Uranium & Other Heavy Metal Contamination in Herbal Tea in an American Indian Community

Aims:  This study examines environmental contamination in a commonly used American Indian herbal tea in New Mexico (NM). Uranium (U) and associated heavy metals (As, Cd, Cs, Mo, Pb, Se, Th, V) were examined. The study aims were to: (1) identify dietary behavior in relation to the intake of locally harvested herbal tea, (2) compare U and heavy metal (HM) levels in tea from areas with high and low levels of U contamination, and
(3) disseminate study findings to the Diné (Navajo) leadership and communities.

Background:  Vulnerable populations are disproportionately exposed to toxic environmental materials.  From the 1940s - 1980s, northwestern NM contributed 40% of the U.S. U production. There remain more than 1,100 unreclaimed mining sites in the study area. In the Diné community, Thelesperma megapotamicum is infused and utilized as a common beverage and is also a diuretic to address urinary or digestive problems or used to dye sheep wool for textiles. Studies that examine T. megapotamicum in relation to HM contamination do not exist. Preliminary human studies are emerging from the current community that demonstrate that chronic HM exposure may be correlated to increased incidences of autoimmune disorders, increased risk of developing hypertension, diabetes and renal failure. Uranium enters the body by inhalation or ingestion (contaminated water or food).  Human/animal studies of those exposed to U have shown kidney chemical toxicity and damage to liver, muscle, cardiovascular, and nervous systems. Surveillance and screening for health problems is problematic.

Methods:  Participants from the Diné Network for Environmental Health study were asked to join the study. New participants were invited by word-of-mouth, public announcements, chapter house meetings fliers, and community event announcements. Two questionnaires were administered. Data plant and soil levels were determined on a scale of milligrams (mg) per kilogram (kg).  Heavy metal concentration levels were derived from fresh tea and paired with soil samples utilizing Inductively Coupled Plasma-Mass Spectrometry (ICP-MS).  GIS data collected distance proximity data and sample location information.

Results:  In herb soil, As exceeded the Human Health Screening Level (HHSL) but was not reflected in the infused portion of tea. Tea roots contained greater levels of HM than those parts used to infuse tea. Overall, the infused portion of tea was not contaminated above the recommended guidelines set by the World Food and Agriculture Organization.

Implications:  Larger tea samples in other mine impacted areas of the community should be explored to identify potential contamination. Education regarding safe drinking water use needs to be emphasized.  Research should focus on the extent of HM transfer to boiled tea water and determine biological contaminant levels in humans who consume tea. The use of herbal tea is common world-wide but safe ingestion is unknown.  Equal access to contaminant assessment and information is lacking when discussing herbal products or traditional use of plants.