Welding is one of the most common activities carried out in industry. HSE estimate that there are around 190,000 welders in UK. However, this is likely to be an underestimate of the total number of workers who carry out welding as there is likely to be a large number who do a small amount of welding on an occasional basis.
There are a number of health hazards associated with welding in particular:
- Gases, including ozone and, with MIG and TIG welding, inert gases that can present a problem when working in confined spaces
- UV radiation from the welding arc. This can effect the eye (“arc eye”) and skin and is also responsible for the generation of ozone from atmospheric oxygen.
The main health hazard with many welding operations – particularly MMA (stick) and MIG welding – is the welding fume. This consists of very fine particles of metal oxides, mainly arising from the welding rod or wire.
The composition of the fume varies depending on the metal being welded. With mild steel it will mainly consist of iron oxide but there is also likely to be a small percentage of manganese which is used in welding rods. Repeated exposure to low concentrations of manganese have been shown to affect the nervous system and the Workplace Exposure Limit for manganese will be reduced significantly in 2018. Stainless steel welding is particularly hazardous as the fume contains nickel and chromium VI oxides which are highly toxic if inhaled – both are carcinogens and can also cause occupational asthma.
As well as the fume (particulate), Arc welders will also be exposed to gases. Ozone is produced by the action of the UV from the arc on oxygen in the air. It is highly irritant to the eyes and respiratory system. In some cases, particularly with thicker plate, atmospheric nitrogen can be converted to highly irritant nitrogen oxides. With MIG and TIG welding the inert gas used to stop the weld oxidising will be released. This should not present a risk when welding outdoors or in a well ventilated area, but can present a serious risk of asphyxiation in a confined space.
The UK Health and Safety Executive estimate that exposure to welding fume causes more than 150 deaths due to cancer every year. Exposure to the fume and gases can also cause other diseases including
- Metal fume fever
Many welders are exposed unnecessarily to welding fume. Control measures are available – but it’s important to make sure the right controls are used – there is not one solution that will be effective in all cases.
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.
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.
Workplace Health Without Borders (WHWB) is an international organisation of occupational hygienists and other occupational health professionals dedicated to providing technical assistance, training and skills development to workers in developing economies to help them to develop the capacity and local infrastructure to manage and improve health conditions in their workplaces. I’ve been involved with the organisation for a couple of years and last year helped to set up a branch in the UK.
Last week, I gave a presentation on the work WHWB is doing on LEV to a joint conference organised by the British Occupational Hygiene Society (BOHS) and the Occupational Hygiene Society of Ireland (OHSI) in Liverpool on Exposure Control and Containment. The presentation was based on my own experience helping a company in Tanzania (a consultancy project) and some advice I provided to a project in Uganda on behalf of WHWB, but mainly focused on the LEV aspects of the Agate worker project using some excellent material provided by Paul Bozek of Toronto University.
The presentation slides (with annotation) are available on Slideshare
Last week The British Occupational Hygiene Society held a joint conference with the Occupational Hygiene Society of Ireland (OHSI) in Liverpool. Exposure Control and Containment 2 (ECCII), was a follow up to the successful event held in Cork two years ago. The Conference was held in the Crowne Plaza Hotel on the waterfront, just a short distance from the “Three Graces” at the Pierhead.
During the afternoon of the first day of the conference delegates were given the opportunity of joining a site visit. This entailed a short walk to this building, located in George’s Dock, just behind the Mersey Docks and Harbour building.
A large Art Deco style structure faced with Portland limestone and decorated with Egyptian motifs that were popular in the 1930’s, not long after the discovery of the tomb of Tutankhamen. It’s effectively a huge chimney surrounded by offices built as part of the ventilation system for the Queensway Tunnel (also known as the Birkenhead Tunnel). It’s certainly one of the fanciest chimneys I’ve ever seen!
It was designed by Liverpool architect Herbert James Rowse (1887-1963) and the carved Egyptian style decorations on the portals are by sculptor Edmund Charles Thompson (1898-1961).
The control centre for the tunnel ventilation system, as well as one of the ventilation stations, is located here and this is what we went to visit.
