Meat processed in this way is not believed to pose a risk for consumers, but the approach is widely opposed in the UK and is banned by the European Union. This is because it could potentially mask poor standards of hygiene and welfare in which poultry are raised.

The prospect of UK imports of chlorine-washed chicken, with its accompanying welfare issues, has been raised as part of a possible US-UK trade deal after Brexit.

Industry groups such as the Royal Society for the Prevention of Cruelty to Animals (RSPCA), RedTractor, and the British Poultry Council are opposed to chlorine-washed chicken.

“Acceptance of chlorine washing by consumers would signal that we are condoning lower welfare standards,” the RSPCA has said.

Alex Seguino, a Senior Lecturer and food safety expert at the Royal (Dick) School of Veterinary Studies (R(D)SVS), said: “There is little risk to the consumer from chlorinated chicken – there is more risk from drinking water, which we do every day in larger quantities.”

Dr Jessica Martin, a Senior Lecturer in Physiology and Animal Welfare at the R(D)SVS, added: “A big concern is that chlorine washing allows poor practices throughout the rearing period for chickens.

“This includes birds being crammed in together with minimal ventilation and lighting. These birds are bred to eat a lot, and therefore they excrete a lot, culminating in poor quality litter for them to live on.”

Controlling food poisoning

As chlorine rinsing is prohibited in the EU, producers must tackle potential disease risks to poultry through good hygiene and welfare. Research is ongoing to prevent contamination with bacteria that lead to food poisoning, such as Campylobacter and Salmonella, for example through carcass treatments, vaccination and selective breeding.

Campylobacter bacteria are commonly found in poultry, and can quickly reach large numbers in the chicken gut, which make their way onto the surface of the carcass during slaughter.

“It is so populous in the chicken gut that small numbers sufficient to cause human infections can easily contaminate the meat,” explains Professor Mark Stevens of the Roslin Institute.

“The best approach is to prevent or reduce the colonisation of chickens by Campylobacter as they are reared, as contamination of carcasses at slaughter can be hard to avoid.”

Research on the genetic make-up of broiler chickens – those bred for meat – has shown that it may be possible to breed birds with lower susceptibility to Campylobacter, while retaining commercially beneficial traits such as growth rate, efficient use of feed and gut health. Currently there are no effective vaccines against Campylobacter, and work on this is ongoing at Roslin.

“Campylobacter can spread rapidly within a flock from 2-3 weeks of age – there may be some maternal protection offered until this point, but research to mimic this protection with vaccines is proving challenging,” Professor Stevens said. The short life of chickens bred for meat also allows limited scope for vaccines to become effective.

Research on managing Campylobacter through additives to the diet – such as probiotic bacteria – has had limited success to date. Poultry diets are optimised for growth, which may enable Campylobacter to multiply; evidence is limited on whether different breeds are less impacted.

Keeping chickens indoors in controlled environments can limit their exposure to Campylobacter, which is found throughout the environment and can therefore affect free-range birds.

Salmonella, which is a key cause of food poisoning from poultry meat and eggs, can be controlled with vaccination but outbreaks still occur. Roslin research into the bacteria has determined the function of thousands of its genes during infection and assessed the risk of different strains, towards improved vaccine design.

Quality standards

“Poultry producers, processors and retailers are working hard to control Campylobacter along with other hazards,” said Mr Seguino. He is concerned that if the UK is forced to accept chlorinated chicken, consumers may buy it without realising its provenance.

“Supermarket shoppers may be able to choose unwashed chicken, but in food outlets and restaurants it is harder to choose,” he added.

Dr Martin opposes imports of chlorine washed chicken, and would support a labelling system to help consumers make informed choices, if it were to occur.

Chlorinated chicken products are not yet a reality for UK consumers, and the industry awaits developments regarding the possibility of imports from the US, and the impact on food production standards.

Dr Martin added: “My concern is that if the market is opened to chlorinated chicken and other low welfare practices, the UK and EU higher welfare standards of poultry production are at risk.

“The UK is one of the global leaders in animal welfare standards and protective legislation, but as always we should continue to strive in further improvement. The US has no federal regulations to protect poultry welfare – only state guidance and recommendations. The risk of importation would affect standards overall, jeopardise poultry welfare and penalise British producers.”