Natalie Johnson, Ph.D.

Education and Post-Graduate Training

· B.S., Biology, Texas A&M University College of Science

· Ph.D., Toxicology, Texas A&M University College of Veterinary Medicine & Biomedical Sciences

· Postdoctoral fellowship, Johns Hopkins University Bloomberg School of Public Health

Teaching Interests

· Environmental & Occupational Diseases

· Environmental Health & Toxicology

· Mechanisms of Disease Prevention

Research Interests

· Environmental carcinogenesis

· Health disparities in underserved populations

· Biomarkers of exposure and dose

· Cancer prevention

Dr. Johnson has extensive experience in research on interventions to reduce exposure to aflatoxin, a potent naturally-occurring liver carcinogen. Her doctoral research entailed managing a Phase IIa clinical intervention trial for the reduction of dietary aflatoxins in a high-risk population in Ghana. She assessed the safety and feasibility of the intervention, and her laboratory work focused on measuring the urinary metabolite, aflatoxin M1, to evaluate the impact of intervention on this biomarker. A key observation during a visit to the study site was the presence of indoor air pollution stemming from traditional cooking practices. Thus, Dr. Johnson expanded her research to evaluate exposure to the smoke constituents, polycyclic aromatic hydrocarbons (PAHs), by measuring an additional urinary biomarker, 1-hydroxypyrene. A further opportunity to work with a population in South Texas allowed her to transfer her expertise gained from work in rural Ghana. In this study, Dr. Johnson participated in a pilot project to investigate the role of aflatoxin, PAH exposure and hepatitis infection in a cohort in San Antonio at increased risk for the development of liver cancer. These experiences have reinforced her interest to work with underserved communities. To provide a broader foundation, her postdoctoral training as an NIEHS Environmental Health Sciences trainee explored the mechanisms of aflatoxin-induced carcinogenesis in a rat model of liver cancer. In this model, Dr. Johnson evaluated the chemopreventive power of a synthetic triterpenoid, CDDO-Im, for protection against tumorigenesis. The rich repository of biospecimens collected from this lifetime tumor study has provided the opportunity to investigate the reduction of DNA adducts and the predictive value of biomarkers for hepatocellular carcinoma risk. Dr. Johnson has drawn on her unique background in community and mechanism-based sciences to develop her research program at SRPH. She is currently addressing environmental health issues in low resource populations where the impact of exposures is commonly elevated.

Selected Publications

· Mitchell NJ, Kumi J, Johnson NM, Dotse E, Marroquin-Cardona A, Wang JS, Jolly PE, Ankrah NA, Phillips TD. 2013. Reduction in the urinary aflatoxin M1 biomarker as an early indicator of the efficacy of dietary interventions to reduce exposure to aflatoxins. Biomarkers. 18:391-8. PMID:23697800

· Robinson A, Johnson NM, Strey A, Taylor JF, Marroquín-Cardona A, Mitchell NJ, Afriyie-Gyawu E, Ankrah NA, Williams JH, Wang JS, Jolly PE, Nachman RJ, Phillips TD. 2012. Calcium montmorillonite clay reduces urinary biomarkers of fumonisin B1 exposure in rats and humans. Food Addit Contam 29:809-18. PMID: 22324939

· Marroquín-Cardona A, Deng Y, Garcia-Mazcorro JF, Johnson NM, Mitchell NJ, Tang L, Robinson A, Taylor JF, Wang JS, Phillips TD. 2011. Characterization and safety of uniform particle size NovaSil clay as a potential aflatoxin enterosorbent. Appl Clay Sci 54: 248-57. PMID: 22249378

· Johnson NM, Qian G, Xu L, Tietze D, Marroquín-Cardona A, Robinson A, Rodriguez M, Kaufman L, Cunningham K, Wittmer J, Guerra F, Donnelly KC, Williams JH, Wang JS, Phillips TD. 2010. Aflatoxin and PAH exposure biomarkers in a U.S. population with a high incidence of hepatocellular carcinoma. Sci Total Environ 408:6027-31. PMID: 20870273

· Johnson NM, Afriyie-Gyawu E, Huebner HJ, Marroquin-Cardona A, Robinson A, Tang L, Xu L, Ankrah NA, Ofori-Adjei D, Jolly PE, Williams JH, Wang JS, Phillips TD. 2009. PAH Exposure in a Ghanaian population at high risk for aflatoxicosis. Sci Total Environ 407:1886-91. PMID: 19144392

· Marroquín-Cardona A, Taylor JF, Hallmark CT, Deng Y, Johnson NM, Phillips TD. 2009. In vitro and in vivo characterization of mycotoxin-binding additives used for animal feeds in México. Food Addit Contam 26:733-43. PMID: 19680945

· Afriyie-Gyawu E, Wang Z, Ankrah NA, Xu L, Johnson NM, Tang L, Guan H, Huebner HJ, Jolly PE Ellis WO, Taylor R, Brattin B, Ofori-Adjei D, Williams JH, Wang JS, Phillips TD. 2008. NovaSil clay does not affect the concentrations of vitamins A and E and nutrient minerals in serum samples from Ghanaians at high risk for aflatoxicosis. Food Addit Contam 25:872-84. PMID: 18569006

· Wang P, Afriyie-Gyawu E, Tang Y, Johnson NM, Xu L, Tang L, Huebner HJ, Ankrah NA, Ofori-Adjei D, Ellis WO, Jolly PE, Williams JH, Wang JS, Phillips TD. 2008. NovaSil clay intervention in Ghanaians at high risk for aflatoxicosis: II. Reduction in biomarkers of aflatoxin exposure in blood and urine. Food Addit Contam 25:622-34. PMID: 18478481

· Afriyie-Gyawu E, Ankrah NA, Huebner HJ, Ofosuhene M, Kumi J, Johnson NM, Tang L, Xu L, Ofori-Adjei D, Williams JH, Wang JS, Phillips, TD. 2008. NovaSil clay intervention in Ghanaians at high risk for aflatoxicosis: I. Study design and clinical outcomes. Food Addit Contam 25:76-87. PMID: 17852392