British farmers are not often called hysterical. For Boris Johnson to dismiss their concerns over food imports post-Brexit seems to show he is willing to see an influx of cheap, low-quality food that British farmers will not be able to compete with. That would hasten the decline of family-run farms, and open up the countryside further to the sort of “megafarms” common in the US.

Cheap food sounds good, but Johnson has glossed over the dangers. Chlorine-washing chicken is partly an issue of animal welfare – poultry in the US are kept in filthy conditions that would be illegal here, then the carcasses are dipped in bleach. But it is one of food safety too, contrary to Johnson’s claims.

If the UK’s food standards are to be science-based, as he claims, they will have to account for science that shows the washing of chicken in chlorine only masks the presence of pathogens, rather than eliminating them. That leaves the harmful germs able to carry on infecting humans after the bleach treatment.

Q&A What is chlorinated chicken? Show Hide In the US, farmers are allowed to use chlorine washes and other disinfectants to remove harmful bacteria that may have infected chickens during rearing and slaughter. The EU banned the practice in 1997, leading to a long-running dispute over imports of chicken from the US. The US poultry sector has argued the ban in the EU is not based on science, but the EU is concerned that chlorine may compensate or mask poorer hygiene and animal welfare standards earlier in the food chain. The European Food Safety Authority has concluded that “chemical substances found in poultry meat are unlikely to pose an immediate or acute health threat to consumers”, but a team of microbiologists from Southampton University found in 2018 that some bacteria remained completely active after chlorine washing. Lisa O'Carroll, Brexit correspondent Photograph: Ludovic Marin/AFP

Johnson’s scientists will also have to explain why serious food poisoning is a greater problem in the US than the UK. For instance, the US reports about 420 deaths each year from salmonella, while Public Health England found none in its most recent labs data. “We would like some clarity from the prime minister about how exactly he intends to keep the UK population safe from food imported from countries with lower standards than our own,” said Kath Dalmeny, the chief executive of Sustain, the food and farming alliance.

Then there are the indirect impacts on human health, arguably much more alarming than food poisoning. Though the coronavirus may have come from wild animals, others such as swine flu and bird flu were associated with intensive livestock rearing.

Intensive farming also requires huge inputs of antibiotics, which are leading to the rapid evolution of antibiotic-resistant superbugs of the kind that may soon make even routine operations life-threatening.

Let the prime minister examine the science of intensive farming and food production: he will find little mumbo-jumbo and a lot to be worried about.