Arsenic and Old Wool: An Early Example of the Precautionary Principle in the Risk Management Cycle or a Sheep in a Toxic Wolf’s Clothing?
ANDREW WATTERSON* The paper explores arsenic as an active ingredient in the cycle of dipping substances used to control sheep parasites in the UK in the 19th and 20th centuries. Technological optimists prevailed over a small number of prudent decision-makers in agriculture and used untested, unknown, suspect or even known carcinogens such as arsenic for supposed economic gain and, at the same time, marginalised worker health. Early unsuccessful efforts were made by some in industry to apply the precautionary principle primarily for consumer protection reasons; but action only occurred when ‘better’ products appeared on the markets. A similar pattern was to be repeated in later decades with other active ingredients. The risks were inevitably almost always born by the farm worker and small farmer. Sheep dipping demonstrated cyclical developments depending on which risks were assessed and what political and economic pressures were at work. Such pressures included perceived economic gains as well as compulsory regulatory dipping controls. Meanwhile, the evidence base of toxicology and occupational medicine developed in particular ways, whereby different adverse health effects of arsenic sheep dip were documented at different time periods. Focusing on the uneven and cyclical nature of these processes, this paper highlights how the dominance of chemistry over the biological and medical disciplines ultimately led to a neglect of the subtle and chronic effects of arsenic dips on human health. The paper concludes by drawing potential lessons from these developments.
Arsenic occurs naturally and is a metalloid with both properties of a metal and non-metal. Arsenic pigments, dyes and mordants were used in the 19th century. In the 21st century water pollution by arsenic presents a major public health threat in countries such as Bangladesh, while in ‘developed countries’ wood treated by arsenic has also come to represent a serious health threat. Arsenic is usually found in the environment combined with oxygen, chlorine and sulphur: that is in the form of ‘inorganic arsenic’. Arsenical pesticides are mainly inorganic and were used to control parasites such as ticks, scab, keds and blow flies that attacked sheep. Arsenic proved effective in controlling some, but not all, of these parasites. These pesticide formulations of arsenic are the ones that have most documented ill-health effects in humans. In the 19th century sheep and animal dips contained sodium and potassium arsenite, arsenious oxide, arsenic sulphides and thioarsenates. The pervasive toxicity of these compounds is evidenced by the fact that old sheep dip sites in Australia contaminated by arsenic are now considered a threat to public health. Organic arsenic is produced when arsenic combines with carbon and hydrogen. A few organic arsenic pesticides are still used (ATSDR, 2007; Oliver, 1902; Hunter, 1962).
Other uses of arsenics have included labels, cardboard boxes, children’s books, Christmas decorations, printed and woven fabrics, children’s toys, carpets, lino, coloured soaps and sweetmeats all in the 1880s. Arsenical compounds also occur in smelting and ore refining. They also take the form of white arsenic which occurred in sheep dip production (as sodium arsenite); in the insecticide Paris green, used on fruit trees (as copper aceto-arsenite); and in Scheele's green (as cupric arsenite). White arsenic was further used as a preservative of hides, skins, and furs.
Arsenical compounds in industry were light and hence represented a dust hazard (Q. J. M. New Series Ho. 48). By 1879, Henry Carr publicised a paper on the toxicity of arsenical colours entitled ‘Our Domestic Poisons’. This was followed in 1880 by Oliver, who noted the injurious effects of arsenic in dye workers. By the 1900s, Oliver observed that sheep dip makers and those washing clothes of sheep dip manufacturers suffered from effects on ‘their extremities and nervous system’ (Oliver, 1902).
This paper explores arsenic usage in dipping to control sheep parasites in the UK in the 19th and 20th centuries and the underpinning approach to hazard identification and risk assessment. It examines how risks were perceived, assessed, recorded and reported during that period. This analysis forms the basis for a discussion of the potential lessons that can be drawn from these risk perceptions, assessments and related risk management strategies for the future regulation of hazardous substances.
