Citation:

Belton, K., M. Hartman, AND K. Dreher. In Vitro Pulmonary Toxicity Assessment of Nano-Enabled Outdoor Wood Preservatives. Society of Toxicology, San Antonio, TX, March 11 - 15, 2018.

Impact/Purpose:

Nanoscale CuCO3 (1 - 400 nm) and CeO2 (5 - 7 nm) particles are employed as a preservative and UV coating for outdoor wood, respectively. CuCO3 and CeO2 treated outdoor wood provide a product and application with a risk of dermal and/or inhalation exposures to a mixture of nanomaterials with unknown health effects. To address this uncertainty, research was conducted to assess the potential pulmonary toxicity of CuCO3 and CeO2 employed in outdoor wood preservation and UV coating.

Description:

Nanoscale CuCO3 (1 - 400 nm) and CeO2 (5 - 7 nm) particles are employed as a preservative and UV coating for outdoor wood, respectively. CuCO3 and CeO2 treated outdoor wood provide a product and application with a risk of dermal and/or inhalation exposures to a mixture of nanomaterials with unknown health effects. To address this uncertainty, research was conducted to assess the potential pulmonary toxicity of CuCO3 and CeO2 employed in outdoor wood preservation and UV coating. CuCO3 underwent ball-milling to produce samples differing in particle size distribution but overlapped with a commercial CuCO3 product employed in outdoor wood preservation. CeO2 nanoparticles (NPs) were commercially obtained. Saw dust samples (SDS) were obtained from untreated, CuCO3, and CuCO3+CeO2 treated outdoor wood. A thiobarbituric acid reactive substance (TBARS) assay was employed to assess the inherent reactivity of samples. TBARS analysis of ball-milled CuCO3 samples demonstrated that samples with the smallest size distribution displayed the highest reactivity, whereas CeO2 NPs were found to have no TBARS reactivity. CeO2 NPs inhibited the TBARS reactivity of CuCO3 ball-milled samples in a dose-dependent manner. CuCO3 and CuCO3+CeO2 treated outdoor wood SDS displayed TBARS reactivity similar to CuCO3 ball-milled samples. SDS from untreated outdoor wood was negative in the TBARS assay. Centrifuged extracts from CuCO3-treated outdoor wood SDS retained TBARS reactivity but the reactivity was lost when filtered through a 3kDal filter but not a 0.2 µm filter. Human bronchial epithelial BEAS2B cells were exposed to ball-milled CuCO3 samples or CeO2 NPs over a concentration range of 25 – 200 µg/ml for 24 hr and cytotoxicity was assessed using the WST1 assay. CuCO3 ball-milled samples with the smallest size distribution were most cytotoxic to BEAS2B cells at 24 hr post-exposure. CeO2 NPs were not cytotoxic to BEAS2B cells. These findings demonstrate nanoscale CuCO3 particles employed as wood preservatives have inherent reactivity which correlated with human airway epithelial cell cytotoxicity. In addition, results demonstrate the ability of alternative assays to link physicochemical properties to potential adverse pulmonary health effects. (This abstract does not represent EPA policy)

Record Details: