Thailand has undergone rapid social and economic changes over the past fifty years, and
prevalence and mortality of disease has decreased for infectious diseases and increased for
chronic diseases across the age spectrum. This dissertation focuses on identifying disparities in
childhood cancer and environmental health in Thailand by examining 1) childhood leukemia
incidence and survival trends from 1990-2011 in the Songkhla Province in Thailand, and 2) high
cadmium (Cd) exposure among northern Thai women from Mae Sot and its effects on biologic
aging and co-exposure to toxic and essential metals. The first aim utilized cancer data from the
Songkhla Cancer Registry and the United States (US). Leukemia incidence and survival was
significantly lower in Songkhla compared to US but incidence and survival significantly
increased annually from 1990-2011 in Thailand by approximately 2%.
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In the second and third aims, epigenome-wide DNA methylation and blood and urine
metal biomarkers of exposure were measured in two samples of women from Mae Sot. These
women were exposed to Cd, a toxic metal, after ingesting water and rice contaminated by
environmental pollution from nearby zinc mining. DNA methylation is a dynamic and sensitive
epigenetic marker that changes during aging and is associated with Cd exposure. Biologic age, or
the physiologic age of an individual, can be estimated from a collection of a subset of these
changes. A greater difference between chronologic age and biologic age may indicate
accelerated aging. In Aim 2, higher Cd exposure was associated with smaller difference between
biologic and chronologic age, and Cd modified methylation at some age-associated sites
included in predictors of biologic age. In Aim 3 co-exposure of metals were examined in blood
and urine using multivariate methods. Blood lead and urinary arsenic were also elevated in this
high Cd exposed sample. Unique patterns emerged among these metals, suggesting that lead and
Cd exposures were independent. Further public health interventions are necessary to address
pediatric cancer incidence and survival disparities in Thailand and to study sources of exposure
to other metals and other biomarkers aging within the Mae Sot population.