Sheep dip – has the wool been pulled over our eyes?

Sheep dip – has the wool been pulled over our eyes?
Many farming processes, sheep dipping being one of them, have the potential to cause significant adverse

The farming sector was the number one industry causing pollution incidents in 2015 (1) and remains one of the top four causes according to the Environment Agency’s 2018-2019 Annual Report (2).

The UK’s most common agricultural impacts are associated with the use of pesticides, nitrogen compounds, livestock waste and soil erosion (3). There are approximately 34 million sheep and lambs currently on farms in the UK (4), with sheep dips a prime example of a use of pesticides within the agricultural industry.

Sheep dip

Figure 1: Image captured in September 2015

What is sheep dip?

Sheep dipping is when farmers immerse sheep in a chemical compound to eliminate sheep scab and other ecto-parasites including ticks, lice and blowfly (5). Sheep dip chemicals were first developed in the 19th century and would at that time commonly include arsenic. Arsenic based compounds were used up until the 1950’s and can still remain in soils surrounding historical sheep dipping baths (6). These days sheep dip compounds often contain organophosphorus (OP) or synthetic pyrethroids (SP) compounds which can leach through the soil and pollute groundwater (7).

Figure 2: Ordnance Survey map extract (c.1975 1:2,500)

What are the risks?

Whilst not as toxic as arsenic, the modern compounds are far from safe to human health. Organophosphate exposure can cause coma, vomiting and diarrhoea. Over a longer term they can cause issues with fertility, cancer, as well as brain and nerve problems (8). It’s also interesting to note that organophosphates are the basis of the nerve agent novichok which was used in the recent Salisbury attack (9). Pyrethroids are considered safer for farmers but they can also interfere with nerve and brain function. It has been indicated from animal studies that long term exposure may cause cancer. (10). Additionally, many incidents of pyrethroids causing significant aquatic death were recorded in the 1990’s (11).

Long-term poisoning

From the 1970’s until the late 1980’s it was compulsory for farmers in the UK to dip sheep twice a year with OPs (12). Many farmers who used the regulation sheep dip were later diagnosed with chronic illnesses such as multiple sclerosis (12). In recent years there have been calls for an enquiry as it has been alleged that the government were aware of the health risks but did not publicise the dangers or provide farmers with adequate guidelines for safer use (13).

Safety first

Although there are health risks associated with sheep dipping they are now fairly well known and regulatory bodies publish comprehensive guidance documents.
In order to reduce the exposure of contaminants and to protect the environment, the Health and Safety Executive (HSE) suggest that pour on products and injectable treatments for scab control may be used as an alternative to plunge dipping (14).

The HSE advise the following controls are undertaken to minimise human health and environmental implications:

  • Ensuring ventilation, to prevent excessive vapour inhalation,
  • Use appropriate equipment such as a metal handed crook and wearing of personal and respiratory protective equipment (RPE and PPE),
  • An entry slope, splash boards and screens to reduce splashing from sheep entering the dip bath,
  • Ensure that the dip bath has no drains or leaks, and should be inspected prior to use,
  • Draining pens should be have an impermeable sloped floor which allows sheep dip compounds to drain into the bath,
  • Absorbent material such as sand, earth or sawdust should be used to soak up spillages and placed into a sealed container and labelled for disposal at a licensed waste disposal site,
  • Clean water supply for topping up the bath, decontamination and rinsing.

Figure 3: Edited from the HSE Agricultural Information Sheet No.41

What’s happening now?

These days a licence is required to undertake sheep dipping and as a result, mobile sheep dippers are becoming increasingly common (15). The licensed specialists travel to farms with their equipment and operate under regulations. This could hopefully see a decline in the sheep dip related illnesses of the past. However, the cost of sheep dip disposal permits has recently significantly increased – up to 590% (16). These price hikes could lead to more users disposing of the chemicals improperly in order to avoid the fees and it’s possible that as a result we’ll see a repeat of the damage to the environment which occurred in the 90’s.

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  1. Environment Agency, 2016. Pollution Incidents 2015 Evidence Summary. [pdf] Environment Agency. Available at: [Accessed 19th August 2019]
  2. Environment Agency. 2019. Annual report and accounts for the financial year 2018 to 2019. [pdf] Environment Agency. Available at: [Accessed 19th August 2019]
  3. Skinner. J.A et al.(1997). An Overview of the Environmental Impacts of Agricultural in the UK. Journal of Environmental Management, 50: 111-128.
  4. Agriculture and Horticulture Development Board, 2018. UK Sheep Yearbook 2018. [pdf] Agriculture and Horticulture Development Board. Available at: [Accessed 19th August 2019]
  5. AgriLand, 2018. 5 Reasons why farmers need to dip sheep. Available at: [Accessed 19th August 2019]
  6. Robinson,  A., 2016. Are historical sheep dipping baths in the Ribble Valley a source of arsenic pollution able to cause significant harm to human health? Available at: [Accessed 19th August 2019]
  7. Health and Safety Executive.2013. Agricultural Information Sheet No. 41. Sheep Dipping- advice for farmers and others involved in dipping sheep. [pdf] Health and Safety Executive. Available at: [Accessed 19th August 2019]
  8. Medical News Today. 2017. What are the symptoms of organophosphate poisoning? Available at: [Accessed 19th August 2019]
  9. The Guardian, 2018. Novichok nerve agents – what are they? Available at: [Accessed 19th August 2019]
  10. Agency for Toxic Substances and Disease Registry, 2003. Public Health Statement for Pyrethrins and Pyrethroids. Available at: [Accessed 19th August 2019]
  11. New Scientist, 1997. Sheep dips poison river life. Available at: [Accessed 19th August 
  12. The Ecologist, 2012. Ghosts of farming: Britain’s forgotten sheep farmers poisoned by pesticides. Available at: [Accessed 19th August 2019]
  13. The Guardian, 2015. MPs call for inquiry into sheep dip poisoning scandal. Available at: [Accessed 19th August 2019]
  14. Health and Safety Executive.2013. Agricultural Information Sheet No. 41. Sheep Dipping- advice for farmers and others involved in dipping sheep. [pdf] Health and Safety Executive. Available at: [Accessed 19th August 2019]
  15. Farming Life, 2016. Could mobile sheep dippers be the answer? Available at: [Accessed 19th August 2019]
  16. Farmer’s Weekly, 2018. Sheep dip permit cost hikes unjustified, say farm leaders. Available at: [Accessed 19th August 2019]
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Sep 3, 2019

Alice Shadwell