Colloidal silver and silver nanoparticles bioaccessibility in drinking water filters

• The release of silver in water from coal sample with AgNPs with 30 nm is the lowest.
• The bioaccessibility percentage of Ag in AgNPs with 30 nm was the lowest.
• There are high interactions of smaller nanoparticles with the coal porous.
• The health risk of use AgNPs in water filter is lower than using colloidal silver.

The bacteriostatic effects of colloidal silver and silver nanoparticles (AgNPs) have prompted impregnation of coal in some water filters to prevent microbial regrowth. Many commercially available water filters contain silver, which has raised the risk of silver ingestion. This scenario has motivated conduction of the present study, which has investigated silver leaching from coal samples into water and evaluated colloidal silver and silver nanoparticles bioaccessibility. Two kinds of coal samples were investigated: one with colloidal silver and another one with AgNPs, in different average sizes: 30 and 120 nm. Nanoparticles were characterized by dispersive light scattering (DLS), transmission electron microscopy (TEM) and, scanning electron microscopy (SEM) techniques. Silver measurements were carried out in a graphite furnace atomic absorption spectrometry (GFAAS). Bioaccessibility and leached results showed that coal samples with AgNPs, measuring 30 nm, were the least bioaccessible due the strong interaction between nanoparticles and coal pores. Colloidal silver was more bioaccessible compared to AgNPs, and could pose higher health risk after long-term exposure, although Hazard Quotient was lower than 1. The sample containing colloidal silver leached the highest concentration of silver.

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