THE ECONOMIC AND AGRICULTURAL FRAME FOR DIPPING
Historically, ‘ecological’ sheep farming came first. Farmers bred only those sheep that were ‘adapted’ to their environment and resistant to diseases created in that environment because no technological or chemical alternatives existed. This limited the breeds and numbers and location of grazing available. Such sheep did not necessarily produce the most or best wool and meat, but they were ideally suited to subsistence and ‘organic farming’. In the middle and late 19th century and early twentieth century, the markets for sheep grew and spread to the colonies. This coincided with the growth of industrial chemistry, growing knowledge of biology and significant mechanical engineering advances; whereby only the former significantly influenced pest control at the time.
‘Large’ sheep farmers’ economic interest in producing meat, wool and leather dominated approaches to sheep farming during the period in question. This tended to shape governmental regulations, requiring dipping at certain times and with certain dips, and supposedly ensured markets for large sheep producers without necessarily establishing the most effective method(s) for controlling parasites. It also created additional costs and labour burdens for small sheep farmers. Intermittently this hegemony was threatened by consumer interests such as the hosiery industry’s concerns about arsenic contaminated wool products, or consumer reluctance to purchase leather goods from sheep damaged by parasites. Meanwhile, minimal attention was paid to health risks created for those making arsenic dips, contract dippers and small farmers who dipped their own, and their neighbours’, sheep. The following section examines the causes of this disjunction.
SHEEP FARMING CYCLES AND DIPPING CYCLES
Sheep dipping products and techniques have ‘evolved’ over centuries in the UK. The evolution has been spasmodic and uneven; and at times the developments appear to be cyclical (see Figure 1).
Figure 1) Approaches to Sheep Farming
In the ‘Ecological’ stage, farmers only kept—or keep— those sheep breeds, such as the Hebridean sheep, that were— or are— ‘adapted’ to their environment in the absence of pesticides. This approach often relates to subsistence farming and ensures the survival of small rural populations dependent on their sheep as a major part of their meat diet and as a resource for clothes through wool. leather and other materials. In ensuring resistance to diseases created in these environments, the choice of sheep is limited in terms of breeds, numbers and locations of grazing. While there were no other alternatives to the ecological approach in mediaeval times, in modern organic farming, such sheep provide a niche commercial market; albeit that certain veterinary medicines are approved for use on ‘organic’ sheep with regard to parasite control if the welfare of the sheep may be affected by those parasites. The ecological approach also relied on good husbandry methods and very regular inspections of flocks. With growing markets and the economic imperative to raise very large flocks, and with higher labour costs, such methods were not attractive to commercial farmers
With the historical development of a lucrative market for wool, sheep farming first used non-toxic dipping. This dunking of sheep was simply to ensure the sheep’s wool was cleaned in the water from streams and rivers to increase wool saleability. No parasite control was used.
Scientific advances then led to greater choices for sheep farmers wishing to control parasites that damaged fleeces, weakened sheep and affected the quality of leather available from the hides. This led to the gradual adoption of different approaches (see Figure 1):
Toxic: Controlling sheep parasites to ensure sheep production with products assumed safe for sheep; but no evidence available for such assumptions either available or, if available, used. Efficacy was assumed, but not fully proven, to flow from usage of veterinary pesticides and economic factors drove developments. Sheep and human safety in the dipping process were never explored in the early stages of product use. Arsenic and sulphur were key active ingredients in dips of this stage followed later by organochlorines (as the limited persistence of arsenic rather its neurological, dermatological and carcinogenic effects were recognised by manufacturers and farmers).
Toxic: Controlling sheep parasites that threaten not wool or meat production but leather quality. Organophosphates were key active ingredients here. These replaced organochlorines because the latter’s persistence and environmental toxicity was recognised. Evidence about arsenic’s toxicity to workers was not ranked as highly as organochlorines’ adverse impacts on UK raptor populations.
Toxic: Controlling sheep scab, largely in the absence of data on sheep morbidity or mortality which resulted from these applications. This applied at various stages to sulphur, arsenic, organochlorine and organophosphate sheep dips. The usual pattern for product development was to assume that no animal or human toxicity existed; and, only over time, would such evidence emerge. Hence new products were by definition thought to be safer because the evidence base on their effects did not exist. By the time evidence of toxicity did emerge, new products would have been developed and workers exposed to the old products would either have retired or, if adversely affected by the old products, have great difficulty in gaining recognition of occupational illnesses and compensation.
