Kristian Dreij

Kristian Dreij

Principal researcher

Group leader and researcher at the Institute of Environmental Medicine, Karolinska Institutet.

About me

Kristian Dreij received his Ph.D. degree in Toxicology in 2005 from the lab of biochemist Bengt Jernström at Karolinska Institutet (KI). In 2006 he joined as a post doc in the lab of molecular biologist David Scicchitano at New York University. In 2009 he was recruited to the group of Professor Ulla Stenius, KI as a post-doctoral fellow focusing on genetic toxicology. 2012 he was awarded a Junior Researcher project grant from the Swedish Research Council VR to start a group focused on the biological effects of transcriptional mutagenesis at the Institute of Environmental Medicine, KI. In addition, his group is investigating if mixture effects can contribute to the genotoxic and carcinogenic effects of environmental pollutants, and how this could be included in risk assessment. Kristian became Docent/Associate Professor in Toxicology at KI in 2016.

Kristian is also deputy program director of the global Master's Programme in Toxicology at Karolinska Institutet.

Research description

There are two main projects in the lab. 

Biological consequences of transcriptional errors induced by DNA damage.

When a DNA-damage is bypassed during transcription this can lead to RNA misincorporation, a process termed transcriptional mutagenesis (TM). Although the concept of TM is well known, the biological consequences are still a recent discovery. While the few existing studies of TM have begun to shed light on the process, many issues have yet to be addressed. The extent, to which TM occurs in mammalian cells and the role these seemingly transient errors might play in disease processes such as carcinogenesis, is currently unknown. Current theories postulate that the transient expression of mutant proteins via TM could play a major role in tumor development by stimulating proliferation of a senescent initiated, precancerous cell or allowing it to escape growth-inhibitory apoptotic signals and undergo clonal expansion. In order to characterize each of these events, a  unique approach has been developed for studying the occurrence and potentially detrimental effects originating from TM.

Recent publications:

Transcriptional mutagenesis dramatically alters genome-wide p53 transactivation landscape. Liang S, Ezerskyte M, Wang J, Pelechano V, Dreij K. Sci Rep. 2020;10(1):13513

O6-methylguanine-induced transcriptional mutagenesis reduces p53 tumor-suppressor function. Ezerskyte M, Paredes JA, Malvezzi S, Burns JA, Margison GP, Olsson M, Scicchitano DA, Dreij K. Proc. Natl. Acad. Sci. U.S.A. 2018;115(18):4731-4736

Transcriptional mutagenesis reduces splicing fidelity in mammalian cells. Paredes JA, Ezerskyte M, Bottai M, Dreij K Nucleic Acids Res. 2017;45(11):6520-6529


Contribution of interaction effects to the carcinogenicity of environmental pollutants.

The goal of this project is to investigate the harmful effects of exposure to complex mixtures of PAHs and pesticides, and to improve the scientific base for risk assessment of human exposure to complex environmental mixtures. The methods commonly used for assessing the toxicity of complex environmental mixtures probably significantly underestimate the risk of exposure to human health since they do not take into account interactions which potentially give rise to synergistic effects.

In the PAH project we study the effects of complex mixtures using environmental samples on DNA damage and repair, inflammation and development. Samples are obtained from urban air particulate matter and soil collected at urban as well as industrial locations. The test systems we use are human cell lines and zebrafish embryos. Our published data indicate that complex environmental PAH mixtures induce unexpected and persistent DNA damage.

In the pesticide project we are conducting a cross-sectional study among the Bolivian agricultural population. In Bolivia, farmers have increased the use of pesticides to enter into a more competitive international market. There is little or no social protection which together leads to hazardous working conditions for the farmers. To evaluate and study the correlation between exposure to pesticides and risk of developing genotoxic effects we use questionnaire information and blood and urine analysis. 

Recent publications:


Polycyclic aromatic compounds in particulate matter and indoor dust at preschools in Stockholm, Sweden: Occurrence, sources and genotoxic potential in vitro.  Lim H, Sadiktsis I, de Oliveira Galvão MF, Westerholm R, Dreij K. Sci Total Environ. 2021;755:142709

Mixture effects of oxygenated PAHs and benzo[a]pyrene on cardiovascular development and function in zebrafish embryos. Cunha V, Vogs C, Le Bihanic F, Dreij K. Environ Int. 2020;143:105913

Polycyclic aromatic compounds in urban soils of Stockholm City: Occurrence, sources and human health risk assessment. Dreij K, Lundin L, Le Bihanic F, Lundstedt S Environ. Res. 2020;182:108989


In vitro cytotoxicity and genotoxicity of single and combined pesticides used by Bolivian farmers. Barrón Cuenca J, de Oliveira Galvão MF, Ünlü Endirlik B, Tirado N, Dreij K. Environ Mol Mutagen. 2022; 63:4-17.

Increased levels of genotoxic damage in a Bolivian agricultural population exposed to mixtures of pesticides. Barrón Cuenca J, Tirado N, Barral J, Ali I, Levi M, Stenius U, et al Sci. Total Environ. 2019;695:133942



  • Cancer och Allergi-fonden
  • Institute of Environmental Medicine
  • Swedish Environmental Protection Agency (Naturvårdsverket)
  • Swedish International Development Cooperation Agency (SIDA)
  • Swedish Research Council (VR and Formas)
  • The Swedish Foundation for International Cooperation in Research and Higher Education (STINT)

Research group