Suspected Iran schoolgirl poisonings: what scientists know

Iran’s government has arrested more than 100 people that it says are responsible for an unknown sickness that has affected potentially thousands of the country’s schoolgirls. Many are attributing the sickness to poisoning. As videos continue to emerge online of distressed young people being taken to clinics and hospitals, Nature spoke to toxicologists, chemical-weapons researchers, epidemiologists, political scientists and others to explore possible explanations.

What is the evidence that girls are being poisoned in schools?

Human-rights activists say one of the earliest cases reported in the media was at a school in the northern city of Qom in November 2022. Hundreds of videos have since been posted on social media of girls and young women reporting symptoms including fatigue, burning throats, nausea, headaches and numbness, sometimes experienced after smelling a variety of odours.

Iran’s interior minister Ahmad Vahidi is reported to have told state media on 5 March that “suspicious samples” were being analysed in laboratories. Iran’s supreme leader Ali Khamenei has called for a “serious probe”.

Mahmoud Azimaee, a data scientist based in Toronto, has been tracking incidents from media reports and news outlets since the end of November 2022. The overwhelming majority are in girls-only high schools (where students are aged 12 to 18). There are very few reported incidents in boys-only, or mixed schools. Cases are being reported across the country, but especially in the capital Tehran and in Qom, which is a centre for the study of Islamic theology and philosophy.

According to a toxicologist with knowledge of Iran, the government and researchers are collecting data but initial analyses are not robust enough to draw conclusions. Further results are likely “in the next few weeks”.

What toxic substances could be implicated?

Iran has so far not published official data other than the number of people who have fallen ill. Clinicians who have treated them are not providing public statements. This means any external interpretation of events is mostly reliant on secondary sources.

Alastair Hay, a toxicologist and chemical-weapons researcher at the University of Leeds, UK, says he has seen the results of blood tests from young people who have been hospitalized. However, it is not always possible to detect poisoning in this way, he says, because blood tests do not screen for different kinds of poison. A comprehensive toxicological screen and a representative number of cases are needed, he adds.

If a chemical was involved, a potential candidate would be chloramine, says Keith Ward, a chemist at George Mason University in Fairfax, Virginia, who has advised human-rights organizations in cases where chemical and biological weapons have been used in conflicts. Chloramine is produced by combining a cleaning product containing bleach with another containing ammonia. Its presence creates some (but not all) of the odours and symptoms being reported, Ward says.

Ward says other candidates, such as nerve gases and mustard gas, are less likely. Signs that nerve agents have been used would include an eye condition called pinpoint pupil, which is not being reported. Mustard gas has delayed effects after exposure and not the immediate reactions being reported, Ward adds.

What other explanations could there be?

Both Hay and Dan Kaszeta, a toxicologist at the Royal United Services Institute, a think tank in London working on military issues, are not ruling out the possibility of an episode of mass psychogenic illness. This arises from anxiety in response to fears of a threat or knowledge that a threat could be imminent. In Iran, this threat is real as the government has been arresting and imprisoning young people following nationwide protests after the death of Mahsa Amini, a student, while in custody in 2022. Girls and women have died as a result, according to Human Rights Watch and Amnesty International.

There have been previous cases in which fears of poisonings “have led to stress reactions such as fainting, nausea and hyperventilation”, says John Drury, a psychologist at the University of Sussex in Brighton, UK, who studies collective behaviour. The phenomenon¹ is thought to affect schoolchildren, often girls in countries where there is conflict. The World Health Organization has been recording incidents of mass psychogenic illness in Afghanistan since at least 2009, for example.

However, Drury says it is hard to distinguish between psychogenic effects and exposure to actual hazards, and that tests to determine the causes of physical symptoms should still be carried out.

Other researchers say it is too soon to be searching for psychogenic causes. Ali Arab, a statistician and epidemiologist at Georgetown University in Washington DC, says that a psychological phenomenon is “an absurd argument in this particular case”, given the abundance of video and photographic evidence showing physical symptoms.

Orkideh Behrouzan, a physician and medical anthropologist at the School of Oriental and African Studies (SOAS) in London agrees. “Bringing in a mass psychogenic hypothesis before having ruled out all physical causes is dangerous and misleading,” she says.

How should these events be investigated?

Researchers, human-rights groups and some governments say that an independent investigation is needed. Such an investigation would need the government to provide “access to health data, that are often extremely securitized in Iran”, says Behrouzan.

It could be carried out through the Organisation for the Prohibition of Chemical Weapons (OPCW), which is part of the United Nations Chemical Weapons Convention and based in The Hague, the Netherlands, in which Iran is an active member. A member state would need to put in a formal request for an investigation, which has not yet happened, an OPCW representative told Nature. But they added that the agency is closely monitoring developments in Iran.

A thorough investigation would include interviews with victims, toxicological tests, analyses of clinical histories, an epidemiological study and environmental sampling, according to researchers Nature has interviewed.

“I would like to see an open discussion, with the clinicians that saw the girls speaking freely,” says Ward. “You have to bring the community with you. Community involvement for something sensitive is crucial for people to believe in the findings,” adds Hay, who carried out a process of this kind to understand mass sickness in Kosovo around the time of the breakup of Yugoslavia into separate countries² in 1991.

Iran has enough trained experts and equipment to carry out toxicological investigations, says Hay. This capacity was built during and after Iran’s war with Iraq from 1980 to 1988, during which Iraq used chemical weapons.

If the cause is poison, who might be responsible?

On 11 November, Iran’s interior ministry announced that more than 100 people had been “arrested and probed” for shutting down classrooms using “smelly and harmless” substances, according to state media. The ministry said their motives were “mischief or adventurism” and hostile motives towards the government.

At the same time, some level of government involvement in these events, with the aim of stopping children from protesting, also cannot be ruled out, three researchers told Nature. After months of protests, the Islamic republic’s military and security apparatus may have concluded that poisoning is a way to punish those that have joined the protests, says Saeid Golkar, a political scientist who studies Iran at the University of Tennessee at Chattanooga.

If these are cases of poisoning, they “cannot happen without the approval of the government”, adds Encieh Erfani, a physicist formerly at the Institute for Advanced Studies in Basic Science in Zanjan, Iran. Erfani resigned in protest at the state’s violent repression of girls and women. At the same time, “there are those in the regime who feel girls should not be educated, so it is possible they are taking matters into their own hands”, says Ali Ansari, a historian of Iran at the University of St Andrews, UK.