Characterization of nanomaterials in metal colloid-containing dietary supplement drinks and assessment of their potential interactions after ingestion

Little information is available regarding the suitability of analytical methods to evaluate claims regarding the presence of engineered nanomaterials (NMs) in consumer products, their potential toxic effects to humans, or their life cycle after product use. This study was designed to assess the potential interactions across the life cycle of eight commercially available dietary supplement drinks from a single vendor, all purported to contain metal NMs. Analysis showed that all of the products contained metallic NMs with average diameters below 50 nm as determined by dynamic light scattering and transmission electron microscopy. The products intended use is human ingestion; in order to examine potential human health effects after ingestion, we investigated the interaction of NMs in the drinks with an in vitro cell system that faithfully mimics human intestinal cells. After exposure to concentrations of NMs as low as 3.5 μg/mL, we found that the number of microvilli decreased relative to untreated controls for all drinks. From a life cycle perspective, consumption of drinks containing NMs will eventually result in sewer discharge of these NMs in feces. Screening tests for NM removal by biosolids in wastewater treatment plants (WWTPs) conducted using the NMs contained in supplement drinks showed variable removal of NMs, with the fractions removed ranging from (99 ± 27)% to (30 ± 0.05)%. The results showed that metal NM-based supplements may have an effect on the number of viable human intestinal microvilli and will likely enter the environment via either water or solids released from WWTPs.