Toxic: Controlling of parasites which may affect sheep and workers. This involved moves to improve application technologies.
Toxic: Substituting chemicals that adversely affect workers with ones that are safer from an occupational health perspective but may damage, through incorrect high dose applications or disposal, the environment because of water pollution. This part of the cycle led to the reduced use of organophosphates and the introduction of synthetic pyrethroid dips (Watterson 1997).
Toxic: Usage of injectables which reduce risks to workers and the environment, but potentially increase risks to consumers. Injectables have eliminated worker exposure to dips and put an end to direct water pollution; but they have created potentially increased risks to consumers who eat lamb and mutton and may ingest the injectables.
‘Revised’ Ecological: This returns to the earliest sheep farming practices. It depends on raised animal husbandry standards, lower stocking density, selection of breeds suited to specific region, minimal use of veterinary medicines- pesticides not available in the original ecological stage - and greater labour input.
Chemical, Commercial And Toxicological Developments Linked To Arsenic Sheep Dips
With larger markets and flocks, chemistry drove innovations in sheep parasite controls abetted by some engineering technology advances. Biological and medical disciplines contributed far less to sheep dip developments; and hence the means available to monitor and measure the risks to human health were limited. The subtle effects of arsenic dips often went undetected, the crude effects in terms of mortality went unrecorded, and the chronic effects remained obscure or unknown. This is a familiar pattern in the history of occupational diseases and is partly based on the deliberate social construction of ignorance amongst politicians, regulators and scientists who failed to inform workers of the risk to their health that they ran. Workers often identified the hazards and related diseases themselves (Legge, 1934; Watterson, 1993).
By the 1800s, there were already reports of arsenical use in UK dips (Hendricks 1937). The Georgians and early Victorians lacked any toxicological or epidemiological knowledge that they could draw on to make risk assessments. Hence the assumption always was that any new materials that appeared to work were safe to use. The ‘Complete Grazier’ of 1807 discussed an arsenical sheep dip preparation as an example of ‘leading edge’ and untypical chemical sheep tick control which was at the time used by Lord Somerville in Norfolk. This involved “four pounds of soft soap and two pounds of arsenic be steeped in thirty gallons of water and the animals be immersed in the suffusion…. ” (quoted in Hendrick, Trans Roy High Ag Soc, 1937)
Between 1843 and 1852, a vet, William Cooper developed a mixture of arsenic and sulphur in experimental sheep dips. In 1852 he began the large scale factory-based production of this dip. A description survives of the process, although almost all the family members involved in the production at this time died in their 30s and 40s (The Story of Coopers of Berkhamsted, Dacorum Heritage Museum):
The arsenic and sulphur were dressed using a machine called 'the Joggler'. This consisted of a long flat sieve in a deep box which was moved backwards and forwards at high speed by a wrench. The mixture was then boiled in the Kiln which was attached to the Grinding Mill. It was then cooled for several days until it had the consistency of treacle. The powder was then placed on the kiln floor and mixed with the liquor by men using shovels. When thoroughly mixed, it was spread out evenly on the kiln floor and pressed down tightly by men walking over it. Initially, the men wore their own shoes but eventually were provided with boots. William Cooper noted, 'It is a serious affair if the 'dipping' gets into their feet'.
By 1857, the British medical journal ‘Lancet’ was carrying reports of skin effects on the hands, arms, thighs and scrotums of shepherds who dipped sheep for nine hours in one day; which was a common occurrence at the time (Lancet, 1857). Other reports of arsenical sheep dip poisoning were also well known to physicians and publicised in definitive works on poisons and medical jurisprudence (Taylor, 1859).
