New developments in advanced welding
Environmental issues
The last 30 or more years have seen a significant awakening of interest in the environment and a much greater understanding of how human activities in one geographical area can have long term and far reaching effects in another. The difficulties in research into environmental effects are possibly even greater than those in epidemiology. It is difficult to obtain measures of changes in the variables in the land, water and air, the effects of such changes on the earth and its climate cannot be predicted, and the effect of changes that might be made to try to reverse a trend are unknown. Changes that are to be made involve co-operation between nations and the involvement of the people within them. They can be difficult to ‘sell’ because they can be in conflict with economic and social aspirations.
Three drivers in the environment are discussed here:
• Preservation of the ozone layer by restricting emissions of ozone-depleting chemicals;
• Reduction in global warming by restrictions on emissions of greenhouse gases;
• Sustainability in all its forms, which includes the controlled disposal of waste.
In many ways, the third of these drivers incorporates the other two and they are not entirely separable.
Ozone is a gas that is formed from oxygen, with the formula O3. It is relatively unstable, readily reforming oxygen, O2, especially when it comes into contact with surfaces. Ozone is a familiar gas in the welding workplace, being formed in significant quantities when welding stainless steel and aluminium with the TIG (GTAW) and MIG (GMAW) processes. The mechanism for its formation is the action of ultraviolet (UV) light on oxygen in the atmosphere around the arc. It is not normally found in any significant quantity in processes such as manual metal arc, because of the high levels of fume generated by that process. Ozone is also formed at ground level due to the action of ultraviolet light from the sun on air containing oxides of nitrogen and volatile organic compounds. It is thus found in quite high concentrations in some cities, as a result of pollution from vehicles. Ozone at ground level is a significant hazard to health, as it can cause lung damage.
The ‘ozone layer’ is a region of the atmosphere high above the earth where a proportion of the oxygen molecules also form ozone due to the action of UV radiation from the sun. In the upper atmosphere the production and persistence of ozone plays a crucial role in filtering out a proportion of the harmful UV coming towards us from the sun, preventing it from reaching the earth’s surface. Exposure to UV has a proven adverse effect on humans, being a known cause of skin cancer. Ozone produced at ground level does not persist long enough to drift into the upper atmosphere. The recognition that several substances in widespread use were drifting into the upper atmosphere and reducing the effectiveness of the ozone layer led to the Montreal Protocol in 1987. Chlorofluorocarbons (CFCs) had been identified as ozone depleting substances and an agreement was drawn up to phase out CFCs, along with several other ozone depleting substances, which was signed by around 60 countries.
Worldwide, CFCs were used in aerosols, as solvents, in refrigerants and in foam blowing; their use was widespread. In the welding environment, therefore, the phasing out of these substances has been most noticeable in non-destructive testing, where aerosol dyes and developers are commonplace. Several of the properties of CFCs made themselves attractive for these applications - they appeared largely inert, non-toxic and non-flammable. Substitution for CFCs in aerosols has brought different hazards into the workplace - CFCs are non-flammable, but many of the substitute propellants, such as butane, are highly flammable.
Other substances that have been phased out as a result of the protocol include 1,1,1-trichloroethane and bromochloromethane, which were both marketed under several trade names. These were common solvents for degreasing and, when choosing an alternative, users should assess carefully the potential replacement substance for its toxicity, flammability and environmental effects.
Trichloroethylene is one substitute, but unfortunately this substance suffers from several drawbacks. First, it is a much greater hazard to human health than is 1,1,1-trichloroethane and there have been many instances of people being overcome by entering degreasing tanks when the vapours are present, sometimes with fatal consequences. It has also recently been officially classified as a carcinogen, so those currently using the substance should review their use of it in the light of this reclassification. Note that in Table 10.1 it is listed as having a workplace exposure limit. Users should therefore consider either substitution of a substance with a lower intrinsic level of hazard, or the total enclosure of the processes in which it is used. Many of the old degreasing baths that were used for 1,1,1-trichloroethane do not offer sufficient protection for them to be suitable for use with trichloroethylene.
Large users of solvents will find that their operations fall under the Solvent Emissions Directive,34 which aims to reduce the quantity of volatile organic solvents being emitted into the atmosphere, particularly those that are designated as carcinogens. Trichloroethylene, as an organohalogen compound and a carcinogen, is on the ‘Black List’ of substances in the EEC, where the declared intention is to eliminate the pollution they cause.
