Nanoparticle News recently published a short article about a voluntary NIOSH field study of potential worker exposure to nanoscale materials at a California company late last year. According to the article, the company manufactures nanoscale metals and metal oxides for use in the energy, electronics, and defense industries. Apparently, with NIOSH’s help the company was able to reduce potential workplace emissions of engineered nanoparticles by 90%. Based on final test results, the company "concluded that no further action [was] necessary to reduce engineered nanoscale materials emissions, during the manufacture of nanomaterials, in order to protect the safety of employees and the environment."
The company’s website provides a useful direct link to NIOSH’s October 11, 2007 project report. That report indicates the company uses 4 gas-phase condensation reactors to produce approximately 1 kilogram of nanoparticles per day, and that these manganese, silver, and cobalt nanoparticles range from 15-50 nm in diameter.
NIOSH conducted a baseline assessment in February 2007 and concluded that the company’s reactor clean-out process potentially released these nanoparticles into the workplace, which might cause potential worker exposure. As a result of the baseline study, the company "purchased a portable fume extractor typically used in the welding industry, to control [nanomaterial] releases during reactor clean-out procedures." The fume extractor was a standard 6 inch duct-type attached to a HEPA filtered air-handler with a carbon prefilter. Workers also continued to use existing PPE during the NIOSH study, which consisted of full-body Tyvek™ suits, nitrile gloves, wrist-to-elbow cotton arm covers, and 3M L-122 full-face positive pressure airline respirators.
In July 2007, NIOSH conducted a final site visit and performed a local exhaust ventilation (LEV) effectiveness study. The LEV study used both direct sampling and filter-based sampling methods to "determine the effectiveness of the implemented [LEV] control technology."
NISOH’s filter-based tests showed a percentage reduction in ambient nanoparticles from 74% to 96%, with a mean reduction of 88%. Direct-reading test reductions ranged from 78% to 100%, with a mean reduction of 96%. Transmission electron microscope analysis confirmed a notable increase in nanoparticle capture when the LEV was used, and "[a]ll TEM images, regardless of the use of LEV, indicated that the majority of ENM’s are emitted as agglomerates."
NIOSH concluded its report with a finding that the use of LEV and PPE "appears to be an acceptable method of reducing the potential for worker exposure;" and "[n]o additional protective measures are necessary."