The acute risks to those manufacturing arsenic were considerable, but chronic risks do not appear to have been fully identified by the medical profession until studies in the first part of the century by Sir Thomas Legge were reported (see Table 1 below; and Neubauer, 1947). This is despite the fact that the 1895 Workshop Act required every medical practitioner to report cases of arsenic poisoning in factories and workshops that they attended (Legge, 1934: 4). It seems unlikely that many medical professionals at the time would have been able to diagnose such illnesses and the law did not apply to agricultural uses. At the same time, similar reports about the hazards to dippers emerged in Governmental enquiries by the Board of Agriculture and Fisheries 1904. By 1913, UK medical professionals were reporting arsenic cancer affecting sheep dip factory workers in the Lancet (Harwood et al., 1913).
In Australia, the Australian Workers Union in the 1920s noted the skin irritation caused by arsenical sheep dips specifically to shearers and called for their banning. These calls had little success because of the employers’ arguments that such bans would damage the industry, and because their views were supported by leading scientists (Penrose, 1999: 259). No similar protests emerged in the UK or none were reported (the numbers of UK shearers would, of course, have also been much smaller). This was the case despite the fact that UK studies had been cited to support the Australian workers’ arguments in the 1920s and 1930s. Legge’s discovery of cancer cases among arsenic sheep dip manufacturing workers, published in his standard occupational medicine text of 1934, must have reached a large medical readership. However, it produced no immediate regulatory response in the UK.
In the 1930s it was increasingly recognised that arsenical dips, though very effective against external adult parasites, could be washed off. Hendrick (1937), accordingly, reported that:
Sheep ticks. Worked for one hit only;
Keds. Adults killed but not pupae and they miss second dips as they hatch 21 days after being laid;
Lice. Some are killed but not all unlike more successful carbolic and nicotine dips.
Arsenical soaps, moreover, could lead to prolonged exposure of animals (sic) to arsenic which resulted in serious poisoning. Hence, despite the effectiveness of arsenicals, they were gradually abandoned. However, there was no move to remove from them from the market on account of their carcinogenicity.
Standard UK medical texts on occupational medicine in the 1940s by Collier (1943: 252-255), and in the 1950s by Lloyd Davies (1957: 178), recognised the acute and chronic toxicity hazards including lung cancer presented by arsenic and noted its prescribed industrial disease status. But both textbooks argued that these problems could be controlled by industrial hygiene measures; even in agricultural situations and sheep dip manufacturing. Moreover, neither suggested that the toxicity of the metal necessitated its removal from the workplace. In Collier’s case, this was possibly prompted by the report of only one case of arsenical poisoning notified to the Chief Inspector of Factories in 1936.
The toxicity of arsenic had been reported with regard to different target organs throughout the 19th and early 20th centuries, as well as in earlier sources (Source, Neubauer, 1947). These reports covered:
Dermal effects [Agricola, 1556; Arlidge, 1872; Morris, 1902; Dunlap, 1921] which included adverse effects to the public through stockings, handkerchiefs and gloves that had been dyed with arsenic;
Respiratory effects which included laryngitis, bronchitis and rhinitis, (asthma) [Morris, 1902; Dunlap, 1921] as well as nasal septum perforation [Dunlap, 1921];
Gastrointestinal effects[Morris, 1902];
Neurological effects [Morris 1902];
Conjunctivitis [Dunlap 1921].
Table 1) Dates of knowledge on arsenical toxicity related to sheep dip, other manufacture
[ Source: Watterson – Collection of history of sheep dipping papers. University of Stirling, Stirling held at Stirling]
Arsenical dips were replaced firstly by organochlorines and then by organophosphates and synthetic pyrethroids. However, arsenic compounds were still listed in the UK Ministry of Agriculture, Fisheries and Food ‘A Guide to Veterinary Pesticides’ in 1984 with a variety of uses and with a UK supplier (1984: 89). Even in 2002, the UK Health and Safety Executive regulatory and enforcement agency was still producing leaflets referring to the use of arsenic in pesticides.
Inorganic arsenic, as well as being a known human skin and lung carcinogen (Ihrig et al., 2008) is also a well known reproductive health hazard. In 2008 it was linked to prostate cancer and endocrine disruption according (Benbrahim-Tallaa and Waalkes, 2008; Davey et al., 2008).
