Woody Johnson, the US ambassador to the UK, stirred the Brexit pot on 1 March by writing in defence of growth hormone treated cattle and ‘chlorinated chicken’, products banned by the EU.

The growth hormone dispute between North America (Canada sides with the US) and Europe began in the 1980s. An EU ban on hormone-raised beef led to the US imposing retaliatory tariffs in 1989 on EU foods, including truffles, chocolates and Roquefort cheese. In 1997 the WTO ruled that the EU beef ban was unfair and discriminatory. The EU did not budge, and in 1999 the WTO ruled that it was right for the US to seek compensation. Before the ban most US bovine meat exported to Europe was offal destined for pet food. Hundreds of millions have been spent in attempts to resolve the dispute.

The scientific evidence that hormone-raised beef is harmless is strong, as far as it goes. The precautionary principle is at the heart of this dispute. It is enshrined in the 1993 Maastricht Treaty. In 2000, the EU Commission said that the principle applies when ‘scientific information is insufficient, inconclusive or uncertain or where there are indications that the possible effects … may be potentially dangerous.’ The principle has no formal legal status in the US. That is not to say that it is not applied. The US banned haggis from Scotland in 1971 because it contains sheep lung, and British beef and lamb in 1989 because of BSE.

‘Chlorinated chicken’ is pejorative. Chlorine gas doesn’t come into it. The meat isn’t bleached. Poultry carcasses are washed with dissolved antimicrobials such as sodium chlorite, chlorine dioxide and trisodium phosphate. The US calls the practice Pathogen Reduction Treatment (PRT). The EU banned it in 1997, not because the washes leave the meat dangerous to eat – the European Food Safety Authority has said that PRT poultry is safe – but because it might incentivise poultry producers and processors to give hygiene a lower priority. This argument was used in the 1930s by opponents of milk pasteurisation. Evidence supporting it is still lacking.

Also lacking is evidence that US food is less safe microbiologically than European. For some food poisoning bacteria, the converse could be true. Campylobacter infections have very strong links to poultry consumption. It contaminates the carcass surface and is one of the main targets of PRT. The most recent figures (2016) for England and Wales were 89.72 lab-confirmed cases per 100,000 population. In the EU as a whole it was 66.3/100,000; in the US it was 17.43/100,000. Estimating the real number of Campylobacter cases is difficult, because most people who are infected don’t seek medical advice, don’t have diagnostic tests, and so don’t get counted in the statistics. Another problem is that nearly all cases occur singly, not in outbreaks, and so don’t provide easy meat for lawyers.

The growth hormone and PRT quarrels have been primarily political. Science has been sidelined. But that doesn’t mean that Brexit and Britain’s ‘special relationship’ with the US will transport us to the sunlit uplands.

The HACCP (Hazard Analysis and Critical Control Points) system, the worldwide food safety law adopted by the WHO-FAO Codex Alimentarius Commission, was developed by the US Army, the Pillsbury Company and Nasa to prevent astronauts getting diarrhoea in zero gravity. The US has been keener on it than the UK. Failure to implement it lay behind the enormous E.coli O157:H7 outbreak (17 deaths) in central Scotland in 1996. In my report on it not only did I recommend the ending of the UK ‘light touch’ approach to HACCP implementation, but said that the EU should get on with it as well, and that the UK government should seek to have HACCP enshrined in EU food safety directives. It is a reasonable guess that any regulatory relaxation on our part post-Brexit would be jumped on by the US in trade talks about food and drink. Stopping the import of our germs would protect their producers as well as their consumers.