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<p>Non-essential trace metals (lead, mercury, arsenic, and cadmium) are ubiquitous
in our environment and have overlapping routes of exposure, yet mixed trace metal
exposures are rarely considered in epidemiological studies. Instead, research often
follows a single research question that focuses on a single trace metal of concern
and does not incorporate potential co-exposures. The published literature of artisanal
small-scale mining in the Amazon is a prime example as it has predominantly focused
on mercury exposure, due to its use in the mining process. Once exposures of concern
are identified, further studies evaluate health outcomes; however, the health effects
cannot be accurately determined without accounting for co-exposures. This verification
is becoming more important as there is a growing recognition that mixed trace metal
exposures are more common than previously believed.To address the prevalence of mixed
trace metal exposures and their health effects in the Peruvian Amazon region of Madre
de Dios, I use epidemiological data from the COhorte de NAcimiento de MAdre de Dios
(CONAMAD) birth cohort study (2018-Present), and two cross-sectional epidemiological
studies (Amarakaeri Communal Reserve study (ACR, 2015), and Etiology and Toxic Metals
study (EATM, 2018)). CONAMAD collected survey data along with maternal and cord blood
samples at birth, which were processed for minerals and trace metals. The cross-sectional
studies collected venous blood for trace metal analysis and hair samples for total
hair mercury. Blood samples from the ACR were also processed for amino acids. In-depth
demographic and health survey data were collected in all three studies. Structural
equation models and random mixed effect models were used to evaluate research questions.
The cross-sectional studies demonstrate a high correlation of lead and mercury exposure
in communities that rely on wild fish and wild game as protein sources, which is prevalent
throughout the Amazon. Consuming a meal of wild game resulted in an estimated lead
dose of 500 µg, with those who eat wild game (Yes/No) associated with 1.41 µg/dL (95%
CI: 1.20 – 1.70) higher blood lead levels compared to those who do not. This furthers
the notion that mixed exposures are likely more common than previously believed.
Mixed exposures target the same toxicological pathway, which may lead to synergistic
or antagonistic effects. My research found that lead disrupts the arginine pathway
and is associated with increased blood pressure. Mercury exposure was a modifier of
the arginine pathway, with high blood mercury levels changing the effect of global
arginine bioavailability from 17.16 (95% CI: 9.09 – 25.84) to -14.17 (95% CI: -31.88
- -0.33) on systolic blood pressure. Interestingly, mercury was not directly associated
with the arginine pathway. Results from the birth cohort demonstrate the importance
of nutrition and prenatal care for fetal development, which had a large positive effect
on birthweight and gestational age. However, even low maternal lead exposure had detrimental
effects on fetal health. A 1% increase in maternal blood lead was associated with
a shorter gestational age of 0.05 days (β: -0.75, 95% CI: -1.51 - -0.13), even with
the CONAMAD birth cohort having lower blood lead levels than other birth cohorts.
There is a need for an integrated approach of nutritional and exposure assessments
to better understand neonatal health outcomes.
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