C2H2 EAGER: Soil and Toxicological Assays to Quantify and Mitigate Climate Change Effects on Human Exposure to Nanophase Aluminosilicate Minerals in Volcanic Soils

This research determines the nature, toxicity, and mobility of nanoscale mineral particles that form naturally in volcanic/volcanic, ash-rich soils. It examines whether mineralogical weathering products that develop from volcanic rock are the cause of podoconiosis, a skin disease that manifests like elephantitus, and is found in agricultural workers who labor barefoot in volcanic soils without adequate clothing and footwear.

Human exposure to these mineral particles is limited by organic carbon in soil, which binds the particles into aggregates, as opposed to being free particles. Climate change and drought reduce the amount of organic carbon in soil, hence increases human exposure to the podoconiosis which is a debilitating condition. This project focuses on rural, subsistance, farm workers in Rwanda where podoconiosis is a common ailment.

In addition to the mineralogical and toxicological work, the project includes assessment of agricultural practices that can prevent organic carbon loss as the climate changes. It also involves mineralogical sampling and high-resolution analysis to determine whether a specific mineral species, such as imogolite - a fiberous mineral with the same size and shape as asbestos can puncture and invade skin tissue, is responsible for the condition.

Broader impacts of the work include reduction of a serious and debilitating health condition that has serious economic impacts for rural families in developing countries. In addition, by examinimg the crystaline structure and dimensions of volcanic soil minerals and by studying how organic matter stabilizes mineral particles in soils, this project will contribute to understanding soil properties not only in Africa and Rwanda, but across all nations as the climate changes.

The project establishes a new international partnership between soil scientists and toxicologists in the US, Europe and Africa Rift countries. It will support a female graduate student and educate undergraduate graduate scholars in Africa and the US that come from populations underrepresented in Earth science.

This project will collect and study soils from agricultural regions of Rwanda where there is significant podoconiosis prevalence. Nanoscale minerals in soils will be extracted using chemical and mechanical methods. They will be characterized using X-ray diffraction, electron microscopy, and other high-resolution imaging and analytical methods.

The toxicity of the extracted minerals will be quantified using toxicological and gene expression methods by collaborators in the UK and France. Our collaborators, one of which is from the Unviersity of Swansea Faculty of Medicine and who has a history of podoconoisis work and is funded under other auspices, will use mammalian immune cells that will be exposed to particles extracted from volcanic soils to assess effects on cell viability and non-lethal signatures of immune response.

Next-generation DNA sequencing will identify up- or down-regulation of inflammatory pathways. The strength of the binding of mineral particles to soil, which will be done in the US part of the study, will be quantified using a torsional rheometry method. This shears soil samples and quantifies particles transferred to a surrogate of human skin.

The US part of the study will develop methods to mitigate anticipated climate change effects on particle exposure by exploring and manipulating organic carbon and its type and quantity in soils to enhance soil particle aggregation which can mitigate the occurrence of podoconiosis.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.