Natalie Johnson, Ph.D.
Education and Post-Graduate Training
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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
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Environmental & Occupational Diseases
Environmental Health & Toxicology
Mechanisms of Disease Prevention
Research Interests
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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 highrisk 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, 1hydroxypyrene. 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
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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