In 1981, the Swedish researcher Goran Pershagen noted that inorganic arsenic’s poisonous properties had been well known for centuries, with recent reviews highlighting its chronic respiratory, cardiovascular, neurological and haematopoietic effects. He also noted that the health effects of organic arsenic compounds remained inadequately investigated, and importantly, that the carcinogenicity of arsenic had not materialised in some animal tests.
By 1980, the International Agency for Research on Cancer (IARC) (1987), eventually, concluded that arsenic was a proven human carcinogen. This drew on evidence from occupational studies, including pesticide manufacture and application, about work–related cancers published in the 1960s, 1970s and 1980s (Thiers, 1967; Pinto, 1978; Horiguchi, 1979; Mabuchi, 1980; Luchtruth, 1983; Buiatti, 1985; Leyh, 1985). However, as Table 1 above illustrates, evidence of arsenic’s carcinogenic properties significantly predates the IARC decision.
APPROACHES TO HAZARD IDENTIFICATION AND RISK PERCEPTION ON ARSENIC
The default position, dominant in science, is to assume the null hypothesis of ‘no effect’ until definitive evidence emerges to the contrary. This works well in some scientific settings, but it is the antithesis of the approach needed in public and occupational health, because it may be too late to protect he public health when exposures have occurred (Watterson, 1993). An alternative approach is the precautionary principle which accepts lower levels of evidence, or the similarities between chemicals and processes already known to be hazardous, as evidence for a need to protect public or occupational health. This approach has been adopted, for instance, by agencies such as the European Environment Agency (2001). In the case of arsenical sheep dips, however, there were several factors which prevented the timely recognition of these hazards.
Technological and Legislative Drivers Linked to Economic Development
Hand dipping was not possible with the large sheep flocks in the colonies and this led to the invention of the swim bath and, later in the 20th century, to jets and showers in such countries as Australia.
The political, if sometimes declining economic, dominance of landowners in the political systems of many countries meant that legislative approaches to perceived sheep pests that threatened markets were to ensure blanket requirements on dipping; albeit that the efficacy of such approaches had not always been established. Dipping was seen as a necessary quick fix, even though evidence of it effectiveness was lacking and there was ample and growing knowledge about the adverse health effects of dipping with a range of pesticides (Watterson, 1997). Those most at risk were, of course, agricultural workers on large estates who had few legal rights and little trade union organisation to protect them. Contract dipping workers were in a similar position, as were small hills farmers in vulnerable rural areas of the UK who would often do the dipping themselves.
Legislation requiring dipping, with a few lacunae, dates back many decades. The 1903 UK Diseases of Animals Act empowered the Board of Agriculture:
To make regulations for ‘prescribing, regulating and securing the periodic effective dipping of sheep’ or the use of some other remedy for sheep scab;
To ensure that sheep were dipped with a dip approved by the Ministry of Agriculture;
To ensure that some sheep in certain areas were double dipped;
To enforce the use of an arsenical dip for second dipping.
As the dipping had to be approved by the Ministry, and as they approved arsenic despite evidence about its limited persistence, sometimes poor results and known or suspected adverse effects on workers were detected as early as 1902.
In the 1930s, the British Ministry of Agriculture still required arsenical dips to be used with levels of arsenic present that related to impacts on parasites rather than safeguards for workers. This flew in the face of the significant body of epidemiological, clinical and toxicological evidence about adverse human health effects that existed in both the UK as outlined above (and in Australia as Penrose, 1999 described).
Diluted dip at this time had to contain:
Not less than 0. 2% of total arsenic (as arsenious oxide);
Not less than 0. 13% of soluble arsenic (expressed as arsenious oxide).
In 1935, there were 91 approved arsenic dips of which 49 contained tar acids. There were also 210 tar acid dips, 12 of which contained some arsenic (Hendricks, 1937). Despite mounting evidence of adverse effects, compulsory dipping of sheep continued, with some interruptions, throughout the 20th century.
