David DeMarini

U.S. Environmental Protection Agency, RTP, NC (Retired)

Tell us a bit about your scientific and educational background.

I was born in Peoria, IL, and while in high school, I placed second in comedy reading at the state forensics competition, which was held in 1966 at Illinois State University in Normal, IL, just a 40-min drive from Peoria. Because of that experience, I applied only to ISU for college, and although I thought of majoring in theater, my mother, Kathleen, who was a nurse, wisely advised me to major in biology instead.  
Consequently, I was required to take Herman Brockman's genetics course in my senior year in 1972. This was the best stroke of academic luck I could ever have had. I was smitten with the topic of genetics and with Herman as a teacher. 

Little did I know at the time that Herman had been a charter member of EMGS and was deeply connected to the Society and, of course, that he was training his students in genetic toxicology.  However, I soon found out because I did my master's degree with Herman, which engendered a passion for the field and for EMGS, whose annual meeting I first attended in 1974 in Washington, DC, with Herman’s lab.  

After completing my master’s degree, I worked for 1.5 years at the U.S. Department of Agriculture’s research lab in Peoria, IL, which resulted in my first two published papers in 1977 and 1978 (on dsRNA viruses in the fungus Penicillium).   During that time, I again joined Herman's lab to attend the 1976 EMGS meeting in Atlanta, even though I did not have any more work to present. One night I drunkenly fell off a bar stool, and Herman asked if I was OK and also if I would return for the PhD in his lab. In a daze, I said "yes," and the rest is history.  ISU did not at that time permit a student to receive all three degrees from the university, so Herman asked for an exception, and although some faculty voted "no," I was allowed to return.

My PhD work followed up on Bruce Ames’ recent work on the mutagenicity of cigarette smoke and a variety of other complex mixtures using assays in Neurospora, yeast, and Salmonella.  During those busy four years, and through Herman and EMGS, I got to meet Bruce, who lived to be 95 and died in October 2024.  Little did I know that I would use his assay for the next 50 years, generating, along with Tom Cebula at the US FDA, the mutation spectrum of many agents.  Along with Herman, I owe a great deal to Bruce for my scientific work; I wrote his obituary in Mutation Research, which is here: Ames Obituary.

Herman had done a postdoc at the Oak Ridge National Laboratory (ORNL) in Oak Ridge, TN, which is where EMGS was founded by Alex Hollaender and others there.  Thus, I started a postdoc at Oak Ridge in 1980 with Abe Hsie who had recently invented the CHO/Hprt assay.  This was an exciting time to be doing mammalian cell mutagenesis, and one of my projects was the first to examine the mutagenicity of complex mixtures in mammalian cells, in this case evaluating fractions of extracts from Jimmy Carter’s synthetic fuels program to convert coal to liquid fuels. Another project involved determining the mutagenicity of ellipticines, which were new anticancer drugs developed in France and loaned to Abe for mutagenicity evaluation.  The paper on ellipticines was published in Cancer Research in 1983, and it provided a propitious opportunity for a second postdoc that impacted the rest of my career. 

In 1982, Ronald Regan cut the budget by 50% of the Department of Energy, which houses all the national laboratories, including ORNL. Reminiscent of current times, all of the students and postdocs had to leave (and Carter’s synthetic fuels program was ended).  However, Mike Shelby kindly continued my ORISE postdoc at NIEHS, where I went in November 1982.  Mike gave me the opportunity to incorporate genetic toxicology data for the first time into the NTP rodent cancer reports.  He and Ray Tennant supported my efforts to provide mechanistic explanations for the carcinogenicity of various agents, something not done in prior NTP reports.
While there, Lynn Ripley, who I had known from my Illinois days, asked to eat lunch with me out on the deck at NIEHS.  She had read my Cancer Research paper and said that she had discovered a potentially surprising mutational mechanism for the ellipticines (involving topoisomerase) and asked if I would work with her on it.  Mike Shelby generously provided the opportunity for me to do so, and Lynn taught me how to clone, sequence DNA, and understand molecular mechanisms of mutagenesis, some of which Lynn had developed.

This was a critical learning experience for me.  Lynn helped me formulate my future research program, which built on my experience with complex mixtures in Herman’s and Abe’s labs, and molecular mutagenesis in her lab.  I owe Lynn a great deal of gratitude for teaching me so much and for positioning me to apply molecular mutagenesis to my next job, as described below.  She died suddenly just a few months ago at age 78, and I wrote her obituary, which is here:  Ripley Obituary 

I received a call in November 1984 from Larry Claxton at EPA saying that he, Joellen Lewtas, and Mike Waters had a permanent position available at EPA and asked me to apply. This turned out to be my dream job and the only permanent job I ever had.  I began at EPA in March 1985, although I was there only for 1 hour that first day because I had to fly to Lyon, France, to participate in the IARC Monograph on tobacco smoking, chaired by Sir Richard Doll, where we evaluated tobacco smoking as a Group 1 human lung carcinogen.  I was only 34, and I never imagined that I would end up working with IARC for the next 40 years, serving on 10 cancer monographs and chairing two of them.  IARC kindly asked me to chair their workshop on the 10 Key Characteristics of Carcinogens, and a summary of that workshop was just published a few months ago in, perhaps, one of the final issues of Environ Health Perspectives.     

What do you see as the greatest value or most rewarding aspect of your scientific work?

Due to the kindness and generosity of hundreds of colleagues at EPA and worldwide, I was able to have a 40-year career at EPA/RTP where I was fortunate to work with unimaginably supportive and brilliant scientists, coupled with ample financial and infrastructure support.  (How many scientists have published >200 papers and never wrote a grant proposal?)  I was lucky, indeed.

