risen by 5,000 to 13,000 a year if we do nothing. I don’t think we can let that happen

Controlling silica exposure during fettling of castings

In foundries, once  the casting is removed from the mould it is usually necessary to remove excess metal and remedy defects. This process is usually referred to as “fettling” or “finishing”.

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Fettling normally involves the use of powered hand tools such as chippers and grinders. The operation presents a number of significant risks. Using power tools exposes the workers to high noise levels and hand-arm vibration. There is also a risk from exposure to the dust generated by the process. The dust will largely consist of metal particles, but this is usually of low toxicity. The main concern occurs where sand is used for the moulds in which the metal is cast. This is crystalline silica. Some particles of sand from the mould adhere to the metal and grinding during fettling can lead to the release of fine dust including particles of respirable crystalline silica. “Respirable”  particles are smaller than 10 microns in diameter and can reach the deepest regions of the lung. Regular, repeated exposure to respirable crystalline silica can lead to silicosis, a serious, debilitating lung disease.

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Risk of silicosis – Source: HSL

Respirable crystalline silica has a very low Workplace Exposure Limit of 0.1 mg/m3 as respirable dust. In fact, as the above chart shows, long term exposures to concentrations much lower than this can lead to some workers developing silicosis. There is also evidence that prolonged workplace exposure to crystalline silica can lead to an increased risk of lung cancer, although this is only likely to occur in those workers who have already developed silicosis. Given the nature of the risk exposures need to be reduced as low as practicable.

So, it’s important to ensure that the dust generated during fettling is properly controlled, particularly when there is a risk of exposure to silica. In most cases, the most practical and effective way of doing this is to install well designed local exhaust ventilation. The Health and Safety Executive have developed a number of sheets providing practical advice on how to control dust and fume generated during foundry processes, including fettling. For small castings they recommend the installation of an extracted booth. The work is carried out inside the booth which then contains the dust generated allowing it to be removed effectively by the extraction.

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Source: HSE COSHH Essentials for foundries. FD7 “Fettling small castings”

Recently, one of our consultants was carrying out a survey in a foundry. They had installed this type of booth for their fettling operations. However, as can be seen in the following photograph,  The booth was not being used in the way intended – the worker was carrying out the work outside the booth.

 

The dust generated was not contained and, consequently, the extraction would not be as effective as it should be. The worker will have a higher exposure than if he carried out the fettling inside the booth.

In a previous post I outlined the key steps needed to control health hazards in the workplace. The first steps are recognising that a risk exists and then making sure that appropriate, effective controls are specified, designed and implemented. In this case the risk from dust exposure was recognised and a local exhaust ventilation system with an appropriate hood design was installed. The problem is that it is not being used properly, considerably reducing its effectiveness.

Once controls have been implemented they need to be properly managed to ensure that during use they continue to do the job they were designed to do. This requires training, supervision, maintenance, testing, audit and review. It’s a management responsibility to ensure that controls are properly used so more vigilant supervision seems to be required.

In this example, there could be a number of possible reasons why the booth was not being used correctly. Perhaps management and the workforce don’t fully understand the health risks and so don’t appreciate the importance of using the controls properly. Perhaps the workers haven’t been properly trained on how to use the booth. However, there could be a problem with the design of the booth. It is possible that carrying out the work inside the enclosure presents the operator with some practical difficulties. Perhaps the fine work required is difficult to complete properly if the casting is inside the booth or the booth dimensions, particularly the height, could cause the worker to adopt an awkward posture which causes discomfort and could lead to musculoskeletal problems. Solving one problem often creates another. Ergonomics is often neglected when designing engineering controls for chemical hazards. Ideally workers need to be consulted and involved in the specification and design of the controls and its good practice to build and test a prototype before finalising the design. Proper commissioning of the controls should also check for usability.

Further investigation would be required to get to the root cause of this problem. However, the case illustrates the importance of proper management of the design, implementation and use of controls.