Volatile organic compounds are also associated with the production of ozone at ground level, as described above. Information on possible substitutes
35
and good practices is available in a leaflet from Envirowise.35
Lastly, solvents are generally banned from discharge to groundwater. In particular, even trace quantities of trichloroethylene can render groundwater unusable for drinking.
Carbon dioxide and other greenhouse gases such as nitrous oxide, methane and CFCs are implicated in global warming. Measurements going back over a century show a steady increase in the concentration of carbon dioxide in the atmosphere. The sun’s radiation, on entering the earth’s atmosphere, spans from the UV to the infrared. Some of this is absorbed by the earth’s surface and the oceans, some is absorbed by plants and used as a source of energy for photosynthesis and some is absorbed by the atmosphere where it causes changes in pressure which give rise to winds. Energy is reradiated to space with the longer wavelengths (infrared) predominating. However, gases in the atmosphere that absorb the energy in these wavelengths prevent it from being radiated out into space and the energy is retained close to the earth. This leads to the temperature of the earth and its atmosphere being higher than they would be in the absence of this absorption.
While it is true to say that if the atmosphere had no greenhouse gases the earth would be too cold to live on, we are currently concerned that too much carbon dioxide and other gases that absorb infrared radiation may change the climate and make the earth too warm. The model for predicting carbon dioxide levels is imperfect, since it is not yet fully understood where all the carbon is stored in the earth and how the balance of carbon dioxide in the atmosphere is maintained. Stores of carbon include living plants and animals, fossil plants, rocks and a considerable amount of carbon dioxide dissolved in the oceans. Climate change will bring with it changes in the patterns of growth of many organisms, some of which will add to the carbon dioxide in the atmosphere, and some of which will remove it.
Concerns about global warming led to the Kyoto Climate Change Protocol where most industrialised countries agreed to take measures to reduce the emission of substances that contribute to climate change. These substances include CFCs, carbon dioxide, nitrous oxide and methane. The question of CFCs had already been addressed in the Montreal Protocol, due to their ozone depleting potential. Nitrous oxide and methane are produced in large quantities by the decay of biological material. Carbon dioxide is produced by the combustion of carbonaceous materials of all kinds, by decaying organic materials, by respiration and by fermentation. Of these, the release of carbon dioxide from fossil fuels is of most concern, because the carbon in these deposits has been in the earth’s crust for millions of years, where it had effectively been removed from circulation.
This driver is leading companies towards consideration of where the greatest emissions of carbon dioxide are produced. A leading manufacturer of welding consumables36 made an estimate of the CO2 emissions associated with all its consumables during one year, encompassing the entire life cycle of the consumable from raw material extraction and conversion to its use in welding and disposal of the waste. They have estimated that during the life cycle of the consumable, approximately 41% of the emissions are associated with raw material extraction and conversion, 37% with welding, 11% with production of consumables and 9% in transport. A life cycle analysis is a very powerful tool for assessing impacts and planning for reductions, as it helps to avoid saving in one area only to make the problem worse in another.
Sustainability is generally defined as the ability of the world to meet its needs today without compromising the ability of future generations to do likewise. This includes considerations of the environmental factors already mentioned, but in addition recognises that the earth is a finite resource - there are only fixed quantities of resources such as metals, oil and other fossil fuels. Thus we are concerned with the depletion of resources and the emissions to the atmosphere, water and soil, which result from the fabrication, use or disposal of manufactured articles.
The environmental impact of consumables includes the emissions of gases and particulates, the use of energy and the wastes that are produced. Ultimately, the product that has been fabricated using the consumables will also become waste, unless it is recycled. In the future it is probable that manufacturers will need to invest more effort in designing articles that can be dismantled and reused, or recycled.
Welding equipment itself also has an environmental impact. However, a life-cycle analysis shows that with welding equipment the greatest environmental impact lies in its energy consumption while it is being used. Thus, designing equipment that is energy efficient will have the greatest impact.
10.3 Sources of further information and advice
The book Health and Safety in Welding and Allied Processes2 describes the key hazards associated with a wide variety of welding processes, the health effects and the control measures that reduce the risks to welders. It addresses the legal requirements of both the UK and the USA and contains almost 200 references.
In major industrialised economies there is a well-established framework governing the obligations of the employer towards the preservation of the health, safety and welfare of his or her employees. Differences are apparent both in the approach that is taken to health and safety, and to the standards that are acceptable. However, there is much common ground, as would be anticipated because the basic research on health effects is available to all. Thus much of the information that is published in one country can be used beneficially in another. However, each country has its own legislature and its own enforcing authorities and readers should ensure they know their own legislative framework.
