Physical chemical properties and cell toxicity of sanding copper-treated lumber

Abstract

To protect against decay and fungal invasion into the wood, the micronized copper, copper carbonate particles, has been applied in the wood treatment in recent years; however, there is little information on the health risk associated with sanding micronized copper-treated lumber. In this study, wood dust from the sanding of micronized copper azole-treated lumber (MCA) was compared to sanding dust from solubilized copper azole-treated wood (CA-C) and untreated yellow pine (UYP). The test found that sanding MCA released a much higher concentration of nanoparticles than sanding CA-C and UYP, and the particles between about 0.4-2 µm from sanding MCA had the highest percentage of copper. The percentage of copper in the airborne dust from sanding CA-C had a weak dependency on particle size and was lower than that from sanding MCA. Nanoparticles were seen in the MCA PM particles, while none were detected in the UYP or CA-C. Inductively coupled plasma mass spectrometry (ICP-MS) analysis found that the bulk lumber for MCA and CA-C had relatively equal copper content; however, the PM particles from sanding the MCA had a higher copper concentration when compared to the PM particles from sanding UYP or CA-C. The cellular toxicity assays show that exposure of RAW 264.7 macrophages (RAW) to MCA and CA-C wood dust suspensions did not induce cellular toxicity even at the concentration of 200 µg PM wood dust/mL. Since the copper from the treated wood dust can leach into the wood dust supernatant, the supernatants of MCA, CA-C and UYP wood dusts were subjected to the cellular toxicity assays. The data showed that at the higher concentrations of copper (≥5 µg/ml), both MCA and CA-C supernatants induced cellular toxicity. This study suggests that sanding MCA-treated lumber releases copper nanoparticles and both the MCA and CA-C-treated lumber can release copper, which are potentially related to the observed in vitro toxicity.

Revealing the structural and chemical properties of copper-based nanoparticles released from copper treated wood

“…The detailed testing procedures and the diagram of the laboratory testing system can be found in recent studies. [20][21][22] In addition, baseline tests were performed when the saw/sander was running but not sawing/sanding any wood to measure the emission from the machines.…”

Understanding Chemical States of Copper Nanoparticles in Wood Structures by Electron Energy Loss Spectroscopy

“…There is a growing concern over the potential exposure of workers to the micronized/nanoscale copper particles released during the handling and mechanical processing of copper-treated lumber. A recent toxicity study indicated that sanding of copper-treated lumber can produce nanoscale copper particles that are potentially cytotoxic [6]. However, the potential toxicity of metal nanoparticles is greatly affected by their chemical states, aspect ratios, and degree of agglomeration.…”