“They pointed to different parts of their bodies that had aged more than the rest and where they had health problems,” says Brown. “They knew all about which radioactive isotopes had lodged in their organs.” The other 288 women, they told her, had either died or had taken pensions for ill health.

In the weeks and months that followed the Chernobyl disaster, hundreds of thousands of firefighters, engineers, military troops, police, miners, cleaners and medical personnel were sent into the area immediately around the destroyed power plant in an effort to control the fire and core meltdown, and prevent radioactive material from spreading further into the environment.

These people – who became known as “liquidators” due to the official Soviet definition of “participant in liquidation of the Chernobyl nuclear power plant accident consequences” – were given a special status that meant they would receive benefits such as extra healthcare and payments. Official registries indicate that 600,000 people were granted liquidator status.

But a contentious report published by members of the Russian Academy of Sciences indicates that there could have been as many as 830,000 people in the Chernobyl clean-up teams. They estimated that between 112,000 and 125,000 of these – around 15% – had died by 2005. Many of the figures in the report, however, were disputed by scientists in the West, who questioned their scientific validity.

The Ukrainian authorities, however, kept a registry of their own citizens affected by the Chernobyl accident. In 2015 there were 318,988 Ukrainian clean-up workers on the database, although according to a recent report by the National Research Centre for Radiation Medicine in Ukraine, 651,453 clean-up workers were examined for radiation exposure between 2003 and 2007. A similar register in Belarus recorded 99,693 clean-up workers, while another registry including included 157,086 Russian liquidators.

In Ukraine, death rates among these brave individuals has soared, rising from 3.5 to 17.5 deaths per 1,000 people between 1988 and 2012. Disability among the liquidators has also soared. In 1988 68% of them were regarded healthy, while 26 years later just 5.5% were still healthy. Most – 63% – were reported to be suffering from cardiovascular and circulatory diseases while 13% had problems with their nervous systems. In Belarus, 40,049 liquidators were registered to have cancers by 2008 along with a further 2,833 from Russia.

The International Atomic Energy Agency, however, says that health studies on liquidators have “failed to show any direct correlation between their radiation exposure” and cancer or other disease.

Another group who bore the brunt of the radiation exposures in the hours and days after the explosion were those living in the nearby town of Pripyat and the surrounding area. It took a day and a half before the evacuation began and led to 49,614 people being evacuated. Later a further 41,986 people were evacuated from another 80 settlements in a 30km (18.7 mile) zone around the power plant, but ultimately some 200,000 people are thought to have been relocated as a result of the accident.

Some of those living closest to the power plant received internal radiation doses in their thyroid glands of up to 3.9Gy – roughly 37,000 times the dose of a chest x-ray – after breathing radioactive material and eating contaminated food. Doctors who have been studying the evacuees report that mortality among the evacuees has gradually increased, reaching a peak in 2008-2012 with 18 deaths per 1,000 people.

But this still represents a small proportion of the people affected by Chernobyl. 

Brown has found evidence hidden in hospital records from around the time of the accident that show just how widespread problems were.

“In hospitals throughout the region and as far away as Moscow, people were flooding in with acute symptoms,” she says. “The accounts I have indicate at least 40,000 people were hospitalised in the summer after the accident, many of them women and children.”

Viktor Sushko, deputy director general of the National Research Centre for Radiation Medicine (NRCRM) based in Kiev, Ukraine, describes the Chernobyl disaster as the “largest anthropogenic disaster in the history of humankind”. The NRCRM estimate around five million citizens of the former USSR, including three million in Ukraine, have suffered as a result of Chernobyl, while in Belarus around 800,000 people were registered as being affected by radiation following the disaster.

Even now the Ukrainian government is paying benefits to 36,525 women who are considered to be widows of men who suffered as a result of the Chernobyl accident.

As of January 2018, 1.8 million people in Ukraine, including 377,589 children, had the status of victims of the disaster, according to Sushko and his colleagues. There has been a rapid increase in the number of people with disabilities among this population, rising from 40,106 in 1995 to 107,115 in 2018.

Interestingly, Sushko and his team also report that the number of Chernobyl victims in Ukraine has decreased by 657,988 since 2007 – a fall of 26%. Although they don’t explain why, this is likely to be partly due to migration as victims have left the country, reclassification of victim status and, inevitably, some deaths.

Mortality rates in radiation contaminated areas have been growing progressively higher than the rest of the Ukraine. They peaked in 2007 when more than 26 people out of every 1,000 died compared to the national average of 16 for every 1,000.

In total some 150,000sq km (57,915 sq miles) of Belarus, Russia and Ukraine are considered to be contaminated and the 4,000sq km (1,544 sq miles) exclusion zone – an area more than twice the size of London – remains virtually uninhabited. But radioactive fallout, carried by winds, scattered over much of the Northern Hemisphere. Within two days of the explosion, high levels of radiation were picked up in Sweden while contamination of plants and grasslands in Britain led to strict restrictions on the sale of lamb and other sheep products for years.

In areas of Western Europe hit by Chernobyl fallout there have also been indications that the rates of neoplasms – abnormal tissue growths that include cancers – have been higher than in areas that escaped contamination.

But Brown believes some of the actions of those attempting to deal with the aftermath of the disaster also led to contamination spreading far further than it otherwise would. In an archive in Moscow she found records that indicated that meat, milk and other produce from contaminated plants and animals were sent all over the country.

“They came up with manuals for the meat, wool and milk industries to classify produce as high, medium and low in terms of radiation,” she says. “Meat with high levels, for example, was shoved into a freezer so they could wait until it fell. Medium and low-level meat was supposed to be mixed with clean meat and turned into sausage. It was labelled as normal and sent all over the country, although they were told not to send it to Moscow.”

Brown, who has written a book about her findings called Manual for Survival: A Chernobyl Guide to the Future, also discovered similar stories of blueberries that were over the accepted radiation limit being mixed with cleaner berries so the whole batch would fall under the regulatory limit.

It meant people outside Ukraine would “wake up to a breakfast of Chernobyl blueberries” without even knowing it, she says.

Establishing the links between radiation exposure and long-term health effects, however, is a difficult task. It can take years, even decades before cancers appear and attributing them to a particular cause can be difficult.

One recent study, however, identified problems in the genomes of children who were either exposed during the disaster, or were born to parents who were exposed. It found increased levels of damage and instability in their genomes.

“Genome instability represents a significant risk of cancer,” says Aleksandra Fučić, a genotoxicologist at the Institute for Medical Research and Occupational Health in Zagreb, Croatia. The daughter of a Ukrainian woman herself, she has been working with Russian scientists to study the effects of Chernobyl’s radiation on children from the region. “In Chernobyl cases, time is not healing. Time is a latency period for cancer development.”

There have been other impacts too, she says. Suicide rates among people involved in the clean up at Chernobyl are higher than in the general population. Studies have also found that people who reported living in the Chernobyl affected zones in Ukraine had higher rates of alcohol problems and poorer levels of mental health.

Putting a figure on exactly how many deaths around the world may result from the Chernobyl disaster is almost impossible. But despite the grim picture much of the research paints, there are some stories of hope too.

Three engineers who volunteered to drain millions of gallons of water from tanks beneath the burning reactor in the days immediately after the explosion waded through highly radioactive water and debris to reach the release valves. Their heroics are one of the most dramatic moments in HBO’s recent dramatisation of the disaster.

Astonishingly, two of the three men are still alivedespite having minimal protection from the radiation during their mission. The third man, Borys Baranov, survived until 2005.