Many countries have large organisations concerned with research into health effects, the setting of standards and the dissemination of information. In this section, some major sources of information are listed. While postal addresses are given for most of these, the reader will find that almost all are readily found on the world wide web. Web addresses are given for only a few, due to the problems that arise when addresses change, but the rest may be found very readily using a search engine. The world wide web is an impressive resource. Readers will find that they can now obtain information extremely quickly via the web. However, the material on the world wide web is not peer reviewed and readers should exercise caution. The organisations mentioned in the following sections provide good quality advice, based on sound research, and their publications, and those of organisations like them, are preferred.
10.5.2 International resources
The World Health Organisation (WHO)37 is concerned with all matters of health and publishes several books of interest to those studying occupational hygiene. The International Agency on Cancer Research (IARC)38 is part of the WHO and is concerned with the assessment of the data that link substances to cancer. They undertake research of their own and critically assess the evidence available. They maintain a database of all the substances that have been assessed, classified under four headings, according to the weight of evidence. This ranges from those that have been proved to cause cancer, down to those that are probably not carcinogenic. The monographs detailing the evidence that was taken into account are all published on their internet site.
The International Commission on Non-ionising Radiation Protection, ICNIRP,39 acts as an independent international body of experts whose principal aim is the dissemination of information about the effects of exposure to nonionising radiations. The International Institute of Welding (IIW)40 has a Commission (VIII) on the subject of health and safety in welding. They have a limited range of published documents.
The text of UK Legislation is obtainable from Her Majesty’s Stationery Office (HMSO).41 The law on health and safety is enforced by the Health and Safety Executive (HSE) for most industrial workplaces and by local authorities for others. The HSE runs an information service and an extensive website.42 The research arm of the HSE is Health and Safety Laboratory43 whose research underpins much of the advice offered by the HSE. One of their current projects is to improve the quality of analysis of Cr (VI) in welding fume. This is part of a European proficiency testing scheme previously managed by the Danish External Quality Assessment Scheme.
The enforcement authority for environmental matters is the Environment Agency.44 Practical advice and guidance on environmental matters are also available from Envirowise.45
TWI, The Welding Institute46 is a non-governmental organisation that carries out research into welding and joining. It offers research, consultancy and advice for its members and offers training facilities to the wider welding community. The website contains many documents giving free advice to the welding community. These consist of a series of sheets with the title ‘Job knowledge for welders’ and the ‘Frequently asked questions’ resource. They have also developed an interactive tool ‘Welding fume tutor’ in conjunction with the Health and Safety Executive, industrial sponsors and union representatives.
The National Radiological Protection Board31 is concerned with both ionising and non-ionising radiation and gives advice on such diverse subjects as exposure to sunlight, radioactive sources and mobile phones.
The Institution of Occupational Safety and Health47 is Europe’s leading professional body for health and safety professionals. It has a Royal Charter and operates a membership structure designed to reflect the competence levels of its members. It awards the designation Chartered Safety and Health Practitioner CMIOSH, to those who meet the educational and experience requirements.
The text of legislation is obtainable from the Occupational Safety and Health Administration (OSHA), who enforce the requirements.48 They develop mandatory safety standards and provide technical assistance, training and education.
The Centers for Disease Control and Prevention (CDC) have the National Institute of Occupational Safety and Health (NIOSH)49 within its umbrella. This is a federal agency that conducts research and makes recommendations for the prevention of work-related diseases and injury.
The American Conference of Governmental Industrial Hygienists (ACGIH)50 is a non-governmental organisation of practitioners in industrial hygiene, occupational health, environmental health and safety.
The Board of Certified Safety Professionals51 is a not-for-profit certification board for safety professionals. It sets the academic and experience standards that are required for practitioners and awards the designation Certified Safety Professional, CSP, to those who meet the educational and experience requirements.
The American Welding Society, AWS,52 is an organisation that offers certification, research, conferences, education and many other services. It has a publications section that markets a wide range of advice booklets on the subject of welding, a large number of which are concerned with health and safety.
The text of legislation is published by individual states, but it can be accessed via the Attorney General’s Department.53 The National Occupational Health and Safety Commission is the Statutory authority.54
The Canadian centre for occupational health and safety (CCOHS)55 is a national organisation giving information about occupational safety and health. It has a resource ‘OHS answers’ on the world wide web and enables workers in Canada to access the laws specific to their own territory.