The tunnel was opened in July 1934, and at the time, at 3.24 kilometres (2.01 mi) long. it was the longest road tunnel in the world, a title it held for 14 years until the opening of the Vielha Tunnel in Spain in 1948. It remained the longest underwater tunnel though, until 1955. The entrance is right in the centre of Liverpool and being built in the 1930’s it only has a single carriageway of four lanes, two in each direction.
Mersey Travel, who own the tunnel, organise regular tours of the tunnel showcasing its history and allowing the public to gain access to the old control room, ventilation equipment and the tunnel itself. They also can arrange special tours for schools, companies and other organisations. Given the theme of the conference – about the control of exposure to hazardous substances – the tour was customised to highlight how the air quality is controlled.
After donning our hi-viz vests and safety helmets, our guides, Alison and Billy, gave us a potted history of the tunnel and described how it was constructed. Billy was a real “Scouser” – born and bred in Anfield (although a true Evertonian!) with lots of stories and plenty of jokes and wisecracks. A true entertainer!
The tunnel cost £8million to build and employed 1700 men in difficult working conditions under the river bed. 1,200,000 tons of rock and gravel had to be excavated by two teams working from either side of the river. Pilot tunnels were excavated, one starting in Liverpool and the other in Birkenhead, eventually to meet in the centre – less than an inch out of alignment! – on 3 April 1928. The pilot tunnels were then enlarged to create the full sized tunnel. There’s more information about its construction on the Merseyside Maritime Museum Website and a more detailed description here.
First stop was the old control room, which was in use until relatively recently. This required climbing several flights of steps (you need to be fit for this visit!!)
Ventilation of the tunnel to remove contaminants from vehicle exhausts, is provided by massive fans located at 6 ventilation stations, including the one at George’s Dock. Fresh air, brought in from above street level, is blown through the ducts beneath the roadway. The air enters the upper half of the tunnel through outlets18 inches apart at roadway level. The air flow is balanced by varying the size of the outlets to ensure an even distribution of air throughout the tunnel. Contaminated air is extracted through vents in the roof of the tunnel to the exhaust chambers at each of the six ventilating stations.
It’s incredible to think that the original fans, built and installed in the 1930’s, are still in use. They are enormous, with the largest capable of moving 641,000 cubic feet per minute (315 cubic metres per second).
I was rather pleased to hear that one of the two fan suppliers was Walker Brothers of Wigan (my home town) who specialised in equipment for mines. In the 1930’s there was little knowledge or experience of how to control air quality in road tunnels so, perhaps not surprisingly, they fell back on the technology used to ventilate coal mines.
Here’s some old pictures showing the fans being installed.
This diagram illustrates the operation of the ventilation system (showing the Birkenhead side). It appeared in the second edition of a short lived British magazine “Wonders of World Engineering”, published in March 1937.
I found the image here.
We were then taken all the way back down and below ground level to look inside the tunnel itself. It’s very narrow and the cars speeded past only centimetres from where we stood on the observation platform. No photographs were allowed to minimise the distraction of drivers of the vehicles passing through the tunnel – we didn’t want to be the cause of an accident.
Then it was back up the stairs to the ground floor where we handed in our safety gear at the end of what was a very informative and entertaining visit.
Last week I was up in Glasgow for the annual BOHS Conference. As usual, there were lots of good interesting Keynotes, workshops and technical sessions. And there were plenty of opportunities for networking – and some fun too.
One of the highlights for me was the very first session, the Warner lecture, which this year was given by Professor Sir Anthony Newman Taylor, the renowned and respected expert in respiratory disease. Sir Anthony is the President’s Envoy for Health at Imperial College London and also chairs the new Workplace Health Expert Committee recently set up by the Health and Safety Executive. The theme of his lecture was The continuing challenge of UK Lung disease.
