Chlorinated chicken: How safe is it?
Fears over chlorine-washed chicken and other US farming practices have been described by US ambassador to the UK Woody Johnson as "inflammatory and misleading".
Mr Johnson urged the UK to embrace US farming methods after Washington published its objectives for a UK-US trade deal. He said the process was used by EU farmers to treat vegetables, and that it was the best way to deal with salmonella and other bacteria.
So is it safe? The evidence suggests the chlorine wash itself is not harmful. But the concern is that treating meat with chlorine at the end allows poorer hygiene elsewhere in the production process.
Why ban chlorine-washed chicken?
Washing chicken in chlorine and other disinfectants to remove harmful bacteria was a practice banned by the European Union (EU) in 1997 over food safety concerns. The ban has stopped virtually all imports of US chicken meat which is generally treated by this process.
It's not consuming chlorine itself that the EU is worried about - in fact in 2005 the European Food Safety Authority said that "exposure to chlorite residues arising from treated poultry carcasses would be of no safety concern". Chlorine-rinsed bagged salads are common in the UK and other countries in the EU.
But the EU believes that relying on a chlorine rinse at the end of the meat production process could be a way of compensating for poor hygiene standards - such as dirty or crowded abattoirs.
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Instead, the EU says the best way to eliminate the risk of salmonella and other bacteria is to maintain high farming and production standards.
The European Commission says: "This rule is part of wider EU legislation ensuring a high level of safety throughout the food chain, from farm to fork."
The US has voiced frustration, saying the ban is not based on scientific evidence. It even tried to bring a case before the World Trade Organization in 2008.
Does US meat have more harmful bacteria?
The US Department of Agriculture's (USDA) National Antimicrobial Resistance Monitoring System tests samples of raw chicken from shops for bacteria.
In its most recent round of testing it found a significant amount of the bacteria campylobacter - the most common cause of food poisoning - in 30% of chicken carcasses, 26% of chicken parts and 58% of "mechanically separated" chicken, which is used to make things like chicken nuggets.
It recorded how much of the chicken had more than 400 units of bacteria per gram of meat.
In the UK, the government's Food Standards Agency found 54% of chickens had traces of the bacteria but only 6% had the highest levels - more than 1,000 units of bacteria per gram of meat.
Since they don't measure exactly the same thing, it's difficult to compare these results.
There is evidence that chlorine kills more bacteria on chicken than plain water does - but some studies have suggested it does not kill all bacteria.
A study from the University of Southampton last year found that chlorine could make food-borne pathogens undetectable, giving lower microbial counts in testing, but without actually killing them - so they might remain capable of causing disease.
They tested chlorine-washed strains of food-borne bacteria on roundworms and all of them died.
The World Health Organization has also cast some doubts over how much bacteria chlorine kills, and studies of its effectiveness have had mixed results.
So is food poisoning more common in the US?
The US government's Centers for Disease Control and Prevention says there are about 1.3 million illnesses from campylobacter and 1.2 million illnesses from salmonella a year, affecting about 0.4% of the population.
It's based on information from infection surveillance centres in 10 states. That sample is used to give an estimate for the whole country.
Across the UK in 2017, there were 63,946 confirmed cases of infection from campylobacter and 10,089 infections from salmonella, equating to 0.1% and 0.02% of the population respectively. Those figures are the actual number of confirmed reports around the UK, not estimates.
The death rate from salmonella in the US is far higher than in the UK, where fatalities are rare. In the US, the CDC estimates there are 450 deaths from salmonella a year.
Lots of people also don't go to their doctors with symptoms of food poisoning, so in both the US and the UK only the more severe cases of food poisoning will come to the attention of authorities.
It may be that a higher proportion of people are infected but only certain groups - the very old and young, for example - will actually end up being diagnosed and treated.
Not all food poisoning is from meat, though - although poultry is the most common cause - and not all food poisoning is down to the production process. Some bacteria will generally be left on the skin of a chicken so the care with which it's handled and cooked at home are extremely important.