Date of Award

2026-08-01

Degree Name

Doctor of Philosophy

Department

Environmental Science and Engineering

Advisor(s)

Jorge L. Gardea-Torresdey

Abstract

This dissertation investigates the potential environmental and public health impacts associated with fine jewelry and the gemstone industry, specifically focusing on potentially toxic elements (PTEs) in sapphires. Heavy metal contamination within consumer goods and raw materials has become a pervasive issue in the United States. Potentially toxic elements (PTEs), such as lead (Pb), cadmium (Cd), and nickel (Ni), arsenic (As), pose significant toxic health risks. Human exposure to these PTEs via inhalation, ingestion, or dermal contact can induce severe health effects; Pb is associated with cognitive impairment and developmental delays in children, Cd exposure can cause pulmonary and renal damage or oncogenesis, and Ni exposure frequently triggers severe contact dermatitis. Consequently, robust analytical assessments of these materials are vital. This research presents three comprehensive case studies evaluating heavy metal contamination, spectroscopic characterization, and regional environmental risks within the Paso del Norte region. The first study utilized X-ray fluorescence (XRF) spectroscopy to screen 143 fine jewelry pieces from the El Paso del Norte region for heavy metal content. The results revealed that 42.7% of the samples contained Ni within the metal alloy, a trend predominantly observed in pieces with lower gold (Au) purity. Additionally, 7.7% of the samples exhibited Pb contamination within the embedded gemstones; notably, no detectable levels of Pb or Cd were identified within the structural metal alloys. The second assessment comprised a nine-month investigation of 101 gold and silver jewelry pieces containing colored gemstones marketed as sapphires (corundum). High-wavenumber Raman (HW Raman) spectroscopy was employed to characterize the crystal structure of corundum, followed by XRF spectroscopy to quantify trace potentially toxic element compositions. HW Raman spectral profiles identified characteristic sapphire bands at 4387 cm⁻¹ and 4358 cm⁻¹, confirming 51 of the gemstones (50.5%) as authentic sapphires. Elemental analysis via XRF revealed Pb trace levels in 4% of the authentic sapphires contained, indicating Pb treatment. The third environmental assessment examined the Pb bioaccessibility of two Pb-treated pink sapphires selected from a cohort of 24 colored gemstones marketed as sapphires. The findings revealed that 12 samples (50%) of the original samples were misidentified as sapphires, and about 21% contained detectable levels of Pb via XRF spectroscopy. Lead bioaccessibility was evaluated by performing a 28-day leaching assay on artificial sweat performed on the two selected pink sapphires. Migration of Pb from the gemstones to the leaching medium was determined using Inductively Coupled Plasma -Optical Emission Spectroscopy (ICP-OES). The concentration of leached Pb was determined to be 40.2 ppm in one gemstone, and 87.3 ppm in the other gemstone. In conclusion, these three environmental studies demonstrated that Pb, Cd and As were not detected in the fine jewelry's gold and silver alloys; however, Ni was identified as a potentially toxic element, which poses a health risk to children and adults. The two latter studies also shone light showing that at least 50% of the gemstones marketed as sapphires are not correctly identified. On the other hand, Pb has been found in treated gemstones, such as sapphire and synthetic gemstones. Lead may be bioaccessible, in treated sapphires, presenting a significant exposure pathway for consumers in the U.S.-Mexico border region and globally. Ultimately, this research advances our understanding of potentially toxic element incorporation and stability within consumer gemstones, providing a foundational framework for future toxicological mechanisms.

Language

en

Provenance

Received from ProQuest

File Size

101 p.

File Format

application/pdf

Rights Holder

Maricarmen Lerma

Download

Share

COinS