The Health and Safety Executive estimate that there are about 13,000 deaths every year in Great Britain due to respiratory disease caused by exposures to hazardous substances at work. The main agent of concern is asbestos, followed by respirable crystaline silica. Due to the long latency period associated with these diseases (i.e. the time taken for the disease to develop) most of these deaths have ben caused by historical exposures. So some people might argue that the numbers will reduce in the future as the substances causing the disease have either been banned (i.e. asbestos) or are becoming better controlled, and that these diseases are a problem of the past. However, for Sir Anthony this is not the case.
He pointed out that although silicosis is sometimes considered to be a disease of the 19th and 20th Centuries, there are still a significant number of cases in the UK, particularly in the construction industry where at least 50% of workers are exposed to silica. Internationally, examples of where silica exposure occurs include sandbalsting of oil platforms in Mexico and the use of sand to produce faded denim jeans. In both these cases the serious risk of silicosis and cancer can be prevented by substituting alternative processes or materials.
Although the use of asbestos has been prohibited in the UK, it is still present in many buildings, and there is still a risk of exposure for maintenance workers, electricians, plumbers etc. and also for building occupants where the material degrades. Even low exposures to asbestos, particularly the amphiboles (which include “blue” and “brown” asbestos) can lead to the development of mesothelioma, a serious cancer of the tissue surrounding the lungs. So it is likely that workers will continue to develop asbestos related disease for many years to come.
Other respiratory diseases also continue to be a problem, including asthma in bakers, paint sprayers and other workers and hypersensitivity pneumonitis associated with exposure to metalworking fluids.
New technology also presents risks to health, including respiratory disease. One example Sir Anthony highlighted was carbon nanotubes, which potentially have many uses. These very fine, fibre like particles have many similarities with asbestos in that they are small enough to reach the deep lung and are resiliant, so aren't easily absorbed by the body. Given these properties, perhaps it isn't surprising that there is evidence that they may present the same health hazards as asbestos, particularly mesothelioma.
There have been major changes in employment in the UK, with many of the “traditional” heavy industries exported overseas to the “developing” economies in Eastern Europe and the Far East where labour is cheap. Measures to control exposure in these countries are often less stringent and effective meaning that the historical industrial diseases are likely to re-emerge. Some might argue that the othe side of this coin is that these diseases will decline and even disappear in the UK. However, this is too simplistic an analysis. Sir Anthony demonstrated that there are still exposures occuring which are likely to mean that these diseases will continue to be a problem for many years to come. Yet most of the problems Sir Anthony highlighted could be prevented or, at least, reduce by applying good occupational hygiene practice. Unfortunately, many employers don't recognise this. So there is still much work for BOHS to raise awareness of the problems and the solutions and continue to argue for more emphasis to be placed on controlling health risks in the workplace.
A couple of weeks ago I travelled down to Birmngham to give a talk on behalf of the BOHS Breathe Freely initiative at the Health and Wellbeing event at the NEC. The Title of the talk was Managing Health in Construction – What Good Looks Like. An annotated version of the slides I used during the talk are now available on Slideshare
To prepare for the talk I did a little research on the meaures that are readily available to control exposure to contaminants, particularly dust, during common activities on construction sites. A number of studies have been done, both on-site and in the laboratory to assess the effectiveness of water supression and on-tool extraction for power tools. These studies have confirmed just how they can be.
- A large scale study in Ireland by Healy et al showed that the use of local extraction built into on-tool shrouds could reduce dust exposures by up to 99%
- Laboratory tests by Thorpe et al showed water suppression on cut-off saws reduced dust levels by up to 99%
Despite this, in a large proportion of cases these engineering controls are not being used with reliance placed on respiratory protection which is often incorrectly used and inadequately managed. So one of the main aims of the BOHS Breathe Freely initiative is to raise awareness of the types of controls that can be used to reduce exposure. Hopefully in the not too distant future we’ll see water supression and on-tool extraction become the norm rather than the exception.
Measurements of the Eectiveness of Dust Control on Cut-off Saws Used in the Construction Industry. Thorpe et al. Ann Occup Hyg Vol. 43, No. 7, pp. 443-456, 1999
An Evaluation of On-Tool Shrouds for Controlling Respirable Crystalline Silica in Restoration Stone Work. Healy et al. Ann Occup Hyg 2014;58:1155-1167