Overview

We address public health research questions through molecular-level analyses of chemical contaminants and biomarkers. A primary component of this research is the development of advanced analytical methods. Often these compounds are analyzed in complex sample matrices at low abundance; therefore, most methods in our laboratory utilize chromatography and mass spectrometry for chemical identification and quantification.

We work across a variety of public and environmental health related fields, including microplastic pollution, environmental tobacco product waste, pollution in the US-Mexico border region, pesticide contamination, bioaccumulative contaminants in marine wildlife, evaluation of wastewater treatment systems, and thirdhand tobacco smoke pollution. Example research areas are described below.

For a full list of past projects, please see the publications of Dr. Hoh and Dr. Dodder.

Environmental Fate of Contaminants and Human Exposure

Quantitative mass spectrometry methods are developed to study the behavior of specific environmental contaminants and their associated biomarkers. Our laboratory developes targeted GC/MS and LC/MS/MS analytical methods for tobacco smoke components and related biomarkers (e.g., nicotine, tobacco specific nitrosamines, and cotinine), pesticides and related biomarkers, persistent organic pollutants (e.g., PCBs, organochlorine pesticides, and flame retardants), and other contaminants of known and emerging concern.

Example Projects

  • Examining the efficiency of contaminated soil/sediment remediation through analysis of PAHs.
  • Pesticide exposure among agricultural communities.

Example Literature

Microplastic Pollution


Plastic discarded in the environment breaks down over time into microplastic particles. Most work in this field is on non-fiber and non-rubber microplastics, such as microbeads and broken fragments of larger plastics, and most studies describe effects due to the particles themselves rather than the leached constituents. Considering the far greater number of microfibers (from textiles and tire wear) found in California’s coastal waters, our current research focuses on these two categories of microplastics.

Example Projects

  • Evaluate the dissolution of chemicals from microfibers and tire wear particles in water.
  • Elucidate mechanisms of aquatic toxicity produced by leaching chemicals from the new and aged microplastics.

Example Literature

Environmental Tobacco and Cannabis Waste

Discarded cigarette butts are among the most prevalent litter found at ocean beaches and in inland waterways. However, their impact on the environment has not been evaluated. Cigarette tobacco and cigarette smoke contain numerous toxic chemicals, and cigarette filters are made of non-biodegradable plastic that trap cigarette smoke particulates and less volatile chemicals. Therefore, harmful chemicals may leach from the filters and unburt tobacco in cigarette butts.

Documentary on the potential environmental impact of discarded cigarette butts.

Cannabis cultivation may have local environmenal impacts due to the use of pesticides and fertilizer, and from plant residue.

Example Projects

  • Identification of tobacco product waste contaminants by non-targeted analysis.
  • Analyze pesticides in ambient waters downstream of cannabis farms.

Example Literature

Bioaccumulative Contaminants in Sentinel Species

Biomagnifying contaminants originating from the California coast will accumulate in high trophic level marine mammals, and other coastal animals, at levels that may induce a biological impact. These species also serve as spatial and temporal trend indicators of historical and emerging contaminants. Using non-targeted mass spectrometry, we developed an approach for the detection of a broad range of organic compounds in fish oil, marine mammal blubber, and avian species.

Example Projects

  • Enhanced cataloging by non-targeted mass spectrometry of bioaccumulative chemicals in stranded marine mammals to assess health impacts.
  • Assessing potential endocrine disrupting chemicals in the critically endangered California condor.

Example Literature

Thirdhand Tobacco Smoke Exposure

Tobacco smoke can be a major contributor to indoor air pollution. When dust and surfaces remain contaminated long after active smoking has ceased, it is referred to as "thirdhand" smoke. We investigate human exposure to thirdhand smoke under various indoor settings such as homes, cars, and commercial businesses, and compare thirdhand smoke profiles to smoking behavior.

Example Projects

Example Literature

Non-Targeted Contaminant Discovery

There is concern that unrecognized or novel contaminants are either contributing to current health impacts or may pose an elevated risk in the future. Non-targeted mass spectrometry approaches provide a comprehensive contaminant profile that can be used to investigate differences among sample groups, identify unknown compounds, and suggest new chemicals for further risk assessment. Custom software is developed to process the non-targeted data sets. We are continuously working to further the development of non-targeted analytical approaches and their applications to environmental monitoring, food safety, and exposure assessment.

Example Projects

  • Evaluation of contaminant removal in decentralized water reuse systems.
  • Identify unexpected organic contaminants following advanced oxidation water treatment processes.
  • Nontargeted analysis of sediment and water in San Francisco Bay.

Example Literature