Sheep dipping products and techniques have ‘evolved’ over centuries in the UK. The evolution has been spasmodic, uneven and, at times, complex. Ecological and biological controls of sheep parasites have lagged behind chemical controls and related application technologies. Sheep dipping practices demonstrate cyclical developments depending on which risks were assessed and what political and economic pressures were at work. ‘Large’ sheep farmers’ economic interest in producing meat, wool and leather dominated during most of the period in question. This tended to shape governmental regulations requiring dipping at certain times and with certain dips; supposedly ensuring markets for large sheep producers without necessarily implementing the most effective method(s) for controlling parasites. Economic governance and regulation were strong throughout the period in question. Social governance to protect workers’ health, meanwhile, was weak and rarely properly enforced. Dipping regulations also created additional costs and labour burdens for small sheep farmers. At other times, consumers’ interests dominated the regulation of sheep dips, primarily on account of hosiery industry concerns about arsenic contaminated wool products, or consumer reluctance to purchase leather goods from sheep damaged by parasites. Additional animal welfare arguments were used even though the risk to sheep survival from dipping and dips was manifest. Minimal attention was paid to the health risks affecting those making arsenic dips, or contract dippers and small farmers who dipped their own and their neighbours’ sheep.
Some of this disjunction can be attributed to the historical development of sheep farming. During the ‘ecological’ stage, farmers could only breed those sheep that were ‘adapted’ to their environment and resistant to diseases created in that environment. This limited breeds, numbers and locations of grazing available. Additionally, these sheep did not always produce the most or best wool and meat.
With larger markets and flocks, chemistry drove innovations in sheep parasite controls, abetted by some engineering technology advances. Biological and medical disciplines contributed far less to sheep dip developments and hence the means available to monitor and measure the risks to human health were limited. The subtle and chronic effects of arsenic dips often went undetected, the crude effects in terms of mortality went unrecorded and the chronic effects remained obscure or unknown. Although the toxicological and medical evidence base on the adverse effects of these dips grew rapidly, the UK scientific and scientific civil service community was slow to act on many of the early warnings of damage to workers’ health. This pattern of government supported careless in the application of these toxins resulted in a significant, and avoidable, loss of human life.
The history of sheep dipping in the UK exposes a pattern where technological optimists prevailed over prudent decision-makers and used untested, unknown or suspect carcinogens such as arsenic. Early unsuccessful efforts were made by some in the industry to apply the precautionary principle to arsenic in order to protect consumers and markets. This pattern was repeated with other dips at other times. The greatest risks resulting from these approaches were born by the economically and politically weakest parties; namely farm workers contract sheep dippers and small farmers.
With concerns growing about global warming, carbon footprints, food miles, animal welfare, supply chain checks and fodder inputs, there is now mounting support for ecological approaches to sheep farming. However, global issues of food production and food security, which have re-emerged in 2008, have also created support for technical solutions which are associated with the misnamed ‘Green Revolution’ of the 20th century.
The ‘Green Revolution’, a classic example of technological optimism and scientism, promised scientific fixes for agriculture that would produce food for all globally through extensive use of pesticides, fertilisers and new crop varieties not normally available to the developing world. The revolution failed to address the political and economic factors that created poverty and food scarcity and hence it failed spectacularly to end world hunger. What it did do was boost the profits of agri-capital enterprises which benefited from the sale of genetically engineered crops. In the context of risk cycles, it led to the spread of engineered crops that were resistant to pesticides especially herbicides, and thereby ensured future markets for the agro-chemical industry. The same revolution encouraged the genetic engineering of animals and now there are possibilities of producing breeds resistant to parasites, or breeds capable of being treated by veterinary pesticides without adverse effects– with side-effects we do not yet know about. This is indicative of another iteration in the risk cycle, and specifically one which is again prioritising technological optimism and producer interests over health and safety concerns. Whether this cycle will be as harmful as previous ones will depend to a large degree on how risks are assessed and addressed, and specifically whether precautionary or traditional approaches to risk management guide policy makers.
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* ANDREW WATTERSON is Professor and Head of the Occupational and Environmental Health Research Group, RG Bomont Building, (R3T11), University of Stirling, Scotland, FK9 4LA, firstname.lastname@example.org