Fluoride has been in most American tap water for decades. It’s there to help to prevent tooth decay, especially in children. Scientists and health officials say it’s one of the biggest public health wins of the 20th century.

But lately, fluoride has found itself at the centre of a heated debate, with some people concerned about side effects. Robert F Kennedy Jr, the US Health Secretary, is one of those, but he has long expressed views that conflict with scientific evidence.

We break down the facts about fluoride, explain how the quantities of it in water is safe and tell you what you need to know with Phoebe Hopson, a BBC reporter, and Michelle Roberts, a doctor and health reporter.

Instagram: @bbcwhatintheworld Email: [email protected] WhatsApp: +44 0330 12 33 22 6 Presenter: Hannah Gelbart Producers: Julia Ross-Roy and Emily Horler Editor: Verity Wilde

Over 500 schools and universities in South Korea are dealing with a deepfake porn crisis. Explicit images and videos of classmates and teachers are being shared. The perpetrators are often students themselves. In fact, 80 per cent of those arrested for creating and distributing deepfakes are teenagers.

Hyojung Kim from the BBC’s Korean Service explains what’s happening and what’s being done to stop it.

Plus, presenter and campaigner Jess Davies gives us tips on what to do if you have been deepfaked.

If you’ve been affected by any of the issues raised in this episode and you are based in the UK, you can get support from relevant organisations through the BBC Action Line website: https://www.bbc.co.uk/programmes/articles/22VVM5LPrf3pjYdKqctmMXn/information-and-support-sexual-abuse-and-violence.

Instagram: @bbcwhatintheworld Email: [email protected] WhatsApp: +44 0330 12 33 22 6 Presenter: William Lee Adams Producers: Julia Ross-Roy, Elena Angelides, Benita Barden and Adam Chowdhury Editor: Verity Wilde

The annual World Happiness Report is out and Finland has been named the happiest country for the eighth year in a row.

What makes the Finns so joyful? Emilia Jansson from the What in the World team breaks it down for you.

But, is happiness just a fleeting emotion or is there more to it? Sarah Jelbert, a lecturer who teaches courses on the science of happiness explains how you can improve your life satisfaction.

And we hear from Sweden and Costa Rica, two countries that rank in the top ten.

Instagram: @bbcwhatintheworld Email: [email protected] WhatsApp: +44 0330 12 33 22 6 Presenter: Hannah Gelbart Producers: Emily Horler and Maria Clara Montoya Editor: Julia Ross-Roy

Netflix has a TV show out called Apple Cider Vinegar - it’s a dramatisation of a real story of a real influencer who was popular online, and said she was treating a terminal illness with alternative therapies. But it turned out the supposed natural treatments she was promoting didn’t do anything, because she didn’t really have brain cancer.

So it got us thinking - how can you spot false wellness claims?

Drinking special tea to make you slimmer. Rubbing bee venom on your face to reduce fine lines and wrinkles. Inserting gemstones into your vagina to regulate menstrual cycles. These are just three on the seemingly endless list which have little to no scientific evidence to support their purported benefits.

Jacqui Wakefield, a reporter with the BBC’s Global Disinformation Unit, takes us through what makes these trends take off and how we can spot the bad ones online. Makuochi Okafor in our Lagos bureau explains what wellness scams look like in Nigeria. And Maria Clara Montoya tells us about the scene in Latin America.

Instagram: @bbcwhatintheworld Email: [email protected] WhatsApp: +44 0330 12 33 22 6 Presenter: William Lee Adams Producer: Emily Horler Video Journalists: Benita Barden and Adam Chowdhury Editor: Verity Wilde

Imagine going on a work or school trip for eight days, but ending up away from home for nine months. Now, imagine that journey was to space. NASA astronauts Suni Williams and Butch Wilmore’s spacecraft launched in June last year from Cape Canaveral in Florida. They were taking part in the first crewed test flight of the Starliner spacecraft, developed by Boeing. But there were some technical problems after launch and NASA decided it was too risky to use it to take the astronauts back to Earth. Instead, Suni and Butch would catch the next scheduled flight home, which ended up being nine months later. And now Suni and Butch have splashed down off the coast of Florida in a different spacecraft.

Our Science Editor, Rebecca Morelle, explains what went wrong with the mission, if they were really stranded, and what daily life is actually like in space.

Instagram: @bbcwhatintheworld Email: [email protected] WhatsApp: +44 0330 12 33 22 6 Presenter: Hannah Gelbart Producers: Emily Horler and Elena Angelides Editor: Verity Wilde

On Sunday night, hundreds of people gathered at Pulse nightclub in Kocani, North Macedonia to watch the popular hip-hop duo DNK perform. It ended in tragedy. A fire ripped through the venue killing 59 people and leaving more than 150 others injured.

Reports say the fire was caused by sparks from pyrotechnic devices that hit the ceiling, which was made of highly flammable material. The incident has raised questions about how the venue was able to operate with inadequate safety measures, and if corruption has a role to play.

We speak to Saska Cvetkovska, an investigative journalist in Skopje, about what we know so far and how the country is coping with the aftermath of the tragedy.

