Physico-chemical characterization of metallic nanoparticles derived in welding fumes

Cali Chang, Philip Demokritou, David C. Christiani

Department of Environmental Health, School of Public Health, Harvard University

     Abstract Number: 370
     Last modified: May 10, 2010

Abstract
The main objective of this study is to characterize the physico-chemical properties of metallic nanoparticles generated from the welding fumes during welding processes, and investigate the associations between welding generated nanoparticles and adverse cardiovascular outcome. Due to the unique physico-chemical characteristics of the metallic nanoparticles, we hypothesized that exposure to nanoscaled metal particles may be one of the main reasons that induces cardiovascular responses including effects on heart rate variability and blood pressure.

State of the art particle sampling techniques were deployed for the physico-chemical characterization of the exposures, including both continuous and integrated methods. The following particle continuous measurements were taken every five minutes: 1) total particle number concentration (WCPC, TSI), and; 3) PM2.5 particle mass concentration (DustTrak, TSI). Integrated particle samples were also collected for each sampling day using a PM2.5 sampler (Harvard Impactor) for mass and elemental/organic carbon analysis. In addition, the Harvard Compact Cascade Impactor System (CCI) (Demokritou et al. 2004) was used to fractionate and collect on PUF substrates particles by size ( 2.5, 1.0, 0.5 and 0.1 micro-m sizes). For mass measurements, filters and PUF substrates were equilibrated in a temperature (65-75 degrees F) and relative humidity (40±5%) controlled room both before and after sample collection. Following mass measurements, the HI filters and CCI PUF substrates were analyzed for trace metals using ICP-MS and for elemental and organic carbon by thermal optical reflectance.

Biological samples (urine and blood) of the participated welding workers were collected before and after exposure to evaluate internal exposure by using metabonomic techniques to profile metabolic mechanisms. Real-time HRV was also monitored and recorded using LifeShirtTM (Vivometric). Blood pressure and heart rate was recorded as well.

There was strong evidence that welding procedures result in high fine, ultrafine and nano-range particle concentrations above background. We are analyzing the exposures to test our hypothesis that HRV declines after 8-hour exposure of metal nanoparticles in welding fumes.