Formalin and cancer at the University of Copenhagen: Facts and unanswered questions

How dangerous is it to be a medical student dissecting donated bodies as a student job? Can formalin, which is used to preserve the tissue they work on, cause cancer? And why have four young dissection instructors who worked at Panum between 2006 and 2012 developed cancer — three of whom have since died?

These are the questions raised by Danish national broadcaster DR in a TV documentary and podcast series called ‘The Toxic Doubt’ or Den Giftige Tvivl. The case has been covered in multiple media outlets, and the University of Copenhagen (UCPH) management has responded.

Here is what we know — and what we do not know — about the formalin case at the Faculty of Health and Medical Sciences.

The case in brief

Four former dissection instructors who worked in the dissection room while they were students at the Panum buildings of the Faculty of Health and Medical Sciences between 2006 and 2012 have developed cancer at a relatively young age. Three of them have since died.

DR has raised the question of whether their work in the dissection room — where they handled tissue preserved in formalin — may have played a role in their development of the disease.

The University of Copenhagen was first made aware of the cancer cases in 2019, when the Department of Occupational and Environmental Medicine at Bispebjerg Hospital contacted the university. This happened after a junior doctor, Kirstine Karnov, who had previously worked as a dissection instructor, was diagnosed with lung cancer and approached the department because she suspected there might be a connection. She died six months later.

What is formalin, and why is it used?

Formalin is an aqueous solution of formaldehyde and is used to preserve biological material, including human bodies that are donated to science and used in anatomy teaching in both the medical and dentistry programmes.

The dissection course is run by the Department of Cellular and Molecular Medicine (ICMM) and is a core component of the programme. Here, students learn what the human body actually looks like and how it can differ from textbook illustrations. It is typically senior medical students who work as dissection instructors.

Formaldehyde has been classified as carcinogenic for several years. In 2006, the substance was classified as carcinogenic for nasopharyngeal cancer, and in 2009 myeloid leukaemia (a type of blood cancer) was also included on the list from the International Agency for Research on Cancer (IARC), part of the World Health Organization. This means that strict regulatory requirements apply to its handling and exposure, and dissection instructors work with gloves and specialized ventilation systems.

Christian Budtz, who appears in the documentary, worked as a dissection instructor in 2006. He says in the programme that he would push the ventilation system away and sit with his head closer to the tissue in order to see better. Christian Budtz was diagnosed with Hodgkin lymphoma, a type of lymphatic cancer, in 2010.

What does UCPH say about safety?

UCPH emphasises that formalin is no longer handled directly in the dissection room itself. In a statement on KUnet, management explains that the donated bodies have since 2006 been rinsed with ethanol (alcohol), so that most of the formalin is removed before the bodies are brought into the dissection room. Management also writes that the concentration of formaldehyde in the embalming fluid has been reduced on several occasions.

UCPH states that exposure levels in the dissection room are significantly below the current exposure limits.

What did the 2019 investigation show?

The Department of Occupational and Environmental Medicine at Bispebjerg Hospital conducted an investigation based on Kirstine Karnov’s inquiry in 2019.

The conclusion at the time was that there was no documentation of a link between the cancer cases and the work in the dissection room, as these types of cancer (lung cancer, lymphoma and bowel cancer) do not appear on the WHO list of cancers associated with formaldehyde. At the same time, overall formalin exposure was deemed acceptable.

Neither Christian Budtz, nor the relatives of the three deceased young doctors, were contacted in connection with the investigation.

What do we know about the risks of formaldehyde and formalin?

International research shows that formaldehyde can be carcinogenic with prolonged exposure at high concentrations. The substance has been linked to cancers of the nose and throat, and in some studies also to myeloid leukaemia.

Neither lymphoma, lung cancer nor bowel cancer — which are the types of cancer the four affected doctors had — appear on the WHO list of diseases related to formaldehyde and formalin.

According to UCPH, dissection instructors are present in the dissection room for three to six hours at a time over four or eight days per semester.

Christian Budtz says in the documentary that it is typically a student job that you keep for a longer period, as it is both interesting and well paid.

What do we not know?

The central unanswered question is whether the four cancer cases in the basement are an occupational health issue — or a statistical coincidence.

In the documentary, the journalists emphasise that researchers who have expertise in this area are uncertain about which types of cancer can be attributed to formalin exposure. But several experts stress that four cancer cases among people who are under 35 years of age is very high.

There has been no investigation into how many people have worked as dissection instructors, how many have become ill, and whether this figure deviates from the incidence of disease in the general population.

This means that there is currently neither any documentation of a causal link — nor a comprehensive, independent analysis that can definitively rule out a causal link. In the documentary, UCPH declines to conduct an overall investigation into potential cancer cases among former dissection instructors.

UCPH acknowledges: Documentary has raised doubts

The Dean of the Faculty of Health and Medical Sciences, Bente Stallknecht, says she is deeply affected by the case and acknowledges that DR’s programmes may lead to uncertainty.

UCPH management writes on ku.dk [in Danish] that it has initiated a supplementary review of safety conditions with external assistance. It will contact both the Department of Occupational and Environmental Medicine and the Danish Working Environment Authority to clarify the next steps.

So where does the case stand?

The documentary makes clear that questions remain about the link between work in the dissection room and the cancer cases. On the one hand, we have four documented cases of cancer among young doctors who handled a substance classified by the WHO as carcinogenic. On the other hand, all relevant measurements of limit values for formalin have been complied with since 2006.

There is currently no basis for concluding that work in the dissection room was the cause of the cancer cases.

But neither is the case definitively closed. The new investigation may prove decisive in determining whether the doubts can be dispelled — or whether the working environment in the past needs to be examined further.

The Department of Occupational and Environmental Medicine reported Christian Budtz’s case as an occupational injury in 2025. But labour market insurance from the Arbejdsmarkedets Erhvervssikring has rejected granting Christian compensation.

What is the role of industry?

The documentary journalists interview researchers who are in disagreement over how dangerous formalin actually is. They also discover that industry and its lobby organisations have been active in trying to influence researchers to raise the limit values.

The journalists document how lobby organisations have had close ties to researchers and may have influenced research results on multiple occasions. This is relevant because the limit values for formaldehyde directly affect how much formalin students and staff are exposed to during teaching.

What should you do as a UCPH staff member or student?

The message from UCPH is that you should stay calm. Students at UCPH do not handle formalin directly in the dissection room, but they do handle tissue that has been fixed in formalin and rinsed beforehand.

According to ku.dk, this means that »the exposure to which students are subjected to is far below the limit values for formalin«. UCPH also assures us that it has complied with all relevant measurements of the Danish Working Environment Authority since 2006.

This article was first written in Danish and published on 26 February. It has been translated into English and post-edited by Mike Young.