In a recent TikTok video, a youngish US woman demands to know, ‘Am I the only one who didn’t know this?’ She then tells of a visiting friend asking her why she’d bought a bag of lemons. The woman said she liked lemon in her water and for cooking. But why did you buy a bagful, repeated the friend. I just told you, the woman replied. But you have a lemon tree in your garden, with lemons, the friend queried. The woman replied, don’t they do something to them before they’re sold? No, said the friend, you can eat them straight from the tree. ‘Tell me I’m not the only one who didn’t know this,’ the woman asks the TikTok universe.

You can take a number of lessons from this – a regrettable remove from nature, a naive faith in authority – but surely there’s also a gobsmacking level of simple stupidity? For those who observe dumbness abounding (climate beliefs, gender nonsense, let’s eat insects), I offer the following thought: perhaps people are dumber than they used to be.

Many, if not most, top scientific experts have agreed that fluoride, a known neurotoxin, lowers IQ in children’s developing brains. The US started fluoridating water in 1945 and Australia in 1953, to curb tooth decay – which it did, by about one-third. The question in dispute is the level of fluoride that’s harmful. Australia and the US fluoridate water to around 0.7 milligrams per liter, while levels of 1.5 mg/L have been found to be neurotoxic. Most Western European countries, such as France, Germany, Italy, Sweden and Switzerland, have rejected water fluoridation, amid concerns about health effects, and one’s right not to have a medical treatment.

A long-awaited, drawn-out and landmark court case against the US Environmental Protection Agency (EPA) has now put these issues to the test. Duelling experts with competing studies fought it out over two weeks in February in a San Francisco federal court trial; a finding is awaited on whether fluoride poses an ‘unreasonable risk’. Environmental groups’ suit to ban US water fluoridation due to toxic effects on children’s developing brains began way back in 2017, but was delayed pending a multi-year government agency review of available fluoride research – the National Toxicology Program (NTP) report. It took a subpoena to finally get the report out, because its conclusions are damning. In early 2023 the report revealed a higher fluoride exposure of around or above 1.5mg/L is consistently associated with lower IQ in children, and that there was no apparently safe level of exposure. A stunning 52 of 55 studies found lower IQ with higher fluoride exposures. The report also ran a graph showing that fluoride of 0.7mg/L (Australia’s level) was associated with a 3 point drop in IQ; at 1.5mg/L the drop is 6 points. For context, the NTP report noted that a five-point drop in a population’s IQ would nearly double the number of people classified as intellectually disabled. During the trial the EPA’s risk assessor, Stanley Barone, conceded that fluoride was neurotoxic at relatively low levels.

The scientific history of fluoride’s effect on teeth dates back to 1901, when young dentist Dr Frederick Mckay moved to Colorado Springs, and began investigating Colorado Brown Stain, a localised heavy staining on teeth so severe that some teeth, while strong, were chocolate in color. A high level of natural fluoride in water supplies turned out to be the cause, of both the staining and the strong tooth enamel. By 1945 Grand Rapids became the first US city to fluoridate its water. Around 200 million Americans now have fluoridated water, as do around 90 per cent of Australians.

However, additives in public water supplies are not the only source of fluoride. Fluoride can enter water and plant systems in varying amounts from local rocks and soil while industrial emissions can also contaminate water supplies.

Fluoride can also come from almost all foods, especially seafoods which can have levels up to 7 mg/L. These days we also have fluoridated toothpastes, and dental applications. Thus 0.7mg/L in drinking water is not total fluoride exposure, but simply a base level, and of course individual vulnerabilities would differ.

The EPA argues that research on safety levels is too uncertain to merit a policy change. The necessary work has not been done. However, four of the experts who testified against the EPA in this case have worked with the EPA in the past on setting hazard levels for toxins such as lead and mercury. Harvard professor Philippe Grandjean told the court that the most vulnerable populations to neurotoxicity are pregnant mothers and babies. Another expert said that babies fed with formula made from fluoridated water showed lower IQs later in life than breast-fed babies.

Such has been the level of political conflict in this case that a freedom of information application was launched to prise out internal emails from the now-retired former NTP scientific director, Dr Brian Berridge. In them he expressed concerns that commercial and stakeholder interests were seeking to modify the NTP report ‘to fit commercial interests’. The NTP is a government agency within the Department of Health and Human Services. Berridge also criticised public health agencies for wanting to protect their existing practices, which he said explained both the lack of key research on fluoride exposure and the difficulty in getting the report out.

These days, dentists like to paste fluoride straight on to one’s teeth, because fluoride’s primary mechanism for preventing tooth decay is through topical contact, not ingestion, as previously thought. So there’s no reason to have to drink it in your water, when you can get it more effectively from dentists and toothpastes.

The whole debate echoes Covid-era disputes, with suppressed research, political interference and authorities insisting it’s all safe and effective. Queensland is something of a ground zero with a reported 51 out of 77 local councils not having fluoridated water, many having opted out after the Newman government made it optional in 2012. Some Queensland areas also have high naturally occurring fluoridated water. But our medical controllers, dentists and doctors, want fluoride mandated, with an Australian Medical Association spokesman describing it as a human right. You may want to play safe and drink filtered water, while getting fluoride from the dentist, until these issues are resolved.