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Scientists comment on hormone-treated beef and chlorinated chicken, following the announcement of a UK-US trade deal.
Beef
Prof Chris Elliott, Chair of Food Safety, Queen’s University Belfast (QUB), said:
“There are a number of hormones, mainly anabolic steroids that are classified as growth promoters. They were banned in the EU back in the 1980’s on the grounds they were a food safety risk. This has been hotly disputed by the US and other countries that use the hormones in livestock production.
“The bulk of the scientific evidence suggests they are safe if used correctly. However incorrect use (as can happen accidently or deliberately) could pose health issues.
“The big issue is that use of such hormones is not ‘natural’ – but again this is widely disputed as livestock have many things added to their diets to enhance growth rates.
“Testing for the presence of the hormones can be done but it’s extremely difficult and requires very expensive equipment and the cost per test would runs into many hundreds of pounds. There has previously been evidence that meat claimed as ‘hormone free’ was in fact treated with anabolic steroids.”
Chicken
Prof Paul Wigley, Professor in Animal Microbial Ecosystems, University of Bristol, said:
“The use of high-concentration chlorine washes applied in the USA and other countries is adopted as a relatively simple and low-cost method to reduce foodborne bacterial pathogens such as Salmonella from chicken carcasses. Its efficacy is questionable. Rates of human Salmonella infection in the USA are around double the European average and around five times greater than in the UK.
“The UK approach is to control on the farm with the use of vaccines, good biosecurity and hygiene together with regular testing for Salmonella, accompanied by far greater levels of animal welfare that were set down by EU legislation and still adopted in the UK. Salmonella is in effect eradicated in UK Lion Mark eggs and is uncommon in UK-produced poultry meat.
“An analogy is going out for a walk as seeing a pile of dog muck. The UK/EU approach is to avoid getting it on your shoes. The American approach is wiping it off when you get home but we all know that some will remain trapped in the tread.
“The ban on US produced chicken on public health grounds is justified when simply looking at the figures of public health impact. Human Salmonella infection often leads to hospitalisation and most recent figures indicate there were 33 deaths resulting from Salmonella in the UK in 2013. We cannot ban on welfare grounds but there is a clear public health reason to do so.”
Beef and chicken
Dr Elisa Pineda, Research Fellow in Nutritional Epidemiology and Food Policy at the George Institute for Global Health UK, Imperial College London, said:
“Hormone-treated beef refers to cattle administered synthetic or natural growth hormones, such as oestradiol or trenbolone, to accelerate muscle development and reduce the time to market. Chlorinated chicken involves washing poultry carcasses in chlorine-based solutions to reduce surface bacteria. From a food systems perspective, these are technological ‘end-of-pipe’ interventions, often used to compensate for intensive production practices rather than addressing upstream hygiene or welfare.
“These practices are banned in the UK under longstanding EU-originated food safety regulations, which emphasize a ‘precautionary principle.’ The bans are partly rooted in health concerns, but also reflect ethical and consumer preference standards that prioritize transparency and animal welfare.
“The scientific debate around health impacts continues, but from a nutritional epidemiology perspective, even low-level exposures to hormone residues raise legitimate concerns, particularly in vulnerable populations. The evidence is inconclusive but not absent regarding links to endocrine disruption and cancer risk. With chlorinated chicken, the issue is less about the chlorine itself and more about what its use permits—namely, intensive, low-welfare rearing environments. These production systems are often less sustainable, contributing to antimicrobial resistance, lower nutrient density, and degraded trust in food governance.
“Both practices are indicators of poorer standards than are currently applied in the UK. Hormone use in beef can lead to faster growth but is associated with higher rates of metabolic and joint disorders in cattle. Chlorinated chicken is typically produced in high-density, industrial systems with minimal welfare standards—something UK consumers and policy frameworks have explicitly rejected. These practices are misaligned with emerging global benchmarks for food systems that are health-promoting, sustainable, and equitable.
“Beef testing can detect synthetic hormone residues using analytical techniques like liquid chromatography-mass spectrometry. However, enforcement is complex and resource-intensive. From a food policy perspective, it’s more effective to regulate practices at the production level rather than relying solely on testing to catch non-compliance. That’s especially important if we want to build resilient food systems that support population health and planetary boundaries.
“As a public health expert working at the intersection of nutrition and food policy, I see this trade deal as a critical juncture. While it’s positive that UK standards on hormone-treated beef and chlorinated chicken have been upheld, we must remain vigilant. Trade policy has profound implications for food environments and, over time, influences dietary patterns, chronic disease risk, and the resilience of our food systems. A truly forward-looking trade policy must safeguard not only markets or value economic exchange alone, but also prioritise the long-term well-being of populations, animal health, and ecosystems.
“At the same time, to mitigate climate change and promote sustainable diets, we must shift focus toward predominantly plant-based diets. For those who choose to consume meat, opting for locally produced, high-welfare meat can support environmental goals and strengthen regional food systems.”
Prof Guy Poppy, PVC Research and Innovation, University of Bristol, said:
On chlorine-washed chicken:
“The use of chlorine washes to ensure chickens are safe to eat is a difference between how the USA and the EU/UK regulate food. The USA uses product-based approach while the EU and UK use a process-based one – i.e. consideration of the process we use to ensure safety rather than the end outcome. If done correctly the end product, chicken, is equally safe, but the system we currently use involves several steps in how chickens are produced throughout the rearing and preparation of the chicken for sale – as opposed to the USA system which uses chlorine to ‘disinfect’ the chicken prior to retail. Both systems are used to reduce/eliminate the number of microorganisms in the chicken which can make us ill.
“Many of the biosecurity processes used in the UK can also enhance welfare, such as practices to reduce the levels of pathogens in chickens – as opposed to being reliant on a system of using chlorine to reduce the pathogens after slaughter.”
On hormone-treated beef:
“There are significant disagreements between the EU and the US on the health issues of hormone treated beef. Whilst the EU claim that one of the regularly used hormones is carcinogenic, the US and Canada claim to the WTO that the EU risk assessment is flawed. And several of the hormones used do not have any health claims against them. However, the rearing practice which is involved in accelerating growth can be seen as an animal welfare issue as weight gain and the feedlots and other practices to reduce feed requirements and accelerate growth result in much lower animal welfare than rearing systems not involving hormones or feedlots.
“Both of these types of animal food production illustrate different rearing systems and methods to control risk. If done correctly and with checks in place, they both result in a safe product but there are differences in the animal welfare outcomes of the production systems used in the US compared to the UK/EU. The US style production systems can lead to reduced costs and increased profits and thus I can see why UK farmers are concerned about the effects this may have on the current UK meat system. It is clear that the current UK food system needs transforming to improve human and environmental health, but I am not sure this is a direction of travel which will help that.”
Declared interests
Paul Wigley: I have and continue to receive funding from UKRI around this area but no current or recent work with industry in these areas
Chris Elliott: No interests to declare
Guy Poppy: CSA at the FSA 2014-2020, Exec Chair at BBSRC 2023-2024
Elisa Pineda: None
For all other experts, no reply to our request for DOIs was received.