Instagram: @bbcwhatintheworld Email: [email protected] WhatsApp: +44 0330 12 33 22 6 Presenter: Hannah Gelbart Producers: William Lee Adams and Benita Barden Editor: Verity Wilde

Taylor Swift fans were gathering in Vienna in August last year, when organisers announced her three-night run would be cancelled, due to a terror threat. Three teenagers were arrested, accused of plotting an attack which was allegedly inspired by the Islamic State group. Speaking at a news conference, an Austrian politician said that “a tragedy was prevented.”

This sits within a wider picture of people behind acts like this getting younger. Although the numbers aren’t huge, in Europe last year, 1 in 5 terror suspects were under the age of 18. In the UK, it was double that. This data comes from a report written by Thomas Morgan, from the Institute for Economics and Peace in Australia. He joins the podcast to talk about the rise in radicalisation amongst young people.

We are also joined by Julian, a counsellor who works with teenagers in Berlin who have been radicalised by far-right ideology. He tells us how sessions run by Violence Prevention Network aim to change attitudes and behaviours of radicalised young people. Instagram: @bbcwhatintheworld Email: [email protected] WhatsApp: +44 0330 12 33 22 6 Presenter: Hannah Gelbart Producers: Emily Horler, Elena Angelides and Julia Ross-Roy Editor: Verity Wilde

The Saudi Public Investment Fund (PIF) has agreed to pay $3.5 billion to buy the gaming division of Niantic, the Pokémon Go publisher. It’s the latest in a string of entertainment and gaming investments by the PIF. BBC tech reporter Tom Gerken tells us why the Saudi government is spending billions on gaming and what the Kingdom stands to gain from it.

Plus: BBC Arabic’s Abdirahim Saaed explains where the PIF gets its money and why the gaming scene is so big in Saudi Arabia right now.

Instagram: @bbcwhatintheworld Email: [email protected] WhatsApp: +44 0330 12 33 22 6 Presenter: Hannah Gelbart Producers: William Lee Adams and Benita Barden Editor: Julia Ross-Roy

An estimated 700 million people visit zoos every year. Some people see these facilities as a great way to teach people about nature and to save species from extinction. Others think they’re cruel and unnecessary. It’s a heated debate. And now, as more and more people are watching animal rescue videos on Instagram and TikTok, it feels like the debate is hotter than ever.

William Lee Adams from the What in the Word team talks us through the history of zoos, including how England's Queen Charlotte (who was featured in Netflix’s Bridgerton) came to have twenty kangaroos, and how zoos have evolved. We also discuss their pro and cons. We hear from Tonya Lander, a biology lecturer at the University of Oxford in the UK, 19 year old animal rights activist Nikita Dhawan, and Delcianna Winders, Director of the Animal Law and Policy Institute at Vermont Law and Graduate School in the US.

Instagram: @bbcwhatintheworld Email: [email protected] WhatsApp: +44 0330 12 33 22 6 Presenter: Hannah Gelbart Producers: Mora Morrison and Elena Angelides Video Journalist: Adam Chowdhury Editor: Verity Wilde

In November, fifteen people were killed at the Novi Sad railway station in Serbia when a concrete canopy collapsed. Students in the country have been protesting ever since, claiming that government corruption contributed to the tragedy. The protests have brought the country to a standstill, and on Monday students occupied the public TV station RTS. Slobodan Maričić from BBC Serbian tells us about the student protests, what he’s seen when out reporting and the criticism faced by President Aleksandar Vučić.

We also hear from several student protestors and Konstrakta, a popular singer. She explains why students have been so effective leading and organising the protests and how their movement has expanded to include people of all ages.

Instagram: @bbcwhatintheworld Email: [email protected] WhatsApp: +44 0330 12 33 22 6 Presenter: Hannah Gelbart Producers: William Lee Adams, Emilia Jansson and Benita Barden Editor: Verity Wilde

Two weeks ago $1.5 billion vanished from a cryptocurrency platform - it’s thought to be the biggest crypto heist ever. They had fallen into the hands of some infamous hackers - the Lazarus Group. These hackers have alleged ties to the North Korean government and have managed to steal huge amounts of money from other crypto platforms before.

The BBC’s Cyber Correspondent, Joe Tidy, takes us through all the details and explains why North Korean hackers are so untouchable.

Instagram: @bbcwhatintheworld Email: [email protected] WhatsApp: +44 0330 12 33 22 6 Presenter: Hannah Gelbart Producers: Emily Horler and Emilia Jansson Editor: Verity Wilde

Plastic pollution has been highlighted as an environmental issue for several years. But experts are now researching whether it poses a potential danger to our health. Microplastics specifically are found in our bodies - even in our brains.

The BBC health reporter Smitha Mundasad explains to us what they are and whether we should be worried. And 25-year-old microplastics researcher and influencer Dana Zhaxylykova shares her top tips on how to avoid plastics.

Instagram: @bbcwhatintheworld Email: [email protected] WhatsApp: +44 0330 12 33 22 6 Presenter: Hannah Gelbart Producers: Mora Morrison and Emilia Jansson Editor: Verity Wilde