One of the most rewarding aspects of my scientific career was working with people who helped me apply my unusual background in both complex mixtures and molecular mutagenesis to pressing environmental problems, which was all uniquely possible only at EPA/RTP.  The other was engaging with EMGS, which provided a network of friends and colleagues and leadership opportunities to help facilitate environmental mutagenesis worldwide. 

The laboratories at EPA established by Mike Waters, Joellen Lewtas, Larry Claxton, Steven Nesnow, Martha Moore, and others by the time I arrived there formed the most important setting in the world for studying the mutagenicity and carcinogenicity of real-world complex mixtures of air, soil, and water. I worked with engineers, chemists, biologists, modelers, statisticians, policy makers, etc. for 4 decades doing this work. My colleagues and I were able to apply molecular biology tools to complex mixtures and determine the mutation spectra of air pollution, drinking water, and a wide variety of real-world combustion emissions, as well as of the gas phase of air, work that was just published in 2024. This is the work about which I am proudest and that was the most rewarding. I was a Scientist Emeritus for 5 more years to complete the writing/publication of 20 more papers after I retired in March 2020, ending my formal association with EPA in March 2025. 

Joellen Lewtas and Larry Claxton were my colleagues and bosses for more than 30 years, and together with many others, we were able to identify the mutations induced by complex mixtures, the chemical classes responsible for the mutagenesis, and show that those were the primary mutations in humans whose tumors were associated with exposure to those mixtures.  Martha Moore (Moore Obituary) graciously let me collaborate with her in her mouse lymphoma lab where we were able to show that the ellipticines and other topoisomerase poisons were the most potent clastogenic mutagens ever discovered.  Mike Waters first invited me to work on his Gene-Tox project while I was still a postdoc at Oak Ridge, and we concluded our long collaboration in 2019 when we ended our 21 years as Co-Editors-in-Chief of Mutation Research Reviews.  Larry, Mike, and I wrote the obituary for Joellen in Mutation Research, which is here:  Lewtas Obituary 

What initially drew you to the EMGS? 

My connection to EMGS started with Herman Brockman, who died just 2 months ago at the age of 90; here is a tribute I wrote about him for ISU: Brockman Tribute.  Herman was a charter member of EMGS in 1969, and he brought his students and postdocs to EMGS meetings every year. I have attended all but two EMGS meetings since 1974, spanning more than 50 years of attendance and participation. Through EMGS, we were networked like crazy. By the time I finished my PhD in 1980, I had met nearly all of the founders and leaders in the field of mutagenesis and DNA repair, something not possible in a large scientific society. 

How has EMGS impacted your professional development? 

EMGS WAS my professional development. It provided the intellectual and scientific home for me and countless others over the past half a century. The EMGS gave me an opportunity to interact with others in my field, to collaborate, and to share our work. Equally importantly, it gave me the opportunity to use other skills besides doing science: organizing (countless EMGS meetings, the ICEM with Phil Hanawalt in 2005 in San Francisco, and nearly 20 Hollaender courses), providing leadership (I am a past president), and mentorship of others. Plus, it was just plain fun! Many of my EMGS colleagues became life-long friends. 

What advice would you offer to students or early career investigators? 

Don't be shy. Most scientists are uncomfortable in social settings, but my advice is to be brave and engage with others at scientific conferences, learn what people are doing, share with them what you are doing, and help each other as the years go by. Networking is a tired phrase that young scientists hear all the time, but it is one of the most important aspects of being a scientist, and scientific societies such as EMGS facilitate this more than most. Take full advantage of the opportunity that EMGS meetings provide; it will change your life. 

What involvement opportunities with EMGS have you found to be the most rewarding? SIGs, awards, etc.

As noted above, I think the most rewarding aspect of my association with EMGS has been the opportunities to know and work with some of the most remarkable people in our field. They have enhanced my own research, and many have ended up as close friends. The leadership opportunities afforded to me by EMGS as president of the national and international EMGS, as well as organizing Hollaender Courses, enabled me to give opportunities for others to highlight their science and to enhance their networking opportunities.   

What are the most rewarding connections you have made since joining EMGS?

A large number of friends!!! Some EMGS members became scientific collaborators, as well as friends. The ability of EMGS to foster such connections is invaluable, and EMGS does this almost uniquely among scientific societies. 

What do you think the greatest scientific achievement in history has been?

The breeding and cultivation of corn that native populations in central America conducted for thousands of years to convert a simple grass, teosinte, into corn (maize) is a key scientific achievement. I lived in the midst of corn fields for the first 30 years of my life in central Illinois, and to this day, I marvel at corn and am still addicted to popcorn. Corn is a major scientific achievement that also happens to be good to eat. 

If you could meet any scientist, past or present, who would it be and what would you talk about?

I heard Barbara McClintock speak at a Stadler Genetics Symposium in the 1978 in Columbia, Missouri; Herman Brockman had taken us there to hear her speak. Nancy Kleckner from Harvard also spoke, and she had just announced her discovery of transposons in E. coli, proving McClintock's inference of transposable genetic elements or "jumping genes" in corn. McClintock gave a talk using glass lantern slides (look it up) and read from a yellowed paper a talk she had prepared in the 1940s but had never given because she didn't think anyone would believe her. Now we did. She won the Nobel Prize for her insights in 1983. I did not get to talk with her then, but I would have liked to have explored with her further how she had conceived of transposable elements, a feat something akin to Einstein's insight into space-time.  

If you were not a scientist, what would you be doing?

A lounge act--playing jazz piano in a bar; my father, Santa, owned and operated a bar for >40 years.  It would have been my ultimate dream job, unrealized due to my limited talent.